Strobing and losing focus during line cutting with a Gweike Galvo

[Brad2 (Bradley)]

I am using a Gweike Max 50W galvo/fiber laser, using the line cutting tool with wobble (thanks to this forum for that tip), the settings works usually great, but lately the cutting is very uneven and the laser focus seems to glitch out several times, the laser begins strong and loud. But slowly decreases to be invisible, and only the red focus laser visible. When cutting a circle for example, the laser flash is almost strobing/flashing, and when the job is done one can see where it was flashing, since half of the circle has little or no cutting at all. While the other half is cut through completely.

Just touching the electric lift (either up or down) immideately makes the laser go boom and is instantly very loud and bright all over the circle again.

The problem doing this 10 times every minute for a job that has over 1200 passes is not optimal, since the constant hoisting or lowering of the laser during work makes the end result blurry and I often end up with multiple (close to each other) lines, where in the optimal world there would be one that pierced the brass sheet completely.

I should mention that usual deep carving seems not to be affected and works good.

Anyone that experienced something distantly similar?

[jkwilborn (Jack Wilborn)]

If it’s a galvo fiber, it’s likely a JCZ or similar type of control board.

@Brad2

touching the electric lift (either up or down) immideately makes the laser go boom and is instantly very loud and bright

This would indicate that it isn’t in focus.

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Could be the either of these

1. head isn’t square to the table
2. lenses depth of focus (dof) is too shallow for the application.

You can ensure it’s squared up and use a longer lens. What lens are you using?

I have an F100mm, it has a dof <0.5mm and drops off very quickly.

[Brad2 (Bradley)]

Its their standard 150 mm lens, and the strange thing is that it runs out of focus so fast, one thing to adjust it and then it works, but as soon as I barely touch the lift buttons, the laser is going boom again, to then within a minute slowly decreasing until only the red dot is visible, same thing happens again and again when barely touching the lift buttons (both up and down seems to make the trick)

[Aaron.F (Aaron)]

You also have to be aware that by changing the focus height, you also change the projection onto the material. - Similar to a projector, where the image becomes smaller with shorter distances.

I’ve got better results when I decreased the Wobble Step to 0.04 and increased the Wobble Size to 0.2. This will create a bigger gap for the beam to get in there.
You can compensate for the larger beam thickness with a Kerf Offset.

Also, set your focus halfway into the material.

Feel free to share the settings you used and show us the results.