Sunday, August 25, 2013

fixing a toy cement truck with a 3D printer

I've been looking for an excuse to get familiar with openscad and a 3D printer I have access to. So I was happy when I thought of fixing my kid's broken toy truck. We bought a bag of vehicles from a second hand store and the cement mixer was missing the mixer barrel.
So I figured it would be the perfect project to make a new mixer barrel. I designed the barrel in openscad, and made it hollow to save on time and material. I uploaded the CAD files to thingiverse in case anyone ever wants to do something similar, and because their CAD pictures look great:
I printed the barrel in two pieces and added some marbles inside to jiggle around.

That's not the best picture, but it turned out great and actually spins!

I learned a lot about 3D printing, especially from many failed prints. Here are some of my tips:
  • slic3r
    • Occasionally I got errors when I imported an .stl file. Usually they were fixed by netfabb's online tool (or fixing my openscad source)
    • I originally assumed slic3r would pick the best print orientation, but it just prints from z=0 and up. So you need to design your .stl file accordingly.
    • Lots of helpful info here.
  • adhesion
    • I had lots of trouble with adhesion to the kapton when I first started. Sounds like the melted ABS in acetone slurry is the way to go, but I didn't try that.
    • I had good results when I flipped the plate over and printed on the bare glass, using hair spray to help stick. I removed the glass to clean with acetone (nail polish remover), then sprayed hair spray on it, clipped it back down and heated to print. 
  • spool
    • The spool kept getting bound up on almost every print. Usually because the plastic would get trapped on the inside and tighten up instead of unwinding. I didn't figure out how to fix this.
    • I did successfully restart a print that failed halfway through (instructions here).
  • leveling
    • I couldn't really tell anything from the bed calibration test print. It looked fine to me, but when I checked the level with the single piece of paper method, it seemed way off
  • air quality
    • I was surprised at how smelly the printer is. After a couple hours of sitting next to it, my lungs were not happy. If I ever need to use one again, I'll have to set up better ventilation.
I also had fun printing out different models from thingiverse:







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