Failure Analysis And Improvement Research On Transmission System Of Acrylic Spinning Drafting Machine

As an important chemical fiber,polyacrylonitrile fiber is widely used because of its excellent performance.China is the world's largest polyacrylonitrile fiber producer.Drawing machine is an important equipment for the production of polyacrylonitrile fiber spinning,its operation is directly related to the production and quality of polyacrylonitrile fiber products.Due to the continuous increase of spinning capacity in recent years,the drafting machine load is increasing,and the failure of its drawing shaft and main driving gear has occurred,seriously affecting the continuity and stability of spinning production.In this paper,the failure reasons of the drafting machine drive system are studied deeply,and the improvement scheme is put forward based on the failure reason of the drafting shaft and main drive gear respectively.The main contents are as follows.(1)The load distribution among drafting shafts was investigated.The working loads acted on every shaft were calculated according to the testing results of yield stress and fracture stress of polyacrylonitrile fiber.And the values of the impact loads acting on the shaft,which caused by emergency shutdown,uniformly retarded shutdown of the drafter or the accident of drafting roller twined by the fiber,were also calculated.(2)The surface topography and metallurgical analysis of the fracture surface in drafting shaft were carried out thoughtfully.The stress distribution in the shaft was investigated by FEA method and engineering calculation method under various working conditions.After that,the strength checking of the shaft was carried out to find out its failure causes,according to the admissible stress of shaft material under static load and alternate load.(3)The working loads acting on driver gear in drafting gearbox were calculated under various working conditions.Referring to the conclusion of surface topography analysis on the fracture surface in the gear,the main failure causes were determined by analyzing the stress contribution in gear tooth by FEA and engineering calculation method.(4)According to above-mentioned research conclusions,the reformation plans of drafting shaft and its driving gear were obtained after redesign calculation,to increase the margin of safety of these two components.And some accessorial measures were also applied to increase the service life of the components,considering their maintenance procedure.