[Fab] Fun with Lasers - When ventilation isn't enough...

[Corey McGuire]

...so, yesterday I cut some MDF in the laser engraver.  Being wood based, it
burns readily, thus smokes readily.  This smoke, unlike fumes from other
materials, affects the ability to cut and this is noticeable because cut
depth gets weaker the further the mirror gets from the laser the more smoke
there is.

I added fans to the duct to help pull fumes and smoke out of the machine,
but this will only go so far.

If people are working with fuming or smoking material, the only option to
reduce smoke and fumes is to slow the rate that the laser cuts, which means
lowering the power.  This allows the fans to evacuate the smoke before it
completely fills the machine.

This is pretty obvious.  What isn't obvious is, at least with wood, the
first pass is the smokiest.  So, what I tried yesterday was two vector paths
that overlap, and I altered the color of one of the paths.  This then allows
the engraving software to treat the two paths as layers (layering is based
on path color.)  One of these paths will be cut before the other, you can
specify the order, then power settings, speeds, and iterations.

The trick I did was I set the first layer to cut at a lower power and slower
than the second, and then I proceed to cut the second path 2 more times.

This kept the smoke from the first pass down to acceptable levels and the
cuts consistent across the piece.

The settings for 1/8" MDF were:

   - 1st layer : 10% 10% 1 pass
   - 2nd layer : 15% 15% 2 passes

YMMV

I'm going to try Luan next, which, I think, will be better material in all
regards.
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