1 Introduction
This article describes the application of an intelligent servo driver and intelligent servo technology in fixed-length cutting. Different from the traditional pulse-based servo driver, it must rely on the pulse signal sent by the host computer to realize the motion control mode. The intelligent servo driver integrates the motion control, servo drive and PLC functions, and can realize the motion control without the upper computer motion controller. The function, together with the special functions built into the different application areas, is finally integrated into an "intelligent servo control drive" with a new generation of ideas. Figure 1 shows a comparison between a pulsed servo system and an intelligent servo system. It can be seen from the figure that the pulsed servo must rely on the pulse command sent by the PLC (or control card) to complete the motion control function. Since the intelligent servo has a built-in motion controller, motion control can be realized without using a host PLC, and the HMI touch screen can be directly connected.
"Intelligent servo control driver" is characterized by a complete "motion controller" function, but also a "servo driver", and both the functions of the PLC. This article will introduce intelligent servos based on the familiar application of 2-axis fixed-length cutting.
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Figure 1. Comparison of Pulse Servo and Intelligent Servo Systems
2. Basic working mode of fixed length cutting system
In each type of fixed-length servo control system, its application range is not limited to fixed length cutting. It also applies to other processes that require a fixed length and position. For example, food packaging, printing, punch feeding, pipe sawing or corrugated paper, cardboard cutting and steel plate cutting, etc., fixed length servo control system can be applied. In order to facilitate the description and easy comparison of differences in different systems, these systems with fixed-length cutting are collectively referred to as fixed-length cutting systems.
Defined from the design method of the cutting process, the fixed-length cutting system can be divided into three categories:
(1) stop feeding, static cutting;
(2) continuous feeding, reciprocating synchronous dynamic cutting;
(3) continuous feeding, rotary synchronous dynamic cutting;
Table 1 shows the different characteristics of the three fixed-length cutting systems. The system knife holder of the feed-discharging type is fixed, so the material to be cut at the moment of cutting and processing must be completely stopped, so it is called static cutting. The continuous feed type, whether it is reciprocating or rotary type, at the moment of cutting processing, the tool and material are operated synchronously, so it is called dynamic cutting and is also generally called flying shear.
Table 1. Comparison of different features of three types of fixed-length cutting systems
Action category
Tool holder design
Material Movement
Cutting method
Walk stop
Fixed
Batch feeding
Static cutting
Reciprocating
Straight reciprocating
Continuous feeding
Dynamic synchronous cutting
spiral
Circular rotation
Continuous feeding
Dynamic synchronous cutting
2.1 stop feeding, static cutting system
Feeding and stopping, static cutting system is one of the most common cutting methods, because its mechanical structure and control structure are the simplest compared with other cutting systems. As shown in FIG. 2 , when the motor is running, the material is fed by the feed wheel. When the feed length reaches a preset value, the motor stops feeding. After the material stops moving, the knife action divides the material into finished products of the same length.
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Figure 2. Walk-and-go feeding, static fixed-length cutting system architecture
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Figure 3. Speed ​​curve of stop feed system
The defects of the walk-in fixed-length feeding system:
a) It is impossible to cut the finished product of continuous feed
When continuous cutting is required (as shown in Fig. 2), there must be a LOOP buffer in the front section of the feed clamp wheel, which on the one hand increases the volume of the machine; on the other hand, it cannot handle the continuous output from the front section. Materials, such as extruder production lines for hard-tube hose profiled materials, twill paper tube production lines, and seamless steel pipe production lines, etc., are manufactured continuously and continuously, and cannot be statically cut after stopping.
b) easy to damage the material
If the plastic bag material is very thin, rapid feeding will cause the material to be stretched and deformed; if the surface of the mirror plate is very delicate, the acceleration and deceleration of the pinch wheel will scratch the finished product.
c) Limit of feed rate
For the same cutting length, when the feed rate is to be doubled, the motor needs several times the torque, and it is easy to reach the limit of the system according to the characteristics of the motor.
2.2 Continuous feeding, reciprocating synchronous dynamic cutting
At the end of a continuous production line, the finished product is continuously produced. If the finished product is a soft material (such as wire, plastic film), the product can be taken up and taken up by winding. However, if the finished product is a rigid material (such as a PVC hard tube extruder), the continuous material must be immediately cut into a fixed length of finished product. At this time, it is necessary to apply the technique of "reciprocating synchronous dynamic cutting" or "reciprocating flying shear." Because in the process of cutting, if there is a mutual positional change between the hard material and the tool, it will cause damage to the tool; at the same time, it will also affect the quality of the finished product.
The "reciprocating flying shear" mechanical structure shown in Figure 4 is the best solution to this problem. The cutting tool of this mechanical structure is not disposed at a fixed point but is mounted on a movable "cutting table". Through the screw, the position of the "cutting table" is driven by the servo motor. Therefore, during the entire cutting process, the controller can control the speed and the position of the cutting table at any time, so that the relative position of the tool and the material can always be kept constant. Using this method can ensure each product's fixed-length accuracy and notch flatness, while also extending the life of the tool.
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Figure 4. System architecture for reciprocating synchronous dynamic cutting
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Figure 5. Speed ​​curve of a reciprocating synchronous dynamic cutting system
2.3 Continuous feed, rotary synchronous dynamic cutting
FIG. 6 is a schematic diagram of a rotary synchronous dynamic cut (fly shear). Note that the upper and lower cutting cutter wheels are simultaneously driven by the servo motor and each rotates in the direction indicated by the arrow. The blade above the cutter wheel must be precisely adjusted so that when the blade of the upper cutter wheel rotates directly below, the lower blade just turns directly above. Only in this way can correct cutting be performed. Each time the cutter wheel rotates one revolution, the material is automatically cut once; if the motor is continuously operated in the same direction, the cutter wheel can be continuously cut. Therefore, the cutting efficiency is better than "reciprocating."
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Figure 6. Rotary synchronous dynamic cropping system architecture
It should be noted that in the rotary and reciprocating synchronous dynamic cutting systems, a mechanism is needed to coordinate the movement speed between the master axis and the slave axis (ie, the feed axis and the cutter axis) to realize the feeding and smooth cutting. , namely electronic cam. In the pulsed servo system, the function of this electronic cam is usually realized by the PLC, which not only affects the response speed of the system, but also increases the investment cost and maintenance cost of the system.
3. iDrive intelligent servo driver
iDrive intelligent servo driver is an intelligent driver product of Beijing Sinotrust Intellectual Property. Compared with pulse-based driver products, iDrive intelligent servo driver has the following features:
(1) Higher reliability
iDrive integrates motion control, motor drive and integrated PLC functions. The integrated structure not only reduces the number of connecting cables, but also helps improve system reliability while reducing the impact of outside interference on the system.
(2) Greater flexibility
iDrive has a rich operating mode: RS232 network mode, RS485 network mode, pulse mode, analog signal mode and independent operation mode; iDrive can be used to drive a variety of different motors: DC brushless (brushed) servo motor, AC servo motor And linear motor; iDrive also integrates 18 points of input / output, can be controlled by the host computer input / output port status.
(3) Save more potential
In the RS485 network operation mode, an RS485 bus can connect up to 31 iDrive drives at the same time, which simplifies the connection of the system and can save a lot of costs in installation and maintenance. The iDrive's independent operation mode can be used to build a hostless PC. Controller's motion control system reduces system cost;
(4) Faster dynamic response
The integrated structure of the controller and driver ensures a high sampling and control frequency of each control loop, and the higher sampling and control frequency ensure a high dynamic response of the system. It can guarantee the control precision of the system under high-speed motion.
4. Application of iDrive Dual-axis Intelligent Servo Driver in Fixed-length Cutting
iDrive is a dual-axis intelligent servo driver integrated with motion control, servo drive and PLC. Due to the built-in motion control function, the electronic gear and electronic cam can be built into the drive. With the communication function of the intelligent servo driver, it can communicate with the host computer such as the HMI directly. These characteristics all determine the iDrive two-axis intelligent servo driver has a very big advantage in the fixed-length cutting field. The reciprocating synchronous dynamic cutting and rotary synchronous dynamic cutting are used as examples to illustrate the application of iDrive two axes in the field of dynamic cutting.
Figure 7 shows the interface diagram of the iDrive two-axis intelligent servo driver. The two-axis module is suitable for applications in the fixed-length cutting field. The integrated PLC function can connect up to 18 input/outputs and interfaces.
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Figure 7. Dual-axis iDrive active/slave axis setup
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Figure 8. iDrive applied to a reciprocating synchronous dynamic cutting system
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Figure 9. System architecture for rotary synchronous dynamic cropping
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Figure 10. iDrive connects the second encoder
Fig. 8 and Fig. 9 show iDrive applied to the dynamic fixed-length cutting system. Because iDrive dual-axis intelligent servo driver integrates the functions of motion control and PLC, the speed control function of fixed length cutting can be realized without PLC. iDrive has built-in electronic cam functionality. The iDrive integrated network function can be directly connected with a touch screen or text editor to perform system parameter modification and system operation status display. Because the iDrive dual-axis intelligent servo driver has built-in electronic cam functions, the system responds extremely quickly, which ensures the dynamic performance of the system, and the direct connection with the touch screen also increases the convenience of system construction.
iDrive can connect to the second encoder through the I/O port to achieve the fixed-length cutting function, as shown in Figure 10.
In addition, in some cost-sensitive application areas, we can even remove the touch screen and directly use the state of the iDrive's I/O port to control whether the system is running or stopped, which has great cost advantages.
5. Conclusion
Using iDrive to build a dynamic fixed-length cutting system has the following advantages:
(1) The system is simple and compact.
Because iDrive has built-in electronic cam and color mark capture and compensation functions, and the intelligent driver can be directly connected to the HMI, the system is more concise and convenient to set up.
(2) Significant price advantage and performance advantage Since the electronic cam function is built into the iDrive, the cam function of the system does not need to be performed by the upper PLC, and the synchronization and following functions are realized directly at the driver stage, and the response speed and control accuracy of the system are achieved. Have a significant increase. The original PLC can directly omit or select a PLC with a smaller function, so as to achieve the purpose of saving investment.
With the increasingly fierce market competition, the pressure on the machinery manufacturing industry is not small. In order to enhance the competitiveness, we can only continue to develop new markets by constantly developing and improving the performance of our products. In China, the stop-and-go control system has begun to be generally transformed, and the automatic two-stage speed control system has been gradually replaced by the automatic fixed-length stop-and-go control system. Because the difficulty of the flying shear control system is relatively high, most of the reciprocating cutting machines still use the hydraulic system to cut the table. The rotary cutting machine also mostly uses the cam coupling cutter. Therefore, the synchronization, control, and cutting accuracy of the crop tracking need to be further improved.
The emergence of intelligent fixed-length control drivers immediately simplifies the design of flying shear control systems and reduces manufacturing costs. After the obstacles that had caused the industry's obstruction to disappear, everyone now has the basis for competition with Europe, the United States, and Japan. It is believed that soon, both reciprocating and rotary cutting machines will gradually evolve into high-performance electronically controlled flying shear systems under the joint efforts of domestic companies.
The control system of multi-axis servo pillow packaging machine based on China's independent intellectual property intelligent servo technology adopts bus control architecture, built-in motion controller, built-in electronic cam, multi-axis synchronous flying shear, multi-axis follow-up, real-time compensation of high-speed color standard , Built-in PLC to complete I / O function, all the motion control is completed in the servo driver level, the system response is quick, simple structure, scalability, can be widely used in multi-axial pillow packaging machine, and low cost, cost savings over imported products More than 50% will gradually become the mainstream solution for the pillow packaging industry control system.