Homebrew PCBs

John,

If the 30" lens is working don't change anything unless you really 
need a finer cut. The 5" lens will have a smaller kerf width which 
would help with very fine inside cuts and detail if you need it. My 
laser machine used "cones" to guide the assist gas (compressed air 
for most plastics)into the cut. If you do something like this your 
results will be even better and you should be able to cut at a higher 
feed rate. We used a big dust collector that exhausted to the outside 
but the plastic fumes were hard to totally remove.

This Mitsubishi machine was a gantry type with a stationary resonator 
and moving optics in the X and Z axis with the work supported on a 
moving table for the Y axis. The optical alignment procedure was 
somewhat complex and critical for good cutting results. No fiber 
optics were used in the optical path in this machine. We did use a 
video camera several times to watch the beam since it could "see" at 
the IR wavelength of 10.6 microns. There was also a HeNe red laser 
for setting up the machine. Some of the bend mirrors were pure 
silicon with a gold coating and some were copper with a coating. All 
of the mirrors and lenses were liquid cooled.

Tom

--- In Homebrew_PCBs@yahoogroups.com, "John Myszkowski" 
<myszka_us2000@y...> wrote:
> Thanks Tom,
> That was very informative.
> 
> I only have a 30" fl lens for my CO2. I have good results with 
> cutting .125" pvc, acrylic and similar materials. I don't have a 
good 
> ventillation system, so I avoid too much plastics cutting (at least 
> until I get better ventillarion and compressed air system).
> 
> Would you say that an investment in a 5" FL lens (or beter) would 
do 
> a better job for me? I only intend cutting .125" material.
> 
> I have tried cutting the FR material, but I get too much charring 
> with the low power.
> 
> You can drill a BARE FR board before it gets copper plated. Then 
send 
> it through the through hole plating facility and plate on the 
needed 
> copper.
> 
> John M...
> ===============