The manufacture of braking systems for rail vehicles is the specialism of Knorr-Bremse Rail Systems UK.

Its patented EP2002 distributed brake control systems are recognised as the best in the world and are the ‘de-facto standard’ on all new trains for London Underground, as well as metros in Bangkok, Dubai, Manila and throughout China.

Designed in the company’s engineering and manufacturing facility in Melksham, Wiltshire, to a very high specification (which includes 25µm dimensional tolerances and a ‘mirror finish’ of 0.2 CLA in the valve bores), the systems comprise eight main prismatic parts.

These are machined in a Knorr-Bremse production facility in nearby Corsham from solid aluminium billets on Heller twin-pallet horizontal-spindle machining centres (HMCs), although the latest — installed in July 2017 — is fitted with a four-pallet pallet pool (www.heller.biz).

Paul Ranford, improvements manager at Corsham, said: “Our EP2002 brake control systems were introduced in 2004. Production grew steadily until the end of 2015, not least because it became the standard for railway-vehicle bogies in China.

"Our units have been installed on metro systems in over 30 cities in China, including Shenyang in the north-east, Beijing and Shenzhen near Hong Kong.

“In 2016, demand increased further, and 2017 will be another record year, with 15,000 units manufactured.

“The system’s success is down to the way braking effort is applied across the entire train, to optimise braking performance and allow for different weights of the individual carriages and different track conditions.

“However, the level of precision that goes into manufacturing the valves is also a strong selling point, as it translates into long service life, efficient braking and energy savings. For this reason, we need very-high-quality production equipment.”

Production strategies

Due to the higher manufacturing throughput, the company had to rethink its production strategies. It had already foreseen an upturn and installed a second stand-alone Heller HMC — an H2000 — in 2015, to work alongside a flexible manufacturing system (FMS) comprising three Heller machines.

The purchase of a sixth H2000 was brought forward, and the decision was taken to have it equipped with a four-pallet pallet pool to take maximum advantage of minimally attended production overnight.

Along with this investment, a lot of effort was put into program optimisation between July and September this year, to increase output further.

This resulted in an average reduction of 20% in machining cycle times, and it was achieved by: speeding up traverse rates to minimise idle times within cycles; increasing feeds and speeds during cutting by using new grades of carbide-insert tooling; and introducing special cutters.

The latter include form tools and diamond-coated reamers, principally from Mapal.

Furthermore, flexibility has been maximised by having the potential for each Heller HMC to be equipped to make all eight types of prismatic valve component that go into the Smart, Rio and Gateway variants of the EP2002.

The pallet-pool cell, for example, is tooled up to make six component types.

Mr Ranford said: “Knorr-Bremse Rail Systems UK inherited four of the Hellers, including those in the FMS, when we took over the sub-contractor in Corsham that was previously manufacturing the parts for us on this site.

“When we purchased our additional stand-alone machine in 2015, we considered a couple of other potential suppliers of HMCs used in Knorr-Bremse Group’s Budapest manufacturing facility.

“However, we saw no reason to change, as Heller’s UK headquarters is only two hours away from us in Redditch.

"They also have a manufacturing operation there, so the technical expertise and service capability available in this country are more in-depth than would otherwise be the case.”

Mr Ranford said both the stand-alone machine and the recent pallet-pool cell, which were passed off at Redditch and again after installation in Corsham, were running 24/7 within three weeks of delivery, adding that the Heller team has a true understanding of Knorr-Bremse Rail Systems UK’s manufacturing operation.

Moreover, he says the working relationship with the supplier and the service back-up are first-rate, which translates into minimum spindle down-time at the factory and the all-important high levels of manufacturing output that are needed.