Vol.2 No.2 2009

16/98

Research paper : High accuracy three-dimensional shape measurements for supporting manufacturing industries (S. Osawa et al.)−96−Synthesiology - English edition Vol.2 No.2 (2009) the measurement program on the first run, the measurements thereafter on the CMM can be done by computer control. Therefore, some companies simply assign measurement personnel to only conduct routine work, and depend on the manufacturer of the measuring machine to do the complex programming to cut the cost of measurements. However, it is known that there is a distinct difference between the measurements by a person with specialized knowledge of CMM and someone without such knowledge. This is because the difference in the knowledge and the ability to deal with factors such as positioning of the workpiece and temperature of the environment may affect measurements. To increase the reliability of three-dimensional measurement, it is most important to create a system where the skill of the operator can be improved without requiring profuse knowledge or prolonged training.Previously in Japan, the manufacturing process was perfected within the consolidated company group, and the system for maintaining reliability of the product was relatively well established within the companies. However, as more less-expensive, good-quality parts are obtained inside and outside Japan, and as production overseas is increased to cut the cost of labor, globalization of parts procurement increases and the system for maintaining reliability within a corporate group is collapsing. For example, flaws in assembly may become a problem because the size of parts delivered by Company A and the size of parts from Company B are slightly different. Therefore, some kind of official support has become necessary to replace the system of maintaining reliability that had been established within the consolidated company group.The aim of this research is to develop technology necessary to increase reliability of three-dimensional shape measurement, which is one of the most basic technologies that support manufacturing, and to create an official system to diffuse such system to the sites of production.2 Scenario2.1 Scenario for improving reliabilityFor the dissemination of AIST’s research results to a wide range of industries, it is necessary to create a system for delivering the results to the site of production. A scenario for wide dissemination to sites of production was drafted in advance, starting with the establishment of a high-precision national measurement standard. Figure 3 shows the scenario drafted to improve the reliability of three-dimensional shape measurement.To organize the national standard, AIST develops the standards and their calibration methods, and also will engage in the development of next-generation standards with higher precision. The reliability of three-dimensional measurement is improved by using such developments to calibrate the CMMs at the site of production. The equivalency of the established national standard will be checked by conducting international comparisons that involve the comparison of measured values with the national metrology laboratories of other countries, and the consistency of measured values based on that standard will be recognized worldwide. To diffuse the established standard in Japan, an accreditation system of calibration service is constructed, and the standard is introduced into the site of production through the service provided by the calibration service. To increase the competitiveness of local small and medium companies, training and technical support for high-precision measurement are provided to public research laboratories of each prefecture. Also, the reliability of three-dimensional shape measurement is raised at the site of production by standardizing the CMM assessment methods and the new three-dimensional shape measurement methods, and by developing a remote calibration technology to allow calibration of the CMM on-site using a simple procedure. To support Japanese companies that operate in developing countries, technical support is provided to national metrology laboratories of the developing countries. By establishing the scenario, our objective was to improve the international competitiveness of the Japanese manufacturing industry.2.2 Maintenance of traceability and goals of developmentObjective demonstration of the reliability of three-dimensional shape measurement can be achieved by establishing the traceability to the national standards. For over ten years, AIST has been engaging in technological development to establish the traceability system of three-dimensional measurement. Figure 4 shows the technological developments of the traceability system for length. For three-dimensional measurement, the system is traceable to the iodine stabilized He-Ne laser that is the national standard for length. The shape of the product manufactured is assessed by a CMM; this CMM is calibrated with a standard called Fig. 2 Outline of CMM.Probing systemContact probe (stylus)OperatorControllerZYXIn general, most CMMs employ mechanical contact points called the touch trigger probe. When the probe contacts the measured object, the mechanical contact is broken and a signal is produced.The tip of the stylus is normally a highly precise sphere made from hard material such as ruby.

※このページを正しく表示するにはFlashPlayer9以上が必要です