HDPE Distortion As It Cools
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- Опубліковано 13 жов 2024
- HDPE is a great material for amateur recycling, but it can be difficult to work with in some ways - This video details a couple of experiments to show how HDPE can seriously distort as it cools from softened state back to rigid material
For more information:
The Atomic Shrimp HDPE Playlist: • HDPE
How I ground up the HDPE source material: • Grinding HDPE for recy...
More on how and why I'm using a sandwich toaster: • How To Recycle HDPE Pl...
Making something useful - a plastic pulley: • Making A Pulley Wheel ...
So well presented and so clear. Excellent instructions. Thank you!
Thank you for sharing your experiment. It's a treat to have you work out the variables.
Hi, thanks for your comment on my last posting. I recently had an unexplained experience with melting HDPE to make a block. I melted HDPE bottles in my oven in a square oven proof dish. To speed up the process I lined a George Foreman grill with baking paper and made melted sheets which I added to the dish in the oven. They would be about 15 mm thick. The Baking paper ripped on the last sheet and I noticed that the hot HDPE did not stick to the teflon coating of the grill at all, so I discarded the baking paper and squeezed the hdpe nice and flat before adding it to the dish in the oven. This is where the puzzlement begins. When I introduced the new melted hdpe to the already melted hdpe in the oven, it was like sticking wax onto ice, the two sheets slid over each other without sticking. I put a weight on it and let it cool in the oven. When it was cold the two sheets came apart, it did not join at all. I can use the two sheets as they are, but I cannot recycle any of it as I do not know if the teflon came of in micro amounts, or fat from previous cooking contaminated it. I wipe the grill with hot soapy water after every use. On a different note - I found a brilliant source of HDPE, my local chinese take away put out 25 litre oil drums for recycling. These drums weight 250g each, whereas a 4 pint milk bottle weighs about 30g.
There might be traces of oil (or maybe silicone from your baking paper) on the material - alternatively, any temperature difference between the two pieces may mean that one was shrinking with respect to the other - which would prevent them sticking. I don't really have much experience of working this material in ovens and grills - but I do know the pressure I use when I clamp down the sandwich toaster is important in forcing the material to crosslink
I have added a few molten hdpe sheets form the toaster to the bowl in the oven before, the stuff is like hot toffee, the minute it touches it it grabs onto each other. I think you are right, some contaminate got introduced, though not from the baking paper as this worked successfully before. I know one way now how not to do it.
I have been turning bracelets on my lathe. I then put the shavings on to a cookie sheet and turn them into sheets for easier storage. When I take the HDPE out of the oven and let it cool in the air, it crackles and pops, and detaches itself from the cookie sheet withing 90 second, just by its own contraction. The sheets usually end up looking much like Pringles chips with a similar saddle shape.
Yes, A.T, that was useful. Saving us time and bother by experimenting for us. Keep up the good work 👍🏼
Very cool, looks like a soapdish
Very cool! I think that shape would make a nice scoop, for soil or pet food...something!
Very instructive !
Very useful information. 👍🏻
The logic for this result is easy. A thin upper layer solidified and shrunk without distorting because it was sitting on top of soft melted plastic. As the centre and bottom solidified and shrunk, the stiff upper layer acted as scaffolding and hence the above result.
Absolutely correct - and it's has to be allowed for in any project where this material is being shaped - even when pressing it into a block, the faces tend to pull in and become concave.
So interesting, thank you !!
Hmm, I wonder what happens when you dip it in a pool of ice water. Interesting video, thank you!
Good question - I can easily test this in one of my forthcoming videos... stay tuned!
You could get a couple of metal mixing bowls that nest well together and use them for a mold......I'd like to see how that turns out :)
I tried it - it does work, but you need to preheat the bowls or the plastic shrinks as soon as it touches them
With the tiles you were going to put on a boat, do you think they would make a waterproof bathroom floor, or would they not stick
I think it would be hard to find any kind of glue or cement that would stick them down - also, the material is very slippery, so that might not be the best idea for a floor surface
I wonder if using something like a air-can spray, or even a tight-nozzled CO2 can, could be used going from the outer edge inward, to make a more even curved edge for a bowl or plate.
I've been planning to make some custom pistol grips out of HDPE. I've been watching your videos to try to find out as much as I can, and after seeing your mixing bowl and your palette videos I'm beginning to think that it's doable. I don't really have any good ideas as to how to make the mold. Do you have any ideas? I'd need to be able to mold very accurately, and be able to release the grips without destroying the mold.
I would suggest maybe moulding blanks and machining to the correct shape using a small CNC mill.
Reason being, this stuff shrinks like crazy when it cools, so you would have to make your moulds bigger than the desired size of the finished article - but the problem then is that as it shrinks, it pulls away from the mould faces and this leaves it free to buckle
AtomicShrimp shoot, it's a shame that it shrinks so much. Have you experimented with gradually reducing the heat, or possibly dunking the newly cast pieces into cold water? I'd imagine that might change the cooling (and shrinking) process.
I wonder if this could be done with hdpe between two old baking trays in the oven?
you can also use weight instead of clamping until it cools
Got a question; if u put a shaft in a cooling mass of hdep wil it come out easily or will it remain stick in the collen mass?
nice vids by the way !!
The plastic will tend to shrink and grip the shaft, but if it's smooth, it would probably come out, or if it's threaded, it could be unscrewed. I've remade a couple of kitchen utensil handles and the plastic grips onto the tang really well
ok tnx
Fascinating
mmm i have a question, you said that as it colds down then it contracts and tears apart, but what about if i, somehow, make some 3d filament for indoors use? the problem is that i do pest control service to some restaurants, and they have a lot of plastic boxes [HDPE] (which for me as a 3d printer guy is a big waste of material) and i would like to make my own filament.
KARLOS :v I don't think it will work. The contraction occurs during initial cooling - I think if you try to 3D print with HDPE, the printed item will distort and possibly pull itself apart before it is even finished printing
I wonder if you could make large thin sheets of HDPE with fiberglass embedded. Could be great as a building materials. Plastic sheet, rigid insulation foam and another plastic sheet.
Dejay Rezme possibly, but shrinkage of the material as it cools, would mean the glass fibres would not be under any tension, defeating most of the strength advantage
Oh right, true!
It would probably make more sense to somehow have a roller to extrude a sheet. I guess you could on fiberglass but that is probably not really practical.
Maybe you could mix in fibers?
Maybe you could mold larger "bricks" and fill them with foam as a building material.
Where to find a sandwich griddle like this. All I can find is a small 11”x9” type
I am curious? I saw another vid where the guy said to use # 2 plastic. Can you use different numbers of plastic, or only #2.
#2 is HDPE - #4 is LDPE - similar plastics, but different material properties - they can be mixed, although the results may be unpredictable
Thank you for letting me know.
I broke the handle clean off my sandwich press from too much pressure.
And when you do clamp HDPE to cool it you impart internal stresses into the material. I know this from machining it afterwards.
Yes - I've seen that too - pieces I thought were flat went all wavy at the edges when cut
AtomicShrimp this went bad for me i.imgur.com/eBfoT6s.jpg after I cut it those pieces kept on curling up and interfering with each other. There was no fixing it either. Although this didn't work too bad i.imgur.com/lSsNyBG.jpg Because the cuts are much shallower I suppose. I make thick loaf like bricks of HDPE in an oven, then clamp it as it cools so it does not crown up on me. Then I mill it in a milling machine. But I've abandoned this whole avenue of HDPE dovetail axis stage design. It simply does not perform well enough. I ended up settling on this i.imgur.com/KI7lIAm.jpg Which can run much faster while remaining rigid. I'll give you mad bonus points if you can name where I got the aluminum stock from in the third picture. It's pretty funny what that was. But it works good for this.
I've never tried making anything that thick, at least not where tolerances mattered at all
I don't think it is the thickness of the stock that matters but the percentage of stock that is cut away? At least that is when problems arose for me. Other materials with internal stresses can do the same thing. After that happened I tried to relieve the internal stresses in another piece I'd made by remelting it. That proved to be somewhat less than practical to do though. So I never pursued it very far.
he sounds like r. crowe. love!
can hdpe be melted in counter top oven which uses bar heating elements, or is convection better, what about using a steel mold with a clamped lid to ' cast ' shapes.(( heat the mold to prevent rapid cooling))
I'm not really sure about oven types - I suspect radiant heating might scorch the plastic, but I'm not really qualified to answer on this as I always just use the press.
Heating a mould will definitely help in retaining the shape of the item without distortion, but it will reduce the number of pieces that can be made in any given time. Might be worth it for an item that needs a quality finish with no further shaping. Check out Amateur Redneck Workshop - he's succeeded in injection-moulding some very nice pieces.
will have a look at the pressing melt, should have enough time to transfer to a mold, IM is a bit out of my league,
I use a toaster oven . it works great
When you mix the colors like that, it almost looks edible :P
Sandwich between two bowls hey presto free bowl.
i think you gave to soon it could be a bowl throw some crazy shaped soap in it and sell it for a bathroom design
What kind of paper do you use?
It's nonstick baking tray liner - made from teflon or similar, I think. Search for Reusable Baking Liner on Amazon and you should find some
@@AtomicShrimp Thank you. Do you think using aluminum foil would work?
Not sure. Maybe the really thick stuff
There's something called "parchment paper" that looks like your baking sheets. I bought a roll of it and used it to bake a pizza, I lined the baking tray with it.
How do you chip your hdpe ?
The resin I used in this video is part of a batch that I ground up using my homemade grinder device - details in the link to follow, but I should say that the grinding machine was desperately unsafe and I don't recommend doing it this way: ua-cam.com/video/9qh1qQc3ats/v-deo.html
Why not just let it cool in the heated press by turning off the power - might take longer, but may give you a better product to work with.
Can do, but that's an hour-long duty cycle for each piece, back when I was mass producing the hexagons, that would have been way too slow.
Maybe try vacuum forming?
Good idea. I have an old vacuum cleaner that I could probably hack to provide the suction...
......... M6 nuts........ :D
candy dish
Maybe, but I've got a better one now - ua-cam.com/video/7QZceHIc2zQ/v-deo.html