this article introduces the weighing process of the combination scale, expounds the hardware and software components of the combination scale control system, and analyzes the performance and features that the system can achieve.
Key words: multihead weigher; combination scale;Step motor
Since its introduction in the 1970s, the combination scale has been widely used in food, medicine, chemical and other industries. It solves the problem of metering and packaging of uneven materials, with high measurement accuracy, fast packaging speed and high reliability, especially for some high-value granules or block products, fast and accurate quantitative packaging can be achieved, the precision can be controlled within ±1 gram, and the fastest weighing speed is 240 packs/min. Because the imported combination scale is very expensive, its application is limited.
First,weighing process of combined weigher The combination scale is mainly composed of weighing mechanism and control system. JW-A waterproof type 10 heads combination scale is one of the main products of Guangdong Kenwei Intellectualized Machinery Co.,Ltd, which has 10 weighing hoppers and target combination. The weight is 3000g, the speed is ≥60 packs/min, and the precision can be controlled within ±1.5g. The material is collected from the collecting hopper, through the circular vibration distributor and the radial feeder, and the material is quantitatively put into the corresponding preparation hopper for temporary storage, the material of the preparation bucket is opened, the material enters the weighing hopper for weighing, and the material is put into the hopper after the material is finished. The door is closed and the material continues to be stored.The microcomputer combines the measured ten weighing values into a total of 1023 combinations of 210-1, and selects the best weighing combination. The weighing hopper door belonging to the best weighing combination is opened, and the material is discharged. The warehouse flows out into the package. At the same time, the radial feeder automatically feeds the empty hopper. This cycle is repeated until it is stopped artificially. If a hopper is not selected for 30 consecutive working cycles, the hopper is forced to be discharged once, and the best combination is selected among the combinations containing the weight of the hopper, and the hopper of the material is removed. The weight sensor is automatically zeroed. The opening and closing of the material door is driven by a stepping motor, and the opening and closing speed of the material door is finely adjusted according to the characteristics of the material. The level in the collecting hopper is detected by a photoelectric sensor.
Second,system of hardware design
AD620 is a kind of small volume, low power consumption, high precision instrumentation amplifier. It is suitable for accurate data acquisition system and multiplex application system.
2. A/D converter
Successive analog-to-digital converter, which has high conversion speed and precision, low power consumption and a power-down mode of only 10A. The conversion time is 9.4s, with single and dual polarity inputs and tri-state serial Data output mode, with sample and hold circuit. The A/D conversion process is controlled by a single chip or a PLC.
3.step motor drive circuit
There are 20 hoppers in the hopper and weighing hopper. In order to make the door open and close smoothly and prevent material damage and stuffing, each hopper is driven by a step motor.
Third,system of software design
When the combination weigher is working, it must complete the capacity of 70 packs / min (1 pack / s) or more, that is, complete the weight detection, combination calculation, find the best combination, etc. in at least 1 s to complete the packaging, in which the combination calculation More time-consuming, high-performance single-chip or PLC, can directly complete the detection, calculation, control output, not only meet the accuracy requirements of the real-time control of the combination scale, but also meet the packaging speed requirements, is a more effective control method. When the control system works, the MCU or PLC sends a signal to the multi-way switch, and 10 load cells are selected in time. The signal is amplified, A/D converted, input to the MCU or PLC, and combined calculation of 10 input values. Get a set of weighing hopper numbers where the best combination is located, control the speed and direction of the corresponding stepping motor according to the number, make the group door open, complete the unloading, and then close the material door; the material level in the storage hopper is detected by photoelectricity Switch detection. In addition, the system also designed display, alarm and keyboard circuits to make the system more complete.
The combination weighing technology represents the highest level and development direction of today's weighing technology with its high precision and high speed. In the past, China mainly relied on imports from Japan, Australia and other countries. Due to the high price, it hindered the wide application of computer combination scales. popular. However, with the rapid development of China's commodity packaging in the direction of high speed and high accuracy, computer combination scales will quickly enter China's commodity processing and packaging industry. It can be said that the development of the packaging industry has promoted the development of weighing technology. At the same time, weighing technology has also improved the packaging level and promoted the development of the packaging industry.
Guangdong Kenwei Intellectualized Machinery Co.,Ltd.has become a professional manufacturing base for large-scale combination scales in China. It is the first in China to receive the “Guangdong Province Industry-University-Research Technology Project Combination Award” in the field of combination scales. "In honor of the company, in 2017 relying on the support of more than 800 new and old customers from 87 countries and abroad, to achieve sales of more than 5,000 sets of weighing packaging equipment, 2018 Kenwei company layout semi-automatic production mode, refine the sub-components The specialized production mode can achieve 7,000 sets of production capacity while accelerating the production cycle. Kenwei has undoubtedly become a brand that the packaging machinery industry relies on.
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