[sntlewis]

Ok, I'm an official lurker as I wanted to make sure I could do what I thought I could do...

I have a laser table with 2'x4' capacity, vacuum table, ac servo drives, and a flowing CO2 laser..

Cuts balsa (haven't tried anything thicker than 3/16 YET) like a hot knife through really soft butter, Popular ply (3ply, 3mm) very nicely.

Now for the tough test.... 5-7ply birch plywood, cuts 1/8, butcher cut on 1/4...

Question is this, currently using compressed air to keep optics clean/cutting jet, has anyone tried/used something else as "cutting assist gas"?

I tried "unamix" (75 CO2/25 Argon) not much better.

[joeski]

Hi Stan,
I have a universal laser. I also service them. The compressed air helps keep the optics clean also the Universal lasers have a cone on the moving optical assembly. This also keeps the material cooler, but it does not stop it from burning. I have found using papermasking on the wood stops it from showing burn marks on the front and back of the material you are cutting. It doe not stop the charring where the beam actually goes through the wood.
Thanks, joe m

[sntlewis]

I'm redesigning the cutting nozzle to be a bit more "elegant" than the simple pinhole design.

The use of papermask is intriguing...

Yet, now a question remains concerning burning....

Charred wood is expected... When I have to make multiple passes to cut through material, I end up with a cut-kerf that looks like (). My guess it this is due to the heat build-up being greater in the center.

Possible solutions.... Move slow for the first/last cuts, faster for the intermediate cuts.

I can afford to run the laser back over the material as time is not especially critical.

[danr50]

I have a 55w 4x8 table and was considering testing use of argon for wood carving. Will this reduce the carbon build up that I see with Compressed Air? Is there any reduction in buring?

[Neil Pritchett]

the best we have found is to use the correct power for the job.
You need to cut through in one pass for best results. This stops the increased charring in the middle of the thickness. The laser is like a blowtourch in the kerf if it does not cut through. Also, the surface discolouration is reduced considerably if the fumes can be pushed through the material and away by the air assist and fume extraction. We recon, like a fire, it's the smoke particals that burn, not the solid. When they are above the surface with the laser igniting them, they discolour the surrounding area (and can contaminate the optics).
Another point is that every type of wood is different. Settings and thicknesses are specific to each. Sometimes even to a batch. Balsa for example can be a light as a feather to as heavy as medium hardwoods.
In our experience, open grained hardwoods do not normally give good results, eg. the red plywoods, because they burn too easily at the surface.

Happy cutting. Regards.
Neil (for CTRfuture Ltd) http://www.ctrlasers.co.uk

[sntlewis]

IMHO(and little experience), the 75/25 doesn't change much in the quality of cut nor the color.

+Stan