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?


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!


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.


Eeek! That sounds gnarly!