János Kundrák

Environmentally Friendly Precision Machining

ABSTRACT Material removal processing has been investigated both theoretically and experimentally to a certain extent. The demands for environmentally friendly processes impose new parameters such as the use of minimal quantity or even the complete omission of cutting fluids. Therefore, the related processes need to be newly studied in order to be optimized for specific cutting conditions. Cutting fluids are used in material removal processes mainly for lubrication, reduction of the temperature in the cutting region, and increase of tool life. However, cutting fluids are associated with skin and breathing problems of the machine operators. Furthermore, after their disposal and if, as in most cases, recycling is not possible, they may become polluting agents in soil and water when inappropriately handled. In this paper the case of hard cutting, a process that can be performed without the use of a cutting fluid, is investigated. A discussion on the technological parameters involved is given and experimental data are presented in order to point out the environmental as well as the economical benefits emerging from the use of such a technology.

On a Novel Tool Life Relation for Precision Cutting Tools

When using new, very expensive superhard tool materials (diamond or CBN) for precision and ultraprecision machining of parts made, very often, from expensive materials, exact knowledge of the tool wear process (considering, of-course, its stochastic character) is absolutely necessary. It means, that we need new tool-life equations for these new tools. In the present paper, a new tool life relation is proposed based on machining experiments. It reflects the two-extremum form of tool life curves and is valid for a wide range of cutting conditions.

Possibility of reducing environmental load in hard machining

Abstract. The development of metal machining processes and procedures has been characterized by aiming at accuracy and economy for decades. The applied coolants and lubricants helped this process; however, they are polluting the environment. For today that is a social demand and technical possibility that environmental aspects should predominate better in production engineering. In the frame of this article, through the application of dry hard turning we shall spotlight on its economy and efficiency. We shall prove that, keeping the same accuracy and economic efficiency, it is possible to choose a machining process by which the environmental load can be reduced compared to the most frequently applied grinding.

Effect of Environmentally Conscious Machining on Machined Surface Quality

Modern machining processes continuously face cost pressures and high quality expectations. To remain competitive a company must continually identify cost reduction opportunities in production, exploit economic opportunities, and continuously improve production processes. A key technology that represents cost saving opportunities related to cooling lubrication, and simultaneously improves the overall performance of cutting operations, is dry machining. The elimination of coolants or significant reduction in cooling lubricants affects all components of a production system. A detailed analysis and adaptation of cutting parameters, cutting tools, machine tools and the production environment is mandatory to ensure an efficient process and successfully enable dry machining. Case study is shown for examination of cylindricity error and surface roughness of helical milling machined surfaces by environmentally conscious way.

Comparison of theoretical and real surface roughness in face milling with octagonal and circular inserts

Various modeling techniques have applied by researchers to predict values of surface roughness parameters in different metal cutting processes. Some examples of these methods are briefly introduced. After this an analytical model and investigation method are presented which were used to make predictions of the expected values of surface roughness parameters. Cutting experiments were performed to obtain real roughness data and to validate the proposed and realised model by face milling of 42CrMo4 specimens with two different insert shapes. Conditions and results of these experimental investigations are presented in the subsequent part of the paper, and finally the determined approximation relations are introduced that can be used to calculate the expected roughness values from theoretical data.

Some Aspects of the Hard Machining of Bore Holes

The machining of hardened surfaces can be done even fulfilling the ever stricter accuracy and quality prescriptions, besides the economic efficiency. Decisively, hard machining is highlightedly important in finish processes because the components must meet increased functional demands. Therefore the number and/or the hardness of the hard surfaces on the components is continuously increasing. In practice the demand for such components is high since they are more wear resistant and their tool life may be higher. Today there are several possibilities for finish machining of components having hard surfaces. We have done experiments for hard machining of inner cylindrical surfaces. The examined procedures were as follows: grinding, hard turning, combined machining. The first two procedures (hard turning, grinding) have got different procedure-specific advantages and disadvantages. Combining these two procedures, using-up the advantages of them, the efficiency of the production can be increased. This paper outlines these procedures of hard machining, their applicability, the increase of their efficiency, and the possibilities provided by the combination of the procedures.

A New Strategy in Face Milling - Inverse Cutting Technology

The article describes a new technology in milling of the flat surfaces - Inverse Cutting Technology. The theoretical basics of the inverse cutting are formulated. The boundary conditions of the process depending on the cutting parameters are presented. The chip formation and chip flow by inverse milling are simulated. The comparison of cutting forces by conventional and inverse face milling is shown. Finally, cutting experiments were conducted to confirm the results of the 3D-FEM-simulation.

Thermotechnical modelling of hard turning: A computational fluid dynamics approach

Abstract During hard turning the original hardness of the surface layer changes, as does its texture structure and stress state. Even cracks and other defects may appear if the heat effect is too intense. As experimental investigations into heat effects are difficult and expensive, simulation investigation methods based on modelling are of great significance. In this paper an example of heat modelling of hard turning is presented. The layer thickness on the workpiece surface that reaches high temperature is determined. In that layer different modifications can occur due to heat. It was found that the thickness of the layer affected by heat depends primarily on the feed and only secondarily on other cutting parameters. The cooling gradient of the layer was determined, allowing conclusions to be drawn on the re-tempering of the heated layer. The computational fluid dynamics method and a commercial software was used for the modelling and proved to be suitable for the simulation analysis of the hard turning process.

Diamond grinding wheels production study with the use of the finite element method

Graphical abstract

Investigation of residual stresses in case of hard turning of case hardened 16MnCr5 Steel

In this paper the residual stresses are investigated emerging in the machined layer during hard turning in case of chip removal done by different tool rake angles. By means of finite element method simulation we examined what rake angle is best to complete cutting so that favourable residual stress values are gained in the machined surface layer.