Firing double image..... Not lens problem....??? HELP

[Jeffrey Michael Wilson]

307200OK, I have a 50 watt Chinese laser (more like 40 watt)...... when I fire matrix multiple copies of vectors (have not seen it on rasters, but I don't fire them as high) at a higher power on the last ones fired I begin to get a "shadow" burn just a little below the original. If I fire it again, it will still just double the last ones... The picture was fired 3 times, just the last half or so had the double image. It can't be a lens or mirror problem or it would do it consistently. I use Laserworks software...RDCM .... Any ideas to this new Mystery?

[Bert Kemp]

what do you mean fired 3 time , you mean you made 3 pass's on the same work area.
if thats the case it looks mechanical like a loose laser head or belt or something.Something is moving between passes

[Bill Carruthers]

This effect is often caused by the lens mounting bracket not being at 90 degrees to the table. So part of the beam hits the cone and produces a "secondary" weaker spot.
Try measuring and adjusting the lens mounting bracket in both x and y axes and also check that your beam is entering the 3rd mirror /lens holder as close to center as possible at different parts of the workbed.
Cheers & good luck.
Bill

[Rich Harman]

First, it does not make it any easier to read nor more likely to get help by using huge text.

It could be, probably is, an alignment problem. The fact that it is different at different parts of the bed just shows that there is a problem in either the first or second mirror (or both). Only if the 1st and 2nd mirrors were perfectly aligned would it be the same everywhere. If the first two mirrors are out of alignment, it is a safe bet that your third mirror and bracket is too.

[Dan Hintz]

First, it does not make it any easier to read nor more likely to get help by using huge text.

Funny enough, it did for me this morning... I couldn't find my glasses ;)




Jeffrey, this is an optics issue, so that's where you should concentrate your debugging efforts. Notice how the problem gets worse the farther from (0,0) the carriage travels? This screams alignment issue and/or loose mirror(s).

[Jeffrey Michael Wilson]

Why would it not do it on the first few....yes, 3 passes on the same work piece... and why only with high power and vector?

what do you mean fired 3 time , you mean you made 3 pass's on the same work area.
if thats the case it looks mechanical like a loose laser head or belt or something.Something is moving between passes

[Jeffrey Michael Wilson]

First of all it makes it way easier for me to read what I'm writing...my eyes are not that great. Why would it only be with Vectors, not raster. And it's worked perfectly well for some time with no changes made to any equipment.

[Jeffrey Michael Wilson]

Yeah my eyes are terrible, can't see a darn thing most of the time... Eye doctor say's,"they are clear"...Yeah dude, maybe for you, but I can't see a dang thing. So checking that the beam is hitting dead center on each mirror would be the process. Strange that it was OK, then not... And sometimes is fine, could that be because I start at a different place on the bed? I'll go check mirrors now.

[Scott Shepherd]

Why would it not do it on the first few....yes, 3 passes on the same work piece... and why only with high power and vector?

That's exactly why you are seeing it. It's misaligned optics and the power that's in the beam that's split and wandering off isn't very strong because it's entering the lens at a bad spot, so it's power is diminished. When you are rastering, it's doing it too, but the power differential is different. I would suspect if you turned your power way up and your speed way down, you'd see it in rastering as well.

[Jeffrey Michael Wilson]

WOW. Matt Dillon, long time no see. OK, so I'm checking the alignment...where you say, hitting the lens at a "bad spot"...do you mean a problem on the lens, or just not in the center..... Yeah, I had the same idea about power in the raster ... Also just looking through to the first lens after the laser tube it looks like there might be a little inclusion, I suppose this could be a problem.... I need to take the mirror out for a closer look to be sure, been trying to avoid that....
That's exactly why you are seeing it. It's misaligned optics and the power that's in the beam that's split and wandering off isn't very strong because it's entering the lens at a bad spot, so it's power is diminished. When you are rastering, it's doing it too, but the power differential is different. I would suspect if you turned your power way up and your speed way down, you'd see it in rastering as well.

[Scott Shepherd]

WOW. Matt Dillon, long time no see. OK, so I'm checking the alignment...where you say, hitting the lens at a "bad spot"...

Bad spot as in, not the optimal spot for the beam to be entering into the lens.

[Jiten Patel]

Jeffrey, it must be your eyes, those all look perfect to me?! :D

Sorry couldn't resist.

[Jeffrey Michael Wilson]

307229 OK, so checking alignment, I put tape on last mirror b4 lens, pulsed once far left upper corner, then far right.... it hit the same spot on the tape exactly...Did this on all corners and beam hit perfectly each time. So I don't see an alignment problem. The far left piece of tapes are going into the first mirror, just mm's away from the end of the tube. It seems a bit spread out.... The last tape is through the lens, nice and pin point...... So...... HMMM? any ideas?

[Jeffrey Michael Wilson]

​WHAT ??? Can't see what you said?

[Gary Hair]

HMMM? any ideas?

Maybe it's because it's a DC laser, but all those spots tell me something is very wrong! When I fire my laser into tape like that I get one single mark that is about 1/8" in diameter.

[Bill George]

Start with the mirror at the tube check the mount and then the alignment. When you get to the rest do the same.
Your tapes do not show correctly alignment. Ray Scott has the procedure on his Rabbit USA website.

PS If you can't see the screen they have something now called glasses, wonderful invention. I use a pair of off the shelf reading glasses 2.0 or 2.5 just for the computer

[Dan Hintz]

307229
I see multiple points on all of those sheets... if you're getting multiple points with one pulse of the laser, your tube is dying (optics are shot). If those are multiple spots due to being in different locations on the table, it's alignment.

BTW, with most browsers you can hit <ctrl>+ or <ctrl>- to increase/decrease font sizes. No need to increase them with each post.

[Jeffrey Michael Wilson]

Drat......

[Jeffrey Michael Wilson]

Glasses, what a concept...too bad they don't work for me. It isn't a focus problem, it's something else. Had the lens replaced in one eye...he screwed up made it worse, so I sort of am not in a hurry to have them do the same to the other, one blurry eye is better than no eyes. So what would my tape show to be correct. It's hitting the same place both times. But I do believe it's alignment because I get perfect cuts upper left quadrant, lousy bottom right. BUT all the tests I've seen so far use the tape the way I do and if in upper left it hits the same spot as in lower right... they say that's OK... Enlighten me please. But also explain what about tapes show alignment problem.

[Jeffrey Michael Wilson]

So I do believe this is an alignment problem now ....Maybe.... Even though it hits dead center on the tape in all positions.... when I fire in the upper left quadrant everything is perfect, but lower right, has double image..... Is the method of firing into the tape somehow not valid? Don't get it.

[Scott Shepherd]

So I do believe this is an alignment problem now ....Maybe.... Even though it hits dead center on the tape in all positions.... when I fire in the upper left quadrant everything is perfect, but lower right, has double image..... Is the method of firing into the tape somehow not valid? Don't get it.

Your definition of "dead center on all the tape in all positions" is different than my definition of that. In your photos, I see 3-4 different spots on the tape. If you aren't seeing that, look under a magnifying glass, because those are NOT hitting in the dead center, all in the same place. Not even close as far as lasers are concerned.

[Dan Hintz]

But I do believe it's alignment because I get perfect cuts upper left quadrant, lousy bottom right.

This guarantees it's an alignment problem... and if those test shots on paper are to be believed, they scream the same conclusion.

Sounds like you have some fine-tuning work with a screwdriver ahead of you...

[Jeffrey Michael Wilson]

Wow, cool with the cntrl+...... OK, so in this pic, the far left is closest to tube, through mirrors... Second one is furthest away (think I held it down longer...3rd is both positions fired on same tape.....perfect line up.. Last is through lens, nice little dot. So if it was a tube problem, why would it cut perfectly in upper left quadrant, then double lines in lower right? It has plenty of power, as much as ever... What concerns me is the shape of the dot, almost like a little X. Before it goes into the first mirror this is most evident, but I don't see how a laser beam can be broken up like that..... just don't it. 307234

I see multiple points on all of those sheets... if you're getting multiple points with one pulse of the laser, your tube is dying (optics are shot). If those are multiple spots due to being in different locations on the table, it's alignment.

BTW, with most browsers you can hit <ctrl>+ or <ctrl>- to increase/decrease font sizes. No need to increase them with each post.

[Scott Shepherd]

the far left is closest to tube, through mirrors... Second one is furthest away (think I held it down longer...3rd is both positions fired on same tape.....perfect line up.. Last is through lens, nice little dot.

Why do you keep saying this? They are showing you that they are NOT in perfect alignment. If you fire the beam and it goes through the same hole in the same position every time, it doesn't mean you are aligned. Being aligned me the beam goes through the SAME hole no matter WHERE on the table it is. You should NOT be seeing 4 holes, X's or whatever. You should see 1 hole, period.

Showing the tape once it goes through the lens means nothing at all. That has nothing to do with alignment.

[Scott Shepherd]

It's not people being rude, it's people telling you what's wrong with your machine and you repeated the same thing that we've told you to correct about 6 times that you keep saying isn't an issue. We've said it's an optics issue from the beginning and you've said repeatedly it's not the optics.

The 4 different locations of burn marks in your tape is an alignment problem. Alignment can be mirrors out of alignment or something diverting the beam, like a pit or scratch. Either way, it's an ALIGNMENT problem.

Turns out, it was the optics. Go figure.

[Dan Hintz]

the far left is closest to tube, through mirrors... Second one is furthest away (think I held it down longer...3rd is both positions fired on same tape.....perfect line up.. Last is through lens, nice little dot. So if it was a tube problem, why would it cut perfectly in upper left quadrant, then double lines in lower right? It has plenty of power, as much as ever... What concerns me is the shape of the dot, almost like a little X. Before it goes into the first mirror this is most evident, but I don't see how a laser beam can be broken up like that..... just don't it. 307234

Your tube optics are toast if that's what you're getting directly out of the tube. Buy another one.

EDIT: Sorry, I read that incorrectly. You said the paper on the left is the beam after it goes through all mirrors. You need shots of the beam before it hits any optics to make sure it is correct. Still, if you're getting anything other than a small circle a handful of millimeters in diameter after any optic other than the final focusing lens, something is ****ed in the optics train.

[Bill George]

And you still have an alignment problem, anytime you fire the laser 3 or 4 times all you should have is one 4 mm or so burnt spot on the tape at each mirror that you check. The more times you press the button the darker that one spot gets.

[Bill George]

You know Jeffrey I really don't know why you bother coming on here and asking questions when you already have the answers? Nobody was rude to you, they tried to help and you argued. If I was a Moderator you would be gone.

[Rich Harman]

When one shot fires directly on top of another, in the exact same spot, making an identical mark...exactly the same size and shape on the tape in the same position...... that's not alignment.....

Very true. Alignment is when a mark is made at the same spot on the tape when fired in different positions.

But if you know it is a scratch on the mirror, I guess we are done here. Glad you got it sorted out.

[Dan Hintz]

Really? The forum blanks out B-o. ^ r-k. (without all of the characters in between)? The root word is completely safe! <sigh>

[Mike Audleman]

307229 OK, so checking alignment, I put tape on last mirror b4 lens, pulsed once far left upper corner, then far right.... it hit the same spot on the tape exactly...Did this on all corners and beam hit perfectly each time. So I don't see an alignment problem. The far left piece of tapes are going into the first mirror, just mm's away from the end of the tube. It seems a bit spread out.... The last tape is through the lens, nice and pin point...... So...... HMMM? any ideas?

You are checking alignment in the wrong places, its not before the lens, its the lens tube itself!

I had nearly the exact same issue with my chinese laser a while back. Here is what I believe is going on...

The downtube (where focus lens is) is not exactly 90 degrees vertical. Say your firing at 50% which puts 20w into the lens. The lens isn't square to the beam so the beam hits it off-center and at an angle. Like a prism its refracting the beam. Its shooting 18w where it should but diffracting 2% to a second spot. So, unless you fire it really hot, thus raising the amount of power to the second point or run it multiple passes over the same cut, you won't see damage from the 2nd spot.

Put a board under the lens and pulse it at full power for a couple seconds without moving the carriage, I wager you will see the second spot begin to mark the wood.

Use a triangle or t-square and verify your tube is dead nuts on 90 both front-back and left-right. I couldn't get mine close enough to eliminate it all the way. Pulsing at full power and watching the shape of the hole, I could nudge ever so slightly and get the tube perfectly aligned. Now I have one nice crisp dot now.

[Jeffrey Michael Wilson]

Replaced scratched mirror, working good.