January 28, 2021
Unison tube bender makes light work of SST’s life-saving Halo system
Investing in a Unison Breeze all-electric CNC tube bending machine has not only assisted Oxfordshire-based SST Technology in becoming the only British-based precision fabricator authorised to produce the life-saving Halo titanium driver protection system, as used in Formula 1. 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 exceptionally tight material control, production parameters and dimensional tolerances provided by the all-electric Unison Breeze tube bender, combined with SST’s considerable 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.
Notoriously difficult to bend
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. By contrast, Unison’s infinitely controllable and robust all-electric machines enable the safe, precise cold bending of titanium. With advice and application support from the technical team at Unison Ltd, SST were therefore 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 exceptional power, optimal rigidity, precise mechanical motion and all-electric control for accurate, effortless repeatability, we knew the 130 mm Breeze was the ideal machine for precision-bending SST’s Halo design. 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.”
Delivering significant benefits
“Investing in the 130 mm Unison Breeze machine has clearly paid dividends,” says SST Technology’s Group Business Development Director, Daniel Chilcott. “Tool changes are rapid, programming is incredibly user friendly, while the automatic setup ensures uncompromising levels of accuracy and repeatability. Sufficiently impressed with the capabilities of our 130 mm machine, we have also purchased a smaller 65 mm Breeze model for the production of more intricate pipework and parts for aerospace and gas turbine applications. Combining this capability with our AS9100REVD accreditation means we are perfectly set up to support leading aerospace propulsion, fluid and air system OEMs.”
Intelligent tube manipulation
The Unison Breeze 130 mm tube bender purchased by SST is well suited to manipulating exotic alloys such as titanium and Inconel, as well as Super-Duplex stainless steels and provides high-quality thin wall bending. Multi-stack tooling allows the most complex of parts to be formed in one uninterrupted manufacturing cycle, while Unison’s bar code scanning system ensures that only the correct tooling is installed. The standard-fit rise and fall pressure die can result in significant savings in tooling costs and allows tools of very different radii to be used on a part within a cycle. The tube bender can be programmed manually or from CAD data using industry-standard IGES or STEP files.
“At Unison, we are often invited to advise customers on particularly challenging tube bending projects,” concludes Steve Haddrell. “That’s partly because of the immense capabilities offered by our tube bending machines. Assisting SST on establishing the optimal tooling configuration of their Unison Breeze machine for the production of the life-saving Halo device, however, is one of the most rewarding projects we have been involved in.”