Force filter

MILITARY vehicles could be equipped with improved methods for filtering chemical, biological, radioactive and nuclear (CBRN) agents with a new technology under development in the UK.

Domnick Hunter, a manufacturer of filtration and cold sterilisation systems for compressed air and gases, is developing the filtration technology through Parker Hannifin, which acquired the company in 2005. The company has created demonstration models of the technology with help from prototype specialist Paragon Rapid Technologies.

The filtration system is a next-generation version of the regenerative CBRN filter system fitted into Trojan and Titan armoured vehicles, which were the world’s first platforms to have such a systems. The new technology will rely on new filters made of advanced lightweight materials and plastic housings and components that will replace the traditional pressed and cast metal systems.

The prototypes of the device were developed using Paragon’s stereolithography technology along with traditional fabrication and engineering.

The system consists of a series of filter cartridges, assembled into manifolds, with pipe work to connect to the ancillary pumps, valves and HEPA filters. All of this is fitted into a box as an enclosed unit.

The models, which were designed for display at exhibitions, were fabricated with a clear protective case. The case was made from 8mm clear acrylic, to the design of the production enclosure, to serve the dual purpose of protecting the internal components, while being representative of the final unit, including all inlets and outlets.

The manifolds and more complex components were produced in epoxy resin as stereolithography models on Paragon’s SLA5000 machine. Each part was finished by hand. The team added details such as nuts and bolts afterwards to achieve a production look.

The filter elements were built from scratch using conventional model-making techniques with a painted finish. Custom graphics were produced of the Parker logo and applied prior to lacquering.

Wherever multiple components were required, Paragon created a master pattern, through stereolithography, before producing silicone tooling and polyurethane vacuum castings. Many of the parts, such as the manifold elbows, butterfly valves and pipe elbows, were common to both assemblies and were all produced through vacuum casting.

The majority of the pipe work was fabricated from stock tubing, with unique parts such as ‘T’ pieces and ‘S’ bends produced as stereolithography.

All of the piping was fully assembled and painted to look as if it was stainless steel.

A standard HEPA filter supplied by Domnick Hunter was mounted in the top of each unit and this was enclosed within a fabricated acrylic cover thermo formed and bonded so it is fully visible. The heat-exchange units were also fabricated from scratch but they were painted white.

After displaying the models at defence exhibitions, Domnick Hunter has generated enough interest to begin developing the concept for manufacture. The filtration system is being designed not only for vehicle applications but also for use within structures and buildings.

Other companies that work with the defence sector are finding uses for rapid prototyping beyond demonstration models. The US Army recently announced it has contracted five companies to help get working prototypes in the hands of soldiers on the battlefield within weeks of request.

The programme, known as the Rapid Prototyping and Technology Initiative (RPTI), is run by the army’s Armament Research, Development and Engineering Center (ARDEC).

The five companies will share a five-year, $300m (£182m) indefinite-delivery, indefinite-quantity (IDIQ) contract. The group will seek to provide prototypes for ammunition, weapons, energetics, warheads, fire control, sensors and seekers, fuse products, novel weapon concepts, protection, assembly, packaging, demilitarisation and environmentally required waste treatments.

One of the companies, Alion Science and Technology, has announced it will be providing, among other things, prototyping and engineering services to the effort.

Chris Amos, senior vice-president at Alion and manager of the Technology Solutions Group, said: ‘Today’s ever-changing threats on the battlefield, as well as the surges in response to shifting military environments, require ARDEC to provide working lethality and counter-lethality prototypes to its customers within weeks of receiving a requirement.

‘As an accomplished integrator with the management experience, technical skills and history of rapid response to the warfighter, we can provide ARDEC with a comprehensive solution for rapid prototyping and system integration. This will enable ARDEC to provide enhanced responsiveness to the field while improving upon quality and reducing costs.’

Other participants in the effort include Battelle Memorial Institute, Booz Allen Hamilton, Concurrent Technologies and Raytheon.

The RPTI programme is one of several efforts by the US Army to incorporate rapid prototyping technology on the battlefield. The Engineer reported in 2003 on the US Army’s trials of Laser-Engineered Net Shaping (LENS) for repairing bladed disks on its General Electrics’ T700 helicopter engines.

The process uses a high-power computer-controlled laser to rapidly weld air-blown streams of metallic powders into custom parts and manufacturing moulds. Many machining processes such as milling are subtractive techniques, which means they remove material to create components. The LENS process, however, builds parts from scratch layer by layer.

While it can be used to manufacture entire components, the US Army showed it can also rapidly repair or add to existing parts and save them from going onto the scrap heap.