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During soft-turning of rings, both, deviation of the wall thickness and the shape occur. Additionally, further changes of shape result from the subsequent heat treatment. To ensure desired geometric tolerances, a high stock allowance for finishing is necessary. Geometric deviations of machined rings originate mainly from workpiece clamping during the machining process due to elastic deformation. Therefore, several special clamping devices are applied in industry to reduce workpiece deformation. But the choice of chucks is always a trade-off between high flexibility and low part distortion. To ensure minimal part distortion in spite of using flexible clamping devices, clamping strategies and novel dynamical turning processes have been developed. Dynamical adapting of the depth of cut based on the measurement of geometric errors, is realized by using a tool actuator combined with an in-process ultrasonic measurement system. This paper discusses the compensation potential of developed methods to reduce part distortion. Keywords

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In machining of ring shaped components, the workpiece is deformed by the clamping forces of the chuck. This elastic deformation generates shape deviations in soft turning. Moreover, the machining process generates locally varying residual stresses which contribute to shape deviation of the workpiece. Hence, in machining of thinwalled bearing rings hexagonal out-of-roundness up to 200 lm occur. In order to minimize the shape deviations, a long stroke Fast Tool Servo (FTS) for controlling the depth of cut was developed. The applied FTS differs from other published FTS systems in the guidance design. The moving tool holder is suspended to the FTS frame by flexure joints instead of using a linear guidance. The flexure joints provide a low stiffness in moving direction and high stiffness in orthogonal directions. The high stiffness in cutting force direction is essential for a real time reduction of shape deviations in soft turning. In this paper, results of an experimental investigation for the reduction of the shape deviation by adapted non circular machining are presented, using the developed FTS. Based on the results, the influence of the cutting forces on part accuracy is discussed.

Metal working fluids (MWF) are widely used in grinding processes to lubricate and to remove the heat and chips from the contact zone. Apart from the chips, abrasive particles from the worn grinding wheel contaminate the metalworking fluid. The solid contaminants, in particular the abrasive particles crumbled from the grinding wheel, are believed to cause several negative effects like for example damaging the guideways of the machine tool. Furthermore, it is assumed that a pronounced interaction of the solid particles and the machined surface will decrease the achievable surface quality of the ground surfaces. Cleaning units are employed within the fluid circuit to prevent failure of the machine tool and to ensure the desired surface quality. The economic efficiency of such cleaning plants cleaning plants depends strongly on the choice of the grade of filtration (the particle size which has to be retained). A grade of filtration which exceeds the actual needs of the machining process adds unnecessary costs for operating the cleaning unit. To enable cost efficient design of filtration units the interaction between solid contaminants and the machining process has to be understood. The results of grinding experiments (face grinding of workpieces made of AISI 52100) confirm a significant increase of the surface waviness when corundum particles are added to the MWF. The underlying effect is an extraordinary tool wear combined with a locally varying effective depth of cut. The excess particles block the pores of the grinding wheel and are transported into the grinding gap. An increasing ratio of the size of solid contaminants and the size of the bonded grains on the wheel accelerates the wear of the tool.