Design And Analysis Of Needle-hook Mechanism Of High-speed Tufting Carpet Machine

As the main base material,carpet has become an indispensable part of daily life.In order to increase production,we should not blindly pursue the expansion of production scale.Therefore,under the limited production scale,it is an inevitable trend to realize the high-speed tufting machine.At present,the maximum spindle speed of domestic tufting carpet machine is generally not more than 500-600 r/min,while the maximum spindle speed of foreign tufting carpet machine can reach 1000-2000 r/min.Under the same production scale,the productivity difference is obvious.In China,the poor dynamic characteristics of needle-hook mechanism especially needle mechanism of tufted carpet machine at high speed is the most critical problem that restricts the speed.That is,after high speed,the needle-hook mechanism will produce excessive speed,acceleration,balance moment and dynamic imbalance.Therefore,in order to improve the kinematics performance of the needle-hook mechanism,reduce the balance moment and dynamic unbalance,and increase the spindle speed of the tufted carpet machine,the design of the needle-hook mechanism,kinematics and dynamics modeling analysis and dynamic balance optimization of the tufted carpet machine are studied in depth in this paper.The main research contents are as follows:(1)Considering reducing the dynamic unbalance of needle-hook mechanism and meeting the requirements of loop height and needle-hook timing coordination,a new needle-hook mechanism was designed.The needle mechanism has a symmetrical structure,which reduces the dynamic unbalance.The hook mechanism has the motion characteristics of "fast in,slow out" similar to long stop,which ensures the quality of weaving at high speed.(2)In order to verify the rationality of the needle-hook mechanism,the kinematics and dynamics of the needle-hook mechanism are analyzed.Firstly,the closed vector method is used to establish needle-hook.The kinematics model of the mechanism is simulated and analyzed by using MATLAB,and the displacement,velocity and acceleration line diagrams of each moment are obtained.Secondly,the dynamic model of needle-hook mechanism is established by force balance method,and its simulationanalysis is carried out by using MATLAB.The reaction force and balance moment of each pair are obtained.Finally,the kinematics and dynamics characteristics of the traditional needle-hook mechanism are compared and analyzed horizontally.The rationality of mechanism design is verified by analysis and comparison.(3)In order to further optimize the kinematics performance of the innovative pin-hook mechanism,the speed and acceleration of the pin slider,the angular acceleration of the hook point and the K value of the quick return characteristic were optimized by using ADAMS software.A multi-objective optimization function is established to measure the velocity and acceleration of the needle slider.The optimal design of the needle mechanism is carried out under the constraints of the mechanism's existence and motion.The optimal hinge position and the parameters of the rod length are obtained.A multi-objective optimization function is established to measure the angular acceleration of the hook block and the angle between the poles.The optimal design of the hook mechanism is carried out under the constraints of the existence of the mechanism,the requirement of the motion and the range of the transmission angle.The optimal hinge position and the parameters of the rod length of the hook mechanism are obtained.(4)In order to reduce the balance moment of the new needle-hook mechanism and its influence on the vibration of the mechanism.On the basis of dynamic analysis,the needle-hook mechanism is synthetically optimized for dynamic balance,and an optimization model of "concentrated point mass" is established.The design objective is to reduce the reaction force of all kinematic pairs,and the position of the center of mass and the center of mass to the center of rotation pair is taken as the design variable to ensure that the kinematic characteristics of the mechanism do not deteriorate as a constraint function.The minimum equilibrium moment of the needle-hook mechanism is obtained.