[Abstract] This article mainly introduces the successful application of Delta's high-response, high-resolution network A2 servo, which integrates servo amplifier and motion controller, in a vertical packaging machine. The built-in electronic cam function of the A2 servo makes it easy to establish the flying shear curve. The use of high-speed capture, high-speed comparison, color mark masking function and automatic correction function has raised the packaging speed and cutting accuracy to a new level.
【Abstract】 This article mainly introduces the successful application in packing machine of a network type servo motor ─ Delta A2 ,which is of high response, high resolution and function as servo driver and MC controller. With a built-in function of electronic cam allows the establishment of the shear curve easily. Furthermore, with the usage of high speed capture, high speed comparion, color code cover function and auto skew adjustment function make a new progress in packing speed and cutting precision.
[Keywords] Built-in electronic cam; high-speed capture; high-speed comparison; color mark masking; automatic correction; A2 servo
1. Introduction to Packaging Machines
1.1 Classification of Packaging Machines
In recent years, with the continuous development of the national economy and the improvement of people's living standards, the public's demand for products in industries such as food, medicine, and daily necessities has been increasing. Traditional manual packaging operations are no longer sufficient to meet market demand, necessitating the search for equipment that automates production and improves efficiency. This has given rise to high-quality, high-performance fully automatic packaging machines. Packaging machinery can be broadly divided into vertical packaging machines (as shown in Figure 1) and pillow packaging machines. Vertical packaging is suitable for liquids, powders, and granules with good flowability. It mainly relies on its own weight, supplemented by mechanical action when necessary, to complete the packaging. Vertical packaging machines generally have two packaging functions: cursor cutting and fixed-length cutting. These two cutting functions are easily switchable. The packaging method used during machine operation depends on the packaging film, which is generally divided into those with and without a cursor. Films without a cursor are cut to fixed length, while those with a cursor are cut. Pillow packaging is mainly suitable for packaging single or combined items with regular shapes and sufficient rigidity.
Figure 1 Vertical Packaging Machine
1.2 Working Principle of Vertical Packaging Machine
A vertical packaging machine is a machine that automatically and continuously completes three functions: forming a roll of flexible packaging material into a bag, filling it with material, and sealing it. Its working principle is as follows: The roll of film placed on a support device is wound around a guide roller assembly and a tensioning device. After the position of the trademark pattern on the packaging material is detected by a photoelectric detection and control device, it is rolled into a film cylinder by a collar forming device and wrapped around the surface of the filling tube. First, a longitudinal heat sealer longitudinally heat seals the joint area of the rolled cylinder to obtain a sealed tube. Then, the cylindrical film moves to the transverse heat sealer for transverse sealing, forming a packaging bag. The metering device fills the measured items into the packaging bag through the upper filling tube, and then the transverse heat sealer heats and cuts it in the middle to form a packaging bag unit, simultaneously forming the bottom seal of the next tube bag.
1.3 Production Process of Vertical Packaging Machine
Vertical packaging machines, used in conjunction with metering and filling equipment, are commonly used for packaging block, flake, granular, stem, powder, and liquid and semi-fluid materials. A key feature is that the material feed cylinder is located inside the bag maker, with bag making and filling occurring vertically from top to bottom. It mainly consists of a metering device, transmission system, horizontal and vertical sealing devices, collar forming device, filling tube, and film pulling and feeding mechanism.
2. Main Functions of the Equipment
2.1 Film feeding device
It mainly consists of a film feeding roller and a film feeding shaft. Its main function is to deliver the packaging film flat and evenly to the collar forming machine. In this device, the film feeding shaft and the longitudinal sealing shaft share a servo, and are driven by a chain.
2.2 Color mark sensor
Color mark sensors are commonly used to detect specific color marks or spots on objects. They detect color marks by comparing them with non-color mark areas, rather than directly measuring the color. A color mark sensor is essentially a reverse-biased device: the light source is mounted perpendicular to the target object, while the receiver is mounted at an acute angle to the object. This allows the sensor to detect only scattered light from the target object, avoiding direct reception of reflected light and enabling a very narrow beam focus.
2.3 Collar Forming Machine
Circular collar forming machines are mainly used in packaging machinery and are core components of vertical automatic packaging machines. The plastic film used for packaging is automatically rolled into a cylindrical shape by the collar forming machine. During the rolling process, the plastic film should not undergo longitudinal or transverse stretching deformation, and the frictional resistance as the plastic film passes through the forming machine should be minimal. This requires that the purchased forming machine conforms to the natural curling deformation of the plastic film, meaning the surface area of the forming machine is equal to the total area of the plastic film passing through it.
2.4 Heat sealing knife
To be precise, the term "heat sealing knife" isn't accurate; it should be "heating plate." Heating plates are made of alloy materials, including chrome alloys and iron-chrome alloys. They come in five widths: 3mm, 5mm, 8mm, 10mm, and 12mm. The silicone sealing strip is used to create a smooth, tight seal and to emboss the surface; the embossed shape is the strip's own texture. Most use a fine mesh pattern.
Control scheme principle of 3 vertical packaging machines
The vertical packaging machine uses the longitudinal sealing shaft (which is also the film feeding shaft) as the main shaft of the system. The horizontal sealing, scribing, and cutting axes follow the main shaft. The servo controllers for horizontal sealing, scribing, and cutting directly capture the film position color mark signal for position detection. After the film is formed by the forming device into a cylindrical film, it undergoes longitudinal heat sealing. As the packaging film moves downwards, the horizontal sealing shaft operates, and the material is simultaneously fed into the cylindrical film, continuing to move downwards together. When the next cursor signal arrives, the horizontal sealing shaft operates again, completing the three heat sealing actions for one package. As the packaging film continues to move downwards, the color mark sensor detects the color mark. Upon receiving the signal from the color mark sensor, the driver operates, scribbling a serrated cut at the cursor position, completing the scribing action. When the host computer (PLC) counts to 5, it sends a signal to the cutting axis servo, enabling the cutting axis servo to receive the signal from the color mark sensor. Upon receiving the signal from the color mark sensor, the cutting axis servo operates, completing the packaging of five consecutive packages. This system includes a PLC, HMI, servo and temperature control module. Since the Delta ASDA-A2 servo controller has an electronic cam function, four servos can complete the film feeding, material feeding and cutting process. The PLC only needs to perform simple I/O control, which greatly saves the expensive cost of the host computer and makes program planning simpler.
Functions of each axis
4.1 Film feeding shaft
This axis uses speed control and serves as the main axis of the entire system. It issues pulse commands to the horizontal sealing axis, scribing axis, and cutting axis to direct the camshaft's operation.
4.2 Horizontal sealing shaft
In the PR (Internal Position Control Mode) control mode of the A2 servo, the built-in electronic cam follows the main shaft. The horizontal sealing shaft receives pulse differential signals OA/OA and OB/OB from the film feeding main shaft and moves along the pre-programmed cam flying shear curve. When the horizontal sealing shaft servo controller detects the color mark photoelectric signal (DI7 has a signal input), the cam engages and operates. During operation, the servo controller captures the color mark signal and uses the built-in synchronous capture correction axis (color mark compensation function) to adjust the cam speed and automatically correct the cutting position to ensure accurate cutting.
4.3 Marking axis
Like the horizontal sealing shaft, this shaft is in PR (internal position control mode) control mode. It uses a built-in electronic cam to follow the main shaft and receives differential pulse signals from the main shaft. Its function is to cut the packaging film with dotted lines or serrated shapes, making it easier to tear or open individual packages.
4.4 Cut-off shaft
This shaft, like the horizontal sealing shaft, is in PR (internal position control mode) control mode. It uses a built-in electronic cam to follow the main shaft and receives differential pulse signals from the main shaft. Its function is to cut the packaging at the cutting position. According to customer requirements, it can cut multiple packages in a row, and can cut 1 to 10 packages in a row.
5. Cam Curve Planning
The Delta ASD-A2 servo has a built-in PR (Internal Position Control Mode) mode. In PR mode, it has a built-in 64-segment positioning program, which can not only realize origin return, position control, and constant speed control, but also has position and speed insertion and overlap functions, parameter writing, and jumping and calling between positioning program segments. It also has electronic cam function, high-speed capture and compare functions, and origin return of the horizontal sealing axis, scribing axis and cutting axis can be completed without the participation of the host computer.
6. Establishment of Cam Curve
The Delta ASDA-A2 servo controller features a built-in flying shear cam model, making the creation of flying shear electronic cam curves simple and easy. The ASDA-A2 PC software supports various flying shear curves, including automatic flying shear, automatic flying shear (synchronization zone), and automatic flying shear (adjustable synchronization zone), and will automatically generate flying shear curves. Considering the varying degrees of difficulty in heat-sealing different packaging films, a synchronization zone is established in the cutting area.
7. A2 servo's unique synchronous gripping correction axis function
The A2 servo controller has a built-in synchronous grasping correction axis function (i.e., the traditional color mark automatic compensation function). The servo controller uses the built-in high-speed pulse grasping function to grasp the number of pulses between two color marks on the active axis through color mark photoelectric grasping. It compares the number of pulses with the theoretical cutting amount set by the user inside the servo controller (the setting value of P5-78) through the compare function. Based on the synchronous correction correction rate (P5-80), the error value (P5-79) between the two is corrected. The servo controller finally runs according to the corrected pulse command (P5-77).
8. Cover-up function
The A2 servo controller has a built-in color mark masking function, which can effectively avoid photoelectric malfunctions caused by packaging film contamination and misprinted color marks, thus increasing the stability of the entire system. P5-78 is the pulse setting value for the cutting length, and P5-96 is the pulse length for the masking area. After this function is set, even if the color mark malfunctions within the masking area, it will not affect the performance of the entire system.
9 Conclusion
The successful application of Delta's A2 servo motor in vertical packaging demonstrates that Delta has a successful solution in the vertical packaging machine industry, which has the following characteristics:
(1) The cutting speed reaches 180 packs/minute when the bag length is 80mm, with an error accuracy of ±0.3mm;
(2) It can produce 1 to 10 consecutive packages to meet the special needs of customers;
(3) The entire cutting process is automatically completed by the servo, and the PLC only performs simple logic control, which greatly reduces the difficulty and cost burden of the host computer control.
(4) The cutting uses the electronic cam function unique to A2. Compared with mechanical cam, it has the advantages of being simple, wear-free, easy to maintain, and convenient to change curves, which greatly reduces the maintenance cost of subsequent equipment.
(5) The use of A2’s unique automatic synchronization correction function and color mark masking function makes the equipment more stable and easier to operate.
