Wide application of electronic combination weigher weighing technology

With the development of science and technology, quantitative packaging of products is widely used in all walks of life, and synchronized measurement is carried out by means of mechanical systems. Especially for small-scale quantitative packaging, high measurement accuracy is required, and the best calculated value close to or slightly larger than the calibration value is required as the output volume of the material. The conventional quantitative packaging scale is a single scale, which can barely carry out quantitative weighing of uniform and small-particle bulk materials, but the fastest packaging speed can be 15-30 bags/min, but for sugar, dried fruit, If uneven items such as potato chips are weighed with a single scale, both the accuracy and speed of the weighing are difficult to meet the production requirements. The electronic combination weigher based on the combination weighing technology can effectively improve the measurement accuracy and speed, and solve the problem of uneven item measurement and packaging. According to the number of hopper heads, the electronic combination weigher has 8, 10, 14, 16, 20, 24, 28 heads, and the more commonly used ones are 10 and 14 heads. The electronic combination weigher is an intelligent combined quantitative automatic packaging weighing instrument in the weighing industry. The combination weighing technology meets the needs of mass production, expands the weighing function and application range, and adds new content to the concept of weighing.

The working principle of combination weighing
The material falls into the cross-cutting hopper of the combination weigher through the elevator, and the vibration machine vibrates to make the material evenly distribute the product on the conical funnel to the linear feeder pan. When there is no material in the cross-cutting bucket or the material is not enough, it will be detected by the horizontal photoelectric detector, and then send a signal to the main board, and then send a feeding signal to the conveyor through the main board to feed. The material is vibrated through the linear feeder, and the product is sent to each buffer hopper through the amplitude and vibration time. Then the driving equipment, the stepping motor, works, and the buffer hopper is opened to send the materials into the weighing hopper.

In the weighing hopper, the product generates a weight signal through the sensor, and then transmits it to the main board of the control device through the lead. The CPU on the main board reads and records the weight of each weighing hopper, and then selects it through calculation, analysis, and combination. For the combination weighing hopper closest to the target weight, when the CPU receives the allowable discharge signal from the packaging machine, it sends a command to start the driver to open the collection hopper to unload the product to the packaging machine, and send a packaging signal to the packaging machine.

The feeding process obeys a normal distribution as a whole. Although the dispersion is large, if there are enough combinations, multiple units can be combined to obtain a high-precision overall. The feeding result is a combination of weighing and calculation. This is fundamentally different from traditional measurement methods. The use of this high-tech working principle can be superior to the speed and accuracy of ordinary automatic quantitative devices. Moreover, not only can the irregular lumps be measured, but all the flowable materials can be quantified by the computer combination weigher.

When the general single-head weigher is about to reach the target weight, in order to ensure accuracy, the feeding speed cannot be too fast, while the computer combination weigher can feed quickly, and the feeding amount of each hopper is usually set at 1/3 to 1/ of the target weight. 5. The combination weigher only uses part of the combination when calculating the combination. The computer can calculate the number of combinations according to the number of heads participating in the combination by the following formula: n=Cim=m!/i!(mi)!, where: m is the weighing bucket The total number of, I is the number of buckets participating in the combination. Generally, as m and I increase, the number of possible combinations increases, and the more likely it is to get qualified products. However, although the computing speed of the microcomputer is very fast, too many combinations will reduce the packaging speed and increase the cost. In terms of rationality and economy, m usually takes 8 to 16, and I generally takes 3 to 5.

Electronic combined weighing control system
When the combination weigher is working, it must complete the capacity of 70 packs/min (1 pack/s) or more, that is, it must complete the weight detection, combination calculation, find the best combination, etc. within 1s at least, so as to complete a package, including the combination calculation It is relatively time-consuming. High-performance single-chip microcomputer or PLC can directly complete detection, calculation, and control output, which can not only meet the accuracy requirements of combination weigher real-time control, but also meet the requirements of packaging speed. It is a more effective control method. When the control system is working, the single-chip microcomputer or PLC sends a signal to the multi-channel switch, and 10 load cells are selected in time sharing. The signal is amplified, A/D converted, and input to the single-chip microcomputer or PLC, and the 10 input values ​​are combined and calculated. Get the number of a group of weighing hopper where the best combination is located, and control the speed and direction of the corresponding stepping motor according to the number, make the group of material doors open, complete the unloading, and then close the material door, the material level in the storage hopper is detected by photoelectric Switch detection. In addition, the system has also designed display, alarm and keyboard circuits to make the system more complete.

The advantages of electronic combination scale
Combination weighing technology with its high precision and high speed represents the highest level and development direction of today’s weighing technology. In the past, my country mainly relied on imports from Japan, Australia and other countries. Due to the high price, it hindered the wide application and development of computer combination weighers. universal. However, with the rapid development of my country’s commodity packaging towards high speed and high accuracy, computerized combination weighers will quickly enter my country’s commodity processing and packaging industries. 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 level of packaging and promoted the development of the packaging industry.

Post time: Jul-28-2021