Product category:
Miscellaneous machine tools, gear cutting machines and equipment
News Release from: Holroyd | Subject: Helical profile machining centre
Edited by the Manufacturingtalk Editorial
Team on 09 June 2004
Special millers produce largest screw
rotors yet
Specialist machine tool and helical component manufacturer is to produce three sets of the largest screw rotors ever made for a German compressor manufacturer.
MAN Turbomaschinen AG, the compressor division of MAN, one of Europe's largest machine manufacturers, has turned to UK specialist machine tool and helical component manufacturer Holroyd to produce three sets of the largest screw rotors ever made Each rotor, measuring 816mm in diameter by 4 meters in length will weigh over 4 tonnes when finished
This article was originally published on Manufacturingtalk on 14 Aug 2001 at 8.00am (UK)
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The rotors are to be produced on a modified Holroyd 8A milling machine.
The standard 8A is the largest helical profile-machining centre available on the market and produces components up to 800mm in diameter.
This is where one of Holroyd's particular engineering advantages lies; as both the manufacturer of the machine tool and also a sub-contract supplier of the components produced on it, the company is able to direct the development of the machine to match market requirements and ensure optimum results.
An 8A machine based at Holroyd's own production facility in Rochdale has since been comprehensively re-engineered in order to accommodate the MAN Turbo order.
It is now the only one of its kind and the only machine capable of accurately cutting deep helical profiles with a diameter of over 800mm.
Due to the amount of material that has to be removed, it will take approximately two weeks for the machine to rough-cut each rotor form from solid forged stainless steel blanks.
The rotors will then be heat treated to relieve metal stress and finish milled at Holroyd.
Unlike smaller screw rotors that are produced in higher numbers in a semi-automated process, each large set has to be manufactured as a matched pair.
The finished dimensional tolerances of the corresponding male and female forms are maintained to just a few microns throughout the complete intermeshing profile surfaces.
The bespoke tooling and checking procedures required to achieve this are all designed and produced in-house to ensure total control and consistency throughout the manufacturing process.
The female rotor requires less tooling and so is produced first.
The male rotor is initially milled 100 microns oversize and then the set are meshed together in a test cell where the profile clearances are measured and mapped.
The male rotor is then progressively machined down close to finished size providing the opportunity to modify or 'fine tune' the form where necessary.
Once this process is completed a finish cut is made to remove the last 25 microns and results in two intermeshing profiles with an overall tolerance in single microns.
One of the unique skills Holroyd are able to employ here is the ability to blend the surface curves of the rotors using the first stage machine tooling.
Other manufacturers use additional finishing runs with separate tooling and in some instances polish the finished surfaces.
According to Holroyd this practice is both inefficient and detrimental to the level of form accuracy the company is able to achieve.
Holroyd Sales Director for Machine Tools, Paul Hanna, comments on the order, "We are proud to have won this contract based on our abilities as a provider of truly world-class engineering solutions.
Doubly so, since we have retained our skills and invested in new product development to remain at the forefront of precision thread grinding machine tool technology." A point underlined by the company's international client base and sales figures that show over 70% export business.
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