This paper describes results of experimental research on the thin microhardened surface layer of a machined surface that occurs in materials using wire electrical discharge machining (WEDM) with brass wire electrode. The direct influence of microhardened surface layer on resulting machined surface quality of tool steel EN X210Cr12 (W.-Nr. 1.2080) was examined. The aim of the experiment was to contribute to the knowledge of mutual interactions between main WEDM technological parameters, the influence of these parameters on the total affected depth, and on the variation of microhardness of sub-surface layers of machined surface. Based on the microhardness experimental measurements, mathematical models were established by the Least Square Method (LSM) in order to simulate and predict final quality of machined surface after WEDM. Recommendations are given for setting the main technological parameters of the discharge process concerning minimization of total microhardened surface layer depth and microhardened surface layer homogeneity along the whole cross-section profile of the machined surface.

Abstract:The paper describes the results of the experimental research of the heat affected zone (HAZ) of an eroded surface after die-sinking electrical discharge machining (EDM). The research was carried out on chrome-molybdenum-vanadium alloyed tool steel EN X32CrMoV12-28 (W.-Nr. 1.2365) after die-sinking EDM with a SF-Cu electrode. The aim of the experimental measurements was to contribute to the database of knowledge that characterizes the significant impact of the main technological and process parameters on the eroded surface properties during die-sinking EDM. The quality of the eroded surface was assessed from the viewpoint of surface roughness, microhardness variation, and the total HAZ depth of the thin sub-surface layer adjacent to the eroded surface. On the basis of measurement results, mathematical models were established by statistical methods. These models can be applied for computer simulation and prediction of the resultant quality of the machined surface after die-sinking EDM. The results achieved by simulation were compared with the results of experimental measurements and high correlation indexes between the predicted and real values were achieved. Suggested mathematical models can be also applied for the determination of the optimal combination of significant technological parameters in order to minimize microhardness and total HAZ depth variations of tool steel EN X32CrMoV12-28 after die-sinking EDM with a SF-Cu electrode.

Abstract:The geometrical accuracy of the machined surface can generally be understood mainly as accuracy of shape, orientation, position and run-out. As a general rule; it is quantified by the corresponding deviations from the nominal area. The size of the geometric deviation from the nominal area may in practice affect the conventionally measured value of the dimension, even if the required dimensional tolerance is adhered to. Since electro-erosive machining technology belongs to very precise finishing technologies; even the small geometrical accuracy deviation has a negative impact on the resulting quality of machined surfaces. The aim of the experiments was to contribute to the knowledge database, which defines the influence of the process parameters at electrical discharge machining with the CuZn37 tool electrode on errors of geometrical accuracy of the machined surface. On the basis of the results of the experimental measurements, graphical dependencies were determined which predict geometrical accuracy of the machined surface in terms of the maximum deviation of flatness after electrical discharge machining of tool steel EN X30WCrV9-3 (W.-Nr. 1.2581) with CuZn37 wire electrode of 0.20 mm diameter to determine the appropriate combination of process parameters.

The paper presents study on energy gain increase of the solar collectors equipped with automatic system which serves for the purpose of changing inclination of the collectors according to the sun ecliptic. The system effectiveness is compared with fixed collectors energy gain.

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In capability evaluation of measuring devices on the basis of diagnostics, it is important to compare variability of measurement with certain proportion of tolerance zone width of observed qualitative parameter. Determined index of capability of particular measuring device indicates its applicability for inspection of selected qualitative parameters in a given tolerance range. The paper is focused on evaluation of capability of digital micrometer DIGIMATIC within its entire measuring range (0 to 25mm) by the means of capability index Cgm and Cgmk. Evaluation of capability of the given measuring device was carried out by repeated measurements of standards with dimensions representing lower, middle and upper range of the measuring instrument at given accuracy (2μm) of measuring device.

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Modern heating furnaces use combined modes of heating the charge. At high heating temperatures, more radiation heating is used; at lower temperatures, more convection heating is used. In large heating furnaces, such as pusher furnaces, it is necessary to monitor the heating of the material zonally. Zonal heating allows the appropriate thermal regime to be set in each zone, according to the desired parameters for heating the charge. The problem for each heating furnace is to set the optimum thermal regime so that at the end of the heating, after the material has been cross-sectioned, there is a uniform temperature field with a minimum temperature differential. In order to evaluate the heating of the charge, a mathematical model was developed to calculate the heat fluxes of the moving charge (slabs) along the length of the pusher furnace. The obtained results are based on experimental measurements on a test slab on which thermocouples were installed, and data acquisition was provided by a TERMOPHIL-stor data logger placed directly on the slab. Most of the developed models focus only on energy balance assessment or external heat exchange. The results from the model created showed reserves for changing the thermal regimes in the different zones. The developed model was used to compare the heating evaluation of the slabs after the rebuilding of the pusher furnace. Changing the furnace parameters and altering the heat fluxes or heating regimes in each zone contributed to more uniform heating and a reduction in specific heat consumption. The developed mathematical heat flux model is applicable as part of the powerful tools for monitoring and controlling the thermal condition of the charge inside the furnace as well as evaluating the operating condition of such furnaces.