UM3 picking wrong printcore

[maxhans 0]

To start off – I have been a huge fan of our UM3 at our office  since it has been working realiably and after getting to know the machine well it has only seldomly let us down.

 

We are running the latest firmware on the UM3 out our office. For the last couple of weeks it has a weird bug, where it uses the wrong printcore. We are usually only printing with the first printcore (the left one) in PLA and seldomly use the second one.

In the setup procedure before starting a print it selects the wrong printcore by moving the lever. This leads to the second (right) printcore being lower. It then starts printing by extruding out of the first printcore and keeps scratching the platter with the second one.

 

This has already ruined two of our buildtak platters. Also yesterday this lead to a huge blob of PLA accumulating around the nozzle and inside the printcore. The printcore is broken now since we had to cut it out of the printhead.

This bug has turned from  an annoyance at first into a major problem and the printer is shut down until there is a fix.

 

I searched around the forums, but have not found a solution. Is this a configuration mistake, a bug in cura or in the firmware?

[Smithy 1,146]

Strange issue, never have seen or heard it before, that the printer switches to the 2nd core and extrudes through the first one.

One idea, can you check if the switch is correctly calibrated? There is a menu option to setup the calibration or to check if it is ok. Maybe your lever don't fit exactly into the gap on the right side and therefore it switches to the wrong core.

[maxhans 0]

Funnily i found that option yesterday in the menu. Switching the printcores has worked fine before, so the lever position should already be set correctly. Nonetheless I did that calibration thing and I will report if it helped!

 

[maxhans 0]

Okay so this issue seems to be resolved at least for the first print. It usually occured for the first print when I switched the printer on.

 

(Probably not?) directly related to this: I replaced the broken printcore and relevelled the bed manually and with the automatic levelling twice. however the first 2-3 layers are way too close to the bed (or rather underneath) which leads to the first layers just scratching the surface. I have a (black) buildtak surface glued to the glass buildplate and did the levelling with the surface on. Do you have any ideas?

[Smithy 1,146]

1 hour ago, maxhans said:

I have a (black) buildtak surface glued to the glass buildplate and did the levelling with the surface on. Do you have any ideas?

Buildtak is not working properly with the active leveling, so turn off active leveling completely and relevel after that manually again. It is important to relevel again manually, otherwise the already saved values from active leveling will still be used.