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GraniTek is the UK’s leading manufacturer of precision granite (polymer concrete) castings and was formed following a management buyout from Taylor Hobson in 1997, with the metrology specialist remaining a key customer.

Since the MBO Managing Director, Derek Robinson has developed the business and its market, expanding sales to a diverse range of customers and with a capacity to regularly create castings from 10 kg up to 10 tonnes it is producing everything from scientific instruments, machine tools, precision lenses and semi-conductors.

 

The use of granite as a machine base offers many advantages such as higher vibration damping, better long-term thermal stability, improved noise absorption, as well as excellent static and dynamic stiffness. GraniTek has developed its products over many years and created its own ‘recipe’ to produce what it sees as the optimum product. This recipe involves a mix of nine different grades of granite, ranging from 20 mm section down to micron dust level. This is mixed with an epoxy resin and moulded to shape. An exothermic reaction then occurs raising the temperature to around 65°C and the casting is left to harden overnight.  Once that casting process is complete GraniTek then has to grind the granite to produce a smooth and accurate surface, an area that has seen recent significant investment.

“Our grinding capacity was restricted to 1.2 m by 0.5 m on an old CNC machine that we have, this meant anything larger being put out to sub-contract. The added problem here was, given our material many sub-contract grinding companies were reluctant to take on our work. This and the relatively low-volumes meant we were often at the back of the queue, impacting on our lead times,” says Derek Robinson. Finding the right machine to upgrade GraniTek’s grinding capability was a challenge in itself, due in part to the company’s location, with the factory built on reclaimed land that was part of an old brickmaking area.

“Our choice of machine was limited by the civil engineering work that we would have to do. During my research every machine we looked at would require deep foundations and piling to overcome our poor location. This meant our search for a suitable machine was a drawn out process as the cost would be prohibitive. We then came across the Perfect range from RK International and due to the weight of the Perfect PFG-160200AHD Double Column machine, at 23 tonnes, we could install it without any significant civil engineering.”

In addition to its weight the Perfect PFG-160200AHD Double Column machine also extended GraniTek’s grinding capacity significantly with its 1600 by 2000 mm table size and 6000 kg table weight load. The machine uses a slant beam construction to provide excellent load distribution and ensure maximum stability during heavy-duty grinding. This is assisted by use of heavy-duty linear guideways; precision feed on vertical-axis; and hydraulically-controlled variable feed table speed. GraniTek also specified the optional dynamic wheel balancing system that constantly monitors the grinding wheel and makes adjustments to its balance in real time. This helps to improve and maintain surface quality. Given the nature of the end products produced by GraniTek flatness of the ground surface is also important. Here Derek Robinson called in a favour with some ex-Taylor Hobson colleagues (Spectrum Metrology) who measured the magnetic table using a TalyVel system to achieve less than 20 micron flatness across its 1.6 m by 2 m table area.

“This was a major investment for us running to around £200,000.00 with everything taken into account,” says Derek Robinson. “However, we knew it was an investment we had to make and the results are proving it. We now have greater control over our production and lead times, that were as long as 20 days when relying on sub-contract are now down to four days. In addition to saving on the work we put out to subcontract, we are also winning work from other businesses looking for large capacity surface grinding, which is further helping the justification of the initial machine purchase.”

The Perfect PFG-160200AHD sits in the middle of the double column range from Perfect with the smallest machine having a table size of 1200 mm by 2000 mm and the largest having a 1600 mm by 6000 mm capacity. “We are seeing growing demand for the Perfect range, which  is totally focussed on surface grinding from the smallest saddle-type machine trough the large double-column machines and the recently introduced PFG-series of PLC controlled grinders,” says Dick Aldrich, Director,  RK International Machine Tools. “The entire range offers excellent value for money with outstanding specifications, including the use of Perfect’s user-friendly PLC control system that enables users to be quickly in production after just a couple of hours of training, in most cases. All of these facts were recognised by Derek at GraniTek and we are pleased to see that he is now reaping the rewards of the confidence he placed in Perfect and RK International Machine Tools.”

For further details visit:
RK International Machine Tools Limited                
www.rk-int.com

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