Some salvation, flaming, focal lenght and cork

[daniel coyle]

First of all want to say thanks for the help I have gotten here. finally got my replacement laser up firing and cutting after a miserable summer replacing my first laser after it burned down. Folks here made things much less miserable than they could have been.

Now that I have it running I wanted to get help with controlling the flaming I see happening. Cutting 6mm cork with a 100Watt RECI running at speed = 20 and power = 72%. The lens is 18mm diam by 80mm focal length. What this means is that the short laser head is a good 5cm off the surface of the cork when the lens is focused on the surface. So, although i still run it, it seems unlikely that the air assist is doing anything. The cuts are sufficient for my needs but you will see in the pictures that there is a lot of flaming on the surface during cutting (as evidenced by the partially charred surface). Cutting cork, for those of you who have not done it, is tricky and get trickier as it gets beyond 3 or 4 mm.

IMG_20130810_212900.jpgIMG_20130810_212912.jpg

So, I would like to avoid burning down this one as well and would like to figure out what is causing the flaming, whether there is any way to improve the air assist to improve cutting and any other thoughts that have not occurred to me.

[Dan Hintz]

What kind of air assist do you have, co-axial (through the cone) or side tube? If you have co-axial, switch to side tube and lower the tube's nozzle to be closer to the substrate. What pressure are you running at? If you're only at 10-15psi, increase the pressure to 25-30psi.

[Rodne Gold]

Co axial is not great - use a side tube directed at the cut and use a decent compressor with TONS of air assist - we always have our air assist at a very angry hiss or roar... those little aquarium pumps you get with the lasers are worse than useless.. if you use a side pipe and not coaxial , you don't have to worry about moisture or oil in the airsteam as it does not affect the lens , but you might have to do some more lens cleaning..
Air assist is vital , we do not laser anything at all if our compressor or air assist is down.

[daniel coyle]

Thanks again Rodne and Dan

I am using the co-axial (as you describe it). The laser head simple is not long enough to get anywhere near the surface. i will work on getting an external air tube on the job. Any tips on how close to place a tube assist as you guys describe? And, I assume that will both improve cutting and help with the flame up issues?

[Dave Sheldrake]

Co-Axial is messy if you don't have the best air supply but it's also the most efficient (making a few other assumptions), Making a tin-can air dryer isn't difficult and can be done for under $15 to take care of water and oil in your air supply.

If you don't mind spending a few dollars you can buy a ready to fit nozzle that is designed for use with the 80mm lens from a number of Chinese sellers and it will position your air much closer to the job (about 8mm above it).

There is quite a bit of science behind air cones on coaxial supplies and getting it right can make a huge difference (getting it wrong can cause fires at worst and bad results at best) . Drop me a PM and I'll send you the details of a home brew air cleaner that works well

best wishes

Dave