Stefan LochbrunnerSo far backlash hasn't really been a concern but the other day I had this idea that should help reducing it. It's similar to what was done in this machine which was recently featured on the blog where two nuts were pressed in opposite directions by some metal strips.
It came to me when I had this threaded rod with those two standoffs laying on my bench along with a small box of misc parts among which were some springs. I was just sort of playing around with these parts wanting to see how far I could compress this quite stiff spring but then something interesting happened: The spring locked the two standoffs together pretty much eliminating the backlash, although it depends on how tight the spring is compressed. Of course, as it is the standoffs aren't completely locked, especially when the rod is turning fast but that's an easy fix.
It's nothing revelatory but the way I stumbled upon it is somewhat amusing. As evidenced by the above example the general concept is a commonly known technique but the option of adjusting the pressure at any time makes for a nice feature.
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Haha, I kinda came across the same by clamping my thumb between two nuts. Wow that sounds bad. Between two short standoffs ;)
I'm still contemplating backlash reduction techniques. I ended up threading a couple plates myself. My intent was to have them secured via screws, so the two plates couldn't rotate WRT each other. One would be held by the screw-heads, the other held to the carriage body, tightening the screws would allow for adjusting the "tension" between the two plates, which would force one to one side of the threads, and the other to the other side, like your spring does here...
That was the intention. The drilling was accidentally angled a bit to the surface of the plate (not perpendicular). So I realized that quite a bit of backlash can be removed by essentially tilting the "nut" and so-far I'm getting pretty good results using only one (tilted) mounting-plate despite having made two.
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Interesting that the tilted one works so well; I think I heard of something like this before. I didn't mention it in the log but so far I use a pieces of square aluminum profile with threaded holes to drive the stages. It works alright but I expect it to wear out somewhat quickly so the above approach is my backup plan although I have no idea yet how I'm going to attach the standoffs to the stages. Your approach on the other hand sounds way easier to implement such that I'm probably going to have to give it a try.
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