I think you're right. My bad. Thanks

But now that I have it up and running again, at least as a single extruder machine, I'm going to hold off fiddling until my son finishes printing some critical robot pieces for the FTC world championships next week.

I just installed the dual head and now the z axis doesn't work. The bed only goes down, when it tries to go up it goes down instead.

It seems to be something to do with the second extruder motor. If I unplug the cable for the new second motor, it works fine again.

That's what I was thinking too. Does anyone have something to share?

Picture of the "fix"... (apologies for poor phone camera picture)

Are you going to be running a PC off it too? If so, you'll probably need a bigger UPS.

Even if you aren't, that might be cutting it a bit fine. A 600VA UPS is only good for around 300W which is roughly what people here have measured the M2 taking at full load.

I found another problem this weekend that can cause the extruder to fail. My filament guide tube was not dead vertical where it entered the extruder drive housing. As a result the filament started wearing a groove in the side of the entry hole of the drive housing. Over time this got to the point wh...

I think the only thing in common with the failed prints is either overhangs that curled up or edges that curled up due to insufficient bonding to the glass. Which would suggest that the slippage is due to the head catching on the print and the X-axis motor unable to overcome the resistance.

After seeing you guys' replies I went back and double checked the extruder motor mount and it was a little bit loose. However after tightening it up I did another print (nothing else changed) and it STILL went wrong after about 30 layers.

Every print is different, even though it's the exact same model.

My suspicion is something is slipping in the x-axis drive train during high speed head moves. I'm going to try slowing down the head speed for the next print.

Recently my M2 seems to have started developing an x-axis problem. It only happens on certain prints and looks like it is related to what model and what part of the model it is printing. Nothing seems to be loose. Could it be belt skip? Or the x-axis steeper motor missing steps?