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From my limited experiments, thorough, extended melt time and lots of compression is what it takes to reduce/eliminate the voids.
You probably saw the threads, but I don’t think anyone has a recycled plastic to filament path that works using the PP extruder.
In the end of this thread https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/page/5/ , I made some bar stock material with my benchtop injection machine. It has about 200cc stroke volume and I can get up to a 125 g HDPE part out of it.
Another option to consider is to get a bunch of cartridge heaters and a PID/SSR/T-C bundle and make a custom compression mold for the size you want, probably under $50 to go that route.
Did you see the beam production thread https://davehakkens.nl/community/forums/topic/beam-production-v4/ ? Depending on the size of beams you are planning to make, they can take a while to extrude so it might be a pretty good workout with a hand crank, maybe a bicycle drive is easier. Also the beams produced have chance of voids.
For making sheet stock, I would consider making a compression mold. Even for beams, compression molds may be better.
The only tube making I’ve seen here was the work by @timslab and that used a wrap process, with the results being interesting, decorative, but not a replacement for tubing.
I think if you are making low restriction cavity molds, you may be able to make a large volume injection machine using the arbor press/gear&rack approach.
Good luck and post your results.
@timslab , nice progress. Could you explain the right hand photo in image 1? How are the two rods anchored into the PP? That is a large void. Is the left image as extruded?
For cutting the slot, a low cost XY cross vise and an endmill or router bit in the drill press could make that easier than the chisel approach.
Good question. Getting rid of voids in larger pieces isn’t always easy.
I’m not sure the toaster melt and stuff it in a form approach will get you there. The people on youtube that appear to make solid parts do a lot of hand manipulation (folding, twisting, etc.) of the hot plastic during the melt. Note in a regular toaster the temperature of the plastic is basically unknown. The surface flakes see the hot elements and are, well, toasted (also releasing bad fumes). The rest is at some other temperature. The approach using a sandwich grill/press or the air fryers is probably better controlled.
I took a shot at making some stock material in this long thread https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/page/3/ . Most of it was using a DIY injection machine with the design and approach evolving over time, but if you look at the March 22 post I heated an aluminum tube and compressed some HDPE into a cylinder. Today, I still could not guarantee a part without some voids or bubbles. In general I heat the plastic longer and apply lots of compaction presses during heating and apply pressure (clamp) during cooldown.
Good luck and post your results.
@jovinc , Wow, that is a great investment. Hopefully you can publish some of the recorded data.
I think mapping what pressure is available at the nozzle for different plastics, nozzle diameters, temperatures, motor parameters (speed, torque, current) would greatly enhance the communities understanding of the extruder. It would also be interesting to know how the plastic flake size affects these since that will help size the shredder.
Thank you again for implementing a great piece of instrumentation.
I’m not sure what the advantage of Discord is over a well managed forum. Other than for initial brainstorming sessions, technical collaborations often benefit from some latency in that a well thought out post is often more valuable than a real time input, especially with wide ranging time zones. Forums do offer a chat feature.
Also, downloading an app and establishing an account with a third party to participate is not as attractive.
It will be interesting how the beta works out.
Do you expect the new platform to increase the frequency and depth of the updates for the V4 activities? Is that what the goal of day to day communication is talking about?
That would be great.
If you google HDPE density or properties for example, you will get a range of 930 to 970 kg/m^3 so it should float even in fresh water. When I’m washing plant pots (HDPE) for recycling, some float, some don’t. It may be residual dirt or additives.
There are threads on sorting plastics by density. For solids, density does not vary strongly enough with temperature or pressure to make it a worthwhile discriminant I don’t think. There is a thread in the V4 area https://davehakkens.nl/community/forums/topic/sorting-plastic-with-robotics-v4/ on using Raman effect for sorting plastic but there has not been an update in 3 months so it may be abandoned.
For the garbage patch issue, I think a good percentage is fishing nets which should be relatively easy to collect and identify. For the rest, there are some programs out there for robotic clean up (google ocean plastic robot) but they appear to be in very much concept stage. Not sure how you collect the small stuff.
I think testing the different ways of communicating to people about the existence of your collection point is a great experiment, and it also gets curious people to see the PP facility.
I’m curious how popular the Eindhoven municipal program is https://eindhovennews.com/features/2018/10/how-to-recycle-plastic-in-eindhoven/ . Are the orange topped bins in many locations? Are they used?
Is the forum being deactivated, and when ?
Good point, probably good to save any major write-ups off line.
If you use the arbor press configuration and mount it in a typical low cost floor standing shop press frame https://www.harborfreight.com/20-ton-shop-press-32879.html , you should have enough height to get the volume you want and you could add a mid-height pivot to lay it horizontally on a bench if you want.
I think of the arbor press and the rack and pinion as the same mechanism. The system should feed just fine in a horizontal configuration. I don’t think you need the two different orientations. Good project.
I don’t have an answer for you, but I personally would not make anything meant to hold food. I also don’t use plastic that originally held toxins. In between those two I take some comfort that plastics do get recycled by industry into usable objects. But, there is no guarantee.
Unless your workspace is in the middle of an open yard, you should have a fume management strategy for your configuration.
Just curious, how are the objectives for this effort different for the past press efforts? If you could post the requirements list for this effort, it would help clarify what you are trying to do.
There is a thread and CAD files for the shredder converted to inch units. Probably want to work your way backwards through the thread (also search for others) to get the latest updates. https://davehakkens.nl/community/forums/topic/shredder-converted-to-imperial-system-inches/page/3/
They are a little over 200 liters. We use them to catch rainwater from our gutters. I have been informed that rainwater is better for our plants than the stuff that comes out of the tap (that I drink). The concept of catching rainwater may not be common in Eindhoven.
I took another try at the laundry bottle labels (they are desirable because of the bright colors) . The plastic labels didn’t loosen with hot water, but a hot air gun will loosen them (the bottle plastic starts getting soft as well) and if peeled slowly they will come off in one piece without residue. I’ll do some experiments to see what temperature is needed. A hot box of some sort (solar?, air fryer?) will be useful to process a bunch of these.
@juul I really like your upcycled blue food barrels. We have a few similar barrels that were used to ship olives, etc. and once they are empty they are not reused or shipped back, and can be had very cheaply. We use them for rain barrels. After 2 years one of them still has that pepperoncini aroma.
@juul I’m not sure what you mean by cycling, but one option would be to make a larger version of a rotary rock tumbler. If you take one of your blue, upcycled food barrels that you have a sealing lid for, add some inside paddles (just some angle or equivalent), and lay it on a pair of rollers, you can drive one of the rollers with a stationary bike.
@btmetz , since you are in a sunny, hot place, I wonder if making a simple solar hot air collector out of sheet metal, aluminum cans, etc. and blowing that through your wet caps would help with the drying without needing extra machinery.
Since it is intended for unattended operation and you are sensing current, perhaps it would be useful to add a “hopper empty” or not feeding signal (light?) based of low current for an extended period of time.
Great experiment. I think the turbo cooker is what they are selling as air fryer in the states. Same features, heater, temperature control and a fan. I think, a larger version could be made using a metal bladed fan and some of the typical heater/PID/TC hardware.
I was surprised that the generic Chinese 12 ton or 20 ton hydraulic shop press isn’t available cheaply in the Philippines. It would make the build almost off the shelf.
Yes, once you get away from the screw on mold, there are several options for interfacing with the mold. I’m not sure you need the parallelogram. You only need a small motion to create an overlap with the mold. If you look at @andyn ‘s machine https://davehakkens.nl/community/forums/topic/benchtop-smaller-machines/ , he lets the cylinder float on a spring. In my machine, I went the other way and use a pair of shallow wedges to bring the mold up to a fixed nozzle.
Looks like you have a great project going.
Wow, that is a lot of plastic. If that bench is about 2m long, solid that would be about 300Kg. Do you expect this to be mixed plastic? Did you see some of the posts on roof tiles and pavers being cast out of mixed plastic? They were working with a fairly large scale machine.
I guess one question is how much would be exhausted outdoors without a filter. While pristine air is a goal, it would be interesting to compare the magnitudes in the test sample results to common sources (asphalt road on a hot day, etc.)
For some workspaces, staying on the carbon filter change regimen may be prohibitive.
If you look at cartridge heaters sometimes called mold heaters, a common size is 9.5x80mm and 300w. On ebay you can find them for a very low cost. You can then build your mold (aluminum) and just plan to drill a few holes for them. Control them with the typical PID/SSR/TC. Not sure what the advantage of the induction heating would be.