My build plate is 800x800mm… So I would need about 9 of them, or to find bigger ones (but they are very expensive, since custom made).
Also, they are not flat (the spot where the wires are coming out is much thicker than the rest of the pad), so it would make leveling complicated.
Add a thick aluminum plate to the cost of 9 pads, it may be well over 200 Usd. I don’t really want to spend that kind of money just for a heating bed, that would be almost half the price of my whole machine!
That was the first thing I thought of, I even bought one 30×30 silicon pad a few month ago. In the end I thought it was too much cost and too much trouble to use it.
Keeping it flat would be a pain in the ass as well. The guys on the seemecnc forums ran into this issue as well. You need a fairly thick chunk of aluminum to keep the differential heating from warping the metal. Even the mic-6 ground aluminum plates would warp. One that I know is working uses three silicone pads to heat it. I think it’s half inch thick and around 18″ in diameter.