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« on: July 17, 2012, 04:15:24 AM »
Something I have perhaps only briefly mentioned in earlier posts is the advantage, even the necessity, of Air assist.
When laser cutting wood, for example, carbon is produced and if this occupies the bottom of the kerf it will reduce penetration considerably. Air assist, if correctly orientated, will remove these carbon particles from the kerf as they are produced and cutting efficiency is much improved as a result. Although wood is perhaps the best example, many other materials will exhibit similar properties and the end product will almost certainly benefit from the use of air assist.
If the air is applied co-axial to the laser beam, for example – the air is fed into the side of the lens assembly and then exits through the same (small diameter) nozzle as the beam, this has the added advantage of preventing vapours or particles from the work piece being deposited onto the surface of the focus lens thus extending the life of the lens and reducing the necessity of frequent cleaning of this component. The disadvantage is that a clean, dry and oil-less air supply is required. The Koi pond aerator type pumps are pretty well suited to this task, they are available in various sizes and air flow rates and are not expensive to buy. These are relatively quiet in operation and are probably the most commonly used type for small laser machines. Shop air could also be used, providing the necessary traps / filters (similar to those used for vehicle spray work) are included in the line together with suitable pressure regulation but with a compressor there is always the potential risk of oil contamination of the lens if the filters are not changed regularly.
For cutting thin materials (veneers, gaskets and the like) a relatively low air pressure / flow rate is all that is necessary – too high a pressure can result in the cut parts or waste material being blown around on the cutting bed and causing problems. For this type of work I use a small Koi pond pump and also have an air-bleed valve in the line so that I can reduce pressure / flow rate if necessary. For the thicker materials I use an old twin cylinder Gast Roc-R pump and between these two different pumps manage to cover most eventualities.
Tweakie.
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