Tooling up to get the basics right

The UK aerospace industry is on a high. A recent report from ADS shows an increase in turnover to £31.1 billion for 2016. Productivity is rising, and the industry is employing increasing numbers of apprentices and trainees: today, 60% of aerospace companies offer apprenticeships compared with 15% in 2009, says the report.

Top line figures like this reflect what is happening at ground level. Generating this kind of growth relies on getting the fundamentals right – in everything from employee skills to tooling.

Tooling may seem an impossibly broad term, but it describes the process of designing and engineering the tools needed to make parts or components. Manufacturing tooling is critical to engineering success, and comes in many different types: work holding tools such as jigs and fixtures; cutting tools, for milling, turning and grinding machines; punching dies for cold forming, forging, extrusion machines and presswork; sheetmetal welding fixtures; and inspection fixtures.

Every aspect of a finished part relies on the precision of the tooling – from quality and properties, through to process conditions such as manufacturing repeatability. Yet making high quality tooling – especially for high speed, multi-spindle CNC machines and cold forming systems – is complex and demanding. Computer-aided design and modelling software can assist the process, but does not replace the insight of experienced tool and die makers.

Effective design

Effective tooling design requires a deep understanding of the conditions encountered during production. This then informs the design, type of materials and construction of the tooling, as well as potential modifications to process criteria.

The goal is to make finished parts that meet the required quality and specifications – in the volumes and lead times demanded by the customer, at competitive cost. Designers must consider a range of factors, including: Tolerances in the finished part, which will affect tooling configuration; Mechanical strength and rigidity of the tool, which is essential for the accuracy, repeatability and quality of the workpiece; Cutting tool strength, which must withstand high machining forces, especially in high volume production; Sacrificial or weak links, to resist wear and prevent damage to indexing tools; Machine tool speed, feed and size, which determine the properties of each tool set.

Counting the cost

Modern engineering techniques have reduced the cost of conventional tooling for CNC machining and precision cold forming, making it relatively affordable. Of course, there are exceptions to this, but they tend to be for complex, low volume parts, or in applications that require specialised or difficult-to-engineer materials. Even in these cases, the aerospace sector can reduce costs through intelligent design and careful control of production processes.

Overall, the idea that tooling is an expensive, cost-prohibitive process is no longer accurate. This misconception is based on past performance. For instance, cost and time delays were common because development was an iterative process, with improvements made in a succession of prototype stages. While the concept is still applied today, elements such as tool design, analysis and testing can be done virtually, using software tools such as SolidWorks or DEFORM, instead of in the toolroom. This eliminates ‘trial and error’ and allows tooling to be made ‘right first time’.

Even companies with fast, efficient toolmaking procedures can benefit from this type of software. It shrinks the development time for tooling and can reduce costs – by eliminating several stages in the design process, while maintaining (or even improving) the part quality of the machined components.

Tooling transparency

Another historical headache has been confusion over the cost of tooling, and how it is charged for. Because there were no standard definitions to guide cost calculations, suppliers adopted many practices to calculate the cost of developing tooling. Few were consistent or transparent; most depended on a small number of experienced toolmakers and estimators. This made it difficult for design engineers to budget appropriately and, as a result, often failed to keep costs under control.

However, calculation software has now made it easier for those same engineers to assess the time, labour and materials required to produce individual tool sets, and this has led to more standardisation across the sector. Companies that take a professional approach to tooling will already have a consistent approach to presenting tooling costs to their customers, much to the benefit of aerospace manufacturers.

Our approach at Dawson Shanahan is to explain how costs are calculated, explain them to the customer, then find the best solution for both sides. It could be a one-off charge, for instance, or an agreement to amortise the cost of tooling across the lifetime of the project, depending on the application. A critical step in the process will always be to consider how the cost of both tooling and the overall project can best be reduced, while maintaining critical factors such as delivery deadlines and part quality.

This is an area in which it is critical to ensure that cost saving does not turn into cost cutting. Slashing tooling cost can actually lead to higher part costs during the production phase. It is usually better to invest slightly more in the tooling if this significantly reduces part costs. This is particularly relevant in high volume projects that are common in aerospace manufacturing.

It is equally important at this stage to consider the method of manufacture: although tooling for precision cold forming is slightly more expensive than that of conventional CNC machining, for instance, cold forming is generally more cost-effective – as it is faster, uses less material, and produces a higher quality component that requires less post-processing. This results in lower part costs, while the process uses less energy while generating less waste.

This kind of value proposition shows that focusing on essentials such as tooling design will help industries like aerospace continue their upward growth.

www.dawson-shanahan.co.uk