How to make a heated bed with pcb by myself??

Now I want to make my own heated bed with pcb but I have a question. How to add the heater strip in the pcb with exact value of resistance and layout?

Use a scrap piece of PCB and cut some traces on it with a knife from end to end in some nominal width say 1/4". Make a cut from one end to the other stopping short by the same amount. Then step over and make a cut in the other direction again stopping the same distance from the end producing a zig zag trace with enough length to measure the resistance with an ohmmeter. Then use ohms law E(voltage)= I(current) X R(resistance) and Power = E x I for this sample. Making it twice as wide will make the current twice as much and the power twice as much for the same length. Making the trace twice as long will make the resistance twice as much and cut the power in half. Work from there, you'll get a good basic education in resistance and DC power.

In theory you can calculate trace width and length using a formula, the details are here [circuitcalculator.com] How well thats works in practice for a heated bed I don't know, but I suspect some trial and error would be needed to get desired result.

As for drawing the tracks, I think you have to do that the hard way, although I would be tempted to write some sort of script to do it.

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You can also use a aluminium bed which you can heat up with a hair dryer on max heat setting.

Why not just use a can of Sterno under the aluminum plate, like they use at hotel buffets to keep the food trays warm?????

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vreihen
Why not just use a can of Sterno under the aluminum plate, like they use at hotel buffets to keep the food trays warm?????

you would have a melted print because the sterno burns way beyond the the melting temp of the pla/abs

Use strip board. Soldering the ends together you can make a trace that zigzags across the board. It works well enough for me, was cheap as chips and is really light! (you might need to solder tracks in parallel to get the resistance down.)