Mylar and diode lasers

Hi, I have a little Neje 3.5w 445nm laser module strapped to my cnc 3018 Pro. I have been cutting paper as a trial and then bought some mylar which it will not even come close to getting warm despite several attempts at focussing the beam.

are all diode lasers ineffective against mylar?

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Looks like mylar allows the 445 nm laser to pass thru it only absorbing 16% of the power. 3.5 watts x 16% = .56 watts of cutting power.

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,56 watts? even less when you consider that the 3.5w is power INPUT!

that’s blown me apart for cutting stencils with a laser then!

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Maybe use black paint on it, like they do tiles. Just a thought.

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Multi use stencils or single use? Stencil paper (coated cardstock)? I use a drag knife cutter (Silhouette Cameo) and Avery masking vinyl for Cerakote masking.

Not a cheap solution, but it works great.

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In tests using my diode laser I’ve had success with using coloured acetate sheets as a substitute for mylar. I don’t think it has the same degree of resistance to chemicals and solvents as mylar so it might not be suitable for all use cases, but it seems to be a reasonable alternative.

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Mylar®, also known as BoPET (Biaxially-oriented polyethylene terephthalate), is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, (reflectivity), gas and aroma barrier properties, and electrical insulation.
It reflects the laser light.

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That’s not correct, it allows the majority of the 445nm visible laser light to pass through (approx 84% according to the chart posted above). The majority of the remaining 16% will be absorbed by the mylar and converted into heat and a very small amount reflected back. However, if you’re talking about aluminised mylar then yes almost all will be reflected back.

my bad , I meant absorbs

Hi.

Nope, that neither unfortunately, save for the 17% mentioned above.
Not high enough percentage to make accurate damage to any material.
With a higher power(density) it might be possible to produce damage that looks like a rat gnawed it, but that’s usually not the desired looks we’re after.

Regards,
Sam

:finland:

Lol! Always leave room for creators to create.

CO2 doesn’t have that issue ,
and my first reply is absoultly correct.

meaning a co2 will cut mylar

a diode will not
just like clear acrylic ?

Hi.

Absolutely, that’s why I said usually :wink: .

I for one would very well see myself using that effect to my advantage if I were to cut stage lighting gels and/or gobos, but on stencils, not that much.

That’s not an issue, that’s a feature that’s firmly tied to the wavelength of the laser vs. the properties of the material.
While that kind of an inbuilt selectivity may seem like an issue to us hobbyists, it’s actually beneficial in many industrial cutting jobs.

Still the answer to that is nope, at least as this thread is about uncoated mylar and a visible spectrum 445nm (diode) laser.
With visible spectrum lasers, that same goes for a plethora of highly transparent materials:
a few % is reflected
~1~20% is absorbed
the rest passes right through.
When the transparency is reduced somehow, those figures obviously change.

Regards,
Sam

:finland: