Metal Printing

  • Has anyone thought about or tried to make a DMLS printer with the duet board? 3d powder metal printing? i've seen videos of how they work and i just got curious to see what everybody's thoughts were. it's got to be possible.

  • Powder bed fusion is not a nice process to work with. It has numerous significant H&S risks that make your average reprap seem like a fluffy duvet!

    Powder bed fusion typically requires a closed processing enviroinment with recirculating the proceas gas through a safe change filter even for the 'safe' end of steels and cobalt chromes. Move to aluminimums and titanium and you are working with very flamable materials. Ideally many of the components within the processing environment should be ATEX rated so they can move after a build process has completed.

    All that said if tackled properly I would be interested to see a decent open source effort on sintering, perhaps starting on nylon rather than metal as it is more readily available, cheaper, and safer. I'm not sure if the duet is the right choice for the controller. The latest galvos when I was involved moved from analogue to digital drive and typically have a local controller doing the detail work of the mirror positioning and another fast digital device issuing digital commands.

    There is the robotic MIG welder approach for metals but more interesting to me right now is casting using PLA cores. Not exactly novel but still somethinh I want to see for myself.

  • While the acronym DMLS (direct metal laser sintering) is still used somewhat, I don't know of any system that sinters anymore. SLM (selective laser melting) is not a process for the basement hobbyist. As @DocTrucker described, the powders are very fine (10~45 micron diameter), making them combustible and the soot produced by the melting process is also combustible. Respirators are highly recommended, as are NFPA-rated (or European/Asian comparable) wet separation vacuum cleaners. And then, you have to start talking about proper disposal of the waste.

    All in all, not for the faint of heart. But, oh, it's a cool process!

    Somewhere last year, I saw a hobbyist-grade SLS system. That would be cool, too, but even nylon powder can get quite expensive.

  • I MIG weld on an off at my job.

    As others said, seriously nasty crap comes off of hot metal, there will most likely never be a open source-consumer grade product... ever.

    Ever set steel wool on fire? yeah, metal goes up pretty violently in powder or wool form.

  • Well I'll be damned.

    Prosumer no doubt, they are going to ask a fortune for those things.

  • Yes, sintering and melting are technically different processes but the mechanics are near identical. Stick to the term powder bed fusion and you're following standard terminology and avoiding trade names.

    Water bath vacuums are the way to go for most materials. I've been in the same building as things going very ugly after they where used for aluminium powder with no additives. Nasty.

    Desktop metal is something different.

    The desktop metal process is based on a similar process to how pstic sintering machines used to make parts. In that instance it was a plastic coated powder that was stuck together with the laser and then the green part was infilled I think it was a bronze material. In the desktop case the stock material has changed and I wonder how much of the original process has changed. Ironically for us the machine is very similar to our machines glue gun origins!

    The DMLS came from EOS. They're pre 2003ish offerrings used a fancy chemical system in an attempt to control the modt difficult aspect of the process - molten metal just wants to make tiny balls! In EOS's system (I'm assuming they now can work with standard metals now) they used I think it was called a eutectic alloy. The powder wad two component. In their original form both metals had a lower melt point than the alloy had when both parts mixed. So keep processing on the edge and you mrlt the alloy, it mixes, then freezes pretty quick. Neat, but not many optioms to process with specofic materials.

  • I think it was XJET who had a bery interesting process that has just been commercialised. Printing (as in print head jetting) a solution containing nano powder which is diffusion bonded significantly under its melting point.

    Nano powder makes me a little nervous but the fine black condensate from the laser processing in inert (welding gas) atmospheres is in the same ball park and not contained in a fluid.

  • I'm pretty sure the DesktopMetal Studio is USD120K+. It uses rods as filament, maybe 300-400mm long (don't recall the diameter, but maybe 5mm?). The rods are factory-packaged in a dispenser, and the head periodically stops extruding, goes over the the dispensing box of rods and grabs another one, then resumes the job. It's exactly like a hot glue gun, but these rods are a blend of polymer binder mixed with metal powder. The part is then placed in the microwave furnace (which is why it can be used in an office) to drive the binder out. There has to be waste, but I don't know what forms it's all in.

    They also have a larger system, and from what I recall, it's broadly similar to ExOne, HP and others that use a spray binder onto a bed of metal powder, producing a green part. You then bake it, driving the binder out, and shrinking the green part by 15-20% to get a pretty dense "solid" metal part.

    GE is also coming out with a similar binder jet system. They made some news last year by producing their own system in-house, from concept to working prototype, in like 90 days. Impressive, but not quite so much when it was realized they had extensive experience with multiple other companies' systems, and had already done a lot of "mental homework" of picking & choosing the best features, learning from other's mistakes, and treading a path between patents.

    The lowest cost laser powder-bed fusion machine I'm familiar with is from Xact Metal. A couple years ago their small unit was about USD80K.

    @DocTrucker - speaking of EOS, I'm traveling next week to their Texas office to evaluate an M400-4 (4x400W lasers) machine for our needs.

  • @plasticmetal My first hand experience is limited to old Realizer, and MCP/MTT/Renishaw machines up to 2013ish. First place I worked had earlier EOS systems but I was running the DTM/3D Systems plastic machines there.

    The field is, or at least was progressing very quickly. Left metals machines around 2014.

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