OpenSCAD, ReplicatorG, why can’t we all just get along?

I need to bolt some shelving to the wall.  Yes, I know the shelves came with some hardware for doing that – but I own a 3D printer and I can design BETTER hardware.  I whipped something up in Sketchup and printed off some brackets.  Next, I needed a slight variation in order to bolt two shelving units to each other.  (Something for which their hardware wasn’t designed).

Unfortunately, ReplicatorG just puked all over itself as soon as I tried to slice the bracket.  I had been tinkering with OpenSCAD for the last week or so, so I figured I’d give that a shot.  Here’s what I tried:

  • First, I tried building the bracket up out of just rectangular boxes.  This was okay, but cumbersome.
  • Next, I tried to design a really really complex polyhedron in the shape of my bracket.  This was a nightmare.  To do it properly, you need to design your object such that you’re defining each of the triangles that make up the object.  If you get set up the triangles by putting the numbers for each corner in the wrong order, in a less-right order, or did some other benign thing, it would make a mess.
  • After chatting with Clothbot, I tried to define a cross section of my bracket as a flat image in Sketchup (again), then tried to expert it to a DXF through a plugin.  I just couldn’t manage to extrude that flat DXF into a 3D image.
  • So, I went back to Sketchup and tried to tinker with the file again, fixed it in CADSpan, exported to STL again, fixed it up with NetFabb again, and ReplicatorG still barfed it up.
  • Back to OpenSCAD (again).  This time I tried to assemble a 2D cross section of other shapes.  This didn’t work as I tried to tinker with the “linear_extrude” function.
  • THEN, finally, I tried to define a polygon (not a polyhedron) based upon the coordinates I had used originally to describe the bracket when I was attempting to build it out of triangles.  This worked to describe a flat 2D section of the bracket.  I tried the “linear_extrude” function again and it worked well.  I then punched a few holes into the bracket with some small cylinders and exported to an STL again.  It’s my understanding that OpenSCAD makes quality STL files – without holes or other cleanup required.  While that may be the case, you guessed it, ReplicatorG tossed its cookies when it saw this bracket.

So, what is it? Is it the bracket?  Sketchup and ReplicatorG?  Is it OpenSCAD?  Suggestions?

4 Responses to “OpenSCAD, ReplicatorG, why can’t we all just get along?”

  1. Marty says:

    One thing to watch out for when using OpenSCAD is leaving infinitely-thing faces when subtracting.

    For example, if you start with a cube sitting on the X,Y plane, and subtract a smaller cube from it that also rests on the X,Y plane, you end up with an infinitely thin wall where the two cubes shared a face, and this can mess up objects for printing. To get rid of them, just offset the object a little bit (and make it a little longer on the correct axis).

    That being said, it sounds like some other issue is going on since RepG is barfing even though you’re trying different programs. You might want to try slicing another model that has worked before to see if your RepG/skeinforge is just somehow messed up.

  2. Xa says:

    Did you get a more specific error message than *puke*? Or did it just freeze up/crash?

  3. MakerBlock says:

    @Xa: Um, yes. :) Let me get those for you.

  4. MakerBlock says:

    @Xa: Dang, I can’t copy/paste from the error pages in RepG. It will have to be as non-specific as error messages. RepG didn’t freeze and didn’t crash, it just starting printing out lines in red text.