Laser chemical machining (LCM) is a method of laser processing based on a gentle material removal by means of thermal induced chemical dissolution. Since LCM depends predominantly on the surface temperature of the workpiece, the process window is restricted by the appearance of gas bubbles at higher laser powers and their associated shielding effect. In order to extend the process understanding, the influence of the laser power modulation on the removal behavior is investigated in the present work. The experiments were conducted on titanium grade 1 and with phosphoric acid. Based on the response time in experiments with a single step function of the laser power, a threshold special frequency was determined above which a constant removal depth could be expected. To proof this hypothesis, the laser power was modulated rectangularly in time resulting in combination with the process velocity in different spatial frequencies varying from 1 mm-1 to 20 mm-1 . The investigations showed that the removal cavity exhibited sin-shaped variation in depth along the line with a spatial frequency corresponding to the spatial frequency of the laser power. When the spatial frequency exceeded the determined threshold frequency, the cavity depths is constant. This established the basis for generating complex removal profiles by varying the power in the range below the threshold frequency.
Keywords
- Laser Micro Machining
- Surface
- Threshold Frequency
- Titanium