(Help!) Print bed moves too far on Y axis

Hi everyone,

I’ll try to explain this the best I can, and hopefully I can post a video soon. Recently when I press print, the printer homes all three axes like normal, but something seems terribly wrong with the y axis. The print bed will move as if to home the y axis, but then it “freaks out” and keeps moving toward the back of the printer. Seems as if the step motors keep running and pushes the bed all the way to the back. The the motor will continue to run, but the belt just slips on the pulleys since the bed is as far back as it can go. This lasts for about 5 seconds and then it finally homes and begins to print. What the hell is going on? Is this a firmware issue? Maybe something going on with the gcode? I’ll try to post a video at some time to better show what’s going on. I appreciate your thoughts and guidance on this!

If its a printer you have been using for a while that recently stopped behaving normally but you haven’t changed the firmware it’s most liley a problem with the end stop switch, either the placement, the switch itself, or the wiring / connection. It could also be your stepper motor / wiring. If it seems to also be moving twice as fast on Y as it should be and moving almost exactly twice as far, that could be the red wire on your stepper motor shorting out. I’d check all the connections, wires, and possibly consider swapping the X and y limit switches and seeing if the problem goes to the X axis or stays with Y.

You can also use the “M119” command in pronterface, to check the current endstop status. Send it once without the endstop being activated, and once again with the endstop manually triggered (held down with your finger). The endstop status should change. The Y axis endstop may have shifted further into the housing, causing it to not be triggered the way it would normally. A M3 setscrew is present within the brass heat-set insert above the endstop. The endstop housing should be visible and flush with the endstop mount housing. The lever should be activated when the y axis bed is moved to the back. Press the “Motors Off” button to move each axis around manually to easily check.

Problem solved! Thank you Orias for your advice.

I checked the Y-axis endstop by sending the code and found that it seemed to be working correctly. I then turned off the motors to check if the endstop was being engaged. Turns out that the damn wiring harness for the heat bed was getting caught underneath the bed and blocking the endstop. Easy fix and something I should have caught. Thanks again!