Making Parts Layer by Layer May Improve Military Acquisition and LogisticsAugust 2010
Topics: Acquisition Management, Technological Innovations, Systems Engineering
When the military needs a critical piece of equipment for a repair in-theater that isn't readily available, the missing parts could jeopardize an important mission. To get the missing pieces, one traditional solution involves using strategically placed warehouses stocked with replacement gear. Another method is to pay a contractor to make a batch of parts on demand. The most common method is for the Department of Defense to pay a supplier for a guaranteed level of performance and system capability and let them manage supply levels.
"The last method is called performance-based logistics and has been somewhat successful in meeting performance requirements," says James Barkley, a MITRE lead software systems engineer. "It's also expensive and often includes the cost of warehouse facilities and personnel."
A better idea, thinks Barkley, is using a process called additive manufacturingsometimes called 3D printingto quickly make replacement parts. Additive manufacturing produces parts by building up layers of a part's cross sections rather than removing material, as with conventional machining operation such as milling, boring, and drilling. A single additive manufacturing machine can produce an extremely wide range of partsit just needs the computer-aided design (CAD) data to make any given part. Depending on the specific process and materials, the parts can be simple plastic objects, or intricate metal parts for cars and aircraft.
Barkley leads a MITRE research project called MakeOne that uses 3D printing as its core, and which could cut days off getting critical parts to the field. (See "Supporting a Continuous Supply Chain" and "Growing the Seed of an Idea," below.) Depending on its use, a part could be made to specifications that are "good enough" for temporary use, or made to more rigid specs for a permanent replacement.
"You can build parts with complex geometries without conventional tools and fixtures," says Barkley. "That reduces total manufacturing time, reduces waste, and tends to be more energy-efficient."
A Key Click Produces a New Part
One form of additive manufacturing uses a machine similar to an ink jet printer. The printer deposits a layer of resin on a support table according to a computer-directed design. An ultraviolet light cures the resin into a thin solid layer about as thick as copy paper. Successive layers are added by lowering the support table and printing a new cross-section layer until the part is complete in three dimensions. Other types of additive manufacturing include:
- sinteringheating powdered metal below its melting point until it forms a solid mass
- melting fusing particles together with heat
- spray depositionbuilding solid objects with layers of finely sprayed molten metal
- stereolithographythree-dimensional printing process that makes a solid object from a computer image by using a computer-controlled laser to draw the shape of the object onto the surface of liquid plastic
- laminationbonding solid layers together as with plywood
Additive manufacturing gives designers the ability to make devices that have moving partswithout the need for assembling separate pieces. The printing process allows pieces that move inside a product to be made at the same time. This greatly simplifies the manufacturing process by eliminating molds and dies for parts that must be made separately and assembled later.
Ultimately, Barkley envisions a soldier or logistics officer at a strategic parts depot clicking a computer key to select a replacement part from a catalog displayed on a terminal. The soldier pulls a secure computer file for making the part from Materiel Command Headquarters in the United States and downloads it to a 3D printer close by. A plastic part is printed by a plastics-based printer, or a high-grade metal part is printed by a system using electron beam melting. (See "Concept of Operations," below.)
"The most powerful thing about additive manufacturing," says Barkley, "is that it possesses the potential to be a completely automated process. However, it will take a lot of systems engineering work to make full automation a reality."
Using Research to Overcome Challenges
As with the process itself, 3D printing in-theater still has a few layers to add before it becomes a regular part of the supply chain process. To succeed, military equipment makers must accept the additive manufacturing process so that their computer-aided design files can be used in the field; new data standards must be developed and accepted for computer-aided design processes; and 3D printing must be simplified for automation. Additionally, network architectures must be developed for selecting and transmitting electronic files for a variety of parts in different sizes and materials.
"In general, manufacturers perceive additive manufacturing as risky for producing operational parts because there are many unknowns about it," says Barkley.
To respond to their concerns, MITRE is designing a semantic data model that helps designers understand all the relationships and attributes of additive manufacturing equipment and materials. For example, different types of printers use different material (such as plastic, ceramic, and metal). The data model catalogues materials according to their properties (such as chemical, mechanical, electrical, thermal, and optical). "Then we roll that information into probabilistic models," says Barkley. "That shows how long a part might last in a specific operating environment using a certain material on a specific machine."
Technology Readiness Level Is Crucial
One of the team's findings is that an additive manufacturing machine can produce parts that can work well in an operational environment. Such a machine would have a Technology Readiness Level (TRL) of 6 or higher. (TRL is a scale from 1 to 10 that indicates how mature a product or technology is prior to incorporating that technology into a system or subsystem.) However, when an additive manufacturing machine is integrated into a larger system, the system's TRL falls to unacceptable levels.
"People are still using these things like a traditional machine-shop tool," says Barkley. "You give your product design to the shop person, and they will manually feed it into the machine while managing and monitoring the print process. That's a long way from the ease with which you can print a 2D document to your network printer from your desktop."
The overall challenge is building a networked system that's robust enough to produce high-quality parts that can be operated by someone who isn't a trained technician. The 3D printers must be integrated into a system that automates the machines and uses a consistent file format. To help develop standards for consistent file formats, test methods, and a variety of other additive manufacturing related items, Barkley is working with the American Society for Testing and Materials International. (See "MITRE's Barkley on New ASTM International Committee" below.)
So far, the team members have completed a catalog of machines and materials for additive manufacturing. They also created a semantic data model that includes materials, physical properties, test methods, modeling software, and how these things relate to one another. In addition, the team assembled three small machines from kits that are used for experimental work.
Adding Up the Next Steps
MakeOne research will continue on a number of fronts, including standards development with ASTM, machine and material locations, logistics, and parts databases. "We'll continue validating methods to test military parts," says Barkley. "We'll also bring in parts from the field to test tensile strength and fracture points."
The team's next major thrust is to see what can be done with open source hardware. Open source hardware is a new design methodology that is based on publishing all information about the hardware implementation, how it can be interfaced to other systems, and how it can be used.
"We have a long way to go, but with more research we hope to put more agility into the acquisition world," says Barkley. "With the right systems engineering, the remaining barriers for adoption can be removed so that out-of-stock parts can be deployed to units in the field well ahead of the current supply chain. It will make it easier for military units to accomplish their missions. For fiscal year 2011, the Operation & Maintenance portion of the DoD's total budget request comprises $283.1 billion. If these costs could be reduced by one-tenth of one percent, that would account for $283 million in savings."