# Y axis moves, when only X is commanded

dc42

My guess is that one of the belt sections whose length varies with XY position isn't exactly parallel to the corresponding axis.

FxxToo

@deckingman Thanks for the Reply. I did those tests, and the results were as stated in the wiki.

MSquared

I had the exact same issue just last night after swapping a couple of my motors.

Turns out the reason was a crap connection on one of the leads to one of my motors. I should have known this by the sounds it was making but since it was new motors I overlooked that. The way I diagnosed the issue was to unplug one motor (duet off obviously) and then command it to move with a single motor. One of the motors worked and was quiet, one of the motors did not and was loud. I narrowed it down to further by removing the pins from the molex connectors and holding the pairs together to see if it made the motor harder to turn by hand or not. One pair did not, so replaced both of those connectors (while also testing the bare wire just to be sure) and viola' working printer.

Assuming that you have the motor directions and everything setup properly as you suspect that you do; this could be a culprit.

FxxToo

@dc42 Thanks for your reply. I just tried swapping the test and If I move the Y first, the X moves, just like the Y did. So that means you are right. Now I am not sure how to proceed.

When I was putting it together I used a 12" caliper and a extension rod that I filed to 6" to use to extend the only way I had of accurately measuring the distances. I measured distances between the X at the ends of the rails and the same on the Y. I believe that I am at .001" or less end to end. The belt that changes length on the outsides in the Y axis look very straight and measure the same width and the ends just before they change direction. (as accurately as I can). Used

FxxToo

@msquared Thanks, I will check that out. Both motors sound good and when measuring the distance and repeating positions, it seems good.

MSquared

@fxxtoo Mine did not sound good, at all...in retrospect.

maybe some pictures of your belts / routing would help

FxxToo

@msquared I will try tonight to take some pics and post them..Thanks

FxxToo

@msquared Here is some pictures, I hope they help get to the bottom of this...
All comments are welcome...

whosrdaddy

maybe the photos are misleading but it seems that the belts coming from the motors are not aligned with the Y axis rails.

dc42

There is a good diagram that shows which belts must be parallel here http://forums.reprap.org/read.php?397,818906,818924#msg-818924.

FxxToo

@dc42 Thanks. I modeled this printer after the last one the Digital Dentist built. I laid a straight edge on the belt and the motor side is out about .6 millimeter. I haven't checked the other side yet. I hope that will fix this. I love the Duet and the 7" Panel. I am glad that I went with this system.

FxxToo

@whosrdaddy Thanks, It is off a bit on the motor side.

FxxToo

I had to set this aside because of work, but am back at this. I found a post where a guy was having the same issues as I was. https://forum.duet3d.com/topic/3688/corexy-setup-problems-with-movement
I tried what he did and changed the steps per mm on one axis and my problem went away. That was after taking every thing a part and redoing it. The rails on the bearings are parallel within .001" end to end. The X is 90 degrees to the Y, the belts are even and the movements are correct. So I changed M92 X320 Y320 , trying different setting and with M92 X320 Y319, the movement of the axis are correct, no more Y movement when moving just the X and vice versa. So barring a difference in a pulley, could the board have a timing issue like the guy in the link posted as DC42 stated? Help I am just trying to get this printer up and running