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.
Injection molding is a polymer processing technology used for manufacturing parts with elastic hinges. Elastic hinges are widely used in FMCG (Fast Moving Consumer Goods) packaging (e.g., bottle closures of shampoos, sauces) and in the electrical engineering industry. Elastic hinge is a thin film that connect two regions of the injection molded part, where significant shear rates are present, which can lead to the degradation of polymers and the decrease in mechanical properties. Selective induction heating is the method that improves the flow of the polymer melt through thin regions by the local increase in mold temperature. In this study, selective induction heating was used to improve mechanical properties of elastic hinges by the reduction of material degradation due to high shear rates. To verify the change of shear rates, selective induction heating simulation and injection molding simulations were performed. The linear relation between mold temperature and maximum shear rate in the cross-section was identified and the mechanical tests showed significant differences in hinge stiffness, tensile strength and elongation at break.
A production line is a fundament of modern high scale FMCG industry. The performance of the line depends on various factors, out of which breakdowns, cleanings and changeovers play the most important role. The paper describes the idea of modeling production line performance by its decomposition into discrete subsystems. Every machine or workstation together with preceding buffer constitute a single subsystem, which is characterized by statistical distributions of time to repair, time between failures, processing speed and capacity. Time dedicated for cleaning and changing format parts between different production batches is also considered in the model. Subsystems are connected with each other by conveyors. The model was simulated by the given time step. In order to verify the simulation results, the data from the real production line were compared and used for adjusting the parameters of the model. The described specimen consisted of six workstations connected with conveyors. There was one high capacity buffer between the second and third station. The efficiency of the whole line as well breakdown time characterizing every machine was captured by data acquisition system. Based on the given data, the parameters of statistical distributions of time to repair and time between failures were estimated by approximation to known distributions. In addition, statistical distributions of cleaning and changeover time were derived in order to provide general performance of the production line. Genetic algorithm was introduced to optimize the line parameters in order to achieve higher efficiency and to identify potential bottlenecks.
The use of selective induction heating of molding surfaces allows for better filling of molding cavities and has a positive effect on the properties of molded products. This is particularly important in the production of parts that include flexible hinges, which are thin plastic layers connecting two or more parts of the product. By using hinges, it is possible to expand the use of injection molding products and their capabilities. They are widely used in the production of parts for the electrical engineering industry and for packaging Fast Moving Consumer Goods (FMCG). The use of hinges also entails specific reductions in wall thickness. Increases in the shear rate can be expected, which can lead to the degradation of polymers and deterioration of mechanical properties of materials. This paper investigates injection molded flexible hinge parts manufactured with selective induction heating to improve their properties. To verify the efficiency of reduction of material degradation due to high shear rates, open/close tests of elastic hinges were performed. The linear relation between the number of cycles the hinges can withstand, mold temperature and injection time was identified, where mold temperature was the more significant factor.
This paper presents a new method of aligning workpieces for machining by means of optical measurements followed by the results of verifi cation tests of this method. The overview of modern assessment methods of irregularly shaped blanks are discussed in this study, with particular emphasis on cast iron castings, as well as on problems related to their positioning and fi xing for machining. A fl owchart of the proposed method and its verifi cation results in industrial conditions are also presented. The essence of the method is based on the comparison of two spatial models: a designed workpiece model and the actual model of a casting produced with a coordinate measuring technique. A series of six iron castings were tested. The obtained results indicate that the errors caused by locating amounted to a maximum of 2 mm (average 0.5 mm) and were three times lower than actual machining allowances. This points to the correctness of the developed method and the great potential for its industrial application. Additionally, a method for improving locating accuracy by modifying the shape of the retaining pin is presented.
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