Laser Cutting Theory
Lasers are rated by their power output in terms of watts. Since laser cutting is a thermal process, the amount of heat produced relates to its capabilities. Whereas a 300 watt laser with a high quality output is more than adequate for the cutting of paper products, it lacks the heat producing capabilities to effectively couple into aluminium. Given all other considerations being equal (eg power distribution, spot size, etc), increased power allows for faster processing speeds and the ability to cut thicker sections of materials.
Since quality results are obtained by the application of consistent energy, the stability of the laser’s output is a key feature in cutting. This includes maintaining unwavering output energy (power stability), consistent beam quality (mode stability), and fixed energy concentration (pointing stability). Should the power increase or decrease by more than a few percent over the short term operation, the beam quality oscillate between a Gaussian and multi-mode profile, or the location of the beams direction shift more than a few tenths of a milliradian due to the outputs instability, there will result a noticeable change in the available power density for cutting.
Particularly evident in metal cutting and ceramic processing, studies have shown that random occurrences of inconsistent edge quality, namely variations in kerf, edge smoothness, and perpendicularly, are attributable to the effects of polarisation. Uncontrolled or random polarisation is characteristic of most standard material processing lasers. It can unpredictably affect the relative degree of absorption of the beam’s energy that is coupled into the material at a given moment. To correct this inconsistency, lasers can be equipped with optical packages which either fix the polarisation to be aligned in the same direction of the cutting action or circularly polarise the output to give equivalent coupling regardless of the direction travel.