Problem with heatbed not reaching temperature
After assembling my printer and tweaking the z offset by about 0.2mm the printer performed like a champ...for a couple of days anyways.
I thought it was taking longer and longer for the bed to get up to pla temperature of 55deg. last night it was taking about 20 minutes and only reaching 36deg. Tonight I had some time to look at it and realized that the bed was plenty warm, the thermistor was just not registering. I swapped the bed and hotend thermistors on the Rambo board and realized that the problem was with the buildplate thermistor. bending and wiggling the cables did nothing until I looked underneath. Doing so, I realized that the thermistor (thermocouple?) came loose from the buildplate. Pressing it against the buildplate confirmed that it was still working and I glued it back on with epoxy putty. The repair would have to wait till tomorrow to test, but I believe it will hold.
Have anyone else had similar problems? could the buildplate have suffered damage from overheating while the thermocouple was dangling?
I just have to add that I was pleasantly surprised by the quality of the prints it produced so far and hope the same holds when I start printing parts of my own design.
Re: Problem with heatbed not reaching temperature
Hi Pieter
I had this also, among a lot of other people. http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/thermistor-came-loose--t4387.html#p35491
I cannot notice that my heatbed have suffered from anything during the few days it had struggle with the temp issue.
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Gert
Re: Problem with heatbed not reaching temperature
...Pressing it against the buildplate confirmed that it was still working and I glued it back on with epoxy putty. ...
hmm... gluing the thermistor with epoxy is not the best solution. the thermistor is normally fixed with kapton tape underneath the heatbed, so that it has direct contact to the bed itself. epoxy is a very bad thermal conductor.... so it might be that after gluing the thermistor with epoxy, the measured temperature will be delayed severely. so if you've already used the epoxy, I would at least recommend to do a pid calibration for the heatbed, as described inside this thread (use the "M303 E-1 S100 C8" command to start the tuning and the "M304...." to store the determined values).
dem inscheniör is' nix zu schwör...
Re: Problem with heatbed not reaching temperature
Thank you for the comments.
There was no sign of any tape being used to hold the thermistor in place, though it is possible that it was lost when the printer was moved.
The epoxy I used is a metal-like putty and I assume it incorporates a metal filler that would help with thermal conductivity. I pushed the thermistor firmly against the build-plate and used a very small amount of putty over it to hold it in place. The thermal delay can not be that much different than what it was before, and the bed stabilize and hold temperature very well.
As far as I can tell, it is not broken enough to warrant any more fixing.
Again, I just have to say that I am mighty impressed with how this printer performs. Thank you Joseph and all who helped to make it possible!
P