The presented publication demonstrates an accuracy assessment method for machine tool body casting utilizing an optical scanner and reference model of the machine tool body. The process allows assessing the casting shape accuracy, as well as determining whether the size of the allowances of all work surfaces is sufficient for appropriate machining, corresponding to the construction design. The described method enables dispensing with the arduous manual operation of marking out as well as shortening the time of aligning and fixing the casting body for machining. For the experimental setup, four rotary indexing table castings were investigated according to the method principles. The geometric accuracy of each casting was examined by comparing their scans with the computer-aided design model, and the machining allowances were evaluated to determine casting qualification for machining. The nominal volume of material to be removed was established and subsequently optimized to reduce the volume to be machined. Thus, a rapid method of aligning a casting in a machine tool according to the planned optimized distribution of machining allowances was developed. For the set of measured castings, it was proven that their poor geometric quality precluded the possibility of further machining according to standard marking out instructions. However, by following the presented methodology, it was possible to successfully process the entire set while reducing the overall volume of the material removed by 4.5-9.6%, as compared with nominal values. The obtained results ultimately confirmed that manual marking out could be eliminated from the casting assessment process.
The paper deals with the theoretical basics of forming the face toothings in flat wheels of spiroid gears by means of a single cutting edge tool, using NC machine tools. Based on kinematicsgeometrical formulas, geometrical models of creating the tooth spaces, as well as a determination of the modification depth along the tooth line, are described. Equations of the tooth line have been calculated as well as mathematical formulas enabling the determination of the modification depth, assuming the correct matching of the worm with the flat wheel of the spiroid gear. Based on geometrical models and mathematical formulas algorithms were elaborated in order to determine the envelope condition and modification depth of the tooth line. Then, on the basis of algorithms, computer programs that are going to be used to design the flat spiroid gears and to calculate their geometrical dimensions were proposed. The modification depth along the tooth line was also illustrated. The simulation results have been illustrated by the gear example. Finally, two methods of machining the face toothings in spiroid gears with a single edge-cutting tool are presented: accurate and approximate ones. Based on algorithms and programs, a comparative simulation of both methods was elaborated.
The accuracy and the repeatability of tool positioning in relation to the work piece is one of the most important features in contemporary NC lathes. Precise lathes are particularly required in the automotive industry. The applied designs of the NC lathe slides do not always assure the required thermal stability of work piece dimensions. It has been observed that during the continuous work time of the one of the world’s famous lathes, the X and the Z axes have been significantly deformed by means of thermal influence. Diagnostic investigations concerning the positioning accuracy have been performed according to the ISO 230/3 standard [7]. While investigations, unpermitted values of thermal deformations in both slide axes, have been observed. The design of the slides has been analyzed and an attempt has been made to minimize the positioning errors that are influenced by thermal deformations. Particular attention has been paid to the errors of the X axis as they influence directly upon the accuracy of the work piece cross dimensions. A new method of deformation compensations for the X axis has been elaborated. The method is based on the elongation measuring of the ball screw applied in cross slides and then programmed compensation in the X axis control system. The practical effectiveness of the introduced compensation method has been confirmed and a five times increase of the machining accuracy has been obtained.
The hereby presented study puts forth the fundamentals of an innovative technology enabling rapid assessment of machine tool cast shape by elimination of manual marking out requirement and machining surplus minimization. The new technique is based on optical measuring system utilization for the design of virtual cast models and their comparative analysis with structural models. Two small scale machine tool body casts were selected for the investigation. The measurements were conducted in triplicate series for each cast labeled with reference markers, by means of Atos GOM II optical scanner. For further comparison, one of the casts was additionally scanned without labeling. Flatness parameters of selected cast surfaces were determined for geometric accuracy evaluation and the scanned cast shapes were compared with reference models. The comparison results were recorded as multicolored maps projected upon the experimental cast and reference model surfaces. Practical map interpretation was further elucidated and the surplus sizes on the machined surfaces were assessed accordingly. Comparative analyses of individual models were demonstrated for all measurement series of both casts, affording reproducibility evaluation of optical scanning system measurements. Economic viability of the proposed technology market implementation was unequivocally established, as it provides for considerable reduction in the cast machining scale as well as the quality control of 100%.
The aim of this work is to compare the effectiveness of two induction heating methods of injection molds by means of thermovision measurement. The problem of selecting external or internal induction heating for thin-walled moldings used in electrical and electronic industry is taken into consideration. At first, the boundary conditions were defined. Then a group of three moldings with different defects were selected. The defects that have been taken to remove by means of induction heating are: weld lines, breaking hinges, air traps and diesel effect. In order to compare the methods of heating two models were created. The first one was made as a block of steel with milled grooves with a width of 2mm and a depth varying from 1 to 12mm. The second model consisted of two parts, one being placed in the second. The research stand consisted of prepared models, induction generator with power of 10kW, specially shaped inductor, thermovision camera and temperature sensor of PT100 type as a reference. First, the surface with milled grooves was heated in four different sectors (because of the shape of inductor) in time of 2s. The area of low-depth grooves heated up to 154°C while the surface with 12 mm grooves heated up to 120°C. It comes from eddy currents flowing. This phenomenon shows that effectiveness of external heating of grooved surface decreases with increasing of grooves depth. In the second case the cavity insert was heated as a coil inside the inductor which was located inside the mold. The measured value was the time of heat transfer from heated area to the forming surface in three configurations.
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