Simulating sole design optimization

A new, user-friendly software system, which simulates the injection molding of smartLite® materials, allows specialized molders to finalize their sole and mold designs before investing in tooling, trials or machine modifications. Developed by Huntsman Polyurethanes with the Institute for Plastics Processing (IKV) and Simcon, the system reduces prototyping time, improves efficiency and accelerates the market introduction of new soling styles. 

The new software, devised and owned by Huntsman, and “powered” by Simcon’s Cadmould programme, allows molders to incorporate interesting design features, predict the filling pattern, position the injection points correctly and achieve soles with the required final properties at the lowest possible density. It can also help to prevent unsightly marks caused by air traps or, in the case of two injection points, an unfavorable location of weld lines.

By testing several critical factors and making adjustments to the tooling or part before cutting in metal, the simulation software helps smartLite customers cut costs and reduce time to market – important aspects for innovative molders in the fast-moving footwear business.

The package covers all the measurements and model fittings needed for accurate simulations of the mold filling behaviour of smartLite materials, under production conditions.  The new tool simulates the mold to include the filling pattern, injection pressure, density distribution and other critical factors for optimising a given part of, or the process itself.

smartLite materials are based on a combination of blowing technologies, which result in lightweight, good-looking soles with high performance characteristics.  During the initial stages of the injection molding process, only part of the mold cavity is filled. The blowing gas, combined in the smartLite pellets, is released during this process, creating bubbles in the thermoplastic material and expanding the melt to fill the remainder of the space.

“Introducing a simulation tool for smartLite materials meant pioneering new developments in mold flow analysis because until now no such software was available for thermoplastic foams,” says Jan Vandenbroeck, Modelling and Simulation Team, Huntsman Polyurethanes. “It required detailed research into how the melt flows while expanding and how the bubbles influence the flow of the material.”

Pressure, temperature and viscosity of the melt as well as injection speed and filling degree, all have an influence on the density distribution and bubble size, which are of key importance for the quality of the molded sole.  A new model involving chemistry, polymer physics and mathematics had to be developed to take advantage of the bubble growth and control it with the help of computational fluid dynamics (CDF).  In this preliminary research project, Huntsman collaborated with the Institute for Plastics Processing (IKV) at Aachen, Germany.

Simcon, a German software developer specializing in injection molding simulation, then implemented the resulting smartLite modelling module. This was achieved by linking the bubble growth model with a two-and-a-half dimensional (2.5D) flow simulation approach from Simcon’s Cadmould program. The final tool is a user-friendly software package with fully automatic mesh generation that runs on standard PCs and allows easy import of existing CAD geometry data. 

CFD and other computer assisted engineering (CAE) programmes rely on precise representations of material behaviour - the theory, equations and measurement of data needed to make the simulation run correctly. The high accuracy of the smartLite optimisation aid was verified in a number of tests by comparing experimental results with simulations. It was shown that the software realistically predicts the filling behaviour and the density and bubble size distribution of the blown material during the injection molding process.

For further information visit www.smartLite.biz. The animated site displays technical and machine specifications, the technology’s features and benefits, together with information on the smartLite alliance.

Editors’ notes
Huntsman is a global manufacturer and marketer of commodity and differentiated chemicals. Its operating companies manufacture basic products for a variety of global industries including chemicals, plastics, automotive, aviation, footwear, paints and coatings, construction, technology, agriculture, health care, textiles, detergent, personal care, furniture, appliances and packaging.  

Originally known for pioneering innovations in packaging, and later, rapid and integrated growth in petrochemicals, Huntsman today has revenues of $11.5 billion, 11,300 employees and 62 operations in 22 countries. The world's most significant and essential industries rely on Huntsman businesses to manufacture basic products for a variety of end-use applications.

Statements in this release that are not historical are forward-looking statements. These statements are based on management’s current beliefs and expectations. The forward-looking statements in this release are subject to uncertainty and changes in circumstances and involve risks and uncertainties that may affect the company’s operations, markets, products, services, prices and other factors as discussed in the Huntsman companies’ filings with the Securities and Exchange Commission. Significant risks and uncertainties may relate to, but are not limited to, financial, economic, competitive, environmental, political, legal, regulatory and technological factors. Accordingly, there can be no assurance that the company’s expectations will be realized. The company assumes no obligation to provide revisions to any forward-looking statements should circumstances change, except as otherwise required by securities and other applicable laws.

smartLite® is a registered trademark of Huntsman International LLC in one or more, but not all, countries.