Reserve Kinematics Design Of Needle Bar Driving Mechanism With Non-Circular Gear

With the development of the people’s demand for textiles,the requirement of efficiency and embroidery’s quality of computer embroidery machine is also growing.Embroidery machine industry in China is booming now.But most of the machines are at low level and it is not international famous.This situation is cause by the poor independent innovation ability of the domestic manufacturers.Their study for the core mechanism of computer embroidery machine(such as needle bar driving mechanism)is still at the stage of mapping and copying foreign products.It will not only bring infringement problems and make export to developed countries difficult.It will also make the machines hard to achieve the ideal performance.So the research for new needle bar driving mechanism with independent intellectual property rights has practical significance for promoting the technology level of domestic computer embroidery machine.Some of the domestic high-speed embroidery machine has an impact when the sewing foot driving block and sewing foot contact.In order to solve the problem,this paper mainly analyzed the kinematic characteristic of the needle bar driving mechanism and the sewing foot driving mechanism which is the core component of computer embroidery machine,and then non-circular gear combination mechanism is used in the needle bar driving mechanism to change the movement of sewing foot driving block.Through the way of theoretical analysis and test,this paper studies the kinematic characteristic of the new needle bar driving mechanism.And some design parameters is changed such as the length of the levers to optimize the smoothness of transmission ratio variation by genetic algorithm.In this paper,the main research contents and results are as follows:1)This paper analyzes the original needle bar driving mechanism and the original sewing foot driving mechanism in kinesiology.Then it is found that the sewing foot and the sewing foot driving block are in different speed when they start to contact,and it will cause impact.By changing the movement characteristics of the needle bar driving block,it can make the sewing foot and the sewing foot driving block keep same speed when they start to contact with each other.So the impact can be eliminated..The combined mechanism of non-circular gear and bar:an realize accurate designed movement characteristics of the needle bar driving mechanism.2)Based on the inverse kinematic mathematical model of the new needle bar driving mechanism,the transmission ratio and pitch curve of non-circular gear can be calculated.The pitch curve of non-circular gear will generate cuspidal point during the calculation process.The paper uses polynomial function to instead the part with cuspidal point of the transmission ratio function.So the curve can be more suitable.In order to make the mechanism work more steady and the non-circular gears easier to process,some design parameters is changed such as the length of the levers to optimize the smoothness of transmission ratio variation by genetic algorithm.The calculation can be solve with the toolbox in Matlab and the result of the optimization is that the standard deviation of the transmission ratio changes from 0.432 to 0.2012.It improves the stability of the transmission ratio change.3)The sewing foot driving mechanism is designed with the cam-linkage combined mechanism to finish the design of whole embroidery machine head.And the contour curve of the cam can be calculated through inverse analysis when the kinematic characteristic is certain.And the thread-taking-up mechanism is cam-linkage combined mechanisms.According to the distribution of other parts and movement requirement of thread-taking-up bar,the dimensions of bars are given.Then the structural design of the sewing foot driving mechanism and the thread-taking-up mechanism is finished.4)Three-dimensional structure of components on the embroidery machine is designed after finishing the mechanisms.Then the simulation of the virtual prototype is done to obtain movement characteristics of needle bar driving block and sewing foot driving block.It is found that the movement characteristics meet to the design requirements,and the design can eliminate the impact.After the parts are machined,embroidery head and needle bar frame are installed on the rack.Through the camera technology,the movement characteristics of the needle bar driving block can be obtained to verify the design.