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3d Laser Cutting With Nd:Yag High Power Lasers for a Car Body Application
Published October 31, 1994 by ISATA - Dusseldorf Trade Fair in United Kingdom
Event: ISATA 1994
A new development in car body construction is the use of "single piece sidewalls." Replacement parts for damaged car bodies, i.e., rear fenders, have to be manufactured by an additional process out of the sidewalls. The availability of cw Nd:YAG lasers with up to 2 kW power and with high beam quality now facilitates those applications.
With step index fibers of 1 mm, 0,6 mm and 0,4 mm core diameter cutting experiments were performed on mild and stainless steel, on zinc-coated steel and on AlMg5 plates by using a 1:2 and 1:1 imaging optics. Two cutting nozzle concepts were examined, a customarily used coaxial conical nozzle and a new off-axis two-jet Laval nozzle. Very smooth cutting kerfs with roughness Rz as low as 2 μm for cutting steel up to 3 mm thickness and Rz of 12 μm for aluminum were achieved. Subsequent to these fundamental investigations three-dimensional accuracy and cutting experiments with standard industrial robots lead to the installation of a robot laser cutting system for production.
Laser robot cutting experiments at the real workpiece showed that the required processing time and cutting quality can be reached with a cw laser power of 350 W guided by a fiber with a diameter of 0.4 mm and an imaging optic of 1:1. In the 3-D cutting process the distance between nozzle and workpiece fluctuates by the dynamic robot inaccuracy. The new Laval nozzle allowed a nozzle distance up to 15 mm and a working range of ±3 mm. The region of ±1 mm nozzle distance variation within a good cutting quality is achievable is not influenced by the different nozzle concepts. This region is restricted by the proportions of the "flat top" intensity distribution of the laser beam around the focal point.
The replacement parts are produced every month by means of an industrial robot on a 7th axis combined with a fiber-guided cw 400 W Nd:YAG laser.
Due to the higher flexibility of the range-controlled system concerning clamping, the facility for standard production today is equipped with a capacitive range-controlled customarily used coaxial conical nozzle.