printing joined moving metal parts

Discussion in 'Technologies and Hardware' started by dadrummond, Nov 5, 2009.

  1. dadrummond
    dadrummond Member
    I'm working on a mechanical design to be printed in metal -- hinges and springs, mostly. I'd become convinced that printing moving parts in metal was impossible. But then, for the tenth time, I watched the "Shapeways 3D metal printing" video (here) and realized that at the end, a) the Moebius Ants model is printed as a single piece, and b) the ants remain free to run around the track.

    My intuition for the steel process is now in disarray. I had guessed that parts would remain separate after the initial printing, and perhaps even the sintering/curing step, but had thought that the bronze infiltration step would be certain to fuse any parts that were touching. Because the ants (again, in my head) were lifted out of the support material and put back in for infiltration, I believed they would almost certainly end up touching one another. Obviously, that didn't happen.

    So: why did the ants work in metal? What are the design principles for moving parts? Can we print separate parts with clearances of, say, 1mm, and have confidence that they won't fuse during the later production steps? Thanks for the guidance.
     
  2. GlenG
    GlenG New Member
    There are tricks to keep closely spaced parts from fusing during infiltration. However, results still may vary. These configurations give the shop techs fits! Also the raw print surfaces are relatively rough and if a smooth running fit is desired, allowance for lapping must be considered. I have seen some "ball and socket" joints that worked out pretty well. Make sure to use fillets on high stress areas to increase strength of the joints.
     
  3. dadrummond
    dadrummond Member
    Thanks. You say there are tricks -- what are they?
     
  4. dadrummond
    dadrummond Member
    Note that I don't want to give the operators fits! What I do want is to understand the process at a deep level so that, in an ideal world, I can design the most interesting mechanisms that will reliably print.

    In my defense, I figure that if Shapeways didn't want us to print things like Moebius Ants, they wouldn't have featured them so prominently on their video about metal printing.
     
  5. designerica
    designerica New Member
    was the verdict that we can't print moving metal parts? Is there a distance that will work?
     
  6. Magic
    Magic Well-Known Member
    In the case of the Brunnian Pendant the clearance is 1 mm.
    I suspect the minimum clearance necessary to avoid 2 moving parts from getting fused depends on the area that is in quasi-contact. In my case (cylinder vs perpendicular cylinder), the area is nearly 0. That why I wanted to try with only 0.5 mm, but I did not do so yet. :(
     
  7. noesis
    noesis New Member
    Bump.
    I received an email from Shapeways implying that moving parts aren't possible at all in metal, which I just refuse to believe! Now that it's been a while are there any other conclusions about this?