Is this usual?

[Bob Davis]

I have been lasering some laminated plastic signs using several passes and came up with the result in the attachment after the first pass.
It would appear that the laser is strongest from the point where it turns on, diminishes in powershortly after that point and then increases in power again just before it is due to turn off.
Is this a typical result or is it a sign that something is malfunctioning?

[Rodne Gold]

Thats not at all typical - speak to your agents re what can be wrong, it can be many things
1) tube malfunction
2) Wrong tickle voltage
3) Bad focus
4) Loose mirror
5) bad optics
6) dirty optics
7) tube oveheating
8) alignment problem
9) etc etc
My guess is no 1 , but hopefully I am wrong...

[Larry Bratton]

If that is typical engraving plastic intended for lasering, it should engrave in one pass, not multiple passes. As Rodney said, many possibilities exist, but you definitely have something out of kilter. Did this just begin or has it been an ongoing problem? Is it only with this material? Is your table level and the work flat? Cleaned the lens and mirrors lately?

[Dan Hintz]

The look that it's stronger at both the beginning and end of each pass may be a red herring. I suggest one possibility is it is stronger only at the beginning of the pass (left to right)... because you are firing on the return stroke (right to left), as well, the strong pulse as the tube first turns on is clearing a bit of the end of your left-to-right pass. If that's the case, it would make it appear as if it's strong at both beginning and end.

If true, that would lead me to suspect a failing tube/RF section.

[Viktor Voroncov]

Bob, what is type of your laser - glass or aluminium?