LMT's tool service for drilling carbon fibre reinforced materials

To ensure compatibility to the process, each tool type is made to order for the application. The LMT 'One-Shot' tool is able to combine, for instance, three separate stages of operation using multi-step geometry. The tool geometry, point angles, helix angles and clearances are tailored to the thickness and make-up of the material stack, while the matrix formation, fibre types, proportions and respective properties along with the forming techniques being used are important elements in defining tool characteristics. The use of CFR materials in laminated or 'stacked' composite panels has been increasingly challenging to machinists as the cutting tool has to contend with the high abrasive nature of the material, as well as unfavourable vibration and resonance which can build up to the detriment of surface finish. While dulled tools can produce rough edges and any excessive force under cut can introduce 'peeling' that will lead to delamination. A key element in the cutting process is that the carbon fibres must be sheared and cannot be cut using conventional methods as this will result in shattering as the tool fractures the hard carbon material. Polycrystalline diamond (PCD) is said to be the best cutting tool material when drilling, giving higher spindle utilisation and therefore overall gains in productivity. PCD has the hardness of diamond while maintaining the toughness of carbide to give longer, more consistent tool life and also enables tools to be run at higher speeds.