At monozukuri sites today, line standards such as Vernier calipers, micrometers and height gauges, end standards such as gauge blocks, plug gauges and snap gauges, and other measuring instruments are used. These instruments can only evaluate a simple dimension in one direction in one measurement; accordingly they may not cover an object with a complicated shape. For example, if a positional tolerance or a deflection is measured, we will measure it with a special gauge manufactured by combining a measuring tool and a jig. A radial reflection of a cylindrical bar cannot be measured only with a dial gauge; manufacturing a jig that presses the probe of a dial gauge on the circumferential surface of a cylindrical bar enables the circumferential deflection to be evaluated.
However, special gauges to measure more complicated and advanced products such as car engine parts are large-scale apparatuses costing several million yen. Each special gauge needs to be manufactured again if the shape of the product to be measured is changed; therefore, given the circumstances where the life cycle of every product is shortened, the costs of special gauges are only increasing. Measurement where a gauge is used is called relative measurement, and a standard such as a gauge block or a master workpieces, which is a standard to set the position of sensors in a gauge to zero, is a must-have item. As part uniformity is promoted now for cost reduction, the global production of the same part by multiple manufacturers is common. Therefore, many master workpieces required for special gauges are necessary. If there are individual variations among those master workpieces, a difference would be generated between companies in different countries, which would be a problem. In gauge measurement, understanding how much the machining position is displaced in what direction is not appropriate, and there is also the problem that feeding back the correction amount to the machining equipment in the preceding process is difficult.
A 3D measuring machine was utilized the most to measure complicated objects like car engine parts to eliminate errors. Until the latter half of the 1990s though, the machine could only work in a measurement room where the temperature was controlled and set to 20°C. Most 3D measuring machines were manually operated then. They took much time for measurement and therefore mainly evaluated prototypes and even measurement of up to several sampled mass-produced items; they were completely different from the measuring instruments and gauges that were used in daily life then. Thus, the idea was that 3D measuring machines were not used in a line or beside a line.
However, in order to manage product quality at a high level in a global manner, there are limits on using the relative measurement that special gauges offer. A 3D measuring machine can be used for absolute measurement and can support various types of workpieces with a single measuring instrument due to programming or other modifications. The integration of a general-purpose machine into a line or installation of it beside a line thus enables cost reduction to be achieved with a long-term vision. We needed to newly develop a 3D measuring machine that addressed these issues because of the many problems in continuously operating the existing gate-type 3D measuring machines integrated into lines for a long time.
The MACH series are machines released on the market as CNC measuring machines to support in-line measurement. The MACH-3A, in particular, features an overwhelmingly high-speed/high-acceleration drive and enables absolute measurement in a production area with self-correction in a wide temperature range from 5 to 40°C. A wide range of workpieces can be measured with a single unit; high throughput, environmental resistance and space saving can be achieved. The MACH-3A can perform the statistical management for numerical data that enables users to find machining errors in early stages and prevents defective parts from being manufactured and flowing out as well as deciding the OK/NG, which are the same as they were with the conventional gauge management. The 24-hour operation manufacturing sites require excellent durability to achieve stable operation, drastic reduction in measurement time, accuracy assurance in a wide temperature environment and a structure design that considers safety and maintainability. In the MACH series, the in-line-capable CNC CMM integrates the functions required for measurement in-line and beside a line . This section will introduce the MACH-3A (Fig. 1) that has one of the highest speed drives in the industry in the MACH series.

Figure 1 Exterior view of in-line-compatible CNC CMM, MACH-3A 653 (The index table is an option.)

Stable quality needs to be quickly controlled at manufacturing sites. With a 3D measuring machine, the higher the specifications of (1) maximum drive speed (speed to quickly reach the specified measuring position), (2) maximum drive acceleration (speed to quickly reach the maximum speed) and (3) measurement speed (low speed from an approach distance to the moment of touching a workpiece), the shorter the time to measure one product item becomes. The MACH-3A features a maximum drive speed of 1212 mm/s, a maximum drive acceleration of 11882 mm/s² and a measurement speed of 30 mm/s, providing an industry-leading CNC 3D measuring machine. Table 1 shows the main MACH-3A 653 specifications. Table 2 compares the measurement results to measure a transmission case (positional tolerance: 4 points, inner diameter: 5 points, pitch between holes: 3 points) with the MACH-3A and a general (gate-type) 3D measuring machine. The MACH-3A has reduced measurement time by approximately 58% (compared to our product) in comparison with the general 3D measuring machine. Improved throughput thanks to this astonishing speed enables the stable quality control required in manufacturing sites.

Table 1 Main specifications of the in-line-compatible CNC CMM, MACH-3A 653

Table 2 Comparison of measurement time between the MACH-3A 653 and a general 3D measuring machine