Industry Spotlight: Automotive Customers Implement Simulation to Address Critical Issues

Even with all the current instability in the automotive industry, executives are still reporting the major issues they face have not changed much in the past few years. According to KPMG’s 2008 Global Auto Executive Survey, product quality, cost reductions, harnessing new technologies, and global competition are the major challenges, with environmental issues becoming more notable.

From a consumer standpoint there has been a definite shift in purchasing considerations over the last two years. Concerns about safety and serviceability have gone down while interest in environmental friendliness and alternative fuel sources has risen significantly.

Now, more than ever, major automakers and their suppliers are harnessing Moldflow simulation to improve their product quality, make their products more environmentally friendly, and stay competitive in their market.

Product Quality

For over 75 years Jaguar, based in Coventry, England, has manufactured vehicles that deliver a unique blend of style, luxury, and performance. As a premium car maker, they consider product quality to be paramount. According to a review in New London, Connecticut’s The Day newspaper, "Jaguar´s quality is ranked above that of its European rivals, Mercedes-Benz, BMW and Audi.” With world-class engineering talent and advanced design and optimization tools, Jaguar continues its rich and distinguished heritage of innovative automotive manufacturing.

One challenge Jaguar has had to surmount is due to the increasing number of plastic parts being used in interior, exterior, and under-hood applications. Until recently, the company had been leaving analysis of their plastic parts to their suppliers and had not been performing up-front work in-house to optimize their designs for manufacturability. This often resulted in late design changes, costly rework, and the risk of entire programs being late for crucial milestones.

On a center console finisher for their new Jaguar XF interior, they identified multiple problems in the parts coming from the original mold design. Air traps, poor fiber orientation, sink marks, and unacceptable warpage resulted in a 42% scrap rate at an estimated cost of $1 million in scrap and rework.

In an effort to address these issues as early as possible in the product development cycle, Jaguar invested in Moldflow Plastics Insight® (MPI®) software to test three different changes to the thickness in the center of the part where filling hesitation was occurring. On the third iteration, they found the optimum wall thickness that produced a uniform filling pattern, appropriate fiber orientation, and minimal volumetric shrinkage. This design iteration also removed the weld lines entirely and pushed the air traps to the edge of the component.

Once the proper wall thickness was found for the part design itself, the engineers used MPI to optimize the processing parameters and cooling system to minimize the amount of warpage that occurred in the molded part. After several iterations, the displacement in a critical area was reduced from 12.8 mm to 1.2 mm. In production, this resulted in a 13% decrease in the scrap rate due to warpage.

After the optimization, the total scrap rate was reduced from 42% to 7%, with most of the remaining scrap due to the veneer in-mold decoration. The cost savings on this project alone due to the reduced amount of scrap and improved production efficiency is estimated at over $1.1 million.

In total, 181 new plastic component designs were validated and optimized for the new Jaguar XF sport sedan using MPI software. With the successful implementation of MPI, Jaguar is now able to fully control the part and mold and ensure the designs of each are fully optimized. Their dependency on suppliers to get it right has been minimized along with the number of late design changes, the amount of rework, and the risk of programs missing their set milestones.

Environmental Friendliness

Over the past twenty years, automakers have made evolutionary gains in fuel efficiency from improvements and innovations in powertrain design. However, these improvements have been countered by increases in vehicle weight because of the use of higher strength steels and other heavy safety features such as airbags. For example, a 2008 Chevrolet Cobalt with significant improvements in engine efficiency still gets the same mileage as a similar 1988 model, because the Cobalt weighs 17% more.

To address environmental concerns, many automotive component manufacturers now are focusing on finding ways to reduce carbon dioxide emissions by optimizing their plastic part designs to reduce mass while still maintaining product performance and quality. This strategy not only helps improve fuel economy of the vehicles in which their parts are installed, but it also reduces the consumption of raw materials, the energy needed for manufacturing, and the need for replacement parts.

Promold, an engineering consultancy firm based in Paris, France, offers MPI analysis services to their customers. Promold was contracted by Valeo, a major supplier of automotive components to well-known vehicle manufacturers, to optimize the design of a new headlamp housing for a Renault sedan. The initial design weighed 244 grams with a wall thickness of 2.15 mm. The constraints for manufacturing were that the parts must be produced on an 800-metric-ton molding machine and there could be no weld lines in the vicinity of where the primary headlamp bulb would be installed.

Promold used MPI software to virtually experiment with three material options (polycarbonate, nylon, and PBT), five different part thicknesses ranging from 2.15mm to 0.8mm, and six different gating configurations. The experiment was set up to use the full capacity of the designated molding machine’s 174 MPa maximum injection pressure so the wall thickness could be reduced as much as possible. The first step was to evaluate the three materials based on their flow characteristics to minimize the pressure required to fill the part. Next, the wall thickness and number of gates were optimized simultaneously to ensure the parts did not exceed the injection pressure limit of the machine and no weld lines were created in critical areas.

The experiment resulted in the selection of the PBT material for a design with a wall thickness of only 1.2 mm that used a 5-gate hot-runner system. The final weight of the part was 41% less than the original design and took advantage of the full capability of the molding machine used. Performance and quality criteria were also met, with no weld lines in any critical areas of the part and no sacrifices in strength due to the thinner walls.

Obviously, saving 100 grams in the weight of a headlamp housing is not going to have a significant effect by itself on the fuel economy of a vehicle. However, with plastics approaching 10% of the average total vehicle weight, incorporating these methods into the best practices of an organization will ensure that all new products developed will be optimized for mass, and taken together, they can have a sizable impact on a vehicle’s fuel efficiency. Also, less material consumed and reduced amounts of energy required during production present opportunities for cost savings in conjunction with improved environmental friendliness.

Going Forward

Executives and directors in all major automotive companies have recognized the importance of using simulation to stimulate innovation and to get products to market as fast as possible. Those that have implemented Moldflow injection molding simulation software have seen great success in improving product quality and increasing environmental friendliness of their plastic products, as the examples described here have shown.

Carlos Ghosn, CEO of Renault and Nissan, is largely credited with the complete turnaround of Nissan since 2005. Ghosn outlines a strategy of, “…using less and less prototypes, more digital simulation to decrease time-to-market,” in his company’s 2009 Strategic Plan.

“Product development is now commodity, you must introduce product optimization and a real time ‘analytical vision’, if not, your competitors will,” notes John L. Sullivan, Ford’s Director of Process, Methods, Tools, and Information at a recent CAE conference.

Going forward, companies in the automotive industry, in particular, can benefit from using simulation throughout development to optimize every plastic product they produce. The greatest potential benefits come from moving beyond using simulation just to discover and avoid potential problems and instead using simulation to truly optimization designs to address criteria that have been identified as mission-critical to their businesses.

Moldflow’s vision of enterprise-enabled simulation (see cover story) supports the immediate needs of the automotive industry by providing a methodology that enables everyone involved in new product development, from industrial designers to process engineers, the ability to perform analyses and improve the design early and often. This type of implementation allows for the designs to be tailored to whatever the best practices of the organization dictate, whether it be product quality, environmental friendliness, time-to-market, or any trend currently shaping the industry.