Laser high pitch noises when engraving and cutting

Machine: Chinese 4060 with 90w Reci

Board: Cohesion3d board

Firmware: I have a new board and I’m using whatever it came with

Problem/ Question:
Hi everyone. A bit of history here, I purchased a used 4060 and upgraded the board almost right away. Within a week, the machine lost its power and even though it was reading 17-20 on the MAH gauge, the laser was no longer cutting through 1/4 inch baltic birch even at full power. I chalked this up as the laser wearing out as it was used and proceeded to purchase a replacement tube and power supply.

Here is where I am at right now. I have a brand new 90w (100w Max) Reci tube, matching power supply, 3 si mirrors, gaas focus lens and am ready to go again. I have my MAH meter on the control panel set to 20mah max when I hit the test button. Its a digital panel and the power output is set at 55 as I don’t want to overpower my tube.

I made a test cut last night and I couldn’t help notice that the laser makes high pitch noises depending on the setting in lightburn. I also notice when cutting from 40 percent to 100 percent it pegs my mah meter right at 20 but the sound of the laser is different for each power setting.

My question is: Is this normal? or am I hurting my laser? I did read that cohesion3d controls PWM but I don’t know what that means and I don’t want to burn out this tube.


Hi Ed,

Welcome to the forum!

This is expected behavior if it is only occurring when the laser is firing. This post is for someone using GRBL, but the fundamentals still apply: High Pitch Sound

Changing the PWM period in the configuration file may help (see Tuning article below). Start with these docs on our Knowledgebase and let us know if you have any questions:

PWM Control
PWM Tuning

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