Working principle and development of gear measuring instrument
Release time：2022-05-20Publisher:Jeenoce
In the field of mechanical engineering, it is often necessary to accurately measure the gear and other parts. The gear measuring instrument is an ideal tool for measuring the gear. It can realize the partial measurement of gear detection, and the whole process is completed on a machine. Next, let's talk about the working principle and development process of gear measuring instrument.
1、 Introduction of gear measuring instrument
Gear detector is mainly used to detect: gear transmission accuracy; Introduction to gear testing; Single measurement and comprehensive measurement of cylindrical gear; Gear overall error measurement; Gear pair measurement; Measurement of bevel gear, worm gear and rack; Gear, worm gear and worm mapping; Measurement of gear hob, worm gear hob and gear shaper cutter. It can realize the measurement of gear detection part on one instrument. It is an ideal tool for measuring gear.
It will include a variety of gear chain and worm measuring instruments, including gear chain and worm measuring instruments. There are many kinds of gears with complex geometry, and there are many parameters to characterize their errors. Therefore, there are many kinds of gear measuring instruments.
2、 Working principle of gear measuring instrument
The gear measuring instrument is generally composed of host, CNC numerical control unit, data acquisition unit, inter machine communication interface, computer and peripherals, measurement software and data processing software. The gear measuring machine adopts the principle of coordinate measurement. In fact, it is a cylindrical () coordinate measuring machine. The essence of "coordinate measurement" is "modeling measurement". For gears, the principle of modeling coordinate measurement is to take the measured part as a pure geometry, measure the coordinates of the actual part, including rectangular coordinates, cylindrical coordinates, coordinates, etc., and compare it with the mathematical model of the ideal shape, so as to reduce the measured error.
Measurement of gear parameters in length measurement technology. There are two methods to measure the errors of cylindrical gear and bevel gear: single measurement and comprehensive measurement. This paper mainly introduces the working principle of comprehensive measurement.
Comprehensive measurement is to measure the transmission accuracy of the gear by measuring the meshing transmission between the gear and the measured gear. Measuring gear is a kind of gear whose accuracy is more than two times higher than that of the measured gear. There are also measuring worm instead of measuring gear. There are two kinds of comprehensive measurement: double-sided meshing method and single-sided meshing method.
1. Double side meshing method: the measuring gear and the gear wheel to be measured are used for double-sided meshing rotation, and the large variation of the center distance in the rotation of the gear to be measured represents the radial comprehensive error of the gear to be measured. The gear measuring tool using this method is called gear double-sided meshing tester (see gear comprehensive tester).
2. Single side meshing method: the measured gear and the measured gear are meshed and rotated under the nominal center distance, and the tangential comprehensive error of the measured gear is expressed in the form of angular error. The gear measuring tools using this method include gear single-sided meshing tester and gear single-sided meshing overall error tester (see gear overall error measurement technology).
The comprehensive measurement can also be used to check the contact spots and noise of gear pairs. For bevel gears, comprehensive measurement is generally adopted, mainly to check the contact spots of the gear pair, but also to measure the radial comprehensive error, tangential comprehensive error and noise of the gear pair. The single measurement is generally to measure the accumulated error of the circumferential pitch and the radial runout of the ring gear. The measurement method is the same as that of the cylindrical gear, but the axis of the measuring head should be kept perpendicular to the conical prime line. In the late 1970s, people began to use CMM to measure the tooth profile of bevel gear, and draw the contour of the measured tooth surface with a plotter.
The main points of today's new CNC gear measurement center are as follows. The performance is high, high precision and easy to operate. The measures taken include the optimal design of precision machinery, 32-bit CNC 4-5 axis CNC system, linear motor, three-dimensional probe and error correction technology; In terms of function, it includes the measurement of main error items of rotating parts such as gear (inner and outer), gear cutter (hob, gear shaper and shaving cutter), bevel gear, worm gear, worm, screw, convex gear and broach; Geometric tolerance measurement of shaft parts; Powerful analysis functions, such as contact analysis, process error analysis, tooth root shape analysis, parameter reverse calculation, etc; It can be coupled to the processing system for real-time data communication; In terms of maintainability, it has the ability of fault self diagnosis and network remote fault diagnosis; It is scalable, including software and hardware.
Compared with mechanical generative measuring instruments, the advantages of CNC gear measuring center are self-evident. Its qualitative leap provides the possibility for the measurement of arbitrary tooth profile, not limited to involute or linear tooth profile. The measurement of bevel gear, K worm (HOB) and C worm (HOB) is proof. CNC gear measuring center provides a tool for measuring and controlling nonlinear helical surface.
3、 Development of gear measuring instrument
The development of gear measurement technology is mainly reflected in the following aspects. In terms of measurement principle, it has realized the development from "comparative measurement" to "meshing motion measurement" to "modeling measurement"; In terms of the technical means to realize the measurement principle, it has experienced the evolution from "focusing on machinery" to "electromechanical combination" to today's comprehensive integration of "light machine electricity" and information technology; In terms of the expression and utilization of measurement results, it has experienced a leap from "indicator plus visual reading" to "recording instrument recording plus manual research and judgment" to "computer automatically analyzes and feeds back the measurement results to the manufacturing system". At the same time, the gear measuring instrument has experienced the evolution from single variety and single parameter instrument (typical instrument has single disc involute tester), single variety and multi parameter instrument (typical instrument has tooth profile and tooth direction tester) to multi variety and multi parameter instrument (typical instrument has gear measuring center).
Although the gear measuring centers are similar in principle, there is a certain gap in the implementation mode. Mainly in the following aspects.
1. In terms of measuring sensors, although high-precision circular gratings are generally used for angle measurement, the length measurement is different due to different measured objects. For gears with high accuracy requirements or workpieces with long axial size, dual frequency (or single frequency) laser interferometer is generally used as the length reference (such as measuring involute or helix template, etc.); In other cases, high-precision long grating is used.
2. In terms of the accuracy of mechanical system, high-precision bearing is necessary; The accuracy of linear guide rail depends on mechanical accuracy and error correction technology.
3. In terms of numerical control system, it was often NC open-loop control in the 1970s; After the 1980s, it was controlled by CNC, mostly using DC servo motor or stepping motor. At present, there have been many using AC servo system or linear motor.
4. In terms of probe, there are inductance type and grating type; There are dimensional, three-dimensional and even rigid. Rigid probe is without micrometer sensor. If a rigid probe is used, the instrument is usually used.
