One-Week Build

General discussion of laser machines

Re: exhaust and 2nd mirror

Postby twehr » Sun Apr 03, 2011 2:00 pm

LeonS wrote:What were you using for an exhaust fan? There didn't seem to be much front-to back air flow in the video.

Do you think having the laser tube exposed to the smoke and acrylic fumes may cause problems?

Sounds like there has been issues with your 2nd mirror. Any advice for those of us in the pack from the path finder? :-)


Don't let the appearance of the smoke in the video influence your thinking about the exhaust. Remember, I had air pumping into the box but not directed through the nozzle, which means it was just blowing it around all over the place. I was just trying to keep part of it off the lens. Without the undirected air, it actually works pretty well. I am using a blower from a small furnace. A little crude and probably overkill for the volume really needed, but works. I picked up a junk furnace for free from a dealer and paid $25 to have the rest of the furnace accepted at the local dump, after removing the blower - so it was a $25 solution. Just plows outside from my shop.

I think the hardest part of the mirror alignment process is starting out with the two mirrors square with each other. There is really nothing good to reference them with. Still not sure my are straight. Height is pretty much automatic thanks to Bart's design.

Here is what I have going on right now.
1. Laser hits 1st mirror just about dead center. Since that mirror never moves, I don't have to worry much about it.
2. First mirror hits second mirror at same point both near and far, nearly center.
3. Second mirror hits entrance to lens holder (and third mirror) at the same height. BUT, I am not able to bring the near and far points together horizontally. Close enough to work without the air nozzle, but still too far apart when the nozzle is installed - far points are centered in the nozzle (and therefore work well), but the near points are obviously bouncing around inside the nozzle, as it does not make its way out through the small exit aperture.

I think I am going to cut a jig that will help with initial alignment. Something that will provide a reference point (from side of frame to center of mirrors?) and setting both mirror holders at exactly 90 degrees with each other. Maybe something like this:

Mirror Squaring tool.pdf
(215.21 KiB) Downloaded 864 times


I may cut something like this, just to check where I am at. If off, that could lead me to fixing the issue.

Open for suggestions from anyone and everyone.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
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Re: One-Week Build

Postby LeonS » Sun Apr 03, 2011 2:41 pm

The horizontal offset suggests to me that your X axis isn't perpendicular with respect to the Y. Did you use a framing square to insure it was absolutely square. Aligning the mirrors is probably the most accurate way of getting the X and Y axis perpendicular that I can imagine.

- Leon
LeonS
 
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Location: Herndon, VA

Air nozzle

Postby twehr » Mon Apr 04, 2011 12:16 am

I made a custom tool to check square on the 1st and 2nd mirrors. I was already square but it was nice to have the confirmation.

I resquared the x axis, raised the lens holder mounting plate, required the third mirror to the y axis. Reaimed the second mirror and reinstalled the air nozzle.

All is working now :mrgreen:

Buttoned everything up again and retested to ensure nothing moved. Finished.

Tomorrow night, I will clean up the shop and start back on production projects, but with a lot more flexibility than I previously had.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

Re: One-Week Build

Postby LeonS » Mon Apr 04, 2011 12:24 am

Great that you have it all squared away; no pun intended.

So, you needed to raise the lens holder a bit? Was that needed to get the 3rd mirror vertically centered on the beam?

Did you make some spacers between the lens carriage and the lens mount?

Congrats!
- Leon
LeonS
 
Posts: 145
Joined: Wed Nov 25, 2009 8:09 pm
Location: Herndon, VA

Re: One-Week Build

Postby twehr » Mon Apr 04, 2011 1:17 am

Just added a washer at each screw beneath the plate.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

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