A numerical model of the temperature field during pulsed laser cutting of thin sheets
(approximately 2.5 x l0-5 m) was developed. Cutting was simulated through removal
of nodes from a finite difference scheme based on sensible heating to the phase change
temperature and a single value of latent heat (melting or vaporization). The pulsed laser
model predicts a heat-affected zone of less than 0.02 mm for pulsed laser cutting. For
comparable cutting with a continuous power laser, a heat-affected zone between 0.05
and 0.l0 mm is predicted. Thermal stress levels were predicted to be an order of magnitude
lower for pulsed laser cutting than for continuous power cutting. The stress levels
predicted by the model also increased with cut speed. Experimentally, pulsed laser cutting
yielded better cut quality, based on less cracking, than continuous power cutting.
In addition, the cut quality deteriorated as the cutting speed was increased for the continuous
power laser. Presently, application of pulsed laser cutting is limited by its low
cutting speed, which is restricted by the energy density of the laser. The model predicts
that increasing energy density will decrease the size of the heat-affected zone and increase
the maximum cutting speed. Therefore, pulsed laser cutting at high speeds should
be attainable without deterioration in cut quality.
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