Diode laser won't seem to engrave below 5000mm/min above 40% power

Hi I wonder if anyone can offer any advice or suggestions please. Very novice at this! I have a Chinese diode laser. I usually use it for imaging but have started to try to use for some font/cutting. On speed settings such as 6000mm/min with 100% power the laser fires and moves round in a continuous motion. However much speed below that, it frames as normal, but goes to the start point and simply fires a few dots and won’t follow the shape. When I use 40% power it seems to move fine at lower speeds. I’m using GRBL1.1. and my settings are below. Could anyone suggest anything please. I’ve tried searching the forum and a few other things but a bit stuck as alot of the speed related issues seem to be with higher speed not getting lower speed to work. Thank you!



































The $110 and $111 values limit the top speed to 2000 mm/min along the X and Y axes, so the top speed cannot exceed 2800 mm/min (*) regardless of the commanded value.

The configuration looks like it’s intended for leadscrews, rather than a belt-drive machine. If it’s a leadscrew machine, higher speeds may be beyond its capabilities. If it does use belts, then the configuration values need tuning for typical laser use.

Some useful guidelines:

This suggests the power supply cannot supply enough current for both the laser diode and the stepper motors. As a rule of thumb, add up the total current for stepper motors (typically 2 A each), the input current for the laser head, and about 1 A for all the other widgetry. Double that number and make sure your supply has at least that current rating; typically, it does not.

(*) That’s along a line at 45° from the axes, with each axis running flat out at 2000 mm/min.

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Thank you so much - I will look at the configuration in much more detail. However the second point as I think you suspected is the issue - I had managed to use the wrong power supply for the last few days…

Keeping them straight seems to be a problem. Long ago, I began labeling which supply goes with which gadget, which definitely helps. Now I have a big box of supplies from obsolete junk that “might come in handy some day”. :grin:

Full power ahead!

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I label my by output - Wattage, Volts and Amps, then match those and find one with correct size plug, I have about 35 to sort through otherwise.

Aaaaand whether the output is AC or DC!

Nearly all supplies produce DC these days, but quarantining my AC supplies in a distinctly separate bag prevents a great deal of heartache & confusion.

Do not ask how I learned that lesson.


I won’t ask but can imagine letting some magic smoke out, my 2 AC live in a different room for that reason as there is only 2 so no need to label.

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