Spring squareness controlled with measuring technologies

19 June 2007

William Hughes Ltd has been manufacturing springs for many years, but as new and more demanding applications are developed, this brings new challenges to the design and production engineers. William Hughes believes that if there is a demand for a product, its engineers will find a way to satisfy that demand using their experience, knowledge and resources to find potential solutions to issues which have often been unresolved in the past.

For example, springs being manufactured by William Hughes are used in vital items of aerospace equipment including oxygen systems, access hatches and the solenoid valves used to control the hydraulic and cabin pressure systems. With these essential and critical applications, it is important that when springs are manufactured the ends are ground to provide a precision flat face. In certain applications, any variation in the ‘squareness’ of the ground end can cause problems with the equipment in which they are used, and in some circumstances, this could result in a functional failure.

So William Hughes had two problems to address. Firstly the production process had to be changed to ensure more accurate ‘squareness’ and this was corrected by developing a process of secondary operations. Secondly, the traditional methods of measuring ‘squareness’ such as the use of Shadowgraph systems were not providing accurate and consistent results, so a better measuring system was needed to match the customers specifications. In the search for a suitable solution, William Hughes conducted a worldwide review of the available technologies. Several options were considered but only the latest high technology camera/PC based measuring system would deliver the speed and accurate results that were needed.

In order to get the best results from the investment in the latest measurement technology, it was also necessary to provide a dedicated area of the factory for the new machine to provide a controlled environment which was separated from the main production area.

The new measuring machine enables compression springs to be inspected and measured, instantly and accurately determining the length, outside diameter, end coil profile, ‘squareness’ and parallelism of the spring when it is stood on its ground end face. By comparing the measurements obtained from the component, with the dimensions and tolerances on the engineering drawing, the Windows-based software package produces a detailed report showing any dimensions that are outside the specified tolerances.

The new machine has improved the quality of manufacture by enabling adjustments to be made to the production process before bulk production is authorised. Scrap has been significantly reduced by ensuring that any spring production meets the exacting requirements of the customer. When the correct specification is being met, the machine saves the end coil profile and this can be used as an overlay/model for future production so saving on set-up time.