User Story

Dow Automotive : C-MOLD

Frankfurt, Germany is Dow Automotive's center for operations in Europe. Its customers include BMW, DaimlerChrysler, VW, Audi, Renault, and others, as well as Tier 1 suppliers. Padraig Naughton, project engineering leader, is responsible for application development including concept design, structural engineering, and process optimization. Among a number of software packages used to develop plastic components, Naughton uses C-MOLD for plastic injection molding simulation. In the automotive industry, Dow is working with companies that are used to engineering with metals. More and more companies are beginning to use plastics to reduce system weight and costs. The challenge is to define how to balance the properties of plastics between impact, flow, heat resistance, and mechanical properties, all of which are totally different to steel.

Naughton says, "The challenge is to develop the right grade to obtain an optimal balance for the application. My department approaches it from the point of view of the application, optimizing the application for easy processing, and the total system to meet specifications such as crash worthiness."

Like most manufacturers, Naughton is faced with tough customer requirements - reduced costs and weight, safety, and consistent quality. Dow Automotive helps its customers design their applications and processes to reduce the total system costs and weight, often though integration of parts and process optimization. "We also have extensive capabilities in engineering for safety," adds Naughton. "The Dow products combined with optimized, stable process design provide the consistent high quality."

Naughton uses a range of software products to meet customer needs. For structural design, he uses static analysis software such as ABAQUS and NASTRAN. LS-DYNA 3D is used for dynamic and impact analysis. A range of products, including C-MOLD and Moldflow, is used for process design.

C-MOLD software from C-MOLD (Louisville, KY) is used as an aid to design tools and layout injection systems for normal injection molding, gas injection, and injection-compression molding. "C-MOLD is a very useful aid to design tool layouts, optimize flow, and reduce costs for development by getting the results right the first time," notes Naughton. "Clamp tonnage, processing pressures and temperatures, cycle times, and end product properties are the main concerns. The modular approach used by C-MOLD allows the use of the same model to compare normal injection molding, gas assist, and injection-compression. The technology allows further analyses of cooling, shrinkage, and warpage to determine the total performance of the process. One of the biggest questions we face is determining the size of the injection-molding machine to fit a particular part. Using C-MOLD we can predict the machine we need to use. If we can redesign the part or the tool layout to fit on a smaller machine, it means cost savings."

C-MOLD is currently being used as an integral tool in developing molds for injection-compression molding of car interior door panels. Naughton is using C-MOLD to determine the layout of the injection system, compare materials to determine the best fit to the process, and pinpoint the critical areas in the tool in terms of high temperature, pressure, and shear - all will have adverse effects on the skin.

"When we initially implemented the C-MOLD Injection-Compression module, I first looked at a simple component, a circular disk. I was able to 'see' what happens inside the tool, how the system works, and compared it with some documented testing and results," says Naughton. "The C-MOLD results compared very well. By 'getting inside' the tool, I can check temperatures and pressures at any location. That gives you a real insight to the whole process.

"We selected C-MOLD because of its broad range of simulation capabilities including injection molding, gas assist, injection-compression, cooling, shrinkage, and warpage within just one package using the same interface and the same models," says Naughton. "We found that C-MOLD is based on sound mathematical principles that tend to provide good results even when we deviate from standard materials and processes."

While time to market advantages are often difficult to quantify, since Dow Automotive conducts at least filling analyses for most parts, typically, the company realizes significant reductions in time and money particularly in the areas of re-machining and making modifications. Naughton adds, "The major benefit we have found when using filling analyses is the optimization of the tool layout for clamp tonnage. The layout and filling of the tool have a huge effect on the clamp tonnage required.

"On some occasions, we have been able to reduce the requirement to half of the initial expected clamp requirement. This has a significant cost implication and can mean the difference between a molder being able to take on a job or not, due to machine availability. We have developed extensive experience in predicting the clamp requirements based on the simulation. The analysis itself does not always give accurate predications but with some experience is a good tool to estimate the machine requirements."

Naughton says that virtual prototyping will continue to be an important factor for manufacturing. CAE is being applied to increasingly more product development efforts. "The goal," says Naughton, "is to progress directly to production tooling without the need to produce several prototype tools. C-MOLD will play a vital role in this trend. In addition, the trend toward integration of parts and extension of functionality also presents a challenge in terms or processing. The low pressure molding process, in all its forms, is becoming more popular in the automotive industry due to the integration of skin and foam in the process. Simulation of this process through C-MOLD will play an important role in determining the optimum tools layout, material, and processing requirements. Some developments in the software are still required to fully meet the needs for this process, but the basics are there and are already helping us design tools."

Author: Laura Carrabine

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