Active measurement in the hottest grinding process

Active measurement in grinding

active measurement refers to that in the process of machining, the measuring device always measures the size of the workpiece, and transmits its size change to the controller at any time, and then the controller sends signals (such as rough grinding, fine grinding, smooth grinding, to size, etc.) to control the action of the machine tool. Because it enables the operator to measure the workpiece without stopping the machine, the labor intensity is reduced, the production efficiency is improved, and the scrap rate is reduced. At the same time, the size consistency of the processed workpiece is high. It is especially suitable for use in mass assembly line operations, such as the processing of auto parts and bearing parts

1. Basic composition of active measuring instrument

active measuring instrument is mainly composed of measuring device, driving device and controller

(1) measuring device

in the process of grinding the workpiece with the grinding wheel, the two diamond detectors of the device always contact the surface of the workpiece, and the change of the workpiece diameter is passed through the detector and lever, so that the position of the magnetic core and the inductive coil in the device generates a relative displacement, so as to convert the change of the size into the change of the inductance. At the meeting, the master jointly reviewed the consolidated accounts of the third quarter of this year. The dynamic measuring device, commonly known as the probe, plays the role of converting the changes of the measured parameters into measurement signals. It is the main body of the measuring instrument. From the structural principle, it can be divided into single point measuring device and double point measuring device. The single point measuring device can be used for end face positioning or two combined to measure large diameter, etc; The double point measuring device can measure the outer diameter, inner diameter, groove width, step width, etc

(2) controller

the controller rectifies and amplifies the inductance signal output by the device through phase sensitivity, and sends signals such as rough grinding, fine grinding, smooth grinding and to size to the grinder control system. After receiving the signal, the grinder control system controls the feeding mechanism of the machine tool, so as to achieve the purpose of controlling the size of the workpiece

the controller is an important part of the active measuring instrument. The current controller has basically eliminated the circuit of separating components in the past and adopted integrated circuits. Some have used microprocessors, which greatly improves the repetition accuracy, long-term stability and other performance

(3) the advance and retreat of the oil pressure driving device

measuring device is driven by the oil pressure driving device. After the workpiece is installed, the grinding wheel advances rapidly, and the driving oil cylinder also drives the active measuring device into the measuring station. After grinding to the size, the grinding wheel quickly returns, and the driving oil cylinder drives the active measuring device to exit the measuring station, so as to facilitate the operator to load and unload the workpiece

the oil pressure driving device is the connecting part between the active measuring device and the machine tool, which is responsible for entering or exiting the device into the measuring station. Through the adjustment of the front and rear fine-tuning mechanism, the contact of the device can be aligned with the center of the workpiece. At present, there are vertical and horizontal oil cylinders (determined according to the center height of the machine tool). The active measurement control system composed of the above three parts is combined with the machine tool control system to form the active measurement in the grinding process. Taking the grinding process controlled by three signals as an example, from the rapid feed of the grinding wheel to the rough grinding stage, point P1 is the signal point for switching from the rough grinding feed to the fine grinding feed, point P2 is the signal point for switching from the fine grinding feed to the non sparking grinding feed, and point P3 is the signal point for returning the tool to the dimension. The machine tool control system successively receives these three signals from the controller and performs different actions to complete a grinding cycle. For high-precision grinding, the size dispersion of machined parts can generally be controlled within 2 ~ 3 μ ｍ。 In recent years, the process requires not only the improvement of dimensional accuracy, but also the improvement of shape accuracy. Therefore, the control signal points required by the machine tool are increased from 3 to 4, and even to 5 ~ 6 points

2. measurement and control of active measuring instrument

(1) control of workpiece taper

in the grinding of auto parts, especially the workpiece with multiple shaft diameters such as camshaft and crankshaft, it is required that the shaft diameter size is consistent and cannot produce a large taper. For such a workpiece, two outer diameter measuring devices are generally used to measure the shaft diameters at both ends. Considering the different processing speeds at both ends, The size and taper can be controlled by controlling the grinding cycle. The outer diameter measuring device controls the size of both ends of the workpiece through the controller, and outputs the measured taper value signal to the machine tool control system to control the action of the grinding wheel and complete the control of the workpiece taper

(2) measurement of workpiece ellipse

at present, there are two kinds of active measuring instruments used to measure the ovality of shaft parts. The more common one is to directly measure the diameter of the workpiece by using the two-point measuring device, and calculate the diameter difference through electrical calculus as the evaluation value of ovality; The other is the newly launched single point measurement method to detect the roundness of the workpiece in the processing process (the same principle as the radius measurement method of the roundness instrument). After the measured data is processed accordingly, the roundness value of the workpiece is directly read out

① active measuring instrument commonly used to measure ovality

double point measuring device: two differential transformer sensors are built in, which can actively measure shaft parts. The controller first controls the size of the shaft diameter. When the outer diameter of the workpiece is grinded close to the specified value, the controller starts to measure the ovality of the workpiece, and uses the peak holding circuit to process the maximum and minimum values of the measured outer diameter through data processing, and directly output the size of the ovality; If the ovality is out of tolerance, a signal will be sent, and the machine tool will control the trimming of ovality

② new active measuring instrument for roundness measurement

pulcom V10 series control instrument produced by Tokyo precision in Japan is used together with the two-point measurement device to create more value for users. It can measure the roundness of the workpiece directly with the lower contact of the device while measuring the diameter of the workpiece, using the same measuring principle as the radius method of the roundness instrument. The signal reflection speed of the meter is 1ms, and the workpiece speed is within the range of 17 ~ 999rpm. After one rotation, 60 ~ 3600 data can be measured, and the roundness value and peak number of the workpiece can be displayed visually through the screen. This controller can also choose to measure the roundness value before or after the workpiece is processed to the size. Compared with the traditional roundness meter, it has the following advantages: the roundness value of the workpiece can be reflected on the processing site, which reduces the workload of measurement, and the high and low temperature experimental machine has a great degree of lifting chamber detection in this function; It can timely monitor some emergencies that affect the quality of the workpiece, such as the poor quality of the workpiece center hole, the poor quality of the blank, the residual hard skin when machining to the size, and the large deformation of the workpiece caused by the failure of the grinding wheel feeding system; It can directly reflect the running condition of the machine tool, so as to shorten the adjustment time of the equipment and improve the work efficiency

3. Application of active quantity meter

with the rapid development of electronic technology and the application of new technology marked by microcomputer, the performance and function of active quantity meter have made great progress. Modern active quantity meter has overcome the limitation of only controlling a single size and a single process in the past, and the requirements for product detection are more and more strict and comprehensive, and its application in production lines is also more and more extensive. It also puts forward higher standards for the function, accuracy, stability and other aspects of the measuring instrument, which meets people's increasing requirements for product quality

(1) measurement before machining

the inner diameter measuring device 4 enters the measuring station through the drive cylinder 8 to measure the inner diameter of workpiece 2. Before grinding the grinding wheel, the gauge has measured the inner diameter of the blank. If the size of the blank is too large or too small, the controller will send a signal to the machine tool to stop the feeding of the grinding wheel, so as to avoid accidents

(2) measurement in machining

this is a common active measurement and control process of grinding. This process is mainly to control the size of the workpiece. When the grinding wheel grinds the workpiece, with the increase of the workpiece size, the controller sends signals to the machine tool such as rough grinding, fine grinding, smooth grinding and to size according to the preset signal points, and the grinding wheel exits to complete the grinding process of the workpiece. In this example, the dispersion of most workpiece sizes in a day is 3 ~ 5 μ m。

(3) measurement after processing

the processed workpiece enters and can also be used as the post machine measurement station for material contraction, zigzag and other experiments. The inner diameter of the workpiece is measured by the pneumatic probe, and the zero position is automatically calibrated regularly by the standard calibration gauge. The signal is output to the controller through the a/e pneumatic electric converter. The controller will be divided into five groups (+ng, +ok, -ok, -ng) according to the size of the workpiece, At the same time, judge the trend of size change, and send a supplementary adjustment signal to the controller 6 in processing according to the trend of size change, so as to change its zero position and control the development of the processing process in a good direction. In this way, the machine tool can continue to work stably without being operated for a long time