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FEATURE: Retrofit transforms legacy machine tools to keep worn parts in use

Crawford Cullen and Grant Payne, Advanced Forming Research Centre, University of Strathclyde

The AFRC's hybrid CNC - laser metal deposition machine is the first of its kind in Scotland (Credit for all photos: AFRC)
The AFRC's hybrid CNC - laser metal deposition machine is the first of its kind in Scotland (Credit for all photos: AFRC)

"I wish there was a tool for adding material" – something that has been said in frustration time and time again when an issue during machining has resulted in a part being scrapped.

In the manufacturing industry, an immediate reaction to a failed or worn part is to purchase a new one. With masses of regulations in place, why take the risk of remanufacturing a part that could result in failure? With a new part, you can safely say that the quality meets your needs and matches the desired tolerance and specifications.

However, if you consider the cost and the lengthy lead time that it takes to get that part, the cost of stalled production while you wait and the increased carbon footprint generated by waste metal, remanufacture becomes a lot more attractive.

Take a wind turbine. If there is a failure and you order a new component, it might take as long as 15 weeks to arrive. The break in generation could waste thousands of pounds, on top of costs for the component.

There are concerns within manufacturing over the material properties of a part that has been restored to use. Laser metal deposition (LMD), however, reduces worries with high-precision, near-net-shape processing using a unique combination of lasers and powders. New or extra features can also be added to modify performance – all within one retrofitted legacy machine tool.

Repair, rework, remanufacture

Hybrid Manufacturing Technologies, one of our tier two members at the Advanced Forming Research Centre (AFRC), University of Strathclyde, has integrated cutting-edge LMD technology by retrofitting a CNC machine, creating a bespoke platform – the first of its kind in Scotland, and one of very few across the world.

The hybrid LMD machine can repair, rework and remanufacture. The technology can also build added features, corrosion-resistant coatings and high-performance coatings for high value components. This combination of additive technology with subtractive machining allows manufacturers to complete a whole remanufacture within one machine, minimising set-up time and increasing accuracy.

The hybrid machine

The hybrid machine

Rather than purchase a new part, manufacturers can take a worn part, scan it to isolate the locations of wear, fix the worn area and then build it back up to conform with the original geometry. They can then go on to add features that provide better performance.

During the LMD process, metal powder is blown into the path of a high-powered laser. It is then melted onto a component or substrate in single beads, then built up in layers until the final desired geometry is achieved.

Engineers can then use non-destructive testing, using a range of probes with frequencies up to 5MHz, to examine any surface or subsurface cracks and voids several layers deep.

Adding tools to the toolkit

The hybrid technology can be retrofitted for a relatively low cost to most existing CNC machines, which many manufacturers already have on their factory floor. The machine retains all the functionality that it had, with new capabilities that can be used independently or in conjunction with its original purpose. If you have all the tools you need within one platform, you can minimise errors by mitigating moves, while saving on time, set-ups and machine shop floor space.

Designed for easy integration within one digital platform, the LMD integration provides a more affordable solution for smaller or growing firms that are looking to adopt new technologies and expand their capabilities without purchasing a brand-new or dedicated additive manufacturing machine.

Avoiding the hit

Remanufacturing, reconditioning and repairing all mean different things. According to the Scottish Institute for Remanufacture, the definitions are:

  • Remanufacture returns a used product in line with new performance specifications and gives the resultant product a warranty that is at least equal to that of a newly manufactured equivalent
  • Reconditioning returns a product to a satisfactory working condition that may be inferior to the original specification and gives a warranty less than the newly manufactured product
  • Repair corrects specified faults in a product and gives a warranty less than the newly manufactured product that may not cover the entire product

Originally, manufacturers would try to repair parts in a bid to save time and money. They might have repaired a part by removing the worn area, using basic, manual welding technologies to build material up and then machining it back to purpose.

With increasingly strict industry regulations, however, it is now commonplace to take the hit and purchase new parts that comply with specifications, which is seen to mitigate risk.

LMD is a more refined method of achieving a remanufacture level process, instead of merely repairing or reconditioning.

Building up interest

We are currently working on several interesting projects, exploring numerous different materials that can improve performance. In one project, we demonstrated 60% enhanced performance through remanufacture.

Designed to combat the high costs associated with die replacement and repair, the DigiTool project seeks to extend lifespan and improve functional performance.

A die might have a lifespan of 25 years at the point of manufacture, but a worn area could have a life expectancy of just 10 years. Rather than scrapping the whole die, remanufacturing the worn section brings the whole die back to a life expectancy of 25 years, potentially saving tens of thousands of pounds spent on buying a new one.

The £1.2m project is the biggest investment of its kind within the tool and die sector for over 40 years. Initial trials have been carried out for analysis of a die for a railway application at Kimber Mills, with plans to remanufacture and bring worn dies back into service.

Crawford Cullen

Crawford Cullen

The AFRC is also working with a major coat hanger manufacturer to improve injection mould tooling performance using LMD. Current issues are causing a rough finish rather than the original smooth product. Part of the issue is that the company's current die manufacturer is overseas, so to have new dies manufactured they are locked into going back to the manufacturer, which owns the drawings and designs.

If the supply chain was located here in the UK, we could more easily access die designs and work with original manufacturers, so we are encouraging tooling manufacturers to invest in LMD to open new markets and boost sustainability.

There has been significant interest from industry, from oil & gas to aerospace, and we are working as part of a consortium to revolutionise the UK's tool and die sector, paving the way for low cost remanufacture within the industry.

Adding opportunities

Powder bed fusion is considered the more glamorous side of additive manufacturing, and until recently there was a lack of attention and skills in LMD. The process is faster to get up and running, however, making it easier for firms to enter the remanufacturing market.

We recognise it might be daunting for firms to invest in a relatively new process, but we're here to assist with the transition, acting as a bank of knowledge and a link to the supply chain.

If we can realise the many opportunities of LMD, we can save time, money, material and factory floor space to offer a more competitive supply chain for manufacturing within the UK.

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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