| With fast development of the automotive industry in China, and fierce competition after WTO in China, vehicle quality and performance will surely be hard indicators of contest. The high level of of automotive production quality is mainly reflected in speed, acceleration, energy-saving, low noise, low fuel consumption, etc. To achieve these technical indicators, it is necessary to have high-precision, high-quality, advanced-design engine, gearbox and transmission system, and so on. High precision of these auto parts manufacture and assembly inevitably demand for sophisticated, high-precision detection, and strict quality control. CMM (Coordinate Measuring Machine) is a clear indication of an enterprise quality control level. At present, to meet requirements of international automotive industry to suppliers for quality system, domestic engine manufacturers and automotive manufacturers have adopted the automotive industry quality standard ISO/TS16949: 002 quality certification, and have purchased various types of high precision coordinate measurement measuring machine to keep quality of whole process production and assembly in control. Two parts of the quality control of processes that affect automotive engine product quality as machining, assembly were detailed in this thesis. First, an important process in quality control - through extensive application of CMM in the machining production to clarify the importance and necessity of CMM in quality control of the engine was studied. Secondly, the causes of CMM measurement uncertainty was discussed and compensation methods were given by examples . The main contents of this thesis include:1) The coordinate detection program of main components of the automotive engine was prepared, the measurement device is PMMC700 with high precision and high speed made in Germany, the computer software applied is QUINDOS measurement software.2) For the structural features of automotive engine cylinder head, cylinder block, crankshaft and other major parts, positioned clamp apparatus are designed to facilitate test, and applied in practical work. 3) The program for CMM precision test and measurement systems analysis was made to determine its accuracy.4) Through examples of measuring, the CMM uncertainty of measurement was determined to compensate error of measurement results.5) Through a large amount of measurement practice, items to be noticed when preparing CMM procedures, and different measurement schemes for the same target were proposed6) Solutions for traditional CMM measurement difficulties were proposed. For CMM specific application in quality control of automotive engine, five aspects were researched mainly:1) Application of CMM in the acceptance of engine factory equipments: under normal circumstances, engine factory will buy processing production lines of engine cylinder block, cylinder head, crankshaft, connecting rod, the acceptance of any one of these processing production line equipment should be finished with the coordination of CMM, from initial commissioning of equipment to efficiency verification, all processed products must be adopted by CMM detection, calculation of equipment processing capacity index from measurement results can determine whether the processing production line is qualified based on the results.2) CMM in application of daily processing of engine: for processing lines after acceptance test into the batch production stage, and the CMM will do opportunity tests of machined processes parts, with a daily adjustment and repair of processing production line with problems, weekly full-size measurement of products in processes and completed measurement so as to control the quality of process sequences.3) Measurement of CMM for inspection tools: the mechanical processing site is inseparable from the inspection tools, which is a powerful means of quality control at site. With a high machining accuracy and a high frequency of use, the decrease of inspection tools accuracy may cause products scrapping in series. Measurement-type CMM is the only way to check inspection tools at test site. Through the measurement testing process of a cylinder head inspection tool, the application of CMM in this work is illustrated.4) Measuring application of CMM in products is illustrated through application examples: the part of quality audits in quality system certification is a quality control work as well as a quality assurance activity. A CMM testing of engine plant processed products provides basis and object of audit for certification bodies, which is the basis for all fundamental work.CMM will have more and more opportunities for the application to the processing system and become a component of high-quality products processing. With its very powerful statistical functions, CMM can control quality for processing with its application of statistical techniques, thus preventing the formation of unqualified products, and to reduce waste and provide original basis for continuous improvement process. Through CMM software products measurement data can be collected, collated, analyzed to produce quality control charts such as histogram and diagram, and analyze the reliability of measurement data, so as to asses and monitor various stages of production and processing to guarantee product quality.
|
PDF Full Text Request