Technical development of gear measuring instruments

The gear gauge is a rich concept. It not only includes instruments for detecting various gears, but also instruments for detecting worm gears, worms, gear cutters and drive chains. There are many types of gears, complex geometric shapes, and numerous parameters that characterize their errors. Therefore, there are many varieties of gear gauges.

The research of gear measurement technology and its instruments has been nearly a hundred years old. In this short development process, there are 6 landmark events:

(1) In 1923, Zeiss of Germany successfully researched an instrument called "Toooth Surface Tester" for the first time in the world. It is actually a mechanically developed universal involute inspection instrument. Based on this improvement, Zeiss launched a practical instrument in 1925 and put it on the market. The instrument's length reference uses an optical glass ruler with a line spacing of 1 micron. The advent of the instrument marks the beginning of precision measurement of gears. The VG450 widely used in China is an improved product of the instrument.

(2) At the beginning of the 1950s, the emergence of the mechanical display-type universal spiral standard instrument marked the complete control of gear quality.

(3) In 1965, Dr. R. Munro of the United Kingdom developed a successful grating-type single-bit instrument, which marked the possibility of measuring the dynamic performance of the gear with high precision.

(4) In 1970, the overall gear error measurement technology developed by Chinese engineers and technicians, mainly Huang Huangnian, marked the beginning of the measurement of gears by the motion geometry method.

(5) In 1970, Fellow Corporation of the United States exhibited Microlog50 at the Chicago Exposition, marking the beginning of the use of the CNC Gear Measurement Center.

(6) At the end of the 1980s, Osaka Seiki introduced a non-contact tooth surface analyzer PS-35 based on the principle of optical holography, marking the beginning of the gear non-contact measurement method.

Looking at the development of gear measurement technology in the past century, it is mainly reflected in the following aspects:

(1) In terms of measurement principle, the development from "comparative measurement" to "engagement motion measurement" to "modeled measurement" is realized;

(2) In the technical means of realizing the measurement principle, it has undergone the evolution from "mechanical-based" to "electromechanical integration" until today's "light-machine-electricity" and information technology integration;

(3) In the expression and utilization of measurement results, it has gone through the leap of “instruction table plus visual reading” to “recording instrument record plus manual judgment” until “computer automatic analysis and feedback of measurement results to manufacturing system”. At the same time, the gear measuring instrument has gone through a single-parameter single-parameter instrument (a typical instrument has a single-disc involute inspection instrument), a single-variety multi-parameter instrument (a typical instrument has a tooth-toothed inspection instrument) The evolution of multi-parameter instruments (typical instruments with gear measurement centers).

In the past 50 years before the 1970s, various types of mechanical exhibition instruments of various types and specifications have been developed in the world to measure basic parameters such as tooth profile, spiral line and pitch. These instruments use a number of precision mechanisms to form a specified standard motion and then compare it to the measured one to obtain the magnitude of the measured error. A variety of mechanical involute development mechanisms have been developed in the world, such as single disc type, base round lever type, and relying mode. Among them, the disc lever type is the most widely used. The instruments belonging to this category are: Zeiss VG450, Carl Mahr 890 and 891S, MAAG SP60 and HP100, Osaka Seiki GC-4H and GC-6H, and 3201 of Harbin Measuring and Cutting Tool Factory. . For profile error measurement, mechanical spread measurement techniques are limited to involute tooth profile error measurements. It is difficult to measure the end face tooth thickness of a non-involute gear by the development method because the development mechanism is too complicated and lacks versatility. For the precise spiral forming mechanism, the principle of sinusoidal rule is mainly used, but how to accurately convert the linear motion of the sinusoidal scale into the rotary motion of the workpiece to be tested is different. The most typical applications, such as the UWM rolling measuring instrument produced by Fette, Germany, the universal rolling measuring instrument produced by Zeiss factory, the universal rolling measuring instrument designed by BHИИ of the former Soviet Union, the SU-130 type hob measuring instrument of Samputensili factory in Italy, the United States The universal hob measuring instrument produced by Michigan and the PWF250/300 from Klingelberg. Before the 1970s, mechanical display measurement technology has matured and has stood the test in production practice. Despite this, there are some shortcomings: the measurement accuracy still depends on the accuracy of the development mechanism, the mechanical structure is complex, the flexibility is poor, and multiple instruments are required to measure one gear. So far, instruments based on these technologies are still the common means of testing gears in some factories in China.

1970 was a turning point in gear measurement technology. The gear error measurement technology and the appearance of the gear measuring machine (center) solve a problem in the field of gear measurement, that is, to quickly acquire all the error information of the gear on one instrument. Although these two technologies are based on modern light, machine, electricity, computer and other technologies, they have embarked on different technical routes. The gear overall error measurement technique extracts individual errors and other useful information from the integrated measurements. After 30 years of improvement and promotion, the gear overall measurement method has developed into a motion geometry measurement method of traditional components in China. The basic idea is to mesh the measured object as a rigid functional component or transmission component with another standard component. Motion, by measuring the meshing motion error to reverse the measured error. The distinctive feature of the motion geometry measurement method is that it visually reflects the gear meshing transmission process and accurately reveals the variation law of the gear individual error and the relationship between the errors, especially suitable for gear process error analysis and dynamic performance prediction. The advantage of the instrument using this method is the high measurement efficiency and is suitable for part inspection in mass production. The typical instrument is the CZ450 gear overall error measuring instrument, CSZ500 bevel gear measuring machine and CQB700 cycloidal gear measuring instrument produced by Chengdu Tool Research Institute. The gear measurement center adopts the principle of coordinate measurement, which is actually a cylindrical (polar) coordinate measuring machine. The "coordinate measurement" is essentially "modeled measurement". For gears, the principle of modeled coordinate measurement is to measure the measured part as a pure geometry (relative to the "motion geometry"), by measuring the coordinates of the actual part (orthogonal coordinates, cylindrical coordinates, polar coordinates, etc.) It is compared with the mathematical model of the ideal shape to determine the error being measured. The coordinate measurement method is characterized by strong versatility, simple host structure and high measurement accuracy. The idea of ​​measuring gears by coordinate method has long been used, such as the combination of a universal tool microscope and an indexing head can also be used to measure gears. However, this static measurement method is not only inefficient, but the measurement accuracy is not guaranteed. The development of modern optoelectronic technology, microelectronics technology, computer technology, software engineering, precision machinery and other technologies has truly provided a solid technical foundation for the superiority of coordinate measurement. So far, the United States, Germany, Japan, Switzerland, China, Italy and other countries have produced CNC gear measuring centers. The typical products abroad are M&M's 3000 series and Klingelberg's P series; the typical domestic products are Chengdu Tool Research Institute. CGW300 horizontal measuring center and 3903 gear measuring center of Harbin Measuring and Cutting Tool Factory.
Although the gear measurement centers of various countries are similar in principle, there are certain gaps in the implementation methods. Mainly manifested in:

(1) In terms of measuring sensors, etc., although the angle measurement is generally performed using a high-precision circular grating, the measurement length varies depending on the object to be measured. Gears with high precision requirements or workpieces with long axial lengths, etc., generally use dual-frequency (or single-frequency) laser interferometer as the length reference (such as measuring involute or spiral sample); in other cases, High precision long grating.

(2) In terms of the accuracy of the mechanical system, high-precision bearings are necessary; and the accuracy of linear guides is guaranteed by mechanical precision, and is also achieved by error correction technology.

(3) In the aspect of numerical control system, NC open-loop control is often used in the 1970s; after the 1980s, all CNC control, mostly using DC servo motor or stepper motor. AC servo systems or linear motors have been used.

(4) In terms of the probe, there are inductive and grating types; one-dimensional, three-dimensional, and even rigid. The rigid probe is without a microsensor. If a rigid probe is used, the instrument is usually dedicated.

The gear measurement center is generally composed of a host computer, a CNC numerical control unit, a data acquisition unit, an inter-machine communication interface, a computer and peripherals, a measurement software, and a data processing software. The main features of today's latest CNC gear measurement center are: 1 performance is efficient, high precision, easy to operate. The measures taken include precision mechanical optimization design, 32-bit CNC4-5 axis CNC system, linear motor, 3D probe and error correction technology. 2 In terms of functions, including the main error items of gears (inside and outside), gear cutters (hobs, gear shaping cutters, shaving cutters), bevel gears, worm gears, worms, screws, convex gears, broaches, etc. Measurement; shape and position tolerance measurement of shaft parts; powerful analysis functions such as contact analysis, process error analysis, root shape analysis, parameter reverse seeking, etc.; can be coupled into the processing system for real-time data communication. 3 In terms of maintainability, it has fault self-diagnosis and network remote fault diagnosis capability. 4 upgradeability. Includes software upgradeable and hardware upgradeable.

Compared with mechanical display measuring instruments, the advantages of CNC gear measuring center are self-evident, and its qualitative leap is possible for tooth profile measurement of arbitrary shape, not limited to involute or linear teeth. Profile. The measurement of bevel gear, K worm (hob) and C worm (hob) is proof. The CNC Gear Measurement Center provides tools for measuring and controlling nonlinear spiral surfaces.

Since 1990, there have been several notable phenomena in the field of gear measurement technology worldwide: 1 The overall gear error measurement technology and gear coordinate measurement technology are combined into one. The Chengdu Tool Research Institute has introduced the CZN450 gear measuring machine with both standard worm and probe, while the foreign CNC gear measuring center can also give “virtual overall error”. 2 The combination of gear measurement center and coordinate measuring machine is one, such as Rdaiance of TSK Company of USA and ND430 of Process Equipement Company. 3 The combination of functional test and subtest test is one. Simplified measurement is one of the development trends of gear measuring instruments. The gear overall error measuring instrument is accepted by the gear manufacturing industry because it can give the gear full information efficiently.

Looking into the future, the relevant research and development focus of gear measuring instrument is: gear network measurement technology; virtual analysis technology of gear performance based on actual measurement results (intelligent pairing, dynamic performance prediction, etc.); gear overall error measurement technology (indicator quantification, performance optimization, etc.) Intelligent analysis technology of gear error; establishment of gear statistical error concept system and its corresponding measurement technology; rapid measurement and analysis technology of gears at production site (currently ITW model4823 is 450-600 pieces/hour; target: 1000 pieces/ Hours); the application of precision machinery, optoelectronic technology, microelectronics technology, software engineering and other technologies on gears.

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