MAXTEMP error but no shorts. Might it be to electromagnetic field?
Hi,
I just assembled my MK2 few days ago, but it did not last long before I got a big issue. I was able to do some prints of small (< 5x5cm) objects. The few prints were of an amazing quality right from the beginning.
At some point the printer started to issue an alarm for hotend temperature treshold (> 500⁰C), like when a short occurs on the sensor wires, but this happened only when the printer head was reaching the right side (opposite of the electronics).
So, I checked the temperature sensor, and there was no short on this side. (But see remark below about that 🙁 )
I then checked in the electronic box (the black box with the board and all the wires) and everything looked fine. The wires were all tied with a zip-tie, firmly enough but without excess.
I noticed that slightly moving the wire spiral up and down triggered the alarm too. I tried to repeat it by holding either ends of the wires set to make sure this was not moving here (either on hot-end side, or electronics side), but the alarm triggered again just by moving the spiral.
So I thought that even if unlikely there was a short somewhere in the middle of the wire. I removed the spiral around the wires and the zip tie on the electronics side, and then tried to repeat the issue again.. But curiously, I was unable to cause it again. I can move the wire all the way I want, or move the head to either side of the frame, and everything works as expected. Heating the hot-end behaves as expected (reaching 50⁰C rapidly, and triggering the fan.)
So I'm wondering.. Can it be explained by the sensor wires being close of some other wires causing something like a current due to electromagnetic field? (within the spiral, or -likely- within the electronic enclosure).
Unfortunately, to diagnose that I had to look closely at the sensor and I think I've somewhat damaged it by pulling the insulation a bit too much on both wire 🙁 Sadly everything is working fine now (with the spiral removed) but since the sensor is no longer pristine, do I need to buy a replacement part?
Here is the damage I made: (I'm not used to perform such things)
Is it not recommended to use the printer in this state?
Re: MAXTEMP error but no shorts. Might it be to electromagnetic field?
While trying to put back the spiral on the wires, I got the error again (the printer was kept on on purpose). I'm no longer sure it was caused by electromagnetic field. It looks more like there was a defect somewhere. However it printed fine several objects without any issues at all. And we followed assembling instructions very closely.
So I guess I've no choice but to change the hot-end.. after only 2 days of using it. I'm disappointed. Maybe it's my fault, I don't know.
Can I change only the thermistor?
Re: MAXTEMP error but no shorts. Might it be to electromagnetic field?
Yes you can change just the thermistor. i don't have a MK2 but using the Prusa assembly instructions in reverse will let you safely dissasemble the assembly. I have linked the part and the official E3D assembly instructions for the hotend. If you are located in the US then use the list of authorized resellers. Saves time in shipping.
Re: MAXTEMP error but no shorts. Might it be to electromagnetic field?
Thanks for the link. I ordered one.
In the meantime I disassembled the head to check the wires, and it was rather easy (easier than with the MK1) which is great.
Regarding the wires, maybe the heatshrink (too much heat) or the ziptie (too tight) around it was not perfectly assembled. Anyway after putting everything back, the printer is working again — so far. But I will change the sensor anyway.