Research And Design Of Continuous Trays MAP Machine

MAP (Modified Atmosphere Package) technology can effectively slow food ingredients respiratory rate, prevent enzyme deactivation and microbial growth by changing the internal gas composition of food packaging, achieving the purpose of prolonging freshness and shelf life. Therefore it has been widely applied in all kinds of food packaging. Food modified atmosphere package is developed by gas packaging equipment, and the performance of equipment directly determines the quality of packaging. Due to modified atmosphere packaging equipment in China starting late, there is a big gap compared with similar foreign equipment in performance and quality.According to the functional requirements, the process was analyzed and three different ways of working mode, sealing and gas displacement were compared. Continuous circulation, plate heat sealing and vacuum compensation were respectively selected. Motion laws and time of each actuator were analyzed. Working cycle time was calculated. Overall scheme of the cassette continuous modified atmosphere packaging machine was determined, which mainly consists of conveying mechanism of packaging box, packaging film conveying mechanism and modified atmosphere packaging mold.Structures of each executive actuator were devised. First of all, conveying mechanism of packaging box was studied. Chain transmission was chosen and relevant calculation was carried out. Power of the system was computed and the stepper motor selection was completed. Next, pulling film mechanism was designed and transportation route of the packaging film was planned. Pulling film device and controlling device of packaging film conveying length were programmed. Finally, modified atmosphere packaging mold, gas exchange device and heat sealing cutting mechanism were designed. The time of filling and pumping gas was also calculated.Principles and compositions of five gas mixing systems, namely pressure mixing system, volume mixing system, mass flow mixing system, throttling mixing system and timing mixing system, were studied. Moreover, evaluation method of fuzzy technology was used to estimate these five kinds of systems. Timing mixing system was eventually selected.According to the functional requirements of control, controlling system of the cassette continuous modified atmosphere packaging machine was studied and projected. First, pneumatic driving system of the packaging machine was designed, which includes pneumatic circuit design and selection of pneumatic components. Then, electronic control system was planned and control functional principles of each executive mechanism were analyzed. Distributions of PLC I/O interface and hardware connection were completed, with PLC control programs designed.Gas displacement accuracy test, performance and production capacity of packaging machine test and sealing strength test were finished. Gas displacement accuracy test:the best air exhaust time was 2.7s, the best gas charging time was 1.3s, after completion of the packaging, the measured gas replacement rate was 97% and the precision error of gas mixing was less than 2%.Performance and production capacity of packaging machine test:when the rotation speed of drive shaft was 105 r/min and the production capacity was 1002 box/h.The packing machine has the characteristics of good air tightness, fast speed, stable operation and accurate operation.Sealing strength test:it used the packaging machine to prepare samples, and tested tensile strength with electronic universal testing machine. The minimum sealing strength of the packaging machine was 31.74N/15mm. meeting the design requirements.