Air Assist & Fume Extraction
Last Updated: 25th May 2009
I've grouped these air assist and fume extraction together because the way I see it, they're both about getting vapour/fumes away from where the work is being done and are therefore really a part of the same system.
It's fairly obvious what fume extraction is all about so for the benefit of those who don't know, I'll begin with air assist:
Air Assist
Air assist is a technique whereby air, or an inert gas is blown at the point where the laser beam is cutting. This improves the efficiency of the laser by getting the crud out of the beam path and helping to keep the lens clean, and helping to prevent the vapour igniting (especially if an inert gas is being used).
Machines that air assist built in are set up such that the gas is blown through the same hole in the cutting head as the laser beam. However when it's been retro-fitted this is often achieved by fixing a pipe/nozzle to the side of the cutting head.
Now it occurred to me, that if we're just using air rather than an inert gas, it might be better to suck the fumes out of the way rather than blowing it. Here's a mock-up of what I'm considering:
In a nutshell I plan to cover part of the current exhaust opening in order to create suction through a flexible hose, connected to a length of brass tube strapped to the cutting head.
Sub Bed Extraction
Another facility you sometimes see on more expensive machines is sub bed extraction.
My cutter came with a metal honeycomb panel that sits on the bed built into the machine. Thus any fumes going into it would tend to be trapped there. I've put a handful of coins onto the bed of the machine, and sat the honeycomb panel on top of that, in order to create a small gap under the panel; through which any fumes that go into the honeycom are now sucked out.
I plan to get a bit more sophisticated with this, especially if what I've said I want to try above (see Air Assist) is successful.
Fan Duct
The image below shows a simple modification that I made on day 2 of using my machine:
The fan unit supplied with the laser cutter is not a custom made unit and has a flap on the exhaust with hinge brackets which mean that the duct won't fit snugly; there's a gap.
So I removed the flap, cut off the plastic hinges (with a craft knife), trimmed a couple of centimetres off the end of the duct fitting, and fixed it in place with duct tape - no more gaps on the exhaust.