You should press the mold against the heated bed with the nozzle, then you can create a bigger mold because you dont have to hold the mold by hand you dont have to wait the whole 4 min holding the mold by hand, pressing the mold against the bed will also help with heating the mold so the plastic won’t solidify fast
@@jowmind9277 it would help significantly more with the angle between mold and printhead, as that's always mis-aligned. there has to be a reason he chose not to print on the bed, but I cant think of why.
You need to preheat the mold in in injection molding, what your seeing is the plastic cooling quickly as soon as it touches a mold you are able to touch. Also I can't help thinking that at some point the air pressure building up could become a problem although it didn't look like you were there yet.
Hello from Montreal. So what I noticed is two things. 1- you need an air hole exit to allow the hot filament to make its way instead of possibly building pressure in the mold. 2- Why not lower the gantry to push down on the mold while sitting in the hot plate? Thanks for the video.
Keep in mind actual injection and ISBM machines charge the barrel before injection. That is to say, they melt enough plastic to fill the mold in advance, then inject it all at once.
I don't think that can be done with a 3D printer nozzle (still don't own one), but him using longer and longer nozzles feels like an attempt to approximate that behavior within the spec of 3D printers. It's definitely an important consideration though, and it's what makes me think that part of making this level of hobbyist injection molding accessible will involve people designing DIY/semi 3D printable injectors that let you preheat a load of the plastic and then shoot it in like a syringe.
@@dawserdoos if it is pre-charged, you don't need to melt it at a rate + inject it at a rate, just inject at a rate because the melt has already occurred. I'd imagine more consistent injection.
1. Air vent hole needed at the other side of hole for injection 2. You can inject plastic not at one end of detail, but at the middle - so plastic need just half path for fill all mold. Of couse you need air vent holes at the all end of detail.
Jesus, Stefan not knowing anything about mold design is kind've painful to watch! Air holes are a necessity. Start all over again from the basic 3D printer and it'd probably work with air holes!
@@dmatschekothat can cause really weak parts, more so than layer lines, due to the fact it would have completely cooled and only be warmed by the molten plastic and not the hot end aswell
I'm an injection molding designer. Here are some tips from my point of view: 1. The air vents like everyone said. But this may not be the only cause of failure. Since you have a parting line all around the part. The air can escape through there. 2. The mold needs clamping force so it doesn't flash, BUT the injector machine (in this case the nozzle) MUST HAVE injection pressure, and it's not a small one. We are talking about more than 2 MPa. This is because you need to inject quickly (around 1 to 3 seconds) and the solidifing plastic will give resistance to the filling. 3. In this case in particular, the mold should be heated around 80°C to 100°C temperature so the plastic stays liquid until it gets till the end. If you need some help, please contact me.
@@coledavidson5630Actually, small parts do need a lot of pressure to get all the details filled in before it starts to solidify. I am really curious to see if Stefan can do a revisit and incorporate all the tips he got from you all, I feel that he is close enough to success.
I had the same thought to heat the mold. Add water channels to run hot/warm water through. Or since they are little plastic molds, under a heat lamp before injecting the plastic.
i know nothing about this whole process, but why didn't he have the mold sitting on the bed, where it can stay warm and also perfectly flat? All of his injections have at least some gap because he's never holding it level
Couple of ideas, which come from my experience working for a molding company: Keep the mold hot at around 10 to 20 degrees (celsius) below the melting point of the material. This will give you plenty of time to inject. Make tiny channels at the corners and dead ends of the form to let air escape. This will reduce the needed pressure and it can serve as an indication when the material has filled the mold. You can make the mold outline smaller, reducing the needed resin. Inject from center outwards, not from one end. This will spread the material more uniformly. Best is to make the input port on the larger side of the mold - that way it will be as short and as close as possible, thus reducing the heat loss before filling the form. We are using thin motor oil as releasing agent. Sometimes petroleum jelly. Depends. These are cheaper.
10:50 injection molding operator here. You may need to optimize the mold first, like the placement of the sprue. currently, you have it at the very top of the part meaning it is quickly cooling down causing undershoots. move it more or less in the middle of the parts volume and you will be fine. I'm gonna be doing my tests soon enough as well so I'm gonna check it
Leaving the mould on the bed and lowering the nozzle into the mould may help seal this better than trying to hold the mould to the nozzle at a random height. This will allow you to be less hands on also.
I used to teach injection moulding theory at university and we would print a few moulds and run them with a small injection moulder, like this, as a demonstration. As most people have noted, position of the gate and airs are key. The only thing I would add is that with an injection moulding tool, you actually leave a tiny margin where between the two halves of the mould so that air can escape but plastic cannot. That's why you almost always see a tiny bit of a step along the seam where flashing eventually occurs, if the pressure becomes too great or the mould deteriorates. Hope this helps.
injection mold design engineer here. -First, heating up the mold before injection is crucial, as you noticed yourself. It will delay solidification of the part. -A vent at the end of the part might be a good idea, depends how tight your splitting surfaces are. -You should feed the part into the thickest part, like head of the screw in your last try. You always want the melt to flow from thick to thin since it tends to solidify in the thin part first. -Pressure is not the key actually, speed is more important since melt solidifies with time. Viscosity also tends to decrease with increased speed. Normal injection of a part takes max few seconds. -350bar of pressure is not the lower end in industry. Most of the parts I made molds for were injected with lower pressures. Machines go up to 2000 bar but it's rarely necessary. If part needs that kind of pressures then it's (mostly, not always ;) ) a badly designed part.
Do you know why the printbed was not used to maintain a warm and *most* importantly a level surface for the mold and printhead mating? Was all the tilting he did with the handheld mold to let air out? I would think a flat surface would be best, but there was never an attempted zero tolerance injection
Agree with venting. It is the only way to allow air to escape from those bends or turns in the mold. @10:38 -- add a vent to the "J" part of the hook that didn't fill, creating a vent pipe that will exit to the left side (where your left thumb is in the frame). Otherwise you will face air trapped by the rapidly cooling filament. EDIT: Since you are using the PRUSA bedslinger, I would think you could make a jig that would "lock" the mold on the center of the bed using the two vertical extruded aluminum Z parts as braces. Once the mold is locked into place, You could lower the print head until it makes contact with the sprue. Keep the Z-axis locked into place and then start the extrusion. Having the bed turned on, in contact with the mold, may allow the filament to flow better at the bottom of the mold.
I really hope you revisit this with an air escape hole, the hotend assembly down and pressing onto the mold sitting on the printer bed (potentially heating it) so you don't need to hold it and also a bigger mold. I wonder how far this technique could be pushed!
@arbitrary_username I like Stefans approach to things, even if he isn't an expert in an area, that doesn't mean he can't quickly come up to speed enough to get value. As I think about this, it's highly possible that the air was able to escape via other means like the somewhat poros polymer. I think.if the air was escaping out the cracks, we would have seen some fleshing. Plus he used a release in the mold, which likely would have sealed any porous issues with the resin. To me, I think he was fighting against a building up of pressure. The more polymer that was forced into the mold the more a leading area of pressure was building and fighting his max 300bars. With proper venting and heating those molds, I think for the size parts he was working on, it would have been perfect. Question would be how much bigger could he go with this technique (and the mentioned enhancements) before the leading polymer cooled too much. With real injection molding you have metal molds that are heated to 149*C-426*C and apply anywhere from 500-1500 bars of pressure (some even have air assist for ease of release). Without more pressure, heated molds, and proper vents; his technique will be very limited (though I believe that was his goal any way).
I am one of those who builds injection molding tools and here the recesses on the side are sufficient, especially since the cavity of the finished part has no sharp edges and is not compressed by several tons, and air can also push these tons apart, creating degrees. If this tool were made of steel, I would place the vent closer to the cavity so that the vent has more space more quickly and no holes are created. With a hole at the top as a vent, you only create unnecessary work to remove it because you also have to remove the sprue
I had this idea where you use few generic hotends and extruders to melt filament and inject it into larger heated cylinder, and when it's ready, a piston pushes the plastic to inject it. Because even if you get hold of a hobby grade desktop moulder, you will struggle to buy the pellet material, and if you find it, it will probably be more expensive than filament or you will be required to buy entire euro palet at once.
@@user-it7kg3pm4q Nah they're squeezed together really hard and it's causing a LOT of back pressure to try to evacuate air through the microscopic gap. The precision fit is evidenced by the complete lack of flashing, so it's perfectly liquid-tight and probably very nearly air-tight. Considering he's fighting with insufficient pressure to fill the ends and corners, properly venting the mould can only be a good thing.
On top of that, you can design the mold to fit around the head of the nozzle so that when clamping down it holds pressure in there, thus not allowing material out around it, and increasing pressure inside the mold.
I made an injection molding machine for 3d prints by using an old soldering iron clamped into a metal block. The metal block has a 14mm hole drilled into it. I use an old 14mm bit to push PETG trough a 3 mm end hole into a one time use mold. I use it to make gears because 3d printed ones aren’t tough enough for my applications.
You should consider venting your mold so you aren't building up pressure by compressing air. p.s. You don't need a draft for very short walls, as there is sufficient shrinkage to allow release.
Wow! Your creative idea on 3D printer is amazing and endless. What a smart move to leave some room for everyone here giving their input and gain more engagement, which you tried not to put an air-release-hole to the mold as well as lower the print head to fix the mold in position with down pressure instead of hold by hands. 👍🏻
SUPER!! It honestly surprises me that no one has done a 3D Printer mod kit for something like this yet. It seems like one could rather easily develop fixturing and use bed heater to preheat molds and then custom g-code to move the nozzle to each sprue hole and start shooting molds. Just a matter of time I suppose before we see it. Well done as always Stefan!
A local company has done simular as you. They take all the waste plastic from milk jugs, packaging etc, and then injection mold it into 3d PRINTED(FDM) molds of combs, hair clips, cloths line clips, etc and sell them at local farmers markets. Its really cool
The first application to this that immediately comes to my mind is reusing filament waste (failed prints, calibration prints, purge waste/ams poop, etc). Would love to see some experiments in how to melt and inject those into a mold, considering your past videos on reusing waste for filament extrusion
that would be probably the most sensible use of waste filament. injection molding skips the step of forming it into a filament which must be done with tight tolerances as diameter variability messes up the prints.
Honestly you never cease to impress us this' so cool. I didn't expected to turn out so well since injection molds used a premelted quantity of plastic in one press. I've also seen people preheating the molds in advance to prevent sudden cooling, I wonder if preheating the mold as much as it can would make a difference. In any case good luck this was awesome.
You can easily print shapes like that directly on the plate of the resin printer. No need for putting it at an angle with supports, it just slows the print down, uses more material, requires cleanup, etc. Even dimensional stability is better when printing functional parts directly on the plate, you just have to dial in the elephant foot compensation and properly set the exposure for the first couple of layers.... It was a revelation for me when I started doing it that way...
For solutions to your issue: I believe you were on the right track by heating the mold prior to injection. As for why there are voids in the cavity leading to incomplete parts, I think what is happening is you are compressing the air left in the mold while simultaneously heating the air causing greater pressure than the rapidly cooling plastic can push. The reason why I think this comes from making soft plastic fishing lures. The molds used in the injection method as well as the open pour method have small grooves cut from the end of thin fine detail parts to the mold edge. These fine grooves allow the air out so the plastic can flow into the finer points of the mold. There are plenty UA-cam videos on home made soft plastics to reference. Some lead sinker molds also have thin grooves. I dare to make the comparison as soft plastic lures when at liquid temperature have a similar viscosity to maple syrup. I believe you could easily score your test hook mold with a dremmel cutting wheel from the up turned part to the edge. Less than a mm deep should be good. When or if a hair of the injection plastic comes out of the vent then you know the cavity has been full to the bottom. As for the sucking in of the top after cooling that is from the shrinking of the cooling plastic. It happens in soft plastic injection molding as well. Often a bait maker will top off the sprew so there will be less chance of cavities in the top. As for making molds, I have personally made a 5 cavity minnow open pour mold from elegoo water washable resin to see if it would take the heat of soft plastic and lead. The mold has been used several times for plastic and once for lead so far. It has held up well to the temperature I had plans to make a 2 piece mold like yours this past winter but found myself without the time or energy to 3d model the mold after a long days work. Hopefully I will get the chance later this summer.
Really surprised as an engineer you didnt consider having a vent. Would thought that would be common sense. Without a vent you're just compressing the air inside.
put the clamp ont he print bed, then lower the extruder into the mold and use the Z axis to hold it in place, and the nozzle and print bed can both pre-heat the mold from both sides :D
Very cool idea. I to was 3D printing but wanted a way to make parts faster and stronger which was why I started developing DIY injection molding machines. I think one of issues that you will run into with using a 3D printer is how fast the plastic can be injected before cooling as you have seen. The other issue is that even if you are able to fully fill the part you would want to keep pressure on the part so the plastic has less shrinking and pitting as it cools. That also might be harder to do with an extruder over a plunger or screw type injection molding machine. Preheating the mold is important even on a regular injection molding machine but typically the heat from multiple injections is enough to keep it hot. I also can't remember if I saw vent holes for the air to escape but that is also very important. Last thing you could possible try is to switch the location of where the sprue is injecting the plastic in to the mold. If you did it from a more central location the plastic would have less distance to travel and thus potentially give you better results. Still super cool and can't wait to see what you are able to come up with!
Tested this myself as well. SLA printed mold for a gear and that did work pretty well. I had a hole for the air to get out (and when plastic came out of it I know the mold was full), was using some grease for easier release and I had the mold on the heat bed and I just used the Z-axis to lower nozzle tightly to the mold. Ended up breaking the mold by moving the Z-axis the wrong way...
How about a nozzle that mechanically keys to the mould? And moulds that is designed to be clamped by screw hardware... That way you could put everything in a heated chamber and press until the hotend skips steps.
Suggestions: slather some two part silicone or 500C gasket sealant around the edge of the entrance hole to create a squishy seal around it. That should increase your pressure. Additionally, the exit hole others have mentioned will help a lot. And yeah, pushing the preheat to the limit will help. Home injection molding machines typically require that you bake the mold in the oven before injection to keep the plastic from cooling part way through.
I love this proof of concept; great work. I do think that the best part is the use of a resin printer to make molds. I don't know if you are aware but long before 3d printers were being made by hobbyists, some were making tabletop injection molding machines. Check out the Gingery book on the topic, its a much easier build than a 3D printer in every way except making the molds. So using a 3d printer to make the molds is the real game changer here.
Some advice popped into my mind and I've seen comments writing it but I think these are the main things you need to do in order to succeed: 1. Air vent hole needed at the other side of hole for injection 2. You can inject plastic not at one end of detail, but at the middle - so plastic need just half path for fill all mold. Of couse you need air vent holes at the all end of detail. 3. Preheat the mold to the max limit where it stays solid but preferably around 200 C , so the plastic stays soft during the process, so it won't block the incoming molten plastic.
Nice idea! I was puzzled by what looked like FDM layer lines in the mold, which I thought you said was created on a resin printer (11:42). Also, why did you not have an air pressure relief hole? Perhaps some of the difficulty in filling the mold is due to back pressure.
I feel like every expansive manufacturing techniques has started coming home, 4 axis CNC with the carvers, EDM with the power code and now injection molding
I wouldn't use a 3D printer for injection molding the specialized tools do a way better job for it. But there's DIY and home versions now so it is like you said way more accessible and less expensive.
I use only kitchen equipment and I use my hands. My products are unique, it's not machine manufacturing. I don't find many artisans in this community :(
Dude your math skills are impressive. What you are attempting to do is more like lost wax casting for sculptors who cast parts in metal. You need vents and sprus to let air and trapped gasses out of the mold. In your case you only have trapped air as other commentators have said, If you want to "injection" cast on a larger scale you need to have a hallow center otherwise you will have a solid casting. Starts to get way more complicated here but luckily, the whole concept of 3d printing is to make the outer shape leaving the center hallow. Every project has it's own hurdles to overcome, but you are brilliant, I'm sure you will figure it out.
What an awesome idea! I have a suggestion: Lay the mold on the print bed, and lower the extruder down to the hole, clamping down the two halves with the extruder. Then crank the heat up on the bed, and since it will be touching the bed throughout the entire injection, that will keep the mold hot, and will probably allow the plastic to flow more easily, and longer before the plastic inside cools. It might allow you to do it with less nozzle pressure too.
@@alvarolopez8514 I think the main issue others are pointing out is the lack of a vent hole, which is still necessary, but yeah I think with this and a vent hole, this could be incredibly viable.
there has to be a reason he didn't do this, it's way too obvious. he never addressed it, but keeping the mold flat and warm would've prevented many of his problems to begin with, since he talked a lot about those issues but kept using his mis-angled hand-held injections throughout the whole video. I'm truly baffled and was waiting the for him to inject on the bed, or at the *very* least tell us why he cant.
Hi Stefan. I've been experimenting with this for the past month or so. I've ditched the 3d printer and am currently using a hot glue gun as it pushes more volume faster. Still a WIP but if the community wants to take a toll at it hopefully we can make it happen 🙏
i think the pressure is not the problem - your problem is speed and coolingrate in the mold. you have to melt all the needed volume and then shoot it in. a slow printer extruder might be ok for very small parts. maybe some air vents would help to reduce the airpressure in the mold, the plastic has to "fight" against. some small 0,5mm holes might help a lot.
Hey! I think I have a good idea. You have to make a hole on the end of the part. Pressure could restrict the flow of the plastic. If it would have a hole (I think that's the standard in the industry) it shouldn't take any pressure.
Really cool. Two things of note. (1) You need a second hole to allow air/pressure to escape from. When doing stuff like metal casting using a mold without that second hole you get only partially filled molds. All the 1 hole system is doing is causing air pressure to build up toward the bottom of the mold and that prevents it from filling. Without the hole all their air either gets trapped and won't allow the plastic to fully fill it or it tries to escape, either through the top hole where the plastic enters or by forcing the mold apart. (2) You need to find some way to continuously apply heat to the mold. No matter how hot you have the plastic it means nothing if the mold rapidly cools it and blocks the passage.
you could try heating the mold in a toaster oven and too 150C, you can also change the place where you fill it and widen the sprue to allow more flow. Lastly adding air vents will help prevent air getting trapped. oh and you could make bolt holes to clamp it down they will keep a constant pressure.
Sometimes molds are heated to prevent your issue. Might be your solution for this test. Also allow a purge hole on the other side to remove the pressure from pushing material into it. You need a relief hole for the pressure build up or else it acts like a plunger
two things, like a lot of people have said you need an air hole the air does not get stuck, secondly try preheating the mold a little (you cannot get too hot because they are plastic molds, but heating them up a little will help).
Venting isn't required. You could add an extra chamber to be trimmed off later (often called a material saver, for some odd reason) that the gas could vent into. Remember, any gas inside the mold is being compressed. The seal between the halves will not be perfect enough to prevent gas escape at these low pressures. The suggestions to use the gantry to hold the hot end against the mold and to use the hot bed to maintain mold heat are very good ideas. Now I am wondering about standard 3DP resins......I don't think a glass filled 10k resin would be required for TPU.I've used resin printed molds for epoxy and composites, but hadn't really considered filling them with hot plastic without turning to specific tool resins. Good stuff!
yikes, this makes no sense, "Venting isn't required" but "You could add an extra chamber to be trimmed off later" so venting is required, this is just a worst solution that makes you waste more plastic + you have to refine it, and it's too generalistic aswell, maybe when casting resins you could be better served with an extra chamber due to the low viscosity of the resin, but that's it , in commmercial injection molding using plastic polymers air vents are what is needed, holding the gantry on to the hotbed is indeed a good suggestion tho
@@martimattia1997 Long-winded reply time. Plenty of "material savers" are used in commercial injection molding; that's where I've made my living for most of the past 30 years. Having dealt with injection molding machines varying between 33 and 4000-tons of clamping capacity from automotive to medical, I've been around a little. Adding a vent to atmosphere isn't always feasible, but a material saver can help with filling. Imagine if your problem area with gas-trapping ended up being inside another feature. Having an extra chamber to fill and have the material pass through can help with filling, even if the gas just gets compressed and doesn't vent to atmosphere. Vents go to the outer edge of the mold. That likely isn't required with c-clamp forces and the kinds of speeds and pressures involved here. Also, in commercial injection molding, temps are very high, so the viscosity can be surprisingly low, and there is a lot of speed and pressure moving the plastic. When you get to a point where the surface area of the mold actally counteracts injection forces before the plastic "freezes off", gas pressures can stop flow or cause the clamp to open slightly (the handheld example), and a highly polished mating surface (not part molding surface) can actually be a bad thing. I don't think 3D printing is yet at that level of surface finish. If the mating surfaces of the mold are highly polished AND match perfectly enough, you will get gas trapping and the gases still generally find their way out - not always in the manner expected. The larger issue for small scale molding is temperature control - keeping the mold hot and even cooling it in strategic places.
@@Tech-gu5ge maybe i didn't explain myself well, i'm not sayng that material savers are not useful in any way, i was just pointing out that in this case, was easy enough to vent out really easily and could be a more efficient solution, im not in the industry from that long, so i'm not debating about common molding pratices, you probably have seen way more than me, but from what i saw, airvents are really a common choice
@professorfrog7181 I think heat is going to be the key, retaining heat in the mold and, if possible, adding thermal mass to the column of plastic going in. The addition of mold release to promote surface flow solved a larger issue than venting: it moved the material across the surface quicker, keeping it from freezing off. I think moving to a 3mm extruder would also help keep heat in the material (a molten column behind what was already injected), and likely improve things by moving the plastic faster, even with the same nozzle diameter (higher pressures due to increased piston area) but I would think a larger nozzle would be better by reducing pressure in the extruder and just pushing more plastic into the mold more quickly. Even in industrial injection molding, we tended to do some questionable "experiments".....right down to "squish molding" in wooden molds where you would throw in a blob of molten plastic and squish the 2 halves of the mold together. Heat makes the most difference in material flow. Same with "hot glue molding", using a hot glue gun to try to fill s small mold. Being able to 3D print the molds is a major step forward over the way I did it, and allows for much more detailed molds. Spare time on your hands makes you want to test the "rules" with some hands-on time. I've moved on from injection molding to medical 3D printing; still doing questionable experiments to test the limits.
Like many viewers suggested, 1. you need a venting/exiting hole for air and excessive material. 2. The injecting hole should be on the back of your little figure to maximize the efficiency of the material flow. Plus, I'd suggest you to integrate a BNC port like metal connecting plug into your mold. So that you can lock the mold on the nozzle(by turnning the mold), and let go of your hands while injecting.
Very interesting concept, did you try putting the fill hole on the long side so the filament has less distance to travel? It would also allow active heating on the build plate
As a mecanical engineer who does casting and other moulds i highly recommend to put a small hole at the end so that air can get out of the mould faster. This is used in early every mold for casting or injection moulding
I'm being gaslit! I thought the topic of vents would eventually come up when it was the right time in the script, so I held back the urge to scream "VENTS!" at the screen for 18 minutes, but then the video just ended 😭
Lol the entire time, i was speeding that urge too! In fact, I'm still half through the video before checking the comments to see if anyone else pointed this out! He's a smart guy, so i thought SURELY he'd come to the same solution!
@@Gendo3s2kI think he's a smart guy too, yet here he is trying to injection mold with a freaking 3D printer and printed mold. It's such a ridiculous waste of time. 🤦🏻♂️
I think you need to include a vent channel in the mold's pockets. I think you are "air locking". Basically filling the mold thru the only hole with hot plastic, and pressurizing the air inside the mold until it equalizes with the incoming liquid plastic. Fantastic idea! Please keep working on it.
Blows my mind why you didn't create another hole for air to escape. But more so why you wouldn't just lower the head so you didn't have to force hold the mould up 😂
Hey. Some advice 1. You need exit holes on any chamber you create. A big reasons for injection moulding pressure requirements is the to get over the pressure of the air you're compressing in the mould. Putting pinholes in the mould, at the points the pressure would build up in, will reduce the pressure the printer need to generate. As the pressure increases the more the mould you fill. Pinholes at the deepest recesses of the chamber will create an "outgoing" sprue which you can remove in post 2. Heating the mould, as you know,ows the plastic to remain soft/molten for longer. That's just not doable with a 3D printer alone, let alone a resin printed mould, but it is a fun PoC. If you can't heat the mould, you MUST reduce the pressure inside the mould. That way you can get the hex in the screw 😊
Suggestion, have a screw table to hold the mold up in place or rebuild an 'injection only' device from an old printer using its parts. Make the jaws 'active heat plates' that hold the mold in place with the clamp like you are currently using, and have a small bleed hole to let air out of the print cavity near the extreme portions of the part. Possibly make sacrificial spew to get material to 'far away' portions of the mold. For larger parts, set up to use multiple extruders with multiple ports on the mold to accept hot material. Great project and yet another set of rabbit holes to follow.
Great video! Something I might recommend for you to try out on your hook mold would to be possibly adding a tiny TINY pinhole at the end of where the mold is for air to get out, just something that I'm thinking is that the reason why it's not able to fully flow into it with some of the types of filaments is because the pressure might be getting too high in there and it might not be able to flow all the way. I could be completely wrong about this but it's just something I thought about! Keep up the great work!
Suggestion: Why not use a threaded, hollow bolt as your nozzle and then design complementary threads into one side of your mold. Screw one side of the screw-like nozzle into your hotend and screw the other end into the threads on your mold. This should create a tight seal between the hotend and the mold, preventing leakage. Then clamp your mold together and proceed. In addition to preventing leakage, by using a hollow, threaded bolt, you will also have more diameter to allow for maximum flow into the mol.
Double edged sword, with a wider nozzle you risk the potential for air to get in, which harms the ability to heat it up, as well as the ability to actually extrude it with effective speed
@@thepenguin9 You can make the hole in the threaded bolt as narrow as you wish.... My point is by using a threaded bolt you get a better seal whatever the size of the hole...
Once the plastic creates a semi air seal it makes a pressurized air bubble out of the cavity. It needs an outlet channel at the bottom for air and the injected material to flow through. You would need to clip the tail off once it cools.
Hi Stefan, es ist super wichtig das die Luft aus der Mold entweichen kann, oder du eine kleine Kammer einbaust wo das Material überlaufen kann. Ich habe viele solcher Molds im 3D Druck für meine Arbeit gebaut. Falls du interresse hast können wir uns hier gerne austauchen.
I'm an injection mold designer, I would advise the implementation of vents for off-gassing the cavity in which you are trying to fill, since the gas inside the mold needs somewhere to go, which is also likely an issue you're running into here. As you mentioned, industrial use molds are typically made from tool steel, 41XX AISI series steel, or Stainless, however cutting of these "vents" is usually a very precise and material-application specific process. The channels cut for venting are usually only a couple of thousands of an inch in depth and are done on a surface grinder. However, you could probably do the same thing with a chamfer or heated blade of sorts to "melt" into the mold material (while it is still green?) Anyways hope this helps.
I can't believe I did my senior design project on this last semester, and now you come out with this vid lol. Funny enough, we found that Rigid 10K was the best commercially available resins for this application. Cheers!
I have a couple of suggestions that look like some were covered by other users. 1. Add air vent hole at the end of the mold. 2. To help stop freezing Add heater blocks to the sides of your mold, between the mold and clamp. Ideally brass plates with heater cartridges installed in holes that have been reamed to final size. Use inexspensive industrial DIN framed heater modules and cartridges with built in thermal couples. 3. You could support your mold with the bed or another great idea screw your mold into the hot end in place of a tip. Use bored out threaded rod instead of a tip and have female threads in your mold to screw it onto the threaded rod. You could also just clamshell it on. 4. Fill the high volume parts of your mold first. For the screw fill the hex head first. 5. You may want to avoid nit lines. You could try to move the injection gate location on your hook to be closer to the center of mass.
Hello. I am happy to see you trying these experiments. I am almost convinced that if you would put a relief hole at the opposite end of the part, any one of your extruders would have been able to fill the mold. I believe there’s too much air pressure building up inside the mold, stopping the materials from flowing before they cool down.
Hi Stefan, I'm one of your supporters, and I like your scietific approach. I'm a plastics and composite engineer, and my approach would be a bit different. Since I frequently use silicone moulds (molds), I would recommend the following: Resin print your part as detailed as you want them, silicone would have around 2 microns in molding tolerance. I believe you would be able to produce vinyl records with it (perhaps). Yes, silicone is a flexible material, but if you have a support mold or a mold box in metal, you will be able to add pressure to your mold, and have no deflection. One advantage more with silicone: Some types withstand temperatures up to 450 degree Celcius. 200 degrees can be done with a standard silicone. You can then preheat the mold, and use your 3D printer as injector. When the mold is preheated, you don't need a high backpressure. But it doesn't hurt to have a simple fixture below your moldbox and the printers nozzle. Things can get hot at times ;-) If you experiment with preheating temperature, mold size and perhaps cooling oportunities, as you can cool your moldbox and the silicone inside in different ways. Maybe you can also get some inspiration by watching this guy: www.youtube.com/@TheCrafsMan He makes pressure casting molds in silicone, and cast thermoplastics in them. Thank you for your great work :-)
Molds usually have breather holes to let the air escape. Also, you should inject from the middle, so the plastic doesn't have to travel as far to reach all the corners
I love that your trying things that not many are doing, alot of the comments pointed out what i wanted to say already but as someone who does everything on his own i understand why that flew over your head, but enjoy your videos nonetheless, i dont think it would make a diffrence with bigger molds, but i can see this usefull for smaller parts that can be molded and not accurately 3d printed, like small strong parts that need prescision but also strength in one, cant wait to see more 😊
I did this months ago, but I used an aluminum mold and secondary heater blocks to maintain temperature to keep plastic molten. It worked okay, but ultimately the limitation was maintaining heat. It's just a continuation of the hot-end, but without the high powered heaters and pressure used in injection molding, you're limited on part size.
A few things I’d change: 1) make the mold fill from a center point so it fills from the middle out not the top down. 2) the filling from the middle out makes it so you can lay the larger surface area down on the build plate so that the heated build plate can keep the mold warm and allow for the plastic to cool slower and fill in more 3) move the nozzle manually into the hole in the mold, along with this maybe make the mold so ito holds a rubber or ptfe insert that the nozzle runs into and stretches that it gets a “seal” on the injection part.
Hi, 4 recommendations: 1. Keep the mold hot throughout the injection phase to avoid the injected media solidifying. 2. Start from the largest volume to fill up first (so with the screw start with the head instead o the thread.) 3. Add flow passage channels to help the melted plastic reach the furthest regions in shorter path (small holes only work for heated molds) 4. Add air drain holes to the avoid air pockets
1) injector pushing plastic from bottom to top instead of top to bottom 2) mold is constantly warmed so the plastic injected doesnt cool down and never loses viscosity 3) air holes at the top of the mold and high points in the mold so air doesnt get trapped with vacuum tubes attached sucking out the air and the plastic so air pressure doesnt build up and there's no trapped air. It also helps the melted plastic to move along the crevices
1. Also create 2 heater cartridge cavities and put heater cartridges controlled by a separate heat controller to actively heat the mold. 2. Polish the interior of the mold with a tumbler polisher to improve flow and release. 3. Include exit sprews to vent resistance pressure and allow more plastic than is needed to flow
As a lot of other people mentioned, holes for the air to escape would definitely help. But I also had the thought that a threaded nozzle might help a lot in sealing the injection pressure in the mold!
This was amazing! I'd love to see a strength test between a printed version and a home injection moulded version of the mini hook! Keep up the good work!
Quick comment on the Resin you used: Rigid 10k actually is based on Al2O3 filling - 4K has a glass filling. That's why you get much higher heat deflection temperatures with 10K - because it is kind of a ceramic! Greetings from Germany! Great video and idea!
Great idea and video of it. My suggestions would be to center your fill hole on the mold at the broad side, let the mold preheat on the hot bed, bring the nozzle down to it so that it will apply the required pressure to prevent flashing, run your hot end temp at 200 or more Celsius, and fill. This method should solve all problems because the injection will be evenly distributed, and the mold keeps the required temperature needed to prevent cooling/solidification.
I just wanna say I love the community, the comments are just full of various experts offering really neat advice and ideas and I just find the level of cooperation and helpfulness really cool. Humans are pretty alright sometimes :)
As others have said, you should redesign the mold. Another option, but takes longer is doing a sort of "Lost wax" type casting for the nmold. Print the shape you need, wrap in clay, bake dry the clay and let the plastic or wax melt out or burn up, Then fill the mold with plastic. If built right you should be able to re-use it a few times. Not as much as a metal mold, but good for low production runs. You can also heat the ceramic at that point to keep the plastic hot and flowing. But I think you are onto something. I am excited to see how this concept evolves.
Would be nice to have a custom clamp bed that can hold 10 molds or so and have it hold the nozzle in the mold by itself. I vouch for further R&D and more videos on the topic
Very nice! Has lots of potential. screw the mold directly onto the volcano adapter. put the spout into the middle of the hook so the path is shorter to the end of the mold. move the cavity of the screw-mold much higher to the top funnel.
Great experiment and typical CNCKitchen - thanks, Stephan! Maybe you could add an overflow cavity at the opposite side of the mold, in which you compress the in-mold air and which gets partially filled (like the bottom end of your hook)? Could possibly lower the in-pressure needed. Could also try to put the inflow opening on the side of the mold, so you can clamp the mold with you bed and hot end. And then heat the bed, too.
I still think you’re better off contracting a CNC shop to make the mold for you. Then use just the direct drive on the printer with some kind of press to keep it against the mold. Make your DIY controller with Gcode that just tells it to extrude. Finally you can incorporate into your CNC mold, a few channels for generic heating elements to keep the mold at a very specific temperature.
before even watching the video; I have been thinking about making a "micro" injection molding machine from my old 3d-printer for a while now, so looking forward to see how well it works out :D
I think a small part of your problem with filling the mold also has to do with the fact that you don't have a place for the air to escape as you inject the plastic. I would recommend to try adding a very small vent at the problem areas. There may be more than one on some molds.
It is nice to see you finally realized you needed a release agent but you never added any holes to vent out air or squish out plastic (exit) to make sure you filled your mold fully. On a side note, what about light gardening resin to fill the mold? There will be no real limit to the size it can be and you could add tons of filler and still squirt it out with a paste extruder that will block the frequency of light that hardens the resin.
As others have said, I think your process would benefit from: - Strategically placing the injection point where the molten plastic will have the lowest distance to flow. - Adding a vent hole(s) where air is likely to be trapped - Use the heated bed to pin the mold to the extruder, which will not only keep the mold preheated longer, but the heat will be localized in the area furthest from the injection site, which is beneficial for flow.
Just do a thermoset injection. It’s a cold injection that’s a lot easier to do at home as you don’t need hot plastic. There’s really high grad/high strength thermoset plastics that you can use.
For the M4 screw mold where the head never completely fills, try a couple of well-placed weep holes through which air can escape as the head portion gets filled. The weep holes should be tight, perhaps 1/3 mm, because you want the air to escape the head allowing the head to fill with plastic, and you do not want a lot of plastic escaping through the weep holes. The goal is to fill the head portion and quickly plug the weep holes so that you can build pressure as quickly as possible. You may even experiment with weep holes that don't fully reach the edge and allow air to escape. Maybe the weep holes should have just enough empty volume to contain the air that isn't escaping your current M4 screw mold.
QUESTION: Where could this method be useful?
Check out our Heat Set Inserts and Tools at cnckitchen.store (Free shipping worldwide starting at €100).
You need vent hole at the end of the mold 👎
why could you not set your mold on the printing bed? aligned at 0° on all axis will be a huge improvement from all your angled hand held molds.
You should press the mold against the heated bed with the nozzle, then you can create a bigger mold because you dont have to hold the mold by hand you dont have to wait the whole 4 min holding the mold by hand, pressing the mold against the bed will also help with heating the mold so the plastic won’t solidify fast
@@jowmind9277 it would help significantly more with the angle between mold and printhead, as that's always mis-aligned. there has to be a reason he chose not to print on the bed, but I cant think of why.
You need to preheat the mold in in injection molding, what your seeing is the plastic cooling quickly as soon as it touches a mold you are able to touch. Also I can't help thinking that at some point the air pressure building up could become a problem although it didn't look like you were there yet.
Hello from Montreal. So what I noticed is two things. 1- you need an air hole exit to allow the hot filament to make its way instead of possibly building pressure in the mold. 2- Why not lower the gantry to push down on the mold while sitting in the hot plate? Thanks for the video.
Glad you posted this, I was wondering the same two things!
I was wondering about those exact 2 things
You can make a flat slot for air exhaust, maybe one layer thick, and you probably won't even get any flashing since your pressure is so low.
I'm amazed Stefan didn't figure that out before he started!
Yeah, seeing that Stefan is a really really smart guy, I was surprised that he didn't at least try that out.
Keep in mind actual injection and ISBM machines charge the barrel before injection. That is to say, they melt enough plastic to fill the mold in advance, then inject it all at once.
I don't think that can be done with a 3D printer nozzle (still don't own one), but him using longer and longer nozzles feels like an attempt to approximate that behavior within the spec of 3D printers. It's definitely an important consideration though, and it's what makes me think that part of making this level of hobbyist injection molding accessible will involve people designing DIY/semi 3D printable injectors that let you preheat a load of the plastic and then shoot it in like a syringe.
Interesting! I wonder what the difference is... I'm imagining quite a bit, but have no idea...
@@dawserdoos if it is pre-charged, you don't need to melt it at a rate + inject it at a rate, just inject at a rate because the melt has already occurred. I'd imagine more consistent injection.
Cool
Have you tried adding vents to allow the trapped air to flow out?
1. Air vent hole needed at the other side of hole for injection
2. You can inject plastic not at one end of detail, but at the middle - so plastic need just half path for fill all mold. Of couse you need air vent holes at the all end of detail.
And you could fill some molds first from one side and then from the other. It would have something like a layer line, but only one
Man, that was, what I wanted to write XD
I was also surprised not to see vent holes
Jesus, Stefan not knowing anything about mold design is kind've painful to watch! Air holes are a necessity. Start all over again from the basic 3D printer and it'd probably work with air holes!
@@dmatschekothat can cause really weak parts, more so than layer lines, due to the fact it would have completely cooled and only be warmed by the molten plastic and not the hot end aswell
I hope you make a part 2. The comments are full of great wisdom and I can't wait to see how this develops
Please do!
I didn’t come across a bunch of wisdom, so much as I merely came across basic fundamental elements of plastic injection molding.
I'm an injection molding designer. Here are some tips from my point of view:
1. The air vents like everyone said. But this may not be the only cause of failure.
Since you have a parting line all around the part. The air can escape through there.
2. The mold needs clamping force so it doesn't flash, BUT the injector machine (in this case the nozzle) MUST HAVE injection pressure, and it's not a small one. We are talking about more than 2 MPa.
This is because you need to inject quickly (around 1 to 3 seconds) and the solidifing plastic will give resistance to the filling.
3. In this case in particular, the mold should be heated around 80°C to 100°C temperature so the plastic stays liquid until it gets till the end.
If you need some help, please contact me.
I can't imagine you'd need that much pressure for these tiny mold volumes. There's gotta be a workaround
@@coledavidson5630 yes the workaround for low pressure is same as poured casting, a vent hole or more as required
@@coledavidson5630Actually, small parts do need a lot of pressure to get all the details filled in before it starts to solidify.
I am really curious to see if Stefan can do a revisit and incorporate all the tips he got from you all, I feel that he is close enough to success.
I had the same thought to heat the mold. Add water channels to run hot/warm water through. Or since they are little plastic molds, under a heat lamp before injecting the plastic.
i know nothing about this whole process, but why didn't he have the mold sitting on the bed, where it can stay warm and also perfectly flat? All of his injections have at least some gap because he's never holding it level
Couple of ideas, which come from my experience working for a molding company:
Keep the mold hot at around 10 to 20 degrees (celsius) below the melting point of the material. This will give you plenty of time to inject.
Make tiny channels at the corners and dead ends of the form to let air escape. This will reduce the needed pressure and it can serve as
an indication when the material has filled the mold.
You can make the mold outline smaller, reducing the needed resin.
Inject from center outwards, not from one end. This will spread the material more uniformly. Best is to make the input port on the larger side of the mold - that way it will be as short and as close as possible, thus reducing the heat loss before filling the form.
We are using thin motor oil as releasing agent. Sometimes petroleum jelly. Depends. These are cheaper.
10:50 injection molding operator here. You may need to optimize the mold first, like the placement of the sprue. currently, you have it at the very top of the part meaning it is quickly cooling down causing undershoots. move it more or less in the middle of the parts volume and you will be fine. I'm gonna be doing my tests soon enough as well so I'm gonna check it
Yes I was thinking the same thing!
Letting the mold sit on the bed and heating it may also help to keep a nice flow temp?
I think also finding a way to get a good seal would help. Maybe the mold could have space to encapsulate the nozzle tip?
Leaving the mould on the bed and lowering the nozzle into the mould may help seal this better than trying to hold the mould to the nozzle at a random height. This will allow you to be less hands on also.
Good suggestion KleikPL. He also needs to vent his part.
I used to teach injection moulding theory at university and we would print a few moulds and run them with a small injection moulder, like this, as a demonstration. As most people have noted, position of the gate and airs are key. The only thing I would add is that with an injection moulding tool, you actually leave a tiny margin where between the two halves of the mould so that air can escape but plastic cannot. That's why you almost always see a tiny bit of a step along the seam where flashing eventually occurs, if the pressure becomes too great or the mould deteriorates. Hope this helps.
injection mold design engineer here.
-First, heating up the mold before injection is crucial, as you noticed yourself. It will delay solidification of the part.
-A vent at the end of the part might be a good idea, depends how tight your splitting surfaces are.
-You should feed the part into the thickest part, like head of the screw in your last try. You always want the melt to flow from thick to thin since it tends to solidify in the thin part first.
-Pressure is not the key actually, speed is more important since melt solidifies with time. Viscosity also tends to decrease with increased speed. Normal injection of a part takes max few seconds.
-350bar of pressure is not the lower end in industry. Most of the parts I made molds for were injected with lower pressures. Machines go up to 2000 bar but it's rarely necessary. If part needs that kind of pressures then it's (mostly, not always ;) ) a badly designed part.
Do you know why the printbed was not used to maintain a warm and *most* importantly a level surface for the mold and printhead mating?
Was all the tilting he did with the handheld mold to let air out? I would think a flat surface would be best, but there was never an attempted zero tolerance injection
Agree with venting. It is the only way to allow air to escape from those bends or turns in the mold. @10:38 -- add a vent to the "J" part of the hook that didn't fill, creating a vent pipe that will exit to the left side (where your left thumb is in the frame). Otherwise you will face air trapped by the rapidly cooling filament.
EDIT: Since you are using the PRUSA bedslinger, I would think you could make a jig that would "lock" the mold on the center of the bed using the two vertical extruded aluminum Z parts as braces. Once the mold is locked into place, You could lower the print head until it makes contact with the sprue. Keep the Z-axis locked into place and then start the extrusion. Having the bed turned on, in contact with the mold, may allow the filament to flow better at the bottom of the mold.
That last point is good to hear, that the crazy high pressures aren't typically needed gives me a lot more hope for this being possible
or very high density resins, like HIPS
Wow, what a ton of responses and suggestions; I believe everyone would appreciate a follow-up video on the same subject.
Thanks Stefan.
I really hope you revisit this with an air escape hole, the hotend assembly down and pressing onto the mold sitting on the printer bed (potentially heating it) so you don't need to hold it and also a bigger mold. I wonder how far this technique could be pushed!
Yeah the holding it in place really took me aback when it's in the context of a machine that can press down an exact amount by itself
I think you are trapping air in the molds and that is why you need so much pressure.
Stefan, I believe you forgot a small vent hole towards the end of the mold (to let air escape) that and achieving higher temp in the mold
I feel a little bit relieved seeing someone so competent making multiple stupid mistakes... like I often do myself.
@arbitrary_username I like Stefans approach to things, even if he isn't an expert in an area, that doesn't mean he can't quickly come up to speed enough to get value.
As I think about this, it's highly possible that the air was able to escape via other means like the somewhat poros polymer. I think.if the air was escaping out the cracks, we would have seen some fleshing. Plus he used a release in the mold, which likely would have sealed any porous issues with the resin.
To me, I think he was fighting against a building up of pressure. The more polymer that was forced into the mold the more a leading area of pressure was building and fighting his max 300bars.
With proper venting and heating those molds, I think for the size parts he was working on, it would have been perfect.
Question would be how much bigger could he go with this technique (and the mentioned enhancements) before the leading polymer cooled too much.
With real injection molding you have metal molds that are heated to 149*C-426*C and apply anywhere from 500-1500 bars of pressure (some even have air assist for ease of release).
Without more pressure, heated molds, and proper vents; his technique will be very limited (though I believe that was his goal any way).
I am one of those who builds injection molding tools and here the recesses on the side are sufficient, especially since the cavity of the finished part has no sharp edges and is not compressed by several tons, and air can also push these tons apart, creating degrees. If this tool were made of steel, I would place the vent closer to the cavity so that the vent has more space more quickly and no holes are created. With a hole at the top as a vent, you only create unnecessary work to remove it because you also have to remove the sprue
King the same thing
I had this idea where you use few generic hotends and extruders to melt filament and inject it into larger heated cylinder, and when it's ready, a piston pushes the plastic to inject it.
Because even if you get hold of a hobby grade desktop moulder, you will struggle to buy the pellet material, and if you find it, it will probably be more expensive than filament or you will be required to buy entire euro palet at once.
You need a hole on the top on the mold to get trapped air out
And also lubricate the mold to avoid the plastic to stick too much
@@user-it7kg3pm4q Nah they're squeezed together really hard and it's causing a LOT of back pressure to try to evacuate air through the microscopic gap. The precision fit is evidenced by the complete lack of flashing, so it's perfectly liquid-tight and probably very nearly air-tight. Considering he's fighting with insufficient pressure to fill the ends and corners, properly venting the mould can only be a good thing.
@@user-it7kg3pm4q I would assume that the slightly flexble resin-halfs, if get pressed together with enough force, seal up very tight.
On top of that, you can design the mold to fit around the head of the nozzle so that when clamping down it holds pressure in there, thus not allowing material out around it, and increasing pressure inside the mold.
Or pull a vacuum on it
I made an injection molding machine for 3d prints by using an old soldering iron clamped into a metal block.
The metal block has a 14mm hole drilled into it. I use an old 14mm bit to push PETG trough a 3 mm end hole into a one time use mold.
I use it to make gears because 3d printed ones aren’t tough enough for my applications.
You should consider venting your mold so you aren't building up pressure by compressing air.
p.s. You don't need a draft for very short walls, as there is sufficient shrinkage to allow release.
Wow! Your creative idea on 3D printer is amazing and endless. What a smart move to leave some room for everyone here giving their input and gain more engagement, which you tried not to put an air-release-hole to the mold as well as lower the print head to fix the mold in position with down pressure instead of hold by hands. 👍🏻
SUPER!! It honestly surprises me that no one has done a 3D Printer mod kit for something like this yet. It seems like one could rather easily develop fixturing and use bed heater to preheat molds and then custom g-code to move the nozzle to each sprue hole and start shooting molds. Just a matter of time I suppose before we see it.
Well done as always Stefan!
A local company has done simular as you. They take all the waste plastic from milk jugs, packaging etc, and then injection mold it into 3d PRINTED(FDM) molds of combs, hair clips, cloths line clips, etc and sell them at local farmers markets. Its really cool
Molds are expensive. Ask them. I do farmers markets, I'll be bankrupt if I use injection molding molds.
@@matildo4ka7 they 3d print there molds so its not expensive.
Yeah I always enjoy watching their videos. Their channel is called BrothersMake (pretty sure I got that right)
The first application to this that immediately comes to my mind is reusing filament waste (failed prints, calibration prints, purge waste/ams poop, etc). Would love to see some experiments in how to melt and inject those into a mold, considering your past videos on reusing waste for filament extrusion
that would be probably the most sensible use of waste filament.
injection molding skips the step of forming it into a filament which must be done with tight tolerances as diameter variability messes up the prints.
Thats what we do at my university. We create Filaments and recycle print waste!
Honestly you never cease to impress us this' so cool. I didn't expected to turn out so well since injection molds used a premelted quantity of plastic in one press. I've also seen people preheating the molds in advance to prevent sudden cooling, I wonder if preheating the mold as much as it can would make a difference. In any case good luck this was awesome.
You can easily print shapes like that directly on the plate of the resin printer. No need for putting it at an angle with supports, it just slows the print down, uses more material, requires cleanup, etc. Even dimensional stability is better when printing functional parts directly on the plate, you just have to dial in the elephant foot compensation and properly set the exposure for the first couple of layers.... It was a revelation for me when I started doing it that way...
For solutions to your issue: I believe you were on the right track by heating the mold prior to injection. As for why there are voids in the cavity leading to incomplete parts, I think what is happening is you are compressing the air left in the mold while simultaneously heating the air causing greater pressure than the rapidly cooling plastic can push.
The reason why I think this comes from making soft plastic fishing lures. The molds used in the injection method as well as the open pour method have small grooves cut from the end of thin fine detail parts to the mold edge. These fine grooves allow the air out so the plastic can flow into the finer points of the mold. There are plenty UA-cam videos on home made soft plastics to reference. Some lead sinker molds also have thin grooves. I dare to make the comparison as soft plastic lures when at liquid temperature have a similar viscosity to maple syrup. I believe you could easily score your test hook mold with a dremmel cutting wheel from the up turned part to the edge. Less than a mm deep should be good. When or if a hair of the injection plastic comes out of the vent then you know the cavity has been full to the bottom.
As for the sucking in of the top after cooling that is from the shrinking of the cooling plastic. It happens in soft plastic injection molding as well. Often a bait maker will top off the sprew so there will be less chance of cavities in the top.
As for making molds, I have personally made a 5 cavity minnow open pour mold from elegoo water washable resin to see if it would take the heat of soft plastic and lead. The mold has been used several times for plastic and once for lead so far. It has held up well to the temperature I had plans to make a 2 piece mold like yours this past winter but found myself without the time or energy to 3d model the mold after a long days work. Hopefully I will get the chance later this summer.
Really surprised as an engineer you didnt consider having a vent. Would thought that would be common sense. Without a vent you're just compressing the air inside.
I love this. We need to continue the desktop injection mold technology. Stephon is doing it 💪🏾💪🏾💪🏾
put the clamp ont he print bed, then lower the extruder into the mold and use the Z axis to hold it in place, and the nozzle and print bed can both pre-heat the mold from both sides :D
Very cool idea. I to was 3D printing but wanted a way to make parts faster and stronger which was why I started developing DIY injection molding machines. I think one of issues that you will run into with using a 3D printer is how fast the plastic can be injected before cooling as you have seen. The other issue is that even if you are able to fully fill the part you would want to keep pressure on the part so the plastic has less shrinking and pitting as it cools. That also might be harder to do with an extruder over a plunger or screw type injection molding machine. Preheating the mold is important even on a regular injection molding machine but typically the heat from multiple injections is enough to keep it hot. I also can't remember if I saw vent holes for the air to escape but that is also very important. Last thing you could possible try is to switch the location of where the sprue is injecting the plastic in to the mold. If you did it from a more central location the plastic would have less distance to travel and thus potentially give you better results. Still super cool and can't wait to see what you are able to come up with!
Tested this myself as well. SLA printed mold for a gear and that did work pretty well.
I had a hole for the air to get out (and when plastic came out of it I know the mold was full), was using some grease for easier release and I had the mold on the heat bed and I just used the Z-axis to lower nozzle tightly to the mold.
Ended up breaking the mold by moving the Z-axis the wrong way...
Good to hear!
1) make a small hole a opposite side of pouring hole to escape the air
2) make a metallic mold & preheat the mold before pouring the PLA
How about a nozzle that mechanically keys to the mould? And moulds that is designed to be clamped by screw hardware... That way you could put everything in a heated chamber and press until the hotend skips steps.
Suggestions: slather some two part silicone or 500C gasket sealant around the edge of the entrance hole to create a squishy seal around it. That should increase your pressure.
Additionally, the exit hole others have mentioned will help a lot.
And yeah, pushing the preheat to the limit will help. Home injection molding machines typically require that you bake the mold in the oven before injection to keep the plastic from cooling part way through.
The guy who will shill for anyone for a dollar has an opinion.
I love this proof of concept; great work. I do think that the best part is the use of a resin printer to make molds. I don't know if you are aware but long before 3d printers were being made by hobbyists, some were making tabletop injection molding machines. Check out the Gingery book on the topic, its a much easier build than a 3D printer in every way except making the molds. So using a 3d printer to make the molds is the real game changer here.
Some advice popped into my mind and I've seen comments writing it but I think these are the main things you need to do in order to succeed:
1. Air vent hole needed at the other side of hole for injection
2. You can inject plastic not at one end of detail, but at the middle - so plastic need just half path for fill all mold. Of couse you need air vent holes at the all end of detail.
3. Preheat the mold to the max limit where it stays solid but preferably around 200 C , so the plastic stays soft during the process, so it won't block the incoming molten plastic.
the fact that you can resin print a mold now is enough for me to get a small injection molding extruder tbh!
Nice idea! I was puzzled by what looked like FDM layer lines in the mold, which I thought you said was created on a resin printer (11:42). Also, why did you not have an air pressure relief hole? Perhaps some of the difficulty in filling the mold is due to back pressure.
I feel like every expansive manufacturing techniques has started coming home, 4 axis CNC with the carvers, EDM with the power code and now injection molding
I wouldn't use a 3D printer for injection molding the specialized tools do a way better job for it. But there's DIY and home versions now so it is like you said way more accessible and less expensive.
I use only kitchen equipment and I use my hands. My products are unique, it's not machine manufacturing. I don't find many artisans in this community :(
Dude your math skills are impressive. What you are attempting to do is more like lost wax casting for sculptors who cast parts in metal. You need vents and sprus to let air and trapped gasses out of the mold. In your case you only have trapped air as other commentators have said, If you want to "injection" cast on a larger scale you need to have a hallow center otherwise you will have a solid casting. Starts to get way more complicated here but luckily, the whole concept of 3d printing is to make the outer shape leaving the center hallow. Every project has it's own hurdles to overcome, but you are brilliant, I'm sure you will figure it out.
What an awesome idea! I have a suggestion: Lay the mold on the print bed, and lower the extruder down to the hole, clamping down the two halves with the extruder. Then crank the heat up on the bed, and since it will be touching the bed throughout the entire injection, that will keep the mold hot, and will probably allow the plastic to flow more easily, and longer before the plastic inside cools. It might allow you to do it with less nozzle pressure too.
That might be a really good idea. It should helo solve all the problems that people are pointing out in a very simple way. 👏🏻👏🏻👏🏻
@@alvarolopez8514 I think the main issue others are pointing out is the lack of a vent hole, which is still necessary, but yeah I think with this and a vent hole, this could be incredibly viable.
there has to be a reason he didn't do this, it's way too obvious. he never addressed it, but keeping the mold flat and warm would've prevented many of his problems to begin with, since he talked a lot about those issues but kept using his mis-angled hand-held injections throughout the whole video. I'm truly baffled and was waiting the for him to inject on the bed, or at the *very* least tell us why he cant.
@@nadca2There was no reason he didn't do it other than he didn't know or forgot. Just like the vent hole
Hi Stefan. I've been experimenting with this for the past month or so. I've ditched the 3d printer and am currently using a hot glue gun as it pushes more volume faster. Still a WIP but if the community wants to take a toll at it hopefully we can make it happen 🙏
i think the pressure is not the problem - your problem is speed and coolingrate in the mold.
you have to melt all the needed volume and then shoot it in.
a slow printer extruder might be ok for very small parts.
maybe some air vents would help to reduce the airpressure in the mold, the plastic has to "fight" against. some small 0,5mm holes might help a lot.
Hey! I think I have a good idea. You have to make a hole on the end of the part. Pressure could restrict the flow of the plastic. If it would have a hole (I think that's the standard in the industry) it shouldn't take any pressure.
Okay so, from what I’m seeing in the comments, he MIGHT have forgotten a vent hole. However, only a few people have said it so I’m not sure…
Haha, yeah only a very small number of people have mentioned it.
Maybe we should also tell him?
Yeah I'm not sure, it's up in the air. Maybe another 30 comments would convince me
I think you might be into something
I wonder if a vent hole would have helped
I was exactly thinking about this then I saw your comment. He definitely needs a vent hole.
Really cool. Two things of note.
(1) You need a second hole to allow air/pressure to escape from. When doing stuff like metal casting using a mold without that second hole you get only partially filled molds. All the 1 hole system is doing is causing air pressure to build up toward the bottom of the mold and that prevents it from filling. Without the hole all their air either gets trapped and won't allow the plastic to fully fill it or it tries to escape, either through the top hole where the plastic enters or by forcing the mold apart.
(2) You need to find some way to continuously apply heat to the mold. No matter how hot you have the plastic it means nothing if the mold rapidly cools it and blocks the passage.
you could try heating the mold in a toaster oven and too 150C, you can also change the place where you fill it and widen the sprue to allow more flow. Lastly adding air vents will help prevent air getting trapped. oh and you could make bolt holes to clamp it down they will keep a constant pressure.
Sometimes molds are heated to prevent your issue. Might be your solution for this test.
Also allow a purge hole on the other side to remove the pressure from pushing material into it. You need a relief hole for the pressure build up or else it acts like a plunger
Why no air escape channels? The trapped air pushes plastic out of the mold.
Two channels are needed at least, its simple logic and I dont know why Stefan didnt use this.
This was my first instinct as well
Well, I'd imagine that with the tolerance of a 3D printed mold air escapage would be fine.
@@captainironbat8193 Nah, that resin part was printed really freaking smooth and clamped down hard
two things, like a lot of people have said you need an air hole the air does not get stuck, secondly try preheating the mold a little (you cannot get too hot because they are plastic molds, but heating them up a little will help).
Venting isn't required. You could add an extra chamber to be trimmed off later (often called a material saver, for some odd reason) that the gas could vent into. Remember, any gas inside the mold is being compressed. The seal between the halves will not be perfect enough to prevent gas escape at these low pressures. The suggestions to use the gantry to hold the hot end against the mold and to use the hot bed to maintain mold heat are very good ideas. Now I am wondering about standard 3DP resins......I don't think a glass filled 10k resin would be required for TPU.I've used resin printed molds for epoxy and composites, but hadn't really considered filling them with hot plastic without turning to specific tool resins. Good stuff!
yikes, this makes no sense, "Venting isn't required" but "You could add an extra chamber to be trimmed off later" so venting is required, this is just a worst solution that makes you waste more plastic + you have to refine it, and it's too generalistic aswell, maybe when casting resins you could be better served with an extra chamber due to the low viscosity of the resin, but that's it , in commmercial injection molding using plastic polymers air vents are what is needed, holding the gantry on to the hotbed is indeed a good suggestion tho
@@martimattia1997 Long-winded reply time. Plenty of "material savers" are used in commercial injection molding; that's where I've made my living for most of the past 30 years. Having dealt with injection molding machines varying between 33 and 4000-tons of clamping capacity from automotive to medical, I've been around a little.
Adding a vent to atmosphere isn't always feasible, but a material saver can help with filling. Imagine if your problem area with gas-trapping ended up being inside another feature. Having an extra chamber to fill and have the material pass through can help with filling, even if the gas just gets compressed and doesn't vent to atmosphere. Vents go to the outer edge of the mold. That likely isn't required with c-clamp forces and the kinds of speeds and pressures involved here. Also, in commercial injection molding, temps are very high, so the viscosity can be surprisingly low, and there is a lot of speed and pressure moving the plastic.
When you get to a point where the surface area of the mold actally counteracts injection forces before the plastic "freezes off", gas pressures can stop flow or cause the clamp to open slightly (the handheld example), and a highly polished mating surface (not part molding surface) can actually be a bad thing. I don't think 3D printing is yet at that level of surface finish. If the mating surfaces of the mold are highly polished AND match perfectly enough, you will get gas trapping and the gases still generally find their way out - not always in the manner expected.
The larger issue for small scale molding is temperature control - keeping the mold hot and even cooling it in strategic places.
@@Tech-gu5ge maybe i didn't explain myself well, i'm not sayng that material savers are not useful in any way, i was just pointing out that in this case, was easy enough to vent out really easily and could be a more efficient solution, im not in the industry from that long, so i'm not debating about common molding pratices, you probably have seen way more than me, but from what i saw, airvents are really a common choice
@professorfrog7181 I think heat is going to be the key, retaining heat in the mold and, if possible, adding thermal mass to the column of plastic going in. The addition of mold release to promote surface flow solved a larger issue than venting: it moved the material across the surface quicker, keeping it from freezing off. I think moving to a 3mm extruder would also help keep heat in the material (a molten column behind what was already injected), and likely improve things by moving the plastic faster, even with the same nozzle diameter (higher pressures due to increased piston area) but I would think a larger nozzle would be better by reducing pressure in the extruder and just pushing more plastic into the mold more quickly.
Even in industrial injection molding, we tended to do some questionable "experiments".....right down to "squish molding" in wooden molds where you would throw in a blob of molten plastic and squish the 2 halves of the mold together. Heat makes the most difference in material flow. Same with "hot glue molding", using a hot glue gun to try to fill s small mold. Being able to 3D print the molds is a major step forward over the way I did it, and allows for much more detailed molds. Spare time on your hands makes you want to test the "rules" with some hands-on time. I've moved on from injection molding to medical 3D printing; still doing questionable experiments to test the limits.
Worked a lot better than i expected, this gives hope that for smaller parts a much smaller and cheaper machine than the huge usual DIY ones could work
I think you need a clamp with heating elements inside to keep the mold warm. That, and you really need airducts. It will flow way better that way.
I agree. In addition to the air vents, heating the mold would facilitate the flow of the material.
Like many viewers suggested,
1. you need a venting/exiting hole for air and excessive material.
2. The injecting hole should be on the back of your little figure to maximize the efficiency of the material flow.
Plus, I'd suggest you to integrate a BNC port like metal connecting plug into your mold. So that you can lock the mold on the nozzle(by turnning the mold), and let go of your hands while injecting.
Very interesting concept, did you try putting the fill hole on the long side so the filament has less distance to travel? It would also allow active heating on the build plate
As a mecanical engineer who does casting and other moulds i highly recommend to put a small hole at the end so that air can get out of the mould faster. This is used in early every mold for casting or injection moulding
I'm being gaslit! I thought the topic of vents would eventually come up when it was the right time in the script, so I held back the urge to scream "VENTS!" at the screen for 18 minutes, but then the video just ended 😭
Lol the entire time, i was speeding that urge too! In fact, I'm still half through the video before checking the comments to see if anyone else pointed this out!
He's a smart guy, so i thought SURELY he'd come to the same solution!
@@Gendo3s2kI think he's a smart guy too, yet here he is trying to injection mold with a freaking 3D printer and printed mold. It's such a ridiculous waste of time. 🤦🏻♂️
@@Studio23Mediait is a step in brainstorming. It may be a waist of time, but may lead to other, better ideas
Look up the meaning of gaslighting
I think you need to include a vent channel in the mold's pockets. I think you are "air locking". Basically filling the mold thru the only hole with hot plastic, and pressurizing the air inside the mold until it equalizes with the incoming liquid plastic.
Fantastic idea! Please keep working on it.
Blows my mind why you didn't create another hole for air to escape. But more so why you wouldn't just lower the head so you didn't have to force hold the mould up 😂
Yes, an escape channel would help. Also heating the mold would help. And embedding the nozzle into the mold, so that the mold screws into the hotend.
Hey. Some advice
1. You need exit holes on any chamber you create. A big reasons for injection moulding pressure requirements is the to get over the pressure of the air you're compressing in the mould. Putting pinholes in the mould, at the points the pressure would build up in, will reduce the pressure the printer need to generate. As the pressure increases the more the mould you fill. Pinholes at the deepest recesses of the chamber will create an "outgoing" sprue which you can remove in post
2. Heating the mould, as you know,ows the plastic to remain soft/molten for longer. That's just not doable with a 3D printer alone, let alone a resin printed mould, but it is a fun PoC. If you can't heat the mould, you MUST reduce the pressure inside the mould. That way you can get the hex in the screw 😊
7:25 where is a channel to relase the air?
Suggestion, have a screw table to hold the mold up in place or rebuild an 'injection only' device from an old printer using its parts. Make the jaws 'active heat plates' that hold the mold in place with the clamp like you are currently using, and have a small bleed hole to let air out of the print cavity near the extreme portions of the part. Possibly make sacrificial spew to get material to 'far away' portions of the mold. For larger parts, set up to use multiple extruders with multiple ports on the mold to accept hot material. Great project and yet another set of rabbit holes to follow.
You should have homed the printer then use the clamping force between the nozzle and the bed to get a better seal on the nozzle.
Great video!
Something I might recommend for you to try out on your hook mold would to be possibly adding a tiny TINY pinhole at the end of where the mold is for air to get out, just something that I'm thinking is that the reason why it's not able to fully flow into it with some of the types of filaments is because the pressure might be getting too high in there and it might not be able to flow all the way.
I could be completely wrong about this but it's just something I thought about! Keep up the great work!
Suggestion:
Why not use a threaded, hollow bolt as your nozzle and then design complementary threads into one side of your mold. Screw one side of the screw-like nozzle into your hotend and screw the other end into the threads on your mold. This should create a tight seal between the hotend and the mold, preventing leakage. Then clamp your mold together and proceed.
In addition to preventing leakage, by using a hollow, threaded bolt, you will also have more diameter to allow for maximum flow into the mol.
Double edged sword, with a wider nozzle you risk the potential for air to get in, which harms the ability to heat it up, as well as the ability to actually extrude it with effective speed
@@thepenguin9 You can make the hole in the threaded bolt as narrow as you wish.... My point is by using a threaded bolt you get a better seal whatever the size of the hole...
Once the plastic creates a semi air seal it makes a pressurized air bubble out of the cavity. It needs an outlet channel at the bottom for air and the injected material to flow through. You would need to clip the tail off once it cools.
Hi Stefan, es ist super wichtig das die Luft aus der Mold entweichen kann, oder du eine kleine Kammer einbaust wo das Material überlaufen kann. Ich habe viele solcher Molds im 3D Druck für meine Arbeit gebaut. Falls du interresse hast können wir uns hier gerne austauchen.
I'm an injection mold designer, I would advise the implementation of vents for off-gassing the cavity in which you are trying to fill, since the gas inside the mold needs somewhere to go, which is also likely an issue you're running into here. As you mentioned, industrial use molds are typically made from tool steel, 41XX AISI series steel, or Stainless, however cutting of these "vents" is usually a very precise and material-application specific process. The channels cut for venting are usually only a couple of thousands of an inch in depth and are done on a surface grinder. However, you could probably do the same thing with a chamfer or heated blade of sorts to "melt" into the mold material (while it is still green?) Anyways hope this helps.
Did you really think the air inside the mould would just magically vanish?
I can't believe I did my senior design project on this last semester, and now you come out with this vid lol. Funny enough, we found that Rigid 10K was the best commercially available resins for this application. Cheers!
Wow, I found this on my recommended 8 seconds after it was posted.
4 mins here, must be a supercomsumer 😂
Same
15 mins for me, but I'd been out for a cigarette for 20 🤣
I have a couple of suggestions that look like some were covered by other users.
1. Add air vent hole at the end of the mold.
2. To help stop freezing Add heater blocks to the sides of your mold, between the mold and clamp. Ideally brass plates with heater cartridges installed in holes that have been reamed to final size. Use inexspensive industrial DIN framed heater modules and cartridges with built in thermal couples.
3. You could support your mold with the bed or another great idea screw your mold into the hot end in place of a tip. Use bored out threaded rod instead of a tip and have female threads in your mold to screw it onto the threaded rod.
You could also just clamshell it on.
4. Fill the high volume parts of your mold first. For the screw fill the hex head first.
5. You may want to avoid nit lines. You could try to move the injection gate location on your hook to be closer to the center of mass.
Y dont you jut fill a transparent mold with resin and cure it
Hello. I am happy to see you trying these experiments. I am almost convinced that if you would put a relief hole at the opposite end of the part, any one of your extruders would have been able to fill the mold. I believe there’s too much air pressure building up inside the mold, stopping the materials from flowing before they cool down.
Someone forgot the basic physics
Если ты про то что он сжимает воздух, я был поражен его стараниям! Но с первых же секунд, задал вопрос в пространство, где отвод воздуха?
@@hoseignasio1538 Да. Но можете ли вы использовать английский? Я не понимаю по-русски.
Hi Stefan, I'm one of your supporters, and I like your scietific approach. I'm a plastics and composite engineer, and my approach would be a bit different. Since I frequently use silicone moulds (molds), I would recommend the following: Resin print your part as detailed as you want them, silicone would have around 2 microns in molding tolerance. I believe you would be able to produce vinyl records with it (perhaps). Yes, silicone is a flexible material, but if you have a support mold or a mold box in metal, you will be able to add pressure to your mold, and have no deflection. One advantage more with silicone: Some types withstand temperatures up to 450 degree Celcius. 200 degrees can be done with a standard silicone. You can then preheat the mold, and use your 3D printer as injector. When the mold is preheated, you don't need a high backpressure. But it doesn't hurt to have a simple fixture below your moldbox and the printers nozzle. Things can get hot at times ;-) If you experiment with preheating temperature, mold size and perhaps cooling oportunities, as you can cool your moldbox and the silicone inside in different ways. Maybe you can also get some inspiration by watching this guy: www.youtube.com/@TheCrafsMan He makes pressure casting molds in silicone, and cast thermoplastics in them. Thank you for your great work :-)
Molds usually have breather holes to let the air escape. Also, you should inject from the middle, so the plastic doesn't have to travel as far to reach all the corners
I love that your trying things that not many are doing, alot of the comments pointed out what i wanted to say already but as someone who does everything on his own i understand why that flew over your head, but enjoy your videos nonetheless, i dont think it would make a diffrence with bigger molds, but i can see this usefull for smaller parts that can be molded and not accurately 3d printed, like small strong parts that need prescision but also strength in one, cant wait to see more 😊
I did this months ago, but I used an aluminum mold and secondary heater blocks to maintain temperature to keep plastic molten. It worked okay, but ultimately the limitation was maintaining heat. It's just a continuation of the hot-end, but without the high powered heaters and pressure used in injection molding, you're limited on part size.
A few things I’d change:
1) make the mold fill from a center point so it fills from the middle out not the top down.
2) the filling from the middle out makes it so you can lay the larger surface area down on the build plate so that the heated build plate can keep the mold warm and allow for the plastic to cool slower and fill in more
3) move the nozzle manually into the hole in the mold, along with this maybe make the mold so ito holds a rubber or ptfe insert that the nozzle runs into and stretches that it gets a “seal” on the injection part.
Hi, 4 recommendations:
1. Keep the mold hot throughout the injection phase to avoid the injected media solidifying.
2. Start from the largest volume to fill up first (so with the screw start with the head instead o the thread.)
3. Add flow passage channels to help the melted plastic reach the furthest regions in shorter path (small holes only work for heated molds)
4. Add air drain holes to the avoid air pockets
1) injector pushing plastic from bottom to top instead of top to bottom
2) mold is constantly warmed so the plastic injected doesnt cool down and never loses viscosity
3) air holes at the top of the mold and high points in the mold so air doesnt get trapped with vacuum tubes attached sucking out the air and the plastic so air pressure doesnt build up and there's no trapped air. It also helps the melted plastic to move along the crevices
1. Also create 2 heater cartridge cavities and put heater cartridges controlled by a separate heat controller to actively heat the mold.
2. Polish the interior of the mold with a tumbler polisher to improve flow and release.
3. Include exit sprews to vent resistance pressure and allow more plastic than is needed to flow
As a lot of other people mentioned, holes for the air to escape would definitely help.
But I also had the thought that a threaded nozzle might help a lot in sealing the injection pressure in the mold!
This was amazing!
I'd love to see a strength test between a printed version and a home injection moulded version of the mini hook!
Keep up the good work!
Quick comment on the Resin you used: Rigid 10k actually is based on Al2O3 filling - 4K has a glass filling. That's why you get much higher heat deflection temperatures with 10K - because it is kind of a ceramic!
Greetings from Germany! Great video and idea!
Interesting because the datasheet clearly says "This highly glass-filled resin...". Gotta dig a little deeper.
Great idea and video of it. My suggestions would be to center your fill hole on the mold at the broad side, let the mold preheat on the hot bed, bring the nozzle down to it so that it will apply the required pressure to prevent flashing, run your hot end temp at 200 or more Celsius, and fill. This method should solve all problems because the injection will be evenly distributed, and the mold keeps the required temperature needed to prevent cooling/solidification.
I just wanna say I love the community, the comments are just full of various experts offering really neat advice and ideas and I just find the level of cooperation and helpfulness really cool. Humans are pretty alright sometimes :)
As others have said, you should redesign the mold.
Another option, but takes longer is doing a sort of "Lost wax" type casting for the nmold. Print the shape you need, wrap in clay, bake dry the clay and let the plastic or wax melt out or burn up, Then fill the mold with plastic. If built right you should be able to re-use it a few times. Not as much as a metal mold, but good for low production runs. You can also heat the ceramic at that point to keep the plastic hot and flowing.
But I think you are onto something. I am excited to see how this concept evolves.
Would be nice to have a custom clamp bed that can hold 10 molds or so and have it hold the nozzle in the mold by itself. I vouch for further R&D and more videos on the topic
Very nice! Has lots of potential.
screw the mold directly onto the volcano adapter.
put the spout into the middle of the hook so the path is shorter to the end of the mold.
move the cavity of the screw-mold much higher to the top funnel.
Great experiment and typical CNCKitchen - thanks, Stephan!
Maybe you could add an overflow cavity at the opposite side of the mold, in which you compress the in-mold air and which gets partially filled (like the bottom end of your hook)? Could possibly lower the in-pressure needed.
Could also try to put the inflow opening on the side of the mold, so you can clamp the mold with you bed and hot end. And then heat the bed, too.
I still think you’re better off contracting a CNC shop to make the mold for you. Then use just the direct drive on the printer with some kind of press to keep it against the mold. Make your DIY controller with Gcode that just tells it to extrude. Finally you can incorporate into your CNC mold, a few channels for generic heating elements to keep the mold at a very specific temperature.
Agreed, I work with molds at my job and all of them need venting some times in multiple places inorder for the mold to fill completely.
before even watching the video; I have been thinking about making a "micro" injection molding machine from my old 3d-printer for a while now, so looking forward to see how well it works out :D
I think a small part of your problem with filling the mold also has to do with the fact that you don't have a place for the air to escape as you inject the plastic. I would recommend to try adding a very small vent at the problem areas. There may be more than one on some molds.
I wrote prusa about this exactly about six months ago. Never heard back. Glad to see you tried it out!
It is nice to see you finally realized you needed a release agent but you never added any holes to vent out air or squish out plastic (exit) to make sure you filled your mold fully.
On a side note, what about light gardening resin to fill the mold? There will be no real limit to the size it can be and you could add tons of filler and still squirt it out with a paste extruder that will block the frequency of light that hardens the resin.
The air hole could be a gap in the mold fit. It could result in a brim like material that should be easy to remove.
As others have said, I think your process would benefit from:
- Strategically placing the injection point where the molten plastic will have the lowest distance to flow.
- Adding a vent hole(s) where air is likely to be trapped
- Use the heated bed to pin the mold to the extruder, which will not only keep the mold preheated longer, but the heat will be localized
in the area furthest from the injection site, which is beneficial for flow.
Just do a thermoset injection. It’s a cold injection that’s a lot easier to do at home as you don’t need hot plastic. There’s really high grad/high strength thermoset plastics that you can use.
For the M4 screw mold where the head never completely fills, try a couple of well-placed weep holes through which air can escape as the head portion gets filled. The weep holes should be tight, perhaps 1/3 mm, because you want the air to escape the head allowing the head to fill with plastic, and you do not want a lot of plastic escaping through the weep holes. The goal is to fill the head portion and quickly plug the weep holes so that you can build pressure as quickly as possible. You may even experiment with weep holes that don't fully reach the edge and allow air to escape. Maybe the weep holes should have just enough empty volume to contain the air that isn't escaping your current M4 screw mold.