I watched some videos of Russ Sadler about producing a good quality photo since my products are still mediocre.
In this tutorial he actually works with Lightburn.
Now what he suggests is to measure a PSU response speed/delay and from that derive a laser speed at which the beam can actually fire at each dot.
I did that test and calculated that my response delay is about 5 ms (my PSU is MYJG 50W from ZYE laser). Is this delay normal or is it too high? He mentioned in the video a reasonable delay is 1 ms.
And can too long response be a cause of mediocre photo shading? I adjusted my speed based on this video and managed to get way more dots to my piece, but the result was still far from good.
I think I could buy a new PSU but I am unsure if it would help.
Here is a photo engraved at 36,6 mm/s at 15 % power with 50W Chinese CO2 laser at the Jarvis dither. Compared to previous results there is much more detail (=more dots).
Now the reason I am curious about this is that I tried to engrave a shades of gray pattern on birch plywood and I cant get dots from light areas onto the piece in no combination of speed and power and it drives me crazy.
I engraved a rectangle at 200 mm/s in the fall+scan mode and then measured a gap between where the scan line should start and where it actually started. The gap was 1 mm, so if my speed is 200 and distance 1, needed time is 0,005 s or 5 ms.
That could be a mechanical, or mechanical + electronic, or electronic issue. The most likely is mechanical backlash.
ZYE are a well-respected manufacturer and in my experience their response times are well below 1ms.
Certainly at speeds of 500-700mm/s, I don’t have to put in any offset calculation with a ZYE 130W supply, but I have a well-tuned, well-specified machine with advanced CNC components and have negligible measurable backlash. You get what you pay for.
It’s my most-often supplied component to customers and I don’t have any complaints about delay.
I’m not convinced that Mr. Sadler always follows the scientific method when postulating a fix to a problem.
I have invited a service man to check the laser. He tried a different PSU and the result was a bit better.
What had much greater impact was increasing max power to 90 % and slow down to 100 mm/s. With this setting there were all dots.
I think I will drop the photo engraving since i cant engrave with that power without damaging the tube.
What the service said was that my KH laser tube might not be good enough and replacing it with EFR or Yongli could help.
Changing the PSU without calibrating it, using a laser power meter, doesn’t tell you much.
Running your tube at 90% won’t damage it, as long as it’s calibrated to the operational specs of your tube. That’s ‘K40 user’ logic, where their machines don’t have the ability to calibrate the PSU.
The only way to properly test your upper limit is to measure using a laser power meter and using a block of acrylic, where you can physically see how deep your cut is.
Often, going over 85% doesn’t give you more cutting power, as that last 5% is just making more heat inside the tube.
EFR, SPT tubes are excellent. Yongli is a good budget tube, but not at the same quality or power as EFR and SPT (or Reci - but they are 2x the price of the other two).
KH is about the same performance as Yongli, with a shorter life span.
