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Soraluce SP 8000 Travelling Column at Joy Mining

Soraluce SP 8000 Travelling Column at Joy Mining

Added to MTDCNC by TW Ward CNC Machinery Ltd on 06 March 2012

With a current order book topping £110 million, Joy Mining faces ever growing pressures from global competition in exporting over 80 per cent of its £160 million turnover to the likes of China, USA, Poland, Australia and South Africa. This means that, apart from product development, the expertise of its production engineers plays a significant role in the utilisation of often complex machining cycles on the high-tech machines that produce workpieces in very small batches (rarely exceeding four-offs).

As Robert Wilks, Production Engineering Manager, outlines: &ldquoBecause much of our work is small batch and very diversified, the extensive skills of our setters and operators are key to not only running the machines but also for tooling up, programming and for taking complete responsibility for the manufacturing tasks.&rdquo

Indeed, this directive came into play when the company was looking to replace a hard-worked, ageing Butler Elgamill CNC universal bed mill used to machine castings and flame-cut large plates: apart from everything else, Joy Mining was adamant the replacement machine had to allow the company to gain maximum advantage from the strength of its skill base.

The ion and installation in September 2011 of the Soraluce SP 8000 travelling column (bed-type) universal milling/machining centre from T W Ward CNC Machinery Ltd (Ward CNC) in Sheffield is a prime example of the benefits that can be gained from such a strategy, because not only has the machine halved cycle times and reduced tool costs on the castings and plates but its ability to produce other components, such as large gearbox housings, has also been capitalised on.

As part of the specification, the machine&rsquos Heidenhain iTNC530 control with its well-proven operator conversational interface provides the two setter/operators that man the Soraluce around-the-clock with the ideal solution to prepare and program the next scheduled component while the machine works through the existing product cycle.

Says day shift operator, Ean Stamp: &ldquoAs cycle times vary between one hour to two days (four shifts), we have ample time to work together and incorporate our machining experience in planning the next task while overseeing the cycle that&rsquos being run. This may not be to achieve the fastest cycle time but rather to ensure the part fully conforms to requirements.&rdquo

Based on a 50-acre site in Worcester, the company produces components for armoured face conveyors, large gear cases, sprocket ring gears, framed components for powered roof assemblies and hydraulic rams, as well as performs assembly tasks on a range of large valves. This array of components, often produced from difficult materials, is destined for use by the mining sector around the world.

Joy Mining was originally established in the 1930s as the Mining Engineering company (MECO) which led to a series of takeovers including Dowty (1970), a management buyout (1980) and an acquisition in 1996 by US mining specialist, Joy Mining Machinery, now a division of Joy Global Inc. Joy Mining is a truly global force in the development, manufacture, distribution and has risen to have the world&rsquos largest service and support infrastructure for underground mining machinery used in the extraction of coal and other bedded materials.

The Worcester operation employs 250 people where almost £3.5 million was invested in 2011 (and £1 million in 2010) on project-based equipment. The projected spend in 2012 is expected to top £1.3 million.

The five-axis Soraluce SP 8000 has a 45 kW, high torque 1,045 Nm drive to its double-jointed automatic universal indexing head, which has one joint vertical to the spindle centre line giving a full 360 deg rotation and the other at 45 deg providing a total of 20,736 (144 x 144 on each joint) specific positions. As part of the justification, Ward CNC had to ensure the machine met the specific requirements of Joy Mining&rsquos management team against five other competitor machine suppliers.

In addition, other key elements in the ion, justification and purchase of the machine included its ability to operate in a self-contained cell-type environment as well as the pedigree of the builder and the supplier&rsquos proven service record.

While both Soraluce and Ward CNC qualified with an acceptable pedigree of manufacturer and supplier, the SP 8000&rsquos build quality was carefully scrutinised to achieve a 10- to 20-year production life span. Here, its inbuilt rigidity and robustness for heavy machining was qualified by the Worcester machine shop, which had already gained good experience with an existing Soraluce bed mill supplied and supported by Ward CNC.

That said, it was the machining trials carried out at Soraluce HQ in Spain that finally drew the signatures to the machine order. As part of the buying process, Soraluce had to satisfy the machining demands of samples of Hardox high strength and impact abrasion resistant steel plate (425 to 475 BHN), a material widely used in coal face conveyoring.

Since installation, the machine has demonstrated overall savings of some 50 per cent on milling and particularly drilling cycles plus provided a significant reduction in tool costs as a result of its inherent rigidity. Says Mr Wilks: &ldquoWe very rarely have to change s, which is helping our tool inventory and costs.&rdquo

Following installation, the Soraluce has recorded spindle uptime of over 80 per cent (75 per cent is the company target) and has even machined fabricated assemblies some 5 metres long by 3 metres wide and high, which overlap the side of the 8 metres by 1.35 metres table. Also, large drive sprocket transmission cases having 20 to 50 micron hole tolerances and between-centre hole geometries of 0.05 to 0.1 mm have been produced, which include the production of main bores in transmission castings.

Quite significant is the fact that the full power of the machine can be exploited in the BT50 &lsquoBIG PLUS&rsquo patented spindle system which provides a dual BT50 taper and flange face interface for the tooling back ends. The tool is also clamped in the spindle with a force of some 15,000 Nm. This has enabled Seco&rsquos latest Performax indexable drills to be used for the first time as a test bed for the tooling supplier in producing bracket holes between 10 mm and 70 mm diameter and bores up to 90 mm diameter from solid utilising the 20-bar through-the-tool coolant pressure.

The 32-tonne Soraluce has an X-axis travel of 6,500 mm driven by two Heidenhain servo motors and gearboxes through a double rack and pinion. The vertical Y-axis is 1,600 mm and the Z-cross-axis is 1,200 mm. The special ram assembly is 480 mm by 500 mm which also houses the Heidenhain water cooled direct drive spindle motor delivering between 20 and 4,000 revs/min.

Included in the specification are adaptive feed control, DXF download and dynamic collision monitoring, plus Renishaw non-contact laser probing. Heidenhain linear scales ensure accuracy is maintained in X, Y and Z axes within ±0.005 mm. A 30-tool magazine will accept tools up to 125 mm diameter by 400 mm long (tool diameter can be extended to 250 mm with adjacent packets being left empty). Maximum tool weight is 20 kgs.

Of particular interest to Joy Mining&rsquos engineers was the machine&rsquos universal head design, which is able to deliver a massive 10,420 Nm of torque and maintain an indexing accuracy through both Hirth coupling joints within ±1 sec.

As part of the ability to utilise the skill of the setter/operators, the Soraluce SP 8000 was called upon to support an overflow condition for producing four different split gear cases some 1,500 mm long by 750 mm wide by 400 mm high. Each of the cast iron housings that have to transmit 11,000 bhp, have three main bores of 700 mm diameter. As part of the cycle the split fine faces had to be milled, 12 bolt holes drilled to 33 mm diameter and 40 mm deep in one casting half and 400 mm deep in the other. Holes were drilled and tapped M24 and thread milled M36.

In the second operation, the castings were relocated on the joint face and certain features milled, holes drilled and spot-faced, 2 inch BSP gas threads tapped and a series of M24 holes drilled and tapped.

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