Problem with printing with Ultimaker 2

[joe30 0]

My UM2 is playing up, the y axis is stepping off, originally I was thinking it was the stepper motor as I had one previously that began to seize and would mis step, but got some new replacements as my reconditioned one with new bearings was doing the same, but problem still there.
I then thought it way be the belts were getting slack, as a quick fix I fitted a little belt tensioner, but still the occasional problem.
Not only that but occasionally the Y axis motor will stop, head won’t home or move, switch off and back on and sometime it works but will after a period of time stop working, checked with spare motors just plug in and intermittent function.
So,
Is my main controller board dying on me and needs replacement, and if so any recommendations as to where from?

[gr5 2,235]

I usually call this "missed steps" but it can be a pulley that slips on the shaft, or a stepper that is skipping steps.  Is it a gradual shift as you move up the print?  Or are the large sudden shifts?

 

When you say "switch off and back on" please elaborate - is it that the other axes keep moving or does the entire printer stop and reboot?  Or does everything stop and it just sits there for a little while?

 

If you have one axis that stops it's almost never the stepper (despite your past experience).  Steppers are extremely simple and will probably last for decades.  

 

1) It could be that there is a lot of friction.  When the printer is idle push the print head around and see if the Y axis has significantly more friction.  If it does then you need to fix that.

 

2) It could be the stepper driver.  These drivers can partly fail where they just don't have all that much power.  But more likely it's another issue: they have heat sensors inside and if they get too hot they shutoff.  Usually just for a second or less because they cool again in milliseconds (I guess the sensor is right there on the semiconductor substrate).

 

Is the ambient air temperature higher than normal (UM headquarters is cold - they like it really cold there)?  Do you have a towel or something under your printer blocking airflow?  You could experiment by removing the larger bottom cover - it's only 2 to 4 screws (I forget but I've removed many many times) and then tilt the printer up with a book or something and use a small box fan or other type of fan to blow under there and it if heat is the issue it will preform so much better.

 

If you have a really old UM2 then it may have a spare stepper driver on for a second extruder (originally they hoped to do dual extrusion on UM2).  It's possible to update the firmware to use the spare driver and plug the Y axis into that channel.  Building the firmware is not a trivial process but I can point you to step by step instructions if you want to try that route.

 

Most UM2s sold in the last 3 years don't have the extra stepper.  It's easy to detect as it is quite a large chip and situated across from each of the corresponding stepper cable connectors.

[gr5 2,235]

By the way, 90% of the time when you are losing steps it is because the set screw on one of the pulleys isn't quite tight enough.  You might want to use a sharpie and mark the shaft and the pulley for the stepper pulley and the pulley it connects to (the two pulleys on the short belt).  Usually it's the hardest pulley to get to - the one on the stepper motor.  Then when the problem happens again you can check to see if the sharpie marks slipped or are still aligned okay.

 

But from your description I kind of ruled this issue out.  But I could easily be wrong and this might just be an issue where you need to tighten the hell out of that set screw.  You can push the head around which rotates the stepper and you can position that screw for easy axis without needing to take those little side covers off that hide the steppers (or you can remove the 2 or so screws that hold those covers in place).

[joe30 0]

Thankyou guys for these kind replies and for this such detailed information