Copper print bed surface? (Page 2 of 2)

Pirvan, I'm sorry, I was rude and grumpy. I still think there's a lot to say about this topic and I ought to have posted in a more useful, contributing way.

My personal favorite setup, that I hope to eventually setup, is the following:

A rigid frame, probably something like a 6mm by 3mm frame of aluminum (those are alu "strips" in a rectangle). Then there needs to be a flat layer, and it needs some way of adjusting. So maybe it could be an insulative lightweight wood. Like balsa wood.  And then a layer of kapton-heater. It's kapton-tape with copper etched to it. the copper etching pattern could be made with a very mild bias towards the edges, so that it counters the effects of edge heat loss. and a magnetic attachment system adheres a 2mm glass layer on top of this kapton.

Some caveats: You probably want to limit how quickly the heater responds. Something like this could put some heat stresses on the glass if you just blast it on. But other than that, it's the best I have for a heater system.

In terms of your idea to add copper, I wasn't clear- will you be adding this *in addition* to the aluminum? Or are you adding it to replace the aluminum? The copper will draw temp from the heater to the surface of the copper faster. And it freely conduct not much differently than aluminum. But if you air flow on the copper the difference in conductivity and the greater importance that has in forced convection, might make it more difficult to reach a given max temp.

To be honest though, I've read through your posts and at this point am not 100% certain what the goal is.

Yes but the copper would warp just like the aluminum bed currently does right? Which is the reason why most people use glass correct on top of the aluminum bed correct? Would a piece of tempered or plate glass with the heat system attached underneath do the same thing while taking most of the warp out of it?

You can drill plate glass, you only need a diamond or tungsten carbide bit. Maybe go to a local glass shop and give them the dimensions along with seeing if they can drill the holes for you also. The glass shop would even bevel the sides, or sand them down for you so you wouldn't cut yourself. You can always adhere the heating element to the bottom with kapton tape. I would also see about making it a 4 hole leveling system. instead of a 3 hole leveling system. That would actually make the bed level out without any type of leaning, especially if your measurement come from the print head.

As for why copper would be bad:

Forget the technobabble from earlier, lets make it simple: Copper conducts. We know this. It is why it is preffered as a thermal conductor for PC heatsinks/water-coolers. It dissipates heat quickly. For us, this is bad. You say copper would heat up quicker but cool down slower. How does that work? It would cool down just as quickly as it heats up, and there my friends is the trick.

The reason why glass works good, and tile works better is becuase they are thermal insulators. They dont want to change temperature, either to heat up or cool down. And that is why they work, the cooling down takes much longer allowing the plastic to cool down evenly.

So the trick is to heat up our insulator faster. Our problem lies in the placement of the thermistor, and that our bed temperature control is defaulted to bang-bang. If our thermistor was placed as close to the surface of the print bed as possible with an adequate PID value set, then you could quickly heat up the bed with an over-powered heater.

This would require drilling through the bed material almost to the point of breaking the surface (aluminum easy, ceramic tough, glass near impossible).

Or instead of inductive heating you can try convection heating (heated AIR blown directly at the surface just like Stratsys).

What-ever. Your copper idea wont work the way you think it will, but dont trust me. Have fun experimenting.