Research and prospects of CNC lathe

Abstract

With the development of the manufacturing industry and the continuous progress of science and technology, as one of the core equipment of the high-end manufacturing industry, CNC lathe is also developed and improved. After searching a large amount of literature, through the elaboration of the current domestic and foreign research institutions for the CNC lathe research history, development level and development status, comparative analysis of different types of CNC lathe structure, characteristics and applications, concluded that the CNC lathe is the best choice for the current rotary parts machining manufacturing tools. On this basis, it analyzes and summarizes the tool path planning, cutting process optimization, high-speed cutting technology and other key technical issues to be solved in the future development of CNC lathe, and finally looks forward to the development trend of CNC lathe, in order to provide references for related research.

Keywords:

• CNC lathes
• development status
• key technology
• precision machining
• development trend

Reviewing Editor:

• DT Pham
• Chance Professor of Engineering
• School of Mechanical Engineering
• University of Birmingham
• Edgbaston
• UK

Subjects:

• Industrial Engineering & Manufacturing
• Mechanical Engineering
• Mechanical Engineering Design
• Manufacturing Engineering

1. Introduction

A machine tool is a machine used to make machines, also known as “workhorses” or “tool machines.” As early as the fifteenth century has appeared early machine tools, in 1774 the British Wilkinson invented a gun barrel boring machine is considered the world’s first real sense of the machine tool, which solved the Watt steam engine cylinder processing problems. To the eighteenth century, various types of machine tools appeared one after another and rapid development, such as lathes, gantry-type machine tools, horizontal milling machines, hobbing machines, etc., for the industrial revolution and the establishment of modern industry laid the foundation for manufacturing tools (Wang & Liu, 2013).

Nowadays, manufacturing industry is still the pillar industry of many countries, with the development of industrial production and the continuous updating of technology, as one of the industrial mother machine CNC lathe (Numerical Control Lathe) has become an important equipment in modern manufacturing. Precision machining requirements of the parts need to have a high degree of accuracy, stability and reliability of the machine tool to achieve high precision, high surface quality parts processing, based on the development of computer-controlled CNC lathe just to meet this requirement. CNC lathe is based on computer-controlled automated machine tools, mainly used for rotary workpiece processing, it can be pre-programmed instructions to accurately complete a variety of processing tasks, which plays an important role in the field of precision turning.

2. Classification and research status of CNC lathe

2.1. Classification of CNC lathes

CNC lathe is one of the more widely used CNC machine tools. It is mainly used for shaft parts or disk parts of the internal and external cylindrical surface, any cone angle of the internal and external conical surface, complex rotary internal and external surfaces and cylindrical, tapered threads and other cutting, and can be grooved and hole processing, etc (CNC Skills Teaching Materials Writing Group, 2006), its common classification is shown in Table 1.

Table 1. Classification of CNC lathes.

Basis of classification	Types	Characteristic
Spindle position	Vertical	Spindle perpendicular to the ground
	Horizontal	Spindle parallel to the ground
Number of spindles	Uni	The CNC controls only one axis
	Spherical	CNC control of two axes
	Multi-axis	CNC system to control multiple axes
Types of CNC systems	Servo control	The control system usually consists of servo motors, position sensors, a motion control card and a computer for programming.
	Cartesian coordinate system	The CNC system uses a right-angle coordinate system, which realizes machining by controlling the movement of the workpiece in the x, y, and z directions
	Coordinate system of rotation	The CNC system uses a rotary coordinate system, which realizes machining by controlling the rotation of the workpiece around the x, y, and z axes.
	Multiple coordinate axes	The CNC system consists of multiple axes, each of which can be independently controlled to realize the machining of complex parts.
Functionality	Economy model	Retrofitting the feeding system of ordinary lathes with stepper motors and microcontrollers
	Normal type	The structure is specially designed and equipped with a universal CNC system according to the turning requirements.
	Turning Center	On the basis of the ordinary CNC lathe added power head, more advanced CNC lathe has a tool magazine, can control three axes

Selected CNC lathe three common classification for analysis and comparison, its specific content is as follows.

2.1.1. Classification according to spindle position

CNC lathes can be categorized into vertical CNC machine tools and horizontal CNC lathes according to the spindle position.

Vertical CNC lathe, as shown in Figure 1, has a large circular table, which is mainly used to place the workpiece, and the whole machine is in parallel with the ground. Vertical CNC machine tools are mainly used to process some large and complex parts with large radial dimensions and relatively small axial dimensions.

Figure 1. Vertical lathe.

Horizontal CNC lathe as shown in Figure 2, it also includes CNC inclined guideway horizontal machine and CNC horizontal guideway horizontal machine, these types of machine structure has a strong rigidity and wear resistance and easy to chip removal.

Figure 2. Horizontal lathe.

2.1.2. Classification by number of spindles

According to the number of spindles of CNC lathe can be divided into ordinary CNC lathe, two-axis CNC lathe and multi-axis CNC lathe.

Ordinary CNC lathe shown in Figure 3, this type of CNC lathe only has a spindle, through the computer program automatically control spindle movement, applicable to general turning processing needs.

Figure 3. Ordinary CNC lathe.

Dual spindle CNC lathe as shown in Figure 4, CNC lathe with dual spindles can simultaneously carry out symmetrical processing of workpieces at both ends to improve productivity.

Figure 4. Double spindle CNC lathe.

Multi-axis CNC lathe shown in Figure 5, it has more than one working axis of the CNC lathe, can realize the complex multi-axis linkage processing, such lathes operating procedures are complex, high cost, applicable to the processing requirements of the use of higher.

Figure 5. Multi-axis CNC lathe.

2.1.3. Classification according to field of application

General-purpose CNC lathe: suitable for the machining of many different types of parts. Generally small and medium-sized machines, mostly used for machining small and medium-sized batches of parts.

Specialized CNC lathes: Lathes designed for specific industries or specific parts machining needs, such as automotive parts, aerospace fields, etc. They are generally used in high volume production processes.

2.2. Status of research

The origins of CNC technology can be traced back to the 1940s and 1950s. 1949, under the support of the U.S. Air Force Department, Parsons formally accepted the commission to cooperate with the MIT Servo Agency Laboratory, began to engage in the development of CNC machine tools. After three years of research, the world’s first experimental prototype of CNC machine tools was successfully tested in 1952, and its control device consists of more than 2000 electronic tubes. The birth of this CNC milling machine marked the beginning of the era of digital control of machinery manufacturing (Huaixing, 2006)^. The 1970s and 1980s were the period when CNC lathes were widely adopted and developed. With the advancement of computer technology, electronic technology and sensor technology, CNC systems became more reliable and flexible. During this period, the functions and performance of CNC lathes continued to improve, enabling more precise control and higher machining efficiency. After entering the 1990’s, the development of CNC lathe entered a brand new stage. The rapid development of computer technology, the integration of control systems and key components of innovation, so that the CNC lathe in the accuracy, speed, process control and interface and networking have made significant progress. At the same time, the application fields of CNC lathes are also expanding, including aerospace, automobile manufacturing, electronic equipment, medical equipment and other industries (Kun et al., 2019).

Typical CNC lathe structure evolution is shown in Figure 6. CNC turning machine structure from the early 2-axis feed flat bed, 2-axis feed inclined bed and other classic structure, the development of 4-axis feed and double tool holder, multi-spindle and multi-tool holder for rotary parts such as high-efficiency turning machining center structure, Further development into a multifunctional mill-turn machining center structure that can adapt to complex parts “once clamped, all finished” (Qiang, 2021).

Figure 6. Evolutionary process of CNC lathe structure.

From the thesis research of Zhou Xiaofeng, Zhang Yuxiang, He Weiwei, etc., it was found (Weiwei, 2021; Yuxiang, 2022; Zhiping, 2022; Zhou et al., 2018) that at this stage, the research of CNC lathe mainly focuses on high-speed cutting technology, precision turning technology, adaptive control technology, simulation and optimization of turning machining and multi-axis linkage technology.

3. Key technology research of CNC lathe

CNC lathe key technology research involves a number of aspects, the continuous optimization and progress of its key technologies to promote the continuous development of CNC lathe technology, to provide strong support for the development of the manufacturing industry. The key technologies of CNC lathe in the past 10 years are summarized in Table 2.

Table 2. Key technologies for CNC lathes.

Key technologies	Key content
High-speed cutting technology	High-speed cutting can increase the machining speed, reduce the cutting force, reduce the cutting temperature, thus improving the machining quality and efficiency.
Precision machining technology	Precision machining technology includes high-precision tools, error compensation technology, machining process optimization, etc., which can improve machining accuracy and reduce product errors.
Error compensation technology	Develop error compensation algorithms and software to accurately compensate for various errors in the machining process, thereby improving machining accuracy.
Intelligent control technology	Through the introduction of artificial intelligence, machine learning and other technologies, the automation and intelligence of the processing process can be realized, and the processing efficiency and precision can be improved.
Networking and remote control technology	By connecting CNC lathes to the Internet, remote monitoring and management can be realized to improve productivity and equipment utilization.
Composite Processing Technology	By integrating multiple machining methods (e.g., turning, milling, drilling, etc.) on a single CNC lathe, it realizes automation and integration of multiple machining processes, improves machining efficiency and reduces costs.
Flexible Processing Technology	Flexible processing technology includes modular design, reconfigurable process flow, intelligent scheduling, etc., which can adapt to the processing of different types and batches of parts, and can quickly respond to production demand and improve production efficiency.
Reliability technology and security	Enhancement of machine tool troubleshooting and early warning mechanisms to ensure proper machine tool operation and operator safety

The continuous research and application of these key technologies have promoted the technological progress and industrial upgrading of CNC lathes and improved the overall level of the machinery manufacturing industry. The specific research of each researcher is as follows.

3.1. Tool path planning

Yi Jiang, Junfei Jiang, Timiryazev V A, Khostikoev M Z et al. studied the key technology of tool path planning in their papers (Jiang & Jiang, 2023; Timiryazev et al., 2019). Tool path planning is one of the key technologies in CNC lathe, which determines the trajectory of the tool on the workpiece and the machining sequence. Researchers are committed to develop efficient tool path planning algorithms to reduce machining time, improve machining quality and reduce energy consumption.

3.2. Cutting process optimization

Agrawal R, Kumar N, Chu W L, Xie M J, Gugulothu B, Kumsa D K, and other researchers (Agrawal et al., 2022; Chu et al., 2020; Gugulothu et al., 2021) have analyzed and optimized the cutting process through various methods on factors such as cutting parameters, tool material and geometry to achieve the optimization of the cutting process as a way to increase the machining efficiency, reduce the cost, and improve the machining quality.

3.3. High-speed cutting technology

Bo He, Huang K, Gong H, et al. (He, 2019; Huang et al., 2022; Shen & Xu, 2022) conducted relevant research on high speed cutting technology in their papers. As an advanced and practical manufacturing technology, high-speed cutting technology has been widely used in aerospace, defense industry, electronics and precision machinery, and has shown strong vitality and good market application prospects. High-speed cutting technology is a technology that realizes high-efficiency and high-quality processing by improving cutting speed and cutting efficiency. This technology is widely used in the field of precision machining, which can significantly improve machining efficiency, reduce machining costs, and improve the surface quality and accuracy of the workpiece. Its specific research includes high-speed tool design, cutting parameter optimization, cutting force monitoring and control. The application of this technology to CNC lathe machining is of great significance.

3.4. Precision turning technology

Cheng Kui, Proskuryakov N A and other researchers (He et al., 2017; Proskuryakov et al., 2018) in their papers on precision machining during turning. Precision turning technology is a machining process used to manufacture high-precision components. It achieves machining objectives by cutting a rotating workpiece on a lathe using specialized equipment and tools. Its main research includes cutting process control, process parameter optimization, tool and tool material research, and stability and repeatability research of machining process.

3.5. Adaptive control techniques

Adaptive control technology of CNC lathe has been studied in the articles of Nahornyi V, Panda A, Valíček J et al. (Nahornyi et al., 2021; Saleh et al., 2021). The adaptive control technology of CNC lathe refers to the control technology that autonomously adjusts the processing parameters and strategies by real-time sensing and analyzing the processing status during the CNC lathe machining process. The goal of this technology is to improve machining efficiency, ensure machining quality and reduce the need for manual intervention. The research of this technology mainly includes automatic process identification and selection, automatic tool wear monitoring and adjustment, adaptive compensation control, automatic selection of the best machining path, intelligent trimming and reprogramming.

3.6. Turning simulation and optimization

Ji Qianqian, Zhang Youlin, Seçgin Ödeng et al. (Qianqian, 2022; Seçgin, 2021; Zhang, 2022) in their article on virtual simulation and optimization of turning machining. CNC lathe turning machining simulation and optimization refers to the use of computer simulation technology and optimization algorithms to simulate and analyze the turning process of CNC lathe in order to optimize the machining efficiency and quality. In CNC lathe turning machining simulation, it is first necessary to establish a mathematical model or virtual model to describe the structure of the CNC lathe, cutting force, tool trajectory and other key parameters. Through the simulation software, various physical phenomena in the machining process can be simulated, such as cutting force distribution, material removal, thermal deformation and so on. For the optimization of CNC lathe turning machining, optimization algorithms can be applied to seek the optimal machining strategy or parameter settings. By defining the optimization objective function and constraints, combined with factors such as cutting force, machining quality and machining efficiency, the optimization algorithm can search for the best machining scheme or parameter combination.

The application of CNC lathe turning machining simulation and optimization technology can effectively reduce the number of trial and error and modification in actual machining, and improve machining efficiency and quality. This technology plays an important role in improving the efficiency of turning machining, reducing costs and optimizing product quality.

3.7. Multi-axis technology

Fu F, Bao X Y, Lv Y, Li C, Jin Y et al. (Fu & Bao, 2016; Lv et al., 2021) Multi-axis linkage technology of CNC lathe is studied in the paper. Multi-axis linkage technology of CNC lathe refers to the realization of linked motion of workpiece in multiple directions by controlling multiple axes of motion simultaneously in the CNC lathe system. It allows simultaneous control of multiple axes on the lathe in a single machining process, realizing more complex machining operations and precise motion control. CNC lathe multi-axis linkage technology usually involves linkage control of parameters such as workpiece rotation, feed and axial movement. Common multi-axis linkage control includes 2-axis linkage control, 3-axis linkage control and multi-axis linkage control.

3.8. Environmentally friendly and energy efficient technologies

Cahyati S, Agrawal C, et al. (Agrawal et al., 2020; Cahyati et al., 2016) in their papers studied the relationship of CNC lathe with environment and energy saving. Due to the need for sustainable development, research on precision machining CNC lathes also needs to focus on environmentally friendly and energy saving technologies. It focuses on how to reduce energy consumption and waste generation and optimize the energy efficiency of machine tools. Specific aspects of the research include the application of new materials and lubricants to reduce friction and wear, as well as the study of energy-efficient cooling and filtration systems.

Overall, the key technology research of precision machining CNC lathe covers tool path planning, cutting force modeling and control, cutting process optimization, high-speed cutting technology, precision turning technology, adaptive control technology, turning machining simulation and optimization, multi-axis linkage technology, environmentally friendly and energy-saving technology. The continuous innovation and development of these key technologies will promote the performance of precision machining CNC lathes to meet the manufacturing industry’s demand for high-precision parts.

4. Research trends and perspectives

Since the twenty-first century, with the continuous development of CNC technology and the expansion of the field of application, because of the general trend of digitalization of the required equipment, CNC lathes play an increasingly important role in the development of various manufacturing-related industries. The development of CNC lathe can be solved for the single piece, small batch parts, especially in the shape of complex, high precision machining requirements of the parts of the production of automation.The development trend of CNC lathe in the next decade will focus on high-speed cutting, precision machining, intelligent control, networking and remote control, composite machining, flexible machining, reliability technology and safety protection, green manufacturing, Internet of Things and big data.

4.1. High-speed, high-precision machining

As technology advances and the manufacturing industry’s demand for high-precision parts increases, researchers will continue to work to improve the machining speed and accuracy of CNC lathes. They will explore new cutting processes, optimize cutting parameters and improve tool design to achieve higher speed and higher precision machining. According to related research (Qiang, 2021), the continuous progress and application of advanced manufacturing technologies have greatly shortened the machining time, improved the machining efficiency and machining accuracy, and the changes in machining efficiency and machining accuracy are shown in Figure 7 (Byrne et al., 2003; McKeown, 1987).

Figure 7. Development of machining efficiency and accuracy. (a) Manufacturing technology and processing efficiency, (b) Processing equipment and processing accuracy.

4.2. Precision control systems

Precision machining requires accurate motion control and position feedback, so research on CNC lathes will focus on the development and improvement of precision control systems. Researchers will study high-resolution position sensors, precision motion control algorithms and real-time feedback systems to achieve more accurate machining control and higher precision motion smoothness.

4.3. Precision tools and cutting technologies

Precision machining requires high quality and performance of tools. Therefore, researchers will continue to develop and improve precision tools and cutting technologies to adapt to different materials and machining requirements. They will study the improvement of tool materials, optimization of tool geometry, and application of surface coating technology to improve cutting efficiency and work-piece surface quality.

4.4. Deviation compensation and error correction

During precision machining, some machining errors and deviations are generated due to mechanical structure errors, thermal deformation and other factors. Therefore, researchers will continue to study the deviation compensation and error correction methods to improve the machining accuracy and stability through real-time monitoring and correction.

4.5. Flexible production and adaptive control

The manufacturing industry’s demand for individualized and small-lot production is becoming more and more obvious, so the research on precision machining CNC lathes will develop in the direction of flexible production and adaptive control. Researchers will work to develop intelligent process planning and control systems to realize automated workpiece switching, adaptive process adjustment and flexible production scheduling to improve productivity and flexibility.

Intelligent, open, networked (Zhu, 2020): machine operation and programming and other aspects of intelligence, set up intelligent human-computer interaction page, mechanical equipment, such as autonomous programming; also includes monitoring intelligence, system failure judgment intelligence, etc., for the maintenance of equipment and fault diagnosis to provide convenience; in order to allow the traditional CNC system industrialization manufacturing process and CNC system closure of the problem to be effectively resolved. Open CNC system came into being. Nowadays, industry scholars are getting richer and richer on the research of open CNC system, and famous CNC machine tool manufacturers around the world have put forward new ideas and new concepts, and the networking of CNC machine tools is an important direction for the development of CNC field in the future.

Overall, research on precision machining CNC lathes will focus on high-speed, high-precision machining, precision control systems, tooling and cutting technology, error compensation and adaptive control. The progress of these researches will promote the improvement of precision machining technology, promote the development of manufacturing industry, and meet the market demand for high-precision parts. At the same time, with the development of artificial intelligence, the Internet of Things and big data, precision machining CNC lathes will also be combined with these technologies to achieve a more intelligent, digital and automated production method.

5. Conclusion

Overall, the research goal of CNC lathes is to improve machining efficiency while increasing machining accuracy and quality. Through innovative cutting technologies, control strategies and process optimization, CNC lathes will be able to meet the growing demand for parts machining and play an important role in the development of the manufacturing industry Overall, the continued development of CNC machine tools in terms of precision, speed, functionality and intelligence will bring about even greater changes and enhancements to industrial manufacturing. With the continuous progress of science and technology, the research and application of CNC machine tools will continue to promote the innovation and development of the manufacturing industry.

Disclosure statement

No potential conflict of interest was reported by the author(s).