Automatic control system

Fertilizer packaging usually uses an automatic quantitative packaging machine, which can accurately package fertilizers of different types and specifications. It is usually composed of a weighing system, a feeding mechanism and a packaging mechanism, a bag sewing machine, and a folding machine. The weighing system ensures that the fertilizer weight is accurately measured, the feeding mechanism transports the fertilizer to the packaging position, and the packaging mechanism completes the bagging and sealing operations. In addition, some packaging production lines may also be equipped with conveyor belts and palletizers to achieve seamless connection of the entire packaging process.

When choosing a fertilizer granule packaging machine, it is necessary to closely consider the type, characteristics and production needs of the fertilizer.

1. The output requirements directly determine the specifications and models of the packaging machine. Large-scale production lines need to choose high-speed packaging machines such as the DCS-50 model with a capacity of 1,200 packages per hour. If it exceeds this limit, two machines are required; small-scale production below 1,200 packages per hour can be equipped with one machine.

2. Different types of fertilizers correspond to different packaging requirements. For example, granular fertilizers such as urea and potassium sulfate have relatively regular particles, good fluidity, and are easy to package; while organic fertilizers, BB fertilizers, etc. have uneven particle sizes and may be sticky and have poor fluidity. This requires the packaging machine's feeding system to be larger or equipped with a stirring and arch-breaking device to prevent blockage.

3. In terms of particle size, small-particle fertilizers require the packaging machine's metering device to have higher precision, so a servo motor-controlled weighing system must be used, while large-particle fertilizers do not require so much and can use an ordinary cylinder + weighing double-cylinder packaging scale.

4. In terms of material selection, since most fertilizers are corrosive, the parts of the packaging machine that come into contact with the materials, such as the hopper, feeder, weighing platform, etc., should be made of corrosion-resistant 304 stainless steel. However, if the fertilizer has been coated or the customer has a limited budget, carbon steel can be used.

First, the finished fertilizer is fed into the packaging scale silo by a bucket elevator or belt conveyor and other feeding devices. Then, in the main body of the scale, the weighing sensor converts the weight of the material in the scale bucket into an electrical signal and transmits it to the control system.

The control system calculates the deviation based on the preset weight and real-time weighing data through PID and other control algorithms, sends a pulse signal to the servo motor driver, accurately adjusts the servo motor speed and angle, controls the feeding speed and amount of the gate-type pneumatic feeding mechanism, and realizes fast feeding, slow feeding and precise stopping to ensure metering accuracy.

After weighing, the bag clamping device is released, the material falls into the packaging bag below, the conveyor belt starts, and the packaging bag is transported to the folding machine. The folding machine is driven by the servo motor and folds the excess part of the bag mouth neatly through the mechanical transmission structure; then, the packaging bag is sent to the sewing machine.

The sewing head of the sewing machine is driven by the servo motor to drive the needle and shuttle to move together. The suture passes through the bag mouth material to form a stitch to complete the stitching. At the same time, the feeding mechanism is controlled by the servo motor to pull the packaging bag forward at a stable speed to ensure uniform stitches. The packaged finished products are then transported to the palletizing area by conveyor belts.

So there are two types of packaging machine Dpuble cylinder packing machine and servo-motor packaging machine, the capacity are as follows:

Double cylinder packing scale: The packaging speed of the double cylinder scale is relatively moderate. If it is used for conventional fertilizer packaging, the packaging specifications are 25-50 kg per bag, and it can pack about 500-600 bags per hour. This is because the double cylinder scale controls the feeding and weighing process through the action of the cylinder. The operating speed and response time of the cylinder are limited. In the continuous packaging process, it takes a certain amount of time to complete the cylinder filling and deflation from one packaging cycle to the next cycle.

Servo motor packaging machine: The packaging speed of the servo motor scale is usually faster than that of the double cylinder scale. For the same fertilizer bag of 25-50 kg, the servo motor scale can pack about 800-1000 bags per hour. This is because the servo motor has the characteristics of high precision, fast response and precise control. It can perform feeding operations more quickly according to the instructions of the control system, and can accurately adjust the feeding speed at different packaging stages, reducing the waiting time and errors in the packaging process, thereby improving the overall packaging efficiency. Tongli's servo scale packaging speed exceeds the average number of bags of its peers by 20%, reaching 1000~1200 bags per hour, and the highest record is 1400 bags per hour.

The automatic bagging machine for fertilizer is a machine used to replace the manual bagging process. Ordinary fertilizer packaging requires manual bagging into the bag clamping mechanism, while the automatic bagging machine automatically completes the process of grabbing and bagging through a suction cup.

It consists of a feeding mechanism, a bagging mechanism, a weighing mechanism, a sealing mechanism, etc. During operation, the fertilizer is first transported to the designated location through the feeding mechanism, and the general feeding speed can reach 1,000 bags per hour.

The bagging mechanism automatically takes out the bag from the bag library and puts it on the outlet. Then, the fertilizer enters the bag. During this process, the weighing mechanism accurately controls the amount of fertilizer loaded, and the common weighing accuracy can reach ±0.5 g or even higher.

Finally, the sealing mechanism seals the bag filled with fertilizer, with a fast sealing speed and good sealing effect, which can effectively prevent fertilizer leakage. Its packaging quality is stable, which can ensure that the fertilizer weight of each bag is uniform and the seal is firm and beautiful.

The fertilizer bag sewing machine is a commonly used equipment in the fertilizer production and packaging process. In layman's terms, it is a sewing machine tied to a pillar. It is mainly composed of a machine head, a machine base and a control system. It drives the needle up and down through the motor, and the shuttle rotates in coordination, so that the suture passes through the fertilizer packaging bag material to form a firm stitch. At the same time, the feeding mechanism transports the packaging bag at a uniform speed to ensure uniform stitches. It has the advantages of fast sewing speed and adaptability to a variety of packaging bag materials, and is widely used in compound fertilizer packaging lines.

The 25-50 kg fertilizer semi-automatic packaging machine is a device used to package fertilizers with a weight range of 25 to 50 kg. It is mainly composed of components such as a weighing mechanism, a conveying system, and a sealing device.

The main difference between this semi-automatic packaging machine and a fully automatic packaging machine is that the semi-automatic packaging machine requires manual bagging. The fully automatic packaging machine can automatically take bags from the bag library and put them on the discharge port, and the entire packaging process can be completed without manual intervention.

Since the semi-automatic packaging machine requires manual bagging, it is called "semi-automatic". This packaging machine is suitable for some small and medium-sized fertilizer production enterprises or workshops with relatively low output requirements, because it can save a certain amount of equipment investment cost while meeting basic packaging needs.

However, compared with fully automatic packaging, it also has certain advantages, that is, it can adapt to flexible production plans, such as changing from 25kg to 50kg or other specifications at any time, while the fully automatic bagging system requires complex debugging to do so.

The cost of a packing machine depends on the scope of supply, for example for a complete semi-automatic packaging line the cost are as follows:
1. Bucket elevator: 10,000 USD
2. Stainless steel semi-automatic packing machine: 18,000 USD
3. Sewing machine: 3000 USD
4. folding machine: 2000 USD
5. Electric control system: 3000 USD
6. On-site fabrication like platform and silo are not included.
Therefore the total for a semi-automatic packaging machine is around 27,000 USD

The main difference between fertilizer packaging machines and bagging machines lies in the manual bagging.

1. Fertilizer bagging machines are usually highly automated equipment that can automatically complete a series of packaging processes from fertilizer metering, transportation to bagging and sealing. There is no need for manual bagging, and continuous and efficient packaging operations can be achieved. However, the disadvantage is that switching between bags of different specifications is very time-consuming because it requires program control.

2. Fertilizer packaging machines generally require manual bagging at designated locations, and then the machine completes the operation of putting fertilizer into bags. It has a relatively low degree of automation and mainly focuses on the bagging function of fertilizers. It usually needs to cooperate with other equipment to complete the complete fertilizer packaging process, but the advantage is that it is low in cost, can be suitable for flexible production plans, and can change the packaging size at any time.

The traditional double-cylinder compound fertilizer packaging scale is a device used for compound fertilizer packaging. It is mainly composed of two weighing cylinders, a feeding device, a weighing sensor, a control system and other parts. Through the cooperation of the two cylinders, the functions of rough weighing and fine weighing can be realized.

First, one cylinder feeds a large amount of material quickly, and when it is close to the target weight, the other cylinder feeds a small amount accurately, thereby ensuring the accuracy of weighing. The double-cylinder scale realizes rough weighing and fine weighing through the cooperation of the two cylinders. It may take a certain amount of time in the conversion process, and the overall packaging speed is relatively slow.

However, if the production scale is small and the packaging speed requirement is not particularly high, the double-cylinder scale can also meet the production needs, and its structure is relatively simple, and it is easy to operate and maintain. It is widely used in some small and medium-sized enterprises.

The servo motor packaging scale is a packaging weighing device that uses a servo motor to drive the feeding mechanism. It uses the servo motor to accurately control the feeding amount of the material and control the weighing error within a very small range. It is especially suitable for packaging materials with extremely high weight accuracy requirements.

Faster packaging speed: The servo motor has a fast response speed, can quickly complete the material feeding action, and can reach a stable operating state in a short time, which is suitable for large-scale compound fertilizer production lines such as 40t per hour.

Better flexibility: The feeding parameters of the servo motor packaging scale can be easily adjusted through programming, and can quickly adapt to changes in different materials and different packaging specifications without complex mechanical adjustments, which greatly shortens the debugging time of the equipment.

Good operating stability: The servo motor runs smoothly, with low noise and low vibration, which reduces the impact on the weighing accuracy caused by unstable equipment operation, and also reduces the probability of equipment failure.

High degree of automation: It can be seamlessly connected with other automated packaging equipment to form a highly automated packaging production line, realizing fully automated operation of a series of packaging processes such as material conveying, weighing, packaging, and sealing, reducing manual intervention, and improving production efficiency and product quality consistency.

The packaging machines in the compound fertilizer production line can be divided into five categories: gravity packaging machine, double cylinder packing machine, servo motor packaging machine, belt packaging machine, and combined packaging machine.

1. Gravity packaging scale: Automatic weighing and packaging based on material gravity. When working, the material flows from the storage bin through the feeding device into the weighing bucket under the action of gravity. When the weighing sensor detects that the weight reaches the set value, the feeding device is closed, and then the material falls into the packaging bag. This type of packaging scale has a simple structure and low cost. It is suitable for compound fertilizer particles with good fluidity, but its accuracy is generally ±0.5% - ±1%, and the packaging speed is about 50 - 120 bags per hour. It is suitable for small production enterprises or scenes with low precision requirements. Due to the lack of precise feeding control, when handling sticky and easy-to-cake materials, it is easy to exceed or under-tolerance.

2. Double-cylinder compound fertilizer packaging scale: It uses double cylinders to work together. Usually one cylinder is responsible for fast and large-scale coarse feeding (up to 80%-90% of the set weight), and the other cylinder is slow and precise fine feeding. Real-time monitoring is performed through weighing sensors (common accuracy is 0.1 level, and the range is set according to the packaging specifications), and the feeding amount is adjusted in combination with a PLC control system. Its weighing accuracy can reach ±0.2% - ±0.3%, and 100 - 200 bags can be packaged per hour. The scale has a stable structure and strong anti-interference ability. It can adapt to compound fertilizers of different particle sizes and fluidity. It is not demanding on the environment, but the mechanical structure is relatively complex. The maintenance cycle is about 3 - 6 months, and the cylinder sealing and sensor stability need to be checked regularly.

3. Servo motor packaging machine: With the servo motor as the core drive unit, the precise movement of the feeding mechanism is achieved through high-precision encoder feedback control. With the help of digital control systems (such as PID algorithms), the weighing error can be controlled within ±0.1%, and the packaging speed can reach 200 - 300 bags per hour. The equipment can quickly adjust the feeding speed and time according to the material characteristics (such as particle size and fluidity). For example, a slow feeding can be set for large particles, and a high-speed feeding strategy can be adopted for small particles. The response time of the servo motor is less than 50ms, the positioning accuracy is ±0.01mm, the degree of automation is high, and it can be seamlessly connected to the MES system, but the equipment cost is 30% - 50% higher than that of the double-cylinder scale.

4. Belt packaging machine: Based on the principle of dynamic weighing, it consists of a belt conveyor, a weighing bridge, a weighing sensor and a speed measuring unit. During the uniform conveying of the material on the belt, the weighing sensor detects the weight of the material on the belt in real time, calculates the instantaneous flow rate in combination with the speed measuring unit, and adjusts the feeding speed through PID control to achieve continuous quantitative packaging. Its packaging speed can reach 300 - 500 bags per hour, which is suitable for large-scale production scenarios, but the accuracy is relatively low, generally ±0.5% - ±1%. The equipment has high requirements for belt tension and material distribution uniformity, and the speed encoder and weighing sensor need to be calibrated regularly to ensure long-term stability.

5. Combination scale: Integrates multiple independent weighing units (commonly 8 - 16 heads), and uses computer algorithms to optimally combine the weight of each unit material. The system can complete data collection and calculation within milliseconds, automatically select the combination with the weight closest to the target value, and the weighing accuracy is ±0.1% - ±0.2%. The packaging speed can reach up to 600 bags per hour. The scale can adapt to compound fertilizer particles with irregular shapes and large size differences, and reduce the superposition of single unit errors through dynamic combination. However, the equipment is highly complex, and the weighing unit sensor and vibrating feeder need to be maintained regularly. The debugging process relies on professional algorithm optimization, and the initial investment cost is about 2-3 times that of a double-cylinder scale.