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Which glass for heated bed

Posted by MStarha 
Which glass for heated bed
September 06, 2021 05:13AM
I am building my CoreXY 3D printer with 350x350 mm heated bed at about 4mm thickness. I just found out that borosillicate glass is unavailable at the local glazier. He offered tempered or ceramic glass instead. Which one should I go for? I read that both are a more expensive option to borosilicate glass, but I worry about the temperature stability, warping of the glass (in case of the tempered one) and parts (not) sticking to it. Any experience is appreciated.

PS. The ceramic glass at this size would cost me about 45 USD. The glazier did not tell me the prize of the tempered option, but I reckon it will be around 30 USD, which is much more acceptable if it does the same job.
Re: Which glass for heated bed
September 06, 2021 11:35AM
If you have a heat spreader (e.g. a few mm of aluminum) between the heater and the glass, then use ordinary float glass. I have used it for years. You only need special glass if it is heated unevenly. Don't use tempered glass because the tempering process tends to warp the glass.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Which glass for heated bed
September 06, 2021 12:16PM
I am using 300x300 mm Keenovo silicone heater on 5 mm thick 350x350mm cast aluminium plate. And I intend to print PETG and ABS mostly, that means up to 100-120 degrees on the heated bed. That might cause some stress in the glass. Will the ordinary float glass survive? Any thoughts on that?

I will ask the glazier about the warping, whether it is something that can be eliminated at this size (which is quite small for a sheet of glass).

Thank you.
rq3
Re: Which glass for heated bed
September 06, 2021 08:29PM
Quote
MStarha
I am building my CoreXY 3D printer with 350x350 mm heated bed at about 4mm thickness. I just found out that borosillicate glass is unavailable at the local glazier. He offered tempered or ceramic glass instead. Which one should I go for? I read that both are a more expensive option to borosilicate glass, but I worry about the temperature stability, warping of the glass (in case of the tempered one) and parts (not) sticking to it. Any experience is appreciated.

PS. The ceramic glass at this size would cost me about 45 USD. The glazier did not tell me the prize of the tempered option, but I reckon it will be around 30 USD, which is much more acceptable if it does the same job.

There are many types of ceramic glass, but you are probably being offered pyroceram or ceran (trade names). Both have extremely low expansion coefficients, sometimes even less than quartz, so they will not warp or buckle with heating and cooling, nor crack if exposed to quick temperature changes. They also don't conduct heat very well. And they are very strong, although they will break if you try hard enough. All of which is why they are used for smooth cooktop surfaces and windows on fireplaces and the like. They are usually not clear, but tinted yellow or red as an artifact of the material itself.

Given the choice between tempered, borosilicate, and ceramic, I would choose the ceramic glass. It will be very stable, dimensionally and thermally, and a heat bed needs to be stable, not responsive. Also, ceramic glass sheets tend to be manufactured under very controlled conditions so that it should be very flat, with both sides parallel to each other.
Re: Which glass for heated bed
September 07, 2021 02:48AM
Quote
MStarha
I am using 300x300 mm Keenovo silicone heater on 5 mm thick 350x350mm cast aluminium plate. And I intend to print PETG and ABS mostly, that means up to 100-120 degrees on the heated bed. That might cause some stress in the glass. Will the ordinary float glass survive? Any thoughts on that?

Float glass will be fine in that setup, certainly with PETG. I mostly print PETG, but I have printed ABS a few times with the bed at 100 to 120C. The only times I have damaged a bed is when the print has stuck to it so well that it took a few shards of glass with it when it came off.

It's handy to have several beds so that when a print finishes, you can remove the bed+print and start another print on a new bed, instead of having to wait for the print to cool down enough for you to remove it.

Edited 1 time(s). Last edit at 09/07/2021 02:53AM by dc42.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Which glass for heated bed
September 07, 2021 02:56AM
Thank you for your answers. I will ask the glazier, how much does the tempered glass warp, and if it is within reason (0.1mm across the whole plate) , I will go with that. Otherwise I wil try the float glass. I am leaving the ceramic glass as the last option because I do not want to waste 45 USD on something that does as good job as a piece of glass for 10-15 USD.
rq3
Re: Which glass for heated bed
September 07, 2021 09:04AM
Quote
dc42
Quote
MStarha
I am using 300x300 mm Keenovo silicone heater on 5 mm thick 350x350mm cast aluminium plate. And I intend to print PETG and ABS mostly, that means up to 100-120 degrees on the heated bed. That might cause some stress in the glass. Will the ordinary float glass survive? Any thoughts on that?

Float glass will be fine in that setup, certainly with PETG. I mostly print PETG, but I have printed ABS a few times with the bed at 100 to 120C. The only times I have damaged a bed is when the print has stuck to it so well that it took a few shards of glass with it when it came off.

It's handy to have several beds so that when a print finishes, you can remove the bed+print and start another print on a new bed, instead of having to wait for the print to cool down enough for you to remove it.

I have found that just a couple of drops of rubbing alcohol next to a PLA print on a 60C bed makes the print pop off without cooling the bed. I have NOT tried this with ABS on a 100C bed.
Re: Which glass for heated bed
September 07, 2021 09:46AM
I recently found that alcohol on the bed helps release an over-adhered TPU print on PEI, too.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Which glass for heated bed
September 12, 2021 02:27AM
Why use glass? I've used PrintBite for years. I suspect PEI would work just as well.
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