GraniTek, a leading UK manufacturer of precision ‘granite’ (polymer concrete) castings, was formed in 1997, when Taylor Hobson decided to sell a non-core business (the metrology specialist remains 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 with its ability to produce castings weighing from 10kg up to 10 tonnes.

The use of granite as a machine base offers many advantages, including high levels of vibration damping, good long-term thermal stability and good noise absorption — plus excellent static and dynamic stiffness.

GraniTek has developed its products over many years and created its own ‘recipe’ to produce what it regards as the optimum product. This recipe involves a mix of nine different grades of granite, ranging from 20mm ‘sections’ down to ‘micron dust’.

These are mixed with an epoxy resin and moulded to shape, after which an exothermic reaction raises the temperature to around 65°C. The casting is then left to harden overnight, before being ground to produce a smooth and accurate surface.

Mr Robinson said: “Our in-house grinding capacity was restricted to 1.2 x 0.5m by our old CNC machine, so anything larger had to be sub-contracted out, but many sub-contract grinding companies were reluctant to take on the work, because of our material.

“Coupled with our relatively low volumes, this meant that we were often at the back of the queue, which impacted on our lead times.”

Finding the right machine to upgrade GraniTek’s grinding capability was a challenge in itself, due in part to the company’s factory being built on reclaimed land that was part of an old brick-making area.

“Our choice of machine was limited by the civil engineering work that we would have to do. During our research, every machine we looked at would require deep foundations and piling to overcome our poor location, making the cost prohibitive.

“We then came across the Perfect PFG-160200AHD double-column machine, which — at 23 tonnes — we could install without any significant civil engineering work.”

This machine — supplied by Erith-based RK International Machine Tools Ltd (www.rk-int.com) — also extended GraniTek’s grinding capacity significantly with its 1,600 x 2,000mm table and 6,000kg load capacity.

The machine uses a slant-beam construction to ensure excellent load distribution and maximum stability during heavy-duty grinding. Also contributing to the machine’s performance are heavy-duty linear guideways, a precision feed on the vertical axis, and hydraulically controlled variable-feed table speed.

GraniTek also specified the optional dynamic wheel balancing system, which constantly monitors the grinding wheel and makes adjustments to its balance in real time, thereby helping to improve surface quality.

Given the nature of the end products produced by GraniTek, the flatness of the ground surface is of utmost importance.

Mr Robinson ‘called in a favour’ with some ex-Taylor Hobson colleagues (Spectrum Metrology), who measured the grinding machine’s magnetic table using a TalyVel system. They confirmed that it was flat within 20µm over its total area.

“The Perfect PFG machine represented a major investment for us, running to around £200,000 with everything taken into account,” said Mr Robinson.

“However, we knew it was an investment we had to make. We now have greater control over our production and lead times, which were as long as 20 days when relying on sub-contractors but are now down to four days.

“In addition to savings made by no longer putting work out, we are now winning work from other businesses looking for large-capacity surface grinding. This is further helping to justify the machine purchase.”

GraniTek’s PFG machine sits in the middle of the double column range from Perfect, with the smallest machine having a table size of 1,200 x 2,000 mm and the largest one of 1,600 x 6,000mm.

Dick Aldrich, a director at RK International, said: “We are seeing growing demand for the Perfect range, which is totally focused on surface grinding, from the smallest saddle-type machine to the large double-column machines and the recently introduced PFG-series of grinders.

“The entire range offers excellent value for money with outstanding specifications, including the use of Perfect’s user-friendly PLC control system, which enables users to be quickly in production after just a couple of hours of training.”