Something I perhaps didn’t cover very well earlier in this thread is “Air Assist”. This plays quite a key role when using the laser in two main areas and is, in my opinion, essential.
1) By directing the smoke / particles away from the focus lens this prevents contamination and the need for constant cleaning of this rather delicate component. (The lenses used at 10,6um are usually made from Zinc Selenide and AV coated – they scratch easily and are extremely brittle so the less they are handled the better).
2) When cutting anything that carbonises the air assist is used to remove the deposit from the bottom of the kerf and thereby increase the cutting / engraving efficiency.
I have chosen to use a co-axial air assist, for the most part, and have a 3mm diameter exit nozzle for both the beam and the air. This essentially pressurises the focus lens cavity and prevents the ingress of smoke and small particles. I use 3 different air supplies, the first is a low level, double acting, aquarium aerator which is always on whenever the laser is powered up, the second which is Tee’d into the same air line is a larger koi pond pump and the third is the exhaust side of a twin cylinder “Roc-r” pump (which is also used to power my vacuum table). All three of these pumps are oil-less and between them provide various air volumes for most applications.
Additionally I have a separate nozzle (not co-axial), which can be fitted when required, and can be used to direct a relatively high pressure “shop air” directly into the kerf. This is only used occasionally (when cutting plywood) and has the disadvantage that the high pressure / volume enables the fumes to escape the existing air extraction system (bad smell of burnt wood in the workshop).
When the little insects, shown in the earlier post, were cut I was using just the aquarium aerator, any greater volume of air would have scattered the individual pieces everywhere as no tabs were used.
Tweakie.
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