Plastic Bearings Case Study:
Ultra-low Profile Plastic Bearings Resolve Friction Problems
The design flexibility of thermoplastics together with the intelligent use of
injection moulding technology solve a last-minute hitch in the development of
a state-of-the-art mobile satellite TV antenna system.
When the launch of a groundbreaking, ultra-low profile, mobile satellite TV antenna came under threat because of the failure during trails of a bushing solution due to high friction problems, BNL was called in to help.
BNL’s design and technical teams soon got the project back on track with two new custom designed injection moulded parts – a bearing and giant thrust race that form the mobile base of the antenna.
Using revolutionary phased array technology, the new antenna provides in-motion access to more than 300 live satellite TV and music channels via virtually all in-vehicle passenger entertainment systems in sport utility vehicles, mini vans and cars.
With the overall height of the antenna fixed at just 11.5cm, BNL’s designers had to come up with an ultra-thin bearing in ultra-quick time. But, having worked closely with the customer before, the team understood the application and the potential problems. The project had been alive for two years, but in just two weeks, the bearing design had been approved and the first prototype produced two weeks later.
The bearing is very thin – just 9mm high – with the pitch circle of the raceway designed as large as possible to offer maximum support. Integrated features include belt drive teeth around the outer edge, brass inserts to fix it to the unit and moulded pads on one side to provide extra stability. Being plastic, the BNL product is a much lighter weight solution. It is also more cost effective - an equivalent bearing in stainless steel would be many times more expensive.
As well as a bearing solution, KVH needed to find a way of supporting the perimeter of the 77.5cm wide antenna and asked BNL’s design team for ideas. The result is a giant thrust race with an outside diameter of 63.5cm. Manufacturing a plastic part of this size causes problems with tooling in terms of the expense due to wasted space in the tool. BNL overcame this by sectionalising the part in order to make it both cost effective and easy to manufacture with each part being moulded in one shot. The finished part is made up of eight identical sections which fit together effortlessly by way of an integral connection clip design.
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