Grinders are the preferred equipment for the finishing of metal products. In the grinding process, the wear state of the grinding wheel is a major factor affecting the quality of the grinding. During the grinding process, the abrasive grains gradually become blunt and affect the cutting performance. If the grinding is continued, the friction between the grinding wheel and the workpiece will increase and the heat will be generated, and the grinding quality will be significantly reduced. The main reason is that the abrasive grain is passivated, the surface of the grinding wheel is blocked, and the shape of the grinding wheel is distorted. Therefore, it is of great significance to detect the state of the grinding wheel in real time and to perform the dressing in time to ensure the quality of the grinding.
Second, transmission error and compensation technology Transmission error mainly refers to the manufacturing precision and transmission gap of the transmission chain.
Using the numerical control system software error compensation method, the overall accuracy can be significantly improved without any improvement in the mechanical part of the machine tool. Accuracy software error compensation technology has two meanings for improving the precision of CNC machine tools. Firstly, combined with the improvement of manufacturing precision, the overall accuracy of CNC machine tools is increased by one step. In the implementation of machine tool numerical control transformation, software error compensation is realized. Cheap machine tool accuracy upgrades.
Backlash compensation principle Backlash compensation is also called backlash compensation. When the mechanical transmission chain changes the steering direction, such as the worktable changes the moving direction, when the rotating shaft changes the steering, due to the existence of the backlash, the servo motor will be idling without the actual movement of the table, which is also called the lost motion. In a semi-closed loop system, this backlash error has a large influence on the machining accuracy of the machine and must be compensated.
The system adds backlash compensation during the calculation of the feedback position by the position control program to obtain the actual feedback position increment. The backlash value of each coordinate axis is measured and the basic parameters of the machine tool are input, and the memory is input in units of servo resolution. Whenever the coordinate axis change direction is detected, the backlash compensation value is automatically added to the feedback position detected by the feedback element to compensate for the loss due to the backlash. Equal-pitch pitch error compensation The so-called equal spacing means that the distance between the compensation points is equal.
Equal-pitch pitch error compensation selects the machine tool reference point as the base point of compensation. The machine tool reference point is selected by the corresponding reference pulse provided by the feedback system. It has high accuracy and is one of the basic parameters of the machine tool. Before implementing software compensation, the feedback incremental correction value of each compensation point must be measured and stored in the table in servo resolution. The higher precision system generally uses the laser interferometer to measure the actual position compared with the transmitted command position. The feedback incremental correction value of the corresponding compensation point is obtained.
Compensation point feedback incremental correction Numerical control command value A real sleepy value Servo resolution Pitch error compensation degree is generally included in the position control program. When the control system calculates the absolute coordinates of the current position of the workbench, the pitch error compensation program is called to realize the compensation of the feedback increment and the compensation of the position.
Since the equal-pitch pitch error compensates for the compensation points and the compensation point spacing of each coordinate axis is certain, by assigning the compensation points, it can be conveniently implemented in software. However, such compensation, because the position of the compensation point is too rigid and lacks flexibility, in order to obtain the compensation that meets the actual needs of the machine tool work, it is better to use the pitch error compensation method, that is, the pitch error compensation method with unequal spacing.
After the backlash compensation and the equally spaced pitch error compensation, the accuracy of the machine tool is obviously improved, and the motion accuracy can be improved from the forest to the forest.
Third, in the grinding wheel wear detection and dressing grinding process, not only the size, shape and distribution of the abrasive grains have an influence on the processing process, but also the pore condition of the grinding wheel plays an important role in the grinding quality.
When the air holes are severely blocked, the wear of the grinding wheel will be intensified, which will not only seriously affect the grinding quality, but also end the service life of the grinding wheel early. Regardless of how reasonable the processing conditions are, it is still a bottleneck in current technical treatment to completely prevent clogging. In order to reduce the scrap rate in the grinding process, it is necessary to carry out on-line inspection technology for the grinding wheel during the grinding process, so that the quality problem can be found and processed in the early stage of manufacturing.
Contact grinding wheel wear detection method In the grinding process, the wear state of the grinding wheel is one of the important indexes of the grinding wheel grinding performance, which affects the production efficiency and processing quality of the grinding process. During the grinding process, the abrasive grains gradually become blunt and lose the cutting ability. If the grinding is continued, the friction between the grinding wheel and the workpiece will increase and the heat will be significantly reduced.
This is mainly due to the passivation of the abrasive particles, the blockage of the surface of the grinding wheel and the distortion of the shape of the grinding wheel. Using the detection, dynamic monitoring of the laser power spectrum and applying the rough set theory to establish an online knowledge monitoring technology such as an expert knowledge base can solve the conventional detection problem. However, due to the influence of grinding debris, cutting fluid and other factors in the grinding process, the signal detection is easily distorted, and the investment is large, and the practical application and maintenance are very difficult.
Detection principle When the grinding wheel is detected as shown in the figure, the grinding wheel first moves to a certain fixed point and can be set as the second reference point. When the grinding wheel rotates, the sensor reciprocates along the track to the point, and the detected maximum and minimum signals. The difference between the values ​​is the dressing amount of the grinding wheel.
The processed signal value is entered into the single chip microcomputer to control the dressing amount of the grinding wheel. The jog feed and the rapid feed button, the jog back and the continuous pick-up sequence of the grinding wheel dressing the bearing grinding wheel contour are relatively simple and common methods. The grinding wheel has a simple trajectory and convenient control, so the diamond wheel dressing method is often used.
When the grinding wheel is trimmed, in addition to the rotation, the shaft is circularly interpolated and moved, and the dresser diamond wheel only performs the rotary motion. When the inspection side is over, the dressing wheel moves to the trimming position, and the maximum error is automatically stepped to the trimming position, and the grinding wheel reciprocates a plurality of times according to the predetermined trimming track to realize the dressing of the grinding wheel. Diamond wheel dressing grinding wheel indication, grinding wheel trimming specific measures In order to realize the automatic detection and dressing of the grinding wheel, the structural principle of the single-chip microcomputer is adopted in the transformation, and the retractable resistance sensor is used to realize the trimming amount control, and the stepping motor is controlled by the single-chip microcomputer to realize the trimming. Feed in quantity.
The function of the single-chip microcomputer is strong, the stroke switch is introduced, the keyboard can input the number of feed steps, and the digital tube displays the number of steps for inputting the feed. In order to extract the step function key, the input key is determined and the key is the graphic back-up key. Command port address port address port address port address. For the contact type measuring probe in-position switch, the measuring probe is retracted to the positional stroke switch, and the dressing wheel is fed to the positional stroke switch, and the dressing wheel is retracted to the positional stroke switch, which is the stop switch.
It is thought that the tool feeds the step electrode control, and the test probe DC electrode is reversed to rotate the tool grinding wheel.
During the dressing process of the grinding wheel, when the grinding wheel needs to be inspected, the grinding wheel is moved to the dressing position by calling the subroutine. The contact measuring probe is close to the grinding wheel. After the position is in place, the signal is sent, and the dressing wheel starts to approach the grinding wheel. After the position is in place, the signal is sent and the dressing wheel starts. Do a constant feed, the grinding wheel starts along the "grinding track of the grinding wheel"
After the national arc interpolation movement, after the dressing wheel moves and repairs the whole amount, the grinding wheel reciprocates once along the “grinding track of the grinding wheelâ€, ends the dressing, and the dressing wheel retreats. After the position is in place, the signal is sent and the trimming is finished and returned to the main program. The manual trimming process can be started by pressing the jog feed to the continuous feed arrival position.
According to the defect of the grinding wheel, determine the number of steps to feed, and shoot into the keyboard, the display can display the number of steps, press the confirm button to trim the grinding wheel and the grinding wheel to start. The feed stepper motor starts feeding until the given number of steps has been fed. You can jog back, exit trimming or jog feed, and further trim. Grinding is a minor finishing process, and the grinding wheel has a great influence on the machining accuracy. In the grinding, the grinding wheel wears faster. How to timely and accurately detect the wear degree of the grinding wheel and carry out the dressing is of great significance for improving the processing quality, and the numerical control transformation of the cost-saving grinding machine is a long way to go in the manufacturing industry.
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