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How about a golf ball which is a Sphericon or an Oloid? Would be interesting for putting and crazy golf.
I’d really like to know what is the largest diameter of filament which an extruder like this could possibly make in PET. Could it go to 10mm maybe?
If so, what would be the radius it would bend to ? In other words, how big would the spool need to be?
@3dseed That sucks… I’m sure it’s related to the legal side of things, probably also connected with their investors. I looked at those ISO codes at the bottom of that page, the first one is about quality control, but the others relate to medical devices and aerospace parts. That’s the type of thing which requires such high standards.
In that case, better to set up PP print farms independently, with injection services, and connect with customers through a central PP hub (which would also need some rules, quality control etc.)
In my mind there’s no doubt that 3d printing will play a central role in the future of this movement, and the barriers are not so big.
@occupypp Definitely looking forward to seeing an automated injector, this is the dream for PP!
@3dseed (or @3d-seed ?) Maybe you could look into providing an online service of printing in recycled PET via 3dhubs.com? I looks like you already have the capabilities and everything almost in place..
Solar is definitely the way forward, using muscle-power would be a great addition – but why enslave donkeys or horses when you can charge people for a gym membership?
Could be 3/4 inch (=19mm), and 1″ =26mm
Maybe try a 3/4″ keyed shaft with a 3/4″ to 1″ adapter sleeve
If you don’t have any machine tools, I suggest http://www.3dhubs.com to have the moulds CNC machined from aluminium. You could use http://www.fiverr.com to find someone to turn the image into a 3D file for the mould, then send that to 3dhubs and they will send you the finished mould. However it might not be cost effective for you do this for such a short run of only 50 pieces, maybe you could make more of them to make it worthwhile.
There is always space for an alternative forum. As happens in many domains of interest, a new forum will likely not detract from existing efforts and may even feed back constructively to PP. I have seen this happen with other forums, and the new sister forum tends to take on a slightly different character can be a good thing. Personally I would like to see a phpBB forum which focuses particularly on the more advanced technical side of PP work – machine building and research. This could be a healthy compliment to PP, and a refuge for those who don’t want to ‘fade away’.
Nice! the problem with larger blocks of hdpe is they end up with voids inside. This is due gas bubbles and the only way to get rid of them seems to be to squish the plastic with such enormous force that they compress until invisible. You might be able to reduce their size by adding stiff springs to the bolts so that the plate can move down further as the plastic melts in the mould.
I also wanted to create blanks, to turn on a lathe, but the obstacle of voids made me choose a different method, as I cannot find an efficient way to generate enough force to compress blanks of the size I need. I’m looking into 3d printing with PET instead, because the shape of my product would require a complicated and expensive mould.
@occupypp It sounds like you are working on something similar to what I want to do, the PP extruder would make a great hot end for large scale printing. Would the smoothieboard run nema 34s?
The smoothieboard looks like an awesome piece of kit too
Something like this is just what i’m looking for, so an open source design for a PP 3d printer would be amazing!
These flat splodges might be a way of making bottle caps and milk bottles easier to turn into flakes without a shredder- I’m going to try planing the edge with an electric planer. It would be great to make small, uniform flakes with just a sandwich press and a planer. Can’t test it now though as its the middle of the night.
I did another experiment, this time with the caps on baking paper in the bottom of the air fryer bowl. It kinda worked, and using my half-finished press I was able to make my biggest useless splodge so far at about 200mm diameter. However, I’m not convinced that the air fryer is going to be very useful for my needs. The heating is too uneven and the base is like a big heatsink, so the bottoms of the caps don’t melt properly. I tried lifting the caps up on the wire shelf, which helped, but overal the sandwich toaster was much faster and easier. Direct conduction of heat is way faster than convection in air.
The plastic definitely benefits from being mixed so I can see why the screw extruder works well. Kitchen appliances are promising though as they are so widely available. Has anyone tried a tossing a ball of melted plastic in a meat mincer? I haven’t got one or I’d try today. I imagine what would come out would be like mincemeat, if the output were connected to a heated tube maybe it could make a crude extruder? The screw inside a meat grinder has a decreasing pitch to increase meat pressure towards the blades. Maybe without the blades it would be enough to move the plastic along the tube?
Although the airfryer may not be useful in the end, these experiments have really helped me appreciate the nature of the material. I can see now that it really prefers to be about 3-5mm thick, any thicker and it moves around like crazy, and if it’s really thick it gets voids and bubbles inside. I had planned to create large billets of HDPE and turn them on a lathe, but I can see now that it would be much less effort and use less energy to make a really good mould where the wall thickness is consistent throughout. I can also see a serious advantage in controlling the temperature of the mould itself, by preheating in an oven at the very least.
@ppboys seems haptic actuators are a cheaply available component now: https://uk.farnell.com/texas-instruments/drv2605yzft/haptic-driver-erm-lra-actuator/dp/2307949?gclid=EAIaIQobChMI0PD-sPet5AIVCYjVCh06fg9tEAQYBCABEgI4MfD_BwE&gross_price=true&mckv=eRO8WYWS_dc|pcrid|78108376509|&CAWELAID=120173390000222732&CAGPSPN=pla&CAAGID=14406255429&CMP=KNC-GUK-GEN-SHOPPING-2307949&CATCI=pla-57456876370
but hey thats all stupidly complicated. Why not just 3d print the QR code and then toss it into a round mould and squash some melted plastic on top of it?
Alternatively to produce a flat bi-coloured coin it could be an array of 3d printer-type filament extruder nozzles pointing up into the bottom of the mould, extruding with one colour, with a larger injector sending a different colour plastic into the top of the mould. The same stacked array approach might be neccessary.
@ppboys Fun stuff indeed! Not sure the bowden cables are necessary, there are tiny stepper motors available very cheap which could be stacked in offset layers and drive the lead screws directly. Sketch represents 8.5x9mm steppers in 4 layers to give a 10×10 grid in under 50mm square (but yes I can see 20×20 would be required)
There is a trend for companies to start their own crypto-currency as an alternative to selling shares. There are thousands of them out there now. As an open-source, decentralized movement, PP cannot sell shares, but a PP coin could be a good way for all of us to generate funding out of the growing appetite in society for initiatives which address the plastic problem. If I want to buy a shredder, for example, I can sell PP coins in my community to fund it, and in the process both generate awareness and engagement, and boost the value of the coin. The plastic coins and bars themselves would just be tokens, something of a promotional gimmick, the actual validation of the coin still takes place online.
Hmm has anyone tried to injection-mould a QR code yet?
@s2019 Thanks! Yes you’re right, I might need to beef up the bottom rails. But I think I’ll go side-by-side again, I’d like to find a thick flat plate to put each side and leave a space in the middle so I can fit long things vertically into the press. Maybe one day I’ll add an adaptation with a heated tube and plunger running down through the middle so I can use it to make an injector…
From what I’ve been reading it seems that the main way to reduce air bubbles, aside from having the plastic clean, dry, well melted and mixed; is of course to use enormous pressure. The press I am building is currently only set up with a 2 ton jack. I am wondering if anyone can share their experiences about how much pressure is necessary? Is it worth upgrading to a 10 or even 20 ton press?
@s2019 It’s a great idea, air fryers come up cheap secondhand here in the uk because they are basically not very good for cooking as the capacity is usually quite small. For normal cooking it’s easier to bake in the oven.
I’m on the lookout for one and will definitely test the idea as soon as I can. It could be ideal for my purposes as I can put the heater directly on top of my mould and heat the plastic in it.
I am also interested in this subject, I am currently aiming to produce cylindrical HDPE billets or blanks, around 150mm diameter and 60mm deep. This is fairly ambitious and bubbles will probably be the main problem, particularly as I hope eventually to turn the blanks on a lathe.
I have read that making sure that the plastic is extremely dry is important, as any trace of moisture will lead to bubbles. However, the voids caused by shrinkage on cooling seem to be more difficult to address.
I am hoping to make these billets in cylindrical steel moulds made from sections of old gas bottles (the smaller diameter type such as for welding gases). The base will be attatched by bolts and the lid will slide inside the cylinder to compress the plastic. My current plan is to melt the HDPE in the open mould, in an oven with the upgraded thermocouple as used on the PP compression machine. Once melted I will remove it from the oven, insert the lid and transfer the mould to my press for compression. I will leave it under pressure to cool.
I have been thinking that it might help to reduce bubbles if I were to add an in-line spring to the lid of the mould, so that pressure can be maintained by the press as the plastic shrinks. The press compresses the spring with the plastic, but the spring should then expand as the plastic shrinks. I think the ideal type of spring would be the type used in bike frame suspension, as they are widely available as scrap, and already come with a shaft and fittings which can be easily adapted.
Sadly I am working alone on this project so it will be some time before I can share any pics.
I think there’s a market for plastic marble worktops without legs. I would concentrate on making the worktops and think about legs later, and focus particularly on how to market your product and start making money.
One niche market you could target would be worktops for live-in van conversions. Van kitchens require lightweight worktops which are small in size. You can do an off-the-shelf size and more expensive bespoke sizes. An easy market to reach via van conversion forums and facebook groups.