Reusing plastic for vacuum forming
I use vacuum forms for fitting lasts to feet. It’s made of clear PET-G plastic sheets around 0.5mm thick. The key properties are that it needs to be rigid enough to keep the shape of the last (shoe) and clear enough so I can see if there are gaps as well as pressure points.
I’m open to different plastics that have those same properties. PET-G is very clear, which is great, but if it were cloudy, that would be fine too. Some details on how this is used in the fitting process and a picture of the form can be seen here: https://www.exitshoes.com/exit/custom-shoes/
No shop I have seen that uses a lot of sheet material for vacuum forming has a way to reuse the cut-off from forming. The forms themselves are often temporary and used for only one iteration and could themselves be recycled. This is all put in the “recycling” bin which just goes right to the landfill. Then they buy more new sheet stock.
How can we develop a system to make new sheets from the waste?
Long term, can we replace this material with something else?
Hi Jeff ( @shoemaker ),
Very interesting topic. I’m also looking into Vacuum Forming using recycled plastic, but I’m still stuck at the finding a ‘vacuum machine’ stage before I can do some real testing.
The idea is to ‘iron’ flat (using an heat press) cut bottles for use in a vacuum former..
Any advise for where I can look for an affordable vacuum former? Or a DIY build that actually works?
Alternative would be to go for a cheap ‘dental’ machine for testing.
Next step would be to indeed form sheets from pellets/shreds, which the PP V4 is also working on, though not specifically for vacuum forming.
Let’s figure this out!
I made my own vacuum press using pegboard and a heat lamp. I put the plastic sheets in a picture frame secured with the clips used normally to hold in the foam core backer behind a picture. The frame’s opening slightly smaller than the cut plastic sheet (12″ x 16″) but because the plastic is flexible, it snaps in easily enough. The channel on the inside of the frame is slightly larger than 12″ x 16″
I’ve always wanted to make the heating and frame better, but it’s totally functional.
I’m currently traveling (in the Netherlands!) and won’t be back to my shop for another week, so I can’t make any pictures of my setup, but there are tons of plans on line for the basic box, pegboard, and vacuum rig. I use a decent Miele vacuum because it has strong suction. Some shop vacuums more more air more quickly, but don’t have a strong pull once the vacuum seal has been made.
I’ll do some searching.
Enjoy your stay in the Netherlands. Bit of a rainy day today, but hey, I also don’t have to water my garden 😉
Some pictures on your return would be great, maybe even a video?
I’ll ask around if maybe somebody can help improve the design (if need be), but for now a simple setup should be good enough for testing.
KOIN, a local Portland TV station did a story on me in 2013 which shows the basic vacuum form setup. In that video, I’m using an aluminum window screen frame and binder clips to hold the plastic sheet. There is a shopvac down below which you can’t see, but can hear howling in the background. Look for it at 01:59.
Immediately following the forming is some explanation of how I use the vacuum form.
Great to see you at work. That’s some high skilled craftmanship!
I now also better understand the fitting process.
And a very simple vacuum setup indeed, I was thinking way to complicated.
I have an old Kirby vacuum that might be perfect for the job, heat lamps also should not be that hard to find, or maybe just use air heat it for now.
I’ll try to make a setup a.s.a.p. and maybe test it with some bottle plastic.
If this works, I can start trying to make and test recycled sheets.
to be continued…
A small update:
These topics are great reads regarding making the plates:
A second hand ‘panini’ press has been added to my shopping list 😉
I also found a heatlamp, even though it’s actually part of a grill plate. Should be enough to do A4 (vacuum) testing. Still looking for the pegboard, but I could always get it in the shop.
If you can get the material to the right temperature, it strikes me that something like a manual pasta machine (though wider) should be able to roll out sheets of consistent thickness.
The vacuum forming sheets are pretty thin – 0.5mm.
‘Rolling’ the sheets is also how it’s done on an industrial level.
In this needing thin sheets is actually an advantage, as you could almost ‘cold press’ them into submission!
Or using a hairdryer/paintstripper to pre-heat the sheets before pressing.
For small scale testing I can however use my heatpresses.
Here’s from page 100 of the Otto Bock catalog:
Was thinking more along the lines of a good old fashioned Mangle, but good to know we can always upscale the production!
Another one for the list!
I have been looking for a good mangle for years. Mostly the rollers are uneven, cracked or totally shot, or the alignment is terrible.
The best mangle I’ve ever seen was at Het Goed in Nijmegen after I first arrived. Still, they wanted €85 for it.
I possibly saw the same one in Nijmegen.
Nice product placement also 😉
With some tinkering it should be possible to repace the rolls with sand/cement filled pipes in the simpler older models, which often also allow for allignment of the rolls.
Probably easier to build one from scratch though…
For now I however have some old style cold press laminators in the attic that might be suitable for the small scale (a4) testing.
The Anyone with ideas on how to make plastic film sheets also has some useful information, especially the reply by @manix , confirming the heatpress theory.
Not on the topic of reusing the sheets, but some good links on building a Vacuum Former and some extra arguments why these should also be part of a Precious Plastics workshop: Alternatives to Metal Fabrication
Also becouse the next step could be blow molding:
Would be fun to be able to reshape existing bottles…
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(new to the community, hope you don’t mind if I chime in with random thoughts)
How hard would it be to DIY a roller press with two heavy gauge aluminum or steel tubes (not pipes, tubes)? Perhaps put some heating elements inside the pipes and then feed in feeder plastic from the PP extruder similar to how you would squirt ketchup onto a hotdog bun.
It would have to be oriented so that the pressed plastic sheet would exit from the bottom, and it would have to go relatively slowly so that the plastic extruder could keep up as it sweeps from end to end feeding molten plastic in, but it seems like it could work to me….
I wonder about the mixing of the shreds, air, etc? Perhaps a melting box with long slot?
After watching some videos of cutting board stock being made at factories, it looks like some kind of melting/extruder thing and two roll mill would do it. The two roll mill I found at OttoBock is a good one, but insanely expensive for what it is.
~$7,000 for the hand crank mill (89-W1) because it’s used in “medical” products, for example making orthotics and prosthetics. That mill is not even heated.
We would definitely want to avoid air bubbles in the feed stock and during the forming process as much as possible. I don’t know enough about plastics forming and extrusion to know how to avoid those issues though..
I suspect the $7k price tag for the hand crank mill is a case of very few competitors and relatively few customers, but those customers NEED the product, and they have the ability to pay a high amount… So, the seller can sell what the market can bear, and the market can bear $7k….
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