Before assembling, shaping and curing, tire treads are produced by continuous extrusion. Control of the extrusion process is critical in order to obtain the prescribed shape and properties at reasonable expense. Increasingly, tire manufacturers are succeeding with numerical modeling of rubber extrusion to improve their die geometries and processing conditions, while reducing the number of experiments on the production line

POLYFLOW modeling reduced the number of experimental trials required to produce a specified tread profile by 50%.

Industrial Partnership

In a project partially funded by the European Commission,3 POLYFLOW has been successfully applied and validated for the prediction of tire tread rubber extrusion. Alliance Tire Company, Ltd. provided the benchmark measurements used to validate POLYFLOW against actual industrial data. Apex Technology, FEM++ and Polyflow s.a. provided expertise in the usage of the software for rubber extrusion applications, and the Technion offered access to parallel computing resources. The project is the first one of its kind, in which actual industrial data on tire extrusion has been made available for CFD validation.

Design Trials Reduced

First, the study looked at single material tread extrusion. The POLYFLOW results showed very good agreement with the experimental measurements of the main quality parameters used for evaluation (within 11% for the pressure and 10-14% for the geometrical dimensions). The next task involved a coextrusion simulation. This, too, showed a good agreement with the experimental measurements (around 10% for the geometrical dimensions). Finally, the project evaluated POLYFLOW's die design tool for single material extrusion. By predicting the die shape required for a given extrusion, this phase of the project reduced the number of necessary experimental trials by 50%.

Faster Time to Solution

The performance of the new multifrontal (MFR) solver in POLYFLOW 3.6 provided excellent speed during the calculation phase of the project (up to 4.5 times speedup for the largest model size). This enabled simulation of a complex model on a single processor, while parallel processing generated results for the simulation during overnight runs.

Growing Interest in Modeling

As a result of the project, Alliance Tire Company uses POLYFLOW in their production process in order to improve performance and gain understanding. Other tire companies are also expressing increased interest in the POLYFLOW capabilities validated by the project.

1 "Extrusion Modeling of Tire Components", J. Dheur, Goodyear Technical Center, in Proceedings of the IRC-97 conference, Nuremberg, July 1997

2 "Numerical Prediction of Extrudate Swell of Rubber Compounds", E. Slachmuylders, Manufacture Michelin,
poster presented at the 1997 POLYFLOW Users Meeting, Brussels, October 1997

3 ESPRIT initiative, project TTN@GMD number 24462. URL http://www.apex-technologies.fr/tread

Pressure distribution during single material tread extrusion.

Velocity distribution during coextrusion of two materials.

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