8 thoughts on “3-D Printing”

  1. I wonder how porous their metal items are. Perhaps extra metal can be added from the gas phase (via carbonyl compounds, perhaps.)

    1. I’ll add that many refractory metals form volatile carbonyl compounds so thi mmay be a good technique for forming objects composed of thrm. Rhenium in particular is formed by vapor phase deposition. Carbon carbon composites are also densified by decomposition of organic gases.

    2. Sounds similar to PMC (precious metal clay), a niche product hand-worked mostly by jewelers and sintered into solid pieces.

      It contracts 10%+ during the process, though, and I’d expect Desktop Metal’s parts do the same (rather than becoming porous), which will be quite tricky to manage.

  2. I thought the article was fairly negative about current 3D printing tech in plastic. You can use polycarbonate to get a tough plastic that works up to over 100 deg C.
    My 3D printer is on order. The company that used to CNC parts out of aluminum for us went bust and rather than find another one we’re going to 3D printed polycarbonate parts made on demand. Low stock inventory and the parts will be less than 1/10 the cost.
    I did see an article a couple of months ago where a company had 3D printed out of Inconel an M1911 pistol and put 1000 rounds through it. Barrel including rifling was printed and used as is.
    Isn’t Elon already printing Super Draco’s?

  3. I see no real barrier to having the EOS style DMLS laser printers decline down to the price of a nice CNC machine.
    IE 100K or so (presently 750K) The core patent that prevented people from copying their system has expired, I’m really surprised we have not seen a viable lower cost competitor.

    The polymer bound powder jet style of metal printers have too many problems and too many steps to be useful IMHO.

  4. Agree with Mike E. on the sintering/shrinking thing. Allowing for shrinkage as a part sinters is somewhat analogous to having to make mold cores the correct amount oversize or undersize so that parts, and any holes in them, come out an appropriate size as they cool that has long been a requirement for conventional – even ancient – metal casting technologies.

    This is tricky enough for homogeneous materials. For the kind of compound-material parts the Desktop Metal people were spitballing in the article, it’s going to be wicked difficult to harmonize the different thermal expansion/contraction characteristics of dissimilar materials printed into a single part, then sintered all at once.

    One will also be limited, in material heterogeneity, to combinations with roughly comparable sintering temperatures. Material combos in which one constituent has a melting point below the sintering temperature for the other won’t work with the described technology.

    Ironically, such combos are possible with existing laser or electron beam selective sintering machines as the sintering locus is very small. I haven’t done the research to know if any currently-on-the-market metal printing machines have multiple powder feed hoppers to support creation of non-homogeneous parts so this capability may well be strictly theoretical at the moment. And, of course, the small sintering locus is also one of the things that makes these machines slower than Desktop Metal’s.

    More broadly, I would say the described technology looks to be more semi-revolutionary than fully revolutionary. Existing metal printers can slowly make parts from a homogeneous material that have rough surface finishes. The Desktop Metal technology allows for making the same part, with the same poor-quality surface finish, quickly. That’s not nothing, but it’s not the holy grail either.

    What is needed is a technology that can produce parts with surface finishes as good as, say, a CNC vertical milling machine, but with an internal part complexity and material heterogeneity that is not possible for conventional carved-billet machining technology.

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