Secondary tool adhesion wear is commonly provoked by two effects, whose nature depends on the placement of the adhered material. The so-called Built-Up Layer (BUL) is formed on the tool rake face and the Built-Up Edge (BUE) is developed on the cutting tool edge. These effects can be developed by different causes depending on both the cutting conditions and the material to be machined. In this work, X-Ray Photoelectron Spectroscopy (XPS) has been used to analyze the built-up layers formed during the dry drilling processes of aeronautical Ti-6Al-4V alloy. Changes in the Ti oxidation state in each layer have allowed proposing a BUL formation mechanism based on chemical reactions of the workpiece material during the drilling process. Effects of these reactions have been contrasted through the XPS analysis of the chip generated in the process. In parallel, SEM and EDS have been used as complementary techniques for obtaining further information about the BUL nature.

Abstract:Manufacturing of grinding wheels is continuously adapting to new industrial requirements. New abrasives and new wheel configurations, together with wheel wear control allow for grinding process optimization. However, the wear behavior of the new abrasive materials is not usually studied from a scientific point of view due to the difficulty to control and monitor all the variables affecting the tribochemical wear mechanisms. In this work, an original design of pin-on-disk tribometer is developed in a CNC (Computer Numerical Control) grinding machine. An Alumina grinding wheel with special characteristics is employed and two types of abrasive are compared: White Fused Alumina (WFA) and Sol-Gel Alumina (SG). The implemented tribometer reaches sliding speeds of between 20 and 30 m/s and real contact pressures up to 190 MPa. The results show that the wear behavior of the abrasive grains is strongly influenced by their crystallographic structure and the tribometer appears to be a very good tool for characterizing the wear mechanisms of grinding wheels, depending on the abrasive grains.

At present, the techniques developed to control machine tool vibration have been dominated by passive features, focusing on manipulating the cutting parameters such as feed rate, cutting speed, and depth of cut. Since productivity is affected when modifying cutting parameters, other control methods must be investigated. To that end, electroactive actuators and robust control algorithms have attributes that make them potentially effective in reducing the vibration level. In this paper, the successful use of an adaptive control with a piezoelectric actuator to decrease the vibrations in a machine tool is reported.

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Grinding process is a very important process in machining industry being one of the most popular processes when high quality parts must be manufacture. Likewise, workholding is a critical issue on cylindrical grinding. The use of the driving dog is common when the workpiece is held between centers. However, one of the handicaps of this workholding is that the cylindrical workpiece cannot be ground along the complete length. In order to tackle this issue, in the present work the workpiece is held between centers avoiding the use of the driving dog. To this end, a methodology to obtain the grinding limit parameters that ensure that the transmitted torque is higher that the resistance torque is presented, being the aim of these tests is to avoid the sliding between the point and the workpiece. Finally, non-destructive tests are designed, which, using a safety coefficient of about 0.77, the tests allow the correct design of each specific grinding process. Keywords: cylindrical grinding, workholding, driving dog, sliding