Flame polishing with defocussed laser

Not quite a mod, more just misuse…
Has anyone tried flame polishing with the laser?
I’m trying to apply a repeatable flame polish to a laser etched microlens array.
I’ve had mixed success by moving the bed to the bottom of travel (Blacknose A3) so the laser is ~1inch diameter. At power 100, speed 8 it creates a mostly good finish but leaves some bubbles (these may be moisture in the plastic - I’ve been using scrap).

I get a really good finish if I slow the laser to speed 5, which results in a small controlled fire that follows the laser path (doesn’t stay lit after the laser moves on), but it feels wrong to have a fire going on in there!
The flame is the width of the laser ~1 inch diameter and ~3 inches high, and candle like (i.e. yellow and slightly sooty) (not to be confused with Sweep’s friend who is yellow and totally Sooty :wink:

I do have extraction and air blower, and the fire remains small and is located at the bottom because the workpiece is low to defocus, am I still likely to goose the mirrors, etc?

I just thought I’d ask to see:
a) has anyone had success flame polishing with the laser?
b) has anyone got experience of ‘accepting’ small controlled fires in the laser cutter?

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An interesting project Simon, but please don’t run your laser above 65% power.

Oh, I was not aware of that!
Does it burn out the tube?

Well yes, also you won’t get more laser than you would above say 70%, at least that is the received wisdom. I’ve not done a lot of experimentation with it.

Oh, good idea! No useful wisdom to offer, I always used a little blowtorch for this, but I’d love to hear how it turns out.

On the flame front, might it be worth supplying extra extraction with a hoover to suck out the smoke ?

I’d need to circumvent the door interlock to do that…
Even if I thought I could handle it safely, it is my work’s laser cutter, intentionally bypassing the safety interlock would be a good way to get permanently banned from doing home projects in the lab.
It was already a close call when I set fire to myself in the carpark last year!

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And this is why Rule zero in many spaces is “Do not be on fire!” :wink:

They’re more like guidlines anyway :wink:
But based on my experience, I can particularly recommend obeying rule zero if you have a housebrick sized 16Ah 6s LiPo battery strapped to your back. While I came away unscathed, it wasn’t the most relaxing experience.

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Eeek! That sounds gnarly!


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