Can a heatbed PCB (Prusa Mk2) be straightened out?
I have a really bent heatbed PCB, the middle is elevated about 3 mm with respect to all edges.
I have found this thread Warped PCBs, where a heating method is applied by baking a PCB in the oven, as described here: 3.2 Bow and Twist Repair.
Can this help straightening out a Prusa heatbed PCB? If so, can I apply the heat by the heatbed itself, or do I need to utilize an oven? Will the pressure from the strongly clamped glass plate be enough or will the glass break at these temperatures (given that the heatbed can reach them).
Baking PCB in an oven is not a good idea, I would say. I know PCBs are resistive to the heat (especially heatbeds) but, still, it sounds odd. But the real question is how baking would help. Let's leave it.
If your heatbed is such bent you can do few things depending on your situation/environment.
You can:
- Add two glass plates (at the bottom and at the top) and clip them all together;
- Support your HB with flat aluminium or even wood;
- Add an aluminium frame, or;
- If you use glass plate, clip the HB to the glass using stronger (wider) clips.
Ad#1 the thermistor can even stay sandwiched between the PCB and the bottom glass plate.
Ad#2 If your HB is bent up in the middle, you can use the middle thermistor hole. Drill it a bit with fi8mm drill (but not too much, I would say halfway through) and use a cone head screw to screw it flat on to the aluminium/wood support. Of course you will have to install a thermistor into the new place.
The simplest, and less destructive, solution is #1 and I would recommend that.
Some feedback after some time, without using the heatbed too much. The bend didn't go away so far, but with the bulldog clips I use now (it was a weird temporary solution before), the bed straightens out enough under the glass sheet. This solution is good enough for me. I will report if the glass suffers a total loss at some point.
While the suggestions in the answer are OK, the premise (that "Backing PCB in an oven is not a good idea") is factually wrong, given that is exactly as PCB are manufactured, and how they are fixed when surface mounted components become loose. In fact you can most definitively use heat to straighten up a PCB, see this other answer: https://3dprinting.stackexchange.com/a/5682/9134
Agree with Mac on this. PCB heat beds are essentially PCBs and they can be put in ovens, baked at lower temps (say around 100 deg C) and can withstand temperatures up to 240 deg C (for less than 30s). That’s is how components are soldered to the PCB. This of course requires a reflow oven or a temperature controlled skillet.
AFAIK the question was - "could HB be straightened out ?" I did answer how it can be straightened out and in the first sentence I did mention that PCBs are heat resistive. I also asked how baking could help to straighten it out if his HB did bend after making it hot so how it could go the opposite with the same action? I don't see ANY reason to downvote.
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Content dated before 7/24/2021 11:53 AM
kamuro 6 years ago
Some feedback after some time, without using the heatbed too much. The bend didn't go away so far, but with the bulldog clips I use now (it was a weird temporary solution before), the bed straightens out enough under the glass sheet. This solution is good enough for me. I will report if the glass suffers a total loss at some point.