| Automatic weighing is one of the key technologies of automatic packaging system,which is widely used,with the requirements of "high yield,fast blanking,sealing and dustproof,automatic calibration,etc.".This thesis determined essential functions and performance indexes of the weighing equipment according to packaging system’s demand,studied automatic gravimetric weighing method,designed and analyzed the weighing principle,divided the equipment into four modules of storage,feeding,weighing and bagging with "modularization" method,completed mechanism body design and made assembly and test scheme.The quantitative weighing method of gravimetric two-stage-variable-speed feeding is adopted.Gravimetric blanking can realize fast blanking,and the minimum bagging time is 0.5s.Variable feeding,where blanking speed is adjusted by changing opening of the door,achieves coarse and fine feeding,ensures both accuracy and fast blanking to achieve the unity of speed and accuracy of weighing.In the design above,automatic sealing is realized by changing the hopper’s opening direction and shape to match with the cylinder group,which can reduce the redundant mechanism.An improved automatic calibration device is presented,realizing lightweight design,material fatigue reduction and the equipment’s service life extension by reducing the load.Multiple processes are completed in the same position to simplify the operation logic,strengthen inter agency coordination and shorten the operation period.This thesis used discrete element method to study flow characteristics of granular materials,analyzed effects of different storages’ opening on blanking speed,the bigger opening the faster blanking,but granules occurs twice loose during dropping,the average mass flow rate constants steady.The weighing device designed was verified to meet the requirement of production rate and precision after time and force analysis with methods and conclusions described.The automatic weighing equipment designed realizes the integration of automatic granular packaging system,achieves high yield of 1440 bags/h,which has strong competitiveness compared with similar products in the market,and promotes the user to upgrade production line. |
