In recent years, Japan's manufacturing industries have faced severe competition in raising processing efficiency while lowering costs, and one way companies have approached this challenge is by moving production facilities overseas. Although such moves are understandable as a business decision, so it would be inappropriate to criticize this trend, the fact remains that this overseas shift tends to send Japanese expertise and skills out of the country, "hollowing out" the manufacturing firms left in Japan. Today, Japanese manufacturers face not only the dual challenge of raising processing efficiency while lowering costs but also the even bigger challenge of manufacturing high-quality products that exceed the high quality levels achieved so far. With this in mind, let us examine the machines that MITUTOYO exhibited at this year's JIMTOF (Japan International Machine Tool Fair).

Two approaches can be taken to ensure both high productivity and high-quality production: (1) install high-precision machine tools made of high-precision parts, or (2) build an autonomous machining line system that features integrated high-precision measuring instruments. The first approach entails considerable equipment installation costs and is not well-suited to mass production. Also, its effectiveness is not guaranteed, and depends largely on the production environment. The latter approach entails redesigning the manufacturing lines and connecting highly reliable measuring instruments to machining lines. This approach has garnered some attention, since it appears to be effective both in boosting processing efficiency and ensuring high processing quality. Let us examine MITUTOYO's new MACH-V product as an example of a coordinate measuring machine suited for use with the latter approach.


Requirements for coordinate measuring machines

Coordinate measuring machines (CMMs) are measuring instruments that convert workpiece dimensions and other geometric values to coordinate values. In fact, they are rather sophisticated measuring instruments that are able to measure any three-dimensional surface with high accuracy. Once converted to coordinate values, the measurement data is fed back to machine tools. As such, CMMs are a key component for building an autonomous processing system. In the past, coordinate measuring machines typically have been used for highly precise and efficient measurements, often installed in inspection rooms. However, with requirements changing as noted above, CMMs are now being moved closer to the manufacturing facilities, where they can serve as part of the manufacturing equipment. Let us now examine today's user needs for CMMs.

Consider, for example, the automotive industry, an industry that has an especially heavy dependence on production using machine tools. <1> the need for strict quality control at each manufacturing process has meant there are more measurement sites, hence there is a need for faster throughput. <2> Measurements must be taken immediately after parts are input to the machining line and processed, and so there are needs for better environmental resistance and temperature compensation. <3> Another goal is to minimize down time, which will require improvements in reliability, durability, and maintainability. <3> Nowadays, companies are devising their own quality control methods and inspection capabilities and are naturally seeking further improvements in automation and other labor-saving improvements. In today's business environment, companies must be able to provide more individualized, "custom-order" type of manufacturing operations as part of their approach to quality control and production line design. It is against this backdrop that the MACH-V is being proposed as a strategic product that offers a measurement solution for these requirements.

Mechanical structure of MACH-V

The MACH-V's structure is the product of MITUTOYO's highly reliable machine design capabilities, cultivated over many years. To meet the user needs described above, mechanical structures must enable either in-line or line-side connections, and must facilitate the conveyance of the target workpieces. Starting in 1968, MITUTOYO has achieved excellent results using bridge mechanisms with fixed columns. This is the original structure that has been used in MITUTOYO's successful line of CMMs, including Type A and Type F, whose distinctive shape draws from the company's long experience in achieving high reliability and from its accumulated expertise in product development. For workpiece conveyance, these CMMs feature a cantilever structure that enables both front and side access. They also use a linear guide system that takes the on-site environment into account.

These CMMs also help preserve work space with a compact design for a smaller footprint. Their structure also includes special features, such as use of highly rigid castings and an X-beam center drive system (for which MITUTOYO holds a patent). The major structural parts for each axis and drive system are placed close together, and everything is fully covered to provide protection from temperature changes and other environmental factors. Another vital factor for maintaining high-quality manufacturing lines with fewer periodic inspections and less downtime is to make sure that machine structures enable easy access by maintenance staff. It is therefore important to maintain open space around these machines whenever possible.

MACH-V specifications

MACH-V model 9106 with an X-axis measuring range of 900 mm has been developed, and models with 500 mm and 700 mm measuring ranges are planned. The indication error (E) in these models is a mere 2.5 + 3L/1000 μm, while the maximum drive speed is 866 mm/s, the measuring speed is 20 mm/s, and the acceleration speed is 0.86 G. Accuracy is guaranteed at temperatures ranging from 15^oC to 35^oC. This product has been designed with power train-related workpieces in mind. MITUTOYO also offers a lateral MACH model designed for high speed and high throughput.

Table 1. MACH-V Specifications

MACH-V565 MACH-V796 MACH-V9106 Measuring range mm X 500 700 900 Y 600 900 1000 Z 500 600 600 Indication error 2.5+3L/1000 μm (classified according to temperature) Maximum speed 866mm/s (3 axes) Measuring speed 20mm/s Maximum acceleration speed 0.86G (3 axes) Temperature 15 to 35oC

Issues when connecting measuring instruments to machining lines

The following touches briefly upon issues they may be encountered when using MACH-V measuring instruments or other machines with similar design concepts. Although mechanisms are designed to meet certain requirements, each finished mechanism is only part of the overall measurement solution. Many technical advances must be made to meet customer needs. One of the first issues to be addressed is the methodology for line integration. Line integration requires responses to individual customer needs, which means a "custom-order" type of approach that tends to increase costs. To minimize costs, a standardized system is needed. However, additional costs are engendered by the process-specific part measurement program that is needed to support the system's operations. As the number of measurement sites increase, more labor is required to create the corresponding programs for each process. Measuring instruments have a rather distinctive impact on machining line operations when a teaching method is used to create these programs. Consequently, there is a need for systems that can generate such programs off-line, or that include a CAD-based auto programming function. Another essential component is the technology used to control or compensate for the temperature of workpieces being machined. At MITUTOYO, such technology is an integrated part of the total measurement solution. In short, the challenge is to develop measuring instruments with ever higher accuracy and faster speed, while keeping pace with advances in machine tool technology, so that progress can be made without any reduction in guaranteed quality.

As the place where all of the new technologies supporting Japan's manufacturing industries are on display, JIMTOF gives engineers an unbeatable opportunity to expand their knowledge. Besides checking out what competitors are doing, MITUTOYO engineers must make the entire manufacturing system their frame of reference at JIMTOF. They can also expect to gain valuable information from exhibits that describe trends in related industries as they stay on the lookout for new and better solutions.

Published in "Monthly Magazine The Tool Engineer (Japanese only)" by The Publishing Taigashuppan Co., Ltd. November, 2004.