My K40 has arrived. Notice anything glaring?

Do you have an air assist? An air assist is critical to prevent flare ups, especially when cutting paper.

Doesn’t take much for paper. When cutting construction or cardstock weight paper I usually set the power at or close to min (~4ma) and the speed at 25-30mm/s.

For 3mm plywood you are typically looking at around 8ma at 10mm/s.


I have a compressor and house. I am waiting for the chain to come from Etsy. I don’t think I thought about what you of his to use for it though… Should it be silicone or pvc?

This was the first non-test file that I tried to cut. I did not have the setting correct. This was post alignment. Any idea why there would be ghosting? Everything is stock right now.

The beam reflecting off something like the side of the objective lens tube.

Could it be reflecting off the bed itself? It is basically a sheet of mirrored metal.


The lens narrows the the beam down to a point but the other side of that point it just keeps widening indefinitely. The beam is not collinear after the lens. See the schematic side view in the intro topic to visualize it. Even if it reflected off the bed perfectly, it would be spread out enough by the time it bounced back not to burn. You can try engraving cardboard rather than paper to see that it’s coming from above and not below, if you like.

It’s quite common for the beam not to be centered in the tube and to bounce off the edges of the nozzle.

See the videos that American Photonics made to describe their 3rd mirror alignment tool which demonstrate why it’s easy to have the beam not concentric with the tube.

But also, have you checked for belt tension and for play at the wheels?

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Thank you. I tested again on a piece of leather. The ghosted line is when the laser goes back for a second pass at something (not as in I told k40 whisperer to do two passes, it just does it itself). Is it possible that my stroke width is the issue?

Testing again

Raster engrave: 4mA at 100mm/s
Vector engrave: 4mA at 20mm/s
Vector cut: 4mA at 10mm/s (10 passes), 14mA at 10mm/s (1 pass)

I masked the whole area. Engrave went well enough. I was just testing it out. Even with all those passes, leather still wasn’t cut. Not a big deal. If I remember correctly this is pretty hefty leather (3mm thick I think). I cleaned with soap and water.

If it’s going back for a second pass it’s probably the file. If you post the file some of the K40 whisperer people can take a look.


If I forget jerusalem in hebrew

It appears that you have 2 sets of blue lines in the image. Each blue line is actually composed of two lines that are offset from each other by the width of the lines. I think this is why you get a double cut. I’m not a strong inkscape user so I’m not sure how to tell you to fix it. @Jammy?

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Yeah I can take a look, but its 11pm here - and chill time!

I will sort it tomorrow if its still unresolved :+1:


Ok, I think I got it. Had to select the outer line and delete it.

If I forget jerusalem in hebrew 2


Thank you! I am new to Inkscape. I have illustrator but am more of a photoshop user. I will have to get this all figured out. Does the stroke width make a difference? I increased it so that I could see it more easily.


No, the stroke width doesn’t matter in K40Whisperer.
So I figured out to get inkscape to show me the objects in the file. Not very obvious Object—> Objects. :wink: If the object window shows up on the right side group, click/hold/drag the object window from there into the middle so it’s a free floating window you can resize. Let’s you see all the objects in the file. In this case there was a double set of lines (path28-5) and a single line (path26-7). I deleted path28-5.


@NedMan that fixed it 100%. Thank you!


Here is my first complete engraving on Baltic Birch plywood. It is for my son, who loves hippos.

8mA raster engrave at 100mm/s.


Good to see a fellow laser crafter up and running :+1:


Looks nice, good work! :slight_smile:


This one is for one of my daughters. I decided to vector cut it at the last minute. I had two spots where it didn’t quite make it all the way through. I should have let it go more but I didn’t realize it wasn’t cut before I took it out. Still turned out ok for my first time cutting plywood with the K40.