Build a 3D printer - Part 9: Heated bed
For the 3D prints to be able to stick to the printing bed, it needs to be heated. For this purpose we need to add a heated bed to our printer.
The heated bed that is used for the Reprap printer is an open source design by Josef Prusa. There are various versions of this board and the designs are freely avaiable to download. The two that are mostly used are the MK2 and MK2B versions. The difference between them is that the MK2 has a single layer of copper and the MK2B is dubble sided. The schematics for the MK2 is avaiable in Eagle format and the MK2B files are made in Altium Designer. Theoretically it is possible to develop the heatbed PCB yourself, but we will not do that here. You can buy the heated bed already soldered with required components and it comes together with thermistor and cables, ready to be installed.
The only thing that you need to do yourself is to tape the thermistor together with the cable on the board, just like on the picture above. For that purpose you will need 50 mm kapton tape. Notice that the thermistor is put in a small hole that is pre-drilled on the board.
This is how it looks on the other side of the board with the thermistor in place.
The are various methods to mount the headbed. In our case we will need:
- 4x springs 1.2 mm x 20 mm
- 4x M3 x 30 mm
- 8x M3 9mm washers
- 4x M3 screw nuts
Attach the spring to the PCB heatbed like in the picture below. Note that the M3 x 9 mm washer goes on top and on the bottom of the board.
Fot the print surface you will need a borosilicate glass with the dimensions 213 mm x 200 mm x 3 mm. Place it on top of the heatbed.
If you are going to print with PLA, you can cover the glass with tesa masking tape. I did not try other brands, but I know that this one works well and the 3D print will stay attached. For printing ABS you can use kapton tape.
Glue the tape in 4 banners on the glass and make sure you leave no gaps between the rows.
The final step is to make sure that the glass will not move. You can use binder clips to secure it in place. They come in all shapes and colors.
I liked the "see through" clips and placed two in front and two in the back of the bed.