What Are The Principles And Methods Of Error Compensation For Cnc Grinding Machines

[Aichele Jauregui]

In grinding process, the wear state of grinding wheel is a main factor affecting grinding quality. In the grinding process of the grinding wheel, the abrasive particles gradually blunt and lose the cutting ability. If you continue grinding, the friction between the grinding wheel and the workpiece will increase and heat up, and the grinding quality will decrease significantly. This is mainly due to the passivation of abrasive particles, the blockage of grinding wheel surface and the distortion of grinding wheel shape. Therefore, real-time detection of grinding wheel state and timely repair are of great significance to ensure grinding quality
transmission error and compensation technology:

transmission error mainly refers to the manufacturing accuracy and transmission clearance of the transmission chain. Using the error compensation method of CNC system software can significantly improve the overall accuracy of the machine tool without any improvement. Precision software error compensation technology has two meanings for improving the accuracy of NC machine tools. One is to combine with the progress of manufacturing accuracy to raise the overall accuracy of NC machine tools to a new level. The second is to implement software error compensation in the transformation of CNC CNC grinding machine, so as to realize the cheap upgrading of machine tool accuracy
1. Backlash error compensation principle

CNC grinding machine grinding is good! Backlash compensation is also known as reverse backlash compensation. When the mechanical transmission chain changes the direction of rotation (such as the moving direction of the worktable and the direction of rotation of the rotating shaft), due to the existence of backlash, the servo motor will idle, while the worktable has no actual movement, which is also known as loss of movement. In the semi closed-loop system, this backlash error has a great impact on the machining accuracy of the machine tool and must be compensated, CNC system is to add backlash compensation in the process of calculating the feedback position by in-situ control program to obtain the actual feedback position increment. The backlash value of each coordinate axis is measured in advance and input into the memory in the unit of servo resolution as the basic parameter of the machine tool. Whenever the change direction of the coordinate axis is detected, the backlash compensation value is automatically added to the feedback position detected by the feedback element to compensate for the loss of movement caused by the backlash
2. Equal pitch error compensation

the so-called equal pitch means that the spacing between compensation points is equal. For equal pitch error compensation, the reference point of the machine tool is selected as the basic point of compensation. The reference point of the machine tool 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 realizing software compensation, the feedback increment correction value of each compensation point must be measured (stored in the table in the unit of servo resolution). For high-precision CNC system, the actual position measured by laser interferometer is generally compared with the sent command position to obtain the feedback increment correction value of the corresponding compensation point. That is: compensation point feedback increment correction value = (NC command value - actual position value) /servo resolution
the pitch error compensation degree is generally included in the in place control program. When the control system calculates the coordinates of the current position of the workbench, the pitch error compensation program is called to realize the compensation of feedback increment and position. Due to the constant pitch error compensation, the number of compensation points and the spacing of compensation points of each coordinate axis are certain. By numbering the compensation points, it can be easily realized by software. However, such compensation lacks flexibility due to the dead position of the compensation point. In order to obtain the compensation that meets the actual needs of the machine tool, it is best to use the pitch error compensation method, that is, the pitch error compensation method with unequal spacing. After using reverse clearance compensation and equal pitch pitch error compensation, the accuracy of the machine tool is significantly improved, and the motion accuracy is increased from 140 μ M progress to 40 μ Within M
damage detection and repair of CNC grinding machine:

in the grinding process of CNC grinding machine, not only the size, shape and distribution of abrasive particles have an impact on the machining process, but also the air hole condition of the grinding wheel also plays an important role. When the air hole is seriously blocked, the service life of the grinding wheel will end prematurely. Grinding wheel clogging is a common phenomenon in grinding. No matter how reasonable the processing conditions are, it is impossible to completely prevent clogging. Grinding wheel blockage will aggravate wear plain milling operation and affect grinding quality. In order to avoid waste products in grinding, it is necessary to implement on-line detection technology for the grinding wheel in the grinding process. On line detection can eliminate quality problems in the early stage of manufacturing, so as not to cause waste products
contact grinding wheel wear detection method:

in grinding, the wear state of grinding wheel is one of the important indexes of grinding performance. CNC grinding machine affects the production efficiency and machining quality of grinding. In the grinding process of the grinding wheel, the abrasive particles gradually blunt and lose the cutting ability. If you continue grinding, the friction between the grinding wheel and the workpiece will increase and heat up, and the grinding quality will decrease significantly. This is mainly due to the passivation of abrasive particles, the blockage of grinding wheel surface and the distortion of grinding wheel shape. Using the detection of laser power spectrum, the dynamic monitoring of CCD and the application of rough set theory to establish an expert knowledge base for on-line monitoring is of great significance. However, due to the influence of wear debris and cutting fluid in grinding, the signal detection is easy to be distorted, and the input is large, so it is very difficult for practical application and maintenance
when detecting the grinding wheel, the grinding wheel first moves to a fixed point (which can be set as the second reference point). When the grinding wheel rotates, the sensor moves back and forth between points a and B along the track. The difference between the detected maximum and minimum signal values is the grinding wheel dressing amount. The processed signal value is input into the single chip microcomputer to control the grinding wheel dressing amount.