Large Part Additive Manufacturing Using Direct Metal Deposition (DMD)

Additive Manufacturing (AM) is emerging as a mainstream manufacturing technology, and demand for large part manufacturing is getting stronger. Direct Metal Deposition (DMD) is a DED technology based on laser and powder metal application using a closed-loop-feedback control system. This presentation will give an overview of the DMD technology highlighting its capability to scale up to large size parts. The focus will be DM3D’s new multi-nozzle DMD technology capable of printing parts up to 10ft in diameter, 10ft in height and 5000 lbs. in weight. The multi-nozzle DMD technology doubles the part throughput with a further possibility of quadrupling it. Other challenges such as residual stress and distortion related to large scale AM will be discussed in detail. Simulation approaches to mitigate such challenges will be demonstrated through example parts. Finally, a case study involving 3D printing of a very large size real-world part, namely NASA’s RS 25 engine nozzle will be discussed. Benefits and risks of 3D printing such parts that are more than 9ft in height and weighs more than 3500Lbs will be highlighted.

Cost per part is the largest issue gating the adoption of Metal AM for serial production. Quality material can only be welded so fast before the properties start to drop off. Factors such as machine build volume, number of lasers, powder layer thickness, and part orientation can play a significant role in reducing the price of building a part. Optimizing the current generation of machines to produce material faster is one of the biggest industry drivers today. Metal AM gets faster every year, applications that used to not make sense may now be reaching a cost break point where additive could now be considered. If Metal AM is to be taken seriously as an alternate form of manufacturing not just complex geometry but simpler parts for supply chain reduction the cost per part needs to be significantly lower. We will address these topics and share practical considerations to optimize machine productivity and reduce production costs.

The use of additively manufactured high temperature components offer many benefits including cost reduction, better performance and lower risk, however, the parts created using these processes are often left with trapped or partially processed powder and, rough surfaces, heat scale and other imperfections which cause difficulty in FPI and Blue light inspection.

Chemical milling and surface post-processing for high temperature additively manufactured, 3D printed metal parts is available today on a wide variety of alloys including all printed titanium alloys, aluminum alloys (including A205) and high temperature corrosion resistant alloys (Inconel 625, Inconel 718, Haynes 188, and cobalt chrome).

Chemical post-processing improves the surface finish of parts and provides a methodology to enable product realization and meet design specifications. The finishing process can enhance a part’s surface characteristics, geometric accuracy, aesthetics, mechanical properties, and facilitate FPI and blue light inspection. Some typical applications for chemical surface treatment operations are:

• Significant improvement of fatigue performance
• Removal of unwanted surface crystalline morphologies
• Surface preparation for dye penetrants or other inspection processes
• External and Internal support structure removal

This process has been successfully used to provide a method to remove partially sintered or loose powder particles on internal and external surfaces, decrease overall surface roughness of the printed component with an average of 60-70% reduction between incoming and post processed parts, and reduces scale or oxidation layers to promote FPI interpretability.

Metal Additive Manufacturing processes such as Directed Energy Deposition (DED) can produce complex geometries with incredible benefits for applications, but there are challenges between concept design and producing a part. To create quality, repeatable parts, in-process monitoring can be utilized to both collect data and control the build process. The data collected can help determine the point of failure initiation, and with implemented control in place, self-correction is possible during the build process. With Directed Energy Deposition, various monitoring and control modes are available to reduce parameter development times, improve build quality, and limit operator input during a build. Among these control modes are melt pool size and temperature, powder flow, laser power, and geometric monitoring and control. These control modes not only significantly reduce the process parameter development cycle, but also result in a higher quality build to include density and material properties.

The FLCS Canopy Practice Aid is a hybrid training asset with an additively manufactured frame that supports a scrapped transparency. This practice aid replicates the conditions on the jet and allows the maintainers to practice before approaching the aircraft. The 3D printed frame is printed into 10 separate sections using Ultem 9085 material. The practice aid can be quickly assembled and fits onto the standard mil-spec canopy cart. The 10 sections of the practice aid can be printed in 1 month utilizing only one Fortus 900 machine which was one tenth of the time quoted for a standard steel frame. This additively manufactured frame can be paired with scrap transparencies to create the necessary practice aid for the units.

Today we have created a working prototype of the Canopy Practice Aid and are in the evaluation phase. The prototype has been deployed to Luke Air Force Base Egress Shop for testing and evaluation of time savings and reduction in rework. Upon completion of this trial period, we will receive recommendations and feedback from air force maintainers on design improvements.

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Additive Manufacturing, known colloquially as 3D Printing, is now an established method of manufacturing, is real and not a gimmick. We are currently in a new space race, which is being led by commercial tech start-ups. These companies are small, nimble-acting and forward-thinking, refuse to do things the old way and embrace the new. For these companies and more, Additive Manufacturing is the key to unlocking access to space. As we seek to push the boundaries of human space flight, the challenge for space launch providers and the associated supply chain, is to provide greater access to space by improving products, deploying new materials, simplifying designs, decreasing part count, reducing errors and driving smarter and leaner operations. Additive Manufacturing is also an enabling technology for automation, machine learning and AI. From combustion devices for rocket engine propulsion to wire arc additive manufacturing of domes, barrels and fuel tanks, the technology is providing real solutions to space exploration problems. 3D Printing in microgravity and off-planet is another aspect of Additive Manufacturing which is making science fiction become science fact. As we recommence exploring our solar system, Additive Manufacturing is the key to unlocking access to space.

Topology Optimization and Generative Design have received a great deal of press about their ability to greatly reduce the weight of components without sacrificing performance. To date, however, there are few examples where such designs have been implemented, primarily because of the difficulty and cost of manufacturing optimized components in production.

This case study covers a foundry owner’s effort to use topology optimization to redesign an investment cast instrument housing. His customer informed him that the aircraft component that he had been casting for several years was a candidate for light-weighting and that he would likely lose the order. He decided to be proactive and look for an alternative casting design that would not only meet the weight reduction goals of the manufacturer but would result in fuel savings greater than the increased cost of manufacture. Although it presented significant manufacturing challenges, the resulting design not only exceeded the weight reduction objectives of the customer, but the expected fuel savings far exceeded the increased cost of manufacture.

Under the Radar Affordability program sponsored by OSD, ACI worked on a prototype design and development of a broadband passive limiter circuit test coupon, which compares the performance of gold wire bonds against 3-D, printed additively manufactured silver conductors. The Optomec Aerosol Jet printer (AJ300) was utilized in developing a relatively new process which can achieve fine pitch and high-resolution printing of Nano-materials. The Aerosol Jet is a non-contact, mask-less printing process for printing fine pitch structures with the capability to process various inks (Conducting and non-conducting) containing Nano-particles. This presentation will show the selection procedure which includes validation of the equipment, processes, materials, and dielectric support structures necessary for printing conductive RF connections in high reliability military circuitry. Additionally, the test results between the performances of traditional wire bonding (15 samples) verses additively manufactured printed RF conductors (15 samples) will be demonstrated over a wide range of frequencies. The presentation will also cover the challenges for Additive Manufacturing (AM) which includes bridging the air gap between substrate and die, and the sintering process required to produce the conductive traces needed to achieve electrical equivalence to wire bonding.