Debugging Method for Quantitative Packaging Scale

1、 Basic working principle and structure

WhenQuantitative packaging scaleAfter entering the automatic operation state, the control system opens the feeding door to start feeding, and the feeding device adopts two levels of feeding methods: fast and slow; When the weight of the material reaches the set value for fast feeding, stop fast feeding and maintain slow feeding; When the material weight reaches the final set value, close the feeding door and complete the weighing process; At this point, the system detects whether the bag clamping device is in the predetermined state. After the packaging bag has been clamped, the system sends a control signal to open the unloading door of the weighing hopper, and the material enters the packaging bag. After the material is discharged, the unloading door of the weighing hopper is automatically closed; Release the bag clamping device after unloading the empty material, and the packaging bag will automatically fall down; After the packaging bag is dropped, it is sewn and transported to the next workstation. This cycle operates automatically.

The quantitative packaging scale is composed of a weighing unit, a trolley, a sewing bag conveying device, a pneumatic system, a dust removal system, etc. The key component that affects the packaging speed and accuracy is the weighing unit, which includes the storage bin, gate, cutting device, scale body, bag clamping device, bracket, electrical control device, etc. The storage bin is a buffer type bin used for material storage and providing a nearly uniform material flow; The gate is located at the bottom of the storage bin and is used to seal the material inside the storage bin in case of equipment maintenance or failure; The cutting device is composed of a cutting hopper, a cutting door, pneumatic components, and a filling valve. It provides fast and slow feeding during the weighing process, and the material flow of the fast and slow feeding can be adjusted separately to ensure that the quantitative packaging scale meets the accuracy and speed requirements of measurement; The function of the air supply valve is to balance the air pressure difference in the system during weighing; The scale body is mainly composed of a weighing hopper, a load-bearing bracket, and a weighing sensor, which completes the transformation of weight to electrical signals and transmits them to the control unit; The bag clamping device mainly consists of a bag clamping mechanism, pneumatic components, etc. Its function is to clamp the packaging bag, allowing all weighed materials to fall into the packaging bag; The electrical control device consists of a weighing display controller, electrical components, and control cabinet, which functions to control the system's operation and ensure that the entire system operates in an orderly manner according to predetermined procedures.

2、 Weighing and debugging

After checking the sensor wiring, turn on the power supply of the control cabinet and preheat for 15 minutes before debugging. In this article, the maximum weighing capacity is 100kg, the division value is 0.01kg, the quantitative value is 90kg, and the accuracy level meets the requirements of≤ The 0.2% technical requirement is introduced as an example:

(1) Partial load adjustment

Place 10kg weights together on the two load-bearing points of the weighing bucket. When the weighing display shows&quo; Positive difference; When, the sensor output should be adjusted towards the decreasing direction; When the weighing display shows&quo; Negative Difference; When, the sensor output should be adjusted in the direction of improvement. For example, when the output of sensor 1 decreases, a set of trimming resistors related to sensor 1 (original value is 10 ohms) will be rotated to the left by the same amount of rotation.

Rotate to the right (clockwise) to decrease the resistance value and increase the displayed value (denoted as "plus");

Rotate to the left (counterclockwise) to increase the resistance value and decrease the displayed value (denoted as "minus").

Attention: When rotating the fine tuning resistor, if the rotation amount of two resistors in each group is not consistent, it will make adjustment difficult. Therefore, the rotation amount of each group of fine tuning resistors in the sensor should be as consistent as possible during adjustment. The absolute error value of each bearing point shall not exceed 10g, which is considered qualified.

(2) Weighing adjustment

Follow the calibration steps in the weighing display controller manual to adjust the weighing. During calibration, the weights are incremented in the order of 0kg, 40kg, 70kg, 90kg, and 100kg from zero to the maximum value point, with errors not exceeding 10g, 20g, 35g, 45g, and 50g respectively; Reduce the weights in the order of 100kg, 90kg, 70kg, 40kg, and 0kg from the maximum value to the zero point, with an error not greater than the respective tolerance; Repeatability verification shall be conducted at two quantitative points of 40kg and 100kg, each weighing point shall be tested three times, and each time the error shall not exceed the respective tolerance.

(3) Parameter settings

There are many parameters that need to be set for quantitative packaging scales. The following is an example of commonly used key parameters:

a、Weighing display controllerThe quantitative value can be set as a quantitative target value, such as 90kg.

b. Fast increase in lead time, slow increase in lead time.

When the weight is greater than (set value) - (advance amount of fast acceleration), stop fast acceleration and switch to slow acceleration; When the weight is greater than (set value) - (slow feeding advance), stop feeding.

Debugging Method for Quantitative Packaging Scale (2)

Example 1: The quantitative value of a certain material is 90kg, with a fast feed advance of 5kg and a slow feed advance of 0.4kg. Then: the quantitative packaging scale should first add the material quickly, then switch to slow feeding when it reaches 85kg, and stop feeding when it reaches 89.6kg.

Example 2: The quantitative value of a certain material is 40kg, with a fast feed advance of 3kg and a slow feed advance of 0.2kg. Then: the quantitative packaging scale should first be fed quickly, and when it reaches 37kg, it should directly switch to slow feeding. When it reaches 39.8kg, it should stop feeding.

c. Drop

This parameter is an automatic compensation method. At the end of the slow feeding process, some materials have left the feeding device and are still in mid air, ultimately falling into the weighing hopper. The weight value of this part of the material is called the drop. The weighing display controller can automatically detect the drop value and compensate it through a certain mathematical model. Under normal use, the drop value is relatively stable data.

d. Compare Prohibition Time

When transitioning from fast feeding to slow feeding, considering the instantaneous instability of the system, judgment is prohibited within the set time. This period of time is the comparison prohibition time (in seconds). For example, when the comparison prohibition time is set to 1 second, the slow feeding will be maintained for 1 second from the moment when the fast feeding ends, and then the set value will be determined after 1 second to stop the slow feeding. In general, the smaller the material impact, the smaller the prohibition time setting.

e. Judgment time

After the slow feeding is completed, considering the material drop and the system stability, it takes a period of time, which means that after the slow feeding is completed, there will be a delay of some time before the collected weight can be judged. This delay time is the judgment time (in seconds). The smaller the parameter, the better, while ensuring accurate weight collection.

f. Jog compensation time

After the slow feeding is completed, after a delay in the judgment time, the collected weight is judged. If the quantitative value is insufficient and exceeds the allowable error range, the controller will automatically use a jog method to supplement the quantitative value. The duration of each jog is called the jog compensation time (in seconds). When there is a high demand for weighing speed, this function can be turned off.

g. Unloading delay time

In the unloading control, to ensure sufficient emptying of the material, after the weight returns to the zero zone, a further delay of a certain period of time is called the delay time (in seconds). The smaller the set value, the better, while ensuring sufficient emptying of the material.

h. Stability determination time and range

These two parameters are the criteria for determining the stability of weighing. If the maximum difference between all weight collection points within the interval of stability determination does not exceed the range of stability determination, the weighing is considered stable; otherwise, it is considered unstable.

i. Zero zone range

In unloading control, materials often cannot be completely emptied due to sticking and other reasons, and the weight of residual materials after each emptying is also inconsistent. The zero zone range represents the standard for emptying. For example, if the zero zone range is set to 1 kilogram, the weight that cannot be unloaded due to sticking material after unloading control does not exceed 1 kilogram, and it is also considered empty.

3、 Material debugging

Before debugging, first check the relevant components of the quantitative packaging scale for any abnormalities. For example, whether the support legs of the car are lowered to the ground and kept level, whether the air compressor operates normally and whether the pressure is maintained within the specified range, whether the sewing bag conveying device operates normally, and whether the dust removal system operates normally. Only under normal circumstances can feeding and debugging be carried out.

The purpose of material debugging is to achieve the optimal weighing speed of the quantitative packaging scale and meet production needs while ensuring weighing accuracy. In the case of initial use or limited experience, first try to reduce the slow feeding cut-off door as much as possible, increase the fast and slow feeding advance, so as to quickly adjust the weighing accuracy; Then gradually increase the slow feeding cut-off door, reduce the fast and slow feeding advance amounts, until the weighing speed is met.

When verifying the accuracy of weighing, set the quantitative value of the quantitative packaging scale to 90kg. When the material is continuously weighed, perform 20 quantitative weighings. When there are few materials and they are in intermittent operation, quantitative weighing can be grouped. Generally, each group should have no less than 10 tests, and the material testing data should be no less than 3 groups. Record each weighing result, and the maximum allowable deviation between the testing data of the quantitative packaging scale and the average value of the testing data shall not exceed± 126g. The difference between the average value of each group of detection data on the quantitative packaging scale and the predetermined value shall not exceed± 31.5g.

When verifying the weighing speed, when entering the normal working state (with sufficient materials and all system components turned on and running normally), start timing and counting. After measuring 10 quantitative weighing times, stop timing, record the weighing time, and calculate the weighing speed.

The quality of the quantitative packaging scale is not only related to the quality of the product itself, but also to daily maintenance and upkeep. Maintenance and debugging personnel, as well as operators, should be familiar with and strictly follow the relevant safety operating procedures for quantitative packaging scales. Adhering to the principle of putting prevention first and combining pre inspection, pre repair, and planned maintenance can ensure the good performance of equipment and the continuity of production.
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