Allforge 3d moulder - Page 1
Forum section: electronics / general

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 14, 2016, 09:07:12 am
content: May be a neat idea, but showing signs of bullshit feature creep - "gesture wake functionality" , phone control when it already has a 10" screen"it's a machine that can bring families together"http://www.allforge.org/

author: kosine
author_rank: Regular Contributor
timestamp: May 16, 2016, 02:33:22 pm
content: Oh dear! Looks nice, but unlikely to be of much use. I've seen quite a few attempts at small moulding machines, some better than others*. Here's a few alternatives:http://www.mediummachinery.com/http://www.injectionmolder.net/http://www.techkits.com/http://www.alibaba.com/product-detail/Benchtop-Manual-plastic-injection-molding-machine_60163139156.htmlhttp://www.alibaba.com/product-detail/Desktop-Micro-Injection-Molding-Machine-for_60022090548.htmlhttp://www.amatrol.com/coursepage/plastics-learning-system-94-mp-3t/http://www.travin.co.uk/tp1.html(I used to have a Travin. Robust and functional, but not much control. Needs some sensors and actuators adding.)If you want to get into moulding properly all you need is a half decent CNC milling machine, and a secondhand moulder off ebay. Some go for under £2k, you just need a garage (with 3-phase) to put it in. (And a soldering iron for running repairs on the many circuit boards!)Not really any more ambitious than fixing-up classic cars and bikes, don't know why more people aren't doing it. Certainly possible at a hackerspace. You can make commercially saleable products on moulds that cost next to nothing. Weekend job in most cases. (I've done projects for school kids who've made some serious pocket money from their widgets. Enough to buy their own equipment in several cases!)* You need A LOT of force for injection moulding. Ideally 10-20T to clamp the mould shut, and 5-10T to inject the plastic. The designers of these small machine usually overlook mould cooling as well. Moulds get hot after just a few minutes when you're squirting 200C molten plastic into them!Plastic granules are cheap, by the way. A "sample" is usually a 25kg sack, and pretty much every mould-shop out there has bags of unused material lying around. They normally just dump it in the skip. Can't understand why 3D printing gets all the love!

author: CanadianAvenger
author_rank: Regular Contributor
timestamp: May 17, 2016, 02:53:58 am
content: I have a hard time believing this thing will work for anything other than low-temp things like chocolate and sugar, as they are using 3D-printed molds.

author: edavid
author_rank: Super Contributor
timestamp: May 17, 2016, 04:16:41 am
content: Quote from: CanadianAvenger on May 17, 2016, 02:53:58 amYou have to scroll down a little more:Quote

author: kosine
author_rank: Regular Contributor
timestamp: May 17, 2016, 09:10:48 am
content: 3D printed moulds have been tried a few times, but not very successfully. Metal-sintered moulds apparently don't give an adequate surface finish, although it's being worked on. I recall an Eastern European university team (Budapest perhaps?) was working with Stratasys on the issue a year or so ago. They were getting good results, but I don't think it was cheap.Homebrew FDM printers are way off. Even in polyamides (nylon 66) you'd have problems. It's usually processed at up to 280C, but I wouldn't want to put high temp plastics into such a mould - even at 200C. Firstly it's likely to stick, and secondly nylons will soften at much lower temps. The injection pressures are likely to warp it and moulds get progressively hotter during use. (Hence the need for cooling channels, though I think a PC water cooler would work.)There are some low melting point polymers you could use, but not sure if they're available as filaments. Polycaprolactone is a hard plastic that melts around 70C, so should work. But it's not cheap at £6/kg in bulk. On ebay they sell the granules as polymorph in the UK or Friendly Plastic in the US. Expect to pay up to £20/kg for it.Another option is ethylene vinyl acetate (EVA). It's much softer and cheaper, and some grades melt around 70C as well. Basically a softer version of the stuff they use for some hot-melt glue sticks. Stinks of vinegar, but I sometimes use it to plasticise (i.e., soften) polyolefins (i.e., polypropylene and polyethylene).There are a few biopolymers with low melt points as well, but they're not very commonly available. (Recall running some polyhydroxy butyrate a few years ago. Think it was made from bacteria. Stank like a damp forest floor!)If someone could make a hobby 3D printer than ran off granules instead of filament, you'd have the ability to roll your own compounds and go anywhere from stiff to soft just by changing the mix ratio. Not all polymers like to blend, but quite a few combinations work well.Moulding it is a totally different game, but I do agree there's a market out there for a hobby level system. (I've done some work on it in the past, but don't really have the time at present.)

author: tszaboo
author_rank: Super Contributor
timestamp: May 17, 2016, 09:29:02 am
content: I've talked with people who designed stuff which got injection moulded. Like case for custom electronics, that I've designed. The mould itself cost several thousand euros, and it is -not easy- to design them. Like you expect that you can make a wall simply 90 degrees, insted you need to make it 89, have it bevelled just a little bit, and have the wall be chamfered. Otherwise the thing doesnt even come out of the mold. And oversize it, because thermal expansion.This is probably fine if you want to print 20 Donald Ducks at home."One mold can equal hundreds of parts made at seconds or minutes a piece, all while costing you as little as $20 per mold - pennies per part. This is the lowest cost-per-part desktop manufacturing machine ever made." Yes. It is completely unrealistic.

author: kosine
author_rank: Regular Contributor
timestamp: May 17, 2016, 02:36:07 pm
content: I am one of those people who design stuff that gets injection moulded!Mass-production mould-tools, yeah, I get those made by people with better equipment, and you're right, it's not cheap. It also can take 2-3months to finish the job.But all the prototyping I do myself. Attached (hopefully!) are some examples of what can be done on cheap equipment. (Homebrew CNC + secondhand moulder.) None of the moulds for these parts cost much more than £20 in aluminium plate, so that part is actually correct. As is the "parts in seconds" bit. Depends on the part, but a 20-30second cycle time about par for the course.The moulds I make can take a few days to complete though, depending on complexity. But that's my time and effort - I'm not paying for anyone else's at that stage. Some of the moulds I've done have run many thousands of parts before they degrade too much, and if/when I do need to scale up, I already have a reference mould the pros can simply copy.I haven't done any proper electronics cases yet (though it's on my list!), but the two red rectangular pieces (bottom leftish) are end pieces for a stock aluminium extruded enclosure. They screw over the ends and support various headers and connector that stick out. Think that was a 2 or 3 day project, and I was making about 100 parts per hour. Not much harder to do a full size enclosure, just more CNC machine time.There's also a small motor at the bottom left that had to fit a Lego shaft. I made the non-standard coupler for it. That was a quite a bit more work due to needing sub 50micron tolerances, but the final fit was near perfect. (Had to make 5000 of those suckers.) Like you say, mould shrinkage is a pain to get right if pieces need to fit together, and deep parts also need a shallow taper to allow extraction. (Taper cutters aren't that expensive. About £15 delivered typically, and cutter last years if only working in aluminium.)So as dubious as this current Allforge machine is, I do think it's just a matter of time before someone does actually democratise injection moulding. The required tech is certainly available and has been for some time. What's missing is a development team that fully understand all the necessary aspects.

author: tszaboo
author_rank: Super Contributor
timestamp: May 18, 2016, 07:45:50 am
content: Interesting insight. And I'm actually impressed that someone can actually do this home, so cheers!Although it is probably obvious that these parts are "flat". And the surface finish is not even, probably because the CNC method. I wonder if they use some kind of chemical etching on the mould for commercial purposes to get that "grainy" finish?

author: kosine
author_rank: Regular Contributor
timestamp: May 18, 2016, 11:10:10 am
content: Nice to be appreciated! Maybe I should be doing some YouTube vids.Ahh, yes, that grainy finish... That's been done by "spark erosion", more correctly termed electro-discharge machining (EDM). The moulds I make are "machine-finish", so you get swirl patterns from the cutter. That can be polished out, however. (I did a memorial coaster last year and the mould for that was mirror finished. I might have a photo somewhere, though it's done a bit of work since I first made it...)With machining, you cut the negative of the part, with EDM you first cut an exact replica (copper or graphite) and then burn it into the metal with tiny lightning bolts. It's an added step in production, so adds to the cost. Normally only used for parts that require a cosmetic finish or have geometries too hard to machine. You can tell how much time someone spent making the mould by looking at the size of the speckles. The finer they are, the longer it takes. (You'll also only see the speckles on the outside. The inside surface is normally machined.)You can do this in a home workshop as well if you want. I think the Canadian chap who does AvE (Chris?) on YouTube is building one, and "The Post Apocalyptic Inventor" (Gerolf?) is assisting with the electrics in Germany.Some of the parts in my photo above may also look a bit "bubbly" - that's normally due to too much water content in the material. (My homebrew CNC will actually hit 10um, so the moulds are pretty good.) Choice of material makes a big difference, but for prototypes I often just use what I've got rather than sourcing specific grades. Colourants can also have a big effect, even though they're only added at 1%. (Had a big problem with the penguins due to needing different colours. Only two worked without significant bubbling.)And yes, most of my work is substantially flat. I can go deep if needed, possibly up to 50mm at a push, but it gets harder to cut the moulds, and harder remove the part. (Flat items just lift out nicely.) The other limit is the "shot weight" of the machine - i.e., how much material you can inject in one go. I'm limited to about 40ccm, and I'd guess these table top machines are considerably less. (The penguins used about 38ccm to give you an idea. They're solid polyurethane, and about 100x 60x 10mm in size.)I did the inside housings for these as well:http://www.kielowatts.co.uk/product/contact-colour-optionsThey're the black square in the mouldings photo with the 8 slots through them for the cap-touch contacts. Nice example of how plastics and electronics come together. (I ended up doing the circuitry and PCB layout for the first version as well. All old school 4000 series chips as he didn't want to use a microcontroller, but that's another story!)