Incorporation of Additive Manufacturing into the United ...



AIR WAR COLLEGEAIR UNIVERSITYIncorporation of Additive Manufacturing Technologies into the United States Air Force Supply ChainbyCraig M. Giles, Lt Col, USAFA Research Report Submitted to the FacultyIn Partial Fulfillment of the Graduation RequirementsAdvisor: Dr. John P. Geis II16 February 2016DisclaimerThe views expressed in this academic research paper are those of the author and do not reflect the official policy or position of the US government, the Department of Defense, or Air University. In accordance with Air Force Instruction 51-303, it is not copyrighted, but is the property of the United States government.BiographyLieutenant Colonel Craig Giles is assigned to the Air War College, Air University, Maxwell AFB, AL. Colonel Giles entered the Air Force in 1997 through the Reserve Officer Training Corps at Iowa State University with a Bachelor of Science degree in Material Engineering. His assignments include multiple flight-line maintenance positions in B-1B, HC-130P, HH-60G and A-10C units and a tour as the Sniper Targeting Pod Program Manager. Additionally, he commanded the NATO AWACS Maintenance Squadron, served as the Deputy Maintenance Management Division Chief at HQ Airborne Early Warning & Control Force, Supreme Headquarters Allied Powers Europe, Belgium, and most recently served as the Deputy Maintenance Group Commander for the Joint Strategic Targeting Attack Radar System at Robins AFB, Georgia. He has deployed in support of Operation Southern Watch, Operation Enduring Freedom, Operation Iraqi Freedom, presidential support, Joint Task Force Katrina and stood-up NATO E-3A operations in Afghanistan. AbstractThe United States Air Force (USAF) requires a robust supply chain to support worldwide operations, requiring the use of strategically-placed warehouses, rapid transportation and expedited repair and manufacturing capabilities to ensure prompt resupply of aircraft parts. Alternatively, additive manufacturing, also known as 3D printing, is an appealing option to manufacture replacement-parts quickly and economically when the part is not available in the supply system or it is not possible to ship the part to the required location in time to accomplish a mission. Additionally, utilizing additive manufacturing techniques at a depot facility could offset diminishing manufacturing source and material shortage issues common with ageing aircraft. The paper analyzes the feasibility of using additive manufacturing technologies to improve the USAF’s supply chain by manufacturing parts at the point of consumption to reduce warehousing and transportation requirements and by producing parts in a depot to offset diminishing manufacturing source and material shortage issues. Analysis of currently available technologies concluded that they are mature enough for some applications at depot-level facilities, but have limited use at more austere, field-level applications. A common constraint across all environments is the lack of certification procedures for additively manufactured replacement parts. The paper provides five recommendations to implement additive manufacturing technologies into the USAF supply chain. Table of Contents TOC \o "1-3" \h \z \u Disclaimer PAGEREF _Toc443320802 \h iiBiography PAGEREF _Toc443320803 \h iiiAbstract PAGEREF _Toc443320804 \h ivTable of Contents PAGEREF _Toc443320805 \h vIntroduction PAGEREF _Toc443320806 \h 1Basics of Additive Manufacturing PAGEREF _Toc443320807 \h 3CAD Model Origin PAGEREF _Toc443320808 \h 4Three-Dimensional Printing PAGEREF _Toc443320809 \h 6Postproduction Finishing PAGEREF _Toc443320810 \h 9Standardization and Certification PAGEREF _Toc443320811 \h 10Future Additive Manufacturing Developments PAGEREF _Toc443320812 \h 12Opportunities for Improvement in the USAF Supply Chain PAGEREF _Toc443320813 \h 13Analysis PAGEREF _Toc443320814 \h 15Production in a Depot with OEM’s CAD Model PAGEREF _Toc443320815 \h 16Production in a Depot with User Generated CAD Model PAGEREF _Toc443320816 \h 17Production in an Austere Location with OEM’s CAD Model PAGEREF _Toc443320817 \h 18Production in an Auster Location with User Generated CAD Model PAGEREF _Toc443320818 \h 18Conclusions and Recommendations PAGEREF _Toc443320819 \h 19Notes PAGEREF _Toc443320820 \h 23Bibliography PAGEREF _Toc443320821 \h 27“Just as nobody could have predicted the impact of the steam engine in 1750--or the printing press in 1450, or the transistor in 1950--it is impossible to foresee the long-term impact of 3D printing. But the technology is coming, and it is likely to disrupt every field it touches. Companies, regulators and entrepreneurs should start thinking about it now.”The EconomistFebruary 10, 2011IntroductionThe United States Air Force (USAF) requires a robust supply chain to support worldwide operations, requiring the use of strategically-placed warehouses, rapid transportation, and expedited repair and manufacturing capabilities to ensure prompt resupply of aircraft parts. In a perfect and modern world, deployed units at the very end of the supply chain would retain a capability to manufacture replacement parts when they need them. However, traditional manufacturing technologies make it infeasible for a deployed unit to maintain a complete machine shop, man it with highly-skilled technicians and stock it with all varieties of raw materials required to manufacture parts at the point of consumption. However, additive manufacturing, also known as 3D printing, may make this a reality.Additive manufacturing is an appealing option to produce replacement-parts quickly and economically when the part is not available in the supply system or it is not possible to ship the part to the required location in time to accomplish a mission. In addition to the advantages of manufacturing a part at the point of consumption, there is value in centralized USAF additive manufacturing capability at one or more of its three existing depot facilities. Production at a depot facility could offset diminishing manufacturing source and material shortages (DMSMS) issues or simply produce the part faster and cheaper than current vendors produce. However, there are technological, standardization and certification concerns the USAF must address before it can broadly employ additive manufacturing to produce spare parts.Advances in additive manufacturing have led to applications in rapid prototyping, industrial, medical, building construction and even food preparation. Narrowing the focus to aviation applications, nearly all of the research focuses on production of new, more complicated parts at lower cost. General Electric expects to field engine components produced by additive manufacturing as early as May 2016. According to GE, the expected advantages include a 25 percent reduced component weight, reducing the number of fuel nozzles from 18 to 1 and five-fold higher durability compared to conventional manufacturing. Additive manufacturing techniques are the only means to achieve these results. However, there is no discussion from GE to use additive manufacturing to produce replacement aircraft parts.In 2013, Lt Cols Bennett and Pettus successfully argued that additive manufacturing could produce a competitive advantage for new aircraft applications as well as for production of replacement parts including the “potential to cut significant time from the reengineering process.” However, they go on to state, “any improvements in the aforementioned processes will need to be accompanied by parallel improvements in bureaucratic support systems that are beyond the scope of this paper.” Part of the bureaucratic support system they are referring to is the standardization and certification of the additive manufacturing process and the parts it produces. This research aims to fill the gap that was outside the scope of previous research efforts.The purpose of this paper is to analyze the feasibility for the USAF to use additive manufacturing technologies to improve its supply chain. The paper starts with a brief overview of the additive manufacturing process, including a summary of current technologies, a description of standardization and certification efforts and a discussion of future technology advances. Then it highlights opportunities in the current supply chain where additive manufacturing may benefit the USAF. To organize the analysis, the paper introduces a four-quadrant model to examine the relationship between the origin of the design specifications and the environment where technicians manufacture the part. It concludes that currently available technologies are mature enough for some applications at depot-level facilities, but have limited use at more austere, field-level applications. Additionally, a common constraint across all environments is the lack of certification procedures for additively manufactured replacement parts. Finally, the paper provides five recommendations to implement additive manufacturing technologies into the USAF supply chain. This research includes two limitations. First, it only addresses replacement parts, not the development of new, more complex parts made possible by additive manufacturing. Second, additive manufacturing techniques can produce parts from a variety of materials, but the focus of this research is only on additive manufacturing of metal parts that show potential for use in the aerospace industry; mainly aluminum, titanium and steel. Basics of Additive ManufacturingAdditive manufacturing is a subset of the broader category of Direct Digital Manufacturing (DDM) where automated machines manufacture a part from computer-based drawings known as Computer-Aided Design (CAD)/Computer-Aided Manufacturing (CAM). Additive manufacturing builds an object layer-by-layer from raw material as opposed to traditional subtractive manufacturing where a mill, lathe or other machine removes material to obtain the final shape. This research describes the additive manufacturing process with the following three steps. The first is generation of a digital CAD model. Designers can use data from the original equipment manufacturer (OEM) or use 3D scanning techniques to reverse engineer an existing object to develop the CAD model. The second step is to print the replacement part. There are many different methods to print an object, each with their own advantages and disadvantages. The final step is postproduction finishing. This can include heat treatment to control grain size, subtractive manufacturing to meet tolerance requirements and/or sanding and polishing to achieve the required surface finish. CAD Model OriginA common source to build a CAD model is from the OEM’s design specifications. In addition to the dimensions, the original design specification includes material properties and acceptable tolerances for the finished part. However, for some parts, the USAF does not have access to the OEM’s specifications due to either contract restrictions where the USAF did not purchase rights to the data, or in DMSMS cases where the OEM is no longer in business. In cases where the OEM’s specifications are not available, reverse engineering a CAD model from an existing part is a possible solution. Reverse engineering a CAD model from an existing part requires a thorough understanding of the functionality of the original part and its intended operating environment. Even the best reverse-engineering process can only determine the dimension of an existing part, not the design tolerances included in the OEM’s specification. Without knowing the design tolerances there is a risk that the sum of the errors accumulated during the original manufacturing, CAD model development and additive manufacturing can exceed the OEM’s designed tolerance and lead to the part’s potentially catastrophic failure. Additionally, if the modeled part experienced wear, deformation or cracking during use, the reverse-engineering process will include the defect in the CAD model and replicate it in the production version. Engineers can account for the presence of a known defect in the model part, but they require extensive design knowledge to avoid introducing unintentional design flaws into the CAD model. There are five common commercially available reverse-engineering technologies. Coordinate Measuring Machines. A coordinate-measuring machine (CMM) uses either physical probe or a laser to produce a “point cloud” of key points on a model part. The point cloud is not a complete CAD model, but for simple parts, CAD software can fill in the dead space between the measured points to produce a CAD model. A CMM can quickly produce a point cloud for simple parts, but complex parts require additional point measurements and can take longer to model. Fully automated CMMs are commercially available, however, they excel at quickly verifying the tolerance new parts from the manufacturing process, not developing CAD models of various shapes and sizes. Furthermore, CMMs cannot measure any internal features or small detailed sections that are not accessible by the probe or in the line of sight from the laser. A recent U.S. Patent combining CMM and ultrasound may lead to a CMM being able to produce a CAD model including internal features, but the technology is not commercially available. 3D Scanners. As opposed to a CMM that only measures one point at a time, a 3D scanner shines a light across the surface of a model part and uses a camera or charged-couple device to record the image as a point cloud. By scanning multiple directions, a 3D scanner captures all visible external features in the point cloud and CAD software converts the point cloud to a CAD model. Three-dimensional scanners are portable and mostly automated, therefore the quality of the scan is not dependent upon the technician’s training and ability. Similar to a CMM, 3D scanners do not detect internal structures or details hidden from the light and camera.Laser Scanning. Instead of using light and a camera like a 3D scanner, a laser scanner reflects a laser off the model part and uses range finding and triangulation to develop a point cloud of the part. Laser scanners are portable and produce high-quality point clouds. However, similar to 3D scanner and CMMs, a laser scanner is not able to detect internal structures. Computer Tomography (CT) X-ray Scanning. A CT X-ray scanner records a series of “slices” and assembles each layer into a CAD model without the additional step of generating a point cloud. The 3D models generated by a CT scan include internal structural details in addition to the external dimension, although the part's thickness and material density can influence the accuracy. CT X-ray scanners are portable and do not require extensive training to operate.Rotating CT X-ray Scanning. A rotating CT X-ray scanner builds a CAD model of a part by recording individual slices recorded while the part rotates on its third axis. The process takes longer than routine CT X-ray scanning and the equipment is larger and not portable, but the rotating CT X-ray scanning produces the highest quality CAD model of a part including internal structures. Three-Dimensional PrintingThe second step of the additive manufacturing process is to print a part using deposition-based additive manufacturing procedures. All metal deposition-based additive manufacturing technologies share the following challenges. First, the quality of the final product is highly dependent upon the quality of the feedstock used to produce the part. The 2013 Measurement Science Roadmap for Metal-Based Additive Manufacturing highlighted the industry’s need for improved availability of reliable feedstock and the need for a greater understanding and characterization of feedstock materials. Second, deposition-based additive manufacturing suffers from a lack of standards regulating the printing process, material properties, defects, geometrical parameters and test procedures. The Measurement Science Roadmap identified milestones for the additive manufacturing industry to achieve standardized procedures with a target of producing first time, quality aerospace metal additive manufactured parts. The following section describes some advantages and limitations of three specific deposition-based additive manufacturing technologies.Direct Metal Deposition. Direct metal deposition (DMD) uses a laser to melt metal powder delivered through a coaxial nozzle and can produce medium-sized parts (greater than 12”x 12”x 12”). However, the equipment, shown in figure 1, is large and the product requires secondary subtractive machining. Figure 1: Commercially Available Direct Metal Deposition Machine.Direct Metal Laser Sintering. Similar to DMD, direct metal laser sintering (DMLS) uses a laser beam as the heat source to melt metal powder. The main differences are DMLS uses a powder bed versus DMD’s coaxial nozzle and DMLS requires an inert gas environment. Commercially available DMLS machines, as shown in figure 2, are smaller than DMD machines but are not portable. DMLS is limited to small (12”x12”x12”) parts that require nothing more than postproduction surface polishing and heat treatment to control the material’s microstructure.Figure 2: Commercially Available Direct Metal Laser Sintering Machine.Electron-Beam Melting. Electron-beam melting (EBM) is similar to DMLS with the main difference being EBM uses an electron beam in a vacuum to melt the powder. The process produces parts with an isotropic grain structure negating the need for post-production heat treatment. However, EBM produces a rough surface finish requiring postproduction polishing or machining. Like DMLS machines, commercially available EBM machines are smaller than DMD machines, see figure 3, but are not portable. Figure 3: Commercially Available Electron-Beam Melting Machine.Postproduction FinishingThe final step in the additive manufacturing process is postproduction finishing. All of the parts produced with DMD, DMLS and EBM require subtractive manufacturing, polishing, and/or heat-treatment. USAF machine shops retain the capability to perform the postproduction finishing at all fixed bases with the exception of the most austere locations where access to subtractive machining and heat-treatment equipment could be limited. A more pressing concern is the insufficient understanding of the required postproduction processing in the additive manufacturing industry. The industry’s limited understanding of thermal post-processing behavior and the lack of characterization of hot-isostatic pressing, heat treatment and welding all need further research to continue advances in additive manufacturing. Standardization and Certification Although additive manufacturing registered a 34.9 percent compounded annual growth in 2014, a hurdle preventing its widespread acceptance in critical applications, such as aerospace, is the lack of international standards for certification. Unlike traditional subtractive manufacturing, very small deviations in additive manufacturing’s build process, environmental conditions, or even vibrations during printing, can cause variations in the physical properties and dimensions of parts produced with the same additive manufacturing technique. The metal deposition additive manufacturing process must control for the quality of the metallurgical bond between layers as well as controlling the metal’s microstructure, including grains and grain boundaries. Complicating this search for standards, private companies fund a significant amount of additive manufacturing research and the advances in techniques they develop remain proprietary.In an attempt to standardize the additive manufacturing industry, the International Standards Organization (ISO) established a formal agreement with the American Society for Testing and Materials (ASTM) in 2011 for joint development of additive manufacturing standards. As of November, 2015, ASTM has published 11 standards, including three jointly issued with ISO covering additive manufacturing file format, a practice for reporting data for test specimens produced via additive manufacturing, and a guide for characterizing the properties of metal powders used in additive manufacturing. An additional 10 standards are in work including guides and test method to improve the quality and consistency of the final product.Despite the agreement to development joint standards, there are significant obstacles to overcome. The additive manufacturing field is still a young, rapidly developing field and any standards need to allow room for innovation. Additionally, the standardization efforts from ISO and ASTM are strictly voluntary with no projection to regulate the industry anytime soon. The Federal Aviation Administration (FAA) has taken the lead to ensure safe operation of additive manufactured parts in the U.S. civilian airline industry. The FAA formed the Additive Manufacturing National Team (AMNT) in 2014 that teamed their specialists and engineers from several functional areas with experts from NASA, DoD, Massachusetts Institute of Technology and Wichita State University. The goal of AMNT is to assess the applicability of current regulations to additive manufactured products and to initiate the development of guidance allowing flight certification for these products. Boeing received FAA certification to use 3D printed parts for certain engine applications in 2015. However, Mr. Jim Kabbara, an aerospace engineer with the FAA’s Aircraft Certification Office says, “There are many great bene?ts [to additive manufacturing], but also some huge risks … there are at least 50 variables with this technology, maybe more, that we need to understand better.” While it appears most of the industry’s attention is on certifying additively manufactured parts specifically designed and tested as a new end item, the FAA recognizes the potential benefits and challenges of additively manufacturing replacement parts. Mr. Mark James, an engineer with the FAA’s Small Airplane Directorate says, “in [general aviation] especially, parts are hard to find for airplanes orphaned by companies that have gone out of business.” He goes on to state, “parts on demand ... could save time and money ... assuming of course that compliance to the type design can be shown.” The USAF made headlines in January 2016 for approving the first additively manufactured replacement part on an E-3 aircraft. Technicians reverse engineered a plastic armrest cap, shown in figure 4, with “calipers and other measuring tools” and printed it in 10 minutes for an estimated cost of $2.50. Annual cost saving for this part alone could reach $1,000. Although the part is not critical to the aircraft’s airworthiness, engineers still had to certify it to existing fire and noxious fume standards.Figure 4: SSgt Ryan McBride Displaying an Additively Manufactured Armrest CapFuture Additive Manufacturing DevelopmentsAdditive manufacturing is growing quickly, and advances in technologies and equipment will affect its application within the USAF supply chain. Aircraft manufacturers are developing new weapons systems with additive manufactured parts installed during initial assembly. Lockheed Martin included a dozen 3D-printed brackets on Juno, a satellite launched in 2011, and is considering building some small titanium components in the wings and tails of the F-35 with additive manufacturing. Boeing has used additive manufacturing on its satellite systems and produced polymer-based air ducts for the F/A-18 Super Hornet. As companies include more additive manufactured parts on their aircraft, the ability to produce a replacement part via additive manufacturing becomes more feasible if the USAF has access to the OEM’s specification and manufacturing procedures.Advancements in additive manufacturing can improve the quality of the final product and may reduce the need for postproduction processing. Research on the incorporation of nanotechnologies into the additive manufacturing process has demonstrated promising results by improving mechanical properties, lowering sintering temperatures and improving dimensional accuracy. If additive manufacturing advances to being able to control the grain or atomic structure, the quality and accuracy of the final product could meet or exceed design tolerances without the need for any postproduction finishing. Opportunities for Improvement in the USAF Supply Chain The USAF supply chain combines three of the seven core logistics functions identified in Joint Publication (JP) 4-0: supply, distribution and maintenance. The supply function is responsible to manage supplies, inventory and global suppliers. The distribution function oversees and collaborates with other logistics providers to move material through the distribution pipeline from sourcing to the end user. Finally, the maintenance function provides depot and field level maintenance on end items and components. Injection of additive manufacturing into the USAF supply chain can provide significant benefits in each of these three logistics core functions and ultimately provide more effective and efficient supply chain operations.The USAF follows Department of Defense (DoD) guidance to assign a Source, Maintenance, and Recoverability (SMR) code for all aircraft parts. SMR codes can be either “consumable”, “field-level reparable” or “depot-level repairable” and are assigned to provide the most economical support through the life of the item. Depot-level maintenance is the most complex and extensive level of maintenance in the DoD and includes the ability to manufacture a variety of replacement parts. Field-level maintenance is less complex and only manufactures simple panels, brackets, hydraulic tubes, wire harnesses, etc. that require less complex tools, equipment and skills to manufacture. Developing an additive manufacturing capability at the field level could allow technicians to economically produce a wider range of parts, eliminating the need for extensive warehousing and transportation.Currently, the USAF supply chain supports forward deployed units with Readiness Spares Packages (RSPs). An RSP is a set of commonly used parts stored at the point of consumption intended to provide the end user access to mission-critical parts. The supply system’s goal is to establish premium transportation routes for aircraft parts from the point of use to the repair node and returned to the point of use to achieve a consistent resupply within 72 hours of deployment. To provide consistent resupply, the USAF fills the repair cycle with serviceable parts while moving the unserviceable parts to the source of repair or reclamation. The author’s previous research found aircraft averaged over 9 days in transportation from a CONUS source of supply to a deployed location and over 26 days in the retrograde leg from the source of consumption to a CONUS source of repair. Forward-deployed additive manufacturing capabilities could eliminate the need to transport some parts to and from deployed locations resulting in lower inventories and compressing the overall repair cycle from weeks to just hours.Diminishing manufacturing sources and material shortages (DMSMS) is the loss of manufacturers or suppliers of a part. DMSMS occurs when manufacturers discontinue production and is a common occurrence on aging aircraft. One of 10 DMSMS resolutions included in the DoD’s DMSMS Guidebook is to develop a new source for production by either reverse engineering the part or using the OEM’s specifications. Historically, this a relatively expensive option due to the cost associated with nonrecurring engineering and development-related activities to reverse-engineer the part or the cost associated with purchasing the OEM’s specifications. Applying additive manufacturing techniques, including CAD model reverse engineering at the depot level, could provide the USAF a tool to economically combat DMSMS in its aging aircraft fleet. AnalysisTo analyze the feasibility of using additive manufacturing to improve the USAF’s supply chain this paper plots the three steps of modeling, printing and post-production finishing in a strategic planning space defined by two independent variables. The first variable is the origin of the digital CAD model. A CAD model provided by the OEM replicates the specifications of the original part. Technicians can also develop a CAD model by using a 3D scanner to replicate an existing part, but this process has risk of inducing a small amount of error. The second variable is the environment required to conduct the printing and post-production finishing. The environment can range from a robust production capability at a depot, where quality control may be more precise, with access to all additive manufacturing techniques, specially trained technicians and advance engineering design knowledge, to austere conditions with minimal equipment, generalized training and no engineering design knowledge, where there is greater risk for error.This paper uses the quad-chart in figure 5 to examine the relationship between these two variables. The horizontal-axis represents the origin of the CAD model and the vertical-axis represents the production environment. The four quadrants describe the relationship between the variables. Figure 5: Categorization of CAD Model Origin and Production Environment. Quadrant I captures scenarios where the production is accomplished at a depot facility utilizing the OEM’s CAD model, quadrant II represents depot production with a user generated CAD model, quadrant III shows austere production facility with OEM generated CAD model and quadrant IV represents austere production facility with user generated CAD model.Production in a Depot with OEM’s CAD ModelWith respect to the quality of the part produced, quadrant I is the lowest risk. Production in this quadrant utilizes the OEM’s specifications meaning there is no risk of propagating errors during reverse engineering and the design tolerance of the part is a constant. Since the depot accomplishes the work, portability of the printing capability is not an issue allowing the depot to utilize any or all of the additive manufacturing techniques. Additionally, postproduction finishing is not is not an issue since the depot maintains a large machine shop and heat treatment capability. Current technology maturity makes additive manufacturing at the depot with the OEM’s CAD model possible now, but full utilization requires standardization and certification processes that currently do not exist. The only benefit in the scenario is when the depot facility can manufacture parts faster and cheaper compared to commercial vendors.Production in a Depot with User Generated CAD ModelQuadrant II in the upper left of figure 5 shares the same advantages as quadrant I with respect to the depot manufacturing process. However, the depot needs to produce the CAD model for production. Since the depot does not have a shortage of space and power, and portability is not an issue, they can employ any of the reverse-engineering technologies including the rotating CT X-ray scanner that produces the highest quality CAD model and is able to capture internal structures. In addition, the depot has access to engineers with in-depth design knowledge to assist with correcting or verify the quality of the organically generated CAD model. Current technology maturity makes additive manufacturing at the depot with user-generated CAD models possible now at relatively low risk. The generation of CAD models via reverse engineering requires additional work and in-depth design knowledge, but once an engineer approves a CAD model in an ISO/ASTM CAD file standard, the file can be stored and distributed to additive manufacturing facilities anywhere to avoid future nonrecurring engineering costs. Additively manufacturing a part without the OEM’s CAD model is particularly beneficial to the USAF when replicating DMSMS parts. The lack of an existing standardization and certification processes is the largest challenge for reverse engineering and manufacturing parts in this quadrant of figure 5.Production in an Austere Location with OEM’s CAD ModelQuadrant III in the lower right of Figure 5 describes production of the part at an austere location using the OEM’s CAD model. Similar to quadrant I, there is no risk of propagating errors during reverse engineering and the design tolerance is a constant. However, since the production takes place at an austere environment, the additive manufacturing equipment must be ruggedized and portable. Additionally, the amount and type of postproduction finishing may require equipment not available at all austere locations such as mills, lathes and annealing ovens. Additive manufacturing at an austere location utilizing the OEM’s CAD model is useful at deployed environments to prevent extended downtime awaiting receipt of replacement parts. Additionally, since the USAF produces the part at the point of consumption, the supply chain does not need to warehouse as many parts and does not require transportation for the part. The lack of an existing standardization and certification processes is the largest challenge for manufacturing parts in this quadrant of figure 5.Production in an Auster Location with User Generated CAD Model Quadrant IV represents the most difficult scenario to perform additive manufacturing combining a user generated CAD model with production in an austere environment. In this case, both the scanner and the printer need to be portable and ruggedized while the product should require a minimal post-production finishing. In addition, generating the CAD model at an austere environment limits accessibility to engineers with design knowledge to adjust the CAD model for latent defects in the modeled part. In addition to reducing warehousing, transportation and extended downtime, additive manufacturing in this quadrant could yield significant benefits for recovering damaged aircraft at remote airbases and aircraft battle damage repair (ABDR), but there are significant challenges to overcome. Typically, the focus of an aircraft recovery team or ABDR team is to make the aircraft airworthy for a one-time flight to an established maintenance complex for permanent repair. In these circumstances, there may be an application for a portable reverse engineering and additive manufacturing capability to manufacture a part without the OEM’s drawings at an austere location. Limiting the application of additive manufacturing in this environment is the non-availability of ruggedized and portable equipment and lack of standardization and certification processes.Conclusions and RecommendationsThis research began highly optimistic that additive manufacturing would prove feasible for implementation into all levels of the USAF supply chain. With current technology, however, limitations emerged. While the technologies are mature enough for some depot-level applications, they have limited use at more austere, field-level applications. A common challenge in all environments is the lack of standardization and certification processes for reverse engineering and additive manufacturing. Figure 6 summarizes the benefits, challenges and technical maturity associated with each of the four situations this paper analyzed. Figure 6: Summary of ResultsIn order to address the challenges identified in Figure 6 associated with additive manufacturing this paper provides the following five recommendations. The USAF should:Work with the FAA’s Additive Manufacturing National Team to expand its scope to develop a standardization and certification framework designed specifically for reverse engineering and additive manufacturing replacement parts.Publish standards and technical orders to regulate the additive manufacturing process across the USAF that mirror the ISO/ASTM standards. Establish a robust 3D scanning and additive manufacturing capability at one of its aircraft depots and use the capability to produce DMSMS parts.Require all future acquisition programs to include ISO/ASTM standard CAD files for all parts originally produced with additive manufacturing.Collaborate with additive manufacturing equipment vendors to produce a ruggedized metal-deposition additive manufacturing machine that is able to fit onto a 461L pallet and operate in an austere environment.Continuing advancements in additive manufacturing technology may lead to widespread utilization in aerospace applications, including production of replacement parts. Incorporation of nanotechnologies could eventually allow additive manufacturing processes to meet or exceed traditional manufacturing tolerances. However, further research is required to understand the mechanical and material properties of additively manufactured replacement parts before use in critical aircraft structures. In the interim, the USAF can benefit from additive manufacturing in certain settings. The greatest near-term benefit is to manufacture replacement parts at a depot facility to alleviate DMSMS issues or in cases where the depot can manufacture parts faster and cheaper compared to commercial vendors. At the field level, if the USAF has access to OEM CAD models, additive manufacturing may be possible in limited cases using available technologies at non-austere bases. As additive manufacturing technologies and certifications mature, additive manufacturing has a potential to provide significant benefit to the USAF’s supply chain in the future. Additionally, there are opportunities for further additive manufacturing research that could benefit the DoD, including applications on aircraft carriers as well as non-aviation uses across the services, which were outside the scope of this paper.NotesBibliographyAir Force Instruction (AFI) 23-101. 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