Rotate Sawppy STLs For Printing

For future Sawppy iterations, I’ve decided I should put identifiers on 3D printed components to help with parts management. Another thing I could do to help other Sawppy builders is to orient the STL files for printing. I had published a set of Sawppy STL files upon request, but I did it reluctantly. Due to the challenges of precise dimension tolerances required for heat-set inserts to work well (plus interaction with other unyielding parts like 608 bearings) I expected that my STL files would not suffice for most builders. Which is why I made Sawppy’s Onshape CAD document public as well, so people can tweak dimensions and generate their own STLs.

My expectation turned out to be correct for some builders, who then had to learn enough Onshape to generate STLs tuned for their heat-set inserts and assorted other parts. But many others chose not to do so. I have since learned that a fraction of them were relative beginners who were intimidated by the thought of picking up CAD. They just wanted to download STL files, load into their printer slicer, and go.

Reducing Sawppy construction complexity was something already on my list for my own sanity, but it would also make Sawppy more approachable for beginners. It would be helpful if I could orient every STL file for printing. My published set of STL were oriented exactly as they were installed on Sawppy, and I expected 3D printing enthusiasts to know how to find the correct face to place on their print bed. I was wrong for the beginners, which I realized after receiving some messages asking for help. These messages included pictures of Sawppy parts printed in the wrong orientations. Not only are print layers in the wrong direction for optimal strength, the parts were also covered with auto-generated support structure that were difficult to remove.

This orientation challenge was the worst for Sawppy’s corner steering joints. These objects have an angled side that were the result of trigonometric math for scaling Curiosity’s suspension geometry, and the result was not a nice even number of degrees. Even worse, I had designed those faces to be facing the print bed. Which meant it was up to the user to find some way to make their slicer automatically align to this oddly-angled face. At the time I was using Simplify3D as my slicer, which has a straightforward “Place Surface on Bed” tool. Unfortunately not every slicer has an equivalent feature, and even if it did, it may be named differently. Thanks to the Sawppy community I collected information on how to do this for several other slicers, but it would be better if people didn’t need to worry about it at all. I did the math in CAD, I can perform the rotation in CAD so nobody else has to deal with it.

Doing so would raise the odds of success for relative beginners to build Sawppy, without penalizing people investigating advanced techniques like adapting Ardupilot.

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