Vertical Banding when raster engraving.

[Chris M Jones]

The banding is occurring when raster engraving. I have a ULS 6.60 and am having no success with resolution of these symptoms. I do mostly acrylic engraving and use a very light etching for best light absorbing for my signs. The issue is more prevalent in larger engraved areas. Etching in shades of gray also exhibit the same behavior. X arm had been replaced, x motor and the bearings have been replaced.

[Kev Williams]

Are you rastering this direction--
tst1.jpg
and getting all the vertical lines shown? or is the pic sideways to the raster?

If rastering as shown, might be a symptom of Y axis travel due to belt slop, or some crud or something else to do with the teeth of one of the two long Y belts (or a cog) is creating a slight gantry misalignment when the belt & cog mesh at that point. (My LS900 had a belt issue (probably just wear) between the 2 and 3" from left position, small text engraved within those coordinates would get very thick, so for a long time I just called 4" from left my "zero". A new belt totally fixed the problem.)

If the pic is sideways and you rastered parallel to the lines shown, then beam wobble and overlap is likely the problem.

Easy to test- take a 4" long piece of plex, engrave a 3-3/4" x 3/4" rectangle at full speed and power, X at 500 dpi and Y as small as possible, 25 or 50 lines per inch. Check the lines to see if they look like these:
banding1.jpg
band2.jpg
note, the very bottom test, that's straight? That one I vectored, to prove to myself that the wobble created when rastering wasn't mechanical..
-My LS900 has done this since day one. Factory claims it's normal. Haven't done this test yet with my other lasers (I should)

I'm curious if yours will do this-

[Ian Stewart-Koster]

What other machinery did you have running?
We have 2 air compressors here (for spray painting, general air supply, etc) - one has a 2hp and one a big 3hp motor.
The power drain when the capacitor-start 3hp one kicks in is enough to give a notable flicker or band in engave lines I've found - but that's in the direction they're engraved- parallel to the X axis gantry.
If I need the compressor on while engravnig, I make sure it's the smaller one, not the big one!

[Keith Colson]

I had the same problem with the same machine. It turned out the Z axis was out of calibration so the work was slightly out of focus.

Thread is here with photos
https://sawmillcreek.org/showthread....n-my-Universal