Omtech K40+ Cannot Cut Thru Material

I’ve got a new Omtech k40+ with Lightburn. I’m a Lightburn newbie but I managed to get it set up correctly…at least I think. I did a ramp test to find where my focal length should be and I think I have that set correctly. I’m trying to cut 3mm/.118" thick acrylic with 1 pass and I’m unable to do it even at 100% power/19mA at 7mm/sec. I’m not sure what’s going on. On my other k40, using k40 whisperer, I can cut 3mm acrylic at 9mA with 1 pass all day long. Could it be that I have something misconfigured in Lightburn? I don’t understand what is happening.

My mirrors are aligned. I double checked those again. My mirrors and lens are clean. Air assist is working. When trying to cut at 100% power, I do see the meter read 19mA. Everything appears to be working. It’s just not cutting. It’s likely something obvious but I’m not seeing it.

The odd thing is when trying to cut acrylic, it’s only penetrating about a 1/4 of the way through. It’s like I’m starved for power. Any thoughts?

  1. properly working tube
  2. clean and aligned optics
  3. proper focus

If you have these three, they work.

If you’re sure about the focus, that only leaves two…

When you did the alignment check, did you look at the TEM mode of the tube?

Suggest you don’t run 100% power, especially when you have a technical issue… 19mA could be a bit hot for these…

Good luck


  1. properly working tube
    Before I turned on the laser, I followed an instruction booklet that wanted me to disconnect the red wire from the tube and the black/blue wire from the tube and connect that up to a large resistor. Then it wanted me to press the test fire button and read the milliamp meter on the unit. It appeared ok but I didn’t really understand what I was suppose to see if it was bad. So…I wired it back up like the instructions told me and away I went.

  2. clean and aligned optics
    I believe my optics are cleaned and aligned. I checked all places on the gantry and I’m hitting nearly in the center of the mirror holes. I also slightly shimmed up the corners on my honeycomb bed so my z height was the same on all places on the gantry.

  3. proper focus
    I believe I have proper focus. The unit came with a small acrylic focus gauge with no instructions on how to use it. I made an assumption and I was right. As a double check, I conducted a ramp test and the finest line is the same height as the acrylic lens height gauge. I think I’m good there.

So, I guess that leaves me with the tube. I guess I can’t say if it’s good or bad. I’m not sure how to check for that. I will take your advice and back off of 100% cutting and move back to 50% cutting until I get it sorted.

I also have a support ticket in with Omtech. They want me to shoot a video and send back to them. I’ll do that as soon as I can.

This is basic ohms law… so much current for so much voltage… Since you didn’t give us any values…?

What did you read and what was OMTech advice on what it should be?

Did you do a TEM00 mode check?


Well, Omtech wanted me to record a series of videos for them. I did that and they determined that I have a bad tube. They are shipping out a replacement. I’ve not installed a tube before so I guess I’ll be hitting youtube.

It’s not rocket science… I’m sure you’ll do fine.

My replacement came with both anode (hot) and cathode (ground) wires already connected to the tube. I have a hv meter on mine, so it already has a hv connector.

Put the hv connector on the anode and wired the cathode back to the meter.

The pair of white connectors are visible in the back. One to the lps, other to tube anode.

Then it’s alignment time…

Have fun :wink: