Perhaps others have seen this: my most recent ABS print pulled a small divot (6mm x 6mm x 0.4mm thick) of glass off of my build plate! The divot remained stuck very tightly to the underside of the print after cooling.

The divot was shaped like a a wedge of pie with a 90 degree angle in the "corner." It did not otherwise damage the glass, and the print came out fine. The print was completely free of the bed when I removed it, having cooled overnight. So the divot was pulled out of the plate while it was cooling, I suppose. I was not there to see or hear it happen.

I use inexpensive window glass, 3mm thick, from a big box store. The bed was heated to 110C, which is typical for my ABS prints.

The object was a terrain model of a mountainous area. It is thick (>20mm) at 3 of the corners, and I had been having problems with those corners lifting slightly off of the bed. But the divot occurred under the thinnest corner (< 3mm) at a location where I had never seen any lifting on previous prints.

The change I made in the model right before this print was to increase the bottom layers from 3 to 5. I did this because the thick corners had been pulling up enough to actually break the bottom layer on previous prints. Making the base thicker solved that problem, and the print was perfectly flat across the bottom.

I had just reapplied a very thin layer of All Purpose Glue Stick to the bed before this print. My practice is to apply a few swipes of the stick, then even it out using a damp paper towel. I was actually concerned that I had not applied enough since this was a thinner application than normal for me. And the print was completely loose after cooling. So I am not blaming this on too much glue?

Comments and suggestions to avoid a similar occurrence in the future are welcome!

Jim