Legendary Octo Sniffle Progress

Most of the mechanical work for the Legendary Octo Sniffle is complete! I’ve resolved a few interesting issues:

  1. I initially intended to use one smooth rod per leg, with the smooth rod sitting behind the lead screw. You can see this concept in my speculative drawing from March 19th.I knew that placing the rod to the side of the lead screw would allow the lead screw to sit further back, allowing the effector arms to sit further back and afford more print area, but I thought to leave this as an exercise to my students.It turned out that the lead-screw-forward configuration gave an unacceptable loss of print area: I had to push it back and the smooth rod to the side. In doing that, I designed it to accommodate two rods per leg.

    Using two smooth rods is also superior. This is because the lead-screw nut is a little loose: it’s only designed for linear drive in one axis and it’s not very good at preventing motion in the other five axes. So the carriages, as configured in the picture above with only a single smooth rod, yaw just a tiny bit. But a second smooth rod per leg eliminates this yaw.

  2. I’m using magnetic effector joints. And specifically, I’ll begin by using this magnetic effector from Thingiverse.All of my prints so far has been in PLA, but I’m using ABS material for this print because of the high temperatures endured by the effector. Printing in ABS is hard! My cheap printer has a tough time keeping its print bed at 90 degrees celsius: a good temperature for keeping the object stuck to the bed during the print.I managed to get a single effector printed. The rest, which I am printing for my students, all popped off the bed; it was my first true spaghetti print. I’ll have to add insulation to my heat bed, and maybe an enclosure, in order to reliably print these parts.

Mechanically, I still need to complete the effector arms and attach the effector. I also have to mount the end-stop switches and the extruder. Then I’ll complete the electronics, including the power supply, a heated bed, and the RAMPS control board.

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