Engraving tips - need clarification

[Ivan Sule]

Hi. I watched following videos from Russ:
https://youtu.be/YvQ8L7Xth8k (1)
https://youtu.be/K7wXla8JgeA (2)
and am being confused with, I would say, different approaches. Or perhaps I did not understand completely. In video 1 he calculated speed according to dot size. In video 2, he talks about acrylic, and starts with 150mm/s without any explanation, and then adjusts power and engraving mode to get smaller dot. So what would be the best way for acrylic, or in general? Thanks.

[Pete Cyr]

The point Russ was trying to make is that the controller will fire and produce a dot at specific rate. If you move too fast there is space between the dots......if you move to slow there are dots on top of dots.

Power determine the amount of damage or how much burn is produced by each dot
Speed determines the dot density (how close or or far away each dot is from the adjoining dot)

Depending on the effect you are trying to achieve you may vary speed or power differently for different materials.

As for dot size it will only change with a variation in lens or by changing the focal distance - you can not change dot size by changing speed or power. (although changing power may appear to give a change in spot size due to the amount of damage caused by the change)

For acrylic there are two different acrylics - one engraves nicely one cuts nicely -neither do both well. basically cast acrylic engraves well and extruded cuts well. - I engrave acrylic at 15% 400ms/s - cutting varies with thickness - see the attachment for a bit more data and experiment to find your sweet spot.

acrylic-castvsextruded.pdf

[Ivan Sule]

Thanks! I think you helped me a lot here. I guess Russ's calculation should be considered for photo engraving. When he used that special engraving mode to reduce power - less power burns smaller dot.
It was quite interesting to see what lightburn's newsprint image mode could do. Basically, if follow Russ's advice, one can conclude that jarvis mode should be run at appropriate dpi, according to dot size. But newsprint can be run at higher dpi and acts even better.
I hope I will be able to make some comparisons soon - if my laser gets fixed