Minimum Wall Thickness?

Discussion in 'Miniatures and Scale Models' started by Mr_Trainiac, Jul 28, 2019.

  1. Mr_Trainiac
    Mr_Trainiac Member
    I am thinking about printing a train in kit form (i.e. flat) to reduce the price. My reasoning is that it would get rid of all the support structure a one piece shell would need. With that in mind, I would like to lay the sides flat on the build surface. In HO scale, they would be about .75” x 8.5”. What is the minimum thickness that you would recommend? Right now my design is 9 scale inches thick (7/64 real inches, 2.8 mm). Will 6 scale inches (1.75 mm) survive printing and shipping?
     
  2. 8_Perf
    8_Perf Well-Known Member
    If you are printing this yourself on a filament based printer, your logic is sound. Shapeways uses industrial printers that use either a resin or a laser sintered powder for the most part. This resin or powder acts as its own support material and either washes away in the case of resin or is brushed off for the powder. Its material that should not be charged for as "support" material as its re-used by them later. Unless your parts laid flat take up for less space in the printer, I doubt your savings will be that much. Submit it both ways and double check. Just my .02 cents.
     
  3. stonysmith
    stonysmith Well-Known Member Moderator
    In theory, you could go all the way to 0.3mm but such thin pieces will have a bad tendency to warp/curve during the post processing step.
     
  4. barkingdigger
    barkingdigger Well-Known Member
    If you are printing in "Versatile" plastic (the old "Strong & Flexible" nylon) then I can't help.

    But, if printing in Smooth Detail (the old FUD/FXD) the following should help: For an HO-scale boxcar side (say 1.5 inches by 6 inches) laid flat, a general wall thickness of 1.75mm would be ok, but will almost certainly warp a bit in production. Clamp it to a flat board and apply hot (but not boiling!) water to soften the resin, then a wash in cool water to "set" the new flatness. Generally you are aiming for a temp of around 50 degrees celcius - very hot to the touch, but not actually damaging to your skin. It would be stiffer if thicker, but will also be more expensive.
     
  5. Mr_Trainiac
    Mr_Trainiac Member
    I have used the boiling water trick to bend styrene before, and my model has tabs that lock the floor and roof to the side, so I hope that it stays together. I am testing out various orientations, whether a one piece shell or one in kit form would be cheaper.
     
  6. southernnscale
    southernnscale Well-Known Member
    I have done most of my models as one piece. the shell as the upper part I have put cross bars across to help keep the shape they can be cut off when the time come to put it together. I have done this with my brass models to keep walls from warping. This is in Z scale but it works! I also use min wall thickness to keep price down!
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  7. he6agon
    he6agon Well-Known Member
    For Smooth Detail I use 0.024" as the minimum thickness for walls, but I try to keep walls at least 0.040" thick. When I go with the minimum I will often try to reinforce the walls with some interior ribs. Walls that are 0.040" thick with interior ribs tend to avoid warping at all, but the interior ribs can be distracting on a model where the interior is visible.