Airflow-induced Separation Method For Stacked Paper Labels And Its Application

Paper labels are widely used for product identification.Separating individual labels from stacked labels is a challenging common task in automated packaging.At present,there is no separation method that can separate flexible breathable labels while meeting the requirements of high reliability(greater than 99.9%)and high efficiency(less than 1 second/sheet).This thesis has proposed a separation method for stacked paper labels based on airflow,which is studied from the theoretical,numerical simulation,and experimental aspects.The main research and conclusions are as follows:1)The physical model of the paper label has been modeled.The discrete Spring-Mass Beam model is used to describe the mechanical model of the label.An experiment was designed based on the beam bending method of a non-linear cantilever beam,and the bending stiffness of the label was tested.In addition,the air permeability of the label was described based on the Forchheimer quadratic high-speed non-Darcy flow empirical formula,and the corresponding experimental methods were designed and the air permeability parameters of the label were measured.2)A separation method for the airflow-induced paper label has been proposed.Simulation analysis on the failure of the vacuum chuck to pick the paper label was conducted,and it was concluded that the permeability of the label material which causes the vacuum suction force to be transferred between the stacked labels was the reason for the failure of the chuck to pick the label.So a new method has been proposed that uses airflow to induce the pre-separation of stacked paper labels,blocks the transmission of vacuum adsorption force,and then picks one of them up with a vacuum chuck.Two speculations about the separation mechanism with and without the initial gap have been put forward on the basis of force analysis of paper label under airflow.3)The mechanism of separation of air-induced paper labels has been studied with numerical simulations.Abaqus CEL(Coupled Eulerian-Lagrangian)method was used to numerically study the process of paper label separation induced by airflow without the initial gap.The results show that there are three stages in the dynamic process of airflow-induced label separation: the initial gap generation stage,the micro-gap expansion stage and the separation channel formation stage.Further numerical simulations were carried out on these three stages respectively by using ANSYS,and the force of paper label separation in each stage was found.At the same time,it is observed that the label separation would flap unsteadily when the air-flow velocity exceeded a certain value.In this thesis,the linear stability theory was used to study the flap phenomenon of label separation,and the numerical simulation verified the correctness of the theoretical analysis.4)A complete implementation scheme of paper label separation induced by airflow has been proposed.According to the force and constraint required by the paper label separation method,the corresponding structural realization scheme was proposed,and its mechanical model was established.The physical parameters of the scheme,including fluid load,constraint and force of the label and physical characteristics of the label,which affect the separation performance of the label,were analyzed.A local sensitivity analysis on these physical parameters was also performed to obtain the sorting of the effects of these physical parameters on the label separation performance.5)The separation method of paper label induced by airflow has been verified by the experiment.The detailed structure of the label separation module based on the implementation scheme was designed.Its manufacturing and debugging were completed and it has been integrated into the automatic packaging machine.The experimental tests on label separation were performed.It was observed that the first label was always separated preferentially,the separation time was less than 0.1s and separation efficiency was more than 3600 sheets/min.The label separation module could achieve 3s/ sheet processing efficiency and 99.9% reliability,which verified the high efficiency and reliability of this method.Experiments on nozzle airflow velocity,label constraints,and different labels have verified the previous conclusions drawn from theoretical and numerical analysis.Four kinds of paper labels with different specifications were tested,and the test results showed that the paper label separation method has wide adaptability.