Glass bed warped when heated ?

[Mind]

Oh... so I now have a dial-gauge indicator in my ever present quest to print ABS at 0.1mm reliably with 100% infill. I got the bed flat within 10 micron.

Then I started a thin-wall box test print and everything went pear shaped. Skirts were smeared towards the center of the bed. So I got out the feeler gauge and did some checking!

The center of the bed is now 0.1mm higher than the sides across the X. Determined with a feeler gauge at left, center and right edges of the bed across the middle Y position.

Ideas on where to go from here to debug this ?

[insta]

The glass bed warps when heated, as you found.

Do the 10 micron calibration with everything at printing temps.

[Mind]

Not sure if this is one of the reasons I am having calibration issues.

The glass is larger than the bed. The rubber corners at the corner of the bed are higher than the bed. The glass actually sits proud off the bed because as it is on the rubber corners (by about 1mm on each side). Is this part of the design or a manufacturing tolerance issue ?

I assume the bed and glass are meant to be 255x205mm .... well, the bed is, but the glass is 257x206mm !

NOTE: The rubber corners sit higher than the metal bed. This means there is 0.5mm airgap between the bed and glass !!!! Then you clamp them together and then heat the bed.... and I believe this is why the glass is warped at 110 deg C ! Thoughts/comments ?

Here is a picture of a typical corner:

[jimc]

thats not right. the glass should sit on the heated bed and everything fits between the rubber corners. loosen the rubber corners a bit to make sure they arent squishing out making things too tight. the glass should not be touching the screws. where is the rest of your corner? there is a square rubber pad everything sits on then a 90deg rubber corner that sits on top of that. the heads of the screws should be recessed down into the rubber corner.

[Mind]

thats not right. the glass should sit on the heated bed and everything fits between the rubber corners. loosen the rubber corners a bit to make sure they arent squishing out making things too tight. the glass should not be touching the screws. where is the rest of your corner? there is a square rubber pad everything sits on then a 90deg rubber corner that sits on top of that. the heads of the screws should be recessed down into the rubber corner.

Yep, the rubber pad is under that... the bed sits on it. The problem is the glass is bigger than the bed, so it protrudes all around. So much so, that it cannot fit inside the L shaped rubber corners. Compounded with the design that the rubber mount is higher than the bed..... and the glass sits on top of the rubber L shapes

What I just did, was to trim the thickness of two of the L shapes so that the glass would fit. Happily, the glass is now actually ON the bed. I wonder how this will effect heat up/etc ?

[rpollack]

Borosilicate has very little thermal expansion. We took several measurements and warp is under 0.05mm at up 110C. Clipping the HBP to the glass can cause the glass to bend slightly.

We also went through our glass supply and there were some over-sized pieces. If you would like a smaller piece, please contact support.

Thank you,
Rick