[Abstract] This paper starts with the introduction of the structure and working principle of quantitative packaging scales, analyzes several factors that affect the packaging speed of quantitative packaging scales, as well as several problems that should be paid attention to during design, for your reference. 

[Key words] quantitative packaging scale; packaging speed [Chinese Library Classification Number] TH715.1+6 [Document Identification Code] B 

First, Introduction 　　

With the development of social productivity, enterprises have higher and higher requirements for production efficiency. More and more enterprises demanding quantitative packaging equipment have placed higher demands on the packaging speed of packaging equipment. How to adapt to the development of this market, sum up experience, and develop a quantitative packaging equipment that not only has high measurement accuracy and fast packaging speed, but also puts it in front of us. Below, I will start from the structural composition and working principle of quantitative packaging scales, talk about several problems affecting the packaging speed of quantitative packaging scales and solutions. 

Second,The quantitative composition of the packaging scale and working principle 

1. The structure of the quantitative packing scale: The structure of the basic quantitative packing scale is shown in Figure 1. It mainly consists of the storage bin, the emergency maintenance gate, the feeding device, the weighing device, the sensor assembly, the bagging device, the bracket, Electrical control cabinet, each device actuator, conveyor sewing mechanism and other components. The main functions of each part are:

   1.1 Storage bin: used for material storage, providing a nearly balanced material flow for the packaging process, which affects the measurement accuracy and speed of the packaging equipment to a certain extent.

   1.2 Emergency maintenance gate: used to cut off materials during temporary maintenance.

   1.3 Feeding device: Most feeding devices consist of two-stage feedstock, which is the main factor affecting the accuracy and speed of feeding.

   1.4 Weighing device: The material weight signal is collected by the sensor component.

   1.5 Clamping device: Complete the clamping work of the packaging bag, so that the weighed materials can smoothly enter the packaging bag.

   1.6 Bracket: Provide a connecting backbone for each part.

   1.7 Each device actuator: When the required speed is fast, the pneumatic actuator is generally used to complete the action of each part. The speed of the speed affects the accuracy and speed of the packaging equipment to a certain extent.

   1.8 Conveying and sewing machine: complete the conveying and sewing work of the packaging bag.

   1.9 Electrical control cabinet: It is the main control center of the packaging equipment, which realizes the control and indication of the whole equipment.

   
   

   2. The working principle of the quantitative packing scale: the initial working state is: the feeding device and the weighing hopper discharging door are in the closed state, the bag clamping device is in the loose state, and when the automatic running state is entered, the control system control is turned on. The fine feed gate starts feeding, and the weight signal of the material is converted into an analog signal by the sensor and sent to the weighing display controller, which is converted into a digital signal by preamplification and A/D conversion for data calculation and control; When the weight signal reaches the coarse feed setting value, the coarse feed gate is closed to keep the fine feed; when the detected weight signal reaches the fine feed set value, the fine feed gate is closed and the final compensation is passed by the drop. Meet the accuracy required by the system. At this time, if the system detects that the bagging device has clamped the packaging bag, it sends a control signal to open the weighing hopper discharge door, and the material enters the packaging bag. After the material is discharged, the weighing hopper discharge door is automatically closed, and the weighing is stabilized. Then enter the next feeding process. At the same time, the bag-carrying device is loosened, the bag is automatically dropped, and transported by the conveyor to the sewing station. This cycle is repeated.  

Third, analyze the factors affecting the packaging speed:

Combined with the basic structure and working principle of the above quantitative packing scale, we can draw a graph of the feeding amount and working time (Figure 2). 

Where: t0~t2 is the coarse feed time 

T1~t2 is the stable judgment time of coarse feedstock 

T2~t4 is the fine feeding time 

T3~t4 is the stable judgment time of fine feedstock 

T4~t6 is the compensation time for the drop compensation 

T5~t6 is the final value stabilization time 

T6~t7 is the final value stable delay time 

T7~t8 is the discharge time 

T8~t9 is the stable zero time of the weighing hopper 

From Fig. 2, we can see that t0~t9 is a packaging cycle of the quantitative packaging scale. The problem of increasing the packaging speed is also the problem of how to shorten the packaging cycle time. The time used in Figure 2 is basically done by the feeding device and the weighing device, so designing a good mechanism in both aspects is necessary to increase the packaging speed of the quantitative packaging scale. 

1.Effect of the feeding device on the packaging speed: In Figure 2, the feeding time takes a considerable amount of time throughout the packaging cycle, which is also the most important in the impact on the packaging speed. Its main factors are:

1.1 Design of the hopper: The ability of the feed port to directly determine the amount of feed per unit time, should first meet the requirements of the feed amount. Otherwise, if you only design a feeding hopper by experience, if the feeding port can not meet the requirements of the feeding amount, it is also a waste of effort in other aspects. The verification of the feeding port passing ability can be carried out according to the following formula:

 For the rectangular outlet: 

1.2 Design of the actuator: In the design of the actuator, the size of the coarse and fine feed should be clarified first, and the movement stroke of the actuator should be selected according to the structural characteristics. Secondly, an actuator with a higher moving speed should be selected. Pneumatic actuators have been adopted in most of the current quantitative packaging equipment because of their fast moving speed, easy installation and use, and reliability and pollution-free. 

1.3 Feeding port adjustment mechanism should be designed in the feeding device. Feeding speed and feeding accuracy are a contradiction. The use of a large feed port can increase the feed rate. However, from the perspective of control and debugging, the size adjustment mechanism of the feed port should be designed. In the case of feed accuracy, the speed is gradually increased. 

2. Design of the weighing device: In Figure 2, the length of the feed stabilization time and the discharge time also affect the feed rate. 

2.1 In the weighing device, in order to ensure that the weight signal of the material in the weighing hopper is accurately transmitted to the load cell, the limit device on the weighing hopper is not affected by the additional force generated by the symmetrical measuring bucket, so it must be retained. The balance of the activity, and at the same time due to the impact of the material and the vibration generated by the action of the various components, will be transmitted to the weighing hopper through the steel structure bracket, resulting in a slow stabilization speed of the weighing hopper, which makes the feeding process stable for a long time. In order to solve this problem, we are required to design a weighing device, while ensuring the stable and accurate transmission of the weight signal, try to consider a better limit structure, make the weighing hopper fast and stable, and consider the vibration reduction measures to minimize Determine the time. 

2.2 Design of the weighing hopper structure: In the structural design of the weighing hopper, the structure of the weighing door directly affects the speed of the discharging speed. Therefore, when designing the weighing door, the discharge stroke of the discharging door should be as short as possible and the speed is fast. 

3. In order to reduce the influence of the symmetry speed of the drop compensation time, the weighing device should be combined with the feeding device to carry out the overall design. The distance between the weighing hopper and the feeding hopper should be shortened as much as possible, and the air column should be reduced and reduced. The amount of drop allows the air column time to be shortened and the impact of the symmetric material bucket of the drop material to be reduced, and the settling time is shortened.  

4. Software design: In terms of software measures, Comrade Han Jianjun of Shenzhen Jieman Company proposed a good method, which is to introduce the concept of prohibiting comparative discrimination and group detection to improve speed. The comparison is forbidden. After the end of the pre-feeding, the signal is judged by delay and then the signal is judged to overcome the influence of the impact value, and the pre-feeding amount is increased to increase the weighing speed. The group detection is to check the symmetric data of the applied mathematical statistics and error analysis principle. Since not all the data are detected and recorded, the data can be saved without waiting for the scale to be stable. Time is up.  

Fourth, the conclusion 

Through the analysis of the above aspects, I briefly talked about my own opinions. The factors affecting the packaging speed of packaging scales are multi-faceted. Different analysis should be carried out according to different situations. The above is my opinion, I hope that the peer teachers will criticize and correct. Fortunately, China's quantitative packaging scales have flourished, especially the manufacture of combination scales, represented by Guangdong Kenwei Intellectualized Machinery Co., Ltd., which uses a stable time mode, anti-jamming AD module technology and equivalent system filtering. The volume has become a large-scale trend. The improvement of the packaging speed of domestic quantitative packaging scales also requires everyone's joint efforts. I hope that we will all contribute to the improvement of the packaging speed of quantitative packaging scales.