Hi there,

To do laser engraving i have a programm (CamBam) which translates my gcode so that the z axis translates into spindle speed which then i can use for the laser to control it’s power via pwm.

I works really great but one issue:

In order to create a picture with different shades the gcode changes the “spindle speed” very quick and the feed interrupts for a short time every time it changes. That’s a problem since the laser creates a darker spot when the feed stops. If there are a couple lines without an rpm change it runs without interruptions.

I’m sure it is no g-code problem.

Can I make Mach 3 stop from doing this?

Thank you for helping 

With Mach3 changing the spindle speed with the 'S***' command will break the Constant Velocity chain and cause the problem you describe. The only solution is not to use the S*** command or any other command which breaks the CV chain.
You could use a digital encoder, driven by your Z axis, to control laser power or use a digital potentiometer (driven by Step and Direction signals) and set-up as an Axis. Both these methods have been sucessfully used by others in the past to create stunning 8 bit laser images.

Another alternative is to change to Mach4.

Tweakie.