Investigation of thermoforming as a method of manufacturing plastic air intake manifolds
Original Publication Date: 2001-Apr-01
Included in the Prior Art Database: 2003-Jul-23
P. K. Mallick, Dearborn: AUTHOR [+2]
Current plastic intake manifolds are manufactured using the injection molding process. In this paper, thermoforming is explored as an alternative to injection molding for making intake manifold shells, which can then be joined by one of the welding techniques used for thermoplastic materials. The idea includes press-forming experiments of a simple bowl shaped shell and subsequent welding experiments to join these shells.
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Investigation of thermoforming as a method of manufacturing plasticair intake manifolds
Idee: P. K. Mallick, Dearborn, MI (USA); P. Daly, Auburn Hills, MI (USA)
Current plastic intake manifolds are manufactured using the injection molding process. In thispaper, thermoforming is explored as an alternative to injection molding for making intake manifoldshells, which can then be joined by one of the welding techniques used for thermoplasticmaterials. The idea includes press-forming experiments of a simple bowl shaped shell andsubsequent welding experiments to join these shells.
There are many plastic intake manifolds in production today covering applications ranging fromturbo-charged diesel engines to normally aspirated gasoline engines. Current manufacturingtechnologies for plastic intake manifolds include lost core injection molding, shell injection moldingand a small number of assorted other technologies. The shell injection molding process followedby vibration welding has a lower tooling cost and is less cumbersome than the lost core injectionmolding process. As the use of plastic intake manifolds grows, the shell design becomes moreattractive because of its applicability to lower volume economies of scale.
There is now an increasing trend in integrating several components, such as fuel injection, inengine air/fuel modules. The assembly of these components is achieved via either snap fits orthreaded fasteners. Increased integration is generally associated with increasing shape complexity.The advantages of shell design in the integration approach are lower number of fasteners required(Table 1) and greater flexibility in modular design. Figure 1 shows one such integrated intakemanifold using shell design and compares it with an older lost core design.
Lost Core Shell
4 cyl 14-18 8-10
6 cyl 17-22 8-12
8 cyl 17-22 12-16
Table 1: Typical Number of Fasteners in Intake Manifold Modules
Siemens Technik Report
Jahrgang 4 Nr. 11 April 2001
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Figure 1: Photographs of lost core design (left) and shell design (right) of integrated intakemanifolds.
Thermoforming is as an alternative method to injection molding for manufacturing shells for plasticair intake manifolds. Thermoforming is a well-established manufacturing process in the plasticsindustry. It is used for making a wide variety of products in the packaging industry. It is also usedfor making business machine housings, refrigerator cabinets, automotive inner door panels,shower stalls, etc. Most of the thermoformed products have been developed with amorphouspolymers, such as polystyrene and ABS. Plastic air intake manifolds, on the other hand, use eitherpolyamide-6 or polyamide-6,6. Both polyamide-6 and -6,6 are semi-crystalline polymers, with anarrower forming window than amorphous polymers that are more commonly used forthermoforming (1). Furthermore, the intake manifold materials contain up to 35% (by weight)short glass fibers. Not much information is availabl...