Analysis of influencing factors and improvement methods for machining accuracy of CNC lathes
Jan 16, 2024
At present, in contemporary mechanical industry production, CNC lathe technology has gained recognition from a large number of users due to its outstanding performance. At the same time, the demands of users are increasing, and the requirements for machining accuracy of workpieces are also increasing. Especially in recent years, the rise of technology has driven the large-scale industrial production of high-precision instrument manufacturing technology, and has also led to a large number of CNC lathe machining errors. The emergence of these problems poses greater challenges to the application of CNC lathe technology.
The inevitable problem in mechanical production is error, and the effective resolution (or reduction) of error is one of the key technical tasks in CNC machining. Because many factors in the CNC machining process can cause errors, directly affecting the accuracy and quality of the machined parts. Therefore, it is necessary to effectively analyze the influencing factors based on the actual requirements of mechanical processing, and take certain measures to control errors, in order to improve the machining accuracy of CNC lathe workpieces.
1. Introduction to the Concept of CNC Lathe
1.1 Common classifications and structures of CNC lathes
The rise of market economy has driven the widespread application of CNC lathe processing technology, which can be divided into three categories according to different control principles: ① ordinary CNC lathe processing; ② Point control CNC lathe machining; ③ Other CNC lathe processing.
In specific mechanical processing applications, CNC machining technology is generally used for complex and high-quality forming designs, which can meet the processing requirements of users for high standard workpieces. A typical CNC lathe consists of the following parts:
① The lathe control system, also known as the configuration machining machine, is mainly used to control the lathe;
② The lathe servo drive system mainly completes the driving work, and the CNC machine tool completes the driving operation of workpiece production through worker control;
③ Auxiliary machining system, providing mathematical calculations, drawing and other auxiliary functions for CNC machining support;
④ The CNC programming system for lathes is a software application system or code used to control lathes. The application of this system can facilitate the automated processing of workpieces.
1.2 Performance indicators and characteristics
The inherent characteristics of CNC lathes make them more suitable for processing complex workpieces and certain special spare parts. Its unique performance indicators can enable automatic (semi-automatic) processing of workpieces, effectively improving machining efficiency. Meanwhile, due to the application of automation technology, the internal system structure of CNC lathes becomes more complex. Once problems arise, the difficulty of maintenance and repair is relatively high, requiring professional personnel to carry out relevant operations.
The control of a CNC lathe is achieved through CNC programming, and the programming system can set specific machining steps for the lathe, which is one of the key features of a CNC lathe.
CNC programming technology uses servo system (mostly machine language) language devices to drive workpieces. Workers operate and process according to the prompts of the lathe system, freeing them from heavy manual labor, greatly improving processing efficiency and quality, and simplifying the work content and intensity of workers.
However, while CNC lathes can improve the machining accuracy of workpieces, the requirements for investment costs have also increased significantly. The higher the precision coefficient and quality requirements of the workpiece, the more complex the CNC lathe application system used in its machining process, and the stronger the professional requirements for technicians and operators. Simply put, the quality of the workpiece is directly proportional to the cost of CNC machining.
2. Factors affecting the accuracy of CNC lathes
The increase in people's living needs has led to a higher demand for workpieces or handicrafts in the mechanical industry. In the development process of various industries, the use and updating of components are indispensable. In practical applications, CNC lathes use numbers and text to control the precision machining of components. While effectively reducing the negative impact of errors and errors in manual manufacturing, they can reduce error coefficients and increase the machining accuracy of products. The specific operating steps of a CNC lathe are shown in Figure 1.
The inevitable problem in mechanical production is error, and the effective resolution (or reduction) of error is one of the key technical tasks in CNC machining. Because many factors in the CNC machining process can cause errors, directly affecting the accuracy and quality of the machined parts. Therefore, it is necessary to effectively analyze the influencing factors based on the actual requirements of mechanical processing, and take certain measures to control errors, in order to improve the machining accuracy of CNC lathe workpieces.
1. Introduction to the Concept of CNC Lathe
1.1 Common classifications and structures of CNC lathes
The rise of market economy has driven the widespread application of CNC lathe processing technology, which can be divided into three categories according to different control principles: ① ordinary CNC lathe processing; ② Point control CNC lathe machining; ③ Other CNC lathe processing.
In specific mechanical processing applications, CNC machining technology is generally used for complex and high-quality forming designs, which can meet the processing requirements of users for high standard workpieces. A typical CNC lathe consists of the following parts:
① The lathe control system, also known as the configuration machining machine, is mainly used to control the lathe;
② The lathe servo drive system mainly completes the driving work, and the CNC machine tool completes the driving operation of workpiece production through worker control;
③ Auxiliary machining system, providing mathematical calculations, drawing and other auxiliary functions for CNC machining support;
④ The CNC programming system for lathes is a software application system or code used to control lathes. The application of this system can facilitate the automated processing of workpieces.
1.2 Performance indicators and characteristics
The inherent characteristics of CNC lathes make them more suitable for processing complex workpieces and certain special spare parts. Its unique performance indicators can enable automatic (semi-automatic) processing of workpieces, effectively improving machining efficiency. Meanwhile, due to the application of automation technology, the internal system structure of CNC lathes becomes more complex. Once problems arise, the difficulty of maintenance and repair is relatively high, requiring professional personnel to carry out relevant operations.
The control of a CNC lathe is achieved through CNC programming, and the programming system can set specific machining steps for the lathe, which is one of the key features of a CNC lathe.
CNC programming technology uses servo system (mostly machine language) language devices to drive workpieces. Workers operate and process according to the prompts of the lathe system, freeing them from heavy manual labor, greatly improving processing efficiency and quality, and simplifying the work content and intensity of workers.
However, while CNC lathes can improve the machining accuracy of workpieces, the requirements for investment costs have also increased significantly. The higher the precision coefficient and quality requirements of the workpiece, the more complex the CNC lathe application system used in its machining process, and the stronger the professional requirements for technicians and operators. Simply put, the quality of the workpiece is directly proportional to the cost of CNC machining.
2. Factors affecting the accuracy of CNC lathes
The increase in people's living needs has led to a higher demand for workpieces or handicrafts in the mechanical industry. In the development process of various industries, the use and updating of components are indispensable. In practical applications, CNC lathes use numbers and text to control the precision machining of components. While effectively reducing the negative impact of errors and errors in manual manufacturing, they can reduce error coefficients and increase the machining accuracy of products. The specific operating steps of a CNC lathe are shown in Figure 1.
Figure 1 Operating Steps of CNC Lathe
However, for the (semi automated) automated processing of a certain type of single small batch workpiece, due to its complex shape and high precision coefficient requirements, the processing effect is not ideal, and there is still a lot of room for improvement in accuracy and technology. The main factors that affect the machining accuracy of CNC lathes are as follows:
2.1 The influence of servo factors
The servo system is mainly responsible for the stable operation of the CNC lathe in the machining operation of the CNC lathe. Under the operation of this system, the CNC lathe provides mechanical power and plays a coordinated control function. During the operation process, if there is a speed error when the operator drives the system, it will cause transmission errors and a series of other problems, leading to errors in machining accuracy and affecting the final quality of the workpiece.
2.2 The impact of guide rail errors
Many tasks of CNC lathes are carried out on guide rails, so it is necessary to accurately confirm the optimal position of each component during the process of placing tools into the guide rails. If guide rail wear is found during lathe machining, or if the operator controls the rail incorrectly, it can cause guide rail errors and have a negative impact on the quality of the workpiece.
2.3 Impact of Tool Parameters
CNC lathes cannot process any component without turning tools, but many random problems arise when cutting with turning tools. For example:
① The problem of the main deviation angle of the turning tool, when the position of the main deviation angle is offset or the main deviation angle is small, will directly affect the accuracy coefficient of the processed workpiece The problem of external cutting of the tool tip, when performing external turning on the workpiece, has higher requirements for the tool; Once there is a slight deviation in the arc turning tool, it will directly affect the machining accuracy coefficient of the workpiece. Write a reasonable turning program and carefully analyze the deviation of the tool axis to correct the position of the tool. The cutting edge of the CNC lathe tool has a circular radius, and there is also a problem of the main deviation angle and the height difference between the workpiece, which can also have a certain impact on the machining accuracy of the CNC lathe. Based on this, it is necessary to comprehensively refer to the relevant parameters of the tool during the machining process of the workpiece, take into account the error problem during programming, and reduce the occurrence of potential errors from parameter factors
.
2.4 Impact of approximation error and rounding error
The so-called approximation error refers to the use of mathematical approximation algorithms in mechanical control programming to approximate the basic error of the part through precise value control. Once the precise value is too low, it will affect the accuracy of the workpiece. The so-called rounding error refers to the effective control of the linear displacement of the machined parts in the economic stepper motor CNC lathe machining through stepper pulses. The pulse equivalent is the smallest unit of product specifications, which directly affects the machining accuracy of the CNC lathe workpiece.
When the workpiece of the CNC lathe is in working condition, when the operation reaches the equivalent value of rounding pulse, rounding errors cannot be avoided. This error directly affects the size and specifications of the processed components.
3. Exploration of coping strategies
There are many factors that affect the machining accuracy of CNC lathes, but in the machining process of CNC lathes, they cannot be influenced by these factors and should be tolerated. It is necessary to find corresponding coping strategies and deal with possible factors in order to more effectively reduce error values and improve the accuracy of workpiece production.
3.1 Control of servo deviation
For CNC lathes, the role of servo systems is the most important. If you want to reduce the error of machining workpieces on the lathe and reduce the negative impact of the lathe itself, then it is necessary to attach great importance to the practical application of servo systems. Pairing high-performance and low-power driving devices with servo systems can effectively optimize the parameters of the lathe system. Meanwhile, in the turning process, suppressing speed errors based on the physical characteristics of straight workpieces can reduce a series of problems caused by speed lag; Set the open-loop gain function for arc machining to improve the contour machining accuracy of arc workpieces.
3.2 Performance control of CNC lathes
The rapid development of mechanical technology has had a significant impact on CNC lathes, and in recent years, the machining quality and efficiency of CNC lathes have been significantly improved. Meanwhile, the performance issues of CNC lathes have also received increasing attention from professionals. How to effectively improve the performance of CNC lathes has become one of the daily discussions among experts. Generally speaking, in order to improve the self performance of the lathe, an inclined bed shape can be adopted to effectively improve its bending and torsion resistance.
The use of high standardization coefficient turning tools for cutting, and equipped with automatic tool changing function for the lathe, can effectively optimize the turning effect and improve the turning accuracy level of components. Taking the specific machining of a certain axis type part on a CNC lathe as an example, a 1mm tool compensation control is reserved before rough machining of the part. Then, two rounds of lathe turning processing are adopted. The first round of radial feed rate is set to 0.5mm, and a fine machining is carried out. After the first round of fine machining is completed, there is still 0.5mm of tool compensation. At this time, a second round of deep machining can be carried out, effectively improving the accuracy of the product.
Through practical operation, it has been shown that the precision error of shaft workpieces can be effectively controlled through three rounds of machining, from rough machining to primary fine machining and secondary fine machining.
3.3 Error compensation control
When conducting CNC machining, considering the impact of approximation error on product error rate, the control system is upgraded by using mathematical calculation formulas and principles to outline the workpiece profile, improve accuracy coefficient, reduce approximation error, and ensure that the quality and accuracy coefficient of the workpiece are improved during irregular machining processing. The control of rounding errors can be prevented in the early stage through hardware processing, or the accuracy value of errors can be compensated through software processing to eliminate the influence of uncertain factors in actual operations as much as possible.
For workpieces or processes that require repeated positioning, effective measurement error calculation should be carried out before CNC machining to minimize measurement errors and provide more accurate calculation for deep precision machining. This facilitates the control of workpiece error accuracy range in the later stage, effectively improving component production efficiency and accuracy
.
3.4 Maintenance and Repair of Lathe
CNC lathes have extremely high requirements for machining accuracy, so real-time monitoring of the lathe is necessary during the working process. Once a fault prompt appears, it must be dealt with immediately, and the safety factor of processing related work data must be adjusted and optimized. Based on the feedback error information, fixed-point control and management of the control end should be carried out. When repairing the accuracy of the guide rail, use environmentally friendly guide rail coatings to improve the durability of the lathe guide rail and reduce errors caused by physical factors of the guide rail.
At the same time, during the maintenance process of the system, the measurement and machining positioning accuracy of the lathe can be improved, and the series of impacts of cutting accuracy on workpiece quality can be reduced.
4. Conclusion
There are various reasons that affect the machining accuracy of CNC lathes during workpiece processing, and the resulting error effects vary due to their varying degrees of influence. Therefore, operators must analyze the specific reasons and use CNC lathes as the basis to improve the machining quality of workpieces through servo deviation control, performance control, and error compensation control. At the same time, they must regularly repair and maintain the lathes to eliminate the impact of potential problem crises, improve the overall performance and accuracy ratio of CNC lathes, and effectively ensure the machining accuracy and quality of mechanical workpieces, Promote the further improvement of China's CNC lathe technology development level.
2.1 The influence of servo factors
The servo system is mainly responsible for the stable operation of the CNC lathe in the machining operation of the CNC lathe. Under the operation of this system, the CNC lathe provides mechanical power and plays a coordinated control function. During the operation process, if there is a speed error when the operator drives the system, it will cause transmission errors and a series of other problems, leading to errors in machining accuracy and affecting the final quality of the workpiece.
2.2 The impact of guide rail errors
Many tasks of CNC lathes are carried out on guide rails, so it is necessary to accurately confirm the optimal position of each component during the process of placing tools into the guide rails. If guide rail wear is found during lathe machining, or if the operator controls the rail incorrectly, it can cause guide rail errors and have a negative impact on the quality of the workpiece.
2.3 Impact of Tool Parameters
CNC lathes cannot process any component without turning tools, but many random problems arise when cutting with turning tools. For example:
① The problem of the main deviation angle of the turning tool, when the position of the main deviation angle is offset or the main deviation angle is small, will directly affect the accuracy coefficient of the processed workpiece The problem of external cutting of the tool tip, when performing external turning on the workpiece, has higher requirements for the tool; Once there is a slight deviation in the arc turning tool, it will directly affect the machining accuracy coefficient of the workpiece. Write a reasonable turning program and carefully analyze the deviation of the tool axis to correct the position of the tool. The cutting edge of the CNC lathe tool has a circular radius, and there is also a problem of the main deviation angle and the height difference between the workpiece, which can also have a certain impact on the machining accuracy of the CNC lathe. Based on this, it is necessary to comprehensively refer to the relevant parameters of the tool during the machining process of the workpiece, take into account the error problem during programming, and reduce the occurrence of potential errors from parameter factors
.
2.4 Impact of approximation error and rounding error
The so-called approximation error refers to the use of mathematical approximation algorithms in mechanical control programming to approximate the basic error of the part through precise value control. Once the precise value is too low, it will affect the accuracy of the workpiece. The so-called rounding error refers to the effective control of the linear displacement of the machined parts in the economic stepper motor CNC lathe machining through stepper pulses. The pulse equivalent is the smallest unit of product specifications, which directly affects the machining accuracy of the CNC lathe workpiece.
When the workpiece of the CNC lathe is in working condition, when the operation reaches the equivalent value of rounding pulse, rounding errors cannot be avoided. This error directly affects the size and specifications of the processed components.
3. Exploration of coping strategies
There are many factors that affect the machining accuracy of CNC lathes, but in the machining process of CNC lathes, they cannot be influenced by these factors and should be tolerated. It is necessary to find corresponding coping strategies and deal with possible factors in order to more effectively reduce error values and improve the accuracy of workpiece production.
3.1 Control of servo deviation
For CNC lathes, the role of servo systems is the most important. If you want to reduce the error of machining workpieces on the lathe and reduce the negative impact of the lathe itself, then it is necessary to attach great importance to the practical application of servo systems. Pairing high-performance and low-power driving devices with servo systems can effectively optimize the parameters of the lathe system. Meanwhile, in the turning process, suppressing speed errors based on the physical characteristics of straight workpieces can reduce a series of problems caused by speed lag; Set the open-loop gain function for arc machining to improve the contour machining accuracy of arc workpieces.
3.2 Performance control of CNC lathes
The rapid development of mechanical technology has had a significant impact on CNC lathes, and in recent years, the machining quality and efficiency of CNC lathes have been significantly improved. Meanwhile, the performance issues of CNC lathes have also received increasing attention from professionals. How to effectively improve the performance of CNC lathes has become one of the daily discussions among experts. Generally speaking, in order to improve the self performance of the lathe, an inclined bed shape can be adopted to effectively improve its bending and torsion resistance.
The use of high standardization coefficient turning tools for cutting, and equipped with automatic tool changing function for the lathe, can effectively optimize the turning effect and improve the turning accuracy level of components. Taking the specific machining of a certain axis type part on a CNC lathe as an example, a 1mm tool compensation control is reserved before rough machining of the part. Then, two rounds of lathe turning processing are adopted. The first round of radial feed rate is set to 0.5mm, and a fine machining is carried out. After the first round of fine machining is completed, there is still 0.5mm of tool compensation. At this time, a second round of deep machining can be carried out, effectively improving the accuracy of the product.
Through practical operation, it has been shown that the precision error of shaft workpieces can be effectively controlled through three rounds of machining, from rough machining to primary fine machining and secondary fine machining.
3.3 Error compensation control
When conducting CNC machining, considering the impact of approximation error on product error rate, the control system is upgraded by using mathematical calculation formulas and principles to outline the workpiece profile, improve accuracy coefficient, reduce approximation error, and ensure that the quality and accuracy coefficient of the workpiece are improved during irregular machining processing. The control of rounding errors can be prevented in the early stage through hardware processing, or the accuracy value of errors can be compensated through software processing to eliminate the influence of uncertain factors in actual operations as much as possible.
For workpieces or processes that require repeated positioning, effective measurement error calculation should be carried out before CNC machining to minimize measurement errors and provide more accurate calculation for deep precision machining. This facilitates the control of workpiece error accuracy range in the later stage, effectively improving component production efficiency and accuracy
.
3.4 Maintenance and Repair of Lathe
CNC lathes have extremely high requirements for machining accuracy, so real-time monitoring of the lathe is necessary during the working process. Once a fault prompt appears, it must be dealt with immediately, and the safety factor of processing related work data must be adjusted and optimized. Based on the feedback error information, fixed-point control and management of the control end should be carried out. When repairing the accuracy of the guide rail, use environmentally friendly guide rail coatings to improve the durability of the lathe guide rail and reduce errors caused by physical factors of the guide rail.
At the same time, during the maintenance process of the system, the measurement and machining positioning accuracy of the lathe can be improved, and the series of impacts of cutting accuracy on workpiece quality can be reduced.
4. Conclusion
There are various reasons that affect the machining accuracy of CNC lathes during workpiece processing, and the resulting error effects vary due to their varying degrees of influence. Therefore, operators must analyze the specific reasons and use CNC lathes as the basis to improve the machining quality of workpieces through servo deviation control, performance control, and error compensation control. At the same time, they must regularly repair and maintain the lathes to eliminate the impact of potential problem crises, improve the overall performance and accuracy ratio of CNC lathes, and effectively ensure the machining accuracy and quality of mechanical workpieces, Promote the further improvement of China's CNC lathe technology development level.
