Shizuoka coordinate measuring machine international standard traceability
The mechanical parts for the engine components of automobiles, aircraft, and other applications require machining precision in units of μm. The 3-D coordinate measuring instruments used to measure the machining precision of such parts are also subject to possible error. Usually, the manufacturers calibrate these measuring instruments once a year or so. However, the “Quality Master” developed by Asanuma Giken enables the calibration and management of 3-D coordinate measuring instruments within 20 minutes before the start of daily work, thus ensuring compliance with world standards and traceability as certified by National Institute of Standards and Technology of the United States. This is a technology indispensable for Japanese corporations, so as not to lag behind their Western counterparts in the wake of continually advancing international specialization.
Asanuma Giken Co., Ltd. http://www.asanuma-g.jp/
Founded in 1977 as a manufacturer of industrial parts. Having been established as a maker capable of machining prototypes of automotive and aircraft parts of extremely high precision, almost all domestic car manufacturers have business with this company. In 1993, it built a new factory with a rooftop garden that provides energy saving measures for maintaining the temperature inside. In January 2003, the company was granted NVLAP certification by the National Institute of Standards and Technology, and began the manufacture and sales of gauges for 3-D coordinate measuring instruments.
By measuring this cylindrical gauge, the error of 3-D coordinate measuring instruments can be measured.
Block Gauge of a cubic form prototyped in the early stage of development
In the back is a 3-D coordinate measuring instrument manufactured by Leitz of Germany worth millions of dollars.
In a computer simulation, a very complex machine like an automobile engine can function perfectly and demonstrate its full performance, provided there are no design problems. Conversely, an actual machine that has been manufactured may not only fail to measure up to its theoretical performance, but may not work properly at all. The reason for this is the degree of error in each of the actual parts. The error of a part might be insignificant, but when it adds up, precision deviates further and further away from the theoretical values.
The smaller the degree of error, the closer the machine’s performance to design values. In order to minimize error, it is necessary to accurately measure the error of each part.
This may sound like simple logic, but such measurement requires a 3-D coordinate measuring instrument that can cost millions of dollars.
Nevertheless, such a measuring instrument itself is a “machine” composed of metal parts. Metals expand and contract due to changes in temperature or humidity, and may also deform through the aging process.
“About 20 years ago, when I delivered a prototype of a part to an automaker, a staff member yelled at me, “Your products are far from accurate!” I responded by saying, ”We use measuring instruments under strict temperature control. Your machines are no good!’”
Although the manufacturers of measuring instruments usually calibrate to eliminate such error about once a year or so, some degree of residual error can be expected depending on the environment and frequency of use.
“Though we know we provide better maintenance and our machines are more accurate, there is no means to prove it. After all, we lost because of our weaker business position, and it was frustrating indeed. Still more serious, however, was the realization that we wouldn’t be able to supply our products with confidence regarding their precision unless we did something about it.”
Mr. Asanuma became keenly aware of the need for having a measuring instrument that measures the error of measuring instruments, namely, “a ruler for rulers.” There was no such a machine in Japan at that time, and that motivated him to make one himself.
What determines the standard of length adopted by 3-D coordinate measuring instruments? In searching for the answer to this question, Mr. Asanuma frequented Germany and asked for advice and instruction at PTB (a national institute of Germany providing technical standards).
What he learned as being important there is the traceability (linkage) to world standards. The procedure is to make a standard gauge of length and measure it with a 3-D coordinate measuring instrument, so as to verify the precision of this machine in turn, but the gauge used herein must be of the same standard as designated by the certifying institutions in Germany or the United States.
A cubic design was adopted for the first prototype called Master Block, and trial production as well as measurement continued for five years. This design, however, proved to have a concentration of stress on the vertexes in case of thermal expansion, and it took 30 days to return to the original shape. In search for a more reliable gauge with little deformation, an original cylindrical gauge was newly devised. As a result of prototyping and experimental measuring for 12 years, a benchmark of 0.3 μm for the margin of error was finally achieved, in contrast to about 10 μm for the error range of automotive parts.
“We conducted measuring operations under a variety of environments in an effort to collect as much measuring data as possible.
Mr. Asanuma went to the Unites States with an enormous collection of measurement data, and in January 2003, certification was granted by the NIST (National Institute of Standards and Technology), an American national institution. Asanuma Giken is the only Japanese company with NIST certification for the field of 3-D coordinate measurement. This certification must be renewed every year, and only three companies in countries outside Japan continue to retain it.
“In the wake of advancing international specialization, there will be more cases where parts manufactured in Japan and those made overseas are assembled together. The traceability to worldwide standards will be truly indispensable in such cases. Now I am ready to have a row with overseas companies (laughing).”
What Mr. Asanuma accomplished was the development of technology that can form the basis for a “reunification of measurement standards.”
The factory has a rooftop garden which maintains the temperature inside at 25°C or below even at the peak of summer.