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NUBM44 + BlackBuck 8 = 25Hz ridges on engraved surfaces

jgrouse

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For some odd reason I'm getting ridges on engraved surfaces (mostly wood) which look close to 25Hz based on the feed speed of the CNC router the laser is attached to. The faster the speed the greater the spacing between ridges. I've put an oscilloscope on the 12V source and the 5V PWM source and both a very clean. I also checked the air assist to see if it was pulsing at about 25 hz and it's also a steady stream from the compressor (also tried compressed air from a can to see if the ridges vanished with no luck). As you can see from the image below, I sped up the feed rate (job sweeps left to right) about 2/3's down and then again a bit lower down). You can see between the o and r how the pattern stretches with speed increases so seems unrelated to the mechanics of the router. Each ridge at the top is about 0.62mm apart and the feed speed started at 1000mm/min. We use 50Hz 240V mains here so would expect the ridges to be 0.33mm apart if this were a mains hum on the power to the laser. Starting to wonder if the is an issue with the BlackBuck driver? Anyone have this issue before? IMG_3954.jpg
 
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jgrouse

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Entirely possible that having a peak PWM voltage of 5.12V is causing the driver to fluctuate when max power is applied. If it wasn't for the fact that the PWM / MOD pad on the BlackBuck fell off yesterday I'd be putting a trim pot on the input to lower that max below 5v to see if that fixes it? Now I have to wait for the replacement driver. Going to run plugs off the board next time so that I only have to solder the wires on once.
 




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