Abstract: This paper describes the system composition, main technical parameters, and control scheme of a carton packaging machine, as well as the design scheme for the carton board supply process. Through analysis and research on the production process of the carton packaging machine in an automatic bottling line, a Siemens servo motion control system is applied to this equipment, communicating with all driven servos via a CAN fieldbus. The advantages of this control system are also explained.
0 Introduction
With the rapid development of packaging technology and the increasing number of packaging electronic equipment, the integrated packaging control system needs to exchange a large number of signals in real time. Traditional wiring harnesses are far from meeting this requirement. Therefore, more and more packaging systems are adopting Controller Area Networks (CAN). However, the CAN bus only defines the physical layer and data link layer in the Open Systems Interconnection (OSI) reference model. Generally, users must directly operate the data link layer using drivers, which cannot directly meet the configuration requirements of complex control networks and product interconnection. CANopen, as a truly open high-level CAN protocol, enables different CAN devices to communicate in a standardized way, making CAN devices interoperable. With the continuous improvement of the CANopen protocol, it has been widely used in many industries.
Heat shrink film packaging offers advantages such as safety, reliability, and ease of transportation and sales, and has been widely used in the domestic beverage industry. However, glass bottles used in beer production are easily damaged by impacts, and the limitations of heat shrink film cannot fully meet the production needs of the beer industry and other related glass bottle packaging industries. Therefore, cardboard box packaging is a high-end, high-specification packaging option for beverages and beer, easily solving the problems associated with long-distance transportation and effectively compensating for the shortcomings of heat shrink film packaging. The two complement each other and are indispensable packaging methods in the modern beverage and beer packaging industry. Previously, my country's cardboard box packaging machines had a packaging capacity of only 35 boxes/min, which could only meet the needs of beverage and beer packaging production lines with a capacity of 20,000 bottles/hour. This paper improves and upgrades existing carton packing machine technology, drawing on the characteristics of domestic and foreign carton packing machines, and successfully develops a fully automatic carton packaging machine with a production capacity of 60 boxes/min using a servo motion control system, effectively solving the production needs of the beverage and beer industry.
1. Technical structure and working principle of paper packaging machine
1.1 Composition of the control system
The R60 carton packaging machine from Keshimin uses a B&R (B&R) control system. The main control PLC is a CP476 that communicates with all drive servos via a CAN fieldbus. The host computer panel is a PP451, which is also connected via a CAN bus and uses an EX470 to expand remote I/O.
Figure 1. B&R control system diagram for carton packaging machine
Set the IP address of the PP451 host computer to 01; the CAN bus address of the 3IF771.9 communication card to 09; the CAN bus address of the bottle-tipping servo driver to 01; the CAN bus address of the bottle separator 1 servo driver to 02; the CAN fieldbus address of the bottle separator 2 servo driver to 03; the CAN bus address of the servo driver at the outlet to 04; the CAN bus address of the paperboard suction servo driver to 05; and the CAN bus address of the EX470 bus controller to C6.
The CAN bus address set on each device must be absolutely correct with the address set on the device; otherwise, the control system will not operate normally. Under normal circumstances, after the control system is powered on, the CAN communication indicator light of the IF771 will flash rapidly, and the two communication indicator lights on the AC110 communication card on each servo driver will remain constantly lit; otherwise, it indicates that communication is abnormal.
1.2 Composition and Working Principle of Automatic Carton Packaging Machine
Automatic carton packaging machines mainly consist of: bottle conveying, cardboard feeding, cardboard board picking, cardboard board conveying, bottle sorting, bottle pushing, carton folding and forming, sealing and gluing, and glue spraying.
The cardboard board supply system mainly consists of a cardboard board storage warehouse, a horizontal cardboard board conveyor, a cardboard board waiting station, a secondary cardboard board supply fork, a main cardboard board supply fork, and detection switches. Its main function is to supply cardboard boards to the packaging machine. For high-speed packaging machines, the cardboard board supply should be continuous to ensure a smoother supply.
Bottle conveying is mainly divided into two parts. One part uses a frequency converter to control the running speed of the motor, which transports the bottles on the conveyor line in a regular manner as required, and ensures a continuous supply of bottles through bottle shortage detection. The other part uses a main drive to drive the mechanical parts to convey the bottles according to the running speed of the main motor.
The cardboard picking mechanism is driven by a servo motor, which operates synchronously with the main shaft motor as a driven shaft. It is equipped with two sets of suction cups that alternately pick up the cardboard, achieving high-speed cardboard picking. Bottle sorting is controlled by the servo motors of bottle sorting units 1 and 2, as well as the main drive motor, sequentially dividing the bottles into groups of 3×4.
The cardboard conveying section transports the picked-up cardboard through several stations to the bottle loading position, powered by the main drive. The detection of double-layer cardboard and cardboard shortage is mainly used to ensure the supply of cardboard.
The main function of the bottle pusher section is to organize the bottles after they have been separated. The bottles are pushed over by the pusher bar, and when they pass over the unpowered transition plate, they are arranged closely together, thereby improving the quality of the packaging.
The packaging of beverages or beer is completed through folding, gluing, and sealing of cardboard boxes. The precise location for gluing is determined based on the box's structure, and the sealing process is adjusted accordingly to ensure sealing quality. Figure 2 shows the workflow diagram of the cardboard packaging machine.
Figure 2. Production Flow Chart of R60 Automatic Carton Packaging Machine
2 Control System Design
2.1 Main Controller
The main controller primarily controls analog signals, sensors, light sources, drives, positioning, pneumatics, process parameters, processes, operational faults, product quality, and safety. It employs a PLC (Programmable Logic Controller) and related auxiliary systems to achieve real-time and accurate control.
2.2 Multi-motor synchronization technology and servo technology
Packaging materials are conveyed via the main drive system, while auxiliary packaging materials are conveyed via a feeding system. Their interactions require coordination and consistent control. The multi-motor servo control system uses a PLC for control. Detection between different workstations is achieved through peripheral proximity switches, enabling contactless signal input and coordinated electrical, optical, mechanical, and pneumatic actions of the control system. By appropriately adjusting the positions of the bottle separator, sealing cylinder, glue spraying cylinder, and shaping cylinder, packaging of cartons of different sizes can be performed.
2.3 Operating System Design
By utilizing frequency conversion technology and a human-machine interface (HMI), the packaging equipment can be controlled to operate at different speeds in various working modes, including manual, automatic, and debugging modes. The frequency converter communicates via an RS-485 interface, allowing relevant parameters to be displayed and set on the HMI.
3 Control System Scheme
The automatic carton packaging machine control system mainly includes: a PP451 human-machine interface, an EX470 motion controller, detection elements, servo drivers, actuators, and servo motors. The EX470 motion controller controls the servo drivers via a CAN bus, enabling real-time control of the servo motors.
The machine's position detection and packaging cycle are both set via servo control. An encoder is mounted on one side of the servo motor, forming a closed-loop control system based on the pulse feedback signals from the rotary encoder. An incremental encoder is selected. Data is transmitted to the EX470 via the encoder interface, where the received data is processed to indicate the machine's actual operating position. During the carton packaging process, each push of a group of bottles by the bottle pusher completes one packaging cycle. A detection switch is installed on one side of the pusher's path, which resets the encoder data recorded by the EX470. In each packaging cycle, the position data for actions such as picking up cardboard, placing cardboard, and separating bottles are compared one-to-one with the encoder data in the EX470, and each machine action is controlled based on the compared data.
3.1 Bottle-dividing motor control system
The bottle-splitting motor drive involves the separate motors driving two sets of bottle-holding grippers. On the packaging machine, bottle transport in the packaging section is achieved via the main drive motor. Bottle sorting involves dividing closely spaced bottles into 3×4 groups or other sizes of combined bottles. Two sets of equally spaced bottle-holding grippers are installed on the conveyor chain of the two bottle-splitting motors, and the two motors alternate between fast and slow operation. The arranged bottles are divided into 3×4 groups, and then transported to the next station via the main motor.
Bottle-dividing motor control. Two bottle-dividing motors operate alternately in a regular pattern. The pulse count of the main motor is used as the synchronization control signal (X direction), and the pulse count of the bottle-dividing motor itself (Y direction) is used to run according to a pre-set motion trajectory. Only when the main motor is moving does the bottle-dividing motor, as a slave motor, run synchronously along a specific trajectory.
The setting of the synchronization parameters of the bottle-separating motor determines that the bottle-separating motor runs according to a specific pattern. There must be a reference position for the starting position of the operation, which can be set on the human-machine interface.
3.2 Cardboard Board Supply System
The cardboard board supply system mainly consists of two parts: vertical cardboard board supply and horizontal cardboard board supply.
The vertical board supply section is driven by a vertical supply motor. One motor drives one main support fork, and another motor drives a secondary support fork. The vertical board supply is primarily achieved through the motor-driven main support fork. When the supply of boards decreases to a certain quantity, the secondary support fork supports the remaining boards, and then the main support fork descends to the waiting position. Once the boards are lifted into position, the secondary support fork is withdrawn, and the main support fork resumes normal supply until a new set of boards is replenished.
A horizontal cardboard board supply device. The drive motor continuously monitors the real-time status of the cardboard board conveyor chain and controls the motor accordingly. Cardboard boards are transported from their initial stacking position to their waiting positions. Once the secondary fork lifts the cardboard board, the main fork moves downwards to its initial position, and then the motor moves the waiting cardboard board to the vertical workstation, completing one horizontal cardboard board supply cycle.
3.3 Composition and Control System of the Paperboard Picking System
The paper tray picking system consists of three main parts: a synchronous toothed belt, a drive shaft, and a driven shaft. Two sets of air suction cups are installed on the synchronous toothed belt. When the servo motor and the main drive motor move back and forth synchronously, the system achieves high-speed automatic paper tray picking.
The core of the cardboard tray control system is the control of the servo motor. The servo motor drives a synchronous toothed belt, on which are mounted two sets of suction cups for the cardboard tray picking action. When the servo motor rotates forward, the first set of suction cups releases the cardboard tray downwards when it reaches the cardboard placement position, while simultaneously the second set of suction cups moves to the suction position and picks up the cardboard tray, completing one cardboard tray picking cycle. When the servo motor rotates backwards, the second set of suction cups releases the cardboard tray downwards when it reaches the cardboard placement position, while simultaneously the first set of suction cups picks up the cardboard tray upwards when it reaches the suction position, completing one cardboard tray picking cycle.
3.4 Adhesive spraying control
Glue spraying control is also a major challenge of this machine. Within the 0-360 degree range, when cardboard is detected approaching the glue sprayer, the main shaft is activated by opening the glue spraying solenoid valve after rotating to a certain angle within that range. Once another angle is reached, the solenoid valve closes. Furthermore, due to the lag in the solenoid valve's action, different forward compensation values must be set for different production speeds.
4. Conclusion
The application of servo motion control systems in high-speed carton packaging machines makes the control system more precise, flexible, complete, reliable, and stable. The new generation of motion controllers has added many practical functions, reduced the programming difficulty for users, and truly demonstrates its advantages in machinery with high control requirements. Using servo motors not only effectively reduces the impact damage to equipment but also significantly reduces the equipment failure rate associated with traditional control methods.
