Issue with laser going out of focus very quickly on material

Hi all,

I have been having this issue for a little while now and not been able to get to the bottom of it.

I have had this issue with a mantech 80w machine whereby the line scoring thickness differs in each corner of the bed very slightly. But when the material (MDF 4mm) warps by a few mm it will then go very thick.

Attached is an example whereby the distance between the laser head and material goes out of focu by maybe 1-1.5mm.


I have a 2 inch lens which i thought had a 2.5mm tollerance for focus (maybe I don’t understand it though). My interpretation of this is that I have 2.5mm outside of the perfect focus point to stay in focus. I did a ramp test and with my nozzle it seems to be around 8.5 or 9mm.

I also checked all 4 corners of the bed and adjusted them to ensure it is the same from the bed to the laser nozzle head.

My other chinese laser is perfect though, I never seem to have issues with and the MDF material can be out by 2mm or more and it will still score perfectly fine.

Attached is a laser focus alignment video I did today. I had noticed that when going from Mirror 2 to Mirror 3 at the bed closest to me, the second pulse on the right hand side is slightly north of the first one.

This isn’t the case when you move the laser head to the top of the bed and go from left to right (it is then perfect).

Not sure if this is the route cause of my issues.

But have you ever seen when the focus thickness of scoring very quickly changes by just 0.5 or 1mm?


Hope you can help.


During an alignment, you should start at m1 and ensure the tube is in the proper resonance or mode… Check the TEM00 mode, if it’s not right it will never align properly.

I cut out targets out of watercolor paper, so I don’t have to deal with tape adhesive, plus you can evaluate the mark after you remove it from the machine.

The way you’re doing it, once removed, you can’t tell where it was.

Check it’s mode and let us know.


I don’t have a fancy mount so having to work with what I’ve got here.

Power is down to 20% did about 3 pulses.

Has like a ring to it with a dot to middle. It is a reci tube less than 1 year old.

Did a few more shots just in case at various amount of pulses.

It’s nice to have a minimum pulse to just slightly mark the target…

However, it’s pretty clear yours is out of resonance and will never properly align.

Unfortunately, the only fix is a new tube - :poop:

I’d expect more out of a RECI tube, these are pretty high quality, assuming it’s not a grade B tube … they usually have a 10k hour mtbf.

Is this the original tube?


Yeah brand new about 11 months old. For the first 3 months I barely used it as it was in storage.

Most of these, from good vendors, will warranty them for a year… might want to get on your email with the vendor and see it they will cover it… Don’t dawdle.

Good luck :+1:


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