Are you using PCB heater or ALU+Silicone/Kapton heaters? Which is preferable? Are PCB heaters more newbie friendly? What are the advantages and disadvantages that you have experienced? I would really go ALU plate + Kapton heater fbut am not sure.
Go with cast alu plate and silicone heater, preferably AC heater if you can.
Silicone heater under an aluminum heat spreader, with glass on top for flatness, and PEI on the Top (pei bonded to glass via 3m 468mp tape)
Solid state relay with an AC silicone heater and MIC6 cast aluminum plate. That’s the best combination in my opinion.
I kinda went overboard with my heater setup, but I’m really liking it–It’s a 220W silicone heater (about 0.45w/cm^2) on a pocket-milled MIC6 aluminum plate with removable 3mm PEI coated glass on top. Heats up in about 3 minutes to 65C and can sustain 115C.
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@Ishaan_Gov
that’s nice setup there but I kind of entertain the idea of lighter stacks like @Eclsnowman describes but I wonder why no one really uses Kapton Heaters, way thinner than the silicone heater -and likely less potent. How thin can the ALU spreader be and also the glass what thickness is minimum?
@Florian_Ford , Kapton heaters should work as well Silicone heaters had the thermistor bonded better and were simply easier to source; 3mm glass is probably the thinnest you want; the thinnest I was able to source MIC6 aluminum plate was 1/4", but 3/16" may be doable too
For DC powered kapton should be OK, for AC main voltage I like thicker insulation from silicone heater.
@Dont_Miyashita I am not aware of AC Kapton heaters but they might exist. I would do cork beneath kapton I guess. Are you referring to the electrical insulation provided by silicone for AC current right -as opposed to thermal insulation?
@Ishaan_Gov As long as you put a glass on top why would you need the MIC6 aluminum, which is harder to source than standard ALU plate and more expensive?
@Florian_Ford , you could probably get away with standard 6061 aluminum plate as a heat spreader; I went with MIC6 for the extra flatness and better thermal coupling to the glass, to minimize the (very small) warping of the glass plate itself, to minimize deformation of the material while machining, and have a flat surface if I ever needed to print on the Aluminum bed directly.
I also went with the thicker aluminum because it was my means of mounting the bed to the Z-axis for my machine.
My source for Aluminum priced MIC6 not significantly higher than standard 6061 as well, but not sure what is available/economically viable for you.
You don’t need much heat spreader thickness at all if you put glass on top. Lots of people use a 1mm aluminum rolled sheet with glass on top for flatness. The purpose of the aluminum in that case is mainly to keep hot spots in the heater from causing localized failure.
@Florian_Ford I mean electrical insulation.
@Ryan_Carlyle Yeah I was thinking the same way regarding the heat spreader but wondering how would one space the silicone/kapton heater that is glued to the alu, with the glass on top, from the under carriage (bed support). Isn’t 1mm alu kind of too thin to be used as a connection element for the adjusting bolts? On the other hand how would the heater+spreader be kept in contact with the glass? Would gluing it in spots (to allow expansion beyond what glass does) to the glass be a bad choice?
@Florian_Ford What I do is set the heat spreader on a support frame (which can be your leveling structure or delta frame or whatever) then put a pattern of 0.5mm silicone heat-transfer pads on top of the aluminum, then just rest the glass on the pads. That puts the glass in decent thermal contact with zero stress or bend transfer. Very repeatable and secure.
umm… can you post a picture? Where does your silicone heater go? Shouldn’t the bed stack be:
glass
(silicone heat-transfer pads)
ALU spreader
Silicone Heater
Insulator (cardboard/cork/etc)
Support Frame (the 3point leveling structure above the frame or the support that the bearings are bolted to)
Yes, that’s basically it. Here’s my standard stack:
- 1mm PEI sheet
- 3M 468MP tape
- 3mm boro glass
- lots of little squares of 0.5mm silicone pad
- aluminum spreader, 1-3mm if the print area is smaller than the heater, 3+mm if the print area is larger than the heater
- Silicone or kapton heater smaller than the aluminum sheet
- In non-enclosed printers, aluminum/fiberglass automotive insulation tape to cover the heater
- Thermal fuse taped to the heat spreader somewhere w/ more insulation tape
- Bolt the aluminum sheet to a leveling sub-frame (cartesian) or rest it in a tight-fitting bracket on the main frame (deltas w/ autolevel)
It’s a lot of work to build, but works fantastically well.
Why are the silicone pads of 0.5mm thickness necessary? Are they used to keep all of the spreader surface as close to the glass as possible? are the pads sticky?, basically glueing the spreader to the underglass?
A picture would really replace maybe 1000wo 
Not a great pic, but here’s one: http://www.thingiverse.com/thing:612857
The pads are SOMEWHAT sticky, so they hold the glass stable but still removable. 0.5mm is compliant enough to make up for minor surface flatness issues without adding too much thickness to significantly reduce heat transfer.
OK i get it about the pads now -did a bit of research, basically CPU pads, not adhesive but tacky, as they refer to them . About PEI/3M tape I don’t know. PEI is great but I read it doesn’t work ok for nylon so I am not convinced yet.
I was hoping that the 2mm alu spreader with these pads would stay in contact with the glass even if not supported from below (I am planning to clamp the stack from the sides only, dunno if u can get the picture, otherwise I’ll make a sketch).
You can put PVA glue or gluestick on PEI for nylon just like any other build plate. Or keep a bare boro glass plate to swap out with the PEI plate. (That’s what I do.)
I don’t clamp my build plates at all – the weight of the glass and tackiness of the pads is perfectly adequate to hold it in place on the heat spreader. I haven’t tried it with a Y-bed printer though, just Z-bed and deltas.