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

[Sean Cusack]

One quick question - could the different rates of burning be MDF/LDF
specific? I think one unique feature of MDF is that you've got a bunch of
crunchies pressed between 2 pieces of paper. Could the paper just be burning
at a different rate than the wood? In either case, this info is super good
to know.

Sean

On Fri, Mar 18, 2011 at 9:41 AM, Corey McGuire <coreyfro at coreyfro.com>wrote:

> ...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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