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Abstract: The increased concern for environment and sustainability are pushing machining operations towards the reduction or even complete elimination of cutting fluids. Grinding is not excluded from this objective, but greater difficulties appear due to the nature of the material removal mechanisms. In this work, two approaches aiming at the optimization of fluid application in grinding are presented. First, the influence of nozzle design on the development of velocity and pressure fields is studied using CFD tools. A new nozzle design that optimizes the characteristics of the jet is introduced, analyzed and manufactured. Grinding experiments show that improvements in wheel life and surface finish are possible using the new nozzle. Second, the performance of a new grinding technology that combines MQL with low-temperature CO2 is evaluated trough industrial grinding tests. Results show an increased performance in terms of friction conditions and surface finish. [Copyright &y& Elsevier]

Abstract: Wire electro discharge machining (WEDM) has become one of the most popular processes for producing precise geometries in hard materials, such as those used in the tooling industry. The so-called taper-cutting involves the generation of inclined ruled surfaces, and it is especially important in the manufacturing of tooling requiring draft angles. In this paper a new approach to the prediction of angular error in wire-EDM taper-cutting is presented. A systematic analysis of the influence of process parameters on angular error is carried out using Design of Experiments (DoE) techniques. A quadratic equation for the prediction of angular error that takes into account electrical parameters and part geometry is derived. Validation results reveal a dominant influence of the mechanical behaviour of the wire, rather than that of EDM regime. Following this assertion an original finite element model (FEM) to describe the mechanical behaviour of soft wires, typically used in taper-cutting operations, has been developed taking into account non-linear phenomena such as contact mechanics, plastic behaviour, stress-stiffening and large displacements. Both the results of DoE techniques and FEM simulation have been validated through experimental tests in industrial conditions. Deviations of accuracy of WEDM-tapered parts can be reduced to values below 4′ using these models. [Copyright &y& Elsevier]

Abstract: Industrial application of superabrasive metallic-bond form-wheels is currently limited by problems arising when trying to recover geometrical accuracy after precision is lost due to wear. Literature shows this is a current field of research, and different configurations of the electrical discharge dressing process can be found. In this work an original method for form truing of metal bonded cubic boron nitride (CBN) form wheels is presented for the first time in literature. The method uses a single-point metallic electrode, thus eliminating the need for expensive form electrodes. A mathematical model was derived to predict electrode path and velocity. The model includes the effect of electrode wear. Experimental tests were carried out on a test bench, showing over 90% efficiency in the removal of material from the wheel surface. Wheel performance after truing was examined through grinding tests. [Copyright &y& Elsevier]

Abstract: Tooling costs, machining time and surface finish in an EDM operation can be improved by using multi-stage planetary EDM strategies. However, the technological tables provided by machine manufacturers do not always adequately fit to the specific user application, especially in the case of gap values. In this work, a methodology for the calculation of gap variation between two consecutive stages that can be applied both in roughing and in finishing regimes is described. The methodology defined requires the realization of a number of EDM tests, in which the surface finish of each intermediate stage must be assured. It is shown in the paper that this is optimally done by using the strategy based on the complete removal of . Results also show that gap variation is dependent upon the radius of the first orbit until a limit value is reached. It is observed from the experiments that larger gap variations are related to the use of smaller electrodes and copper electrodes. Finally, it is shown that the steepest decreases in gap variation occur at the regimes at which both discharge current and pulse time decrease. [Copyright &y& Elsevier]

The use of multi-stage planetary EDM is the best option when it comes to the reduction of the machining time required to achieve the specifications of dimensional accuracy and surface finish of an EDM operation. Furthermore, this strategy allows the user to reduce costs by reducing the number of electrodes required to complete the operation. However, it is not always easy to optimize the design of this kind of operation due to the large number of parameters involved. This is especially so in the case of dimensional accuracy, which is influenced by the different error sources present during the process.In this work, the validity of different multi-stage planetary EDM strategies is assessed from the point of view of machining time and surface finish. However, the optimum choice under those criteria does not assure that dimensional accuracy requirements are met. Thus, the different error sources are analyzed, paying most attention to thermally induced errors, which are numerically simulated from experimental data collected during the process. [Copyright &y& Elsevier]