Lightweight and vibration reduced hybrid FRP-metal drill tubes with structure-integrated sensor technology for BTA deep hole drilling processes

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BTA deep drilling is a process for producing bores with high length-to-diameter ratios. However, the required tool lengths lead to an increased tendency of the tool system to vibrate. Strong torsional vibrations during drilling, which occur primarily during the machining of high-alloy materials, lead to increased wear of the cutting edges and guide pads as well as to a reduced drilling quality. An improvement of the dynamic behavior through the vibration damping resulting from the inhomogeneous structure of fiber-reinforced plastics (FRP) increases the process reliability and thus has a large market potential due to the typically high component costs. Based on promising preliminary investigations, a hybrid FRP drill tube is therefore to be developed in this project. In addition to the experience gained from basic investigations on BTA deep drilling (ISF) and the experience gained in the manufacture, use and metrological monitoring of metal CFRP lightweight structures within the framework of the priority programme "Intrinsic hybrid composites for lightweight structures" (LKT, Fraunhofer IZFP), the cooperation with the companies CarboFibretec, BGTB and Kaiser Maschinenbau und Zerspanungstechnik ensures the support and the expertise of industrial partners from the development, design and manufacture of the drill tube up to the application and validation.In addition to the direct influence on the deep drilling process and thus on tool wear and hole quality, the development of the FRP drill tube also focuses on the material-specific properties of fibre composites (laminate structure, coolant lubricant influence, hybrid connecting elements) and the sensory recording of the loads acting in the composite in order to qualify it for industrial use. The use of FRP for tool systems requires investigations of the interactions of the matrix and the fibres with other machine components, e.g. in the area of seals or contact points on the damping system, as well as with coolants and chips. In addition, for the use of structure-integrated sensor technology, the fibre winding process must be developed with regard to the connection of the sensor fibres with as little influence as possible on the fibre composite. Within the framework of the project, comprehensive experimental and simulation-supported investigations are carried out to optimize vibration and to adapt the laminate structure to the cutting process. Corrosion processes in direct contact between fibres and metal require the development of hybrid joining systems for the permanent bonding of metallic components. With the help of a data line to sensors in the drill head and sensors in the laminate of the drill tube, the process-parallel recording of important process variables and critical load cases and thus a condition monitoring of the tool system are investigated.