Talking about the status and development trend of domestic quantitative packaging scales
This article briefly describes the current status of the domestic quantitative packaging industry and the weighing methods, feeding devices, and control methods commonly used in quantitative packaging scales, and briefly discusses the development trend.
The production of quantitative packaging equipment by Chinese enterprises started relatively late. After more than 20 years of development, the development of quantitative packaging equipment industry in China has begun to emerge, which can not only meet the needs of the domestic market, but also export some. In recent years, domestic companies have followed the trend of economic development in developed countries and China. While trying to learn from international advanced technology experience, they have emphasized independent knowledge innovation and developed high-precision, high-speed, high-quality internationally competitive high-tech products. . Contributing to the stable and sustainable development of China's quantitative packaging equipment, catching up with the United States, Japan, Germany, Italy and other four leading countries in the production of quantitative packaging equipment. Strive for a wider world in the increasingly fierce international competition, and actively enter the European, American, and Japanese markets to win a place.
1. Status of quantitative packaging industry
China's quantitative scale production enterprises are mainly small-scale, with weak product design, research, and development links. China's quantitative packaging industry has been in a state of low productivity and low main technology for a long time. Most enterprises are still in the original business stage of copying domestic and foreign technologies to reduce production costs. Some workshop-type small businesses survived with a set of drawings, blindly pursuing low costs, and severely disrupted the domestic market. Enterprises do not have independent intellectual property rights, especially the core control technology. The controller is the brain of quantitative packaging machinery. However, most enterprises need to buy from foreign countries or joint ventures or wholly-owned units. At present, China's quantitative packaging equipment has entered a new period of adjusting product structure and improving development capabilities. Technology upgrades and product replacements are important topics for the development of the industry. The low-level development of quantitative packaging machinery will affect the rapid development of the entire quantitative packaging industry, so efforts must be made to change its backward situation. Fight for bigger domestic and international markets.
1.1 Basic Structure
Quantitative packaging scales can generally be divided into bucket (net weight) scales and non-bucket (gross weight) scales according to the weighing method.
When working with a bucket scale, the material to be weighed is added to the weighing bucket equipped with a load cell through a feeding device for weight measurement. The load bearing device with the bucket scale is the weighing bucket, and the shutter installed at the bottom of the weighing bucket is the unloading device of the quantitative packaging scale system. The weighing bucket can adopt a structure in which one or two pairs of shutters are arranged at the bottom of the square weighing bucket, and the valve is used to drive the valve to discharge. Bucket scales have high weighing accuracy, fast packaging speed, and can form a dual scale (and above) system, which greatly improves packaging speed.
The structure of the bucketless scale eliminates the need for weighing scale components. The load cell is directly installed on the lower hopper and the bag clamping device. During work, the material is directly placed in the pocket clamped on the bag clamping mechanism for weighing. Because the bucket-less scale omits the scale bucket components, the height of the scale body is greatly reduced, and it is suitable for low occasions at the packaging site. However, due to the inconsistency of the weight of the packaging material (bag), the tare change of the weighing unit must be measured every weighing cycle when the bucketless scale system is in operation. Therefore, before each weighing cycle, the computer's weighing control instrument must automatically "tare". Because "tare" takes several seconds, the packaging speed of the bucketless scale is affected to some extent.
Basic structure of quantitative packing scale is composed of storage silo, feeding device, bearing mechanism, filling device and other components.
The feeding device has many structural forms, mainly including: electromagnetic (motor) vibration type, gravity (valve or insert plate) type, spiral (auger) propulsion type, belt conveying type, high-current feeding, etc. A part of Figure 1 can also be used in combination with each other according to the characteristics of the materials. By taking corresponding measures on various feeding structures, a thickness and thickness combination that meets the requirements can be generated. Using different speeds of auger or belt motor.
Talking about the status and development trend of domestic quantitative packaging scales
1.2 Weighing control
1.2.1 Adopt universal weighing instrument and programmable controller (PLC) with fixed value control.
Weighing instrument to realize weight signal conversion processing, weight value display, fixed value output and other functions; while PLC completes the logic control function of quantitative scale. Its process adaptability is strong. It can change the packaging process and control the peripheral equipment by modifying the PLC program. At present, typical domestic models include UNIPULSE 701 instrument + PLC weighing control system.
1.2.2 Special controller for quantitative scale is adopted.
Weight signal conversion processing, weight value display, fixed value control and logic control of quantitative scale are all completed by this controller. This control method has strong professional pertinence. The special function requirements and key technologies required by quantitative scales can be integrated in this dedicated controller.
At present, the typical domestic high-resolution A / D conversion device with a single-chip microcomputer as its core and using Sigma-Delta technology. The A / D conversion circuit is packaged in a high-performance integrated circuit. Due to the serial I2C bus output, the size of the device becomes very small. A / D conversion can be up to 24 bits, while its sampling speed can also reach 4000 times / second, A / D data output speed can reach 100 times / second or higher, and linear error can reach 0.0007% FS.
2. Industry development trends
2.1 Fully automatic system
At present, domestically produced quantitative packaging scales are mainly based on semi-automatic mechanical structures. Domestically produced fully automatic quantitative packaging equipment has poor working reliability and high failure rate. The high-quality fully automatic quantitative packaging equipment required by the market mainly depends on imports. With the continuous increase of labor costs, the development trend of domestic quantitative packaging equipment is bound to gradually replace semi-automatic with full-automatic, in order to greatly increase production capacity. Therefore, domestic manufacturers are required to increase investment in product development and manufacture high-speed, high-precision, high-reliability fully-automatic quantitative packaging equipment to meet the needs of modern production.
2.2 Intelligent control system
Weighing controllers currently used in China are designed based on single-chip microcomputers. Due to the constraints of system resources, the user interface is monotonous, the system software cannot be upgraded online, the PROFIBUS-PA field bus cannot be constructed, and it cannot meet the requirements of modern industrial information management. Therefore, it is required that the quantitative weighing control system develop from the current single function to multiple functions, and gradually realize miniaturization, modularization, intelligence and networking.
At present, the new weighing controller developed by a domestic professional quantitative packaging scale company is based on a 32-bit ARM microcontroller design. It has two analog interfaces for weighing sensors and can control two weighing devices at the same time. , Full Chinese display interface, provides a good man-machine interface, making operation more convenient; RS232 and RS485 standard communication interfaces are configured, which can directly communicate with the weighing control software of the host computer, 10M Ethernet interface to meet the needs of field networked control Requirements; a USB HOST 2.0 interface can store field data on a U disk for backup and management.
The new weighing controller has the characteristics of high integration, reliable operation, friendly man-machine interface, rich interface resources, convenient implementation of software system upgrade and hardware system expansion, and can meet the control requirements that conform to the trend of the modern industrial era.
This product has obvious advantages compared with traditional controllers in terms of product performance: 1. The software can be upgraded online, and the user has multiple returns for one investment. 2. The graphical interface breaks the traditional model and is more vivid and humane. 3. High degree of system integration, more stable and reliable operation. 4. Compared with the traditional weighing controller, it is cost-effective.
3. Concluding remarks
The choice of the specific scheme for each quantitative packaging system should be determined based on comprehensive factors such as material characteristics and production conditions. The quantitative weighing system composed of the quantitative weighing method, control method and common structure described in this article has been well applied and popularized in the seed, grain, chemical, plastic, feed, medicine, condiment and other industries. Practice has proved that, according to the user's requirements, the quantitative packaging scales that are reasonably selected for configuration and optimized design can meet the packaging requirements of the enterprise with complete functions and high reliability. The shortcomings of imported quantitative packaging scales, such as large investment, difficult maintenance, and high maintenance costs, are very obvious. With the continuous development of domestic weighing technology, not only domestic quantitative packaging scales have become the first choice of many production enterprises, but also many quantitative packaging scale products are exported abroad.
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