Bosch Connecting Plunger Design Produces an 84 Percent Cost Reduction; Chevron Phillips Chemical Material Enables Savings

THE WOODLANDS, Texas, June 21 -- When Bosch engineers went to work designing an active vacuum brake booster connecting plunger for use in sport utility vehicle braking systems, they quickly realized the part needed to be molded out of plastic. A precision cast steel part would have required extensive post machining, adding significant cost. The solution? Modifying the connecting plunger to reduce weight and cost through the use of Ryton(R) polyphenylene sulfide (PPS), a highly engineered plastic.

Bosch's connecting plunger in the vacuum booster works in conjunction with the hydraulic braking system to amplify the manual input to the brake. As a result, drivers are able to safely stop with minimal pedal pressure.

The proposed connecting plunger design was complex. Designed with a tight tolerance to prevent leakage, a resin-rich spherical radius-sealing surface was added to the end of the connecting plunger. Additionally, the ID bore sealing surface was designed to only allow a maximum draft of .07 degrees. The design also added four flexible tabs that bent to a high degree to snap over the solenoid plunger. In addition to these requirements, the entire connecting plunger had to withstand great impact during the automobile's assembly.

Bosch worked with NYX Fort Wayne, a supplier of underhood and molded interior assemblies to develop a solution. Chevron Phillips Chemical Company LP's (Chevron Phillips Chemical) Ryton(R) PPS grade R4-200BL was selected as the material of choice for its heat resistance up to 250 F, low creep resistance, good chemical resistance and wear resistance against steel and PET, and the ability to withstand great impact and high structural loads placed on the part.

The combination of NYX's tooling and Ryton(R) PPS' minimal moisture absorption and low coefficient of linear thermal expansion easily achieved Bosch's precise tolerance design requirements. Even with the precise molding, little to no flashing occurred.

As a result of this innovative design and wide collaboration, Bosch realized an 84 percent cost reduction per part by utilizing Ryton(R) PPS versus a steel component design. Additionally, rather than adding a steel part weighing 33g, the connecting plunger made of Ryton(R) PPS reduced the part's weight by 78 percent, weighing only 7g.

The Society of Plastic Engineers (SPE), named Bosch's active vacuum brake booster connecting plunger design as a 2005 Innovation Award finalist in the chassis/hardware category.

About Chevron Phillips Chemical

Chevron Phillips Chemical Company LLC with its affiliates is one of the world's top producers of olefins and polyolefins and a leading supplier of aromatics, alpha olefins, styrenics, specialty chemicals, piping and proprietary plastics. The company has total assets of approximately $7 billion and is owned equally by Chevron Corporation and ConocoPhillips. For more information about Chevron Phillips Chemical, visit http://www.cpchem.com/ .