Getting a double image when rastering, but only in a certain spot

Ok, I have a mostly stock K40 engraver (added air/upgraded exhaust) and use Inkscape & K40 Whisperer. I am getting a double image when I raster, but the odd thing is, it’s not the whole image, just in a certain area. It’s not happening on the ends of an image, or the top and bottom. It only does this just to the left of center, everywhere else is crisp and clean. I’m assuming it’s not a laser alignment issue since everywhere else on the image is crisp, and not a gantry alignment since usually that occurs in a corner. It shouldn’t be a backlash problem if it’s not on either end where the laser switches directions. I cleaned the mirrors with no change. I also tried slowing the speed way down and that didn’t help, either. I’ve spent 2 hours now searching the topics in the forum without finding a solution. The only post I’ve seen mentioned something about adjusting settings for the laser timing for the direction of travel, or selecting a unidirectional raster. I don’t believe that’s an option for the programs I’m running…Any ideas?

Hi, could you provide a picture of the double imaging?

This is a rough one, but the only one I got. I didn’t waste time sanding the wood first, so that’s why it’s a little rough. You can see where some of the letters are crisp and the others are doubled…

Ok, a few more questions then:

  • Is the tree and leaves engraved as well and if so do you notice any issue with them? Hard to tell from the picture.
  • ~ how big is this engraving?
  • Are the boxes around the letters raster engraved or are they vector engraved?
  • Do you have an air assist?

Everything was rastered except the boxes around the initials, I vector engraved the boxes. The entire engraving is 6.5 x 6.5 inches square. Yes I have air assist.

Alright, so notice on the vector engraved boxes you don’t see doubling or ghosting, but you do see that on direction change the line wiggles. Like when it goes from from the x direction to the y direction.


This means that something is loose and it’s causing the beam to move. Typically this is cause by a loose carriage for the laser head. Check and see if the carriage is loose and if so you can tighten the wheels. To tighten the wheels typically the front two wheels are eccentrics, meaning the wheels are not attached to the center of the posts. So loosen the grub screw on the posts and rotate the posts to bring the wheels closer to the rail. They don’t have to be super tight, but if you turn the wheels by hand you should feel some friction against the rail.

You could also have a loose mirror or lens.

Ghosting can also be cause by a cracked mirror or lens and also by internal reflections in the laser head especially if the beam is clipping the edge of the air assist nozzle. Don’t assume the beam is perpendicular after the 3rd mirror even if it’s hitting the center. You can place a piece of tape on the bottom of the air assist nozzle and do a test fire to see if it’s exiting cleanly.

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Does it do the same thing (double) if you use other smoother materials.

Thanks! I will go through everything and check!

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Also, when you do the mirror alignment check do you get a single spot on all 3 mirrors?

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I went through and tightened everything, rechecked laser alignment, found I was getting a double dot in some spots doing the alignment. I cleaned the mirrors. slightly better result, but still not right. My air assist is a home made job, it isn’t a cup that the laser travels through… Maybe my mirrors are junk, they are the originals. I did a run on some 1/4" plywood…

Can you provide pictures of what the spot looks like on each mirror?

Also I’m surprised the vector etch didn’t improve. How fast are you doing the vector etches? Also how fast are you doing the raster engraving?

Was the machine running fine and then just started doing this?


Also, check your SVG file. On your doubles, is there a 2nd vector under the first or possibly a 2nd layer.


So does this mean you are getting double spots on the third mirror at different positions over the bed?

Thank you everybody for taking the time to help me troubleshoot. Turns out my double dot was from a dirty mirror. The double image I was getting was due to the belt being sloppy loose on the X axis. Turned the tension screws a little bit, now my image is coming out perfect.


Excellent. Thank you for letting us know the solution to your problem. Will likely help someone else in the future. :slightly_smiling_face: