Gear in place measurement refers to the measurement when the instrument is installed on the gear or on the machine tool. According to the relevant regulations of ISO / TC60, the meaning of in-situ measurement includes two aspects: one is to measure the gear on the machine tool; the other is to measure the gear on the upper device, that is, to move the measuring device to the gear for measurement.
On board measurement system
When using in machine measurement system to measure the big gear, there is no need to lift and align the measured gear, which saves time, labor and high measurement efficiency. At the same time, the purchase of large gear measuring center is avoided, which can significantly reduce the input cost of equipment.
There are two types of on-line measurement: independent on-line measurement and integrated on-line measurement. The former is to add a set of measurement device beside the machine tool. The measurement of gear movement is still realized by the mechanical system of the machine tool. Before the 1990s, on-line measurement mainly used this form. At present, the technical transformation of some old machine tools is also in this form. Klingelnberg company of Germany has developed an independent in-house instrument evtm-d for measuring gear pitch and run out error. Its measuring gear module range is 1-40 mm, and the minimum outer diameter of workpiece is 20 mm. Theoretically, there is no requirement for the maximum outer diameter of workpiece. However, when measuring, the instrument needs to drive the measured gear to rotate continuously and slowly with the help of the rotating workbench of machining machine tool, Two measuring contacts are inserted into the tooth slot for measurement. The main problems of the independent on-line measurement are as follows: the positioning accuracy of the probe is low, and the measurement accuracy is not high; the measurement system is not integrated with the CNC system of the machine tool, and the test results must be converted to adjust the gear processing parameters.
The integrated on-board measurement uses the control system of the machine tool, some servo motion axes and additional measuring devices to complete the gear measurement. The new generation of large-scale CNC gear machine tools at home and abroad, such as gear hobbing machine, gear grinding machine and so on, are equipped with integrated measuring mechanism, which can realize the measurement of tooth profile, helix and pitch. These airborne gear measuring devices integrate the measuring system with the CNC system of the machine tool, and can feed back the measuring information to the machine tool after processing, so as to correct the processing parameters in time. China’s Qinchuan Machine Tool Group Co., Ltd. is equipped with a random measurement system on yk7380 grinding machines for workpiece adjustment and measurement. The zp08-zp60 series grinders produced by Kapp company in Germany are equipped with a probe system, which can measure the gears in the process on the spot. The rapid 2500 ~ rapid 6000 series gear grinding machines manufactured by H ö Fler company in Germany have integrated a three-dimensional probe system, which can measure the three-dimensional topological error of the tooth profile.
There is a problem in the measurement method of the big gear on the machine: when measuring the tooth profile deviation, because the maximum stroke of the tangential direction of the machine tool is relatively small, it is impossible to use the normal polar coordinate method developed from the base circle. Therefore, the rectangular coordinate is usually used to measure the tooth profile deviation. In addition, on-line measurement accuracy depends heavily on the original accuracy of the machine tool. There is a so-called “self-test” problem, that is, the measurement results can not reflect the influence of machine tool system error. Therefore, the measurement error correction of on-line measurement system is the key.
Upper measuring device
The top mounted measuring device was first developed and applied to the measurement of large gears in the 1950s. Because of its small volume, low cost and strong practicability, there is no upper limit requirement for the diameter of measured gear in theory, which is especially suitable for in-situ measurement of large gear. However, this kind of instrument is usually located on the tooth surface or tooth top. The measuring datum is not consistent with the design and manufacturing datum of the gear. The positioning precision depends heavily on the manufacturing precision of the gear, so it is difficult to improve the measuring precision. The typical product of this kind of instrument is the es-430 involute profile measuring instrument developed and produced by Maag company of Switzerland in 1970s. Due to the high positioning requirements and low measurement accuracy, the top mounted measuring instrument has stopped developing in the past 30 years.