Research On Optimization Design Of Presser Foot And Needle Rod Drive Mechanism In High Speed Embroidery Machine

The development of productivity has brought tremendous changes to the high-speed computer embroidery machine industry.The new embroidery machine with high efficiency and low amplitude has become a technical problem that the embroidery machine industry urgently needs to tackle.Embroidery machine generally takes cam as transmission component,and its needle bar,foot pressing and thread taking-up parts all take cam as the starting point of the kinematic chain.In the process of cam transmission,because its characteristics will produce inertia force and impact,the increase of rotational speed will aggravate the vibration of embroidery machine and reduce the quality of embroidery products.Therefore,based on the double cam driving mechanism of needle bar-foot pressing part,this paper analyses and solves the motion law of needle bar and foot pressing part of embroidery machine,and optimizes the design group.In order to replace the double cam driving mechanism,the combined link driving mechanism is studied and experimented.The following studies have been completed:(1)According to the double cam driving mechanism of needle bar and foot pressing part of embroidery machine,the motion law and function relationship of needle bar and foot pressing part are analyzed and solved.Based on the calculation and simulation results,the constraint range of the rotation angle of the pin and pin was established,and the kinematics model of the combined linkage driving mechanism is established.(2)The objective function of the output curve of the combined linkage driving mechanism is constructed.Based on the output motion curve of the double cam driving mechanism,the optimal objective function is compiled in the range of the corner constraint by the least square method.The optimal solution of rod length is obtained by iteration of genetic algorithm.Under the condition that the parameters of the rod length of the combined linkage drive mechanism are determined,the output curve is compared with the output curve of the double cam drive mechanism.The output of the needle-bar motion fits perfectly,and the output fit rate of the key movement of the pin is above.The above results provide a theoretical basis for the feasibility of replacing double cam driving mechanism with combined linkage driving mechanism.(3)The dynamic balance optimization method of mass moment substitution is used to optimize the design of the combined connecting rod driving mechanism.By dividing the treesystem and the branched components of the combined linkage drive mechanism,the mass moment on the branched components is transformed into the additional mass moment of the branched components,and the mass moment balance equation with the additional mass moment coefficient matrix is established.When the coefficient matrix of the rotation angle in the equation is constant to zero,the dynamic balance of the combined linkage mechanism can be achieved.In order to show the contrast effect between the optimized and the pre-optimized dynamic balancing of the combined linkage driving mechanism,the GUI module in MATLAB is used to compile the total centroid change view interface of the combined linkage driving mechanism,and the centroid change image of the combined linkage driving mechanism is obtained.By comparison,it can be seen that the area of centroid change area decreases after optimization,then the mass moment is verified.The effect of dynamic balance optimization on the improvement of the combined linkage driving mechanism provides a theoretical reference for the design of the actual prototype of the combined linkage driving mechanism of embroidery machine.(4)Using AVANT MI-7008 data acquisition and analysis instrument,the vibration acceleration of embroidery machine driven by different driving mechanisms was tested.The vibration acceleration of the combined connecting rod drive mechanism and the double cam drive mechanism at the same position and speed was compared according to the sampling point test method at different locations in the speed range of 800 r/min,1000 r/min and 1200 r/min.Quantitative analysis of the vibration acceleration values at three locations in the same time period shows that the peak value of the vibration acceleration produced by the combined connecting rod driving mechanism is smaller than that of the double cam driving mechanism.Therefore,the combined linkage driving mechanism optimized by dynamic balance has more stability and meets the requirements of high-speed operation.