Study Of The Extrusion Simulation Of Auto Sealing Strip Of Rubber

Auto sealing strip of rubber is produced through extrusion process with composite of EPDM rubber mixture. Extrudate swelling is widely represented in rubber extrusion, which induces deformations in the extruded profile, and requires die corrections to obtain the target product. Until recently, die designing for rubber extrusion has been largely dominated by empirical know-how and repeated trials to improve on the initial designs. But it often leads to non repetitive moulds and results, even high cost and time consuming. If the rubber extrusion and profile forecast and die optimization can be simulated with computer, then trial cost and time consuming can be saved much, and product quality can be improved too, which has important significance to promote the development of industry of Auto rubber sealing . Until present, the opening publications in the field of computer simulation of rubber sealing extrusion were not much, and most of them were limited to the local analysis of melt flowing of simple profile. Even in the world famous companies of Auto sealing systems, to design the extrusion die by simulation are also a big difficulty, which has a far distance to be used practically.In the base of above background, in this project, the extrusion processing and die design of sealing strip of EPDM were studied with Polyflow simulation. A whole analysis method was set up including rubber rheological properties testing, rheological model studying, extrusion simulation, extrusion die designing, and test verification with real rubber profile.The rheological properties of EPDM composites were tested with RH7-2 Capillary Rheometer and Gemini200 Flat-plate Rotational Rheometer. The test results showed that the storing modulus of EPDM composites was far bigger than their loss modulus in dynamical shear flowing field of small vibration amplitude, elasticity is the main response. In the steady flowing, the elasticity of EPDM composite was very weak and can be omitted. The Bird-Carreau viscosity model met the rheological properties in the steady flowing of EPDM composites very well.From the extrusion simulation of several rubber sealing strips, the influence of wall slip, traction velocity and flux to extruding status were analyzed detailedly. The results showed wall slip had big influence to extrudate. Bigger traction velocity induced smaller extrudate, and bigger flux induced bigger extrudate. For the purpose of getting the same extrudate, the adjust of flux and traction velocity accorded with the direct linear relation. Although the simulation result with PTT visco-elastical model was more accordant with the reality than the result with Bidr-Carreau viscosity model, but the elasticity was still weakly. In real application, for the complex profile, because of the limitation of calculational methds, software and hardware, time and cost, it is more reality to use viscosity model for simulation.Synthesizing the above studies, on the one hand, uniting with flux balance principle and direct extrusion simulation, a new way of designing die structure was set up. On the other hand, a new way of inverse designing the extrusion die shape was set up according to the velocity rearrange principle. Moreover, it was found that the adaptive flow channel with variational cross section was better than the straight flow channel with single cross section, because the extrusion pressure of the former was smaller and then saving energy consuming.Important achievements were acquired after the application of the above studies to solve problems in the real production. For example, from solving the vulcanization of EPDM composite inside the extrusion head, the place of vulcanization was found, and then a new flow channel structure was designed. Through the flux balance principle, a new extrusion head was designed to solve the problems of vulcanization, high extrusion pressure, uneven temperature distribution and low efficiency, which was used successfully in the extrusion line-6 of Shanghai Saic-Metzeler Sealing Systems Corporation(4S company). These applications showed that the studying of this project has reached the real application, and start a new phases of CAE simulation applied in rubber extrusion field in domestic rubber seal industry.The innovations of the present research work are listed as follows:With CAE simulation technology, a set of digital designing way of extrusion die of auto rubber seal was brought forward, then uniting CAD/CAM technology, the integrated 3C(CAD/CAE/CAM) system of designing, simulation and manufacturing of extrusion die was set up. The detailed innovations are the follow 5 sides.1 Analysis of rheological model of EPDM compositesFrom the comparison of the simulation results of viscosity model and visco-elasticity model with test result, it is shown that EPDM composites has high viscosity and low elasticity in the steady shear flowing field. Which supplyed the proof of using viscosity model in the EPDM composite extrusion simulation, and avoided problems of using visco-elasticity model.2 Process analysisThrough the simulation of extruding flowing of complex rubber seal, the relationship of wall slip, flux, traction velocity and extrudate swelling was gained, which was useful to instruct the debugging of the extrusion process. 3 Design of flow channel of extrusion dieWith flux balance principle and direct simulation, a new way of designing quantificationally the flow channels's size, shape and depth was set up.4 Design of extrusion die lipWith velocity rearrange principle, direct simulation, inverse simulation and die lip expansion, a new way of designing quantificationally the extrusion die lip of rubber seal was set up.5 Application.1) Solving the vulcanization inside the extrusion head:Through analyzing the vulcanization area inside the extrusion head, the extrusion head used in 4S company(Huai an Subsidiary) was optimized to solve the vulcanization problem.2) Design of new extrusion head:Through the flux balance principle, a new extrusion head was designed and used in the extrusion line-6 of Shanghai Saic-Metzeler Sealing Systems Corporation(4S company) and acquired good results...