Purchasers of business jets are notoriously picky.  After all when you’re laying out $45 million to $150 million for shiny new aircraft, you want some say in how it’s going to look and operate.

Jeff DeGrange, a Stratasys vice president with a long history of applying additive manufacturing technology to the aerospace industry, puts it this way: “The configuration of a business jet is unique to each customer.  If, for example, the business jet community is building 500 jets for 50 different customers, each of those customers will want the cockpit configured in a certain way, a unique look and feel to the cabin, and a customized set of accessories and extras.”

This customization, he says, encompasses everything from visible parts like seats and fixtures, to all the unseen but essential systems and subsystems that exist behind closure panels, including heating, ventilation, cooling and a wide range of electronics. And, once all these customized parts are in place, they have to be maintained over the life of the airplane, usually about 20 to 30 years.

“This is a classic low volume, large product mix problem, and it’s ideally suited to additive manufacturing (AM),” says DeGrange.

Creating these components using traditional subtractive manufacturing techniques, including a major investment in hard metal tooling, is expensive and inflexible. When the final tool is made, in many cases, it does not meet final requirements and must go back for rework or redesign.

Product Lifecycle Support

With AM, physical tools and jigs are replaced by CAD files on a computer, allowing multiple simulations to be run to make sure the tool is configured properly before the components are manufactured. The ability to easily store and retrieve these CAD files also provides what DeGrange terms “product lifecycle support – what the aerospace industry call sustainability of the airplane.”

He explains: “Whether it’s a business jet or a commercial or military aircraft, after so many flights maintenance crews will install new flight control or avionic boxes – for example, upgraded electronics that allow the pilots to detect unfavorable weather conditions or turbulence more quickly.  This in turn requires new tooling for the various ducts because these highly sensitive electronics have to be maintained to very strict temperature operating conditions.  Or, in ten years, you may have to install an upgraded computer in the aircraft requiring a whole bunch of new parts to heat and cool the computer. So the question is, how do you do that cost effectively without making major investments in hard metal tooling?”

The answer, of course, involves computer-aided design and additive manufacturing. One of the biggest enablers in this aerospace manufacturing revolution is the development of new, extremely strong, corrosion resistant, lightweight materials. One of the most promising of these is carbon reinforced plastics (CRPs), a fiber-reinforced polymer that contains carbon fibers. DeGrange says the Holy Grail of CRP is to endow the substance with the same properties as aluminum but with 50 percent less density – in other words, the same products made of CRP will be just as strong but 50 percent lighter than their aluminum counterparts.

For example, he says, when you board an airplane the first thing you see are all those seats, and each one contains a machined aluminum frame.  Typically a seat frame weighs 26 pounds. Cut that by half to 13 pounds using CRP and then multiple by the 100 or 200 seats on a typical airplane and it all adds up to significant savings in weight and fuel economy.  

But the savings don’t stop there.  For example, under the skin of the aircraft’s wings are its fuel tanks and wide variety of pumps and housing made out of metal.  These parts, which are not load bearing, could also be made out of CRP, again saving weight and cost.

Ultem's Many Uses

A number of commercial, business and civil aircraft are making widespread use of CRP in structures, taking advantage of the strength, light weight and corrosive-resistant properties of the material.  Fused Deposition Modeling™, a Stratasys invention, is an ideal technology to make these complex designs and geometries.  Aerospace manufacturing engineers are now employing FDM for various applications such as jigs, fixtures, check gauges, and even as end use parts. FDM technology can work with a variety of thermoplastics designed for aerospace applications - like Ultem.  

The fact that these parts can be printed using additive manufacturing means additional savings and a shortened supply chain.  As a result, DeGrange sees this technology increasingly moving into other industries, such as automotive.  AM is a natural fit for Formula 1, Indy and NASCAR race cars, followed by adoption by high-end performance production automotive companies.

Another major application of AM in aerospace targets support and maintenance.  During their travels in the air and on the ground airplanes get dinged – they run into birds, service vehicles bang into them, parts break, dents need to be patched, non-standard parts need to be replaced – it’s a constant process.  

DeGrange says this use of AM is gaining traction.  Some airline depots are now deploying AM technology right next to their traditional drill presses and metal forming machines. This approach is now a standard practice in the U.S. Navy Naval Air Systems (NAVAIR) Fleet Readiness Centers to keep the flying Navy in the air.

AM helps provide the customized tooling needed for maintenance, overhaul and repair of in-service vehicles. Comments DeGrange, “AM’s role in assembly, fabrication and tooling is huge, and it’s only going to grow in the future.”