A Guide to Manufacturing Aerospace Parts

The aerospace and defense industry is known for producing complex and advanced products—jet engines, aircraft, rockets, satellites, drones, and more—that move fast in a highly regulated environment. It is no wonder that these factors of speed, complexity, and policy compliance play key roles in the manufacturing process. This design tip explores how to improve aerospace development cycles through:

• accelerating production with digital manufacturing
• reducing components, which helps in lightweighting part design, cuts items in an overall assembly, and reduces costs
• using a range of manufacturing methods and materials, which can accelerate development and add value to your designs
• streamlining quality and compliance assurances

1. Use Digital Manufacturing to Accelerate Product Development

At Protolabs, we understand the importance of speed. Working extensively with companies in the aerospace and defence industry, we have accelerated the development over the years of a range of metal and plastic aerospace parts and products that include: 

• Heat exchangers
• Manifolds
• Turbo pumps
• Liquid and gas flow components
• Fuel nozzles
• Conformal cooling channels

Metal aerospace parts have been produced by a range digital manufacturing methods, including GE’s additively manufactured fuel nozzle, left, for CFM International’s LEAP aircraft engine, right.

One of the drivers in our success is through experience and rigorous development of digital manufacturing tools. We have found the right blend of working with autonomous digital tools and hands-on application engineers to meet aerospace demands.

When starting the digital manufacturing process with many manufacturers, it can be easy to upload a CAD file into multiple online quoting tools.

Unfortunately, some manufacturers' online quoting tools don’t take into account all of the back-end requirements, or offer all of a manufacturer’s processes. This is where we choose to be upfront so that each step required for the part or project is reflected in the initial quote.

When using online digital tools, quoting software can greatly accelerate development and production cycles.

However, to get the most out of these tools, make sure you are working with software (and a manufacturer) that includes the following: 

• Takes into account all requirements and steps of the build or project
• Offers all available processes and materials 
• Offers trained and experienced staff with years of manufacturing experience 

A major challenge in the aerospace and defence industry is on-time delivery and quality. Industry sources say around 80% of orders generally show up on time. Yet, when those orders do show up on time, about 25% of parts do not meet the required quality. A common complaint from aerospace companies is when vendors promise a lead time with a cheaper price but could not deliver within the timeline quoted. Delays have led to missed deadlines and greater costs to fix than if they would have just started with the higher-priced vendor.

Our online, interactive quoting system turns your CAD model into a quote with immediate design analysis and feedback. Your design can be reworked to determine the ideal balance of processes, materials, time, and cost. This greatly increases efficiency as it isn’t necessary to talk with someone every time a part is needed. But when you need a knowledgeable person on your side, we have a team of applications engineers ready to back up our automated tools. All contacts, customer or not, get free access to our responsive team that understands how to design for our processes, reduce cost, and answer a myriad of other technical questions.

2. Reduce Components to Benefit Product Design

You may want to reduce overall components in a part or product design for several reasons.

First, lightweighting is crucial in aerospace. Companies know just how many ounces of fuel it takes to fly a gramme of weight in flight, for example, so slight reductions drive major gains. The choice of materials, and sometimes the method of manufacturing, also factor into this lightweighting equation. But trimming part count helps, too.

Second, cutting costs is important. Plastics and metals can be expensive, and so can assembly time. Accordingly, if designs can lessen the number of components or parts, this can reduce materials and assembly time.

With these lightweighting and cost considerations in mind, which materials work best for aerospace components? Titanium is often a go-to choice, available through machining and 3D printing services. This lightweight and strong material offers excellent corrosion and temperature resistance. Aluminium, and its high strength-to-weight ratio makes it a good candidate for housing and brackets that must support high loading. Aluminium also is available for both machined and 3D-printed parts. Inconel, a 3D-printed metal, is a nickel chromium superalloy ideal for rocket engine components and other applications that require high-temperature resistance. Stainless steel also is a frequent materials choice. For example, SS 17-4 PH is used in the aerospace industry due to its high strength, good corrosion resistance, and good mechanical properties at temperatures up to 315 degrees C. Like titanium, it can be machined or 3D printed. Liquid silicone rubber is also widely used in the industry. This elastic fluorosilicone material is specifically geared toward fuel and oil resistance while optical silicone rubber is a good PC/PMMA alternative. Common applications in aerospace include soft-touch surfaces, gaskets, seals, and O-rings.

Reducing components and combining part assemblies can improve aerospace product design in several ways: trimming a part’s weight, cutting costs, reducing inventory, and streamlining supply chains.

Finally, beyond lightweighting and cost cutting issues, the aerospace industry faces unique benefits and challenges with high risks and rewards. Companies are concerned with development cycles, prototyping, hot-fire testing, and production. So, while component reduction can help reduce part weight and assembly time, the real savings are in the reduction of the headaches and overhead associated with the supply chain and paper trail for each part. In aerospace, each component that goes into the final product has a tremendous amount of validation behind it such as material traceability, shock and vibe tests, rigorous inspections, and much more. In such a regulated industry, reducing parts can provide great value by reducing inventory, having fewer documents to track, and streamlining your supply chain.

3. Deploy a Range of Manufacturing Methods, Materials

If you have an internal machine shop but have to deal with a lot of different types of manufacturing in a small space, you might have taken projects to outside vendors for development work. It is important to find the right vendor with the capacity to meet your high demands for quality and speed. You may know but it bears repeating that there are no universal processes or materials. You need all the tools in your arsenal to find the best solutions to stay on the cutting edge. Therefore, work with companies that are able to offer a range of manufacturing processes and materials. We offer CNC machining, sheet metal fabrication, injection moulding, and five different industrial-grade 3D printing (additive manufacturing) methods in-house, more via our network. Additionally, you can choose from hundreds of commercial-grade plastics, metals, and elastomers that are suitable for both prototyping and production. See our Materials Comparison Guide for a complete list.

Subtractive Processes and Materials:

CNC machining methods, specifically three- and five-axis milling, are frequently used in manufacturing today.  For the aerospace industry, common materials are aluminium, hard metals such as 304, 316, and 17-4PH stainless steel, and titanium.

What isn’t common are the size and geometric dimensioning and tolerancing (GD&T) capabilities of many shops. While it is common for the customer to state what tolerances are needed, look for companies that state what size and GD&T they can deliver.  

Most aerospace customers have complex parts that can be more advanced than even our automated machining facilities can handle.

For detailed information on  tolerances, minimum and maximum part dimensions, and other design guidelines, visit our basic design guidelines for CNC milling.

Additive Manufacturing—Processes and Materials:

A considerable amount of aerospace and defence parts are metal. Accordingly, when it comes to metal 3D printing or additive manufacturing, most common materials are Inconel 718, the aluminium alloy AlSi10Mg, stainless steel (304 & 17-4), titanium, and cobalt chrome (CoCr). Again, the difference here will be the material and additive manufacturing processes available.

We use multiple additive processes: stereolithography, direct metal laser sintering (DMLS), selective laser sintering, Multi Jet Fusion,  and PolyJet. DMLS has proven to be a desirable process in the aerospace industry because it offers:

• large range of materials
• increased functionality
• ability to accommodate complexity and organic designs

Beyond the manufacturing methods referenced (subtractive and additive), we also offer a number of secondary or finishing options, if your design calls for these applications:

• Post-process machining - for 3D-printed metal parts
• Heat treatment
• Anodising
• Basic assembly
• Chromate plating

DMLS can additively manufacture large, production-grade metal parts (as shown). This large-format metal 3D printing, from our GE Additive Concept Laser X-Line machine, is an example of how our company is technology agnostic, using machines, equipment, and processes sourced from a variety of companies.

• Cleaning
• Part marking
• Plus more via our network

If you need several vendors for different processes or secondary processes, remember the benefits mentioned earlier about using one supplier with multiple processes. We offer many processes and materials while operating as a local vendor to reduce time and costs.

4. Rely on Quality and Compliance Assurance

Finally, aerospace product designers and developers need to carefully navigate government and safety policy and compliance issues. Working in such a highly regulated industry, it is important to find vendors familiar with aerospace requirements. Traceability, documentation, testing, and certified parts that are compliant in an ISO 9001 and AS9100D environment can decrease much of the work needed to be done, tested, or verified in house. 

Governing bodies are continuously working on standards for additive manufacturing, so knowing exactly what is needed may be difficult to find for non-traditional processes. However, standards or certifications for finished parts apply no matter how it was manufactured. You will want to make sure vendors have certified materials, powder analysis, material traceability, and more depending on your needs.   

We have already invested heavily in digital manufacturing methods to provide you with automated tools, documentation, testing, and traceability, all supported by our applications engineers, delivering you a streamlined and efficient digital thread. We offer the following quality documentations and report options in an ISO 9001, and (through our network) AS9100D compliant environment: 

• Material certifications
• Certificate of conformance (CoC) 
• First article inspections (FAI) 
• Various other inspection requests such as CMM, X-Ray or CT scanning

Ultimately, we will work with you to find the best solution and consider all steps of your project. If you would like more information, contact our applications engineers at +44 (0) 1952 683047, email us at customerservice@protolabs.co.uk, or start your design today by uploading your 3D CAD model to receive an interactive quote within hours.