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Against the background of the very high wear of the contact material surfaces, ceramics with their outstanding wear properties are ideally suited to application in extrusion processes. Thanks to their high wear resistance, it is possible to reduce machine downtime, metal contamination of the product as well as the torque moment. The application of ceramic components requires a new mindset of the design engineers because they also have to take into account the typical disadvantages of ceramics, like pure linear material behaviour, limited breaking elongation and statistical fracture behaviour including size effect. It is essential to apply a material-suitable module and joining technique to withstand the complex collective stresses. For the ceramic components, it is necessary to determine the mechanical, thermal and chemical loads to which they are exposed in use. For analysis of the stress field, FEA (Finite-Element-Analysis) is a suitable tool to calculate specific stress distributions. In the next step, the stress distributions (axial and torque loads) are superposed to get an idea of the entire stress field. Furthermore with FEA, it is possible to calculate the tension-stressed volume (Veff) for these geometrically complex components, enabling calculation of the fracture probabilities according to the Weibull theory.

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Cobalt is a hard metal with magnetic properties, resembling iron or nickel. It is practically insoluble in water but dissolves readily in biological fluids like plasma. Ionic cobalt exists in either a bivalent or a trivalent form and different oxides and salts are encountered in the industry. Cobalt is an essential nutrient to humans with vitamin B12 representing the major physiological form in which cobalt functions in the body. Cobalt is mostly produced as a secondary product during the processing of other metals like copper, nickel and lead. The major sources of minerals are Zaire, Zambia, Canada and ex-USSR while the principal consumer of cobalt is the US which uses about 50% of the world production (Lison 1993).

Our industrial world is responsible for the emission of a great amount of respirable mineral dusts, either natural or artificially produced. This dust emission has become increasingly an important health problem, particularly in places of work where specific dusts were found to be responsible for severe lung diseases: silicosis, coal miner’s pneumoconiosis, berylliosis, hard metal lung fibrosis and asbestos-related diseases. Asbestos and other fibrous dusts are presently a major concern because of their carcinogenic potential [1,2].

In this paper a method for teaching, recording and on-line computing of continuous cutting trajectories for a computer controlled industrial robot (IR) used as cutting machine tool is presented. Like the algorithms for digital closed-loop control and coordinate transformation, the algorithm of cutting trajectory calculation has been formulated in the real-time programming language PEARL and implemented on a microcomputer. The proposed concept differs from the other well known methods used for conventional CNC-controlled machine tools in several points. It requires comparably low processing speed and memory capacity. Both the teaching of the measured points on the pattern workpiece and the interpolation of the continuous cutting trajectory are performed on a single microcomputer. The trajectory calculation is done online i.e. after each interpolation step the cutting tool carried in the IR hand is newly positioned. The feasibility and good performance quality of the presented alternative method has been confirmed by experimental investigations using a fast rotating hard metal alloy cutting tool.

The fact that hot metal pieces are capable of welding when forced into contact is an ancient experience of the blacksmiths, but any attempt to analyze the role the high temperature plays in the phenomenon is of a very recent date. From anticipating results of both the present and the next paragraph we may state that the essential action of the high temperature seems to be to soften the material, thus providing the possibility for large metallic contact areas to be generated by plastic deformation. However, it is reasonable to expect that the temperature also exerts another influence, namely, the creation of activation energy for covalent bonds between the members. In the literature this idea is predominating and some authors believe that a high temperature, which produces atom diffusion between the members, is necessary for the weld in contacts.