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I have a new 12" MakerFarm printer (RUMBA with bed heater relay) and found that when the bed heater is on, the print quality goes down. Have checked the power supply, cable size, etc. The moment the bed heater turn on the extrusion goes thinner and does not lay down well. Input voltage is 12.32, drops to 12.28 when the heater is on. I'm thinking the electronics (RUMBA) has a problem, but looking for advice before I buy a new board.
Welcome to the bowing problem I had. The heater actually starts to fluctuate as the temperature drops and raises during prints. I first attempted to solve the problem by using a large 3mm borosilicate glass plate which did help with the problem but I also had cold spots towards the edges. Currently I am running a 300x300mm heater mat glued to a .1" piece of aluminum and the 3mm borosilicate glass on top of that. This resolved my z banding problem, using aluminum standoffs helped with the ringing as well. Heat up times are longer but the glass gets hot evenly and stays very hot. If I were to do it again I would look into a heater mat powered by AC instead of DC for faster heatup times and less stress on the power supply.
Could you explain the AC mat a bit? How does the Rumba control the temps? Also, where did you ge the aluminum and the mat you are using currently? I have been thinking the 30amp power supply can't cope with the power needs of such a big heat bed and extruder.