Page 26 - 3D Metal Printing Winter 2018

3D FEATURE
GE Additive
Efforts
Taking
Flight
This advanced turbo prop is a result of
disruptive engineering, with nature providing key
sources of design-engineering inspiration. The outcome includes 35-percent additive content, a noteworthy parts- count reduction—from 855 to just 12—and lessons that will help advance additive manufacturing.
BY JOE JANCSURAK, ASSOCIATE EDITOR
The grid structure of this C-sump was printed using direct metal laser melting (DMLM) and is based on plant-cell structures. Applying biomimicry, GE Additive engineers were able to reduce part weight while maintaining strength. The C-sump is part of the main load path from the propeller to the engine, and eventually to the airframe. It holds the bearings for the free turbine, so essentially it is what holds the propeller onto the airplane.
an aerodynamic flow pass, allowing air to exit the engine with minimal pressure loss, the exhaust case must be designed with enough strength to withstand the pressure of the airflow traveling through the engine,” he explains.
“If we had designed the ATP exhaust case using subtractive-manufacturing techniques, we would have had to design the entire case with a thickness dictated by the weakest point, which adds unnec- essary weight. By utilizing additive, we designed significantly more complex aero- dynamic shapes and then added features for structural stiffness. The exhaust case has a very thin liner, which is the aerody- namic shape, and then we printed external spars on the case that provide the required
In 2015, when GE Aviation’s Additive Technology Center in Cincinnati, OH, began developing the advanced turbo prop (ATP) for a Cessna Denali aircraft produced by Textron Aviation, Wichita, KS, manufacturing methods and mate- rials didn’t pose the greatest challenges from a design and engineering perspec- tive, says Josh Mook, innovation leader at GE Additive.
“It was more about unlocking the mindsets of our engineers, and getting them to a place where they were willing to take hold of additive manufacturing (AM) and embrace it,” says Mook. “Devel- oping a jet engine involves a lot of enter- prise learning over the years, and AM is all about disrupting that. Additive takes systems and consolidates and redefines them.”
Indeed, the ATP, now being tested and
expected to enter service in 2019, repre- sents the efforts of hundreds of engineers, and features 35-percent additive content and a huge parts-count reduction—from 855 subtractive-manufactured parts to just 12 AM parts.
“Additive content (using Arcam elec- tronic-beam melting machines and Con- cept Laser powder-bed laser melting machines) literally cuts across the entire engine—from front frame to exhaust ducts,” says Mook. “There is no structural casting; every structure is additive. The result is holistic.” In 2016 GE became majority shareholder of Arcam AB, Möin- dal, Sweden, and Concept Laser, Licht- enfels, Germany.
Gordon Follin, GE’s engineering man- ager for the ATP program, singles out a part exemplifying the holistic nature of the project: the exhaust case. “Serving as
24 | 3D METAL PRINTING • WINTER 2018
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