Every spring is different at William Hughes
Springs have been around for a long time and while the basic types of spring remain the same, modern springs are much more sophisticated in terms of their design, materials and finishes. As their performance and versatility has grown, so has their usage and they are now widely used in automotive applications, domestic appliances, business hardware, aerospace and medical equipment to name just a few.
In today's global markets, economics dictate that standard springs for high volume applications tend to be manufactured in low cost locations. On the other hand, high performance springs are manufactured by specialist companies that can meet the need for bespoke designs, close tolerances, complex shapes, short development times, high quality and low volumes. The aerospace industry in particular has special requirements for materials, specifications, manufacturing tolerances, cleanliness and packaging.
100% setting and load testing springs with the Micro Studio MC54 at William Hughes.
"We don't have any standard springs," said Emma Hughes, Engineering Director at specialist spring manufacturer William Hughes. "All our springs are bespoke and manufactured to customers specifications. Our customers usually contact us when they have a problem and we work with them to help them develop a spring solution that is both efficient and cost effective."
Springs generally fall into two categories, high volume, low cost springs for non-critical applications, for example, as used in the mechanism of a ball point pen - and low volume, high precision springs for critical applications such as aerospace or medical equipment. For these applications, where failure of a spring could have safety or cost implications, performance and reliability are the important criteria.
In most spring applications there are certain mechanical and physical criteria that have to be met. For example the spring has to fit within a specific space, be able to provide the required force and provide a minimum number of operations. Where the spring manufacturer can help is in ensuring that the design is viable in terms of manufacturability, and advising on the best material specification to provide a spring that will meet all the needs of the application at the minimum cost. Involving the spring manufacturer's engineering team at an early stage will lead to economies of production and handling as well as fast prototyping and functional testing.
So let's remind ourselves of the basic types of spring namely compression, tension and torsion and what they do. Compression springs provide a resistive force as they are compressed, a typical example being a valve spring on a car engine. Tension springs are designed to provide a resistive force as they are stretched. They are often used as return springs where the force generated is used to return a mechanical device to its original position, for example on the throttle of an engine. A torsion spring stores energy when it is twisted, for example on the hinged lid of a compartment. Torsion springs can be combined with compression springs to provide added functionality. Depending on the characteristics required, springs can be manufactured in a wide range of materials including stainless steel, brass, phosphor bronze, beryllium copper and nickel-chrome alloys.
As an example of the way the use of springs has grown, look around the interior of a modern car or van at all the places where springs are being used. Starting with the seats, there are springs in the mechanisms to raise and lower the seat bases and adjust the angle of the backrest. All the hinged lids and latches on the storage bins and compartments will have a spring in the mechanism.
In the aerospace industry springs are often used in critical applications such as oxygen systems, access hatches, and the solenoid valves used to control the hydraulic and cabin pressure systems. To meet the demanding specifications for high temperature performance, many springs need to be manufactured in exotic materials such as Nimonic, Inconel and Ni-span. These expensive materials are more difficult to work with than conventional materials and require special machinery and expertise to manufacture with high accuracy and minimum wastage.
To ensure a high standard in the aerospace industry, suppliers need to be accredited to AS9100 and this is now widely adopted as the standardised quality management system for the industry. In addition, The NADCAP (National Aerospace and Defense Contractors Accreditation Program) is an industry-managed approach to conformity assessment of 'special processes'.
[caption id="attachment_650" align="alignnone" width="300"] Kaichang Coiling Machine[/caption]
The Kaichang Coiling Machine extends capability up to 8.0mm wire diameter at William Hughes.
"The demand for specialist springs continues to grow and we are continually pushing the limits of what's possible with spring manufacture,2 continued Emma Hughes. "Our facility here in Stalbridge, Dorset is firmly established as our 'Centre of Excellence' for precision spring making and to meet these challenges we have recently moved to a new manufacturing facility. The 60% increase in space means that we can offer our customers a greater range of services and processes, and respond more quickly to their needs."