My galvo head started making an audible whine and one of the axes started shaking. At first I could only hear it, then had quality probs, then it was oscillating back and forth at max speed in like a 1/2" line even while idle. The red dot was a line and any attempt to fire the laser would have that movement added to it. I contacted the mfg and they sent me a new galvo head, it was only a week old or so. I don’t know the exact nature of the problem but it’s in the galvo head which contains a driver board and the galvos.
I suspect you have the same problem, because it looks specific to the axis.
With your 150x150 lens, that should make about a 0.04mm spot. Your LI is 0.03, so there’s some overlap there. I generally shoot for LI=spot size.
But, your movement direction. 25KHz @ 2000mm/s means it’s firing with a 0.08mm interval. That’s putting standalone dots really far apart.
I don’t know the performance charts for the G2, I have an M7 300W MOPA. But I’d recommend you adjust speed and/or freq together so that speed/freq=LI=0.04 (for a 150 lens).
A 110x110 lens is more conventional for small stuff like coins. It will get you a smaller spot size while keeping depth of focus and lens height reasonable, and the beam angle won’t be problematically high. For a 110x110, speed/freq=LI=0.03
Choose a nonuniform number for angle increment so that it will NEVER line up again. I ran this one through ChatGPT and it went through number theory and coprimes and got 42.7 deg, it’s near 45 deg steps but won’t line up again until 1800 passes. And after 20 passes it’s drifted past the first orientation too.
Or, if you want to do a 90 deg advance on each pass (basically cross-hatch), then 90.7 or 89.3 deg. So any pass is “basically” 90 deg cross-hatch against the one before, but then the third pass won’t align with the first.
I had to think this one through- ok, I’m looking at 0 and 180 deg as “aligning”. Even if you’ve got bidir off that’s still mostly the case. If it were a very small object, then using 90.7, the third pass is only 1.4 deg from the first which may not be very far apart, esp in the middle. But then you’d look at using 42.7 deg and cover all the directions every 4 passes while never repeating.
Thinking through that, yep, these are the only 2 choices that make sense. 42.7 would be my first choice unless I thought ~90 deg (90.7deg) cross-hatching was somehow going to be a different effect.
