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Doug Griffith
11-25-2009, 4:07 PM
I just thought I'd share an alignment issue I decided to fix on my Epilog. It may only matter to cutting jobs that require precision fitting of parts but it's something you might want to do. The problem was the beam not being exactly perpendicular to the table. It caused cuts through thicker substrates to be at a very slight angle (beyond the kerf angle). The way way I fixed it was to:

1) draw a dot on a piece of paper.
2) move the z axis as high as it can go without hitting the air assist tube.
3) align the dot with red laser pointer.
4) move the z axis as low as it can go.
5) loosen the lens assembly and align to the dot.
6) repeat up and down until there is no variation.

My machine had .250" variation between the max up and down positions.

Bruce Volden
11-26-2009, 11:20 AM
Good tip Doug!! I'll be checking mine.

Bruce

Dave Johnson29
11-26-2009, 2:50 PM
The problem was the beam not being exactly perpendicular to the table.

That might be an intentional engineering design function. It would prevent a direct reflection of the beam back to the beam path. On my lasers, I intentionally built the beam 1deg off perpendicular for just that reason.

Richard Rumancik
11-27-2009, 12:18 PM
That might be an intentional engineering design function. It would prevent a direct reflection of the beam back to the beam path. . . .

It suspect it is mostly an alignment issue . . .it is not that easy to get the beam hitting the center of the lens in the four corners of the table, nevermind maintaining perpendicularity as well. The Epilog seems to enable aiming the beam at the last stage, which sounds like a good feature.

My Mercury does not allow any aiming of the beam at the carriage itself. All of the aiming has to be done by the first 3 mirrors. Personally I think this is not the best design approach as you can't compensate for errors in the carriage assembly by adjusting the first 3 mirrors. The last mirror should be "45 degrees" to the table. But what if it is 44.5 degrees like mine? I use a mylar shim under one ege of the mirror to tweak the angularity of the last mirror around the y axis. But I can't easily tweak the other axis with these mechanics.

Reflection is not likely to be a significant problem unless trying to mark very reflective materials at slow speeds which most people aren't doing. With stainless and Cermark, the material is no longer reflective. Most other "reflective" materials lose their reflectivity the instant the beam hits it (eg coated plastics.)

Way back when I was trying to mark stainless directly (no Cermark) I contacted Synrad and they did not seem concerned about the reflection back into the tube. But they said that if I was worried I could place the workpiece at a slight angle. But they didn't seem worried (and it is their warranty.)

(BTW the direct marking of stainless was not very successful - like other people have reported, I found that you have to go too slow to make any kind of mark at all and it is not suitable for decorative applications.)