Well the unthinkable happened.  My K40 fouled up.  I’m not sure what happened but my working theory is that my accidentally dropping the laser tube door really hard caused a retainer to fall out, which in turn released spring tension on mirror #1.

Retainer and Spring on Mirror Assembly

Laser beams were firing all over the place.   The dreaded realization came to me that I had to do a mirror alignment on the K40.

Okay, I removed the #1 mirror and reinstalled the spring and retainer and remounted it.

To my surprise I got it back real close to where it was just by using a sharpie to locate orientation.

So the next trick was to forget about mirror #2.  I think most folks try so desperately to hit the middle of mirror #2 that they drive themselves to the point of insanity.

What you want to do it take some card stock or use a sticky note to put in front of mirror #2.  Then you want to make sure the bounce off of mirror #1 is PERPENDICULAR to the gantry.  Forget the mirror 100%.

Once the beam is perpendicular you then move mirror #2 to where the center of that spot is.  The mount will move right and left but you might also need to raise or lower mirror #2.  In my particular case I was able to hit the middle of mirror #2 but it was low.  I had to add some washers under the inboard screw of mirror #2 mount because it fired good close in but low far away.  It’s a pain in the ass, it really is.  I added one washer at a time until I settled on 3 washers.

In a nutshell, and to be kind, this machine is fucking imprecise as hell.  It isn’t level, it isn’t square.  It may have been at the factory or even the receiving and shipping point but it may have drifted in shipment.  Mine arrived PERFECT.  Until that retainer fell out.

Another problem is there are three thumbscrews on each mirror and Nobody but nobody tells you in plain fucking English what screws does what.   Okay, yeah they do but you have to visit 4 websites and see 4 different explanations and then you go………”Ohhhhhhhhh”.  It’s pretty simple.

Thumbscrew controls

Once your mind processes which way the beam will move when you turn which screw………….you’re in there.

The goal is to hit dead center of mirror #3 no matter where the gantry is.  Close. Far. Top.  Bottom.

But just remember this.  Your useable area is about 230 x 320mm.  My rear right corner would not quite hit dead center on a scorch test BUT I CAN’T BURN UP THERE ANYWAY.   My gantry might need a little tweaking in squareness or height but at the end of the day the USEABLE AREA FOR CUTTING AND ENGRAVING IS DEAD CENTER.

Translation:  Don’t expect perfect on an imprecise device.  I dare say my mirror 3 hits are dead center EXCEPT in the rear right corner which is out of the useable area anyway.

The K40 simply is not built to tight specifications and I suspect some get better than others.  Still you should be able to perform a good alignment by understanding the thumbscrews and just working on getting a perpendicular beam and then putting the mirror in the path of that beam. Again you may have to move the mirror A LOT or make it higher or lower but you should be able to do it.

In short before you start twisting shit understand what screws adjustment moves what and that you need to work laser to mirror 1, then mirror 1 to 2, then mirror 3.  Work one step at a time. Once once alignment is right DO NOT GO BACKWARDS.  Always work forwards.

In the end I nail DEAD CENTER in my machine IN THE USEABLE AREA.  It gets off a little bit on the extreme edges.  In my case I choose to live with it, rather than do major surgery.  Also, I swear to God, I can nail it center mass at 9PM and at 5 AM it is slightly off.  Obviously there is some expansion and contraction going on here.

Don’t expect perfect results from an imperfectly made machine with sloppy tolerances.  I’m happy with my results.  My burns and cuts are predictable and consistent.  That’s what you really want.