Breaks glass on pierce almost every time

Using the Soda lime settings and caliper measuring the glass to match thickness but no matter what we do it will break the glass 80-90% of the time. this is a brand new machine with about 4 hours cut time. the cut bed is getting beat up but there are plenty of clean areas on it. We even cut the pieces down smaller but it cracks even those.

Is there a different piece pressure setting or will the lead in help here or need to put something under the glass or what are we doing wrong?

Hi @JasonMarshall thanks for joining the community forum and sharing your concern!

We can work around some of the glass cracking issues by processing glass with the following two things:

  • placing thin (rubber sliver around the perimeter of the pane of glass) so that the 1-2mm of bed movement that happens during a cut or the bowing doesn’t result in a fracture.
  • placing rubber washers under the head of the fixturing screws to give compliance and not allow a piece of abrasive to create a pressure point on the glass

The following items have been tested in-house on multiple glass sheets and have had great success in order to produce glass cut-outs without too much concern for the bed warping.

  • Plastic Fasteners here (100pcs for $10)
  • Rubber material for placing under glass around perimeter to ensure no stress spots (like bowed, uneven cutting bed). Cut some 1/2"-1" wide strips from this material and place it under the edges of the glass as it makes fastening a lot less stress-inducing
  • For washers these seem to be working better for us on really fragile things like thin glass: Mcmaster-Carr # 90130A013

There are even some community made 3D printed washers and other recommendations found in this post! (Link)

Where does the glass break? At the pierce point, near your screws (or whatever you use to anchor the glass to the bed), during the middle of a cut, near tabs?

We’ve found that a beat-up bed or screwing down glass too tightly can cause some fracturing issues. (We stopped using screws altogether and started using custom-made 3d printed toothpick anchor things that work well. Turns out metal and glass don’t work well.)

Great suggestions thank you! It always happens (for us at least) at the pierce point. We are also thinking it might just be cheap poorly annealed glass as well. I have made some 3d printed doodads for holding in place as well.

I place a sheet of corrugated plastic poster board horizontally under the glass before screwing the glass down. This has been a game changer for me. It helps to support the glass, yet cushion the impact of the pierce. I order the sheets precut to 12x18 and cut them down to match the size of the glass blank. The corrugated plastic is sacrificial, but the small cost is worth it. It’s the same material the bed is made from and not only does it result in more successful cuts, it also preserves the use of the beds so they last longer. I can cut glass that’s as thin as 3/32" wide between cuts! The only thing you need to be careful of are large deterioration holes (craters) in the cutting bed, as the bed will not be able to properly support the corrugated plastic when making small shapes.
12x18 Corrugated Plastic
Or save a few bucks, if you don’t mind cutting them in half.
18x24 Corrugated Plastic

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@SlateCraftUSA this is genius! thank you and ordered.