LASER CUTTING OF COMPOSITES - TWO APPROACHES TOWARDS AN INDUSTRIAL ESTABLISHMENT

摘要

Carbon fibre reinforced plastics (CFRP) are of high interest as a lightweight material due to their high strength-to-weight ratio. Within industrial fields with a requirement on lightweight design and energy efficiency, the demand of CFRP increases continuously. Up to now, the cutting of CFRP, as a basic production step within the production of composite parts, is mainly performed by conventional cutting techniques, such as milling and abrasive water jet cutting. These techniques are known to have drawbacks, e.g. force input, handling of auxiliaries and tool wear. The laser cutting of CFRP has already shown high potential to be a practical alternative due to the wear-free and contactless processing. However, as a thermal technique, laser cutting has to overcome the challenge of heat input into the material. Two different approaches concerning deterioration free cutting will be examined and compared within this research. For that purpose, two different laser sources were used. Both laser sources have a maximum average laser power of P_L = 1500 W, one emitting continuous wave (CW) and the other emitting pulsed wave (PW). The first approach investigated is the laser cutting with a single mode fibre laser emitting continuous wave at high beam quality. A small focal diameter was achieved by the optical setup used, enabling narrow cutting kerfs and finely machined cutting contours. The relative movement of laser beam and material was realized by a combination of scanning optic and 3 precise linear stages. The second laser source is a high power thin-disk laser emitting nanosecond pulses. The optical setup consists of a fibre with a diameter of d = 600μm and a galvanometerscanner by TRUMPF, called 3D programmable focusing optic (PFO-3D), leading to a focal diameter bigger than that of the single mode fibre laser. The relative movement was realised by the PFO-3D and a 6-axis robot-system. The required process strategies, differences, benefits and drawbacks of both setups will be reviewed. The review will be completed by an examination of the complexity of the setups and introduction of efficient processing solutions. Comparative investigations with an identical material for both described setups were performed as a basis for discussion. Differences exist in appearance of the cuts and the choice of best parameters, while comparable qualities and efficiencies can be achieved for both setups.