D-Bot Stepper-mounted Z-axis Endstop by dotorg

Last crawled date: 3 years ago

This is a custom bracket that can be mounted above the D-Bot's Z-axis steppers to stop the gantry from lowering beyond 40mm above the stepper. With the particular combination of parts on my build, this stops the gantry at about 325mm of Z height, slightly beyond the spec 320mm.
This is to solve the problem of having multiple Z steppers get out of alignment with each other. I'm running three, which just compounds the potential problem.
To align the steppers, I essentially z-home to zero, then lower the bed 310mm. At that point, I turn down the stepper current low enough to cause easy skipping. It then lowers the bed another 30mm, which lowers all three motors to the Z-stops evenly. Then the current is turned back up, and the bed Z-homed again.
This ensures bed leveling adjustments and mesh compensation stay accurate over time. Even if your controller can't be set up to do it automatically, you could do it manually when you want to verify they're all in alignment.
Installing is simple -- they're notched to fit around the threaded rod and the coupler, so all you need to do is unscrew your stepper, replace the 8mm M3s with 12mm, and screw this back in in the appropriate orientation to catch your z-axis nut bracket or rail. (Basically orient it to face inwards, it'll fit in any orientation relative to the existing motor mount.)
One warning on these -- depending on your motor torque, its possible you can stretch / damage your flexible couplings if you're using the D-bot recommended ones that look like aluminum springs. They're not strong enough to resist linear extension pressures. (Its a problem even without these stops being used for alignment, as too much roller friction can cause them to stretch a bit during moves.) I'd recommend using solid couplings instead of "flexible" ones. (Ie, if the ones you are using look like the ones in the photos above, you may have issues if you're running higher torque levels... ask me how I know...)