Five-axis CNC bare machine tool precision improvement technology exploration

With the growing demand for precision machining in the manufacturing industry, five-axis CNC machine tools have gradually become indispensable core equipment in high-end manufacturing.

Especially in aerospace, automotive manufacturing, mold manufacturing, medical equipment, precision electronic products, and other fields, where the complexity of the parts and precision trend continue to deepen, traditional three-axis or four-axis CNC machine tools are difficult to use to meet the increasing processing requirements.

In contrast, five-axis CNC machine tools with simultaneous control of three linear axes and two rotary axes can process complex parts for all-around, multi-angle processing.

It can complete the machining of multiple surfaces through a single clamping, improving productivity and greatly reducing the positioning errors caused by repeated clamping. Thus, it possesses the outstanding advantages of high precision, high efficiency, and high flexibility.

However, with the popularization and deepening of the application of five-axis CNC machine tools in the actual production process, problems with their long-term continuous operation under the exposure of the precision of the bare machine tools have gradually appeared.

These problems mainly manifest as prolonged operation time, wear and tear on mechanical parts, thermal deformation, and frequent vibration phenomena.

These issues gradually reduce the machine tool’s geometric accuracy and positioning accuracy.
As a result, the stability and consistency of the product processing quality are affected.

For example, in the processing of high-precision aviation engine blades or automobile engine parts, even the slightest decrease in precision may increase the failure rate of parts, increasing the rate of product obsolescence, leading to economic losses and a decline in enterprises’ market competitiveness.

Enhancing technology for in-depth research can address the decline in precision in the long term operation of five-axis CNC machine tools.

Conversely, introducing advanced precision compensation technology, such as geometric error compensation, thermal deformation compensation, and dynamic error compensation, enhances machine tool performance.

Through real-time monitoring and calculation, the system dynamically corrects motion errors. This ensures the machine tool operates in a high-precision state for a long time.

Through real-time monitoring and calculation, the system dynamically corrects motion errors. This ensures that the machine tool operates in a high-precision state for a long time.

In addition, the vibration generated during the machine tool machining process will seriously reduce the machining quality. Advanced vibration suppression and dynamic control technologies are used to address this.

These technologies improve the damping characteristics of the machine tool structure and implement active control measures. As a result, they effectively reduce the negative impact of vibration on machining accuracy.

Temperature control and machining environment optimization technology should not be ignored.

Optimizing the temperature control system reduces the thermal deformation caused by machine tool temperature rise, ensuring the machine tool’s stability and consistency in machining quality.

At the same time, digital detection and error correction analysis, real-time monitoring and feedback of the machine tool processing status, advanced prevention, and dynamic adjustment of errors greatly improve the processing stability and reliability of five-axis CNC machine tools.

Overview of five-axis CNC bare machine tool precision

Bare machine tool is the basis of five-axis CNC machine tool precision, directly affecting the quality and stability of the whole machine processing.

It is embodied in the mechanical structure and the geometric accuracy of moving parts, dynamic performance, and rigidity, to ensure that high-precision machining of the tool and the workpiece is accurate relative positioning.

The improvement of the precision of the bare machine tool is affected by the machine tool’s design and manufacturing process, the precision and stability of the electrical control system, the operating environment and conditions of use, and other factors.

Among them, the electrical control system corrects the positioning deviation caused by the mechanical system error during the machine movement through a precise control strategy and real-time compensation technology.

It reduces the precision error caused by external factors such as load, friction, and temperature change.
The system also integrates thermal compensation and vibration suppression technologies.

These functions ensure the machine tool can automatically detect and correct errors during complex machining tasks.

At the same time, it maintains the precision and consistency of each axial movement.
As a result, the precision of the machine tool is improved.
This ultimately enhances the precision of the bare machine tool.

5-axis CNC bare machine tool accuracy improvement technology

Mechanical structure optimization technology

Mechanical structure optimization technology is a key step in improving the precision of 5-axis CNC machine tools. Reasonable structural design can effectively reduce the precision error caused by structural deformation or loosening of parts during the machine tool’s working process.

The core objective of mechanical structure optimization is to improve the rigidity and stability of the machine tool, which in turn enhances overall accuracy.

Specific measures include strengthening the support of key components, such as using high-rigidity materials. Another measure is increasing the cross-sectional area of components to reduce the possibility of deformation.

In addition, dynamic load analysis is crucial in structural optimization. Through computer-aided design and finite element analysis, each structural component of the machine tool is simulated to optimize the force state and avoid precision degradation caused by vibration or external impact.

In terms of specific implementation, the optimization calculation can be carried out by the following formula:

Where: K is the stiffness coefficient; F is the external force; δ is the displacement.

Increasing the stiffness coefficient can effectively inhibit the mechanical system’s deformation, which in turn ensures the stability of accuracy during the machining process.

Structural optimization design should not be limited to static rigidity. However, it should also consider dynamic performance to ensure that the machine tool can still maintain excellent accuracy in high-load, rapid movement.

Accuracy compensation technology

Accuracy compensation technology can significantly improve the machining accuracy of 5-axis CNC machine tools by detecting and correcting errors in machine tool operation in real time.

This technology monitors all errors in the machine tool’s operation, combines with the compensation algorithm to correct them, and ensures high precision performance in the machining process.

Standard compensation methods include geometric error compensation, thermal deformation compensation and control system error compensation.

Geometric error compensation refers to the precise measurement of the machine tool’s trajectory and correction of path deviations based on the measurement results.

Thermal deformation compensation monitors the temperature changes of machine components and adjusts the trajectory using temperature compensation algorithms to minimize part expansion errors due to increased temperature.

Commonly used compensation algorithms include least squares and Kalman filtering. The mathematical model of accuracy compensation can be expressed as

where: x_compensated is the compensated position; x_measured is the measured value; δi is the amount of compensation for each type of error.

Through this method, the machine tool can correct the errors in the machining path in real time to ensure continuous high-accuracy output.

Vibration Suppression and Dynamic Control Technology

Vibration is one of the important factors affecting the machining accuracy of 5-axis CNC machine tools, especially in the high-speed cutting process. The impact of vibration on the machining quality and precision of the bare machine tool is particularly significant.

The key to vibration suppression and dynamic control technology is to optimize the machine tool’s dynamic characteristics, reduce the amplitude and frequency of vibration, and improve the machining process’s stability.

This technology is mainly realized through accurate vibration analysis and feedback control systems.

Specific methods include improving the dynamic rigidity of the machine structure, adopting vibration-absorbing materials, adjusting the relative positions of the workpiece and tool, and using active control techniques to eliminate vibration in real time.

Mathematically, vibration suppression can be described by the following differential equation:

Formula (3)

where: m is the mass; c is the damping coefficient; k is the stiffness; F(t) is the external excitation force; x is the displacement;

is the velocity; is the acceleration.

Adjusting the damping coefficient and stiffness of the system can effectively reduce the amplitude of vibration, thus improving the machine tool’s accuracy.

In addition, the dynamic control system can be adjusted through real-time monitoring and feedback. Advanced control algorithms, such as adaptive control and fuzzy control, can be used to optimize the vibration suppression effect further.

These measures ensure that the machine tool’s accuracy is maintained during the high-speed cutting process.

Temperature control and processing environment optimization technology

The machining accuracy of 5-axis CNC machine tools will be significantly affected by temperature changes in the machining environment. In long-time operation, the machine components may cause geometric errors due to thermal expansion or contraction.

Therefore, temperature control and machining environment optimization technology plays an important role in precision maintenance.

The core objective of temperature control technology is to reduce machining errors due to thermal deformation by accurately controlling temperature fluctuations inside the machine tool.

Common methods include installing high-precision temperature sensors, optimizing the cooling system, using thermal isolation technology, and controlling the local temperature of different parts of the machine tool.

Mathematically, the temperature-induced deformation can be estimated by the coefficient of thermal expansion, which is calculated by the following formula:

Where: ΔL is the length change; a is the coefficient of thermal expansion; L₀ is the initial length; ΔT is the temperature change.

Controlling the temperature difference of each part of the machine tool can effectively suppress the error caused by thermal expansion.

In addition, optimizing the processing environment is not limited to temperature. Still, it should also include controlling humidity, air mobility, vibration, etc., to ensure that the processing is carried out in suitable environmental conditions, which can improve the accuracy of the bare machine tool.

Digital Inspection and Error Correction Technology

Digital detection and error correction technology is a key means of improving the precision of bare machine tools through real-time monitoring and data analysis, as well as dynamic correction of the motion error of five-axis CNC machine tools.

Relying on high-precision sensors and digital measurement systems, this technology can detect the machine tool’s displacement, speed, temperature, and other parameters in real time during the machining process.

It identifies the source of error through accurate data analysis. Then, it makes corresponding corrections through the control system.

Standard error correction methods include geometric error correction, thermal compensation and dynamic error compensation.

Mathematically, error correction usually uses an error compensation model. For example, the error optimization model based on the least squares method is as follows:

Where: E is the objective function for error minimization; x^_i is the measured value; x_i is the ideal value.

The optimization algorithm corrects the error. The digital inspection system will adjust the machine tool’s motion trajectory and control instructions in real time according to the deviation between the measured value and the target value to minimize the error in the machining process.

In addition, the error correction technology can be combined with machine learning and data analysis methods to predict and correct potential systematic errors by analyzing historical data, providing a long-lasting guarantee for improving the precision of bare machine tool.

Case study

To deeply analyze the practical application of five-axis CNC machine tool accuracy improvement technology, a high-precision five-axis machining center as a case study. The machine tool is mainly used for aviation parts processing, and the precision requirements are stringent.

The aim is to improve the stability of the machine tool’s precision over a long period in the machining process through optimization measures, including the optimal design of the mechanical structure, improvement of the temperature control system, vibration suppression, and precision compensation technology.

The machine tool was tested for machining accuracy several times before and after applying different optimization techniques, and the corresponding data were recorded. The accuracy error data of typical machining process is shown in Table 1.

Table 1 Accuracy Error Data in Typical Machining Processes

Table 1 shows the accuracy error data of a 5-axis CNC machine tool after optimization measures, including positioning error, tool trajectory error, thermal deformation error, vibration-induced error and comprehensive accuracy error.

After optimization, all error types are significantly reduced, especially the most significant improvement in positioning error, with an improvement rate of 65.38%. This shows the significant effect of optimization technology in improving the positioning accuracy of machine tools.

These data show that the optimization of the mechanical structure, accuracy compensation technology, vibration suppression, temperature control system improvement, and other measures can significantly enhance the performance of the five-axis CNC machine tool.

Through these improvements, the machine tool can effectively maintain its accuracy over a long period of processing. As a result, both production efficiency and processing quality are improved.

Conclusion

The article proposes a series of five-axis CNC bare machine tool accuracy improvement techniques, including mechanical structure design optimization, accuracy compensation technology, vibration suppression and temperature control system improvement.

The application of these measures effectively improves the accuracy stability of the machine tool during long-term work, reduces positioning error, thermal deformation error, and other problems, and provides technical support for the high-precision processing of five-axis CNC machine tools.

With the increasing demand for high precision and high efficiency in the manufacturing industry, future research on the precision improvement of five-axis CNC machine tools will develop more intelligently.

The introduction of new materials and advanced manufacturing processes, as well as the application of artificial intelligence and big data technology, will provide new breakthroughs for improving the precision of machine tools and promote the industry’s continued progress and innovation.