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Finished the Mechanical Assembly


I have finished the physical assembly of the RBX1. I documented the build here:

I have a couple of tips:
-Print the wrist at an infill greater than 40%. This piece snapped on me during assembly.
-Use a heat gun to soften the base of the wrist to make it easier to push the bearing on the bottom into place.
-I used a jam nut ( instead of the M8 locknut for securing the m8 rod with the end threading into the wrist. I was unable to fit a regular locknut.
- I was not achieving smooth motion from the rigid coupler in the forearm because the dimensions of the part were off. I fixed this by using a smaller coupler (
-I found the M8 rod with the threaded end that connected the forearm to the wrist was too long. I cut off about 15mm with a hack saw)
- I had to super glue the heads of the nuts into place that hold the base to the steel plate because there was no way to prevent them from spinning with the gear in place.

I'm still trying to determine the optimal way to attach the drive gear of the servo to the gear of the gripper. Let me know if you have any questions.


Dr. D-Flo


  • Well, that's pretty exciting and inspirational. I've had a few places where the tolerances weren't quite perfect, and had to ream them out.

    The wrist is interesting, and will break like you saw right at the point where the uprights depart from the more solid base part. I looked in my slicer (Simplify3D) and saw that the infill gets pretty sparse at that exact area. My solution was to make the infill for that particular area higher (50%) as compared to the rest of the print. You can do this in Simplify3D by using multiple processes. This saves you from having to use a higher infill for the whole part, when really it's only needed for a few millimeters around that area.

    Did you find the shoulder tensioners to be too tight? I found that the M4-20 screws would just barely catch the capture nut.

    Also, for those who might be embarking on the printing odyssey, it's very worthwhile to calibrate your printer for flow. Normally we just use 1.00 and things are fine, when printing trinkets. With these parts, the tolerances are close enough that overflow, or underflow will affect the fit. I had to reduce to .87 when printing with ColorFabb PLA/PHA. Otherwise, parts were printing too big, and not fitting together very well.

  • Ahh yes! I forgot to mention the dreaded tensioners. I went to Lowes and found a couple of nuts that were slightly more low profile than the ones we were given. I also used a soldering iron to push the both the head and nut farther into the 3D printed parts. However, I was able to get the belting very taunt without the tensioners, so if its causing a lot of problems you can definitely forgo the one in the wrist.

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