Looks like perforation, but not

[ednisley]

@URi613

It’s the “perforation” that suddenly showed up.
Material has not changed.

It is possible the CO₂ tube stopped resonating in what’s called TEM00 mode and no longer produces a nice round beam that can be properly focused.

This post gives the test procedure with a pointer to a lengthy discussion of what it all means:

Cleaning omtech 80w

Assuming you’re running the same jobs, then a sudden change suggests a hardware problem, rather than the gradual deterioration brought on by crud accumulating on mirrors / lenses. Check for a loose mirror or focus lens: the lock rings must be snug. If the machine has molybdenum mirrors (heavy metal slugs), then they’re easy to clean. If it has gold-plated silicon mirrors, then they’re easy to damage; check for any surface imperfections. Similarly, the focus lens must be clean. You must disma…

If the test at the tube exit doesn’t produce a round spot, then you’re in line for a new tube.