Failure Mechanism Of The Slide Bearing Of Granulating Machine Group

Plastic extrusion unit is a kind of mechanical equipment to produce plastic sheet and grain of material,which polyvinyl chloride(PVC)and polypropylene are used as raw material.Plastic sheet and the grain of wood can be folders,plastic cups,lunch boxes and other plastic products by further processing.In recent years,as the application and productivity of plastic products increasing,the needing of plastics machinery grows gradually.The combination of industrial automation and information technology has become the main trend in the current industrial development.Research showed that there are more than 60%of the plastic productions,which are processed by extrusion.And extrusion has become one of the most important processing method for polymer materials.In the field of extrusion,single-screw extruder appears earliest and is with the authority.But it is hard to improve the extrusion performance.The development of extruder has focus on parallel twin-screw extruder.CME-450 granulating machine group is researched by a rubber plastic factory in Dalian,which is large,differential double support,and it can extrude steadily.Also,the technology has got the advanced level.However,material pollution was found,because of the break-down of gear shaft.Failure analysis for gear shaft and bearing bush of CME-450 was studied,in this experiment.Failure form and broken-position was found through a series of tests about the friction pair of failure gear shaft and bearing bush,including macro-morphology observation,fracture morphology observation,mechanics performance tests,metallographic structure and scanning electron microscopy analysis.Results showed that:(1)Due to the temperature increasing,the material heated in the molten state.So the lubricant medium material is with low viscosity and it is difficult to form the lubrication film to take the effect of lubrication.Also,this condition aggravates the friction and wear and friction heating.The cycle of repetition leads to the failure of the bearing.(2)Adhesive wear and peeling happens when the gear shaft rubs with bearing bush.(3)Cracking forms when bearing bush rubs with the gear shaft.And adaptability of high-speed-steel-bearing bush is lower than that of silver-bearing bush.The advice is to change the high-speed-steel-bearing bush.