THE INDEXED ASSESSMENT OF FUMES GENERATED BY HIGH-POWER LASER MATERIAL PROCESSING

The nature of the fume generated by high power laser processing is dep endent upon laser type, material being processed, assist gases used, a nd the energy density required to process the material. The fume produ ced from any one process will vary in its composition, aerosol size di stribution, morphology, and toxicity, all of which are important facto rs when assessing human and environmental hazards. At present no strai ghtforward method exists to estimate the hazards. In this article a me thod for indexing the hazards of fumes generated by laser materials pr ocessing is presented. The index can be applied to a wide range of mat erials and laser processing techniques and should lead to a standardiz ation of information pertaining to laser-generated fumes. Two paramete rs are applied to describe the fumes hazard. The first parameter is th e exposure limits, which indicates the perceived hazard of an individu al component released during processing. The exposure limits used are the UK long-term occupational exposure standards and the maximum expos ure limits. The second parameter is the component production rate from a standard material, i.e., the weight emitted per second (mg/s) of ea ch species during cutting. By combining these parameters, the Normal A ir Requirement (NHL) for each component can be calculated. The individ ual NHLs are then summed to produce an NHLtot. These NHLtot's serve as guidelines to the hazard since they are highly dependent upon process ing criteria and are weighted in this application to particulate emiss ions. They are also derived from continuous measurements, whereas in r eal applications the downtime during a working day is considerable. Fr om the NHLtot a classification system can be constructed which can be used to indicate the type of filtration and extraction necessary to ef fectively deal with the laser processing emissions. (C) 1998 Laser Ins titute of America.