Wavy lines 2/3 into a flat otherwise perfect project?

Heya guys,

I was engraving this 15" round sign (“Fill only” no lines) with my brand new 50W Co2 Laser I got just 2 days ago. I was cutting via USB / RUIDA 664XG with Lightburn on my new windows 10 laptop @ 200.00 speed / 20.00 power.

2/3 of the way into the project the laser started to follow a wavy type of line and this occurred all the way across the image. The piece being cut was secured in place firmly so it had not moved and the surface is perfectly flat. Shading and lines don’t match up either if I run them as “line/fill”

The Laser is 2 days old, the Gantry is solid, belts are tight, mirrors are alligned and not loose and there is no debris in the bearings, pulleys, belts etc…

Here are images of the cuts as well as what the files look like for comparison.


I can add a few observations…

The first photo shows where it has ‘moved’ over. It doesn’t appear to ‘go back’ to a ‘correct’ start of the scan position.

The 2nd photo does show that it happening and it is returning to the original scan start position.

The first the image looks like something is lose. Not necessarily for the second.

I assume you have done a good overall checkup of the hardware, bolts, screws, belts…?


I have looked at what I can see, and nothing appears to be loose. but I am no expert.

with the laser powered off, open the door, grab the head and wiggle it.
don’t touch the optics.

you’re looking for “Mechanical Backlash”

You should have nearly zero backlash because of the belt drive - but a loose set screw or some mechanical binding can cause this type of lost motion.

Happy hunting!

Even though the previous 2/3 of the 15 inch diameter project had no issues at all? a loose Optic or mirror would rattle all the time. This is on the Y axis as well so Maybe a Gantry Stepper Motor? Again, it is zone specific. It did this in the same exact spot the second time I ran the project.

Debris on a drive belt or damage to the guide rails can create a repeatable lost motion problem (like binding) for a given area.

Power the machine down and move the laser head through the affected area. Determine whether (or not) you feel resistance or looseness.

pulled the manual. This might be noteworthy.

5.5 Lubrication
It is recommended that you add white lithium grease to the X and Y axis guide rails and screws at least every two weeks.

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