When Joy Global wanted to boost productivity at its UK manufacturing facility, the company turned to Yamazaki Mazak. Solutions reports.

In the mining sector, Joy Global is well-established name. From roof supports through to conveyor systems and cutters for coal extraction, the company’s products are used both for underground and surface operations in mines across the world. Its Worcester-based manufacturing facility concentrates on two products, namely powered roof supports along with gear case and sprocket ring manufacture.

Whilst the UK mining industry is a shadow of its former self, the rest of the world continues to dig for its coal supplies. More than 80% of Joy Global’s equipment, which is manufactured in the UK, is ultimately exported to many countries across the world including China, the United States and Australia.

“Every element of the factory is busy at the moment,” says Rob Wilks, production engineering manager at the Worcester facility. “In some areas we are working double shifts in order to cope with demand with parts are going both to stock and direct to customers straight from the factory floor. A sprocket ring, for example, is treated as a consumable, therefore it is important that we maintain stocks in order to achieve a quick response to our customers’ demands.”

“We subcontract a large number of productive hours in the UK, but there is a limit to the number of subcontractors that can take on both the size and complexity of parts that we need to produce.”

Operational excellence

Productivity is therefore a key issue and goes a long way to explaining why Joy Global turned to Mazak. In 2008 the company relocated the inner cylinder production line, which produces parts for powered roof supports, to a new bay. This impressive development fully adheres to the principles set out by Joy Global’s ‘Operational Excellence’ initiative, resulting in a state of the art production line. The first machine purchased, as part of this project was a Slant Turn which replaced two older lathes.

“The two old lathes frequently suffered maintenance issues due to their age,” Mr Wilks explains. “In fact, they were in maintenance more often than in production by the end of their useful life.

“The Slant Turn allows us to take heavy cuts on raw forgings. Crucially, the quality of finish at the rough stage is visibly better and the concentricity on first operation is so good that we don’t have to recut steady bands which, along with the very high feed rates, have cut cycle times down. What’s more, the Slant Turn 50N is much more reliable and robust than the previous lathes.”

Joy Global’s own figures demonstrate a production saving of 20% in cycle time. The company also gained further benefits by the elimination of work in progress queue time.

Machine consolidation

Part of Joy Global’s strategy is to merge multiple operations onto one machine wherever practical to do so – a philosophy that led to the acquisition of a Mazak Cybertech Turn 4500M with driven tooling.

“On inner cylinder production, we previously used two Boehringer lathes, a drum turret and a square turret,” Mr Wilks adds. “One machine would produce the piston head and the other would turn the main diameter. After that it would go onto a horizontal milling machine to mill a slot on the end face and drill two holes. With the 4500M we have effectively combined three operations onto one machining centre.”

Component size was also a key issue in the choice of the Cybertech. “We wanted to future-proof the production line with a 4m machine as cylinders on mining roof supports are getting longer and diameters are increasing as well,” says Mr Wilks. “We took a decision to buy a bigger machine than we needed at the time to ensure we could increase the size of cylinders if required in future.”

Once again, Joy Global’s figures demonstrate a significant saving. “Overall we’ve reduced cycle time from 217 minutes down to 124 minutes which is a 43% saving and eliminated three work in progress queues,” he reveals.

Building confidence

Following the success of the Cybertech, Joy Global purchased a second Cybertech Turn 4500MT, a twin turret version of the same machine. “Every successful acquisition builds confidence in a machine supplier,” says Mr Wilks. “This lathe was purchased to improve productivity in the gear shop. Used mainly on small batch work, the machine produces a wide range of complex parts.”

In 2011 Joy Global implemented another major investment with the relocation of the outer cylinder production line to a new bay. Like before, this fully incorporated all of the sound principles set out by Joy Global’s Operational Excellence initiative. The resulting streamlined production line incorporated the acquisition of an Integrex e-650H II which, again, has merged two separate machining operations.

“Previously we used two machines, a Soraluce bed type machine to complete the valve face machining and a Heyligenstaedt lathe to produce the counterboring operation,” Mr Wilks affirms.

In the future, Joy Global will continue to look at further process improvements across the Worcester site. “We are looking at a number of areas at the moment, but when it comes to justifying capital spend we have to be mindful that a business case has to be made. I’m pleased to say that with the recent investments made so far, Mazak have proved their ability to help us drive process improvements in our business with very competitive payback periods.”

Yamazaki Mazak
www.mazak.eu