Design of a Novel Integrated Ultrasonic Tool Holder for Friction Stir Welding

Ultrasonic vibration used in friction stir welding (FSW) has shown advantages in reducing welding defects and improving welding quality. How to design an ultrasonic tool holder is a challenge because the holder is rotating in a confined space. In this study, we design a 20 kHz integrated ultrasonic tool holder in FSW. This novel configuration can be applied in general machining equipment. The elastic modulus is measured by non-destructive acoustic testing to attain the precise frequency. Three FSW transducers with alloy steel are designed by the modal analysis and the transducer prototypes are fabricated. The effect of pre-tightening force on transducer frequency is investigated, where the prestress of the piezoelectric stack instead of the torque is tested to achieve an optimal working frequency. The vibration of the transducers is measured by a Doppler Vibrometer System. It proved that the resonant frequencies are well consistent between simulation model and the experiment by the elastic modulus testing and the pre-tightening optimization. Moreover, the experiment demonstrates that the vibration amplitude is significantly different, even in a slight difference of steel material properties are adopted. The dynamic performance of the designed transducers is acceptable by the vibration measurement.

DESIGN OF A COMPUTER-AIDED GEAR MANUFACTURING TOOL – RACK-SHAPED CUTTER

In this work, the calculation of Maag gear shaper cutter parameters is performed for spur gears with helical teeth in three variants – straight-tooth tool with machine offset, helical-tooth tool without machine offset and helical-tooth tool with machine offset. It is therefore a prerequisite that the manufactured involute gearing has helical teeth for each variant. The created CAD program is universal and can be used for construction in other combinations as well. The tool clamping angles on the tool holder, the cutting geometry of the cutter and the characteristic of the gearing are introduced into the calculation. The output of the work will be then calculated individual parameters of the Maag shaping cutter in the tooling system, necessary for its construction. The calculation are performed in program T-Flex CAD and the summary output is graphical 2D/3D representation of the rack-shaped cutter in its base, normal and side planes, always in a different design based on the change of the tool input data and gearing characteristic. The analysis of the tool´s involute profile was solved by vector calculus and matrices and by rotating the tool in the chosen coordinate systems. The specific calculation of the tool parameters will be solved using goniometric functions.

Topology optimization of the tool holder produced with additive manufacturing

This paper deals with the topology optimizations of tool holder where three different mass targets were required. The holder was loaded with 499 N. Weight reduction of the tool holder placed in tool turret can positively affect the bearing durability. Easier manipulation with the holder is one of the results. In the process of the topological optimization manufacturing constraints, such as overhang prevention, self-supporting and material spreading were defined for needs of Direct Metal Laser Sintering production technology. Structural analyses of three obtained geometries were simulated for evaluation of the stiffness in three main directions of the tool holder. Finally, the weight and the stiffness of each individual geometry was compared and prepared for manufacturing.

A Smart Tool Holder Calibrated by Machine Learning for Measuring Cutting Force in Fine Turning and Its Application to the Specific Cutting Force of Low Carbon Steel S15C

Real-time monitoring of the cutting force in the machining process is critical for improving machining accuracy, optimizing the machining process, and optimizing tool lifetime; however, the dynamometers are too expensive to be widely used by machine tool users. Therefore, this paper presents a simple and cheap apparatus—a smart tool holder—to measure the cutting force of turning tools in the finishing turning. The apparatus does not change the structure of the turning tool. It consists of a tool holder and a piezoresistive force sensor foil, and transmits the signal through Bluetooth wireless communication. Instead of dealing with the circuit hardware, this paper uses the Artificial Neural Network (ANN) model to successfully calibrate the warm-up shift problem of the piezoresistive force sensor. Such a software method is simple, and considerably cheaper than the hardware method. For the force measurement capability of the smart tool holder, the cross-interference between orthogonal forces are very small and thus can be ignored. The force reading of the smart tool holder possesses high repeatability for the same turning parameters and high accuracy within the experiment groups. The authors apply the smart tool holder to cut the low carbon steel S15C, and to determine its specific cutting force in fine turning. The resulting fine turning force model agrees very well with the measurement. Its mean absolute deviation is 3.87% and its standard deviation is 1.55%, which reveals that the accuracy and precision of the smart tool holder and the fine turning force model are both good.