Hollow Stainless Steel

Discussion in 'My Work In Progress' started by TurtlesAreCool, Sep 27, 2016.

  1. I am trying to make a spherical ornament, but I made it hollow to save money. The spherical shell is 2mm thick all the way around, with a decent-sized hole in the bottom to allow the extra metal powder to escape. However, I understand that they had issues trying to print the model, so I probably need to add some supports internally or thicken something to make it more printable. Does anyone have any suggestions for this?

    print-fail.PNG
     
  2. Youknowwho4eva
    Youknowwho4eva Well-Known Member
    Hmmm probably a problem with packing it for infusion. If they don't pack it tight, it probably sags from gravity. And it's hard to pack it tight with only the one hole.
     
  3. NoahLI
    NoahLI Well-Known Member
    so for infusion the prints are packed in green sand like for casting? if that's the case interior struts would make it even more difficult to pack. The only option might be printing it as 2 halves, then clamp the prints together and heat the seam till the bronze fuses the two halves together. the seam can be ground out and the whole thing polished afterwards.
     
  4. mkroeker
    mkroeker Well-Known Member
    If it is an issue due to thin walls, perhaps a few ribs along the inside would be sufficient ? If in doubt, reply to their message and ask for clarification or suggestions (worst they can do is direct you here :))
     
    Youknowwho4eva likes this.
  5. Are you referring to the "support material" during infusion? I guess I haven't made a hollow stainless print before, so I hadn't thought about that support material actually being inside the model. I thought the hole was only for the unprinted metal powder to escape, and that support material was place *around* the model. I'll have to find some production videos (I think there used to be some somewhere) and see if I can understand the size and shape of the material so I can strengthen the model appropriately.

    Thanks for the responses - familiar faces all. I was hoping to have this done for my cousin's wedding but I failed to start working in time. Oops.
     
  6. stonysmith
    stonysmith Well-Known Member Moderator
    Or make it two halves with an overlapping section inside that screws or locks together.
     
  7. Understood. The tough part with that is gonna be that I made the design very asymmetric. I suppose anything's possible, but my concern is that the cut would be pretty obvious when assembled unless the screw turns *exactly* the right distance.

    Let's say I do that. I use Blender, but working with boolean modifiers (as I did extensively here) is something of a painful process. Are there any suggestions for tools (preferably free?) that can cut a model like this in half? Blender could do it, but fixing the geometry after the cut could be painful.
     
  8. NoahLI
    NoahLI Well-Known Member
    I think the steel prints are packed in green sand, as if making a casting mold. In order to properly support the spherical shell the interior needs to have enough packed green sand inside so the shell doesn't warp or sag when bronze is flowed through the mold. Adding extra struts inside the sphere would only make it more difficult to pack the interior for the infusion stage. you need additional openings, preferably all around the sphere, to allow better packing of support material for the infusion; or cut the sphere in half so the shell can be properly supported for bronze infusion.

    you might be able to print this as a single cast metal piece, though more expensive than steel versions.
     
  9. stonysmith
    stonysmith Well-Known Member Moderator
    I would attempt such a cut in Netfabb Basic. It can do the cut rather nicely, but you'll then have to add the locking mechanism on the inside with some other drawing tool.
     
  10. I'll have to look again at Netfab. I use it to prep the model for Shapeways upload, but last time I tried, I recall that the boolean tools are disabled in the basic version. I'll test that out after I return from the wedding - thanks for the suggestion!
     
  11. stonysmith
    stonysmith Well-Known Member Moderator
    Yes, the boolean tools are disabled, but not the CUT tool.