Quote Originally Posted by printbus View Post
That's a long time. For comparison, my hex hot end goes from room temp to 215 degrees in about 90 seconds and the 8-inch heat bed goes from room temp to 110 degrees in about eight minutes. Some suggestions on things to check -

  • Make sure the power supply output stays at 12V when the heat bed turns on
  • Make sure any screw terminals at the power supply and heat bed relay are tight
  • Make sure the heat bed thermistor is secured well to the bottom of the heat bed (no gap)
  • I'd try to make sure cardboard or other insulator you're using between the Y-bed and heat bed isn't pressing against the heat bed thermistor. If the insulator is touching the thermistor, the thermistor won't be properly reading the heat bed temperature. Cut a clearance hole in the insulator if required.


Beyond that, I'd suspect the gauge of the wiring used with the heat bed is on the small side, and you're not applying the power you could be to the heat bed. You could verify this by measuring what voltage is actually applied at the heat bed itself. Do you feel any of the heat bed wiring getting warm? That would be another sign of power being lost in the wiring. As I understand it, the 10-inch heat bed can draw as much as 18 amps. As heavy as 12-gauge wiring might be appropriate for that much current. Can you read the markings on the wires that came pre-attached to the heat bed? One thought would be to use at least the next larger size for the fixed wiring between the power supply and the heat bed relay where flexibility isn't important.

EDIT: I should probably note that my hex hot end is not running the original cartridge heater, aluminum block or thermistor. I use silicone heatsink compound on the cartridge, and my hot end aluminum block is insulated on all sides with kapton tape. My hot end warm up time may not be comparable to the usual config.
What I found out is that the wire I used from the PS to the relay is not the right gage. It was way hot, so I shut it down. I will make a run to Lowes tonight to get some 12gage wire. It was after I had posted this that I decided to check for loose wires and when I grab the wires coming in to the relay it was like "wow is that hot" Thankful nothing seems to have melted down.