Extending the lives of engineering masterpieces

You don’t have to be a history fan or an engineer to get excited by the sight of a WWII fighter plane in flight or find that you’ve got an extra spring in your step after hopping off a vintage cable car. There’s something inherently appealing about seeing these vintage machines in motion.

Additive manufacturing is a flexible technology. It's driving a fundamental rethinking of engineering and design for manufacturing, and because you can create just about anything using AM, it’s also proven to be a superb tool for the reverse engineering of vintage parts for all manner of historic vehicles.

Rob Connelly, a former Vice President of Additive Manufacturing for Proto Labs, owns a very rare Mustang P-51D fighter plane from 1944 named “Hurry Home Honey.” 

As you’d expect, replacement parts for an 80-year-old plane of which few were made in the first place are difficult, if not impossible to find. However, it’s exactly the kind of assignment AM is ideal for. In a report from engineering.com, Connelly shared how he, together with a friend and fellow pilot John Murray, president of Concept Laser Inc., (now acquired by General Electric’s GE Additive division), developed a plan to use AM to recreate the plane's exhaust ports. 

An airplane exhaust port is, of course, subject to extremely high temperatures and no doubt considerable mechanical stress, too. A few years ago, printing a part using engineering-grade thermoplastics would have been challenging. Today, though, the high print temperatures demanded by a material like PEEK have been met with water-soluble support-material breakthroughs. 

To reverse-engineer the part, they worked with Phoenix Analysis and Design Technologies (PADT), in Phoenix, Arizona, who scanned the existing part and ran thermal and flow simulations on the digitally created part. 

The result was a part that was stronger, more durable, with no weld seams, and improved exhaust gas flow compared to the original.

The same process Connelly used to create the Mustang part is being used by GE in their Global Research Program for the US Navy. 

Modern aircraft are far more complex, of course, but like the PT Mustang, they put a lot of mechanical stress upon all manner of parts. 

For active military craft, the far faster process of creating a 3D print vs. fabrication using traditional methods is a crucial advantage. GE is working to further increase that speed advantage by embedding sensors to monitor the build and allow the printer to self-correct, speeding up production.

Back down on earth, AM is playing a part to help keep the trains on time. Deutsche Bahn’s Class 294 locomotive has been in service since the 1960s, making spare parts for some components increasingly difficult to source. 

Take the wheelset bearing cover, for example. Traditionally, a part like this would be created using a casting process, albeit at a very high cost-per-part. Enter 3D printing to the rescue, putting the train back on track and avoiding lengthy and costly downtime. 

Meanwhile, the first 3D-printed parts inside in-service passenger trains are rolling through the United Kingdom. The parts include armrests and grab handles, which have been installed on Chiltern Railways trains. 

The program’s success prompted the railway to look at how 3D printing can be used to customize interiors, such as seatback tables with information on the location of the toilet in Braille.

Naples, Italy is home to another reverse-engineering success. The Neapolitan public transport company Azienda Napoletana Mobilità (ANM) has new 3D-printed "trolley heads," the part that connects a bus to the network’s overhead power lines.

Italian firm 3DnA produced the part utilizing two different printing systems to create the metal and plastic parts needed for the trolley heads.

Porsche put auto-enthusiast imaginations into overdrive with the announcement of a new program called Sonderwunsch. As detailed in Car and Driver, Porsche Classic, the German automaker's restoration and parts division, and Exclusive Manufaktur, its bespoke division, will work together to build customers' cars into special one-off creations.

Porsche has for some time been using AM to manufacture rare parts for its vintage models. It seems only a matter of time before on-demand parts for a range of consumer goods become more widely available. 

"We've heard a lot about printers in places like auto parts stores," said Jeff Cernohous, Ph.D., COO, Infinite Material Solutions. "A digital file saves the considerable cost of inventory for suppliers and retailers.

Other carmakers have been using AM to give customers the option of specifying custom touches on new cars. But the new Porsche program is a big leap forward on the idea of mass customization — if you’ll allow anything Porsche does to qualify as “mass” — by making custom changes possible on everything from interiors to mechanics.

Using AM to create a unique sports car is an enthusiast's dream realized. The more quotidian work of aircraft MRO (maintenance, repair, and operations) dovetails with another animating social force: sustainability. 

The cost savings realized through the utilization of AM can conserve resources, too. Digital manufacturing offers the promise of a world with less waste, less inventory, and less CO2 emissions, which is no small thing given nearly one-third of CO2 emissions stem from manufacturing.

Another example of how AM and other contemporary manufacturing techniques can point to a brighter future for past technologies is Pittsburgh-based Wabtec Corp’s work on battery electric locomotives. In an Industry Week article profiling the company, Wabtec CTO Eric Gebhardt explains how AM is helping the business maximize its design work. 

“Considering the type of products we are manufacturing, such as heat exchangers, we have the opportunity to get into these geometries because, with additive, complexity is free,” he said. “It actually costs more to print just a square block than it does to print an intricate lattice pattern. Because it's all really just around how much material you're using and how much time it takes.”

AM has proven itself a versatile tool, whether driven by an enthusiast's passion or operational economics. There's every reason to expect 3D printing applications to continue to expand — maybe even to a store near you.