Simulation Of Co-extrusion Of Tire Tread Compound

Today the car has become an essential means of transport.As an important component of car tires,tread should have high strength and good flexibility to bear the load and vibration when the car is in use.Co-extrusion molding technology is widely used to produce tire tread because of its low cost and high production efficiency,however,tread rubber composite mold design is so difficult that the "trail and error"method is used for die design.This design method takes a long time and costs high,need to repeatedly adjust the design with great blindness and other shortcomings,so the quality of the die can not be guaranteed and predicted.At present,there are few studies on co-extrusion simulation of tire tread national and abroad.In this paper,the Polyflow software is used to study the two tire compound flowing in the die co-extrusion process and the method of extrusion die structure improvement.The conclusions are as follows:The structure of the prefabricated die plates has a great influence on the extrusion process.The prefabricated die plates and the die plates are used as the modeling domain for the modeling,which is closer to the actual production.The speed distribution of the compound becomes more and more uniform after the compound get out of the die plates.The maximum velocity value of the velocity peak area is decreasing,and the shear rate reaches the maximum point where the preformed plate is in contact with the die plate.Wall slip coefficient,inlet flowrate ratio have a significant impact on the head pressure,extrusion expansion ratio,co-extrusion interface,the speed distribution within the mold in the co-extrusion process.As the wall slip coefficient decreases,the head pressure in the upper and lower runners decreases and the velocity distribution becomes more uniform.In the actual production the improvement of the wall smoothness can benefit improving the co-extruded tread surface quality and improving production efficiency.With the increase of the inlet flow rate of rubber compound in the lower runner,the expansion ratio of the upper rubber compound decreases,and the extrusion ratio of the lower rubber compound increases,and the overall expansion ratio remains constant.The change of the inlet flow ratio has a great influence on the co-extrusion interface position,and has little effect on the profile of the coextruded cross section.A reasonable match for the inlet flow rate of two co-extruded materials can improve the production efficiency under ensuring the quality of the extrudate.When the flow rate of tread compound in the upper layer remains unchanged and the flow rate of tread compound in the lower layer is adjusted,it is advisable to adjust slightly the inlet pressure of the upper channel to ensure the stability of the extrusion.A method of designing the prefabricated die plate structure can achieve the parametric design and the reverse die extrusion design method is used to design the prefabricated die plate structure.For the extrusion of complex products,the uniformity of the flow velocity of the prefabricated die plate can be improved by using both the inlet expansion channel and the additional damping block,however,the height of the damping block needs to match the depth of the flow path.The reverse prediction function of Polyflow software is helpful to obtain a more reasonable die plate structure.It has unique advantages in the design of extruder mold with complex extrusion section,which can greatly reduce the number of die repair times and save time and money,improve the production efficiency and has strong research and application value.