X will not move when homing  

RE: X will not move when homing

Posted by: @lexington23

I have been trying to solve this one for 2 days now.  It's doing my head in.  Here are the important points.

I can move X freely with my hand, all the way left and right with no resistance.

When I run the wizard X check fails, X will only twitch slightly and then it wont move.

If I auto home X it will twitch and then set the home in that spot.  I can move the x axis freely and put it anywhere I want to and auto home will twitch it and set home in the spot that I placed it.

If i move the X to home position manually and then start a print it will print normally with home set in the correct place.  If i start a print with X in any other position then the home will be there and it will ruin the print.

If i move X using the manual controls it will move freely all the way left and right.

Please help I am completely out of ideas on how to fix this.  Thank you

Hello and welcome in Prusaforum!

I don't own a Mini but:

i would first check the complete mechanics of the X-axis (belt, pulley, linear bearing, screws...). Are the bearings greased, all plugs correctly and firmly connected to the printerboard, no short circuits or loose contacts?
If the mechanics fit, everything runs smoothly and all electrical contacts are o.k. i would contact the prusachat (login with your account and select eshop), maybe the printerboard could have a tilt.

Good luck!

RE: X will not move when homing

Interesting, I had similar occurrences with Y-axis at the beginning of the print when printer was supposed to home and start MBL in starter gcode. It happened only twice and resolved on its own though. Are you saying if you move stepper motors from the menu, they move freely? If support cannot diagnose it properly and you are sure mechanically it's OK, I'd open issue on GitHub.

RE: X will not move when homing

I worked with it more last night.  Here is some net info.  It gets stranger and stranger.

I ran the wizard several times in a row.  X always twitches and fails.  I had Y fail two times in the same way.  The platform would twitch and then fail the test.  I even had Z fail one time.  The I run it again and they move normally.

I manually placed all axes to their home location and then started a print.  Everything had the correct home even though X acted strangely.  The print was a success.  It was a three hour print and it had no issues and the quality was excellent.  If i don't manually place X at home and I start a print then it will set home at that spot and spoil the print.

At this point I am thinking that there is no way that it's a loose grub screw or an obstruction or anything like that.  I guess I can use it as-is but I will always have to manually home it before starting.

Anyone have any ideas what I can do?  I've never used github before but perhaps I really should file and issue.

RE: X will not move when homing

Did you Lube the Linear bearings? 

https://help.prusa3d.com/en/article/i3-printers-regular-maintenance_2072#rods-and-bearings

regards Joan

RE: X will not move when homing

@joantabb

I have noticed that compared to MK3S, MINI bearings came very well greased already. I guess this is taken care of during assembly. This does not exclude possibility that OP's bearings are dried, or cables are loose, or even rods are not parallel. 

@lexington23

I suggest contacting support via their chat, you can find Live Chat widget at the bottom of Shot page after you log into your account there. It can be mechanical issue, or it could be bad main board. MINI relies on sensorless homing, meaning it detects end of axes when motor reports back it cannot move further (crash). It could very well be that initial resistance for carriage to start moving is high for whatever reason, motor detects it as crash, and firmware concludes it's at the end of axis, causing this weird behaviour. I think this is what happened with my Y axis fail.

Github is pretty simple to use in your case, you just need an account and you can open issue. Here's a list of issues for MINI reported by people: https://github.com/prusa3d/Prusa-Firmware-Buddy/issues  

RE: X will not move when homing

@joantabb

It's not lubrication.  The printer is new and everything came very well lubed.  It's not obstruction or loose grub screw either.

RE: X will not move when homing

I have completed several prints successfully at this point.  I have to manually place X in the home position before I start the print but after that it will work.  Also I have noticed that mesh bed leveling is not working correctly.  X will stop in random spots and then check the level as if everything is working normally.  The result is that the bed is not truly leveled.  I have mostly been printing single figures so this is not a big problem either.  However, if I want to print something larger I cannot because it almost never completes the leveling process properly.  It doesn't fail in a consistant manor either.  It just randomly stops short and then checks the level in that spot.  Does anyone have any ideas?  I am really stumped here.

RE: X will not move when homing

I need some times to press auto home 2 times (one after the other) to be convinced that it will be fine. Some times, only the 2nd time is really "homing" 

RE: X will not move when homing

What you are reporting could be most anything. But common issues are: 

• improper assembly, cable not plugged in
• improper assembly, crimped/damaged cable
• improper assembly, loose drive gear / loose belt
• improper assembly, crushed bearing
• defective motor
• defective motor driver
• ...

As for homing, stray cable ties, improperly routed cables, crushed bearings, dry bearings, among other causes.

ps: Prusa doesn't lubricate anything ... the user must do that.

RE: X will not move when homing

@tim-m30

I've read elsewhere on the forum that the bearings on the Mini have better lubrication from the factory than the mK3 etc. is this not your experience? 

RE: X will not move when homing

@tim-m30

Your MINI came without bearings lubricated? Mine had small amount of grease overflowing on rods and Z bearing was bubbling with grease when moving.

RE: X will not move when homing

Ugh, the X-Axis on my mini has been nothing but trouble.  First I had a belt and loose pulley issue, but after I replaced the belt and tightened up the pulley, I've been printing successfully for a week.

Now I'm having the X-Axis issue described int he first post.  I thinks x-axis:180 is either in the middle of the bed or all the way to the left.

Self-test fails on the x-axis after moving a few inches when I run it. 

Mesh bed leveling does not work since it only tests the right side of the bed if I move the x-axis all the way to the right manually.

RE: X will not move when homing

Well.... I disassembled everything, and it all looked ok.  I re-assembled it and now everything is working again.  Go figure.

RE: X will not move when homing

I had something similar to this that was actually intermittent. I would have prints fail midway looking like skipped steps but I would not hear anything, I would try to move the axis manually with the steppers turned off and I had significant resistance one way but none the other. It would fail to home and bed level because it would not move one way. I came back to it the next day and it moved fine and I had a few successful prints before it would show up again. 

I eventually figured out it was one of the linear bearing seals had somehow been damaged(I haven't figured out how but I don't discount something that I did) so it would sort of cave in one way and cause resistance, I replaced the bearing and have not had troubles since.

Hopefully this helps:) I have pictures and videos of the issue as well if anyone comes across a similar issue.

-Nick 

RE: X will not move when homing

I have this exact same issue.  I removed the stepper motor and found play in the rod, it would click up and down. I would rotate it 180 degrees and it would click left and right.  If I put any sort of tension on the belt it would bind and "reset: the home position.  I would then have to home all the way to the left to reset it and able to home right.  When Mesh Bed Leveling start it binds up and things the home is in the center.  With the belt remove the carriage moves smoothly and i confirmed there was no binding due to a print or alignment.

90% its a bad  X Axis Stepper.