Moulded antenna cuts weight and costs

A Sabic Innovative Plastics product story

Edited by the Engineeringtalk editorial team Nov 27, 2006

ERA Technology selected next-generation Ultem 2312EPR resin instead of machined aluminium to cost-effectively mould a complex antenna for consumer vehicles while reducing part weight by 30%.

ERA Technology is a UK-based leader in antenna technology for military, commercial, and high-volume applications.

When developing a revolutionary new low-profile antenna for mobile connectivity to the Internet and satellite TV, the company lost little time in deciding against traditional machined aluminium in favour of a thermoplastic resin.

To achieve its goals of light weight, reduced cost and high-volume production, ERA worked with GE Advanced Materials to identify the best resin and create the most effective part design.

Applying its experience in military communications to the consumer market, ERA developed a compact antenna concept for tracking satellite signals from a moving vehicle.

The antenna had to have a very low profile, making it suitable for mounting on top of recreational vehicles, motor homes, boats, aircraft, and railroad cars where height is an issue.

ERA wanted to be able to produce the antenna in large volumes and make it affordable.

Design elegance for appeal to consumers such as yacht owners was also a key objective.

ERA briefly considered aluminium for the antenna, but recognised that the time required to accurately machine such a large (approximately 686 x 584mm) and complex part would be cost-prohibitive.

aluminium's weight was also a drawback.

Instead, ERA decided to pursue injection-moulded plastic and approached GE Advanced Materials for advice.

ERA had a number of requirements, including the ability to plate the part with copper for optimal radio frequency reception; a coefficient of thermal expansion (CTE) similar to that of aluminium, and low warpage with high modulus to ensure tight tolerances.

GE Design Engineering recommended next-generation Ultem 2312EPR resin for its exceptional balance of properties, particularly enhanced flow length that enables injection moulding of large parts.

Ultem 2312EPR resin provides excellent bonding strength with copper, as well as dimensional stability when used in a multi-layer part.

This latter characteristic was critical for ensuring accurate satellite signal reception over a broad temperature range.

The GE team also worked with ERA to analyse the part design.

Mould flow software was used to identify the best gating locations to achieve a balanced fill pattern that would minimise warpage.

The resulting product - ERA's G1 low profile antenna - has a highly efficient and attractive design that provides maximum reception within a relatively small enclosure compared with conventional technologies.

This antenna is 30% lighter than one made of machined aluminium.

Thanks to the efficiencies of injection moulding compared with machining, the part can be produced at a substantially lower cost.

"If we had been limited to aluminium for the antenna, it's unlikely that the revolutionary antenna technology would have been financially viable", said Dr Robert Pearson, Head of Antenna Systems, ERA.

"Moving to a solution using plated Ultem thermoplastic resin has allowed us to develop a highly complex product for mass markets at a competitive price".

GE's Ultem resin is an amorphous thermoplastic polyetherimide offering outstanding high heat resistance, high strength, modulus, and broad chemical resistance.

Its balance of properties and processability offer design engineers exceptional flexibility and freedom to innovate.

For the telecommunications market, Ultem resin offers high heat resistance, platability, as well as great flow for thin wall design.

Ultem resin can replace aluminium and thermosets.