How to improve the efficiency of CNC machining
How to improve the efficiency of CNC machining
1、 Programming skills
CNC programming is the most basic work of CNC machining. The quality of workpiece processing program directly affects the final machining accuracy and efficiency of machine tools. We can use the inherent program skillfully, reduce the accumulated error of the numerical control system, and flexibly use the main program and subprogram.
1. Flexible use of main program and subprogram
In complex workpiece processing the first mock exam is usually used in the form of multiple parts. If there are several identical shapes on the workpiece, the relationship between the main program and the subprogram should be used flexibly, and the subprogram should be called repeatedly in the main program until the machining is completed. It can not only ensure the consistency of machining size, but also improve the machining efficiency.
2. Reducing cumulative error of CNC system
Generally, the incremental mode is used to program the workpiece, which is based on the previous point. In this way, the continuous execution of multi-stage programs will inevitably produce a certain cumulative error. Therefore, in programming, absolute mode should be used as far as possible, so that each program segment is based on the origin of the workpiece, which can reduce the cumulative error of the CNC system and ensure the machining accuracy.
Machining accuracy is mainly used to produce products. Both machining accuracy and machining error are terms for evaluating geometric parameters of machined surfaces. However, the actual parameters obtained by any processing method will not be absolutely accurate. From the function of parts, as long as the machining error is within the tolerance range required by the part drawing, the machining accuracy is considered to be guaranteed.
Machining accuracy refers to the degree to which the actual geometric parameters (size, shape and position) of a part conform to the ideal geometric parameters. The difference between them is called machining error. The size of machining error reflects the level of machining accuracy. The larger the error is, the lower the machining accuracy is, and the smaller the error is, the higher the machining accuracy is. The following is a brief introduction to the methods to improve the machining accuracy of workpieces:
1、 Adjust the process system
(1) Trial cutting method adjustment by trial cutting - measuring the size - adjusting the cutting rate of the tool - cutting - re cutting, and so on until the required size is reached. The production efficiency of this method is low, and it is mainly used for single piece and small batch production.
(2) The adjustment method obtains the required size by adjusting the relative position of the machine tool, fixture, workpiece and tool in advance. This method has high productivity and is mainly used for mass production.
2、 Reduce machine error
(1) The rotary accuracy of bearing should be improved: ① select high-precision rolling bearing; ② adopt high-precision multi oil wedge dynamic pressure bearing; ③ adopt high-precision hydrostatic bearing
(2) To improve the accuracy of accessories with bearings: ① improve the machining accuracy of box support hole and spindle journal; ② improve the machining accuracy of mating surface with bearing; ③ measure and adjust the radial runout range of corresponding parts to make error compensation or offset. (3) Proper preloading for rolling bearing: ① clearance can be eliminated; ② bearing stiffness can be increased; ③ rolling element error can be homogenized.
(4) The spindle rotation accuracy is not reflected on the workpiece
3、 Reduce transmission error of drive chain
(1) Less transmission parts, short transmission chain and high transmission precision;
(2) The lower speed transmission is an important principle to ensure the transmission accuracy, and the closer the transmission pair is to the end, the smaller the transmission ratio should be;
(3) The precision of the end part should be higher than that of other transmission parts.
4、 Reduce tool wear
(1) The tool must be reground before the tool size wear reaches the sharp wear stage
(2) Select special cutting oil for full lubrication
(3) The material of cutting tools shall meet the technological requirements
5、 Reduce the mechanical deformation of process system
(1) Improve the stiffness of the system, especially the stiffness of the weak link in the process system;
(2) Load reduction and its variation
6、 Reduce thermal deformation of process system
(1) Reduce heat source and isolate heat source
(2) Equilibrium temperature field
(3) Adopt reasonable machine tool component structure and assembly benchmark
(4) Accelerate heat transfer equilibrium
(5) Control ambient temperature
7、 Reducing residual stress
(1) Increase heat treatment process to eliminate internal stress;
(2) Arrange the process reasonably.
The above is the method to reduce the error of the workpiece, reasonable arrangement of the process can effectively improve the accuracy of the workpiece.
1、 Programming skills
CNC programming is the most basic work of CNC machining. The quality of workpiece processing program directly affects the final machining accuracy and efficiency of machine tools. We can use the inherent program skillfully, reduce the accumulated error of the numerical control system, and flexibly use the main program and subprogram.
1. Flexible use of main program and subprogram
In complex workpiece processing the first mock exam is usually used in the form of multiple parts. If there are several identical shapes on the workpiece, the relationship between the main program and the subprogram should be used flexibly, and the subprogram should be called repeatedly in the main program until the machining is completed. It can not only ensure the consistency of machining size, but also improve the machining efficiency.
2. Reducing cumulative error of CNC system
Generally, the incremental mode is used to program the workpiece, which is based on the previous point. In this way, the continuous execution of multi-stage programs will inevitably produce a certain cumulative error. Therefore, in programming, absolute mode should be used as far as possible, so that each program segment is based on the origin of the workpiece, which can reduce the cumulative error of the CNC system and ensure the machining accuracy.
Machining accuracy is mainly used to produce products. Both machining accuracy and machining error are terms for evaluating geometric parameters of machined surfaces. However, the actual parameters obtained by any processing method will not be absolutely accurate. From the function of parts, as long as the machining error is within the tolerance range required by the part drawing, the machining accuracy is considered to be guaranteed.
Machining accuracy refers to the degree to which the actual geometric parameters (size, shape and position) of a part conform to the ideal geometric parameters. The difference between them is called machining error. The size of machining error reflects the level of machining accuracy. The larger the error is, the lower the machining accuracy is, and the smaller the error is, the higher the machining accuracy is. The following is a brief introduction to the methods to improve the machining accuracy of workpieces:
1、 Adjust the process system
(1) Trial cutting method adjustment by trial cutting - measuring the size - adjusting the cutting rate of the tool - cutting - re cutting, and so on until the required size is reached. The production efficiency of this method is low, and it is mainly used for single piece and small batch production.
(2) The adjustment method obtains the required size by adjusting the relative position of the machine tool, fixture, workpiece and tool in advance. This method has high productivity and is mainly used for mass production.
2、 Reduce machine error
(1) The rotary accuracy of bearing should be improved: ① select high-precision rolling bearing; ② adopt high-precision multi oil wedge dynamic pressure bearing; ③ adopt high-precision hydrostatic bearing
(2) To improve the accuracy of accessories with bearings: ① improve the machining accuracy of box support hole and spindle journal; ② improve the machining accuracy of mating surface with bearing; ③ measure and adjust the radial runout range of corresponding parts to make error compensation or offset. (3) Proper preloading for rolling bearing: ① clearance can be eliminated; ② bearing stiffness can be increased; ③ rolling element error can be homogenized.
(4) The spindle rotation accuracy is not reflected on the workpiece
3、 Reduce transmission error of drive chain
(1) Less transmission parts, short transmission chain and high transmission precision;
(2) The lower speed transmission is an important principle to ensure the transmission accuracy, and the closer the transmission pair is to the end, the smaller the transmission ratio should be;
(3) The precision of the end part should be higher than that of other transmission parts.
4、 Reduce tool wear
(1) The tool must be reground before the tool size wear reaches the sharp wear stage
(2) Select special cutting oil for full lubrication
(3) The material of cutting tools shall meet the technological requirements
5、 Reduce the mechanical deformation of process system
(1) Improve the stiffness of the system, especially the stiffness of the weak link in the process system;
(2) Load reduction and its variation
6、 Reduce thermal deformation of process system
(1) Reduce heat source and isolate heat source
(2) Equilibrium temperature field
(3) Adopt reasonable machine tool component structure and assembly benchmark
(4) Accelerate heat transfer equilibrium
(5) Control ambient temperature
7、 Reducing residual stress
(1) Increase heat treatment process to eliminate internal stress;
(2) Arrange the process reasonably.
The above is the method to reduce the error of the workpiece, reasonable arrangement of the process can effectively improve the accuracy of the workpiece.
