Heat bed temperature drop
I observed a strange behaviour of the heat bed temperature. As an example I mention here printing a benchy with Prusament PETG (orange) and using the system preset print file:
Heated temp for 1st layer is 85 C. After this it will raise to 90 C: temperature was reached after ~1 min of the change. Then the temperature dropped to 86 C within ~4 min. Then started to raise again to 90 C within ~5 min. The bed temperature keeps then stable for the rest of the print. More pronounced is this effect when printing nylon or PC. Consequence is, that I observed warping with these filaments and also with PETG when printing larger objects. Increasing the temperature using tune will give a preheat error (code 26201).
I contacted support and received a replacement for the heat bed. Too badly, this didn't make any difference.
Any ideas what may be the cause?
Printer MK4S kit (1 year old). Firmware 6.2.0 (newest).
RE: Heat bed temperature drop
Hi,
I experience the same when printing a temp tower, close to the middle of the sheet. The temperature drops more then 10 degrees and i get an error. When i measusre the temp around the object with an ir thermometer i measure the board is way above the set value. My analysis is that the ventilator cools the spot above the temp sensor way to good. I tested by decreasing the rpm of the vent. and the indicated temp went up again. I have no solution yet. maybe install more temp sensors on more places under the bed? anoying....
RE: Heat bed temperature drop
Hi pa3cw.
Many thanks for sharing your experiences. Based on your findings, I made two additional test prints with PETG:
- moved benchy to the front-left corner (far away from the thermistor).
- disabled the cooling print fan and printing benchy in the middle of the bed, where I've seen the highest temperature drop.
In both cases the heat bed temperature changed less than 0.2 C, which is absolutely fine.
Conclusion: It may not have been worth to upgrade from MK4 to MK4S, because the print fan on the MK4S is much more powerful for enabling higher print speeds. I'm considering to moving back to the MK4 extruder design.