Heat bed taking a long time

I've been having trouble getting my heatbed up to the right temps. Initially the problem seemed related to running the printer through Pronterface. Once I started printing directly from an SD Card, it was heating much quicker. Then I changed the settings so the bed would heat to 90 for the first layer and 100 for additional layers, seemed to do the trick. But yesterday after I was done calibrating the bed and the extruder, the heatbed started taking a long time to heat again. Right now I'm heating it and it's been 32 minutes and only at 85 degrees. I checked the wires, everything seems fine. The thermistor is insulated. I'm not sure what the problem could be unless the power supply isn't good enough or maybe I'm using the wrong electrical sockets?

I have a MakerFarm 6" i3 with the Magma Hot End and my power supply is the Antec ATX 12V, v2.3, 450 watts.


Thanks!!!!

Printing from Pronterface or from SD card shouldn't make a difference. Here are possible reasons:

1. Your power supply is probably not supplying enough current for the bed,
2. the resistance in your bed is too high and it's not getting enough power,
3. your leads are not big enough and adding too much resistance,
4. you have a poor connection somewhere.

Measure the +12V voltage at the power supply, at the power supply terminals to the controller, at the bed terminals on the controller, and at the bed terminals with the heater on. Be very careful not to short anything out!!!

1. If the 12V is too low at the power supply, then the power supply doesn't enough current output. Most printers with 200x200 mm heated bed require at least 18A of current.
2. If the voltage is fine at the power supply, but low at the +12V terminals at the controller, then your leads are either too thin or you have a bad connection.
3. If the PS voltage is fine, and there's a big drop in the voltage at the bed terminals on the controller, then you might have a problem in your controller.
4. If 1 and 2 are fine and theres a big drop in the voltage at the terminals on the bed, then your lead wires are too small or have a poor connection at the controller.
5. If the voltage at the bed is fine, then your heated bed might have too much resistance or you have poor contact there.

Yeah, I've been having problems getting the connections for the power supply to stay putin the Ramps board and that seems to be at least some of the issue. Whenever I re-insert the wires everything works great for a bit, then something starts sliding. Thinking about soldering the wires together (stranded wires) so they'll all fit.

I also ordered a heat relay and a new power supply.

Thanks!!!

You mention RAMPS - Swap out the 11A fuse (polyswitch) for a 15A then the MOSFET is too weak also so you need to get something with a better choice of MOSFET - IRLB3036PBF. They are under sized for the heated bed and are over heating. Once you finish this swap the board will be cooler and your heater more reliable.