Views: 231 Author: Site Editor Publish Time: 2021-08-26 Origin: Site
Usually, bulk materials need to be packaged quantitatively when they leave the factory, that is, bulk materials are divided into individuals with the same weight in units of weight or volume to facilitate storage, transportation and use. Especially food, after packaging by small scale packaging machine, it can also avoid contamination and deterioration during the sales process.
When bulk materials are quantified, suitable weighing packing machine can be selected according to the shape and type of materials, the requirements of packaging specifications, packaging accuracy, and packaging speed. According to the quantitative principle, the powder packing machine can be divided into two categories: weighing type and constant volume type. Generally speaking, the fixed-volume packing weight machine of the same price is faster than the weighing-type packaging machine, but the accuracy is slightly worse, and there are certain requirements for materials.
The weighing of the weight packing machine is a dynamic process, and the accuracy of dynamic weighing is closely related to the automatic quantitative control process. The weighing part of the weighing and packing machine is usually composed of a feeding part, a weighing part, a control part and a weighing instrument. Therefore, the difference between the actual weight and the set weight is the comprehensive reflection of the errors caused by these parts in the weight. We can divide it into the following three categories.
1. Electronic weighing error
1) Error of load cell
2) Error of weighing instrument
3) The error of the weight transmission of the scale body
2. Automatic control error
1) Repeatability of control element response
2) Repeatability of actuator actions
3. External interference error
1) The impact of the weight of the material during feeding
2) Changes in material characteristics
3) Changes in the vibration of the scale body
4) Changes in other factors
Due to the impact during feeding and other factors, oscillation occurs when the feeding amount is switched. During the entire feeding process, the weighing indicator continuously samples and compares the sampling result with the set weight. When the maximum amplitude value exceeds the set value, the weighing indicator will pick up a false weight value and stop slow feeding, resulting in the unqualified products. The amplitude of the vibration generated by the impact is related to the material flow, the material drop and the rigidity of the electronic packaging scale body. This limits the material flow rate for fast feeding.
Among the above three types of errors, we can improve the hardware or use software methods to eliminate or weaken the influence of the accuracy of the symmetry. Practice has proved to be effective.
1. Reasonably select the form and accuracy of the load cell, use a stable performance amplifier, and select an A/D converter suitable for the dynamic weighing system. Experiments show that when the A/D conversion rate is increased from 10Hz to 30Hz, the weighing time can be reduced by 25-40%.
2. Reasonably design the electronic packing scale body to reduce mechanical friction and improve the consistency of force transmission.
3. Shorten and stabilize the response time of the control components and the action time of the actuator, use integrated components instead of separate components, reduce the intermediate links of the actuator, and replace the mechanical mechanism with electric or pneumatic actuators.
4. Adopt suitable feeding devices and auxiliary measures for different materials to keep the material flow stable and consistent during the feeding process of automatic weight packing machine.
5. Use software to realize automatic zero tracking and drop correction of weighing and bagging machine.
6. Use feedback correction system to adapt to changes in material density.
Follow us to know more information.