Hello Tweakie,
I would like to know what CAM software did you use to laser engrave the lady photograph, and if you can share the post-processor that should be nice.
Thanks.
note: great job and nicely done.

 

Good Afternoon Tweakie,
I was reading about your laser project and found it extremely interesting. I have worked on industrial laser systems for about 20 years now and your system has a lot of the features of the machines that I have worked on, just in a smaller scale. It is very impressive. I will try to insert a picture of me standing in front of one our small systems with a 3000 watt laser. Small would be relative to some of our other machines anyway. In the spirit of sharing knowledge, I will throw my 2 cents in. Looking at the photos of your machine, it seems like you either have some prior experience with cutting laser systems or you just did your homework because you got a lot right. In your pictures it looks like the beam path comes down at about a 45 degree angle but I can’t tell for sure. If it is 45 degrees, you are all set, if not try raising your laser tube mounting so you get 45 degrees. Then if you put a circular polarizing mirror at the top of the 45 degree path, that will help give you a more even cut all the way around a part. I noticed in other laser builds in the forum and in the pictures you provided, the beam path is not fully enclosed, this will have a BIG impact on performance and optics life. Stuff floating around in the air will affect the beam causing the diameter of the beam to “bloom”. In other words, the farther you go, the bigger the diameter gets, which then causes the focus point to change and absorbs energy from the beam. Since your machine is rather small, you might not see a significant change. However, things like dust, hydrocarbons from things like spray paint and solvents as well as water vapor can contaminate the optics to the point of failure, the focus lens is especially sensitive to contamination. Enclosing the beam path on your X axis would require collapsible bellows on both sides of the X axis. The reason for the bellows on the non-laser beam side is to maintain a constant volume of space for the beam path, otherwise with only one bellow, it would collapse when stretched out and balloon when compressed. But again because your machine is rather small you might get away with just one bellow on the X axis. The Z axis would need a bellow also. The last part would be to supply the beam path with clean and dry air. A particulate filter down to 15 micron and a refrigerated air dryer would be best but a filter and simple water separator would probably do the trick. Blowing the clean air in above the focus lens and another line in front of the output mirror on the laser tube and with a sintered metal filter vent on your 45 degree box should do the trick. You want just enough air flow to have some positive pressure in the beam path to keep out the dust and vapors but not so much that your bellows start to balloon.
Another thing that you might find interesting is a spread sheet with some formulas about the energy density of your focused beam. I got these from one of the engineers at a laser manufacture that I worked for years ago. Your estimate of “about a kilowatt” is way off. You did not mention the diameter of the raw beam, but presuming about 8 mm and a beam quality rating of 1, your 40 watt laser tube and 50.8mm focal length lens gives you a spot size of 0.003” and an energy density of about 4,440,000 watts per square inch. If the raw beam is 6 mm, the energy density drops off to about 2,498,000 watts per square inch. I will attach the spreadsheet as well so you can play around with the numbers if you want to.
You did a great job with your build and I look forward to reading any updates.

 

Very well explained, I enjoyed the read- and the effort to document the information for others.
On a semi unrelated note, how do you like mach4? I've been considering switching from mach3 to something- and uccnc is high on my list. I've heard of many bugs on m4.