Engraving Alignment and origin issue

[Mike Syv]

Hi all,

I’m not sure if this is a hardware or software issue, but I’ve seen this on both RD Works and Lightburn, so my guess is hardware (or a controller setting).

I have an issue when cutting shapes (ornaments in this case), where I’m doing a long-ish engraving of multiple ornaments, then I do a cutout of the ornaments. Many times, some of the ornaments are not aligned properly (engraving to cut). I’ve also seen this with the cut and fill function in Lightburn and when doing the same thing in RD Works.

I did some tests to see if i can narrow down the issue. I did an engraving test at 100mm/sec, 200mm/sec and 300mm/sec. I set an origin point, pulsed the laser (to mark the origin), clicked start and engraved the file. At the end of the print, the laser head goes back to the origin. At 100mm/sec - the head did not return to the same place, it was about 1mm to the right in the X axis (gantry left to right). The Y axis (front to back) was aligned. At 200mm/sec, it was about 1.5mm to the right and 300mm/sec, it was dead on. It is repeatable as I did 200 three times and 300 twice. In all three cases at 200, the gap was the same (about 1.5mm) and both times at 300, it was fine. It seems to happen during the engraving and the farther away from the origin, but not all the time. In the pix, you'll see I've got LB set to engrave each group of images for each ornament. I've also tried engraving all of it at once. I get the same issue, but wreck 3 or more ornaments at the same time (and doing them by group is faster).

The controller thinks it’s in the correct position (based on the numbers in the controller and Lightburn) after the engrave. If I reset the controller, the head goes back to the proper spot. I did note the position numbers before and after the test and the numbers on the controller were the same. The cutter thinks it's in the right place, but it physically is not.

Here is what I’ve checked so far- the belt seems properly adjusted- snug, but not too tight. I’ve cleaned and greased the rail bearing and have marked the stepper motor sprocket where it press fits on to the stepper motor shaft to see if it’s slipping (it’s not).

I’m running an OMTech 50W 500x300 Blue & White Laser with Ruida 644XG & RDLC-V8.00.50

Hopefully the experts here have some thoughts on what to check next. I initially thought it was a mechanical issue (slipping or something), but I’m thinking software or controller settings now. The part that is really strange to me is I would have expected a bigger error with faster engraving speeds, not slower speeds.

I’ve put some photos of the cut path, the layout, controller settings and a pic of the before and after pulses at the three speeds. Thanks in advance for any help. All of the photos are from LightBurn as I recently switched, but the problem happens in the same way from RD Works.

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[Mike Syv]

For those who run into t
A similar issues where the engraving and cutouts don’t line up, check the PWM Rising setting fo pr the axis you see the issue in (mine was X). It was sat to True. I ran a couple prints as is, and could s
Clearly see the issue in a couple speeds. I went into the controller settings and changed this to false, wrote it back to the driver and reset the cutter. I tested a problem file at a variety of speeds and the issue is gone. On a whim, flipped it back (with no other variables) and the problem showed right back, and was predictable. Anyway. I flipped it back to false and the problem is sorted.

Other users may find the setting already false and may need to test this.

Anwham if wpanyone is looking for a solution to this, it seemed to work for me.

[Ian Bell]

Looks like you've done some good diagnosis work, i'm sure this will be of great help to someone - thanks for sharing

[Mike Syv]

Sorry for all the spelling errors in my post. I didn’t have my glasses on (clearly) and was typing it from my iPad.