The trend of manufacturing
engine oil pans from plastic instead of metals such as aluminum is continuing
to gain ground. For historical reasons, the plastic of choice to date has almost
always been polyamide 6.6. However, newer designs are favoring polyamide 6, an
alternative that offers a similarly high-quality property profile, but is much
more economical. The latest design of this type is the oil pan module for the
new six-cylinder boxer engines of the Porsche 911 Carrera, which is being
manufactured using Durethan from Lanxess.
“The component fully satisfies the specific
requirements for functional integration, lightweight construction and
cost-effective production that the new generation of engines has to meet,”
explains Jorge Soares, project manager for the highly complex component at
Polytec Plastics Germany GmbH & Co KG, which is based in Lohne. The oil pan
module has been developed in close collaboration between Polytec and Porsche.
Material data for development partners
In a study carried out for
Porsche, Lanxess proved the feasibility of manufacturing motor oil pans from
polyamide 6. For example, aging tests were carried out to determine the
durability of the thermoplastic under exposure to elements such as new and used
engine oil. Specimen storage tests spanning a total of 3,000 hours at 150 °C
were performed on highly reinforced, hydrolysis-stabilised, easy-flowing and
high-temperature-stabilised Durethan grades, among others. “The test results
show that the aging behaviour of heat-stabilised polyamide 6 is only marginally
different to that of heat-stabilised polyamide 6.6 in terms of tensile
strength, Young's modulus, elongation at break and impact strength. Appropriately
optimised polyamide 6 compounds are therefore ideally suited for use in
components that convey engine oil,” says Christof Boden, expert for engine
compartment applications from Lanxess. The specialty chemicals company is
making the test results – and other material data – available to development
partners as part of joint projects. Furthermore, customers are supported
through every stage in the development of an oil pan as part of the HiAnt
customer services package. This brand incorporates HPM's extensive material,
simulation and processing competence, which it offers to customers through all
stages of component development. Services include, for example, simulating mold
filling including warpage calculation, simulation of stone impact and sealing
forces, or testing of components with regard to sealing gap expansion and stone
impact.
Greatly simplified production and installation
The engine oil pan for the
Porsche 911 Carrera consists of an upper and a lower part made from 30 percent
glass fibre-reinforced Durethan BKV 30 H2.0 from Lanxess. The upper part is
screw-connected to a pipeline carrier that is also made from polyamide 6. Using
plastic instead of aluminium means that numerous functions can be shaped
directly during injection moulding, thereby integrating them into the
component. This has helped to reduce the number of separate parts that need to
be manufactured and mounted for the oil pan from 14 on the metal design to
eight. The number of key work steps needed in the final assembly of the engine
has also been cut from eight to two. For example, the bulkhead panel is
integrated into the lower part of the pan and no longer has to be installed
separately with a seal. Furthermore, the oil return lines of the turbocharger,
the oil separator and the air-oil separator are combined in the pipeline
carrier.
More than two kilograms of weight saved
Polyamide 6 has helped to
reduce the weight of the upper and lower sections of the oil pan to 1.3 and 1.8
kilograms respectively. Overall, the oil pan is more than two kgs lighter than
its aluminum predecessor, due to the lower density of the plastic and the
optimised wall thicknesses.
Injection moulding process
with benefits
A key argument in favour of
manufacturing the oil pan using injection moulding was the huge potential that
the process offers for integrating functions and thereby cutting costs. What’s
more, as the parts are produced in a single step in the mould, there is no need
for complex finishing work such as deburring die-cast aluminum parts. The lower
energy costs are another benefit in favour of manufacturing injection-moulded
parts.