Click here to see this story as it appears in the July/August 2017 issue of MCDP

Layer by layer deposition of materials to manufacture parts, better known as 3-D printing or additive manufacturing (AM), has been flourishing as a fabrication process. With this method, complex geometries can be created that were not previously possible for lightweighting, more efficient organic shapes and even cellular structures.

Originally confined to models and prototypes, AM has more recently been used for creating molds, tooling and even direct part production. Direct manufacturing of metal parts with AM is not generally considered a mature technology, however, and indirect methods may offer dramatic benefits through the combination of state-of-the-art AM and age-old metal casting.

This dual approach was evident in a recent project for the U.S. Air Force. The service branch required replacement aluminum piping parts for a legacy aerial spray system. The original supplier was no longer available to provide the fabricated replacements, and the harsh environment of the aerial spray system, which was both corrosive and erosive, lead to increased replacement rates.

At first, the Air Force fabricated replacements by modifying and then welding three individual parts into a single unit. Each part was for one of six unique systems operated by the Air Force and consequently required custom fitting for the repair.

A better, more efficient solution was needed.

Building the Team
The Air Force Research Laboratory (AFRL) and America Makes lead a congressionally directed project focused on the utilization of AM technology in Air Force depots to demonstrate via case studies and best practices how AM integration and advanced manufacturing practices may increase throughput and reduce costs. The project is called Maturation of Advanced Manufacturing for Low Cost Sustainment (MAMLS).

Phase 1 of the project kicked off in 2016 with one task focus of demonstrating AM technologies for tooling applications. The University of Dayton’s Research Institute (UDRI) and Youngstown State University (Youngstown, Ohio) leveraged the Youngstown Business Incubator (YBI) to assemble an experienced casting team which could demonstrate the utilization of 3-D sand printing (3DSP) for rapid tooling manufacturing and case study execution. The team includes the University of Northern Iowa’s Metal Casting Center (UNI) as the technical experts on 3DSP, AFS for workforce development outputs and additional technical support, Youngstown State for reverse engineering and COTS sensor integration work, and several metalcasting companies who are early adopters of the technology such as Humtown Products (Columbiana, Ohio); Lite Metals (Ravenna, Ohio); and Product Development and Analysis (Schaumburg, Illinois).

The Air Force directs the work, UDRI and YSU then direct the MAMLS Casting Team to execute specific MAMLS casting work.

Finding the Solution
The U.S. Air Force’s 910th Air Wing Division has the only large-area, fixed wing aerial spray mission in the Department of Defense. During a site visit with 910th senior maintenance staff, YSU professors noticed a cast header system on the back of an aerial spray system. The aerial spray system is loaded on a C-130 and each system has customized headers through which fluid flows under pressure.

The sealing points of the elbows are required to be uniform to ensure no leakage. Any leakage in the system would cause an aircraft to be removed from a mission to be cleaned extensively. The part is critical to the aerial spray system.

In discussion with the 910th maintenance crew YSU, learned that three aluminum cast elbows were special ordered, cut and then welded to fit a specific sprayer system. While the 910th maintenance team were experts at this work it experienced long lead times to acquire the elbows from existing vendors.

YSU and UDRI engineers utilized reverse engineering capabilities like a handheld scanner to acquire dimensions for each of the existing spray system headers. Then, YSU utilized CAD software to create 3-D files for a single cast part that would leverage 3DSP tooling to address customization requirements and facilitate part consolidation. The MAMLS Casting Team reviewed the YSU design and UNI’s team and Covy Design and Services (Columbiana, Ohio) developed some mold designs that would minimize post processing.

Lite Metals performed the casting work as the team made several part artifacts. YSU also poured some part artifacts at its micro-foundry to educate students on this technology approach. The 910th conducted flow and pressure testing after Lite Metals completed post processing and heat treatment with another Ohio small business.                   

Benefits Realized
The cast replacement part designed and developed through the MAMLS project maintains the original specifications and eliminates the need for hard tooling. By leveraging additive manufacturing, a sand mold was printed specifically for the system without increasing the cost. Lead time was reduced for fabrication from 10 weeks to four weeks, and the cost per part for an order of five—with all development expenses included—was $2,170, which included printing each mold and pouring each casting.

By comparison, traditional hard tooling was quoted at a cost of $12,000 and a 10-week lead time, with a per part cost of $3,140. The associated weldment required only one day to create at a cost of $2,050 per part, but fabrication incurred a nine week lead time.

The surface finish of the part cast with the printed sand molds was sufficient for the application and eliminated the additional requirement for machining. The casting was designed for immediate use after removal of the gating system. The new single piece casting is more durable than the welded assembly and has improved dimensional tolerances.

Rapid casting was demonstrated to be beneficial for the Air Force in terms of improving cost and schedule and reducing post processing. Many critical weapon legacy systems face issues with securing replacement parts, which often take them out of service and reduce warfighter capability to respond. This activity, besides being a cost-effective solution, demonstrated to the Department of Defense the potential that technologies like additive manufacturing can be utilized to solve supply chain issues with metalcasting.