If you want to print larger PLA objects or ABS you need a heated print bed.

• Josef Průša designed the original PCB heat bed for the RepRap Prusa Mendel - see PCB Heatbed.

We have made a few minor updates with the MK2 boards, allowing through hole components and through hole wire connections, a hole for a thermistor through the centre of the PCB and putting the silkscreen on both sides.

New Mk2a has further improvements including bigger cable holes and solder pads, and another mounting hole centrally located on the cable edge. This allows 3-point mounting for easier bed levelling.

• For more information check out the RepRap wiki: PCB Heatbed MK2

To ensure even heat distribution, these boards are produced by directly etching 35um copper; no copper plating is carried out - see Josef Průša's warning about plated beds on the Wiki - PCB_Heatbed - WARNING. The boards are all individually tested to confirm even heat distribution and correct resistance. Henrik Akerstedt's YouTube video shows one of our heatbeds warming up in infra-red: see RepRap PCB Build Platform heating up.

• The MK2 board has identical dimensions to the MK1 board and is designed to be mounted under glass; check out Prusa's mounting instructions:PCB Heatbed Mounting Instructions. There are pads and unplated through holes for connecting the power wires. Ensure that the wire you use is thick enough for 10A, and solder it to the pads on the track side of the PCB. It is a good idea to think about strain relief so your moving build platform does not flex the joint, which can lead to failure of the joint over time. We recommend routing the wire from the heated bed to strain relief on the supporting sheet before routing it to your controller/power supply.

You will need the following to mount the board (not supplied):

• 20x20cm glass sheet, 3mm or 2mm (you can print directly to the back side of the board but no PCB is perfectly flat)
• 4 bulldog clips
• Nylon Washers, Cork washers or your preferred insulated stand offs
• 4 M3 machine screws nuts and washers

You will need the following to power the board:-

• 11A+ 12V power supply, either through your RepRap power supply or from a separate supply. The boards generally draw up to 12 amps briefly when starting from cold, and this falls to 9-10 amps at 60C (PLA operating temperature) and 8-9 amps at 110C (ABS temperature)

• Thick cables: minimum 1.0 sq.mm recommended.

IMPORTANT

• If you are powering the heatbed using the PWR2/BED MOSFET on a Sanguinololu controller, then you must divide the cable strands in two at the controller connector so as to use all 4 pins on the MOLEX connector - Pins 1 & 2 are 12V, pins 3 & 4 ground. This is to comply with the power rating of the MOLEX connector which could otherwise overheat. It is also strongly recommended to use a heatsink on the PWR2/BED MOSFET. Similar precautions against overloading/overheating should be taken with other controllers.

The following items are recommended:

• A 500 Ohm to 1K Ohm resistor and one or two LEDS
• PET Heat Resistant Table/ Kapton Tape for adhesion to the print surface.
• A thermistor/thermocouple to measure board temperature.