Onyx warping

[Zob]

Hi All,

I see there have been some historical problems with Onyx warping on the V2. Has anyone with a Rev 8 Onyx had warping problems?

At 80degC I see my Onyx bed dome up by over 6mm in the centre. With the glass plate and a 2mm aluminium heat spreader clamped down on top of it, I'm still getting 0.6mm warp across the bed. NO amount of calibration is correcting this.

When cold the Oynx is flat-ish with only a small warp of around 0.3mm for which the spreader & glass easily compensate. The glass and spreader are dead flat at all temperatures when not clipped down to the Onyx.

A first I thought I might be able to fix the Onyx in the centre by screwing it to the support bed, but this will only deform the plastic bed itself over time.

My Current thoughts are on supporting the glass around the edge and allowing the Onyx to warp under it. The heat spreader would float on top of the Onyx. Of course, without direct contact, the glass plate will take a lot longer to reach working temperature. The bed surface will be 5mm above the surrounding base, so I'm also going to need longer bed clip screws and some spacers.

Does anyone have any better ideas how I can compensate for, or eliminate, this problem?

Zob

[djarmag]

I have the rev 8 on my V3 and I did notice after making my FSR mount and doing a couple prints, my glass is not sitting flat on the onyx. I have the glass secured using cam bolt "thing" but not too tight to warp the glass. Flipping the glass bed from PEI side to the bare glass side and the height map shows its the same (my Z is slightly lower < .25mm than average) so my glass is not warped. There is a small airgap between the heater and bed so I will have to tune it up tonight