Key words: CNC compound machining, economical lathe, turning and milling, composite spindle, C-axis function
With the diversification and increasing complexity of parts in the field of mechanical cold processing, the metal cutting industry is increasingly demanding CNC (computer numerical control) machine tools capable of producing high quality, high precision, high efficiency and low cost products. At the same time, as a CNC machine tool manufacturer, how to produce a CNC machine tool with complex processing capability based on the existing production capacity, which is simple, practical, efficient and economical, can survive and develop in the increasingly fierce market competition. The main goals and directions of research and development. For this reason, the design and manufacture of machine tools have been making unremitting efforts.
Second, CNC composite processing technology
The production of a part product usually requires multiple processes to complete. Different process methods have different processing principles and characteristics. Different processing processes have different processing purposes and requirements, so they each need different processing equipment. achieve.
In the traditional manufacturing process, the manufacture of a part often requires multiple, multiple different processing equipment to complete. This not only increases the number of equipment and the floor space of the production plant, which increases the investment of the enterprise, and also affects the factors such as waiting, transporting, inspecting and repositioning the clamping between the process and the process equipment during the production process. Processing accuracy also inevitably increases the production assistance time. Statistics show that this part of the non-processing time will account for about 70% to 95% of the total production cycle of parts, which greatly restricts the improvement of production efficiency.
With the booming metal cutting manufacturing industry, the traditional processing methods, even the use of ordinary decentralized CNC machining methods, may not meet the processing requirements of machine tool users for complex parts. Instead, it is an intensive composite processing method that combines different processing technologies on the same machine tool, and has become an important direction for future machine tool development.
CNC compound machining is to put several different machining processes on the same CNC machine to realize the machining of parts. For example, turning, milling and drilling can be performed on a CNC machine. CNC composite machining is one of the most popular advanced manufacturing technologies in the field of metal cutting in recent years. The biggest advantage of CNC machine tools with combined machining capability is that it can realize the processing of many different parts of the parts through one-time part clamping, thus reducing the number of machine tools and fixtures, eliminating the handling and storage between processes, and improving the machining accuracy of parts. The purpose of shortening the manufacturing cycle and saving the working area is to bring benefits to the user.
According to Figure 1 shows the machining diagram of the gas burner combustion nozzle parts. The traditional machining method requires three basic machining processes: machining the outer contour with a CNC lathe or a small hydraulic copying lathe; using the drilling machine to install the indexing chuck or Special fixtures are used to index the holes; special drill-changing chucks are used to drill and tap the sides.
When it is produced on a CNC lathe with composite function, simple NC programming can quickly and easily realize all the above processing steps through one-time process clamping, which greatly improves the processing efficiency.
Figure 1 Gas burner combustion nozzle
Third , the realization of the turning and milling composite function and the difference with the economical CNC lathe
3.1 Differences in mechanical structure
Turning-based CNC composite machining lathes are usually developed on the basis of ordinary CNC lathes, with a multi-station tool holder and power rotary cutters. The main processing objects are shafts and discs. Body parts. In addition to the main turning operations, partial milling, drilling and tapping are also possible. In order to realize the whole or most of the processing of the rotary parts by means of one clamping on one lathe, in addition to the general turning tools, it is also possible to install the upper milling on the bed of the lathe. Rotary auxiliary power units such as knives, drills and taps are the distinguishing features of the mechanical lathes with the turning and milling functions of CNC lathes that are distinguished from economical lathes.
3.2 Differences in CNC Control System
(1) C-axis function. For the CNC lathe with turning and milling functions, the spindle channel of the control system can not only perform the function of the S code spindle, but also control the spindle spindle speed change, and also realize the C axis function and C and the machine spindle can be accurately indexed. Z-axis, C and X-axis linkage function. The CNC lathe with such a composite function can not only perform turning machining on the inner and outer surfaces (including cylindrical surface, tapered surface, curved surface, etc.) and end surface of the rotary body part like the ordinary numerically controlled lathe, but also can use the CZ axis linkage function to thread the thread. The shaft indexing function and the power rotary tool mounted on the X or Z axis perform drilling and milling away from the center line of the rotating part, which greatly expands the ability of the CNC lathe.
(2) Multi-axis control capability. The standard economical CNC lathe usually has one spindle channel (servo spindle or inverter spindle) and two servo feed axis channels (X-axis, Z-axis), and the CNC lathe with turning and milling functions needs to be added. The auxiliary power unit is used for drilling and milling. Therefore, the controller needs to provide more servo shaft channels (such as A-axis and Y-axis) to control the auxiliary power unit to meet the control requirements, as shown in Figure 2.
Figure 2 Multi-axis machining
Fourth, based on the Delta-CIMIC automation platform milling machining solutions
Based on the above analysis, we understand that the transition from economical lathes to CNC lathes with complex machining capabilities is required to meet both the electrical control architecture and the mechanical design of the machine tool. For the latter, because each machine tool The manufacturer's machine design is not the same, and the openness of the PLC using the Zhongda Dentsu CNC system can fully meet the different mechanical design requirements. This article will not discuss the mechanical part, mainly introduces the electrical control of Zhongda Dentsu. The overall solution that the aspect can provide.
In addition to the PUTNC-H4CL-T reinforced lathe CNC system, the Zhongda Dentsu, which is rich in electromechanical automation products, can meet the control requirements of CNC lathes with integrated turning and milling functions, and can also provide Delta ASD series AC servo system. Delta's VFD-VE series AC inverters, CS7 spindle encoders and other complete industrial automation products to meet the needs of electrical control, enabling machinery manufacturers to be simple, practical, efficient and economical based on existing production capacity. The production of CNC machine tools with combined processing capabilities has brought greater benefits to machine manufacturers and end users.
4.1 Introduction to CNC Control System
Based on the market demand and future development of CNC machine tools with metal machining capabilities, Zhongda Dentsu introduced the PUTNC-H4CL-T enhanced lathe CNC system to the market at the end of 2006 (Figure 3). The innovative design of the PUTNC-H4CL-T reinforced lathe CNC system adopts a new hardware design architecture, which fully inherits the stability and operational ease of the Zhongda Dentsu CNC system, making it even better.
PUTNC-H4CL-T technical features:
Figure 3 PUTNC-H4CL-T CNC system
(1) Open system architecture with embedded PLC. The LCD interface can be planned to meet the customization needs of different machine manufacturers.
(2) 10.4 inch color liquid crystal display with a larger field of view and clearer.
(3) Split operating platform, which is more convenient to use and more flexible in operation.
(4) Maximum number of control servo channels: 4 servo axes (X, Z, Y, A).
(5) Number of spindle control channels: It can control 1 servo spindle or variable frequency spindle. The spindle control has S spindle function and C axis arbitrary angle indexing function.
(6) The design concept of the car and milling machine can realize the linkage function between C and Z axis, C and X axis, and can carry out rich processing functions such as spiral groove milling and high precision thread machining.
(7) Auxiliary power units that rotate with milling cutters, drills and taps can realize complex machining functions such as rigid tapping, X-axis drilling, Z-axis drilling, and eccentric rigid tapping.
4.2 Parameter configuration of CNC system
Using the parameter interface of the PUTNC-H4CL-T lathe CNC system, the machine tool builder can easily implement the spindle function and the auxiliary power head function through the corresponding parameter configuration without editing the CNC PLC program. Therefore, it is easier to construct various control functions required for CNC lathe compound processing, as shown in Fig. 4.
Figure 4 Automatic interface and spindle parameter configuration interface of the CNC system
4.3 CNC programming of CNC lathe compound machining
For the PUTNC-H4CL-T lathe CNC system, the system has developed a special NC command code, which can easily control the spindle indexing, auxiliary power head rotation, rigid tapping, X-axis drilling, Z-axis drilling. , eccentric rigid tapping and other composite processing functions. The table below lists the commonly used NC instruction codes.
Table Common machining commonly used NC programming code
V. Delta ASD series AC servo system
Delta's ASD-A series advanced AC servo system and ASD-B standard AC servo system are two mainstream servo products that Delta Electronics introduced to the market in 2003 and 2005 respectively, which can meet the needs of industrial users. Especially in the application of CNC machine tools, the performance is even better.
Delta servo is aimed at the field of CNC machine tools:
(1) Built-in three basic (position/speed/torque mode) basic control functions, which can be easily connected to the upper controller.
(2) The dynamic response is good, the servo setting time is 1ms, and the acceleration time of -3000RPM~3000RPM is 10ms under no-load condition.
(3) PDFF (Pseudo-Derivative Feedback and Feedforward) The robust control architecture is faster and has stronger suppression and compensation for external disturbances, thus ensuring the cutting moment of the turning tool or the sudden intervention of other external forces. The speed is rarely affected, as shown in Figure 5.
(4) The automatic gain adjustment function of the servo can automatically evaluate the load condition and set the servo gain reasonably, so that the servo debugging is simpler and faster, and the servo positioning is more precise, without overshoot and acceleration overshoot.
Figure 5 PDFF Control Architecture
(5) Provides resonance suppression function and low-pass filter function, which can effectively compensate for mechanical defects and defects.
(6) Delta's ASD-A series advanced AC servo system has indexing positioning function, which can easily realize servo tool magazine control with the I/O planning of CNC system PLC. See Figure 6.
Figure 6 ASD-A series built-in servo indexing function
VI . Delta VFD-VE series high performance magnetic beam vector control AC frequency converter
The Delta VFD-VE series is a new product launched in 2007 to meet the high-end market. Its frequency output range is 0~600 Hz, while the V2H output is up to 3600Hz, which fully meets the control requirements of CNC machine high-speed spindles. With the unique position control function, the C-axis function of the H4CL-T system can also realize the arbitrary angle indexing function of the spindle.
VFD-VE series AC drive features:
(1) Built-in V/F, vector control. Torque control, as well as position control.
(2) The frequency output range is 0~600 Hz, and the output of high-end models is up to 3600Hz.
(3) Speed â€‹â€‹control accuracy: FOC+PG closed loop control, up to +/- 0.02%.
(4) Low speed torque: 0.5HZ can reach 150%.
(5) Motor parameter and load inertia estimation and high-speed field weakening curve estimation function can be performed.
(6) Mechanical brake control function and deceleration function during instantaneous power failure.
(7) Motor temperature feedback protection (PTC) function.
Seven, Delta CS7 â€‹â€‹spindle special encoder
CS7 spindle dedicated encoder features:
(1) The highest adaptation speed is up to 8000RPM, and the highest corresponding frequency is 300kHZ.
(2) The mechanism design can adapt to heavy load working environment, withstand vibration and high temperature.
(3) Aviation joints with IP65 protection for high oil and gas environments.
(5) Modular design, various specifications are available, and reliability is high.
Eight, the conclusion
Composite processing technology is an important direction for the development of CNC machine tools in the future. The overall automation solution for the standardization of the company is able to meet the functional transformation of economical machine tools to high-end machine tools with composite functions. Allow machine tool builders to find higher target markets and products that are more competitive.
For machine tool end users, CNC machine tools with combined machining technology, combined with the stability and ease of use of Zhongda Electric Control System, the production process will also be transformed from traditional decentralized production to advanced intensive production methods, product quality and The manufacturing cycle of parts will also have a leap of â€œqualityâ€ and â€œquantityâ€, thus creating greater benefits for it. Obviously, because the solution integrates a single-brand automation platform, the end user based on the CNC machine tool of Zhongda Electronics It is easy to obtain the economic and technical characteristics of the equipment life cycle total ownership benefit TB0 (Tota1Benefit 0f 0wnerShip).
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