newb.. Heatbed and Printrboard Questions

I have the Printrboard Rev C and right now a MK1 heatbed. I built my machine a little bigger then specs on the wiki. Mechanicly its working fine but my MK1 heatbed/table is much smaller then the amount of travel I have. Are there any other heated bed options that will work like the MK1 plugged into the Printrboard?

the Mk1 (with my piece of glass) gives me a 203mm x 203mm bed. I have calculated that I could get a 255mm x 290mm bed in there.

For my Mendelmax, I'm using a silicon heating pad from McMaster-Carr (35765K31) and a solid state relay to allow a RAMPS1.4 to control the temperature. I have the pad under an aluminum plate with some pipe insulation to keep the heat where it's needed. Currently using self-adhesive PET from mcmaster on top of the plate.

> For my Mendelmax, I'm using a silicon heating pad
> from McMaster-Carr (35765K31)

Have you tried other heating methods? PCB or power resistors? How does it compare? I was turned off to the heating pad for cost reasons but if it really works better I might want to try it.

The heating pad heats up the bed really fast. I have a MK1 heatbed on a Prusa, takes about 5-8 minutes to heat up. The 9"x9" 810 watt/sq in pad takes about 20 seconds to get to 110C, now the waiting is for the hotend to heat up. The wattage is overkill for a heatbed, next time I may get the low wattage pad. I currently have the thermister on the bottom side of the pad, opposite of the aluminum plate, so the surface temp is around 93C. Temperature control is a must with this pad. I tested it before installing and the pad started smoking when the thermister lost contact with it.

I recommend a thermal cut out or a thermal fuse as well, otherwise a single point of failure might cause a fire.

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Good idea. Ordered one that opens at 167C, with an operating temp of 147C. A big enough margin, since the temp does overshoot by about 15C when heated the first time from room temp to 110C.