High precision laser macro-drilling of CFRP with a new nanosecond pulsed laser – optimized towards industrial needs
International Congress on Applications of Lasers & Electro-Optics (ICALEO)
Due to their outstanding strength-to-weight ratio, carbon fibre reinforced plastics (CFRP) are of high interest for lightweight construction. Within industrial fields requiring lightweight design and energy efficiency, the demand for CFRP increases continuously. Until now, machining of CFRP, as a crucial step in the production chain of composite parts, is mainly performed by conventional techniques such as drilling, milling and abrasive water jet cutting. These techniques come with known drawbacks, including force input, handling of auxiliaries and tool wear. The laser cutting of CFRP has already shown its high potential to be a practical alternative due to wear-free and contactless processing. However, if sufficient cutting rates are required, laser cutting has to overcome the challenge of either non orthogonal cutting edges when using short pulsed high power lasers, or heat input into the material when using continuously emitting (cw) high power singlemode laser sources, as shown by Staehr et al. . Within this investigation the machining with a novel short pulsed high power laser source by Trumpf Laser GmbH emitting at λ~=~1030~nm will be examined. The lab-state laser source provides nanosecond pulses at tp~=~20 ns, at a maximum pulse energy of Ep~=~100~mJ and a maximum average power of Pavg~=~1.5~kW, while maintaining a very good beam quality allowing for small focus diameters down to df~=~84~µm with the focusing optics used. It was shown that processing with small focus diameters results in narrow cutting kerfs contributing to the cutting edge angle. In addition, the investigations revealed a minimized thermal load resulting from the short pulses. At the same time, challenges resulting from shielding effects when specific parameters are used will be displayed and discussed. Different processing strategies for adjusting the cutting edge angle towards orthogonality will be presented in the paper. This optimization procedure aims at the drilling of macroscopic holes with a diameter of Ø~>~4~mm in CFRP laminates with a thickness of s~≥~2~mm at very high precision.