Method and apparatus for improving reliability of a machining process

Apparatus for machining a work piece by means of a liquid jet (WJ) guided laser beam (LB) comprising:

• a) a machine head (LH) with a coupling unit for coupling a laser beam (LB) into a liquid jet (WJ) to generate the liquid jet (WJ) guided laser beam (LB),
• b) an outlet (5) in the machine head through which the liquid jet (WJ) guided laser beam (LB) leaves the machine head (LH) for machining the work piece,
• c) a protection shield (20) replaceably fixed to the machine head (LH) and mounted at a distance from said outlet (5),
• wherein
• d) the protection shield (20) is a blind plate without a hole in its centre.

Apparatus for machining a work piece by means of a liquid jet (WJ) guided laser beam (LB) comprising:

• a) a machine head (LH) with a coupling unit for coupling a laser beam (LB) into a liquid jet (WJ) to generate the liquid jet (WJ) guided laser beam (LB),
• b) an outlet (5) in the machine head through which the liquid jet (WJ) guided laser beam (LB) leaves the machine head (LH) for machining the work piece,
• c) a protection shield (20) replaceably fixed to the machine head (LH) and mounted at a distance from said outlet (5) and having a transit-hole (23) for passage of the laser beam (LB) guiding liquid jet (WJ),
• wherein
• d) said transit-hole (23) is formed by:
• d1) fixing a blind protection shield blank (20) to a front of the machine head (LH) prior to launching said liquid jet guided laser beam (WJ),
• d2) generating said liquid jet (WJ) guided laser beam (LB) and impinging it on the blind protection shield blank (20),
• d3) drilling a transit-hole (23) into the blind protection shield blank (20) by means of the liquid jet (WJ) guided laser beam (LB), said transit-hole (23) having a minimal size for allowing the liquid jet (WJ) guided laser beam (LB) to transit without hindrance.