[Solved] Help please - Y Axis Length self test failure and Home position failure  

RE: Help please - Y Axis Length self test failure and Home position failure

Should have added, have also checked motor mount, gearing and idler.  All firmly fixed and free running and doesn't seem to jump teeth.

I can't see it now as failing the self test but the belt tension was over 210 but can't remember the exact figure.  Wondering if this is too slack but then it worked at least half a dozen times for the first layer calibrations.

RE: Help please - Y Axis Length self test failure and Home position failure

Posted by: @lizridley

I'm a first time novice.  I built the kit, self test, calibrated and had a few goes at the first layer calibration and all was OK.  I found the first layer calibration a bit tricky as I didn't really know how much movement it needed but getting my eye down level with it gave me a good indication that it was quite a bit higher than it should.  I also downloaded and installed the latest firmware.

During the calibration I am getting say 1cm of drop or from the nozzle which didn't always clear properly on the first wipe so I raised the X axis from the settings and heated the nozzle and cleaned it off with some cardboard before doing another first layer calibration.  Something I was going to look into to see if I could improve and not the problem at the moment.

Then it didn't return to home but I've now been fiddling about so much I'm not sure when it was first a problem.  I think it was when pressed the stop X button during one of the first layer calibration. I moved the axis from settings and had another go, it seemed to go fine and I made a final change to the first layer height.

I then tried printing the tree frog from the SD card and it started off but didn't complete the first layer. Not really knowing what to expect I was wondering if something was wrong as it started the wipe in the middle of the bed and continued to print near that and then further back on the bed.  The Y axis made a clatter but it continued, then it clattered more and I pressed the stop button.  Again the head stopped in position where I pressed stop.  I checked the last print and it had recorded 6 crashes.  I tried moving the bed from the settings but it only had 0 to -4 and hardly moved.

I read up a bit about the Y axis and wondered if I had over tightened the bearings so dismantled, inspected bearings and they are fine and added lubricant (I had followed instructions and not lubricated on first assembly).  Ran self test again and it only moves the bed about an inch before failing due to Y axis length.  There is nothing blocking or jamming it.  I turned the printer off and moved the bed by hand to see if it would work from a different starting point, it did the same.

Can someone please point me in the direction of what it wrong?  Its somewhat disappointing spending ages fiddling with it and not having got as far as printing anything and now it won't work at all.

Also, I've been using the settings menu to move the axis (extruder and bed) when it stops in the wrong place or is that a problem too?

Thanks

 

I think you have a mechanical problem. on these pages you may find helpful tips for your problem: https://help.prusa3d.com/en/article/selftest-mk3-and-mk3s_2045

RE: Help please - Y Axis Length self test failure and Home position failure

An update for anyone who reads this with a similar problem.

I contacted support through the online chat and they were very helpful and immediately suggested I loosen the Y axis belt.

They are now:

X axis 255

Y axis 245

I will recalibrate and give the printing a go shortly but the self test has passed.

The lower the number the tighter the belt is and I thought the other way round and that the belt was surely tight enough!  I'll see how I get on and could slacken off a little.

Lesson 1 of 3D printing learned 😀 

RE: Help please - Y Axis Length self test failure and Home position failure

@lizridley

Thanks for the feedback, glad you were able to solve the problem.

The MK3 has no more limit switches and controls the homing via the current consumption of the trinamic drivers. If the belt is too tight, the drivers need more current and think they have reached the homing position. This could happen at any position. Right belt tension is very important.