Cutting DefectsDuring any thermal cutting process it is possible for defects to be created in the material being cut. The main processes used are oxygen cutting, plasma cutting and laser cutting. Defects may arise due to incorrect process settings, incorrect use of process, damaged or defective equipment, incorrect cutting speeds, use of wrong size nozzle, or inherent sensitivity in the material being cut. The type of defects that may be encountered include excessive melting of the top edge, rounded edges, incomplete cut, cut not perpendicular to plate surface, non-parallel cut, wavy cut profile, and heavy slag on cut surface. These are caused mainly by process or equipment related problems, and are therefore easy to overcome by training or attention to detail. Cracking, porosity, formation of hardened zones, or loss of alloying elements, are defects normally caused by an inherent sensitivity in the material being cut. These are less easy to deal with and sometimes the problem is unavoidable. Attention to setting up the process properly, ensuring the equipment is in good condition, cutting at the correct speeds with the cutting heads or nozzles at the correct distance from the plate will avoid many of these defects. If cutting a crack sensitive material, preheat can be used to reduce the thermal shock of the cutting process.
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