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Basic principles and application of weighing sorter


Weighing sorter is also called weight screener and weight sorter. It is on-line weight sorting equipment with high speed and high precision. It can be integrated with various package production lines and transmission systems. It is mainly used to check whether the product weight is up to standard and whether there is missing part in the package on line, or send the objects of different weight to the corresponding weight areas.
After improvement of design, the weighing sorter has been developed from previously simple weight checker to current weight sorter. Moreover, there was only one level of removal and sorting, but now, it has over 20 levels. It is often used to sort out seafood, traditional Chinese medicinal materials and meat etc. according to eight and sizes.
On-line weight check is an indispensable link in production of modern industry, especially production of food and pharmacy. During the transmission, weight sorter completes measurement of product weight, and compares the measured weight to the pre-set scope. The control box will send an order to remove the product with disqualified weight, or send the products with different weight scope to the designated area.
The weight sorter generally consists of conveyor belt, controller and input-output transmission mechanism. The weighing mechanism collects weight signals, and sends them to control box. The input transmission mechanism guarantees sufficient space between products by improving speed. The output transmission mechanism is used to remove the products tested.

Working process of weighing sorter is as follows:

Weighing preparation
Generally, entry of products into inlet transmission mechanism and setting of speed of inlet transmission mechanism are co-determined by the spacing of products and the speed required. In this way, only one product will be placed on the scale during weight checking.

Weighing process
       After the products enter the weighing transmission machine, the system will recognize the products to be tested and to enter the weighing area according to the external signals, such as optoelectronic switch signals or internal level signals. According to operating speed and length of weighing transmission machine or the level signals, the system can judge the time when products leave the transmission machine. From entry into the scale and departure of products, the weighing sensor can test the weight signals. The controller selects the signals in the areas with stable signals to process and thus to obtain the product weight.
Sorting process
After the controller receives the weight signals of products, the system will compare the measured weight to pre-set weight, and sort out the products. The sorting types will vary as the application varies. The main types are as follows:
1) Remove disqualified products;
2) Remove the overweight and underweight products or send them to different places;
3) Divide the products to different categories according to their weight scopes

Report feedback
The weight checking machine has weight signal feedback function. Generally, it reports the average weight of products with set quantity to controller of packing/filling/can packing controller. The controller will adjust the feed amount dynamically to make the average weight of product approach the desired value.
Except for feedback function, the weight checking machine can also provide abundant report functions, quantity of packages in each area, total quantity of each area, number of qualified products, total number of qualified products, average value, standard deviation, total number and total accumulated number.
Weight sorter can be used in many industries, like food, pharmacy, chemical industry, beverage, plastics and rubber etc.  

It is mainly used in the following situations:
1. Final inspection of product weight
The weight of product will be re-checked in the final link of production, and the disqualified products will be removed, in order to ensure that the weight of product leaving the factory is up to standard. This is conducive to the benefits of both consumers and the manufacturer. The consumers will not suffer a loss due to insufficient quantity, and consumers will suffer the damaged reputation due to complaint of customers.

2. Feedback control
Except for weight signal of product, weight sorter will remove the disqualified products, and output the feedback signals of difference value of average weight and nominal weight to the packing filling equipment. It also adjusts the average weight to make it consistent with the set weight automatically, in order to reduce the production cost. For example, the weight of each package of milk powder is 450g, there is no need to use the weight sorter. The average weight of package should be 453g to ensure the weight of product is up to standard. After the automatic weight feedback control is applied, the average weight can meet 450g. Based on the assumption that ten thousand packages can be produced every day, 30000g can be saved every day, and 10.8 tons can be saved every year. As the price of each package of intermediate-leveled infant milk powder at the market is 15 yuan, 360,000 yuan can be saved every year.

3. Inspection on insufficiency of products
Due to equipment or manual factors, the products in small packages in an outer package (e.g. beverage case) will be missing. To use the weight sorter to check the weight of outer packages in order to ensure that there is no insufficiency of products in them. For example, the weight of a box containing 24 bottles is definite, so it is feasible to check whether there is neglected loading to check the weight of each case.

4. Classification
The products with non-uniform weight can be classified automatically. For example, as the manufacturer cutting chicken divides the chicken legs of different sizes into different weight scope, it can use the weight sorter to weigh each chicken wing automatically, and send weight signals to PLC. PLC can drive the corresponding pulling board according to the scope set to send the wings to the corresponding box. In this way, the automatic classification is fulfilled.

The above application is some regular application of weighing equipment. The weighing sorter is also applicable to military industry and press industry etc. An American agency once used the weight checking machine to check the weight of each bullet, because the weight of bullet will influence its flight path. In addition, weight sorter can also be used to count the number of pieces of newspaper while sorting out them.  If the quantity of newspapers counted while binding up is not accurate, the total quantity distributed to various areas will be inaccurate. However, counting of weight checking machine can be fast and accurate, and this saves plenty of labor.