Solved Robo3D R1+ Z-axis endstop switch not engaging after carriage is lifted up. How to level?

My Robo3D R1+ has always has this problem, but it's gotten so bad that I can't seem to fix it. The 3d-printing carriage that slides along the X-axis isn't dropping back down onto the Z-axis endstop switches, leading to the firmware thinking that the extruder is bottoming out on the bed. This makes proper homing and leveling impossible.

A wide view showing the carriage lifted up off the endstop switch: https://i.imgur.com/u1hpFcX.jpg

A closer view: https://i.imgur.com/esl1VMH.jpeg

The above is an extreme illustration; usually it drops down a little but not all the way, and not enough to engage the switch. Note that the nut *is* aligned with the plastic housing. It can drop down, but requires a bit of force.

The yellow switch should be depressed by the plastic above it, which is supposed to drop down on its own.

I've lifted it up and lubricated everything, but still the carriage drops down in a very chunky manner, requiring force to push it in. I've done a rough leveling and followed the steps here: https://help.robo3d.com/hc/en-us/articles/115000724052-Z-Axis-endstop-fix

They don't actually address this situation, where it won't drop down on its own.

This has plagued my printer since the beginning, and very often I've had to fix it by giving the threaded rods fractions of a turn to put enough asymmetrical force on the carriage that it drops down when the carriage slides over. It's never been fully smooth, almost like the rods are bent inwards or the plastic rubs against the part that should drop down.

Does anyone have any advice on how to fix this?

 

It sounds like what I'm about to suggest will not fix the problem, but just in case: Be sure that the X gantry is parallel with the bed. If it's not, then one or the other switch won't engage properly, leading to the symptom you describe -- but you also describe a roughness to the motion that makes me think something's not fitting properly, rather than this being an issue of proper X gantry alignment. Still, it's worth checking.

 

The method I used for aligning the X gantry (the carrier on which the print-head slides on the x-axis, right?) is the following:

Move the printhead to the far right. Lower the z-axis to the bed so that a piece of paper can barely slide under the extruder.
Move the printhead to the far left. Rotate the threaded rod until paper can barely slide under the extruder.

Is this correct?

I then run G28 and G29 and expect auto-leveling to work, but the left microswitch doesn't get engaged properly.

I just tried bending the left threaded rod outwards (further left) and that makes the carrier drop down onto the microswitch properly. I don't know if that means it's bent, or it's just overcoming another misalignment. When I'm not actively pushing on the rod it doesn't drop down on its own, though.

Can I loosen and reseat the left stepper motor for the z-axis, maybe?

 

Yes, your method sounds correct. Something else is wrong, and following @mark tomlinson's advice is a good place to start. One thing I'd add is that the top cover, if it's in place, is designed to hold the smooth rods in place. If the smooth rods don't fit into the cutouts in the top of the cover, then they may be forced out of square. (That's what Mark meant by the smooth rods being "correctly held in place," I believe.) If they're not in place, you may need to remove the screws from the bottom of the cover (if the cover is screwed down), lift it a bit, reposition the smooth rods, and push the cover back down so that the smooth rods are correctly positioned. I've heard of people running R1+s with the cover completely removed, too, but I've never tried this myself.

 

Guys, thanks so much! I was an idiot and didn't know that the smooth rods actually went into guides at the top of the case! They were forced out of square by my improper reinstallation of the cover.

I was able to install the cover properly, re-do manual leveling, and then adjust the threaded rod a few fractions of a turn until the left z-axis switch properly engaged

The initial problem was probably a lack of lubrication or a switch that needed adjustment.