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Engineering thermoplastics are widely used in a variety of automotive components systems because of their excellent balance of mechanical performance, design flexibility, aesthetics, parts integration, and low specific gravity. This combination of properties allows for the creation of highly integrated modules, which can increase assembly efficiency and reduce mass, part count, warranty and ergonomic issues, and systems costs. As a result, the use of engineering thermoplastic materials can enhance market competitiveness at a time of increased global competition. To evaluate the economic advantages of polymers in a specific vehicle system, a design for assembly (DFA) case study was conducted with the goal of determining the variable system cost case for a generic thermoplastic door module system vs. conventional-build door systems based on assembly savings gains. This paper will describe the study and show the results achieved.

Automotive styling and performance trends continue to challenge engineers to develop cost effective bumper systems that can provide efficient energy absorption and also fit within reduced package spaces. Through a combination of material properties and design, injection-molded engineering thermoplastic (ETP) energy absorption systems using polycarbonate/polybutylene terephthalate (PC/PBT) alloys have been shown to promote faster loading and superior energy absorption efficiency than conventional foam systems. This allows the ETP system to provide the required impact protection within a smaller package space. In order to make optimal use of this efficiency, the reinforcing beam and energy absorber (EA) must be considered together as an energy management system. This paper describes the development of a predictive tool created to simplify and shorten the process of engineering efficient and cost effective beam/EA energy management systems.

Because it is common to attach plastic parts to other plastic, metal, or ceramic assemblies with mechanical fasteners that are often stronger and stiffer than the plastic with which they are mated, it is important to be able to predict the retention of the fastener in the polymeric component. The ability to predict this information allows engineers to more accurately estimate length of part service life. A study was initiated to understand the behavior of threaded fasteners in bosses molded from engineering thermoplastic resins. The study examined fastening dynamics during and after insertion of the fastener and the effects of friction on the subsequent performance of the resin. Tests were conducted at ambient temperatures over a range of torques and loads using several fixtures that were specially designed for the study. Materials evaluated include modified-polyphenylene ether (M-PPE), polyetherimide (PEI), polybutylene terephthalate (PBT), and polycarbonate (PC).

There are a multitude of opportunities to utilize two-shot or overmolding technology in the automotive industry. Two-shot or overmolding a thermoplastic elastomer onto a rigid substrate can produce visually appealing, high quality parts. In addition, use of this technology can offer the molder significant reductions in labor and floor space consumption as well as a reduction in system cost. Traditionally, two-shot applications were limited to olefinbased TPE's and substrates, which often restricted rigidity, structure and gloss levels. With the development of thermoplastic elastomers that bond to engineering thermoplastics, two-shot molding can now produce parts that require higher heat, higher gloss and greater structural rigidity. This paper will outline engineering thermoplastics that bond with these new elastomers, discuss potential applications, and review circumstances that offer the best opportunity to call upon the advantages of two-shot and overmolding technology.

The instrument panel (IP) is one of the largest, most complex, and visible components of the vehicle interior, and like most other major systems in passenger cars and light trucks, it has undergone considerable aesthetic and functional changes over the past decade. This is because a number of design, engineering, and manufacturing trends have been driving modifications in both the role of these systems and the materials used to construct them since the mid- '80s. This paper will trace the recent evolution of IP systems in terms of the trends affecting both design and materials usage. Specific commercial examples will be used to illustrate these changes.

The thermal performance of an automotive forward-lighting assembly is predicted with a computational fluid-dynamics (CFD) program. A three-dimensional, steady-state heat-transfer model seeks to account for convection and radiation within the enclosure, conduction through the thermoplastic walls and lens, and external convection and radiation losses. The predicted temperatures agree well with experimental thermocouple and infrared data on the housing. Driven by the thermal expansion of the air near the bulb surface, counter-rotating recirculation zones are predicted within the enclosure. The highest temperatures in the plastic components are predicted on the inner surface of the shelf above the bulb where airflow rising from the hot bulb surface impinges.

As the global auto industry wrote the final chapter on its first century, we saw the average thickness of an automotive instrument panel drop from 3.0 mm-3.5 mm to 2.0 mm-2.3 mm, as found in the 1999 Volkswagen Jetta and Golf. By reducing the wall thickness of the instrument panel, Volkswagen started an industry trend: both OEMs and tiers are investigating technologies to produce parts that combine a lower cost-per-part via material optimization and cycle-time reduction with the superior performance of engineering thermoplastics. The goal is to produce parts that are positioned more competitively at every stage of the development cycle - from design, to manufacturing, to assembly, to “curb appeal” on the showroom floor. The key to this manufacturing and design “sweet spot” is a technology called thinwall - the molding of plastic parts from engineering thermoplastics with wall thicknesses thinner than conventional parts of similar geometry.

Use of thermoplastic materials for throttle body applications can offer substantial weight, cost, and integration benefits. This paper will discuss the many elements that comprise materials selection, as well as the design and testing of composite throttle bodies. Polyetherimide (PEI), polyphenylene sulfide (PPS), and polybutylene terephthalate (PBT) materials will be discussed and compared as candidates for automotive throttle bodies. The focus areas that will be covered in this paper include: Materials Selection - The criteria for materials selection will be discussed and the properties of candidate thermoplastics compared with key requirements of throttle body applications. Bore and Plate Dimensional Stability and Consistency - The effects of thermal cycling, coefficient of thermal expansion, humidity, and design will be discussed, as well as their relation to bore/plate air leakage.

The automotive industry is continually striving for opportunities to take additional cost and mass out of vehicle systems. Large parts such as an Instrument Panel retainer are good candidates because a small percent reduction in mass can translate into a significant material mass savings. Multiple requirements for a soft instrument panel including safety, stiffness, adhesion, etc. can make these savings difficult to achieve. This paper will describe how a new material and process development for the fabrication of a soft instrument panel can produce 50% weight savings with a 20% cost reduction potential. In addition, this new technology exhibits improved performance over existing materials during safety testing.

This paper examines a variety of thermocouple and infrared measurement techniques as means of obtaining accurate and consistent temperature measurements within a headlamp system. While measuring temperature is straightforward in principle, in practice, these measurements are fraught with potential error. The paper summarizes a succession of experiments conducted at our Parts Design Center (formerly the Application Development Resource Center) in Pittsfield, MA. These experiments lead to the ability to accurately measure temperature at a given location within a lamp assembly. Using these studies and the resulting transfer functions as a foundation, a Design of Experiment (D.O.E.) is presented which explores the effect of a variety of headlamp design factors on the surface temperature of a headlamp reflector at a given location.

Gas-assist injection molding is a relatively new process. It is an extension of conventional injection molding and allows molders to make larger parts having projected areas or cross sectional geometries not previously possible using existing equipment. However, controlling the injection of the gas has been a concern. The plastics industry is attempting to establish logical techniques to set up and rationalize processing conditions for the method. Although gas injection equipment permits a number of adjustments, an optimum processing window must be established to provide control and repeatability of the process to mold consistent, acceptable parts. This paper describes a strategy and equipment for rationalizing and accurately controlling gas injection processing conditions that are applicable regardless of the type of molding machine or processing license a molder is using.

Basic automotive steering wheel armature design has been largely unchanged for years. A cast aluminum or magnesium armature is typically used to provide stiffness and strength with an overmolded polyurethane giving shape and occupant protection. A prototype steering wheel armature made from a unique recyclable thermoplastic eliminates the casting while meeting the same stiffness, impact, and performance criteria needed for the automotive market. It also opens new avenues for styling differentiation and flexibility. Prototype parts, manufacturing, and testing results will be covered.

An efficient energy absorber (EA) will absorb impact energy through a combination of elastic and plastic deformation. However, the EA is typically coupled with a steel reinforcing beam, which can also elastically and plastically deform during an impact event. In order to design and optimize an EA/Beam system that will meet the specified vehicle impact requirements, the response of the entire assembly must be accurately predicted. This paper will describe a finite element procedure and material model that can be used to predict the impact response of a bumper system composed of an injection molded thermoplastic energy absorber attached to a steel beam. The first step in the process was to identify the critical material, geometric, and boundary condition parameters involved in the EA and Beam individually. Next, the two models were combined to create the system model. Actual test results for 8km/hr.

As automakers struggle to meet often conflicting safety, weight, styling, and performance requirements, engineering thermoplastics (ETPs) are making increasing inroads into applications that once were the exclusive domain of metals, glass, and thermosets. A good example of this is in the door systems area, where the performance, design flexibility, aesthetics, parts integration, and lower specific gravity offered by ETPs are allowing highly integrated and efficient modules to be created that, in turn, increase assembly efficiency and reduce mass, part count, warranty issues, and systems costs. This paper will use several case studies on innovative door hardware modules and door panels to illustrate the advantages offered by this versatile class of engineering materials.

This paper discusses a Design for Six Sigma (DFSS) based methodology for designing an injection molded bumper energy absorber to help meet vehicle pedestrian protection requirements. The development process is described, and an example is presented of its use in designing an injection molded energy absorber for a range of various vehicle styling parameters. First, an idealized set-up incorporating the car styling parameters critical for pedestrian protection requirements was developed. Then, the vehicle and Energy Absorber (EA) geometries were parameterized and a DFSS process was employed to investigate the design space using Finite Element Impact Analysis with a commercially available Lower Leg Form Impactor.

The drive to reduce weight, simplify assembly, and cut total system cost in today's vehicles is relentless. Replacing metal systems with thermoplastics has been of considerable interest in the engineering community. The current generations of engineering thermoplastic resins are enabling the use of plastic systems in demanding underhood applications. Technical data and discussion regarding the materials, design, molding, and assembly of lightweight composite throttle bodies will be presented in this paper. Comparisons with machined aluminum throttle housings are drawn to establish a baseline with the throttle body housing component that is most common in production today. Design flexibility and process simplification are some of the approaches highlighted. Much of the technical information provided in the paper applies to both cable driven mechanical throttle bodies as well as electronic throttle bodies under development.

Current accelerated weathering protocols such as SAE J1960 or ASTM G26 do not provide reliable, predictive results for engineering thermoplastics. Correlation factors among resin types and even different colors of a single resin have variations that are 60-100% of the mean at the 95% confidence level, making these tests useless for lifetime prediction or even reliable ranking of materials. We have developed improved conditions using CIRA/sodalime-filtered xenon arc, a more rain-like water spray, and occasional sponge-wiping of the samples. The data for gloss loss and color shift agree very well with Florida data giving a correlation factor of 3100±680 kJ/m2 (at 340 nm) per Florida year at the 95% confidence level. The acceleration factor is 7.6x.

The first single-piece, injection-molded, thermoplastic, front bumper for a light truck provides improved performance and reduced cost for the 1997 MY Explorer® Ltd. and 1988 MY Mountaineer® truck from Ford Motor Company. Additionally, the system provides improved impact performance, including the ability to pass 5.6 km/hr barrier impact tests without damage. Further, the advanced, 1-piece design integrates fascia attachments, reducing assembly time, and weighs 8.76 kg/bumper less than a baseline steel design. The complete system provides a cost savings vs. extruded aluminum and is competitive with steel bumpers.

Textron Automotive Trim, Valeo Climate Control, and Torrington Research Company, with assistance from GE Plastics, have developed an integrated instrument panel system to meet ever-increasing industry targets for: Investment and piece-cost reduction; Mass/weight savings; Quality and performance improvements; Packaging and space availability; Government regulation levels; and Innovative technology. This system, developed through feedback with the DaimlerChrysler Corporation, combines the distinctive requirements of the instrument panel (IP) with the heater-ventilation-air-conditioning (HVAC) assembly. Implementing development disciplines such as benchmarking, brainstorming, and force ranking, a number of concepts were generated and evaluated. Using a current-production, small, multi-purpose vehicle environment, a mainstream concept was designed and engineered.

The purpose of this paper is to discuss design methodology, manufacturing considerations, and testing proveout for a prototype gas-assist-molded, energy-absorbing, glovebox door program. The design used a single gas pin mounted in a multiple-gas-channel component and an internal gas manifold to form an efficient energy absorbing system. The end goal for the development program was to manufacture a glovebox door in a system that could meet the customer's targets for cost, surface appearance, and safety considerations without degrading function and fit. This paper will discuss the ability of a design methodology to predict actual component performance using engineering calculations, analytical tools, and prototype testing/molding during the development.