Dorking-based Johnston Sweepers — a manufacturer of road sweepers for over 75 years — is reaping the benefits of switching from metal fabricated components to plastic parts with the assistance of local injection moulder Broanmain Plastics (www.broanmainplastics.co.uk).

The company had thought for some time about switching from metal, predominantly steel, to lightweight plastic for some components, but low production volumes combined with the initial capital outlay for mould tooling made the investment hard to justify.

Additionally, with vehicles exported world-wide, all components needed to be able to withstand extreme heat and cold — and perform in wet, dry, dusty or sandy environments. However, a meeting with Broanmain changed these perceptions.

Johnston Sweepers’ head of purchasing, Steve Hurst, said: “The Broanmain team presented us with a range of durable materials and sensible tooling prices that enabled us to realistically consider changing to plastic moulding.

“By sourcing the tooling from a high-quality Chinese-based specialist, we were able to justify the switch.”

Starting with the filler cap, Broanmain collaborated with Johnston Sweepers’ in-house design and purchasing teams to develop an initial prototype and trial the strength and durability of plastic materials.

Further production trials and tests confirmed the project’s viability, with Broanmain overseeing all aspects of tool development, and Mr Hurst now estimates that switching from aluminium to plastic for filler caps has halved the part cost.

Since then, Broanmain has helped convert more than 30 metal parts to plastic, among them a complex suction water outlet integral to the road-sweeping operation that previously cost £50 and required extensive welding and powder coating.