Tomorrow I will order an aluminum sheet to make a heated bed for my 3d printer (Ø430), I was thinking to order a 8mm sheet but wonder now if it’s not too much…can someone advice me?
I will glue a Ø400 silicon path that I get from @MakerGal (good advice and fast deliver).
Thanks.
I think 4mm its enough, 8mm its too much aluminum to heat
@MakerGal Thanks, I have already a 3mm one and it seems weak, I wonder if 4mm will not be the same…
Michael talk with @Darkberg_Aryavis have similar issues 
sorry dark 
… for my opinion 3mm+ glass
@Mauro_Manco Thank you, you mean issues about thickness too big?
@Mauro_Manco I use to work on a mirror (4mm), do you think it can be on the top of aluminum plate?
8mm Slow to heat and heavy and possible no have correct uniform heat distribution…aluminium not perfectly planar and prefer add glass for clean it fast too . 3-4mm thinkness are right size with glass arrive at your around 8mm. 8 + glass are too much. That my opinion.
I use 3mm 388mmx235mm for my mendel max xl, cero problems, you lave clearence en the screw holes for expansion of the bed? I use m4 screws and my hole its 4.8mm
@MakerGal yes I did, thanks.
3mm aluminum is not weak. I have entire printer bodies built from that.
@raykholo i was not planning to add a glass on the top but maybe it still the best solution to have a perfectly flat bed. I mean weak to be heated, it’s a big plate (430mm diameter).
I like heated glass becomes plastic sticks to it. And yeah it’s cheap and flat.
It’s certainly easier to get flat glass than aluminium. I made an aluminium bed but it took lots of time to get it flat as the cutting guillotine bent the edges.
@Daniel_Bull i will make it laser cut.
I usually use 3/8inch aluminum with a 300x300 heating pad and have no problems with heatup time. Usually around 3 minutes or so.
@Blake_Dunham with how much power? Are you running about a kilowatt there?
Depends on the heater, and if its mic6 cast aluminum. If it’s mic6 and your heater can handle it, otherwise 4mm should be enough. I found 3mm flexes a bit too easy.
It also depends on the width.
I have a 4.7mm and its plenty. My bed moves up and down because its a corexy, if yours is different, think of inertia of a moving bed.
My bed has a 300x300 silicone heater and the corners are
3 deg less than the center at 65
deg.
I would go for the MIC6 plate less distortion and heats evenly
I recently put a 12x12x.25" (6.35mm) mic6 tooling plate on my printer, been working great. Obviously takes longer to heat up than glass, but the heat distribution seems solid. Noticeably flatter than glass to at that size. Milled it with my xcarve cnc, fun project:
http://www.akeric.com/blog/?p=3860