Diagnosing Laser Cutter Alignment Problems

I’m writing this because it appears we’re not the only ones to suffer from this problem, but there’s little information out there, and it initially had most people I asked completely baffled. Martin Raynsford suggested the problem was most likely more widespread than I thought and that it’d be really useful to get what I’d learned out there for the benefit of everyone else, so here we go.

We were suffering from strange variable power issues on the laser cutter. In some places it would cut with no problem at all, in other areas of the bed the power seemed to be far lower.

By adding a spot of tape to the mirrors on your laser you can see exactly where the beam is aligned by firing some test shots. You should start from the mirror closest to the laser tube and work out to the final mirror before the focusing lens. Out cutter showed the alignment was good right up to the final mirror when everything seemed to diverge. If you fire a test shot near each corner of the bed you should get something like this:

Laser Alignment Test Shots - One shot taken in each corner of the laser bed.

Taking a closer look at the end result we can see that 3 spots are clustered together and nicely central within the aperture in front of the final mirror, but the fourth is very low in comparison – this will lead to a reduction in the laser power at the front right of the bed:

The results of the test shots.

Since everything runs on rails it’s not possible for the laser head to actually move up and down (in this case it’s too high, resulting in the low appearance of the spot) so what’s the cause of the change in alignment? It turns out the desk on which the laser sits has bowed slightly under the weight of the laser cutter resulting in a slight twist to the entire machine – so it’s not the laser head that’s high, it’s the entire front right corner of the machine.

The solution is surprisingly low tech – put a wedge under the appropriate foot to neutralise the twist, and re-check your alignment, you should find that things are improved, you may wish to experiment until you’ve got everything nice and square.

Maybe adjustable feet would be a useful lasecutter mod.

Hopefully this will save people hours of headscratching trying to diagnose similar problems. Happy laser cutting!

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6 Responses to Diagnosing Laser Cutter Alignment Problems

  1. Paul Brook says:

    Maybe an even better solution is to use a desk that can actually support the weight of the laser cutter.

  2. Michael Chang says:

    Hi Jon,

    What kind of laser cutter did you use. It’s my first time buying my own and have read blogs about the prices like this one: http://www.lasercutter.co/laser-cutter/laser-cutter-price/close-up-on-the-laser-cutter-price/ and boy! – they are not cheap.

    I want to make the most out of my bucks so I think I’ll go for steel rod based design instead of v-groove bearings on tracks because I think the former is much studier, what do you think?

  3. Albert says:

    Hello – Im hoping i can get some Help we bought a Full Spectrum Laser Pro- about a month or so ago and to this day we can not get the alignment right – one day we were trying it out trying to align couldnt get an even burn deeper on the left side than the right – well we gor frustrated left it for another day — well when we went out a few days later to try it again did a practice cut – and wouldnt you beleive that it wastnt cutting at all no laser at all was working with no laser coming out it was moving like it was workig but wasnt cuttung anything — tried again to adjust alignment still couldnt get it this is so frustrating dont know what to do called tech support at company – they have been trying to help but nothing as of yet– we are in desperate need of help and guidance — not sure what is going onn this was a pricey mchine and for us to be having such problems is crazy — i would really appreciate some kind of help

  4. darryl says:

    Hi I read your info about mirror alignment, I am having problems with this. I center the laser to the first mirror, then bring the second mirror up close and center, when I move the mirror back to the front the beam moves up and towards the left side of machine? Any ideas?

    • jon says:

      Error will increase with range. Try aligning at max range and see if that helps. If you still get too much variation as the mirror moves then its highly likely the machine is warped.

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