Inconsistent line scoring results

Hi guys

I have been cutting and doing line scoring on 4mm oak veneer sheets for many years on a flux 50w laser with a 2 inch lens. The wood warps and can be out of focus by quite a few mm in the middle compared to the edges even after pinning it down.

This has never been a problem when scoring/line engraving and the lines were always consistent.

However we recently got a 80w mantech laser with the same 2 inch focus lens but the variations in line thickness when the wood goes out of focus is a lot worse.

If the sheets are out by more than a few mm the lines become so blurry even when it is only 1-2mm out when doing line scoring.

I can’t understand why this is the case when it is the same lens and the same wood?

Is the bed on the Mantech nice and level? I would also try a ramp test just to double check that the focus spacer you are using is correct at the Mantech.

There is always the option to switch to a 2 1/2" focus lens which will allow you a few mm more “grace”.

Or, it may help to cut all the shapes out first and then place them in a jig for engraving - extra work I know but they might then sit flatter?

I prefer not to use the term level, as CNC machines work fine on the Space Station …

What level helps with, is humans… it’s easy to put a level on the machine, but it has to be off enough for you visually see it with the standard level.

It should be clear that level isn’t a requirement.

What @NicholasL is driving at, is that it’s required that the machine be 3d square within it’s working area.

Sometimes a level is handy in helping you determine a problem … as long as you’re on terra firma, which is ok for most of us :man_shrugging:

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

If you have these three they work… any anomalies of poor performance can be any or all of these, but is very likely at least one of them.

Start at the beginning with a TEM00 mode check of the tube.

If you have a good tube, then follow with an alignment check/align… then a ramp test as @NicholasL suggested.

The depth of focus (dof) of a 2" lens is about 2.7mm (spot size is 205 microns) – a 4" lens is about 11mm (spot size is 410 microns).

This is based on a 6mm beam input, your 80W may have a larger beam resulting in a smaller dot or spot.

Good luck


Yes, when I say ‘level’ in that context - I mean “is the workbed level with the laser nozzle”.

Check that your focus height remains the same from the laser nozzle to the knife blades (or whatever workbed you are placing the veneer onto), check in all four corners of the workbed and through the middle both ways (9-point check) if you want to be thorough.

So the bed is level, I have checked this out.

I think I may be closer to the answer, so I did some test line scores. Top left and then middle and bottom right.
The focus height was the same in each area, but the top left looked out of focus, middle was perfect and then bottom right was blurry too.

So I decided to check the mirrors, First and second mirror are spot on and in the middle.

But when I do the check on the laser head (before it hits the mirror) I notice that the top left and top right were out.

Middle left and middle right were perfect.

Bottom left and bottom right were out.

See attached images.
Imagine the grey is the laser bed itself and then the checks are done left to right.

Would this point to a X or Y axis rail that isn’t level?

If these are done as per your graphic, I don’t see how it works at all in some areas. Am I misinterpreting what you’re showing?

It looks like you need an alignment.