Mirko Soković

Ecological aspects of the cutting fluids and its influence on quantifiable parameters of the cutting processes

Abstract This contribution gives an analysis of the ecological parameters of the cutting fluids and its influence on the machinability parameters. Evaluation of quality parameters of the cutting fluids is based on output parameters of production process considering also ecological norms. Some results of machinability tests, which were done in tapping threads into standard reference steel C 45 E4 and Al-alloy AlMgSiPbBi for free cutting show how it is possible to achieve acceptable machinability parameters by use of new environment-friendly cutting fluid. The cutting parameters were chosen from the technological database with respect to particular machined material/cutting tool combinations. This approach has been used to quantify the performance of the existing products, compare products in the marketplace, and search for novel cutting aid additives.

Tribology of coated tools in conventional and HSC machining

Abstract The aim of research of the tribological conditions in the tool–workpiece interface in cutting processes is to find the main causes for unpredicted tool life. As is shown in the paper there are many causes for their influences on the tool wear. Not only mechanical and chemical but also thermo-chemical aspects of wear is important. The high cutting temperature, which is a result of high-speed cutting (HSC), enhances diffusion and oxidation process. Diffusion processes between the chip and the top rake surface of the cutting edge result in crater wear, and oxidation reactions with the environment induce scaling of the cutting edge. The phenomenon of central wear can be used to define the tool life in the case of HSC milling of alloyed tool steels ( hardness >45 HRC ) .

Model of complex optimization of cutting conditions

Modern flexible production with its JUST-IN-TIME philosophy requires efficient organization, high quality tools, selected machining materials with defined mechanical and technological properties and continual determination and optimization of cutting conditions. Therefore, for successful production it is necessary to carry out a number of studies with the purpose to optimize the cutting conditions which should include understanding of tribological problems, the cutting material properties, cooling agent and its application. The rationality and economy of manufacturing which are a result of material and energy saving and shorter machining times, depend to a large extent on the right choice of selected cutting conditions and required product quality. This paper deals with the development of a model for complex optimization of cutting conditions showing that the right way from optimal cutting conditions to product quality is via process quality.

On the inter-relationships of some machinability parameters in finish machining with cermet TiN (PVD) coated tools

Abstract This paper presents some results of machinability tests which were done by finish machining of Ck 45 steel with TiN (PVD) coated and uncoated cermet tools. We exploited the advantages of the good properties of cermet and TiN (PVD) coating and analysed the results of machining with such a cutting tool. We used tool holders with entering angles which are very frequently found in modern machining operations. Machinability tests were also supported with some statistical analysis and modelling techniques.

Pre-processing of point-data from contact and optical 3D digitization sensors.

Contemporary 3D digitization systems employed by reverse engineering (RE) feature ever-growing scanning speeds with the ability to generate large quantity of points in a unit of time. Although advantageous for the quality and efficiency of RE modelling, the huge number of point datas can turn into a serious practical problem, later on, when the CAD model is generated. In addition, 3D digitization processes are very often plagued by measuring errors, which can be attributed to the very nature of measuring systems, various characteristics of the digitized objects and subjective errors by the operator, which also contribute to problems in the CAD model generation process. This paper presents an integral system for the pre-processing of point data, i.e., filtering, smoothing and reduction, based on a cross-sectional RE approach. In the course of the proposed system development, major emphasis was placed on the module for point data reduction, which was designed according to a novel approach with integrated deviation analysis and fuzzy logic reasoning. The developed system was verified through its application on three case studies, on point data from objects of versatile geometries obtained by contact and laser 3D digitization systems. The obtained results demonstrate the effectiveness of the system.

Dimensional accuracy and cost optimisation in the finish machining of cold formed parts

Abstract In the modern market-driven economy, there is a constant pressure to reduce all kinds of costs, the amount of work and the energy consumption. If parts have appropriate shapes, material and quantities, a combination of cold forming and subsequent finish machining offers very promising solutions. The results can be much better if the forming technology can ensure a high form and dimensional accuracy, high surface quality and a narrow tolerance field of parts. Accordingly, a strong growth can be observed in the introduction of the Near-Net-Shape technology into that kind of production which is already now well established in mass production (of automobile parts, kitchen appliances and hand tools). The critical point of unification of two completely different technologies is an integral description of the parts after cold forming, and especially, a non-uniform stress–strain distribution inside them. The fluctuation of these properties together with geometrical fluctuations can have a strong impact on the latter quality of finish machining processes. For a successful Near-Net-Shape Forming (NNSF) implementation, it is, therefore, first necessary to define the lower and upper limits of the parameters affecting finish machining, and second, to maintain them under control.

Improvement of tool life of die-casting tools with duplex treatment

A comparative tool life test of protected tools was made in aluminium die-casting of driving wheels for automobiles with two types of cores in one casting plate. One set of cores was improved with plasma nitriding process, while another one was improved with duplex treatment (plasma nitriding + PVD CrN coating). After 2700 and 4150 shots, surfaces on both types of tools were analysed using optical and scanning electron microscopes to identify damages of tool working surfaces. The performance tests, made under real manufacturing conditions, showed that wear of duplex treated tool is smaller compare to only plasma nitrided tool.

Cutting Properties of PVD and CVD Coated A2lO 3 + TiC Tool Ceramic

The paper presents investigation results of tribological and cutting properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from the Al2O3 + TiC tool ceramics. Tests were carried out on the inserts made from ceramics, uncoated and PVD or CVD-coated with gradient, mono-, multilayer and multicomponent hard wear resistant coatings composed of TiN, TiCN, TiAlN, TiAlSiN and Al2O3 layers. Substrate hardness tests and micro hardness tests of the deposited coatings were made on the ultra-micro-hardness tester. It was demonstrated, basing on the technological cutting tests of grey cast iron (260 HB), that putting down onto the tool ceramics the thin anti-wear PVD and CVD coatings increases their abrasion wear resistance, which has a direct effect on extending tool life of the cutting edge.

Scanning errors identification using touch trigger probe head

The objective of this research presented in this paper is to generate mathematical model, which combines ball tip radius error and small tilt of the stylus to determine translational motion (in two directions) of the stylus ball centre, due to the surface slope. In simple two-dimensional mathematical model is described one error. Second model is based on 3D-mathematical model, which is a basis to determine (and plot) translational movement of the stylus ball according to surface slope. Scanning process on freeform surface with touch trigger probe head could not be performed very accurately, due to a number of reasons related to the stylus ball and trigger probe head errors. Translational movement of the stylus ball centre at any slope can be shown only on 4D?6D-graphs, which does not exist. Such mathematical error might be a basis to create mathematical compensation error model. Because in literature, we did not find such mathematical model to determine translational motion (in two directions) of the stylus ball centre, the contribution of the conducted research is observed in one possible view of two types of systematic errors, which may occur during surface scanning process with touch trigger probe head. [Received 13 October 2006; Accepted 3 March 2007]

Influence of TiN (PVD) coating on the tool on the identification parameters in turning

Abstract The machining of metal components involves the selection of the cutting material and the cutting tool, including the hard protective coatings on the tool, and the correct selection of the cutting parameters to be adopted on the machine which will be used to carry out the operation. Therefore, for successful production it is necessary to carry out a number of studies for the purpose of optimising the cutting conditions and to thoroughly understanding the tribological conditions at the tool–workpiece interface and the nature and characteristics of the cutting material and hard protective coating. This paper deals with the investigation of the influence of the TiN (PVD) coating on cermet tools on the identification parameters in turning.