Re: grid kind of pattern on thermal
In our experience, when running stochastic screening, the laser focus settings are much more critical than when running conventional screening. We see a grid pattern over the entire plate when the laser is slightly out of focus.
If your problem is caused by laser focus settings, I doubt it would appear on just a small part of the plate.
More likely, it may be the punch is creating a ragged hole, or distorting the plate, which is causing that area of the plate to lift off the drum. This could move the surface of the plate to be out of the range of the laser's focus.
Common troubleshooting methods:
If you have another platesetter, try it on that machine.
Spin the plate around 180 degrees and re-image. If the problem is still in the same plate relative to the punch, it's probably not the plate material.
After exposure, manually catch the plate, turn it 90 degrees, and feed it through the plate processor. If the problem is still in the same spot on the plate relative to the punch, it's probably not the processor.