Matt Neal, marketing director at the West Bromwich-based specialist wheel manufacturer Rimstock, says: “The automotive supply chain is characterised by innovation, quality, speed and reliability of delivery — and cost-competitiveness.
“As a progressive manufacturer in this sector — and with a growing number of high-profile OEM customers that includes Jaguar Land Rover, Lotus, Honda, Toyota and Nissan — we constantly monitor our performance to ensure continuous improvement; we also regularly upgrade our plant and equipment, our manufacturing processes and our systems.”
In 2010, the company made a strategic decision to expand and diversify its operations into a number of niche markets — including the defence and security markets, where it has been particularly successful over the last two years with its Bead Lock and High Load alloy wheels. In the motor-sport sector, the company has built on its Team Dynamics brand to supply high-performance cast and forged wheels to many national and international racing teams and racing-car constructors (in 2010, the company secured a three-year contract to supply forged wheels for the Australian V8 Supercar Championship).
As a part of its diversification, Rimstock also increased its capacity for producing forged aluminium wheels. Mr Neal says: “Car designers and manufacturers are constantly looking to minimise wheel weight — and therefore a vehicle’s unsprung weight — while maintaining strength and durability. Reducing weight has a dramatic impact on car dynamics and performance. With forged aluminium wheels — rather than cast ones — weight savings approaching 30% can be achieved; the wheels are also stronger and stiffer. These characteristics combine to give improved acceleration, handling and braking.”
Reviewing capabilities
In order to expand its forged-alloy wheel production, Rimstock undertook a thorough appraisal of its manufacturing capabilities, which resulted in the purchase of its first Doosan vertical turning lathe — supplied by Mills CNC Ltd
(www.millscnc.co.uk). Mr Neal says: “We could have attempted to ramp up production using horizontal lathes, but we could see that vertical lathes, which are assisted by gravity when loading components, were better suited to the machining of large, awkward-shaped parts made from tough materials like forged aluminium alloys.
"We were also convinced that vertical turning would deliver long-term savings through reductions in set-up times and cycle times, as well as increased tool life. We also anticipated improvements in accuracy and repeatability, and this has proved to be the case. We approached a number of machine tool manufacturers with our ideas and plans. Following extensive machining trials, we selected Mills CNC and the Doosan VT 750.”
This machine, equipped with a high-torque 30kW 2,000rev/min spindle and a 15in chuck, was installed in early 2011. Rimstock subsequently designed and built a ‘modular’ fixturing system that accommodates its different wheel diameters and wheel designs; this bespoke work-holding allowed the company to reduce cycle times and increase productivity. Parts are finished on the VT 750 in just one set-up and two machining operations, using a external profiling tools and boring bars; previously, the parts required two set-ups.
The productivity achieved by the VT 750 led to Rimstock buying two more vertical turning lathes and three Doosan DNM 650 vertical machining centres. The latter feature 15kW 12,000rev/min spindles and have been retro-fitted with rotary-axis tables for a full five-axis machining capability.
They are used for roughing and finishing forged- and cast-alloy wheels; cycle times, especially where the engraving of fine details is required, can be as long as 10hr. Since 2010, when Rimstock diversified its operations, its export business has grown; it now produces around 5,000 cast-alloy and 500 forged-alloy wheels a week.