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Missing engraving dots on successive jobs

Posted: Mon Jul 15, 2024
by Joncon00
I made a custom "Laser Lathe" to produce lighting parts. It has this issue where after a few successive runs of the same engraving job it will start to produce spiral patches of unetched areas where the laser did not seem to fire. Usually after about 10-20 minutes of running.

My machine is featured here.
https://www.grbl.org/100-watt-rotary-custom-laser

The setup is built on a 100W Reci Tube and basic cloudray power supplysupply. The motors are nema23 steppers with integral drivers which drive X and A axis. The controller runs GRBLHAL to interpret our custom gcode. There are three mirrors that that direct the beam to a fixed head. The parts being etched are on a rotary mounted on a sled (axis). The included image shows parts made with the same exact program but producing different appearances. Baically the density of dots should be a smooth gradient without any spiral or empty patches like #3 & #7 in the image. With some discussion with the designer of the controller I have tried:

Changing out the pwm line from the controller to laser ps to a shielded cable. No change
Checked the thermals of the controller. Everything was cool. The water temperature stays between 18-20C
switching computers to send the program. Seems to help initially

Looking for ideas on what further to look into. Thanks in advance!

Re: Missing engraving dots on successive jobs

Posted: Tue Jul 16, 2024
by Gareth Lewis
Hi JonCon00

My original thought would be the cooling system, even though it's cooling to 18~20C.

Russ Sadler did a video on the cooling effects of the CW5200 chiller on the laser beam https://www.youtube.com/watch?v=PJw-3uK6ZfM&t=1s

It could be that your cooling circuit is being aggressive when it kicks in after 10~20 minutes causing changes in the laser performance. It may be a case of you just needing to adjust the settings on your chiller.

Re: Missing engraving dots on successive jobs

Posted: Tue Jul 16, 2024
by Gene Uselman
I am loving the aluminum extrusions [80-20 in the US- altho I use 2020 too]. If this is not proprietary I would love to see more of this. Gene

Re: Missing engraving dots on successive jobs

Posted: Fri Jul 19, 2024
by Gareth Lewis
Gareth Lewis wrote: Tue Jul 16, 2024 Hi JonCon00

My original thought would be the cooling system, even though it's cooling to 18~20C.

Russ Sadler did a video on the cooling effects of the CW5200 chiller on the laser beam https://www.youtube.com/watch?v=PJw-3uK6ZfM&t=1s

It could be that your cooling circuit is being aggressive when it kicks in after 10~20 minutes causing changes in the laser performance. It may be a case of you just needing to adjust the settings on your chiller.
Hi JonCon00

Did this suggestion help at all?