Product category:
Automation and assembly equipment
News Release from: Gudel UK | Subject: High precision gantry positioning system
Edited by the Manufacturingtalk Editorial
Team on 06 October 2000
Clever parts transfer on 68m
manufacturing cell
Holroyd set about designing what is believed to be the world's largest automated manufacturing cell for its close tolerance rotors for screw compressors, and turned to Gudel UK for support
Precision and innovation are two words that recur throughout the history of Lancashire-based engineering company, Holroyd By the end of the 19th Century, the business had established an enviable reputation at the forefront of industrial gears and machinery production and had already invented the principles of thread milling that are still used today by manufacturing industry world-wide
This article was originally published on Manufacturingtalk on 19 Feb 2001 at 8.00am (UK)
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Later, it pioneered the development of worm gear technology and the production of close tolerance rotors for screw compressors.
This is a field where Holroyd regularly works to microns.
So, when the company set about designing what is believed to be the world's largest automated manufacturing cell for these components, it is no surprise that it should look for similar qualities in a partner to produce a component handling system capable of maintaining the ultra close positional accuracies required.
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Still occupying the site in Rochdale it moved to in 1897, Holroyd is today part of the world-wide Reynold engineering group.
The 280-strong company has come a long way since producing its first textile machine in the mid 1800s.
It is a recognised leader in helical thread form technology, being the world's largest producer of helical screws from 6 mm to 800 mm diameter.
It is also the UK's largest producer of worm gears and a further substantial part of the company's business is devoted to the development and production of helical milling and grinding machines, chiefly for the manufacture of screw compressor rotors.
Two Queen's Awards for Technical Achievement reflect the company's position at the leading edge of technology.
The company also won first prize for 'measurement and manufacturing excellence' in the recent Metrology for World Class Manufacturing Awards and has achieved 'Millennium Product' status for its advanced rotor production centres.
The latest generation of Holroyd thread milling and grinding equipment takes worm gear and helical screw manufacture to new levels of accuracy and productivity.
So when the company came to create a state-of-the-art automated manufacturing cell for compressor rotors, these machines would clearly be at its heart.
However, a major element governing the success of the venture would be the ability to control the handling of process parts to the same level of precision and reliability as the machine tools themselves.
At 68 metres in length, the new cell is believed to be the worlds' largest.
Its layout is split into two separate lines, allowing buffer stocks to be maintained within the cell to smooth out variations in machining cycles.
It also incorporates a number of novel features to enable six diameters of rotors to be produced around the clock to the highest quality standards.
"But it's not just about zero defects," says Holroyd's Sales Director for machine tools and rotors, Paul Hannah.
"The line has been justified on the basis of guaranteeing an overall cost per part.
Its operational sequence is based on principles we have established and refined over many years and, not surprisingly, draws heavily on the capabilities built into our own precision machine tools." After initial turning operations, the rotor billets are profile milled to within 0.4 mm of finished size.
They then progress for further turning and cylindrical grinding operations, before being transferred to a Holroyd TG 150E machine for finish grinding.
This is the most intricate and carefully controlled part of the manufacturing process, with each flute first being ground to within 40 microns of finished size, before an in-built CMM probe monitors the component ahead of the finishing pass.
A feed back loop to the control system - coupled with in-process form dressing of the grinding wheel - then ensures that each component is produced, and 100 per cent inspected, to the most rigorous quality standards.
Finally, the finished machined rotors are transferred to a Holroyd Conturo beburring unit prior to delivery to the unload position.
"Yet, the manufacturing capabilities of each of the machine tools represent just part of the total solution," continues Mr Hannah.
"From day one, it was clear that the ability to meet the necessary throughput targets for the cell would hinge on the development of a parts loading system to enable the full potential of the production equipment to be realised.
"Not only would the handling system need to exhibit high accuracy and repeatability, but it would have to be tailored to our specific requirements.
It meant that our selected supplier simply had to be able to underpin its product with excellent technical back-up and customer support.
"We simply could not afford any weak links on such a major project, so we went to considerable lengths to evaluate a number of potential partners, before deciding to forge a close working relationship with Coventry-based Gudel UK." The resultant solution is based on the proven capabilities of a Gudel high precision gantry positioning system and is capable of consistently delivering components weighing up to 110kg each to a few tenths of a millimetre at any of the machine tools in the cell.
With locational accuracy such a key issue, special attention was paid to the gripping mechanism, as well as the transfer of the process parts.
Typically, each of the machine tools locates the components at their end faces, which means that the parts handling mechanism has to operate on the body of each rotor.
"This is relatively straightforward while they are at the rough turned state," explains Gudel's joint managing director, Gary Ottley.
"But once the spiral form has been generated, this configuration causes severe problems for conventional gripping systems - especially as the system must be capable of accommodating a range of component diameters from 109 mm to 160 mm.
To overcome this, Gudel and Holroyd devised a solution in conjunction with Eclipse of Sheffield, which utilises a magnetic gripping principle.
A further requirement of the parts transfer system is that some of the intermediate grinding operations call for the workpiece to be rotated through 180 degrees to enable each end of the rotor to be processed.
This has been achieved by incorporating a high accuracy indexing mechanism from Manifold - another Reynold company - within the final installation.
The resultant Gudel system combines the benefits of high accuracy - to match the precision of each of the Holroyd machine tools within the cell - with rapid traversing to ensure maximum production throughput.
"Developing and producing a cell such as this represents a multi-million pound investment," continues Mr Hannah.
"We have found from past experience that a wide range of problems will always emerge, which simply cannot be predicted at the start of the project.
That's why we felt it was so important to find a partner that we could work closely with and have complete confidence in.
Over the past two years, Gudel has demonstrated that its quality products are backed by first class service and applications engineering support.
In short, they have proved to be exactly the partner we thought - and hoped - they would be.
I am sure we shall be working with them again on similar projects in the future.".
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