Questions for those printing on glass

As my bed deforms significantly when it is heated, I decided to try adding a piece of glass to my bed. (yes Snapmaker has verified internally that this happens to them as well).

I had some old picture frames laying around so I cut a piece of glass to fit the bed and sandwiched it between the original print surface and the bed heater. The glass is quite thin, but for a test I figured I’d give it a shot. It couldn’t be worst that nothing. It did help.

I did turn up the heat a bit, as I’ve been printing PLA at 35C to help avoid bed deformation, but needed a bit more to heat through the glass.

I did find that the magnets held the bed surface down, but didn’t know if it would be enough so I used four pieced of tape to help hold it on better.

So my questions: Do you use the same print surface? Do the magnets hold it firm enough or do you use Kapton, binder clips, or something else? I was really hoping avoid going back to binder clips and kapton is a pain when you take the print surface off.

I do have a metal PEI covered print surface coming, should be here in a month. Unless it was in a crate that got lost at sea this week :slight_smile:


I havent really tried using anything other than the bed with sheet as designed, but for what its worth i know that alot of people will print directly onto glass instead.

it is much better to print on glas because you can remove every print from the glas without damaging it.
i have both of my printers updatet with normal glasbeds and i like it very much. Give it a try.

@ Sigogglin I was wondering if that would work. Does the print surface trigger the leveling sensor?
If it does then I would keep it on just for that. If not then it serves no purpose and I would just print on the glass.
I print on glass all the time on my other printer, still waiting for my Snapmaker to arrive and looking at how I will solve the undoubted warped bed.

No, out of the box it will not working, because the sensor did not recognise the glasbed.
But my little tool FiFix at thingiverse works great for that.

keep alive and kicking!

Thanks, didn’t know if there was any metal in the print surface.
FiFix looks great and I have already printed one! Very ingenious.
Glass gives such a great finish I wouldn’t bother with anything else and if you use Magigoo or similar everything sticks then pops off all by itself when cool. Only issue I have had with glass is PetG pulls chunks out of surface as it cools but a new sheet if glass is very cheap.

The provided removable print bed has a layer of spring steel inside that the inductive sensor picks up. I have a magnetic sticker I added to the glass bed so factory leveling methods still work.

Thats great so glass then print sheet should work, few bulldog clips round the edge as I have now and you have a flat bed that auto leveling can work with even if it’s not perfectly level. The only thing is you presumably have to up the bed temperature which might make it tricky for ABS.

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Someone else did that and found the print sheet itself was not flat, causing the flatness of the glass to be somewhat lost. I’m curious if you notice the same thing. Maybe after doing a calibration post your if your M420 V mesh coordinates are flat or not?

Sorry Brent, I am waiting for my machine to arrive but I will be checking that very quickly. Micrometer holder already printed. Very worrying if even the print sheet isn’t flat. Can understand the print bed with that support web never being flat with heating and cooling but a flat print sheet should be easy.

I can confirm that the print sheet isn’t perfectly flat (or at least there are differences in the thickness of the coating). I’ve been doing some tests as well (not on glass, but on a flattened wasteboard (and without heating) flipping the print sheet around could result in some significant differences. I didn’t keep al my measurements, but I believe I found differences up to .20-.15mm when trying different orientations. (there may also be some deviation in the individual measurements. Haven’t tested that exhaustively yet)

So even on a normal print bed the fifix solution might prove to have more consistent results.

You did? Under the glass? What is the thickness of the glass you used?

Would that help the sheet from shifting and negate the need to add some kind of clips? Magnetizing it to the heated bed?

What do you think about this type of glass, borosilicate glass. i can have it cut to any size i want.

1/8 thick would be okay right?

Or would you think gorilla glass would be better? Its available in much thinner sizes, although getting it cut in custom size is not an option on mcmaster carr anyhow. I could talk to local glass supplier I guess but im a mcmaster junkie.

I can use the metal PEI sheet and the inductive sensor picks it up just fine. I put it on top of a sheet of glass, but it is flexible so the binder clips on the outside made it spring up a bit in the center.

It is shipped with a magnetic sticker that you should glue down to the glass and it will hold the metal sheet firmly. Haven’t tried that because I just have a thin sheet of picture frame glass. Need to get into town to get a thicker sheet.

The FiFix looks interesting as well.

@MooseJuice Thats the gold standard in glass and will work exceptionally well. Most people just use 3mm glass either plain or mirrored what ever they can get cheaply. I think there is very little difference in the flatness of any decent glass. My experience is at the build your own printer level of printer where low cost was always good :smiley:


Thicker is better for retaining flatness. Glass makes things flatter (1) by bridging high spots on the bend and (2) pressing down on the bed with its own mass. If the glass is too thin, it will sag somewhat between them. I’ve not measured actual deflection of glass sheets under their own weight, so I can’t say that 1/8 would be adequate, but it certainly seems too thin to press down much.

Another aspect of thickness is how much internal stress it can resist. In the first layer of printing, you’re laying down hot plastic on a colder surface, expanding it. The hotter part is in compression and the outer, cooler part is in tension. Thicker glass resists those forces better than thinner glass.

Borosilicate glass differs from ordinary window glass (a flint glass) primarily be it’s lower thermal coefficient. It’s also less chemically reactive, but that’s not at issue here. Lower thermal coefficient means more resistant to thermal shock. There’s no issue with thermal shock with window glass, as experienced has proved. It makes some people feel good to have their premium glass, but insofar as I can see it’s only spending more than necessary.

I am printing on normal glas tried 4mm changed to 3mm both were goog for me.

On my A20T (260x260x3) I have heated uo to 90 degrees Celsius with no problem.

@MooseJuice I have been printing on standard 3mm glass for years now. It’s very flat and since all you are doing is taking the dips and rises out of the bed I dont think there is much chance of it sagging unless you leave in on the bed for a hundred years or so.

Dont see the benefit of borosilicate glass especially when on this device it will be on and off as you change beds with the usual chance of breakage.

I also tought about borosilicate glass, but my “window” were 12 Euros that is OK even if it breaks some day.

i am ordering some borosilicate glass because i am absurd like that, but also buying some regular glass.

the description on mcmaster carr explicitly calls out that borosilicate is ideal for 3d printing due to its smoothe flat finish and tolerance to heat swings without warpage.

is it necessary? probably not, but im going to try them both anyhow.