Building a CNC Mill/Router - Part 2
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- Опубліковано 28 вер 2024
- Filling my new CNC mill/router with sand and epoxy resin to create epoxy granite, which will increase it's weight and vibration damping!
CNC Part 1: • Building a CNC Mill/Ro...
Old CNC router video: • My CNC Router... FINALLY
As a piano tech, I'd say you did a great job eliminating the frequencies that cause the most trouble. In pianos, that is.
Now he probably can reach all the gcode notes.
Haha, good point this would be an amazing piano now :D
You know, fiddling with settings might actually eliminate any leftover problem frequencies!
Maybe there are some sensors you can use to determine resonances, and software to compensate for it? If not, here's a great video idea :D
@@purvel : There are companies out there specialising in eliminating resonance in machinery... witchcraft?
Next up, how to build an aluminium CNC piano
I recommend to fill the legs with fine loose sand. It absorbs vibration much better
i think its gonna be hard to remove the epoxy sand mix
@@Supmah2007 the legs are still hollow.
Yea the whole point of using sand to dampen sound is that it converts vibrations into heat through friction, when you "stabilize" the sand with resin and remove the friction aspect, just creates a new medium for sound to travel through
Did you ram the sand down or just let is fall down?
@@TheRattleSnake3145 You want it loose
Your epoxy granite will have its own resonant frequency, because it is stiff. I think the whole point of the sand is that its lose and will move about and not resonate. Now you've just got 2 different materials with 2 different resonant frequencies, coupled together. Hopefully they overlap and still help a bit.
This is exactly the problem. You want sand as it has no resonance at all and is a great damper over basically all frequencies of interest. Also, sand fills the voids well but his cement will shrink a little as it sets and you lose the intimate sand to metal contact. All he has done is change the resonance by adding mass but has likely not introduced appreciable damping. I appreciate however that he has holes in the system and the sand would work it's way out eventually.
@@rob66181 Added mass of different resonant frequencies is almost guaranteed to dampen vibrations.
Epoxy granite wont resonate it behaves like a piece of stone
@@wizrom3046 Yes it does, most solid objects do. If you hang a rod of stone or concrete from a string, and tap it, it will ding. Thats it resonating.
@@ratgreen actually it doesnt. The epoxy is much less dense than the stone particles so the whole thing absorbs energy and is very low resonance.
Those custom-fit sand funnels are incredibly satisfying
Doesn't the fact sand moves help absorb vibrations? But won't the epoxy keep it from moving?
hard to say - the increased density of the epoxy + sand will dampen the vibration amplitude and frequency of resonance
on the other hand sand without epoxy could dissipate energy via friction
overall I would say increased density has a greater effect
While I never build a CNC or anything that needed to have low ringing/high vibration resilience.
My instinct would also be to use something that can move on its own and is only slightly coupled. Like Rubber or silicon.
But then again, every build I have seen so far uses resin and sand/gravel.
But all the other builds have their CNC standing on the ground or a very strong table. So I guess the feed are the biggest "problem".
Yeah the fact that the epoxy prevents dissipative losses means the sand is just ballast
Both affect the vibrations in this dynamic system. The increased mass increases the inertial force and the sand increases the damping effect since it is not perfectly bound by the epoxy (both of which increase resistance to motion).
i agree with you, to me thats one reason sound travels much longer distance in water then air
It's generally considered best practice to mix the epoxy parts before you mix it with a filler. That way you can be assured of good mixing.
It doesn’t sound the same at all! Sounds much better!
Well done! I did exactly the same on a custom build that I currently assemble.
Your problem is indeed the stand. The CNC should be heavy on the bottom and get lighter the higher you go. You have a very rigid machine now, on a flimsy undercariage. You will see how shaky it will become, once the machine is up and running and you do some highly dynamic stuff with repetitive direction changes, like boring or adaptive clearing. Maybe you have some possibility to attach the legs to the adjacent walls with some wooden spacers. This should fix it.
But in any case, it is a great build 👍
Good job! I think you'll find it helps a lot more than you think. Resonance or vibration is only part due to stiffness (lack of...), you also need to consider the accelerated mass. Doubling the tightly coupled mass of a beam lowers the resonance frequency, sure - but the important part is that the beam impact load moment of inertia goes up to a factor of mass increase squared. Doubling the mass means that the same impact force now gives four times lower beam displacement. This helps a lot on all vibrations and momentary impacts that are NOT perfectly synced to the resonance frequency. At (the now lower) resonance, the same amount of impact force has the same displacement as before though
You just described drum tuning in the most scientific way possible.
Excellent overview of the benefits related to increasing mass. It is my understanding that the stiffness of the overall system increases. I think he could have increased mass further if the mix was compacted in layers. The mixture didn't seem fluid enough to settle with just a few taps.
The objective is to remove chatter:
Eliminating "ringing" created by tool cutting edges contacting the workpiece at a harmonic of the frames natural frequency is one reason to fill the extrusions.
Another reason is to increase the overall mass of the machine... this alone can be a significant improvement.
I guess that's why you don't see many portable Bridgeport mills! 😜
Really looking forward to the rest of the series; I don't think you are going to be disappointed with the finished machine.
Great video Tom! Getting rid of all that vibration is indeed very important 👍
cannot wait for part 3.... the structure is sturdy :)
What a fitting video! Just yesterday I decided to fill the column of my milling machine to reduce vibration and increase weight. I used a product called "Durfill" by Durcrete which is a cement glue based engineering concrete for filling structures and building machine bases. It expands slightly when curing to fill gaps and self levels. It's less of a mess than dealing with epoxy resin.
You mean durafill?
@@NiclasGudmundsson no, I used Durfill from Durcrete, a German manufacturer of ultra high performance concrete.
@@Sven_Hein ahh thanks, I will have a look to see if I can find that here in sweden too. I'm having thoughts to make a concrete bottom part for my machine so I can have a built in coolant system.
Where is part 3? I check back every week 😂
Would loose sand dampen vibration better than the weight of the epoxy granite?
imo increased density due to epoxy added has a greater effect than friction within loose sand.
You're all going to give Tom a complex and his next video will be testing like 30 different materials for frequency and stiffness.
The mass of the sand probably has more of an effect on damping than the loose sand itself. Additionally, loose sand would end up finding ways to get out and would make a mess.
@@yetanotherdan This reminds me of the whole marble machine madness for those that know.
@@ChrisValin-w6o not enough mass
Hi Tim. I've been considering epoxy granite for my CNC build, however I strongly believe that the Sikaflex 290DC deck caulking that we use at work for cruise liner Teak decking will be a good alternative choice. My reasoning is down to how these dampening materials work; converting vibration into heat through friction. Epoxy granite alters and shifts the resonant frequencies within the system to longer wavelengths which are less intrusive than the higher "ringing" plain Aluminium produces. Sound dampening materials in audio applications tend to use dense flexible materials such as rubber or polyurethanes which are very good at converting vibration to heat. Sikaflex polyurethane caulks are single component and much more convenient than mixing up dry aggregates and epoxy, which is an attractive benefit.
If I recall, New Yorkshire Workshop's CNC build featured concrete, so you're going in the right direction!
That was a great build !
yea, i´m also waiting for part 3 ...
Your videos are like asmr for engineers ❤
I'd bolt the entire thing to the ground or a concrete block, with rubber gasket between aluminium and concrete.
I'd also put lightly coupled (or gasketed) bracing between the middle of legs and the uprights, reducing the number of long lengths that can resonate.
Here is what’s happening: filling the cores increased the mass and lower the resonant frequency. But to dampen the vibrations, you need to dissipate that energy somehow and for that, you need loose sand. I think you’ll be fine, but you could try filling the legs with loose sand and compare them to see how it changes. I did this awhile back with some speakers stands I have. I filled one with some very dry, fine Masons sand and compared the sound by swapping stands with one that wasn’t filled. I didn’t expect any difference, but it really sounded significantly better. So, I don’t know if it would make a difference in machining quality but it does make a difference. If nothing else, maybe it will help to make it quieter when operating. You should also try to use some strips of sound dampening mat, like they use for car audio. You don’t need much, just a strip on each extrusion. Just be sure to put it where you’ll never need to remove it because it really sticks.
I have done the same thing with my welded machine, but I compacted in the epoxy sand mix as I filled it and that made a noticeable difference.
One tube I had to fill sideways and could not compact, which resulted in a noticeably less uniformly and densely damped tube (you could hear the difference when you hit it at different positions).
the sand-epoxy dough looks edible enough, wonder how that taste like
gritty
cockles on a cold wet stoney brit beach
Looks like kinetic sand one had as a child
It tastes like eating chips at the beach on a windy day
Probably tastes like cancer
No rush but we need a part threeeeee!! I can’t wait I wanna copy this design a bit.
It seems like you’re going in a great direction with it
Use dry sand on the the vertical legs. its pretty much self compacting and should pour in like water if the sand it totally dry. iv had bags of kipn dried that were not dry before hahah
Currently working on a cnc build as well with an extrusion based table/enclosure. To cut down on vibrations and to make the table much stiffer im attaching mdf panels to the sides of the table. Also contemplating using some rubber like gasketing or some sort of putty between the mdf and extrusion.
Regardless, stoked to see where this goes! Oh and also something worth checking out is services like jlcpcb, pcbway (pretty sure they do sponsorships) and rapid direct. If you have any weird brackets or mounts you wanna make, you can just shoot them some cad and some money and you'll get back freshly machined pieces.
One other idea, where you have linear rails, you could just get a slab of mic-6 and mount your linear rails to that. Mic-6 is usually pretty darn flat and not too expensive.
Anywho looking forward to the rest of your build!
I would think that Constraint Layer Dampening would work really well for damping the internal vibrations, easiest and most affordable way to do that would be the sound deadening used in cars.
You'd want to get the stuff that has a goey viscoelastic layer on one side and a thick foil layer on the other side. It's incredible how effective it is at damping sound and ringing in solids.
I have no idea if anyone has done that with a CNC machine but it should work!
Also I would have left the sand dry and only added resin to the ends so it can't escape, seems like if you make the sand a solid structure then it's reduced its dampening effect and it's only lowering the resonant frequency, and hasn't increased the decay rate
Good luck!
I would suggest to further stiffen the lower structure (that can't be filled with sand), for example by simply introducing more cross beams or diagonal beams. This should greatly reduce vibrations in the system.
Perhaps you can try adding the material they use in deadening vibration in high end car sound systems. I think they sell that stuff in rolls and you might be able to attach it to the underside of your build-plate or other convenient areas.
Don't be disappointed Tom.
Any added mass will help dampen frequencies in the range of your cutter speed rpm. Rubber or metalastic feet will also help.
I think you should try it and see......fine tune the clearance on your axis guides.
Loving the content.
Maybe try to Wrap a Rubber mat or Rubber Tape around the legs? The Rubber could absorb the virbrations and also isolate the Sound or reduce the frequency. I guess even normal Tape would Help notacibly.
Listening to the internet... My cnc machine stand same issue, used some gell blocks and some sound deadening foam/foil stick on stuff and job done. cost me 40 quid and took ten mins to do
You could add custom-designed tuned mass dampers to the outside of the legs if it turns out that you need to, that would make for another interesting video in its own right.
You can fill the smaller areas of extrusions by loading the epoxy granite into refillable caulking cartridges and pressure/squeezing it into the extrusion. If you want more rigidity, you can use steel rebar implanted into the epoxy granite.
Maybe diagonal steelwire or braces between the legs. It seems like you now have more weight on spaghetti legs. And I dont know what type of machine feet you have but stiff dampers could also maybe help further.
There is always tradeoffs when designing such a machine. Take your gantry axis for example. You can use very low rails to increase rigidity but then often loose out on drive-stiffness by needing coupling over to the leadscrew (like you have). Alternative is using taller guiderails where the leadscrew can fit under and the coupling nut carrier can then interface directly with the axis for a stiffer drive position. In the end I do not know which is more rigid but I went for the second option on my machine based on simulations in the CAD.
Print spacers in TPU to put between the 8080 extrusions and the legs to help blocking the resonance
Do you really need to rigidly mount the frame to the feet? Maybe adding some rubber to the mounting-points could dampen the vibrations traveling from the main frame into the base/legs.
Maybe inserting rubber/elastic "cushins" between the bed and the legs could help isolating them from each other? Of course that means another cumbersome disassembly and reassembly... But if you still decide to do it, don't forget the screws connecting the two halves together would also need some mini-cushins!
Props for the £1 B&Q Orange Bucket!
Try steel or lead shot plus loose dried sand in the base. This should give you an acoustically dead stand, and make the tool bottom heavy. Right now you are top heavy and that will amplify any vibrations. You may also want to replace the uprights with square 80x80s. They will be easier to fill and give you a bit more contact area and stability at the corners.
Lastly, you may want to use additional angle braces or plates to increase the rigidity of your extrusion joints
Mate, the idea of using sand it’s that stays loose (dat absorb vibration better)
I made my farrier anvil stand and filled whit loose sand, that work perfectly
Its the principal on “dead blow hammers”
The sound definitely dissipates quicker now, you could even measure the damping by looking at the sound wave
I'm thinking bolting it down after might make a big difference too. Either to the floor, or to a concrete block if you don't want to make holes in the floor.
I've been thinking about building a cnc with these extrusions too and I was thinking about filling them with some kind of damping material. Like greenglue or some liquid rubber type stuff that sets and becomes solid material that actually damps the vibrations rather than just adding mass
Tim, good job, I am keenly capturedin your videos about this as I only just finished my CNC mill (I wish I had a CNC to build the frame mounting parts as that would have eliminated my inaccuracies in making the fixtures and it would not have taken 6 years). You will definitely see an improvement in cut quality with your improvements, but making some chips will be the biggest tell. From the video it looks like rigidity from the grooves/T slot fixtures maybe your weakest point causing flex on the gantry and you may need to increase the gantry mounting strength with a drilled & bolted hole through Y axis mounting + to support this the gantry feet & fixturing could be bulked up. Love the videos.
Read up on input shaping. It is being used on 3D printers to avoid resonant frequencies.
Sound proofing material felt washers The main issue is hollow pieces but they are metal on metal which can transfer sound / vibration
Most builders fail to use rubber isolating pads for the feet of home-built machine tools. These pads help to reduce vibration.
Maybe adding strips of heavy rubber to the outside of the legs would dampen the vibration. Something like horse stall mats cut into strips and bolted to the extrusion?
maybe add between leg and main frame?
Appropriate Barry Mounts would be my first choice.
Just an idea to add to the masses, but a lot of machining tools have cast iron bases to absorb vibrations. I would think mounting the CNC on one of those plates would help with the vibrations in the legs, hope this helps!
Flexible TPU washers between the legs and base.
What you could do for the legs is use motor mix . It is much thinner than concrete but not as thin as straight epoxy so it would would flow into the legs much easer. But wouldn't flow out as long as you had end caps on the bottom. if you are worried about them ringing.
You could have used iron filings or small ball bearings? If you Made an iron filing/ epoxy slurry you could have poured in like the sand. If doing the ball bearings you could drop in then pour the standard epoxy.
With bearings you could possibly cap ends and pour in the bearing. That way you can recover and use again.
Alternative solution for hollow sound is to use expanding foam to fill voids and damp the sound a little.
80x80 extrusion on the gantry at 45°. Large 10mm or so triangular plates bolted on from the sides to further improve the rigidity of the gantry. I think some sand blasting media is more dense, especially if you mix different grain sizes. It can be packed more densely by tamping with a rod.
Perhaps the ringing is coming from the contact between the heads of the fasteners and the inner surface of the t slot of the mating beam. I suggest testing various durometer rubber washers under the heads of the fasteners to dial in the perfect damping. (not "dampening" if you're going to use this in a video)
Pretty sure a lot of resonance would be removed by bolting a sheet of MDF or similar to one of the sides of the base, since MDF is elastic it's a great vibration sink.
The mass of the sand definitely will lower the frequencies involved.
you could 3D-print some T-slot sand buckets which can be moved around to show.
A small mass damper system could be made in a similar way, but getting it tuned in might be a pain.
Cross brace the legs and weigh them down or bolt them down to make it super rigid. And cross brace the gantry to the table. It will be solid and overbuilt.
And I am excited to see you indicate everything in square and parallel
the ringing is not so bad, resonance is what you have to watch out for, and adjust you rpm's for.
Drill holes in the legs and cross beams and fill with straight epoxy. Gonna be TOP HEAVY and Wiggle.
Should have filled them B4 reassembly... Cool Project to learn from. thank you
The stuff in the middle of the beams is not as stiff as the aluminum, and it's close to the neutral axis. It isn't moving much, so to do much vibration damping it would need to really efficiently damp any motion that did get to it. The loss tangent should be high at relevant frequencies. Maybe RTV would've been a better binder than epoxy for this application. Something soft and goopy, bare minimum to hold in the sand--it wouldn't be load-bearing no matter what you did, so might as well maximize dissipation.
In epoxy granite, the composite is load bearing and moreover in the good stuff the load paths are through the aggregate to such a high degree that its mechanical properties are more rock-like. That's hard to do. You need several aggregate sizes and powerful vibration to consolidate it.
And the ideal amount of binder.
what about spray foam in the legs to deaden them?
I'm surprised you didn't use something to compact the sand. It doesn't seem like it "flows" very well. There are probably small voids lowering the density.
How about filling the legs with lead shot?
Suppose that's why the older stationary machines were casted instead of bolting lightweight stuff together.
Filling the machine with just sand when is was put together might have worked well with just those caps.
Tilt, fill, closd and repeat
working with high end CNC machines myself, from manufacturers such as DMG Mori and Mazak, you will find that rigidity comes with mass, as well as how that mass is suspended. High end machines have huge iron castings which weigh literal tons, then the machine is levelled with specialist kit and it gets bolted to the concrete floor. The floor becomes part of the machines mass. If you didnt bolt the machine to the floor, vibrations would cause it to move over time, and your parts will be inconsistent, have poor finishes and just generally would not be good for the machine. Its the same sort of idea when youre machining hard metals such as inconel, monel, a lot of types of steel, titanium etc. if you have the material on a fixture high above the machines table with little support under the fixture, you get too much vibrations which will cause excessive too wear/damage, poor surface finish and so on, hence why when you machine these marteials, its best to try and make it one with the machine (bolt direct to table)
anyway rant over haha, what i would do if you could is make the legs as solid as possible, and bolt them to the floor. the difference will be huge. Many people end up welding something out of steel box section or I-beam extrusion, however if you dont have the resources for welding you could us large bolts (lots of them) and it will work well still
You should have made endcaps and left the sand without the epoxy. The loose sand can absorb the vibrations because they can move while the granite will act as a single piece with a single resonance. Think about a dead mallet. It is filled with loose sand.
I don't think adding weight to the bottom of the base will help that much, since the main problem, it looks like, it the frame itself flexing (very slightly, which is what the vibrations are). Like others have suggested, I'd definitely say finding a way to fill the legs would be a massive improvement. Whether that means changing the legs to be the square tubes so they're easier to fill, filling them with loose sand rather than the epoxy mixture so that it's easier to fill, or something else. I work in custom automation, and for machines with something like an ultrasonic welds on it, which exerts tons of pressure (literally) and vibrates in the range of kHz, so frame rigidity is very important, I would think it would be a strange design choice if one of our designers made a big stout gantry and mounted it on less stout legs.
If you want to eliminate the vibrations fill the table legs with a sand silicon mixture
Add plywood wall panels around the aluminum frame, will remove all of those vibrations and significantly further stiffen the structure.
It could definitely do with bracing. I would experiment bracing with rubber pads sandwiched between the members and the braces
While the way you mixed the epoxy was a great idea, I wonder if it would have been easier (and maybe cheaper) to fill the legs with bonded sand like Petrobond or even Kinetic Sand. There are also a few different kinds of casting sand (Sodium silicate sand) that can be poured easily and then cured to a "hardened state" with the addition of CO2.
As for the legs, I think it is less about the weight and more about the long, hollow surfaces that allow for vibration. May want to look at car-deadening mats (like Dynamat) and paints (like Spectrum's Liquid Sound Deadner) that could be added to help lessen resonance.
I think the sand is not meant to add mass (which would just decrease the resonance frequecies) but to dampen the vibrations, and for that it needs to be able to dissipate energy i.e have lots of grains rubbing on one another, but the epoxy could be preventing that from happening. I don't build cncs and the sand epoxy thing might be common but if there's a problem I see it here
adding mass was a good thing anyway.
To isolate the table have you put thought about adding a tpu/rubber gasket where the legs meet the table?
you should also defenetly lube the bearings with lube recommended by the manufacturer, they usually come unlubed and just have a film of oil to protect them!, you have to clean off this oil and then lube them yourself
All the rigidity is in the base and gantry, right? Why don’t you use some sort of vibration isolator between the base and the stand? Maybe a high density rubber mat? This could help with accoustics.
Ive filled the upper cavities in mine with molten lead, I haven't rebuilt it yet so nothing to report at the moment. It's defo a lot heavier though.
Make a wall brace and bolt it to a wall =D helped a lot with mine
I would have thought that you would want the sand to be able to move in order to absorb vibration most effectively.
Blasting garnet is MUCH denser than beach sand. I think the filler material should be loose rather than bound for best vibration suppression. It is important to have good coupling from beam to filler.
If you are not too committed. Moving the ball screw between or below the guide rails will help eliminate racking of the tool head. Your current design has cutting forces being resisted by the highly leveraged ball screw, encouraging racking..
How about some rubber washers/spacer between the sand filled table and hollow frame?
it is very easy to weight the machine; just put it on 4 (or 2) scales and add it together.
so, you skipped your CNC machine's leg day?
You could try with adding some self-adhesive sound deadening that is used in cars.
Where is the vibration coming from? Which part of the extrusion? If it’s the little parts that stick out that you bolt everything onto, that tightening will decrease vibrations.
Might be that rubber sealing between legs and top would minimise ring effect 🤔
Better idea is to use sand mixed with old oil. Then you have shock absorber inside your extrusions.
you could truss the legs with braided cable
expanding foam instead of sand would also reduce noise / vibration & be cheaper & faster. Good idea or bad ?
Btw is it possible to add some dampening material on top of the legs?
I bet your CNC skills would allow to work around attachment method
Following! :) Your videos are always top quality. I'm going to make a CNC lathe with filled welded tubes (80x80x5mm steel) but i'm thinking about using pure dry sand due to the huge epoxy cost. I'm wondering if there's much difference between dry sand vs epoxy-glued sand.
The base needs to be solid. You could have filled the whole frame with Epoxy Concrete using a mix with more epoxy. It flows well even in fairly small gaps.
The sand-epoxy just acts as an inertial damper or ballast. I've seen other methods that use thick, used oil made even more viscous by mixing it with fine, sandblasting media. This might have better dissipation.
Would an exo skeleton of heavy hardwood help? Usually good resonance damping is achieved when dissimilar materials are bonded together.
By epoxying the sand you took away the physical property that makes it dampening in the first place...
Sand moving under vibration is what dissipates the energy.
You didn't remove any ringing, you just added mass and so lowered its frequency.
5:51 your hearing the metal hammer ring. Try a wood mallet instead. Its probably ringing a lot less than you think.
If all you really care about is the "ringing"... for noise levels... or resonate frequencies... I'd say you could fill the legs with simple cotton balls or some kind of fiberous insulation. People who build skateboard ramps always glue sleeping bags or blankets to the underside of the skateboard ramps so that when the skaters ride on the ramps, the sound is "dead" and not like riding a skateboard inside an acoustic guitar.
I wonder which CNC controller you'll use.
You lowered the resonant frequency which should make it worse. Job done! Squares are inherently structurally wobbly, not a big problem with your contact area on most of that build but the vertical members are thin. Try cross bracing to stiffen it up the vertical walls. Either two cables under tension on both diagonals or a single rigid diagonal.
I'd experiment with rubber pads sandwiched between the brace and members