When aligning the optics… I do it slightly different. I thought it would help to “level” the tube (a step they wait until you get to the third mirror) early… I’ve learned you can’t move that up and do it earlier unless you are already close to a good alignment. When I check mirrors 2 and 3 I first take a shot at the tape in the first position (like for mirror 2, at position A). Before I put the tape on the opening before the mirror I mark it as “A1” (for my first attempt at “A”. I also use a pencil and put write on a crosshair that I try to tape pretty close to the middle of the hole. Precision of the cross hair is not critical but you want a reference later for when you compare the hole to where it would have been desirable. This tape I place with the long edge of the tape vertically with respect to the machine. After taking the pulse at “A” I leave that tape on and put another tape marked “C1” (for my first shot/attempt at position C) again with a hand drawn cross hair approximately the horizontal and vertical centerline. This tape I place with the long edge horizontally to the machine. I then take the pulse at position C. Now I have an overlapping set of tapes where I can easily distinguish the shot at position A from the shot at position C and by marking them A1 and C1, A2 and C2, etc., I can see my progress (as I remove both tapes at once and tape them to the bottom of the cover glass. I’ve found that after a couple or three attempts I draw a freehand crosshair that is pretty straight/90 degrees and I am able to place it very close to the center of the portal to the mirror. Having the line of a half cozen or even more tape pairs at position A, C MidLeft, MidRight, MidMid (or however you want to label them) is very helpful. Moreover, you can observe the “type” of the hole at the different positions. Twice as I’ve gone through this process I would find I started with a really nice round hole, that as I continued and got further away from the laser tube would become an oval and even resolve into 3 smaller holes vice one large hole. (That is a good indication your tube is almost dead). If you’ve aligned optics 6 or more months ago, the current recommended process is somewhat different and probably better. I’ve also done my best to try and have ALL the holes light up somewhat close to the centerline of the mirror and just slightly above the vertical center. If I can get very close to identical holes at A, C, MidLeft, MidRight, and MidMid I feel better than if my A is a little low/left, the C is high and right, the MidMid is somewhere in between but the MidRight is different from everything before it. It takes a little longer but I’m much, much happier with what appears to be a much more consistent burn/results. And, while you/we are at it… do NOT forget to ensure that your honeycomb table is level. A 3mm difference in focal length from one part of a burn to another will really muddy up your results. If you are not level you have to remove the rubberized timing belt and adjust each of the four corner tray supports. That is also tedious, but worth it.
Now, what I don’t know but intend to experiment with someday is how does one go about cutting a 5mm, an 8mm, and a 10/12mm thick workpiece? The ideal focal length is 12mm from the bottom of the focus lense housing to the workpiece. But what if I’m cutting an 8mm workpiece and it take 2 or 3 passes? Should I raise the table the 2-4mm after each pass to keep the ? Anyone have experience with this?