Development status of coordinate measuring machine

Since the 1960s, industrial production has developed greatly. Especially after the rise of machine tools, machinery, automobiles, aerospace and electronics industries, the development and production of various complex parts requires advanced detection technology and instruments, thus reflecting three-dimensionality. The measurement technology of the CMM came into being and quickly developed and improved.

As a new high-efficiency precision measuring instrument developed in the past 30 years, CMM has been widely used in machinery manufacturing, electronics, automotive and aerospace industries. It can measure the size, shape and mutual position of parts and components, such as the measurement of space profiles such as cabinets, guides, turbines and blades, cylinders, cams, gears, and bodies. In addition, it can also be used for scribing, centering holes, lithography integrated circuits, etc., and can scan continuous surfaces and prepare machining programs for CNC machine tools. Because of its versatility, large measuring range, high precision, high efficiency, good performance and connection with flexible manufacturing systems, it has become a large-scale precision instrument, so it is called the “measure center”.

1. The effect of three coordinate measuring machine on three-dimensional measurement

The advent of coordinate measuring machines is a milestone in the transition of marking measuring instruments from classical manual mode to modern automated testing technology. The CMM plays an important role in 3D measurement technology in the following aspects: (1) Solving the measurement of the contour size of complex shapes, such as the aperture and hole position of the box parts, the blades and gears, the dimensions of the car and the aircraft, etc. (2) Improve the accuracy of three-dimensional measurement. At present, the single-axis precision of the high-precision coordinate measuring machine can reach 1um or less within the length of each meter, and the accuracy of the three-dimensional space can reach 1um~2um. For the coordinate measuring machine for workshop testing, the single axis of measurement accuracy per meter can also reach 3um~4um. (3) As the coordinate measuring machine can be combined with CNC machine tools and machining centers to form a production processing line or flexible manufacturing system, which promotes the development of automated production lines; (4) With the continuous improvement of the accuracy of the coordinate measuring machine, the degree of automation continues Development has promoted the advancement of 3D measurement technology and greatly improved measurement efficiency. In particular, the introduction of electronic computers not only facilitates data processing, but also completes the NCN control function, which can shorten the measurement time by more than 90%. The attached table lists the efficiency comparison between the CMM and the traditional method.

2. Research status of CMMs at home and abroad

The world's first measuring machine was made in the UK in 1959. Nowadays, applications at home and abroad are quite common. According to the statistics of international professional consulting companies, the sales growth rate of CMMs is around 7%~25%. The developed countries have a high volume, but the growth rate is decreasing year by year, about 7% to 10%; the developing countries have a low amount of ownership, but the growth rate is increasing, about 15% to 25%. At present, the domestic and international coordinate measuring machines are developing rapidly. There are more than 50 manufacturers of measuring machines in the world, and the variety specifications have reached more than 300.

(1) Foreign profile

There are many foreign CMM manufacturers, and there are many varieties in the series. Most of them have scribing functions. Well-known foreign manufacturers include Zeiss and Leitz in Germany, DEA in Italy, Brown-Sharp in the US, and Mitutoyo in Japan.

In general, foreign machines have the following characteristics: a. Most of the machines are generally cantilevered, with good spatial openness, easy to install large parts or complete vehicles. b. Optimized by "AutoCAD" and finite element method Design, reasonable structure, beautiful shape; c. Special development strength, special software and accessories, can meet the special needs of more users; d. Most of the moving parts are made of alloy aluminum, the moving parts are as small as possible, do High rigidity, low inertia; e. 21 error compensation software, which can improve machine accuracy at low cost; f. With 32-bit DSP continuous trajectory control system, it is a data signal processor with better performance than CPU. It is a very large scale integrated circuit. In addition to its high computational and control functions, it also has many high-level language programs for internal storage that can be developed. g. Most machines use Renishow's (UK) electrical probes, which are fully functional and reliable. Equipped with fully functional control measurement software, special and error correction software; i. The machine's performance is highly stable and reliable, and has a long service life; j. Coordinate measuring machine is connected with computer workstation and CNC machine tool; k. Coordinate measuring machine technology In the past ten years, the development of the CNC has been leaps and bounds. In particular, the numerical control system and measurement software have been updated every two or three years. l. The series is complete in variety, and the “three-way” (ie standardization, generalization, serialization) is high.

(2) Domestic profile

Since the introduction and development of CMMs in China in the 1970s, great progress has also been made. More domestic imports are: / Zeiss and Leitz, Italy's DEA, the United States's Brown-Sharp, Japan's Mitutoyo and other companies. The domestic production units have also developed greatly. The main manufacturers include China Aviation Precision Machinery Research Institute, Qingdao Sentinel Yingkefa Measuring Equipment Co., Ltd., Shanghai Machine Tool Plant, Beijing Machine Tool Research Institute, Harbin Measuring and Cutting Tool Factory. Kunming Machine Tool Plant and Xintianguang Instrument Factory. Nowadays, China has the capacity to produce hundreds of different types of coordinate measuring machines per year.

The domestic three-coordinate measuring machine has developed rapidly in the past ten years, but there are still some gaps compared with foreign countries, mainly in the following aspects: fewer varieties of series, low degree of “three-oriented”; long period of new product development, mainly due to components It is difficult to support materials; long machining cycle; product stability is poor, especially electronic control system, poor reliability, high failure rate, relatively low life, and relatively few software functions, especially special software. Less, networking with computer workstations and CNC machine tools, only a very small number of measuring machines have just started, most machines have not yet begun this work, pending further development and research.

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