Full blown milling advances

Designated as the Holroyd 4EX-R-BL (BL = blower), this latest model from Holroyd Precision brings high levels of speed to the manufacture of rotors used in Roots-type blowers (also known as rotary lobe blowers). The machine is aimed at blower manufacturers wishing to achieve high levels of efficiency.

“For some time, we have been looking at how we can further extend the capabilities of our EX series milling machines to enable the high-speed, high-precision and high-performance manufacture of Roots-type blowers,” comments Holroyd sales manager, Mark Curran. “We believe our new model will revolutionise the way in which straight fluted, infinitive lead rotors are milled, significantly reducing manufacturing time and increasing the accuracy of the production process.”

Although sitting within Holroyd’s EX range of rotor milling machines, the 4EX-R-BL is in fact a totally new machine that has been designed from the ground up. As well as being equipped to mill helical rotors of up to 450mm in diameter, the 4EX-R-BL will rough mill blower blanks of around 320mm in diameter and 900mm body length into straight fluted rotors in 30 minutes floor-to-floor, ready for finish profile milling to absolute size. This represents a significant time saving when compared to the one-and-a-half to two hours typically required to cut individual Roots-type blower rotor flutes using traditional milling techniques.

“Until now, manufacturers producing rotors for Roots-type blowers have been forced to either rely on NC flatbed milling machines or machining centres that have been retrofitted to absorb the considerable vibrations that occur during the flute milling process,” continues Mr Curran. “Consider the fact that when using either one of these methods each flute has to be milled in a separate operation, and it’s not surprising that the machining process for Roots-type rotors has always been labour intensive and costly.

“By contrast, the technology offered by the 4EX-R-BL moves the manufacture of Roots-type rotors away from traditional flatbed milling, where the component would be manually turned after each flute was cut, to a fully automated, programmable process able to machine both two- and three-flute blowers in one sequence.”

Totally removing the need for manual intervention or indexing during the milling of each flute, the Holroyd 4EX-R-BL features a bespoke steadying system that has been designed to withstand the additional forces that are generated during the milling of straight flutes. Specially developed ‘finger clamps’ ensure the workpiece is held securely while a flute is being milled, then released to enable automatic rotation and positioning ready for milling of the next flute.

“In what has been a genuine ‘from the ground up’ development of a completely new kind of machining centre, in the 4EX-R-BL we have designed a model that is able to produce all helixes from horizontal to vertical, for helical rotors, infinitive lead blowers, helical blowers, compressor rotors and vacuum pumps. This significant level of versatility makes the 4EX-R-BL well suited to manufacturers who possibly make different rotor types and therefore need considerable flexibility in their machining technologies, as well as providing a new, highly effective manufacturing solution for producers of Roots-type blowers,” Mr Curran concludes.

The Precision Technologies Group (PTG) incorporates the brands of Holroyd, Holroyd Precision Rotors, Binns & Berry and Crawford Swift, PTG has established itself at the forefront of high precision machine tool design, build and supply.

The PTG range includes ultra-precision grinding machines for rotor, thread and gear operations; rotor milling machines; heavy-duty lathes; deep hole boring machines; friction stir welding machines and special purpose machine tools for the manufacture of precision components.

HOLROYD www.holroyd.com