Abstract: This paper discusses how to utilize the Delta Electronics PUTNC-HCL-T enhanced lathe CNC system, combined with the Delta ASD series AC servo system, Delta VFD-VE series high-performance magnetic flux vector control AC frequency converter, and CS7 spindle dedicated encoder integrated control platform solution to realize the functional transformation of an economical lathe into a mid-to-high-end turning center with turning and milling composite machining capabilities. Keywords: CNC composite machining, economical lathe, turning-milling composite spindle, C-axis function 1 Introduction With the diversification, miniaturization, and increasing complexity of parts in the field of mechanical cold working, the demand for CNC (Computer Numerical Control) machine tools capable of producing high-quality, high-precision, high-efficiency, and low-cost products in the metal cutting industry is increasing. Meanwhile, as CNC machine tool manufacturers, how to produce CNC machine tools with composite machining capabilities simply, practically, efficiently, and economically based on existing production capacity, and to survive and develop in the increasingly fierce market competition, is also the main goal and direction of product development. To this end, machine tool designers and manufacturers have been making unremitting efforts. The production of a single part typically requires multiple processes. Different processes have different principles and characteristics, and different processing steps have different objectives and requirements, thus necessitating the use of different processing equipment. In traditional manufacturing processes, the production of a single part often requires multiple different processing machines. This not only increases the number of machines and the floor space required for production, thus increasing the company's investment, but also affects machining accuracy and inevitably increases production auxiliary time due to the waiting, transportation, inspection, and repositioning of parts between process and step equipment. Statistics show that this non-machining time accounts for approximately 70% to 95% of the total production cycle, significantly hindering the improvement of production efficiency. With the booming development of the metal cutting manufacturing industry, traditional machining methods, even ordinary decentralized CNC machining, may no longer meet the machining requirements of machine tool users for complex parts. The intensive composite machining method, which integrates different machining technologies on a single machine tool, has become an important direction for future machine tool development. CNC multi-process machining combines several different machining techniques onto a single CNC machine tool to perform part machining. For example, turning, milling, and drilling can all be performed on a single CNC machine tool. CNC multi-process machining is one of the most popular advanced manufacturing technologies in the metal cutting field in recent years. The biggest advantage of CNC machine tools with multi-process capabilities is that they can perform multiple machining processes on a single part clamping, thereby reducing the number of machine tools and fixtures, eliminating inter-process handling and storage, improving part machining accuracy, shortening the manufacturing cycle, and saving operating space, thus bringing benefits to the user. As shown in Figure 1, which illustrates the machining of a gas appliance burner nozzle, traditional machining methods require three basic steps: machining the outer contour using a CNC lathe or a small hydraulic profile lathe; indexing and drilling using a drilling machine with an indexing chuck or special fixture; and drilling and tapping the side using a drilling machine with a special quick-change chuck. However, when producing on a CNC lathe with multi-process capabilities, all the above machining steps can be easily and quickly achieved through a single clamping and simple NC programming, greatly improving machining efficiency. [align=center] Figure 1 Combustion nozzle of gas appliance[/align] 3 Realization of milling and turning composite function and differences from economic CNC lathe 3.1 Differences in mechanical structure CNC composite machining lathe based on turning is usually developed from ordinary CNC lathe, equipped with a multi-station tool post and a power rotating tool. The main objects processed are rotating parts such as shafts and discs. In addition to turning, it can also perform some milling, drilling and tapping. In order to realize that all or most of the rotating parts can be processed in one setup on a lathe, the lathe bed must be equipped with a rotating auxiliary power device that can be installed to install milling cutters, drills and taps, in addition to general turning tools. This is a significant feature that distinguishes the mechanical structure of CNC lathe with milling and turning composite function from that of economic lathe. 3.2 Differences in CNC control system (1) C-axis function. For CNC lathes with turning and milling functions, the spindle channel of the control system can not only execute the function of the S-code spindle and control the speed change of the machine tool spindle, but also realize the C-axis function of the machine tool spindle can be precisely indexed and the linkage function of C and Z axis, C and X axis. CNC lathes with such composite functions can not only perform turning operations on the inner and outer surfaces (including cylindrical surfaces, conical surfaces, curved surfaces, etc.) and end faces of rotating parts like ordinary CNC lathes, but also use the CZ axis linkage function to cut threads, and use the C-axis indexing function and the power rotating tool mounted on the X or Z axis to perform drilling and milling operations off the center line of rotating parts, thus greatly expanding the composite machining capabilities of CNC lathes. (2) Multi-axis control capability. Standard economical CNC lathes typically feature one spindle channel (servo spindle or inverter spindle) and two servo feed axis channels (X-axis, Z-axis). However, CNC lathes with turning and milling capabilities require additional auxiliary power units to perform drilling and milling operations. Therefore, the controller needs to provide more servo axis channels (such as A-axis, Y-axis) to control the auxiliary power unit and meet control requirements, as shown in Figure 2. [align=center] Figure 2 Multi-axis Machining[/align] 4. Turning-Milling Composite Machining Solution Based on Delta Electronics Automation Platform Based on the above analysis, we understand that the transition from economical lathes to CNC lathes with composite machining capabilities requires simultaneous attention to both the machine tool's electrical control architecture and mechanical design. For the latter, since each machine tool manufacturer's design is different, the openness of Delta Electronics' CNC system PLC can fully meet different mechanical design needs. This article will not discuss the mechanical part further, but mainly introduces the overall solution that Delta Electronics can provide in terms of electrical control. Delta Electronics, with its extensive portfolio of electromechanical automation products, not only offers the PUTNC-H4CL-T enhanced lathe CNC system to meet the control requirements of CNC lathes with turning and milling functions, but also provides a complete set of industrial automation products, including Delta ASD series AC servo systems, Delta VFD-VE series AC frequency converters, and CS7 spindle encoders, to meet electrical control needs. This enables machine manufacturers to produce CNC machine tools with composite machining capabilities simply, practically, efficiently, and economically, based on their existing production capacity, thus bringing greater benefits to both machine manufacturers and end users. 4.1 Introduction to the CNC Control System Based on the market demand and future technological trends of CNC machine tools with composite machining capabilities in the metal cutting industry, Delta Electronics launched the PUTNC-H4CL-T enhanced lathe CNC system at the end of 2006 (Figure 3). The innovatively designed PUTNC-H4CL-T enhanced lathe CNC system adopts a completely new hardware design architecture, fully inheriting the stability and ease of operation of Delta Electronics' CNC systems, making its performance even better. PUTNC-H4CL-T Technical Features: [align=center] Figure 3 PUTNC-H4CL-T Lathe CNC System[/align] (1) Open system architecture with embedded PLC. The LCD interface is customizable and can meet the customized needs of different machinery manufacturers. (2) 10.4-inch color LCD display with a larger and clearer field of view. (3) Split-type operating platform for easier use and more flexible operation. (4) Maximum number of servo control channels: 4 servo axes (X, Z, Y, A). (5) Number of spindle control channels: can control 1 servo spindle or frequency converter spindle. The spindle control has S spindle function and C axis arbitrary angle indexing function. (6) Design concept of lathe and milling machine, which can realize the linkage function of C and Z axis and C and X axis, and can perform rich processing functions such as spiral groove milling and high-precision thread processing. (7) With the auxiliary power device that rotates the milling cutter, drill bit and tap, it can realize composite machining functions such as rigid tapping, X-axis drilling, Z-axis drilling and eccentric rigid tapping. 4.2 CNC system parameter configuration Using the parameter interface of the PUTNC-H4CL-T lathe CNC system, machine tool manufacturers can easily realize the spindle function and auxiliary power head function through the corresponding parameter configuration without editing the CNC PLC program. Thus, it is easier to build the various control functions required for CNC lathe composite machining, as shown in Figure 4. [align=center] Figure 4 Automatic interface and spindle parameter configuration interface of CNC system[/align] 4.3 NC programming of CNC lathe composite machining For the PUTNC-H4CL-T lathe CNC system, the system has developed dedicated NC instruction code, which can easily control the spindle indexing, auxiliary power head rotation, and realize composite machining functions such as rigid tapping, X-axis drilling, Z-axis drilling and eccentric rigid tapping. Table 1 lists the commonly used NC instruction codes. [align=center]Table 1 Commonly Used NC Programming Codes for Composite Machining[/align] 5 Delta ASD Series AC Servo Systems The Delta ASD-A series advanced AC servo system and the ASD-B standard AC servo system are two mainstream servo products launched by Delta Electronics in 2003 and 2005 respectively. They can fully meet the needs of industrial users, especially in CNC machine tool applications where they perform even better. Delta servo systems are designed for the characteristics of CNC machine tools: (1) Built-in complete three basic control functions (position/speed/torque modes), which can be easily connected to the host controller. (2) Good dynamic response, servo settling time of 1ms, and acceleration time of 10ms from -3000RPM to 3000RPM under no-load conditions. (3) The robust PDFF (Pseudo-Derivative Feedback and Feedforward) control architecture responds faster and has a stronger ability to suppress and compensate for external interference, thus ensuring that the servo positioning or speed is minimally affected when the cutting tool is cutting or when other external forces suddenly intervene, as shown in Figure 5. (4) The servo's automatic gain adjustment function can automatically assess the load and set the servo gain reasonably, making servo debugging simpler and faster, and the servo positioning more accurate, without overshoot or acceleration overshoot. [align=center] Figure 5 Robust PDFF Control Architecture[/align] (5) It provides resonance suppression and low-pass filter functions, which can effectively compensate for mechanical deficiencies and defects. (6) The Delta ASD-A series advanced AC servo system has indexing positioning function, which can easily realize servo tool magazine control when combined with the I/O planning of the CNC system PLC, as shown in Figure 6. [align=center] Figure 6 ASD-A series built-in servo indexing function[/align] 6 Delta VFD-VE series high-performance magnetic flux vector control AC inverter The Delta VFD-VE series is a brand new product launched in 2007 to meet the needs of the high-end market. Its frequency output range is 0～600 Hz, while the output of the V2H model is as high as 3600Hz, which can fully meet the control requirements of high-speed spindles of CNC machine tools. With the unique position control function, combined with the C-axis function of the H4CL-T system, the spindle can also realize arbitrary angle indexing function. Features of VFD-VE series AC inverter: (1) Built-in V/F, vector control, torque control, and position control functions. (2) Frequency output range is 0～600 Hz, and the output of high-end models is as high as 3600Hz. (3) Speed ​​control accuracy: FOC+PG closed loop control, up to +/-0.02%. (4) Low speed torque: up to 150% at 0.5HZ. (5) Can perform motor parameter and load inertia estimation and high-speed field weakening curve estimation. (6) Mechanical brake control function and deceleration function during instantaneous power outage. (7) Motor temperature feedback protection (PTC) function. 7 Delta CS7 ​​spindle dedicated encoder Features of Delta CS7 ​​spindle dedicated encoder: (1) Maximum adaptable speed up to 8000RPM, maximum corresponding frequency of 300kHz. (2) Mechanism design can adapt to heavy load working environment, vibration resistant, and high temperature resistant. (3) Aviation connector, protection level of IP65, suitable for high oil and gas environment. (4) Modular design, multiple specifications available, high reliability. 8 Conclusion Composite machining technology is an important direction for the future development of CNC machine tools. Delta Electronics' customized overall automation solution can fully meet the functional transformation of economic machine tools to high-end machine tools with composite functions for machine tool manufacturers. It enables machine tool manufacturers to find higher target markets and make products more competitive. For end users of machine tools, CNC machine tools employing composite machining technology, combined with the stability and ease of use of Delta Electronics' control system, will transform production processes from traditional decentralized production to advanced intensive production methods. This will lead to a leap in both the quality and quantity of products and parts manufacturing cycles, thereby creating greater economic benefits. Clearly, because the solution integrates a single-brand automation platform, end users of Delta Electronics CNC machine tools can easily achieve the economic and technical advantage of maximizing the Total Benefit of Ownership (TB0) throughout the equipment's lifecycle.