Vacuum forming means design opportunities

Replacing traditional manufacturing methods for aerospace applications, a new vacuum formed cabin dividing bulkhead is the latest in a series of products that are claimed to be lighter, washable and fully flammability compliant. The new partition, which opens up many creative options for airline interiors, had its international launch from STAG Group's stand at last year's Farnborough Airshow.

Not only is the cabin divider more aesthetically pleasing, it creates opportunities for increased flexibility for branding and personalisation of airline interiors. Part of its appeal is said to be the significant weight saving, typically 25% lighter compared to traditionally manufactured partitions. In addition, as just one polymeric material is used in its construction it is corrosion resistant with no adhesives or metal components required.

Advances in vacuum forming materials and tooling technologies have largely been ignored within the aircraft interiors industry. To date there has been a lack of vision and these opportunities have only been exploited in creating parts which have traditionally been vacuum formed, such as seat plastics and document pockets. STAG Group is developing these new technologies for a range of interior components. One of the first products is the new cabin divider/windbreak which has traditionally been flat, uninteresting and utilitarian.

Three-dimensional, multi-coloured partitions can be created and document pockets or drinks holders integrated into the bulkhead design. Bespoke bulkheads can also be produced with tailored advertising or decorative finishes, giving airlines the opportunity to individualise interiors by using STAG Group's RACEPrint process. By using this technology, each unit can be printed to customer specifications, including tailored advertising and decorative finishes, which are durable and tamper-proof. This allows aircraft operators a wide range of design and branding options.

<Light and low cost>

Rick Crosby, STAG Group's unit director of the Bristol manufacturing operation begins by showing me a vacuum formed bulkhead that is two-thirds of the weight of its existing traditional partner.

“It's lighter, much cheaper and comprises fewer parts,” he claims. “The important benefit that I'm excited about is the fact that vacuum forming gives you shape and form – these parts don't have to be flat anymore. It's the way forward for these types of products. Vacuum formed materials now pass all of the fire, smoke and toxicity (FST) requirements of a full aircraft interior. Combined with the CNC capabilities of detailed tooling, the size and capability of vacuum forming have really advanced. This has allowed us to look at how we can manufacture large format toleranced thermoforming (LTT) and how we can apply it to the aircraft interiors market.”

I'm interested to know how STAG Group overcomes the traditional issues with vacuum forming, such as tolerance variability between parts. Crosby reckons it's mostly down to a clever use of tooling design.

“We've also carried out surveys of what happens to the vacuum formed material when the vacuum process is undertaken to better predict material thicknesses and stresses. These vary depending upon the draw type and angle. Additionally, thermal expansion is not linear; it depends upon the forming geometry. We have developed formulae to predict these, which allows for a greater accuracy of joint when manufacturing bulkheads for example.”

Crosby goes on to add that there are many interior parts, traditionally made from composites that are well-suited for manufacturing using the vacuum forming process. Along with the bulkheads, there are applications for entire toilet modules and moveable class dividers too. STAG Group can also design interior parts to accommodate more stiffness by inserting aluminium laddering inside the vacuum formed part to allow the airline customer to hang additional structures from them.

“We are now capable of making very large parts and any shape required. The only limitation is the tool designer's imagination. We are not restricted by having to use flat composite board to make these parts. The vacuum forming process gives us the freedom to integrate tablet holders and company logos onto the bulkheads.”

So have extra aspects of functionality been enabled through the use of vacuum forming, as opposed to other methods, such as pre-printing of component surfaces and integral metal fastenings?

“Most definitely. As the part can have every element built into the shape - for free, it is simply the cost of the tooling that varies, provided the aspect can be accommodated within the forming geometry of course. Bulkheads can now be shaped to suit a customer need; they no longer need to be flat. We also hope that the competitive pricing could allow for seasonal changes to advertising, or even whole bulkheads with a specific theme being commissioned.”

<Signed and sealed>

STAG's vacuumed formed parts are designed to be capable of being sealed gluelessly. Crosby reckons a traditional bulkhead can weigh around 15kg, whereas a bonded one is about 11.5kg. However, the glueless technology means the weight is reduced to just 10kg. The company also offers its RACEPrinting process, where it takes a standard colour material and prints into it anything required so it appears on the part surface.

“We can vacuum form anything onto the material to produce a finish. We don't just print into plastic, but into metal, leather and cloth – anything really. Direct printing into the metal or powder coat offers us the potential of playing in both the retrofit and OEM markets.

“Combining the LTT with the glueless technology and the RACEPrint process gives us a product that is completely unique. We've also found a way so that the strengthening ladder can be made from composites simply by using a core and bonding relatively rigid FST-compliant plastics to it and then CNC machining it to produce an incredibly rigid structure.”

STAG Group has a number of airlines and OEMs interested in the products. It is also working with a well-known airline operator to produce a generic supplemental type certificate (STC) package for the Airbus A320 and Boeing 737 where there will be view screens, document pockets, tablet holders and logos. STAG Group simply specifies this as a dash number to avoid re-certifying the product.

“Vacuum forming technology is already well-known in the aerospace industry, but we've managed to find the right applications and perfected them for the size and the configuration of aircraft,” Crosby concludes. “Although the technology itself has been around for some time, it hasn't had much of a push from the design organisations attached to it. And from a materials technology standpoint, it's only the last few years that the plastics manufacturers have perfected truly workable OSU toxic smoke compliant materials that lend themselves to making larger parts. We've taken advantage of a series of events that makes it work the way it does. All these factors have combined to give us a truly unique product.”

www.stag-aerospace.com