Metal 3D Printing：A Definitive Guide（2021）

Industrial Applications

Metal 3D printing has found its niche in a number of industries, with players in the aerospace, automotive and medical industries at the forefront of driving innovation with the technology.

In this section, we take a look at the most common applications for the technology, as well as key use cases that have unlocked the benefits of metal 3D printing. 
Industry Common applications Aerospace Fuel injectors, blades, combustor liners, rocket engine manifolds, brackets, functional prototypes Automotive Air ducts, brackets, uprights, knuckles, turbochargers, suspension assemblies, transmission plates, brake calipers, manifolds  Medical and dental Custom-fit dental restorations, such as stages, crowns, and bridges; customised orthopaedic implants (hip, knee, and spinal), surgical tools Industrial goods Tool inserts with conformal cooling channels, industrial pump components, bearings, stators, heat exchangers, impellers, tooling repair 

Aerospace 

The aerospace industry has been a huge pioneer of metal 3D printing. By using the technology, aerospace companies hope to produce more efficient, lightweight aircraft parts to improve aircraft performance.

Within the aerospace industry, metal 3D printing is used in a range of applications, from functional prototypes to tooling, replacement parts and structural aircraft components.

General Electric 

A great example is General Electric (GE), which is extensively using metal 3D printing to make and develop new products. GE’s subsidiary, GE Aviation, is producing fuel nozzles for the LEAP family of jet engines, with an aim to manufacture 100,000 fuel nozzles by 2020. 

Having achieved the milestone of 30,000 3D-printed fuel nozzles in October 2018, GE looks like it’s well on its way to fulfilling this goal.

Using advanced design tools and Electron Beam Melting technology, GE’s engineers were able to create a fuel nozzle 25% lighter and 15% more fuel efficient than its traditionally produced counterpart.

The breakthrough in this case is that the fuel nozzle was printed as a single unit, whereas previous models incorporated 20 separate parts which needed to be subsequently assembled.

But GE has not stopped here. The company is also building its GE Catalyst, an advanced turboprop engine that has more than a third of its components 3D printed in various metals.

Similar to its fuel nozzles, the engineers behind the turboprop have achieved considerable part consolidation, reducing the number of parts produced from 855 to just 12. A redesign will also help to reduce the fuel burn of an engine by as much as 20%.

Automotive 

Automakers have been using 3D printing since the technology’s early days — Ford Motor Company, for example, notably bought the third 3D printer ever made.

For many years, metal 3D printing has proved to be a cost-effective tool for prototyping and producing jigs and fixtures. However, advancements with the technology mean that more opportunities are opening up for end-part production.

Automotive companies can use metal 3D printing to create lightweight metal parts, leading to enhanced vehicle performance and lower fuel consumption. This is particularly beneficial for the motorsports industry, where 3D-printed car parts can offer racing teams significant performance advantages.

Another area of interest for the industry is also using 3D printing to produce spare parts that are typically produced in low volumes. 3D printing spare parts on demand enables automakers to receive parts at the point of need, reducing inventory costs and increasing agility.

BMW

BMW is another company using 3D printing extensively. Most notably, the company has recently moved into the series production of a 3D-printed metal component for its 2018 BMW i8 Roadster vehicle.

Using topology optimisation, designers were able to optimise the vehicle’s roof bracket — a fixture for the folding/unfolding mechanism of the vehicle’s soft top. 3D printed in aluminium alloy powder (AlSi10Mg), the new roof bracket is 44% lighter than its conventionally made counterpart.

Furthermore, engineers optimised the design of the bracket to eliminate support structures. By doing so, the team was able to increase throughput from 51 to 238 of these parts per platform. This makes BMW’s roof bracket the first automotive component to be mass-produced with the help of metal 3D printing.

Bugatti

An exciting application of metal 3D printing comes from luxury car manufacturer, Bugatti. The French automaker has developed a 3D-printed brake caliper to be used on its Bugatti Chiron supercar.

An essential part of the braking system, the brake caliper has been made lighter and stronger thanks to 3D printing. Measuring 41 x 21 x 13.6 cm, the part took 45 hours to print using SLM technology and titanium powders.

By using 3D printing, Bugatti also achieved a 40% weight reduction for the caliper, when compared to machined aluminium alternative.

In 2018, the company successfully tested the brake caliper, proving that it can meet extreme strength, stiffness and temperature requirements.

Audi

Audi presents a different business case for metal 3D printing. In this case, the German automaker is using the technology to produce spare parts that are in low demand.

Metal 3D printing allows Audi to produce these parts on demand, producing and supplying spare parts as they are needed. This in turn greatly simplifies logistics and warehousing.

Audi identified that smaller, complex components would be most suited for metal 3D printing. A good example of a component is water adapters, which Audi is already producing for the Audi W12 engine. The company says that the load capacity of the components is comparable to that of parts manufactured using traditional methods.

Medical 

In the medical field, metal 3D printing allows highly customised medical devices, like orthopedic implants, to be created.

It’s far from unusual for off-the-shelf orthopaedic implants to be used for replacement surgeries. However, prefabricated implants can sometimes cause problems after the surgery as they don’t always fit properly.

To avoid this, 3D printing is increasingly being used to create customised, patient-specific implants with improved functionality.

For example, implants can be designed with improved porosity and surface texture, facilitating the growth of the tissue around the implant. This level of complexity can only be achieved with 3D printing. SmarTech Publishing predicts that more than 2 million implants will be 3D printed in metal by 2025. 

Additionally, metal 3D printing can be used to create hip and knee joint replacements, cranial reconstruction implants and spinal implants.

Lima Corporate

Italian medical device manufacturer Lima Corporate has been bringing additively manufactured hip implants to market for 10 years, using Electron Beam Melting (EBM) technology.

The company developed a technology for 3D printing biocompatible titanium in cellular solid structures that resemble natural bone. Such structures are used to coat an implant, allowing it to be better integrated with human tissue.

The technology is said to have helped almost 100,000 patients, enabling better implant performance and outcomes.

Industrial Goods

When it comes to the design and manufacture of tooling equipment, 3D printing can empower engineers to overcome traditional limitations. This can mean being able to create a mould or core in a matter of days instead of months, significantly reducing lead times.

Within the injection moulding industry, moulds are typically CNC-machined. Here, production costs can range from from $20,000 to hundreds of thousands of dollars. Lead times can last between 2 to 4 months. Additionally, moulds can often require multiple design iterations to achieve the final design, a costly and time-intensive process.

However, metal 3D printing can overcome these inefficiencies in several ways. First, the technology enables rapid design iterations, enabling changes to be made with relative ease.

Second, the performance of tooling aids and components can be enhanced with additive manufacturing.

For example, conformal cooling channels, lattice structures, and complex core/cavity shapes, which are too expensive or impossible to manufacture traditionally, can be factored into a mould design and 3D printed.

Conformal cooling channels are particularly beneficial as they help to achieve more homogenous heat transfer within the mould, compared to traditionally drilled straight-line cooling channels, resulting in greater cooling characteristics.

GW Plastics 3D prints moulds with conformal cooling

GW Plastics, US-based mould maker, has invested in hybrid metal 3D printing with the goal of building injection moulds with conformal cooling. One of the key reasons for this investment is faster cycles and better part quality enabled by 3D-printed moulds.

In fact, the company says 3D-printed moulds can save up to 30% of the cycle time by reducing cooling time. Furthermore, metal 3D printing allows GW Plastics to print a mould as a single piece, thus eliminating the need to assemble multiple components.

Post-processing

Post-processing is an unavoidable step when 3D printing metal parts. Post-processing helps to improve the mechanical properties, geometrical accuracy and aesthetics of a part, ensuring that a part meets the required design specifications.

Before printing your part, it’s important to understand the various post-processing methods that can be used to finish a metal part.

In this section, we’ll be looking at some of the main post-processing steps that can help to achieve the necessary finish for metal 3D-printed parts.

Stress relief 

High temperatures and subsequent cooling are a common occurrence during the metal 3D printing process. However, when a metal part is subjected to such extreme temperature changes, this can lead to residual stress.

To avoid deformations that can occur as a result of a build-up of residual stress, parts produced with powder bed processes must undergo a stress relieving cycle. The number of stress relief cycles depends on the metal or alloy used to produce a part.

In order to protect the surface of a part from oxidation, the stress relieving heat treatment takes place in an inert (typically argon) atmosphere. Parts are typically heat treated while still attached to the build platform.

During the stress relieving cycle, the whole platform is placed in a furnace, where the part is heated to a temperature range between 550-675°C for 1 to 2 hours and then cooled down slowly. Stress corrosion cracking can also be reduced through this stress relief process.

Hot Isostatic Pressing (HIP)

Secondary heat treatment like Hot Isostatic Pressing (HIP) helps to improve the microstructure and mechanical properties of a metal part.

With HIP, high temperatures (up to 2200ºC) and isostatic inert gas pressure (from 100 to 3100 bar) are applied to a part to achieve the highest possible density, reduce porosity and eliminate internal voids.

The HIP treatment of metal parts results in optimum mechanical properties that can be compared with wrought and cast alloys.

Important to note is that the natural cooling in an HIP system can take between 8 and 12 hours. However, HIP systems powered by uniform rapid cooling technologies have been developed, allowing for the parts to be cooled from 1,260 to 300°C in less than 30 minutes.

Powder removal

With powder bed processes, a printed part is encapsulated in the unused powder which needs to be removed once the printing process is complete. The excess powder can be removed manually or automatically with the help of specialised equipment, and then recycled for later use.

The removal of any unmelted powder trapped inside a part should also be taken into consideration. For this reason, at least two escape holes should be factored into the design to help easily remove powder after printing.

Part removal 

Once a part has been printed, it will need to be removed from the build platform. Build plates are then machined separately to remove excess material and return them to a usable state.

Wire Electrical Discharge Machining (WEDM) is the process of choice for cutting metal parts away from their build plates. WEDM involves creating electrical dischargers, releasing sparks which rapidly cut away material. Although the process is comparatively slow and used only with electrically conductive metals , it leaves a clean, smooth surface.

Cutting parts away with a bandsaw is another, considerably faster method. However, the process lacks the precision of wire EDM. However, if a part is going to be CNC machined afterwards, this precision can be sacrificed in favour of a faster post-processing time.

Support removal

Support structures are often considered a necessary evil when it comes to 3D printing, and this is particularly the case with metals.

Powder bed fusion technologies, like SLM and DMLS, will always require supports to ensure that they are anchored to the base plate and to mitigate the effects caused by residual stresses.

These supports are typically made from the same material as the part itself and help to minimise defects such as warping or cracking resulting from the high processing temperatures.

Supports are typically removed with the help of CNC machining. However, it’s a good practice to design as few supports as possible. In the Designing for Metal 3D printing section, we look at some of the ways to reduce the amount of support structures.

Surface finishing

As we’ve seen, a metal part that has just been printed won’t have the necessary properties required of the finished part. To achieve a smooth finish for a metal part, there are a number of common surface finishing techniques, including machining, sand blasting, media blasting and polishing.

For example, metal polishing can be used to achieve a ‘mirror-like’ finish for your part. Typically, polishing will be required before other surface treatments are conducted, in order to prevent corrosion and improve the appearance of the part. Applications are typically in the aerospace and automotive industries, as well as medical.

Abrasive blasting methods, such as sandblasting, bead blasting and media blasting, involves an abrasive material being forcibly sprayed onto a part to achieve a smooth surface.

Designing for Metal 3D Printing

Key Considerations

Metal additive manufacturing gives us the freedom and flexibility to produce parts with complex shapes and intricate features. However, as with any technology, it does have its own set of capabilities and limitations. Understanding the basics of design for metal 3D printing is therefore crucial to obtain a successful print.

Below are some of the key considerations to keep in mind when designing for metal 3D printing.

1。 Wall Thickness

Choosing the right wall thickness can make the difference between a successful and a failed print.

As a general rule of thumb, it’s recommended to design walls with a minimum wall thickness of 0.4mm.

It’s also important to ensure that the wall thickness of your parts are not too thin or thick, as this can result in deformation during the printing process or cause damage after removal from the build plate.

In the case of thick walls, the mass can be minimised by applying lattice or honeycomb structures, making the overall printing process cheaper and faster.

2。 Support structures 

While it’s ideal to design a part with the minimum amount of supports necessary, support structures will virtually always be required with metal 3D printing technologies (except for DED).

Supports play two main roles:first, they are used to anchor a metal part to the base plate to draw away heat, which could otherwise cause residual stresses and build failures.

Second, supports are required to successfully print complex features such as holes, angles and overhangs. For these features, angle measures should be noted:overhangs with an angle less than 45° will require supports.

For features located inside a part, such as horizontal holes along the X or Y axis, it’s generally recommended to design angled support structures.

Angled supports can help maintain a solid connection with the printing bed while minimising the amount of contact the supports have with your part’s surface area. This will make post-processing much easier.

Finally, make sure to check that all support structures will be accessible after printing. Any supports that are difficult to reach will be hard to remove cleanly.

3。 Overhangs and Self-Supporting Angles

Overhangs are unsupported downward-facing surfaces, and will need to be carefully considered when designing a part.

Large overhangs (typically over 1mm) will require support structures to prevent them from collapsing during the printing process. The maximum length of an unsupported horizontal overhang is typically 0.5mm, and it is important to keep your overhangs below this length.

If your design requires overhangs, you can also design fillets and chamfers under the downfacing surfaces to make the overhang self-supporting.

Angled features can be designed self-supporting. For this, the angle of a feature should not be less than 45°.

4. Part Orientation

Part orientation is another critical consideration with metal 3D printing. Experimenting with the orientation of your part is the best way to minimise the amount of support structures needed.

For example, if you want to make a metal part with hollow tubular features, a horizontal orientation will take up more space, while a vertical or angled orientation will save space and reduce the amount of supports needed.

Part orientation is also important in determining the accuracy and surface roughness of a part. When selecting your part orientation, keep in mind that downward and upward facing surfaces will have different surface roughness (so-called down-skins tend to have inferior surface finish). If you want to produce detailed features with the best accuracy, make sure to orientate these on the upward facing surface of the part.

5。 Channels and Holes

Metal additive manufacturing is notable for its ability to produce parts with internal complex channels for improved fluid flow and holes. A general rule of thumb is to not design such features under 0.4mm in powder-bed processes and under 0.2mm in Metal Binder Jetting. Holes and tubes larger than 10mm in diameter will require support structures.

Keep in mind that perfectly round horizontal holes are still a challenge to 3D print. Consider redesigning such shapes into a self-supporting teardrop or diamond shape.

Additionally, if you are designing a hollow part, you need to factor in the design escape holes to ensure the removal of the unmelted powder. A recommended diameter for escape holes is 2-5mm.

Conclusion

Metal 3D printing:a viable manufacturing technology

Metal 3D printing is emerging as a viable manufacturing technology, as advancements across the spectrum of hardware, materials and software continue to be made.

The technology could help to drive new business models and product development strategies by enabling economic low-volume and on-demand production, innovative design possibilities and, of course, mass customisation.

Of course, it will take some time for companies to become fully confident with the technology. However, an increase in knowledge sharing and education will not only help to further the potential of metal 3D printing, but will also spur a wider adoption of the technology across industries.

Discover More Metal 3D Printing Resources:

Expert Interviews

Digital Alloys CEO Duncan McCallum on Joule Printing and the Future of Metal 3D Printing 

HP’s Global Head of Metals on the Impact of HP Metal Jet
 

ANSYS’ Chief Technologist on Achieving Metal 3D Printing Success with Simulation 

Sintavia President Doug Hedges on Achieving Serial Production with Metal 3D Printing 

APWORKS CEO Joachim Zettler on Finding the Right Business Case for Metal 3D Printing

SmarTech Analysis’ Scott Dunham on the Future of Metal 3D Printing, Service Bureaus and the AM Materials Market [Part Two] 

MELD Manufacturing CEO Nanci Hardwick on Fulfilling the Potential of Metal Additive Manufacturing 

3DEO’s President Matt Sand on Taking Metal 3D Printing Into High-Volume Production 

VELO3D’s VP of Technology Partnerships on Expanding the Capabilities of Metal 3D Printing 

Metal 3D Printing Technologies

Metal 3D Printing:Where are We Today?

All You Need to Know About Metal Binder Jetting

Metal 3D Printing:What is Direct Energy Deposition?

An Introduction to Electron Beam Melting 

An Introduction to Wire Arc Additive Manufacturing

Your Guide to the Top DMLS Machines [2018]

Designing for Metal 3D Printing

6 Important Design Considerations for Metal 3D Printing 

Making Metal Parts Lighter with Metal 3D Printing

Metal 3D printing Materials

Why Materials are the Key to Metal 3D Printing Success:Expert Interview with voestalpine’s Armin Wiedenegger 

3D Printing Precious Metals – a New Approach?

Scalmalloy:The Latest High-Performance Material for Metal 3D Printing

A Quick Guide to 3D Printing Metals 

A Guide to 3D Printing With Titanium

Metal 3D Printing Challenges 

5 Common Problems Faced with Metal 3D printing – and How You Can Fix Them

Quality Assurance for Metal 3D Printing:Solving 3 Common Challenges 

Metal 3D Printing Applications

5 Innovative Use Cases for Metal 3D Printing

How Can 3D Printing Benefit Metal Casting? Here Are 3 Ways