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This article provides an overview of the differences between additive and subtractive manufacturing, 3D printing technologies, 3D printing applications for aerospace and defense parts, and a look at how Primus utilizes titanium printing to support customers.
What is the difference between additive and subtractive manufacturing techniques?
Additive manufacturing, also known as 3D printing, is the process of creating an object, such as a critical satellite component, using material deposition and numerous post processing techniques. This is different than traditional subtractive manufacturing in one main way. Instead of taking a block of raw material and using lathes, mills, and CNC machines to remove material in a controlled manner, material is selectively added to a blank slate to build a component from the ground up. Subtractive manufacturing typically
uses cutting tools such as end mills, boring bars, or drill bits to remove matter from a block, bar, or slug of raw material. The tool (or the material if the machine in question is a lathe) is spun at a rapid rate and is ran through the material at computer programmed locations where stock needs to be removed. Through 3 and 5 axis machining, the work can be spun along various axes to remove material to form complex shapes. One alternative to subtractive manufacturing is 3D printing.
This seemingly new technology can be traced back to 1925. A patent was issued for the use of arc welding techniques to create sculptures and decorative articles by depositing welded beads of metal on top of one another to form baskets and other household items. 3D printing first found its use in manufacturing in 1982 when United Technologies Research Center filed a patent for a “Method for Fabricating Articles be Sequential Layer Deposition.” Initially, Additive Manufacturing was only used for rapid prototyping to develop a model for parts to be later created using subtractive methods. It wasn’t until the 2000’s that Additive Manufacturing began to achieved production-grade parts primarily for the medical implant industry. Since then, additive manufacturing has crossed over to the Aerospace and Defense supply chain for making high precision, low volume parts and components.
What are the key types of additive manufacturing / 3D printing?
- Stereolithography – This method utilizes liquid plastic to create 3D objects through layer-by-layer deposition. Liquid resign is collected in a vat with a clear bottom. UV light is used to trace a pattern in the vat and selectively cure the resin. The object is dragged up by a platform to allow the part to grow from the base down . This type of 3D printing is primarily used for rapid prototyping as it is too slow to produce plastic parts in a cost-effective manner.
- Fused Deposition Modeling – Fused Deposition Modeling feeds a thermoplastic filament into an extruder. This plastic is then deposited onto a plate to build a part layer-by-layer from the ground up. This is the most common type of 3D printing and is often seen in entry level printers. This method is also used for rapid prototyping and can be used along with Stereolithography to create negative molds for metal casting.
- Sheet Lamination– Sheet Lamination utilizes a cutting device (usually a laser) to slice through thin layers of material. These cuts are then deposited layer-by-layer and glued together to form parts. This strategy can be used with plastics, wood, and even metal to create prototypes and production level parts.
- Powder Bed Fusion– This strategy employs a laser or electron beam to weld or sinter layers of powdered metal together to from a part. Powder bed fusion is commonly employed by the Aerospace, Defense, and medical industries to create intricate, low volume production parts. The printer used by Primus Aerospace falls under this category.
What types of aerospace projects are best performed on a 3D printer?
- Prototype parts – Producing 3D printed parts requires very little setup, additional tooling or fixtures to create working parts for prototype or R&D applications. This allows design modifications to be verified with minimal effort. Engineers may 3D print a part for a prototype but later transition to precision machined parts as the program enters production phase.
- Complex designs – 3D printing allows designers to create parts that could not be produced with traditional subtractive manufacturing techniques. While aerospace parts designers should not throw out the book on design for manufacturability (DFC), some applications do require designs that cannot be accomplished on a 5-axis CNC mill (such as integrated internal pathways and complex internal features).
- Lightweight requirements – Additive manufacturing allows the incorporation of weight saving features and innovative designs that cannot be traditionally machined, such as complex lattice structures and intricate hollow structures. For example, aerospace engineers designing parts for a commercial satellite (where weight represents a high-payoff Value Engineering effort) can shed costly weight without sacrificing strength.
- Low production volumes – One drawback of 3D printing is its part production time. For a powder bed fusion system, builds take at least one day to print causing this technology to not be applicable for high production parts (yet).…
Additive Manufacturing at Primus Aerospace
Primus primarily uses a Velo3D Sapphire Metal AM Printer for additive manufacturing aerospace projects. This machine is tailored to use powder bed fusion technologies to 3D Print space and satellite parts using a Ti 6Al-4V titanium alloy powder..
ThisThe Velo3D Titanium Printer works by using a vacuum powered contactless recoater to deposit titanium powder over a build plate. The recoater dumps material over the plate, and then uses a vacuum to suck up any access metal an
d ensure a consistent layer of powder. Two separate lasers sinter fuse the powder together in a predetermined pattern to methodically form a part from the base up. Fusion is the process of melting a two separate solid components and re-solidifying them together. This is done in layers that are slightly offset from one another to avoid empty space in the finished product. This ensures strength and reliability in precision aerospace parts. This is done on top of a build plate that sits on top of a piston, which lowers the plate to accommodate for each subsequent layer of titanium until the build is complete. The lasers and piston take instructions from Velo’s Flow software. This takes a CAD model of a part, slices it, and creates step by step instructions for the 3D printer to follow.
This machine has the capability to print material at low angles, parts with overhanging features, as well as internal passageways and cavities with little to no support structures. In turn, this decreases the need for post processing and allows primus to manufacture an extremely wide range of components. So far, we have used this machine to create one-piece parts with a high level of complexity, components with internal cooling passages, and thin-walled pressure vessels with an almost unattainable degree of precision.
Primus Aerospace supports aerospace, defense, and space manufacturers with build to print 3D printed titanium parts. Primus is able to combine this innovative 3D printing technology with other valued added services (such as finishing, grinding, or painting) and an aerospace AS9100 certified quality management system.
 3D Printing | An Overview of 3D Printing Technologies (techpats.com)
 3D Printed Lattice Structures and Generative Design • OpenFab PDX
 Velo3D launches its first metal Additive Manufacturing system (metal-am.com)
Images courtesy of Velo3D
My name is Josh Trujillo and I am a rising senior in the Colorado School of Mines Mechanical Engineering Department. I recently completed an internship with Primus Aerospace’s Paradigm Division as a Process Engineer.
My story with Primus Aerospace started when Gary Vallencourt, the Vice President of Primus Aerospace Paradigm Division, was bitten by a rattlesnake while paragliding. My stepmom, who owns Tonic Trails – a massage therapy and holistic medicine practice in Golden, Colorado, treated his swelling on short notice. Following the treatment, she got me in touch with Gary, helped me secure an engineering internship for summer 2021. That rattle snake unknowingly gave me a huge opportunity that I was not about to let slip through my fingers.
I was initially drawn to the field of mechanical engineering from my love of solving mechanical problems. I grew up riding mountain bikes and wanted to better understand what went into making such a complex system so I could fix my bike more effectively. My high school physics class further reinforced my desire to become a mechanical engineer as I found the study of motion extremely interesting (and I seem to have natural ability in the field). Since childhood, I’ve had a nascent interest in aerospace, but seeing a SpaceX Falcon 9 rocket launch from Kennedy Space Center inspired me to chase my dream.
Going into the summer, I was excited to gain hands-on experience as a process engineer. I also had no idea what exactly my job was going to entail. In my head, I would either be making meaningful contributions to the company or getting Narate, my boss, coffee all summer. On my first day, I quickly realized that even though I was qualified to work there, I had a lot to learn. I expected to jump right in and be on par with the other engineers because I had extensive experience with CAD (Computer Automated Design) and was machine shop certified through the Colorado School of Mines.
In reality, I was quite novice at most of my daily tasks, when compared to Narate, a professional process engineer, and the machinists. Most of these skilled workers had spent at least 10 years mastering CNC programming, set up, and operation. I was playing well above my weight class, but I would not let this discourage me. To learn the nuances of advanced aerospace manufacturing, I shadowed Narate for my first week. He gave me simple tasks at first, like renaming files, running a gas line, and ordering and installing a gas regulator for Primus’s new Velo3D Sapphire titanium 3D printer.
I then moved on to deburring intake manifolds for an in-use rocket engine, which would be used on an upcoming space mission. Deburring machined parts is an important, yet tedious task, that removes small nicks and imperfections from a completed part. As I demonstrated my ability to read engineering plans and complete final finishing tasks, I earned the team’s trust to move on to higher level tasks. This let me begin setting up and operating CNC machines, learning basic CAM (Computer Automated Machining), and modifying CAD designed parts for 3D printing.
Here is a short list of a few things I accomplished during this stage of my internship:
- Designed and CNC machined a bracket to mount the argon regulator I previously ordered to the wall of the shop.
- Operated a 5-axis CNC machine to create ballasts for a satellite.
- Made modifications to parts to allow them to be printed in a metal powder bed fusion 3D printer.
- Performed basic set-up and calibration for the 3D printer.
- Basic CNC set up and operation for facing operations in support of the 3D printer.
- Modified, sliced, and printed several components for a mid-air airplane refueling station.
- Designed and 3D printed a custom bottle opener.
- Designed several fixtures for testing and manufacturing of various components.
Before I knew it, I was performing the daily operations of a process engineer by planning the top-to-bottom production of several space satellite components and aerospace 3D printed parts. This was not only a great experience, but also extremely rewarding – considering my skill set at the beginning of the summer. This progression would not have been possible without the guidance of my summer mentor, Narate. He greatly improved my design, engineering, CAD, and machining skills throughout the summer. Andy, the lead machinist, and the rest of the machinists in the shop also helped me a lot when it came to CNC operation and machining. These guys are all extremely skilled and I learned a great deal just by watching them work. John and Antonio, Primus’s quality inspectors, showed me some of the measuring and quality inspection techniques that allow machinists to feel confident in their machined aerospace parts. I felt as if everyone at Primus had my back and went out of their way to make me a part of the team. They included me in company potlucks, took me go-carting, and got to know me during down periods in the shop. I am very grateful to Gary and the Primus team for this opportunity, and look forward to future full-time opportunities at Primus!
Josh Trujillo is a Mechanical Engineering Student at the Colorado School of Mines.
What are hypersonic weapon systems?
Hypersonic weapons are missiles that travel at speeds in excess of Mach 5 (five times the speed of sound). These extreme speeds are intended to make them very difficult to intercept and able to surprise an enemy with a precision strike. They also differ from ballistic missiles in that hypersonic weapons utilize a very ‘flat’ target trajectory and are intended to be maneuverable throughout their flight.
Hypersonic weapons generally fall into two broader categories:
- Hypersonic Glide Vehicles (HGV) – HGVs are launched from a rocket and then enter hypersonic travel in a glide phase
- Hypersonic Cruise Missiles (HCM) – HCMs are self-powered by scramjet engines when towards their target
Hypersonic weapons are of military interest because their high speed, maneuverability, and low trajectory make them very difficult to detect by terrestrial-based radar systems until much later in the weapon system’s flight. This late detection further complicates the command and control decisions as well as the challenge of technical interception of the weapon.
Most conventional hypersonic weapons utilize kinetic energy which is the energy generated by the weapon system’s extreme speed to destroy its target. Certain Chinese and Russian hypersonic weapons are intended to carry nuclear payloads.
Hypersonic weapons are of interest to the U.S. military because they provide the ability to rapidly attack targets with minimal chance of interception / defeat. Vice Chairman of the Joint Chiefs of Staff (VC-JCS) General John Hyten categorized the need for “responsive, long-range, strike options against distant, defended, and/or time-critical threats when other forces are unavailable, denied access, or not preferred.” Additionally, the growing hypersonic capabilities within the militaries of near-peer countries (e.g. China, Russia) creates the need for a similar capability within the U.S. military.
What are examples of U.S. hypersonic weapon programs?
Multiple U.S. military branches are pursuing hypersonic programs, including:
- US Army
- Long-Range Hypersonic Weapon (LRHW)
- US Navy
- Conventional Prompt Strike (CPS)
- US Air Force
- AGM-183 Air-Launched Rapid Response Weapon (ARRW)
- Hypersonic Attack Cruise Missile (HACM)
- Expendable Hypersonic Air Breathing Multi-Mission Demonstrator Program
- Defense Advanced Research Projects Agency (DARPA)
- Missile Defense Agency (MDA)
- Hypersonic Defense Regional Glide Phase Weapons System interceptor
Where do hypersonic weapons sit in their development curve?
In the United States, hypersonic weapon systems are in a relatively early state of development. While the idea of hypersonic munitions has been around for quite some time, serious investment in technology and operational products only began our of haste in 2018. Some of the technology development has surrounded ramjet engines capable of Mach 5+ travel while other efforts have focused on the materials required to sustain extreme temperature fluctuations while remaining lightweight and strong. With multiple branches of the U.S. military pursuing slight variations of hypersonic missiles for their own branch needs, the entire breadth of the defense industry is engaged in the development of these systems within the United States.
The American defense establishment is limited by a few key factors on the trajectory towards operational hypersonic weapons:
- Limited test facility and ranges
- Limited supply chain capable of producing high tolerance, complex components using exotic materials
- Long-range flight test corridors
As of this article, the U.S. Military and defense prime contractors are actively testing prototype hypersonic weapons across the full range of programs.
How are hypersonic weapons made?
While the exact manufacturing processes and engineering designs remain classified, the basic manufacturing process is similar to other aerospace and defense programs. The United States Department of Defense establishes the requirements (in this case for hypersonic weapons) and then defense primes and aerospace original equipment manufacturers (OEMs) bid on the work. Once a Prime and/or OEM is selected to produce the weapon, it is then up to that company to develop a manufacturing program and supply chain to support it. In most cases, Primes and OEMs work with contracted machining suppliers and/or aerospace component manufacturers experienced in complex machining to produce the high-tolerance parts that form the backbone of the hypersonic weapon. Other supply chain partners focus on electronic components, fasteners, carbon fiber components, controls, and aerodynamic surfaces. These suppliers (known as Tier I and II Suppliers) produce components and assemblies that are ultimately assembled into the finished hypersonic missile by the Prime / OEM and destined
for the U.S. Government.
Which American defense suppliers (OEMs) are involved in manufacturing hypersonic systems?
What are unique considerations for manufacturing parts and components which support hypersonic weapons?
The supply chain for hypersonic weapon development and production is similar to that of other high-performance defense systems. Key considerations for these suppliers include:
- Rapid prototyping and development capability – As designers and engineers work through the initial design iterations, suppliers must be configured to produce prototype / Low-Rate Initial Production (LRIP) parts rapidly and accurately.
- Ultra-high precision, complex machining – The high-velocity speeds of hypersonic systems requires high-tolerance components and assemblies to prevent failure during their use. These aerospace grade parts must be manufactured to exacting specifications and validated through stringent quality processes. Tolerances in the thousandths and millionths of an inch for linear, positional, and circular dimensions are common within hypersonic components.
- Ability to work with unique, exotic materials for heat tolerance and weight reduction – Hypersonic platforms and weapons experience extreme temperature fluctuations due to the speed and air friction they create. Additionally, the ability to achieve stable hypersonic speeds (Mach 5+) requires ultralight but extremely durable materials. These engineering challenges require contract manufacturers who can work with exotic alloys and materials such as Titanium, Inconel and Tantalum. In fact, the U.S. Air Force is currently sourcing carbon composite producers to develop a supply chain for production rates of ultra-lightweight structural components for hypersonic weapons.
- Suppliers configured for defense-specific security – It’s “no secret” that information and technical security is an essential part of delivering defense projects. Hypersonic projects require the highest levels of data security throughout their engineering and supply chain. The top defense suppliers (even Tier I and Tier II) must have extensive compliance experience with ITAR and relevant DFARS regulations. Additionally, hypersonic component suppliers should comply with the Cybersecurity Maturity Model Certification (CMMC) framework, accredited by an outside organization.
Primus Aerospace is a leading provider of high-precision, high-complexity machined components and assemblies for the aerospace, defense and space industries and a leading manufacturing partner to aerospace, defense & space OEMs / Primes & Tier I suppliers worldwide. Established in 1989, Primus Aerospace has grown into a vertically-integrated manufacturing operation that is strategically headquartered in Colorado and serves customers in North America, Europe, and the Middle East with a broad range of complex manufacturing, assembly, integration, and value-added services, including design & engineering support, program management and secondary manufacturing & processing capabilities. The company’s strategic focus is directed towards advanced manufacturing capabilities, automation & robotics integration and technical resources to drive turnkey solutions & world-class service for its customers. Primus Aerospace offers a broad array of build-to-print manufacturing and integration services, including multi-axis, complex machining, mechanical and electrical assembly, 3D titanium printing, water jet cutting, EDM, testing and design support. Primus is committed to delivering the most complex & critical solutions to the Aerospace & Defense industry by aligning capabilities and processes with the market’s evolving needs.
Congressional Research Service Report R45811
Government Accountability Office (GAO)
DoD Press Release – June 9, 2021
Cybersecurity in DOD Supply Chains