Age old Alignment issues

My mirror 2 is in the same spot front to back, mirror 3/entry to mirror 3 is at the same spot in all 4 corners. However my head and entire head assembly is HOT all over, too hot to touch in fact.

No cutting power.

Mirror 3 is clean, the beam comes central out of the nozzle but am assuming its bouncing about all over the place before it gets there.

What can I look at as being the issue? Very frustrating!

The tube is a brand new 60W

It’s likely not bouncing around too much. If I had to guess I’d assume that the light beam is getting clipped from M2 to M3.

Note that the shape of the opening for M3 may not be exactly where you think it is. In that case, you may not be aiming the laser directly at the sweet spot of M3. I’d suggest removing M3 to get a really good lock at what you’re aiming for and adjusting accordingly.

What @berainlb states…

This is my China Blue head… notice the hole is not centered over the mirror…


A good alignment starts at the tube to evaluate it’s output… good chance it’s fine, since it’s new… start there and check for TEM00 resonance mode…

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

If you have these three, they work … which one are you missing?


If the head is getting warm, you’re probably missing number 2 in the above…

Good luck

:smile_cat:



I have a feeling this has something to do with it. I maybe have my tube sat a little low.

Number 2… :face_with_spiral_eyes:

On an alignment, start at the beginning and when you get to the end stop…

Sounds/looks like you have a handle on it…

Good luck

:smile_cat:

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I hope I do, thinking of raising the tube by roughly 5mm and see where that leaves me. I will get this machine up and running! Tube and PSU are now brand new so…fingers corssed.

You don’t need to blast a hole on the target when doing an alignment… This is one of mine from m2 with two strikes… notice you can see each individual pulse, near and far…

I use watercolor paper and cut my targets out… easy to singe and read…

:smile_cat:

Nice idea, I’ll maybe have to cut some with the other laser!

Just 3D printing some stand offs to lift the tube. The old tube was a ‘real’ 60W tube as 1200mm whereas the replacement is 1000mm and somewhat more narrow too.

Most of these 60W are 55mm in diameter… next size down is 50mm, so I’d think 2.5mm would be right…

Did you measure the correction…?

Good luck

:smile_cat:

Lifted the tube 3mm and things are loads better. Just cant seem to get the beam to be centered at the nozzle, even though it is before the lens

If I interpret this correctly… you claim the beam is center in the tube, but it comes out of the lens and hits the nozzle?

If center means parallel to the tube and centered in all three dimensions…

If so, it has to hit the center of the lens…and come out the nozzle…

What kind of head is on your machine? Can you remove the nozzle and the down tube?

How did you know it’s centered in the tube?

I don’t know how this could be with your tube 3mm low … unless you lowered the mirrors?


Keep in mind that we see an 18mm mirror as a circle of 18mm, the beam sees it at a 45 deg angle, so in one axes it’s 18mm and on the other it’s around 12mm…

Me thinks you still have alignment woes…

:smile_cat:

I agree. It all starts at the tube. A hot focus assemble, particularly the laser exit tube can mean that the beam is slightly touching the exit area.

Make sure your laser is on jack feet, not casters. Casters can cause the laser cabinets to warp as it is rolled back into position on a uneven floor and cause the tube to no longer be aligned with the mirrors. This means you may have to have adequate space to service the rear of your laser engraver.

The tube needs to be absolutely level in regards to the XY axis. Mirror 1 is fixed and you only need to get the dot in the center of it. If your tube is misaligned you will have a difficulty in getting dot on dot during your alignment going from mirror 1 to mirror 2. Usually, if the dot is hard to adjust for dot to dot, then the rear of the tube either needs to raised or lowered. Start the testing with mirror 2 in the middle of it’s travel. A correctly aligned tube will hit the same dot at both ends of it’s travel as in the middle.

Next you need to align the mirror 2 to mirror 3. Again, put the mirror in the middle and adjust the dot for the middle of mirror 3. If the dot moves when going from one extreme to the other of mirror 3’s travel, then you will probably need to move the rear of the tube left or right to get dot on dot. Once this is dot on dot, adjust mirror three.

To adjust the focus head and mirror 3, put the focus head in the middle of your XY work area. Proper adjustment mirror 3 will give you perfect beam going through the lens and the exit tube.

If you go back and test where the dot is on mirror 1 now, you may find (probably) that the dot is no longer in the mirror center. This is because you have been moving the back of the tube up and down and left and right. This is not really important if all other dots are dot on dot. If you have to have the dot on mirror 3 directly in the center, then you will either need to raise or lower the tube assembly (front and back) and also move it right and left (front and back) until it is the center. Then you need to do the whole alignment all over again. However, the dot not being directly in the center of mirror one is not really that important.

This should get rid of a hot focus tube due to the laser beam touching the focus tube and should also get rid of hot and cold engraving spots on your. You may also find that you have more engraving power and cutting power now.

This is how I go about it and it works well for me. If anyone sees an error in my process, please feel free to correct me.