Lasers and Horseshoes and grenades

[FanFan]

Hello!! Today, I was talking to someone about lasers and aligments of mirrors. I don't have much experience in this area. I was going to get a demonstration of a "horseshoe" alignment. I got part of an explanation about what it was about. But then I was told to go work on another piece of equipment. So I didn't get full explanation. I didn't understand why part of the alignment was called a horseshoe alignment. From what I could figure out was, when a series of mirrors are used to direct the power laser beam on to a particular spot on the part that there are a various positions that the shot can be taken from to hit the same spot. If those various positions are used then the laser is suppose to hit the spot...dead on. If they don't then the alignment is off. The mirrors ( the planes that they sit in) need to be adjusted. What does horsehoes have to do with this? Is this a horseshoes and grenade solution to the problem? Just have to be close. I suspect not. Or maybe the alignment is that difficult one might think about using a greande. I hope not. What's the real story?
FanFan

[underthetire]

I'm guessing he was going to teach you a rough alignment. I've never heard of horseshoe alignments.

You want laser alignments check this out
YouTube - Broadcast Yourself.

[FanFan]

Underthetire, Thanks for your reply. Initially I was puzzled by your reply. I thought the link you gave me was going to take me directly to laser alignment videos on Youtube. Well it kept taking me to a page that was listing little kids talent show competitions. Yes I tried that link 6-8 times. Dahhh... The lite bulb wasn't coming on. Today the light bulb came on. I put "laser alignment checks" in the Youtube search box and it worked much better. Didn't find anything yet but you pointed me in the right direction. I am getting a lot of laser automotive alignment videos.
I was talking to a co-worker about the horseshoe test. He has seen it done a couple of times. The lasers that we have at work has 5 or 6 axis. The part is put on a rotary table (C axis). The laser head can be moved in 3 basic directions. X, Y and Z. And then the swivel head can move in 2 or 3 rotary axis. Sorry we are offsite from the company for some training so I can't see the machine so I am not sure how many rotary axis are in use.
The way I understand it is that for for each axis a set of mirrors are used to redirect the laser beam to the part. If those mirrors are not properly aligned ( basically not parallel to each other in two planes) the beam will not repeat itself. The term horseshoe comes into play when the shots are taken at the same spot on the part from three different positions. Those three positions if graphed are located around the part in the shape of a horseshoe. Sorry it is hard to verbalize the process. If I could do a drawing ( or a video) it would probably be easier to visualize.
....,..... O.....

. X ...... ......... X





......... X......




The "X" represents the part and the "O's" represent the positions of where the shots are taken from. If the mirrors are not aligned properly then the hole formed would not be round, the 3 shots would cause the hole to be oblong. At least that is the way I understand it works. I am used to machines that positioning in two linear axis, not 4 or 5 axis that include some rotary axis. I suspect those articulating robotic arms may have similar issues.
Thank again.

FanFan