Aligning 40 Watt laser mirrors, without burning your eyeballs out…

by Stephen Hobley on May 5, 2011

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Since the laser cutter has a fixed tube, and “flying” mirrors – it’s critical to get the alignment right over the full range of gantry movement.

It occurred to me that if I could actually *see* the path of the laser, it would make mirror alignment a whole lot easier.

Video also features my $25 air assist mod…

Getting the LED in the exact center of the laser aperture is more a matter of trial and error, but after just a few minutes fiddling I got the placement right.

Here’s an image showing really good placement – the LED is right in the middle of all mirrors. You want this kind of thing all the way through the full range of gantry movement.

Aligning the laser

It turns out that the gantry is poorly constructed (there’s a surprise!) and out of true – almost everything comes out as a parallelogram. So… it will need to be replaced. I’m currently figuring out how I can adapt my previous CNC gantry for laser cutter operation:

New Laser Gantry


{ 5 comments… read them below or add one }

Jelle May 8, 2011 at 3:43 am

Hey, that is a pretty smart trick! but since your webcam is not truly parallel to the laser, how do check that alignment? Or is it just a matter of aiming the laser to the middle of the first mirror with painters tape, and webcam aiming from there?
I’m sure you knew the trick with painters tape, but I did not see/here it mentioned.

Stephen Hobley May 8, 2011 at 2:47 pm

Yes I’ve used the painter’s tape method too.

This trick shows you if the laser beam moves around as the gantry moves, something that should be minimized. I later found that by shining a bright light on the laser tube I could see the aperture in the web cam without having to use the LED.

Stuart May 9, 2011 at 6:47 am

Hi –

I found your website while looking around for a low-cost gantry router. You have some awesome stuff here!

I see that you don’t like the Bluumax, saying that it is out of true. Do you have any recommendations for a better unit? Or some thoughts about how true up the Bluumax?


Stephen Hobley May 9, 2011 at 7:31 am

Let me clarify – it was the gantry that came with the Chinese laser cutter that was out of true, the Bluumax is fine. I’m experimenting with re-purposing it to replace the one in the laser cutter.

Dickson Hoffman April 1, 2012 at 11:14 am

Did you use the z axis to fire the laser? I have Mach 2 . Was thinking about using a micro switch but there might be to much of a delay for the laser. And this might cause a over size hole during the start and stopping of the laser. Some people are using the spindle in Mach 3 and using the port 14 pin from the computer.

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