Precision Adjustable Z Endstop Holder and Constraint
by raldrich, published
A precision adjustable optical endstop holder for Prusa printers, with an integrated Z screw constraint bearing.
I got frustrated with trying to adjust my Z axis endstop by sliding the clamp up and down the smooth rail, and found that the available designs for adjustable clamps wouldn't work for me, for one reason or another.
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2) Trim off the support inside the bottom nut trap.
3) Ream out the inside of the Endstop Mount/Glide's M8 hole, so that it runs smoothly up and down your Z axis smooth rod. Â Â Â Â Note: I've found that the knurled end of a narrow X-Acto knife handle (with the blade removed) is the perfect size for reaming out M8 holes.
4) Install a 608 bearing into the bearing cup.
5) Attach an optical endstop to the glide, using 2 M3 X 25mm socket cap bolts and nylock nuts.
6) Optionally, run an M8 or 5/16 nut partway up your Z axis screw. This nut will be used to secure the top of the constraint bearing.
7) Assemble parts onto the smooth rod as follows (top to bottom): Â Â Â Â a) Glide/Endstop mount. Â Â Â Â b) 3/8" I.D. x 51/64" spring. Â Â Â Â c) Clamp/Bearing mount.
Â Â Â Â Note: you'll have to loosen your smooth rod, and slide it up out of its lower clamp, then re-affix it once the parts are in place.
8) Attach the Clamp/Bearing mount loosely to the smooth rod using 2 M3 X 20mm socket cap bolts and nylock nuts.
9) Assemble the adjustment bolt onto the assembly as follows (top to bottom): Â Â Â Â a) M4 x 40mm socket cap bolt. Â Â Â Â b) M4 washer Â Â Â Â c) Glide/Endstop mount. Â Â Â Â d) 11/64" I.D. x 5/8" spring. Â Â Â Â e) Clamp/Bearing mount. Â Â Â Â f) M4 nylock nut.
10) Move the clamp into its final position, and tighten the clamp bolts.
11) Optionally, secure the constraint bearing to the Z axis screw using 2 M8 or 5/16 nuts.
2x - M3 x 25mm socket cap bolt. 2x - M3 x 20mm socket cap bolt. 4x - M3 nylock nut. 4x - M3 washer. 1x - M4 x 40mm socket cap bolt. 1x - M4 nylock nut. 1x - M4 washer. 1x - 3/8" I.D. x 51/64" spring. 1x - 11/64" I.D. x 5/8" spring. 1x - Optical endstop. I used a MakerBot endstop, but any optical endstop with 19mm mounting hole spacing should work.
Note: If you look carefully at the photo, you'll see that I didn't use #6/32 bolts and nylock nuts on mine, instead of M3, simply because that's what I had on hand. The .stl provided is sized for M3 bolts.
Note: The springs I used came from a spring assortment kit sold by Home Depot - Everbilt #471864.