heatbed not going past 80
January 31, 2020 10:23AM
I have my p3steel (with ramps1.4) since 3 or 4 years ago, and have always printed with the heatbed at 90C at most, mainly printing abs. A month ago I decided to test printing some abs with the bed at 100C and did a couple prints without any problem, but after that the heatbed struggles to even get past 80-85C.
after reading some post here and in other places, this is what I have done to try to find the culprit: disconnected the printer, and measured with multimeter the resistance between the heatbed pads. it shows 1.2 ohms (if I just touch the multimeter probes together, it shows 0.2, so I guess the real measurement of the heatbed must be around 1ohm?) so I guess the bed is ok.
Then I connected the printer and heated the bed. I measure voltage with one multimeter's probe on the bed + pad, and the other probe on the - input connector on the ramps (the one coming from the power supply), it shows around 12v, BUT if I do the same with the negative probe on the - pad of the heatbed (instead of in the - connector from the power supply), it shows much less, around 6-7V. (also if I measure in the - connector on the ramps (the one going to the bed) it shows the same 6-7v. So apparently the problem is not on the cables).

So with this data... should I blame the mosfet? I have got a new ramps1.4 board and will just replace it, but would like to know your opinions about it...
Re: heatbed not going past 80
January 31, 2020 02:14PM
If you're reading 6-7V at the heater and 12V at the power supply, something in between them is dropping 5V at several amps and should be getting pretty hot. Check temperature at connectors. Tighten screws at connectors.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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