What is Additive Manufacturing?

Manufacturing is an integral part of most industries around the world. From creating engine or machinery parts, to medical devices and aesthetic decorations, everything needs to be formed from an original material.

Additive manufacturing (also known as additive layer manufacturing, or colloquially as 3D printing) is a comparatively new way of creating an object that leverages innovative technologies to build an item layer by layer. As you will discover later in this article, this process is completely different to traditional methods such as machining or moulding, and affords the designer and engineer a lot more freedom during the manufacturing process. Keep reading to learn more…
 

How does additive manufacturing work?

The basic principle of additive manufacturing is that the resulting object is built in layers, from the bottom to the top, rather than moulded, cast, or machined. 

But, how does additive manufacturing work? 

Firstly, a designer or engineer creates a “blueprint” for the object. This can be using CAD (computer-aided design) software or 3D object scanner to make a digital plan. Next, using complex geometry, specialised software translates this into a format that allows the machinery to build your chosen component in continuous layers until completed.

This sounds pretty simple, but there are a range of processes and technologies that will impact the functionality and quality of your end result.
 

Additive manufacturing processes

Below, we’ve picked out some of the primary processes that additive manufacturing machinery can use to create an item.
 

Binder jetting

Binder jetting is a process that uses a powder material and liquid adhesive to create the desired object.

Firstly, the build platform is covered in a layer of the chosen powder material. This can be stainless steel, ceramic, or various polymers depending on the required function of the object. A liquid binder is distributed by the print head, which moves horizontally along an x and y-axis and creates the shape of each layer. Successive layers of powder and adhesive are deposited until the component is finished, while any excess or unused powder is removed afterwards.

This is a relatively speedy process, and allows for a broad range of colours, shapes, and binder-powder combinations. However, it may not be suitable for structural items, due to the binder material. It may also need additional processing to smooth any rough edges, which adds to time and labour.
 

Directed energy deposition (DED)

The label of directed energy deposition is used to cover a range of methods, such as ‘laser engineered net shaping, direct metal deposition, or 3D laser cladding’. Unlike other additive manufacturing processes, this technique is commonly used to repair or add to existing components, rather than create new ones. 

One of the more complex options, during DED a chosen material is deposited from the printer nozzle onto an existing surface. This is usually in powder or wire form. It is then melted into place via a laser, electron beam, or plasma arc. Once it solidifies, more layers can be added to build up the structure.

The primary advantages of this technique are that there is a lot of flexibility in movement of the nozzle. Instead of being fixed on an axis, this can move in multiple directions to deposit the material where it’s needed for stronger repairs. However, the finish can vary depending on the material chosen, so you may need to conduct additional post-processing for refinement.

Note: while you can use ceramics and polymers in a DED machine, metal is much more common.
 

Material extrusion

Material extrusion additive manufacturing is somewhat similar to the technique above, but with less freedom of movement. Instead of depositing a powder, wire, or filament that is then melted, material extrusion heats the chosen material in the nozzle. This is then deposited in layers in its melted state, which fuse together as they harden.

This is perhaps the method many are most familiar with, as it’s commonly used in domestic or hobby 3D printing machines. 

This method of additive manufacturing is relatively inexpensive, and the success with which it models plastic polymers means the materials used are fairly accessible. However, there are a range of factors that will impact your results. The accuracy and speed can be limited compared to other processes, which tends to negate any benefits for an industrial scale. The material also needs to be extruded at a consistent pressure in a continuous stream – any disruptions to this will severely impact the final result.
 

Vat polymerisation

Vat polymerisation is an additive manufacturing process that uses selective curing of a photopolymer to build an object. 

Within the machine, there is a vat of liquid photopolymer (most typically a type of resin). A laser or UV light is shone into the vat according to the design; when it touches the photopolymer, the material starts to harden, forming the layers needed to build the object. 

The build platform lowers after each layer, allowing for more liquid to flow over the item and be made into the next layer. Once complete, the vat is drained of any remaining liquid and the object can be removed.

Vat polymerisation is relatively quick, with a high level of accuracy, and objects tend to be completed to a high standard. However, the process is quite expensive, and you have limited options for build material. It also requires a lot of post-processing, such as additional curing for structural strength.

Powder bed fusion

Unlike many of the other techniques we’ve explored in this article, powder bed fusion is a collective term that covers a range of different melting or attachment processes. These include:

• Electron beam melting (EBM).
• Direct metal laser sintering (DMLS).
• Selective laser melting (SLM).
• Selective heat sintering (SHS).
• Selective laser sintering (SLS).

At the core of powder bed fusion, the chosen method is used to melt/fuse a powdered material to form layers of an object. On top of the build platform, a powder bed is selectively hit with a laser or electron beam until the powder forms one layer of your chosen design. More powder is spread out using a roller, and the process continues until the component is complete. Excess powder can then be removed during post-processing.

These techniques are ideal for building components of various materials, and can be relatively inexpensive (aside from EBM, where the electron beam requires a vacuum). However, they can be slower than other methods, and do not have the desired strength or durability for structural parts.
 

Sheet lamination

Lastly, we have sheet lamination. In this type of additive manufacturing, sheets of a material are rolled along like a conveyor belt. When in position, the sheet is bonded to the layer below via an adhesive or ultrasonic welding, and then cut into the right shape. The remaining material is removed along the roller to allow for the next layer. This is repeated until the object has been formed. 

Overall, this process is relatively quick, has a low-energy demand, and can be used for complex internal geometries. However, there is a lot more material waste, and often requires post-processing to fully finish the item.
 

Terms to know

During additive manufacturing, materials are primarily fused together via a couple of different technologies. These are:

• Sintering: this is where powders are compacted or melted to form a solid mass, but not to the point of liquefaction.
• Stereolithography: this is a process whereby objects are created via the hardening of a liquid material on contact with a light source (e.g. the UV curing of resins).
   

Advantages of additive manufacturing

In order for additive manufacturing and 3D printing to be worthwhile, there has to be valuable benefits on a domestic or industrial scale. Some of the primary advantages of additive manufacturing are:

• Bespoke parts: additive manufacturing is incredibly adaptable, and can be used to create bespoke items. It’s also possible that 3D printing can be used for out-of-production items (such as classic car engine parts), where a traditional method would be too costly compared to the volume of parts needed.

• Advanced customisation: 3D printing is perfect for highly customised items, particularly as the design can be adapted right up to the last minute before printing. This makes it a huge boon to the medical industry, for instance, where prosthetic pieces and assistive technology are better when customised to a high degree for individual users.

Note: both of these advantages go to show that small-scale production can massively benefit from additive manufacturing. Where the number of products required remains low, 3D printing can be a cost-effective way to produce what is needed. It also helps with stock management, as pieces can be printed on-demand.

• Quick prototypes: in marketing or research and development, 3D printing can allow for the creation of quick prototypes for testing or showcasing. This cuts down massively on manufacturing costs, allowing designers and engineers to test new items more freely.

• Minimal material waste: since a component is being built in layers, rather than carved out, additive manufacturing methods produce significantly less material waste. This is important for sustainable manufacturing and resource preservation.

• Eliminate assembly: building a component layer by layer allows for more complex designs that would otherwise have to be assembled from multiple parts. This streamlines the production process, can reduce material costs, and improve efficiency.

• More complex designs: built on a foundation of complex geometry and layering, 3D printed parts can be more creative or complicated (as long as the design can be translated into a layer-by-layer template).

• Improve component features: additive manufacturing allows engineers to produce forms that otherwise may not be possible through traditional methods. For example, components with an internal lattice structure can reduce the overall weight of a part (ideal in the aerospace or automotive industry), or incorporate internal channels within the design to improve the functionality.
   

Limitations of additive manufacturing

Of course, you cannot have the good without the bad; and there are some current limitations that will impact how effective and efficient additive manufacturing can be for different industries. These include:

• Technological infancy: at the time of writing, large-scale additive manufacturing is still relatively within its technological infancy. Over time, current disadvantages (like those we mention below), may be mitigated by advances in technology.

• Limited materials: compared to traditional manufacturing methods, 3D printing is limited in the choice of materials you can use. While certain techniques will work with paper, polymers, ceramics, or certain metals, this is still a small selection, and can impact how useful the technology is within your industry.

• High costs: while it can vary depending on your chosen process, there is a high cost of entry to additive manufacturing. Machinery and material costs can limit which businesses can make use of these methods.

• Limited speed: some 3D printing methods can be quick, especially in the domestic sphere, where time pressure is less of an issue. However, for industrial or commercial processes, additive manufacturing is still fairly slow compared to traditional assembly lines.
   

Additive manufacturing FAQs

With this foundation of knowledge, you may still have some questions around this technology. To help provide more clarity, we’ve answered some of the most frequently asked questions below.
 

Is additive manufacturing the same as 3D printing?

Technically, yes. Additive manufacturing and 3D printing are the same principle, whereby an object is built using a layer-by-layer process. The primary difference between the terms seems to come from context use. 

3D printing is more commonly used when referring to domestic, hobbyist, or commercial production, whilst additive manufacturing is used in industrial settings.

Note: we have used both terms fairly interchangeably throughout this article.
 

What materials can be used?

The type of additive manufacturing process you choose (as explained above) will dictate the materials you can build with. The most common materials used in 3D printing can be split into the following categories:

• Biochemicals: while difficult to handle due to their viscosity, materials like silicone are slowly coming into use in 3D printing.
  Ceramics: this includes materials like alumina and powdered glass, and can be used across a wide range of industries (see more below).
• Metals: stainless steel and titanium are ideal for additive manufacturing, especially on an industrial scale where strength and durability are essential.
• Thermoplastics: commonly used in domestic and industrial additive manufacturing, thermoplastics like PVA (polyvinyl alcohol), ABS (acrylonitrile butadiene styrene), and PLA (polylactic acid) are lightweight and adaptable.

What industries use additive manufacturing?

As additive manufacturing has improved, various industries around the world have taken advantage of this technology, including:

• Aerospace: within this industry, the interest in 3D printing comes from unique product customisation, weight reduction to maximise fuel efficiency, and reducing carbon emissions.

• Automotive: the assembly line is a huge part of the automotive industry. Improvements to component production can save money, whilst the quick turnaround of prototype designs can speed up the aesthetic and functional designs of new models.

• Medical: small-scale item production with high customisation is revolutionary in the medical industry, where prosthetic attachments, hearing aids, and surgical components can all benefit from being made on-demand according to individual specifications.

• Maritime: relatively new to the table, the maritime industry could benefit from the on-demand nature of production. Strategic placements could allow parts to be made right at major ports, reducing the wait time for repairs or replacements.

• Consumer: various consumer industries may see the benefits in additive manufacturing for more complex items, and can experiment with more complex product designs.
   

How long does it take to create a component?

Asking how long additive manufacturing will take is much like asking “how long is a piece of string?”. The answer is, it depends.

The size, shape, materials and techniques used, and complexity of design all influence how long it takes to fully manufacture a component. This means that there is no firm answer; your piece could take anywhere from a few minutes to several days to build.
 

How much does additive manufacturing cost?

Providing an exact cost is similar to offering a timeframe for item production, in that it is a combination of factors that will determine the answer.

Initial machinery investments are often very costly, especially techniques using an electron beam, due to the additional equipment required to maintain it. Your material choice will also ramp up the costs; metal powders are far more expensive than polymers, which are relatively cheap per kilogram. You will also need to invest in proper CAD programmes to create your designs.

While a decent hobbyist 3D printer can be anything from a couple of hundred to thousands of pounds, industrial units are much more costly: coming in at anywhere between £100,000 to several million pounds.
 

How does additive manufacturing differ from traditional manufacturing methods?

Traditional manufacturing can include techniques like injection moulding, machining, forming, and joining. These are often collected under the banner of subtractive manufacturing, as you need to take material away to create the desired objects. This is very obviously different to additive manufacturing, where a material is added to build an object layer by layer. 

These distinct differences in production means each method has pros and cons, and the best method for your needs will depend on what you’re looking for in the end product. For example, if you’re looking for:

• Strength and durability: traditional methods are still better for structural components.
• Complex designs: additive manufacturing uses geometry to create more complex shapes and designs, which can help with innovation and product research.
• Quick assembly: additive manufacturing negates much of the need for additional assembly, which can help to improve speed and productivity.
• Broader material choice: traditional machining and manufacturing offers more choice of material, which can help with component functionality.
• Product quality and finish: most traditional methods result in a high finish and superior product quality first time, while additive manufacturing may need additional post-processing to refine the object.
• Minimal waste: building layer by layer reduces material waste, which is more sustainable and cost-effective.
• Small-scale product development: for products needed in small quantities, or with advanced customisation, additive manufacturing can be incredibly valuable. Traditional methods often have more initial set up, but are excellent for consistent mass production.

For most industries, there is a time and a place for both types of manufacturing. A hybrid model allows you to get the best of both worlds to ensure maximum productivity and efficiency.
 

The Lab: home of materials science in the North West

Designing and building new components is an exciting process. But you need to ensure that anything you wish to use is suitable for the job, and in compliance with industry guidelines.

This is where The Lab can help. Our expert team of metallurgists and material scientists have years of experience offering valuable advice on material choice and design recommendations. We also have the technology required to conduct in-depth material analyses and inspections to ensure component quality.

Contact us today for more information on how we can help you, or to arrange an obligation-free consultation.

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Resources

Loughborough University Online, ‘About Additive Manufacturing’.