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Heated bed design questions (400mmx400mm)

Posted by wouterheer 
Heated bed design questions (400mmx400mm)
January 04, 2017 06:54AM
Hi All,

I am building a corexy printer with a build volume of roughly 400x400x400. Now I'm up to the point on deciding on a heated bed:

- Must work with Silicone Heater (220v 600W)/SSR
- Must work with inductive auto leveling system
- Print Mostly ABS, PETG. Not really interested in PLA.

So my plan (top to bottom)

- 3mm 400x400 glass plate/mirror with kaptop tape OR ??mm 400x400 removable aluminium top plate with kapton tape.
- ??mm 400x400 Aluminium plate (how thick must this one be?)
- Silicone Heater
- Spring mounts on frame

Can anyone help me with the dimensions?
Does the inductive auto bed leveling system work through the glass or do I need a aluminium build plate?
Ofcourse by selecting the right thickness of materials I would like to prevent 'curling/bending'

What is the proper Quality of Aluminium to order?

Thanks alot!!

Wouter.

Edited 1 time(s). Last edit at 01/04/2017 06:55AM by wouterheer.
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 06:59AM
If you're building a corexy and the bed moves in Z, you can make it as heavy as you like. I would say that 6mm aluminium tooling plate would be sufficient, but going bigger wouldn't hurt.

As for grade, buy tooling plate or ecocast or get it milled flat if you can afford it
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 07:52AM
Thanks!

These are the aluminium options I have with a local vendor:
AW-1050A H14/H24
AW-5754 H111
AW-5083 H111
AW-5083 H321
AW-6082 T6/T651

So would this be a proper setup:
400x400x6 aluminium fixed aluminium plate (with silicone heater attached to it) and on top a 400x380x4 removable aluminium 'build plate' with kapton tape attached with 'office' clips.

This ofcourse means the combined plates 400x400x10 to be heated, is that realistic?
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 08:01AM
Why do you need two plates? I understand being able to swap plates is handy to some, but 400*400mm is very big.
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 08:05AM
Well, I like to print on kapton tape and putting the tape on the removable build plate is much easier than on a fixed build plate. If it has more con's than pro's I might need to reconsider :-). I'm open for that...
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 08:41AM
I would perhaps consider investing in stronger (thicker) Kapton tape so that you don't need to replace it as much. As for heating it, I think your heater should be adequate but maybe consider some thermal paste between the plates to aid in heating.
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 09:08AM
Thanks for your quick replies!

I think I'll go for the single plate 6mm, a top plate is ofcource easy to add later.

And... Should the Aluminium be anodized or not?
Re: Heated bed design questions (400mmx400mm)
January 04, 2017 07:19PM
The surface processing of the aluminum plate doesn't matter- it's going to be covered with Kapton or whatever you ultimately decide to use. It is far more important that it is flat so you can actually level it and use the entire surface to print. The best way to get a flat aluminum surface is to use cast tooling plate which comes milled flat.

I used 5 mil thick Kapton tape for a few years and found that it typically lasted through months of daily printing before requiring replacement. If you get the more common 1 or 2 mil stuff you'll be replacing it every few prints. I've recently switched to 60 mil PEI and it seems to work at least as well as the Kapton did but should last even longer because of the extra thickness. I suspect that 30 mil PEI is more than adequate and will provide very long life.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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