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variations little & long

A project log for A Cheap Compact Linear Slide

<$10. <10μm repeatable. >10kg capacity. Laser-cut 1/8" hardboard. For 100mm x 6mm rod, but semi-parametric. Handwheel or stepper drive. CAD.

Paul McClayPaul McClay 11/05/2021 at 08:370 Comments

Trying some variations on the theme...

Little:

Using long (LUU) bearings on two rods instead of three. Trades range of motion for simplicity. No room for internal motor but simple enough to make wider for an externally driven leadscrew.

As of writing this, I haven't published the CAD model yet.


Long:

Just bigger #rodl in the published model...

First try came out half baked. No surprise for making it mostly to see how bad it would be, and how it would be bad. Result: the ends pre-load bow into the sides (not new) and the silly-long bendy sides bow enough to interfere in the middle.

I have a couple of ideas to try for fixing that without adding a lot more material/bulk.

Once again I'm surprised by how not floppy the slide is at full extension - even with the extra-long sides gaining multiplied leverage across the extremely short overlap. Of course long narrow strips of hardboard flex easily so the overall result is far from "rigid", but even at full extension the tiny overlap holds up better than I would believe if I wasn't holding it myself.

The bendy sides only have to maintain relative orientation of the ends. It's really just the two ends in the middle constraining where the rods and bearings intersect the two nearly coincident planes that make the slide much more stiff than an equivalent span of hardboard. Kinda neat, IMO.

The sides don't bend so much edgewise, but slide the mechanics allow a tiny bit of free rotation (yaw) at minimum overlap (bearing motion almost tangent to rods). The very long sides exaggerate that, allowing the middle to deviate ~1mm to either side. It's palpable but doesn't look bad at arms length:

(the mill has motors inside the slides so they never get to minimum overlap)

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