Different result with the same materials

[Term1nUS]

Hi.

I was analysing different examples of laser working on Acryl (PMMA) and found one interesting thing.
At the first picture we can see vaporized material and melted edges.
At the second example we can see situation like material was boiled and then frozen.

All that work was made on CO2 laser engraver/cutter.
How can I reach the second result? What parematers should vary to accomplish that? Power, speed, focus distance? May be cooling of cut point?

Any ideas?

[Tweakie]

What is the material and what is the scale of your photos ??

Tweakie.

[Term1nUS]

Material is PMMA (Akryl). The width of cut at pict.1 is about 0.1 mm. The next picture present edge of cut 0.2 mm wide.

[Tweakie]

So, if I am understanding this correctly, the first picture shows a smooth edge as would be achieved by cutting at the correct speed.
The second picture shows the edge which has been cut too fast and possibly with too much air assist. The material has cooled before it has had time to flow into a smooth edge.

Tweakie.

[Term1nUS]

Well, it might be true.

Can it be if the laser beam was bit disfocused?

[Tweakie]

Can it be if the laser beam was bit disfocused?

Possible, but acrylic tends to act as a waveguide at 10.6um so focus does not have quite the same effect as it does with other materials.
As an example, 10mm acrylic can be cut with straight sides yet there is divergence to the beam shape which, in theory, should produce a 'wine glass' shape.

Just a thought.

Tweakie.