Formed in 1917, Slack & Parr has progressed to become a market leader in high-precision engineering, with much of the output from its facility in Kegworth, Derbyshire, being pumps that are used for polymer extrusion and metering — generally in the global man-made fibre industry.
The facility houses a cell comprising 11 Hauser S-series jig grinders that are dedicated to the manufacture of key components for a wide range of high-precision gear-type metering pumps and hydraulic flow dividers.
Pumps manufactured by Slack & Parr have been responsible for several major innovations in man-made fibre spinning, and the company acknowledges that its expertise in jig grinding critical components to micron tolerances has been key to its global success. Moreover, continued investment in the jig grinding cell has been essential in the company remaining competitive in the major Asian export markets.
The first Hauser jig grinder — an X3 microprocessor-controlled machine — was installed in Kegworth in 1988. It has since been followed by a further 10 machines, and all 11 are currently in full-time operation. The most recent machine — a Hauser S35 four-axis CNC model installed in 2012 — joined three similar units.
The grinding shop at Slack & Parr manufactures precision pump components such as gear casings and gears with tolerances as tight as 2µm, and most components are manufactured from hardened tool steels up to 63 HRC. The gear pumps need to work continuously at temperatures up to 500°C with only the pumped product for lubrication; moreover, they must achieve a discharge accuracy of <1% pulse-less flow — and withstand differential pressures as high as 400 bar.
Rigorous inspection
During grinding — and upon completion — the parts are rigorously inspected using customised air gauging equipment. A typical gear casing could feature up to 11 precision-ground bores with different diameters (these accommodate the gears, dowels and the main driving spindle); and because many customers require bespoke designs, Slack & Parr estimates that it manufactures as many as 2,500 different pump models.
The specification of the Hauser machines (Hauser is a Kellenberger company within the Hardinge Grinding Group —
www.jonesshipman.com) includes options such as ISI/DIN programming using the Hauser Software Cycles; these ensure that the control covers all aspects of the jig-grinding process with a wide range of grinding techniques (including bore, contour, pocket and shoulder) — with MSS (multi-sensor system) for the automatic suppression of ‘air grinding’ and for automatic grinding-wheel calibration.
The S35-400 features an automatic tool-change arbour, a 9,000-70,000rev/min spindle motor, measuring probe and the Hi-Cut system, which allows the use of grinding oil as the lubricant.
In total, Slack & Parr’s grinding shop employs some 30 people (on a shift basis). Three of them — Suresh Patel, Ashley Beadling and John Meggison — have between them over 70 years’ experience of working on Hauser machines in Kegworth. Indeed, Mr Patel was the first Slack & Parr operator trained on the company’s Hauser X3 microprocessor-controlled machine when it was installed in 1988.
Mike Duignan, managing director of Leicester-based Jones & Shipman Hardinge Ltd says the operation at Kegworth is a Hauser flagship installation. “We know from our extensive dealings with Slack & Parr that the machines are absolutely integral to the precision and longevity of the company’s world-renowned products.
"Machine number 11 is running quite comfortably alongside its 25-year-old predecessor, and these experienced operators are handing on their skills to the younger team members and apprentices in the organisation.”