garageFab.cc

It took me a couple of evenings to turn all of the "experimental" angle stock into usable pieces of perforated angle (or trash), since it involved a lot of sawing. To speed things up, I made a starter/sawing template for the angle fed into and made by the drilling contraption. I've also drilled one more 32" length, with couple more to go - still not sure about the wear of Delrin nut and backlash that may be increasing with every cycle. I really need to look at the rod whipping problem, however, I've been busy with other things. First, I changed the motor mount to have a better connection with the frame and really act as heatsink; second, as soon as I had enough perforated angle, I started making belt drive to test it out. Somehow I forgot that all the belts I had were short, so I bought some long ones from SDP/SI, and they finally arrived yesterday.

Teflon bearing pads

When I tested one of the newly drilled 24" angles as a rail for the sliding element, I discovered quite an unpleasant problem: due to slightly irregular thickness of the angle in different spots, the sliding element binds where the angle is thickest. I guess some angle pieces are more uniform than others, so this problem has not been as pronounced before. Even though the motion of the sliding elements, especially when tightened, has not been smooth, it did not feel like stop and go. While threaded rod drive may be strong enough to overcome this binding, belt drive will be nowhere near.

I hope to solve this problem by dropping the bearings from the sliding element design, and enveloping both corners of the angle in the teflon bearing pads. I don't think this will affect accuracy very much since it is pretty limited anyway due to the design choices - i.e. angle instead of heavy rigid structure with hardened shafts, etc. From what I see in the tests so far, teflon pads have a bit more friction, but the overall motion is smoother.

Belt drive

Yesterday I assembled one axis, driven by the belt. In the process I had to change the design of the threaded rod mounts (I think they should now be called axis mounts). I removed the large washer - this helps to hold the bearing centered over the hole for the shaft, and the hole is now 5/16" in diameter. I did not yet connect the belt to the sliding element because I do not have a new sliding element with teflon pads instead of ball bearings. After some tweaking the belt drive looks pretty good. Here is the video of it in action (though, idle action):