ultimaker 2+ with y-axis stability issue.

[richardy 0]

Hi,

Our Ultimaker 2+ seems to be having Y-axis stability issues (see attached images). Initially I thought it was the print moving on the bed but that is not the case and the bed plate itself and glass seems secure so I thought it might have been loose drive belts  or pullies but these all look pretty tight to me.

 

Any ideas.

 

Any help is much appreciated.

 

Cheers.

[richardy 0]

Update.

 

I have had a closer look at the machine while it has been printing hoping to “catch” it when moves to a different position  and I have found that it is not to do with the XY axis – the issue seems to be stemming from the Z-axis; what seems to be happening is that it initially prints a few layers (10 – 15) correctly then the nozzle starts hitting the object being printed (very similar to when an object starts lifting off the bed due to lack of adhesion, although this is not the case) then all subsequent layers get hit harder and harder until it forces one of the XY stepper motors to miss a step (or more) so it moves to  slightly new position and then will print the next few layers correctly until the situation repeats – very odd and very annoying. The layers don’t seem to be delaminating so that is not the problem either. The only thing that I have changed since it was last running fine (apart from not being used for a few months) is that I am using a different internal fill pattern (cubic subdivision) although I don’t know how that would have any effect. The problem does seem to be getting worse though.

 

This almost seems like a gcode/firmware issue or maybe a problem with the z-stepper motor stepping to a certain point then not stepping any  more (loose grub screw on collar??)

 

Any help with this is much appreciated.

 

Cheers.

[gr5 2,234]

So for parts with say 45 degree overhangs - imagine the prow of a boat - where the outer wall is tilted outward at the tip of the bow.  On parts like that you get raised edges - as it prints the tip of the bow the plastic is still hot and pulling like a liquid rubber band and it pulls the tip up and later the nozzle can hit that as it can stick up a full mm sometimes.  It hits it HARD.  But if you do everything right the part should stay on the bed and the steppers should still not lose a step.  I mean it's like you can hit that part with your hand hard enough to slide the printer a few cm - that hard (it doesn't slide of course is the head is pushing one way and the bed is pushing back).

 

So:

1) Even if it hits quite hard it shouldn't lose steps.

2) You don't have any overhangs in that part at all - so I don't know why it would hit.  Unless you are printing the infill quite fast - say 70mm/sec or faster?  Yes changing the infill pattern could do this but the basic problem of hitting infill has more to do with printing too fast and with not enough cooling (fan - you can never have too much fan with PLA - you could add a desk fan or something blowing air into the printer).

 

So maybe slow down the infill but even so, your printer can do better.  Tighten the hell out of the 2 set screws on the short belt on the Y axis.  If you have a long hex driver you don't have to remove the cover.  If you don't have a long hex driver you will have to remove that corner cover (2 screws I think) to get at the stepper.  You might even have to remove the stepper.  But this is worth the trouble.