Holroyd, has used one of its own unique milling centres to complete work on a pair of giant helical rotors destined for an environmentally friendly application in the USA.
Helical component and machine tool specialist, Holroyd, has used one of its own unique milling centres to complete work on a pair of giant helical rotors destined for an environmentally friendly application in the USA. With a finished diameter of almost 650mm, the first of three pairs of giant rotors were machined from billets weighing over 3 tonnes each, making them some of the largest rotors ever produced. The order presented an ideal opportunity for the Rochdale-based company to apply the expertise that makes it one of the world's leading manufactures of helical components and the machine tools on which they are produced.

The pair of stainless steel rotors were machined on a Holroyd 8A milling centre, one of only several centres in the world capable of handling components of this size.

The rotors will be used to compress waste gases created as a by-product of styrene production, enabling compliance with US legislation designed to help safeguard the environment.

An overseas consultant has made regular visits to Holroyd's plant in order to monitor production of the rotors, whose rough milling was performed with standard slitting cutters before the rotors were precision finished to a tolerance of 0.1 - 0.135mm around a 9 point profile.

The enormous size of each rotor made meticulous manual inspection the only practical way to check the component's precision finish, and required the rotors to remain in Holroyd's checking centre for a total of 3 days each.

Applications Engineer, Simon Rhodes, explained some of the special challenges presented by a project of this nature.

'The rotors were too big for conventional transportation around the plant and could only be moved using the overhead crane.

Three specially made, dedicated cutters were used to define the profile of each rotor and a phosphorous bronze outboard bearing support was produced specifically to hold the rotor's journal without causing wear to the component itself.

Production of each rotor lasted 17 days, with a week of 24 hour per day roughing and the remainder spent semi-finishing and finish milling until the required standard was achieved'.

Machine Tools Sales Director, Paul Hannah, explained, 'Holroyd has earned a world-wide reputation for the production of both high quality helical rotors and the machine tools used to make them.

The successful completion of these unusually large precision rotors, using one of our own machines, reflects the company's ability to fulfil the most demanding orders while illustrating the unrivalled performance offered by Holroyd's milling centres'.