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'.

Of travelling-column floor-type design, the Union P/PC range of horizontal live spindle boring and milling machining centres are believed to be the most flexible machines for large workpieces.
Of travelling-column floor-type design, the Union P/PC range of horizontal live spindle boring and milling machining centres from exclusive UK agent, Ward CNC of Sheffield, are believed to be the most flexible and universally applicable machines for processing large workpieces accurately and consistently. This is courtesy of features such as auto head and tool changers (up to 80 tools) and the optional NC facing head, pick-up system and NC rotary table - coupled with Union's established build principles of cast iron construction for rigidity and up-to-date linear guideway technology that promotes both high specification and performance. Between them, the P/PC 130 and 150 variants have X axes travels from 4000mm up to 10m and larger, Y axes from 2000mm up to 3500 mm and Z axes of 800mm.

W axis (boring spindle) is 750mm and the 50/60kW motor produces maximum speeds of up to 3,000 revs/min.

The machines are constructed with heavily-ribbed beds featuring backlash-free compact roller guides of the table saddle and column infeed motion for precise, stick-slip free motion.

The column assembly is of rigid box-type cast iron construction, again with precisely machined faces for the preloaded, compact roller guides.

Of solid cast iron construction, the headstock accommodates a high-precision main spindle system by means of preloaded spindle bearings with lifetime lubrication.

Boasting hardened and ground gears for automatic speed range changes, the gearbox is thermally stabilised.

Backed by Union's over 140 years' of manufacturing know-how in Chemnitz, Germany, the P/PC machines are being offered alongside Union's latest generation table- and cross bed-type CNC horizontal live spindle boring and milling machining centres by Ward CNC, a company with vast experience of the brand in the UK.