Two colleagues who know the um2+c tell me you probably have a "bad mainboard".
I just don't know the um2+c very well. If you are competent with a soldering iron and multimeters I can offer some advice but if not I probably can't help you.
I don't know if the 700C is the goal temp (in which case maybe that's just a normal profile temp from cura) or (more likely) if it really thinks that is the current temp. If it really thinks that is the current temp then you might just have an open in your temp sensor wire. I don't know where that temp sensor would be located. It's possible the printer is refusing to move any steppers while the internal temp is over some threshold. Say 50C. I know 80C air temp is hot enough to damage the steppers.
So it could be something very simple (loose wire to the temp "build volume" temp sensor).
I didn't even know the UM2+C had an air manager so I really don't know this printer very well.
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gr5 2,224
You should contact your reseller.
So the steppers and the heaters run off 24V. Everything else is lower voltage. Losing 24V intermittently could be a firmware feature (maybe it sees crazy values on the sensors due to damage and so disables everything), or it could be a hardware issue that I'm familiar with.
If it's a firmware issue you can probably see something about it in the log file? Something like "bad temp sensor value" followed by "disabling 24v" or "disabling heaters and steppers". Just a guess. You could also concentrate on print head temp sensor since it sounds like you may have damaged it - they are a bit delicate. Before heating anything up, go through the menu system to control it manually and see what temp it is reading. It should read at room temp (I assume around 20C). If it reads say -100C, 0C 300C, or just "error" then you should concentrate on this. I'd replace the sensor. They are the most expensive part in the print head at around $25. You can get them from UM resellers or from 3dsolex.com (same part as for UM2).
Anyway I want to talk about the hardware issue. I've never seen the underside of a um2+c but I have a UM2, UM3, and an S5. They all have a variation on this board shown below. It controls the steppers and the heaters. See that big blue box there? That's the relay that allows 24V to flow to the stepper drivers and the heater switches. You could give that a rap or assuming you only have access to the other side you could tap that corner of the PCB with a very fast, but low energy tap. Like with a wooden spoon knocking quietly on a pan.
That relay is known to fail intermittently and you can bypass it with a jumper as it isn't really needed.
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ruttger 0
Thank you for your extended response.
About the sensors, the heat sensor measures 29°C (which could be right because the outside weather is quite warm). Also when I warm it up with a heat gun, it measures higher temperatures, so it seems to work.
But what I saw in the diagnostics screen might be more interesting: the build volume temperature is 700°C (see photo). Which seems extremely high? I don't know what the 'build volume temperature' means, is that the build plate?
Would that mean I need to look into something else?
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