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Walt Langhans
02-13-2013, 8:55 PM
Hi All

I was using a 40mm focus distance lens and the focus distance from the end of the nozzle was 7mm. I ruined my 40mm lens and got one with a 50mm focus distance. While asking for advice about what lens to get, it was also pointed out to me that my nozzle assemble wasn't completely perpendicular. I got my nozzle assemble perpendicular but that threw out my alignment, so I figured all I needed to do was to realign it at the last lens which I did.

Next I started to try and find my focus distance. I first tried the line idea that Dan suggest using a piece of MDF, and I really didn't see any line really stand out.

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Next I tried some letter and circles, the left side (which looks the best to me) is about only 2mm from the end of the nozzle and going left to right the distance increases.

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Looking at the results I not thrilled with any of them but I figured the focal length had to be in there somewhere, so I went back and started checking the alignment from the beginning.

I 'm dead center from the laser tube to the closest mirror. When I have the next mirror at the top of the machine the dot is centered left to right, but is high. Then when I move the mirror to the bottom of the machine I'm still good left to right but now the dot is low.

My problem is that when I turn the top adjustment screw in (to the right) it drops the dot, or loosen it (to the left) it raises it, but I need to lower one dot and raise the other, it like I need to fold the mirror. Any idea how to do that?

I hoping that my alignment issue will help focus issue but I'm concerned because the best results I got where when the nozzle was closest to the MDF, but it was only a 1-2mm away which is less distance then my original lens with the shorter focus distance. I'm not sure how that's possible, shouldn't my focus distance with the new lens be further than the old one?

Any help will be greatly appreciated.

Thanks

Rodne Gold
02-14-2013, 1:00 AM
You got a double image in those pics , are you rastering the circles? - only use vectors for determining focal distance.
The double image is either due to alignment , the wrong backlash settings or perhaps a loose mirror/lens or a bad lens. Remember the lens goes in flat side down...
You must do a proper alignment before you start. The CRITICAL mirror is the first one after the tube , you need to adjust the tube to hit that mirror dead centre and then adjust from there on.

Alignment procedures are more or less the same for all machines and you can find a lot of tutorials on youtube as well as a lot of explanations here. Always a PITA the first time , but once you get the hang of it , it's a snap.

Walt Langhans
02-14-2013, 1:24 AM
The circles where vectored, the top line of letters was rastered and the bottom line was vectored.

Before I stated I thought I did have everything aligned. I only redid the last mirror because I had only messed with the nozzle assembly and figured out I was good to go. Only after I got those results did I think to look at the middle (which I had thought was fine since it was and I had not messed with it) did I find it to be out of alignment.

I'll double check the lens but I'm 99% sure I put it in correctly and tightly.

Thanks

Rodne Gold
02-14-2013, 2:17 AM
http://www.rabbitlaserusa.com/Manuals/BeamAlignment.html
This is for a rabbit , but will apply to you too.

walter hofmann
02-14-2013, 5:14 AM
IT LOOKS LIKE YOUR FOCAL POINT IS SOMEWHERE DIFFERENT IF YOU DID RASTERING IT SHOULD BE A HAIRLINE.
YOU SHOULD PUT A STRIP mdf DOWN RAISES IT ON THE RIGHT SIDE ABOUT 1/2INCH AND CUT WITH LESS POWER A LINE ACROSS NOT VERTICAL, THEN FIND THE SPOT WHERE THE LINE IS THE THINNEST AND MEASURE THE DISTANCE FROM MATERIAL TO HEAD USE THIS MEASURMENT AS YOUR FOCAL DISTANCE.
YOU NEED TO ALLIGN THE BEAM START FROM MIRROR #1 THE CLOSEST TO THE TUBE THE SPOT MUST BE DEAD ON AND THE SAME WITH MIRROR # 2 BUT HERE YOU MUST GO ON THE TOP AND BOTTON AND NEEDS TO BE DEAD CENTER TOO, THEN GO ON TO THE MIRROR ON THE LASERHEAD CARRIAGE PUT A STRIP OF TAPE OVER THE HOLE AND HERE ALSO NEED THE BURN MARK DEAD CENTER BUT IN ALL FOUR CORNERS.
CHECK ALSO IF THE RAILS ARE SQUARE AND THE MIRRORS IN THE SAME HIGHT.
GREETINGS
WALTFL

Dan Hintz
02-14-2013, 6:26 AM
Next I started to try and find my focus distance. I first tried the line idea that Dan suggest using a piece of MDF, and I really didn't see any line really stand out.

This is like trying to align your vehicle's wheels with a screwdriver and a ruler. You need a high-resolution substrate, something like anodized aluminum or a painted aluminum sheet (like the suggested gutter material from Home Depot). MDF is not a high-res substrate by any stretch of the word.

Walt Langhans
02-14-2013, 1:13 PM
The laser is aligned (finally) and here's the results I got. I varied the speed and powers setting to see if I could get some clearer results and ran a horizontal line for the heck of it and here's what I got.
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I'm not sure but maybe the middle row, if you count the first mark on the right and move left then maybe somewhere around 14 to 18?

Thoughts?

Walt Langhans
02-14-2013, 1:57 PM
Ok now I'm really confused. I just tried to cut out a square using my best guess for a focal distance and this is what I got

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Any idea what's going on?

Richard Rumancik
02-14-2013, 1:59 PM
You mean both rectangles plotted at the same time? If so the alignment is off and you are getting a bad out-of-focus reflection from something.

Mike Null
02-14-2013, 2:02 PM
Walt

How about trying to mark anodized aluminum? It's a much higher resolution material and will give you a better reading. If you hit the focus with raster then your vector should be ok too.

Walt Langhans
02-14-2013, 3:13 PM
You mean both rectangles plotted at the same time? If so the alignment is off and you are getting a bad out-of-focus reflection from something.

Yeah that was supposed to be a single rectangle cut in one pass...

Well I figured out the issue. I'm an idiot and someone should probably come and take my laser away before I put my eye out or something... I never bothered to align the the mirror what is on top of the nozzle assemble with the lens. It doesn't have any tension screws in it, and the adjustment screws don't look like the other ones so I just figured it was the way it was. So now the laser is aligned FOR REAL THIS TIME, lol, and I redid the alignment test and one line stood out, so I used that for the focus distance and now I'm back and running, yeah!

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Thanks for all the advice, and patience :)

Walt Langhans
02-14-2013, 3:33 PM
And now for the icing on the cake... My original thought was since my old lens was 40mm and the distance from the nozzle to the material was 7mm, since I was getting 50mm lens I figured that the new distance from the nozzle to the material should be 17mm. But, as we all know, there can be a big difference from what sounds good to what actually works so rather safe than sorry I did the sloped material alignment test. Just an FYI my new focus distance from the nozzle to the material is... wait for it... 17mm.