Where to hit the mirror?

Discussions on optics for laser cutter/engravers

Where to hit the mirror?

Postby bloq » Fri Jun 05, 2015 7:04 am


i am in the process of making the mirror alignment for my laser (with a laser pointer) and before i start i would like to ask the community. I found lots of information and some of the are inconsistent regarding where the beam has to hit the mirror. I found information which says that it does not need to hit the middle but it has to hit in the same place on the different mirrors (whatever this means). Other information sources talk about the exact middle of the first mirror. Lasersaur writes something from the exact middle plus some mm to the top. It is a little bit confusing and i would love to learn from people who already made their lasers fire...


Posts: 88
Joined: Mon Dec 29, 2014 9:15 am

Re: Where to hit the mirror?

Postby rsm5178 » Fri Jun 05, 2015 11:49 am

I would say it is best to hit as close as possible to the center of the mirror. The laser beam has a width, so you want all of that width to hit the mirror. Also, it helps with the slightest bit of misalignment (more room for error down the beam path). My beam path is not perfectly centered to the mirrors but it is perpendicularly true and thus good enough for me.

Make sure you test your alignment across the entire bed. Remember that you have X, Y, and Z axis to align. I had to drill out my lens carriage plate and my left gantry bracket slightly to have a perfectly perpendicular beam path on the X and Y (because of my optics choice). I also had to shim up the second mirror as well as the 3rd to make my path planar (no Z).

For alignment, I made discs to put into my tube holders to hold a laser pointer. The laser pointer is furthest from the 1st mirror. A disk with a pin hole in it was in the other tube holder to condense the beam and make sure it's centered. A bunch of people have used this method and I assume the route you're going. Definitely helps a lot over the tape method.

Posts: 119
Joined: Tue Jul 23, 2013 9:57 pm
Location: 19425

Re: Where to hit the mirror?

Postby JamiesonLaser » Fri Sep 25, 2015 2:54 pm

I prefer the tape method when aligning my mirrors only because the red dot pointer can be misleading. And yes, the beam should be close to the center but does not have to be perfect. As long as the laser hits the same spot in all four corners of your cutting bed and it is relatively close to center I am usually happy.
Posts: 1
Joined: Mon Sep 21, 2015 7:21 pm
Location: Litchfield, CT

Return to Optics and Lasers

Who is online

Users browsing this forum: No registered users and 1 guest