It has also equipped the business to complete numerous complex structural projects involving titanium tube – including roll-cage structures for military vehicles and aerospace components.
The machine, a Unison Breeze 130 mm ‘large diameter’ multi-stack tube bender, was purchased to help SST produce high-performance optimal-flow exhaust systems for Formula 1, IndyCar and other motorsport sectors. With a pedigree in motorsport components and a powerful new tube bending machine to hand, however, SST’s thoughts quickly turned to driver safety. The material control, production parameters and dimensional tolerances provided by the all-electric Unison Breeze tube bender, combined with SST’s experience in the development and manufacture of ultra-precise fabrications, led to the company’s Halo design securing FIA conformity for use in Formula 1, Formula 2 and Formula E motorsport and being adopted by several race teams. SST’s Halo design requires the precise bending of titanium tube of 4 mm wall thickness.
Titanium, however, is notoriously difficult to bend. With low uniform elongation typically requiring a much greater bend radii than other metals, titanium doesn’t readily lend itself to being formed – a characteristic that makes creating tubular structures for aerospace and motorsport applications particularly challenging. For successful tube forming, the material must be compressed on the inside of the bend and stretched on the outside, while wall thinning and ovality of the tube have to be kept to very tight tolerances.
Traditionally, ‘hot bending’ - a process involving the use of super-heated tooling - has been used to overcome the challenges of bending titanium. However, the very process of hot bending presents a number of issues. For example, the use of super-heated tooling requires considerable care and can present a hazard to operators; complex modifications must be made to bending machinery, and tooling heat-up times are lengthy. However, with advice and application support from the technical team at Unison, SST was able to develop a cold-bending process for their Halo design that allowed for the low elongation of the metal and delivered precise results.
“To successfully cold-bend titanium, factors such as material quality, tooling configuration, machine design and flexibility of control need to be considered,” comments Unison key account manager, Steve Haddrell. “This is because any variation in material quality, any lack of rigidity in the mechanics of the bending machine and any failure to achieve repeatability time after time will invariably lead to failure. With material quality assured, it really came down to working with SST to establish the correct tooling configuration and programming of the Unison Unibend machine operating system.”
Based on its experiences with the 130mm machine, SST has also purchased a smaller 65 mm Breeze model for the production of more intricate pipework and parts for aerospace and gas turbine applications.