I am in the middle of building a custom Kossel style printer with a much larger printer area then standard Kossel’s, 330mm x 450mm tall build area. I have been wanting to use a mirrored glass build plate and came across a round mirror with the exact diameter I needed, thickness is 3.5mm on the glass. Now my concern is that I want to install a heated bed underneath but I am afraid that since the mirror is not Borosilicate Glass it will crack or shatter. Anyone with experience with this or ideas on how to proceed would be appreciated.
SOC3D
May 20, 2016, 7:34pm
2
Edit: less thermal expansion is what i was lookong for here. Because the glass expands less under heat it is less likely to break during a fast hot cold cycle. Borosilicate glass is higher heat resistant and has better tolerances for high temp fluctuations. Float glass, salt glass, mirror glass, whatever name it has in context works just fine as a print surface. I’ve stopped using borosilicate glass as it tends to degrade and sheer at the same rate as regular glass. When attached to the heated with a decent thermal conductor like Arctic silver or a high w/Mk value thermal pad regular glass works fine if not better than boro glass. The last commercial FDM printer manufacturer I spoke to said that they also stopped using boro glass in their products for the same reasons. Standard glass works fine under a few 100 degrees Celsius, it degrades at the same rate and it doesn’t have a noticable impact on heat distribution. Unless you call Corning (now Dow Corning?) and ask them to make or recommend custom glass just go with what works and looks shiny!
See the image, this is the mirror I am going to use, I am hoping it wont crack, main purpose of the heat bed is for large print areas that tend to warp up on the ends I want to eliminate this but I also dont want the mirror to shatter. It is the only one locally I was able to get my hands on.
SOC3D
May 20, 2016, 10:15pm
4
I’ve printed on 1-2 mm picture frame glass. 6"*3" ABS in open air without breaking the glass and 10"*6.5". (I broke the glass with my hammer and paint scraper on that one) It could break, it could shatter. It’ll most likely be fine, *try it at your own risk.
did you have a heated bed on it
SOC3D
May 21, 2016, 12:42am
6
All of my printers have heated beds. So yes. I print ABS at 90 degree first layer and 75 layer 2 and up. I’ve use picture frame glass up to 110 c bed temperature.
Well one thing you could do to avoid it cracking is also fine-tuning your firmware to guarantee slow heating/cooling cycles of the print bed. Also, you’ll need to find a way to mount it that can handle the slightly higher thermal expansion you’re going to get.
Finally, you’ll also want to make sure that you calibrate the printer when the bed is at printing temp (yep, if it’s expanding, you’ll change your 0 level)… I’d strongly suggest getting yourself a piece of borosilicate glass if you can - doesn’t have to be circular either - I’ve seen Deltas with hexagonal beds, not for bigger build volumes, but because it’s easier to get a square sheet and find someone to cut it in a hexagon for you.
SOC3D
May 22, 2016, 1:19am
8
Borosilicate has “less” thermal expansion. The same rules apply for both. Fine tuning a Delta with classic or simulated annealing is generally done with the build surface hot and cold and keeping the best result. Or with the bed and extruder both at temp. Binder clips expand really well!
