| With the wide application of automatic production line in the intelligent manufacturing,the influence of its whole machine’s stability on the processing quality of the products is becoming more and more obvious.The pusher,also known as feeder,is an important part of automatic production line,its motion stability directly affects the performance of the whole machine.In this paper,the pusher of a capsule automatic production line is taken as the research object.The multi-objective optimization design based on NSGA-Ⅱ genetic algorithm is used in the gear-linkage mechanism to improve the motion stability of mechanism,under considering comprehensively the influence of kinematics characteristics and gear’s meshing characteristics.Then the influence of the profile modification parameters on mechanism’s transmission characteristics is discussed.The main work and conclusions are as follows:Firstly,the crank-gear-rack mechanism is employed as the main drive mechanism of pusher according to the work requirements,in order to realize the pusher’s function of auto-commutation and long-distance transmission without changing the revolving speed of the motor.The mathematical analysis model of the mechanism is established by taking the gear angle,the gear angular acceleration and the contact ratio of gear-rack as optimization objectives,based on the requirements of mechanical kinematic characteristics and the gears’ mesh characteristics.By using the NSGA-Ⅱ algorithm,the multi-objective optimization of the parameters is carried out and a set of optimal solution is obtained.In the meanwhile,the optimal design scheme is determined.The kinematic characteristics are analyzed to the fore-optimized and post-optimized mechanism on Matlab.The results show that: in the promise of ensuring mechanical smooth operation,the swing angle of gear is increased from 7.365 rad to 9.875 rad,which improves the ability of reciprocating motion with long stroke to the mechanism.Secondly,by combining ANSYS finite element technology with ADAMS virtual prototype technology,the rigid-flexible coupling dynamics simulation of optimized mechanism is carried out.The maximum tooth modification value is determined based on the finite element contact analysis,and two kinds of modification methods with long and short modification are proposed.Then from the perspective of statics and dynamics,the effects of the two kinds of methods on gears’ meshing characteristics are analyzed and discussed under different load conditions.The results show that the short modification method is more suitable for the gears in this paper,and the modification length is 1 mm,modification value is 0.02 mm.Modified gear’s meshing impact is reduced obviously and the stationarity of the whole mechanism is improved.Finally,the rationality of the pusher’s structure is verified from three aspects: the natural frequency of the gearbox,the static characteristics of the output shaft and the simulation of the propulsion process.At the same time,the comparison is carried out about contact situation between mold and push claw at the initial moment under three push approaches,including constant speed,fore-optimization pusher and post-optimization pusher.The results show that: the structure of the designed pusher can work reliably,the pusher has the advantages of stable acceleration,smooth motion and small impact force at the initial moment,which is satisfied the work requirements of the automatic equipment.In summary,the optimization of pusher mechanism is carried out from two sides: the design of the dimension parameters and the tooth profile modification,which improved the overall stability of the mechanism and reduced the vibration shock.The research results can provide the theoretical reference for the design of gear-linkage mechanism. |
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