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

[Corey McGuire]

That's a good question.  I was cutting from the unfinished side.  I don't
know if that has a surface treatment.  I think part of this result is simply
because when you cut the path once, the carbon changes the way the surface
absorbs the laser energy causing it to burn more slowly.  The real answer
will come when we cut real wood and if this process helps in that instance
or not.

On Fri, Mar 18, 2011 at 10:02 AM, Sean Cusack <sean.p.cusack at gmail.com>wrote:

> 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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>>
>
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