Laser not centered out of nozzle

I’ve gone through the steps multiple times before of aligning the mirrors on my K40, but I still never really got clean cuts like I think I should.
Just today I realigned again, and everything hits directly in the center of each mirror at all of the locations (I did have to shim a couple of the mirrors slightly).
However I didn’t think of checking the laser out of the nozzle before, until today. And I found that it’s coming out almost exactly at the very edge. I’m assuming this would cause a problem, especially if it’s actually hitting the edge a bit and losing power or reflecting a bit.
So my question is this: How do I actually align the laser coming out of the nozzle when all of the other mirrors are aligned and centered?

Since the 3rd mirror is not adjustable the beam has to be placed in the right position on that mirror entering parallel with the x carriage movement.

This is one of the most challenging adjustments as it may require changes all the way back to the tube and including the tube.

I suggest you start with one of the alignment procedures given on this site and pay attention to the placement and direction the beam has entering each mirror.

Before you realign open the head and ensure that your lens is clean. Ensure that it is installed properly and there are no cracks or scratches.

Thanks, Don.
I have double checked both the 3rd mirror and lens for scratches/cracks. Appears good to my naked eye.
I definitely have followed several alignment tutorials. What do you mean exactly by “pay attention to the placement and direction the beam has entering each mirror”?
Is ensuring that it hits center on each mirror at each location not sufficient?
Thanks again.

Perfect alignment means that the beam enters the mirror both parallel to its x & y imaging axis and on the mirror center.

By the time the beam gets to the 3rd mirror you do not want it entering the mirror at an angle otherwise the reflection downward to the lens will be at an off angle and not hit the lens in the middle.

Most alignment procedures are set up to help make sure the beam is running parallel to the Y and then X as the beam folds from 2 to 3.

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I’ve followed that tutorial, which is a really good one.
And the laser isn’t quite so near the edge as it leaves the nozzle anymore, but definitely still not centered.
But the fact that it has moved some is a good sign.
I’m just not sure how to continue improving that exit alignment without being able to exactly measure the angle of the beam itself at the other mirrors to ensure it’s 90deg.
I do have a carpentry square that I used to make sure the bracket the nozzle is on is square with the x-axis gantry, but it’s probably the other mirrors I’m more likely to have an issue with.

If the beam is square, you will get the same witness marks with the head positioned at each of the four corners. The process in the documentation describes how to make it square: You measure by shooting the laser, moving the gantry/head, and shooting again, and looking at the witness marks.

From one of our #lasers:co2-intro articles:

Note that if the third mirror does not align the beam with the middle of the lens, the beam will not be focused correctly and will not be aligned with the hole in the nozzle. You may wish to use a device that helps you align using a red visible laser. […] a tool used only while performing alignment

This allows you to work backwards from the head using a visible laser beam. It might be substantially less frustrating for you.


I may just have to look into an alignment tool like that.
I’ve been working at this for hours, but that final mirror is making a lot of this guess work.

The problem can also be that the laser head or the 3rd mirror is not perpendicular to the beam in either the y and/or x direction. This causes the beam to angle out after the 3rd mirror. You can try rotating the head slightly to see if you can center the beam in the nozzle. Place a piece of tape over the end of the nozzle and do a test fire. For easy visualization place a small mirror under the nozzle after test firing and then shine a flashlight through the mirror opening.


Thanks for all the comments everyone. It’s working considerably better now.
Still not centered on the lens when it exits, but much closer, and is cutting better.
I don’t know if this is the best I can get with the default brackets and mounts on my machine. There’s only so much movement they provide.


Check out this video…
K40 - Head - Adjustment Screws

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That’s really great, thanks for sharing. We’ve been needing something to make the head adjustable. :smiley: