What Is Additive Manufacturing?

Oct 11, 2023

Additive manufacturing refers to production methods that build physical objects from a digital file using computer-aided design software. Materials are added one layer at a time to create functional parts of a whole, such as in 3D printing, stereolithography and electron-beam melting.

Additive manufacturing is an umbrella term for the production methods in which three-dimensional objects are built from digital files in a computer-controlled process that “adds” material one layer at a time.

“It’s similar to baking a cake from scratch — you add materials to produce objects,” said Ramsey Stevens, CEO at nano3Dprint, a company that manufactures material extrusion systems that 3D print electronics. “This differs from conventional manufacturing processes that subtract materials or rely on molding processes.”

In contrast to machining, in which blocks of metal are whittled down into desired shapes, and molding, where liquid resin is poured into containers that squeeze them into their final form, additive manufacturing builds customizable designs from scratch by adding only the amount of materials necessary.

Often used interchangeably, additive manufacturing and 3D printing are commonly mistaken as synonyms; however, this isn’t the case.

While 3D printing, more formally known as material extrusion, is one type of additive manufacturing, not all additive manufacturing involves 3D printing.

There are other types of production that fall under the additive manufacturing umbrella besides 3D printing, including ones that specifically build with powder-based materials, or bind their products with heated lasers or liquid adhesives. (In contrast, 3D printing typically refers to a process where a filament mixture flows from a nozzle.)

“The term ‘3D Printing’ is a misnomer and was devised as a marketing term during the early days of the technology,” Aditya Chandavarkar, co-founder of Additive Academy, an additive manufacturing education platform, told Built In.

“With the advances that are coming up now,” he added, “we are transitioning from simple prototyping to manufacturing with these technologies, making ‘additive manufacturing’ a more appropriate term.”

Additive manufacturing creates physical objects from a digital design. Using a CAD model or a scan of a replicable subject, software translates a digital file into a three-dimensional framework, which essentially splices the subject into thin layers. Once uploaded, a manufacturing machine follows the digital blueprint like a set of instructions, constructing the object from the bottom up.

Depending on the specific additive manufacturing process, the next steps could involve extruding a filament mixture from a nozzle guided by a horizontally moving robotic arm, such as the case in 3D printing. Or it could look like a thermal gun welding thin, aluminum sheets, fed through a system of rollers, as in laminated object manufacturing.

The main idea remains the same though: materials — which can come in the form of a powder, liquid or paste-like gel — are applied in layers, then fused together via an external source. The platform vertically lowers down, and the next layer is applied. This process repeats until the final layer is set, completing the design.

Today, everything from polymer composites, metals, ceramics, foams, gels and even living tissues are used in additive manufacturing.

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Binder jetting constructs objects using powdered materials and a liquid binding agent. As layers of powder are spread across a build tray, print heads zip across x, y and z axes to deposit an adhesive substance that glues it all together — no heat necessary. Binder jetting is quick in its delivery, making it ideal for bringing prototypes to life. It has also been used to create casting patterns, aerospace parts and jewelry.

Examples: Furan binder, silicate binder, phenolic binder, aqueous-based binder

Material jetting builds objects one droplet at a time. During this process, an oscillating print head micro-deposits material onto a build tray with precision. This technique is similar to an inkjet printer, and is the only additive manufacturing method capable of mixing resins in a single print. Use cases include industrial tooling, prototypes and anatomically accurate medical models.

Examples: PolyJet printers, nanoparticle jetting, drop-on demand

Directed energy deposition uses a focused energy source — such as a laser, plasma arc or electron beam — mounted on a robotic arm that melts materials as they are being deposited. The multi-axis robotic arm’s ability to deposit materials at any angle means that directed energy deposition can also be used to repair or maintain existing parts, according to additive manufacturing platform Markforged.

Examples: Laser engineering mesh formation, directional light production, direct metal deposition, 3D laser coating

Perhaps the most recognizable of all additive manufacturing methods, material extrusion is what we commonly think of as 3D printing. In a continuous stream, machines extrude spooled, slurried filament through a heated nozzle as the robotic arm it’s attached to outlines the structure. Layers solidify via temperature control or the use of a chemical bonding agent. Material extrusion is popular among hobbyists as it’s user friendly, doesn’t come with a steep learning curve and is relatively inexpensive after you get started. Currently, it’s being used to build houses, engineer meat and bioprint human hearts.

Examples: Composite filament fabrication, fused filament fabrication, fused deposition modeling

In powder bed fusion, layers of powder are sintered, or coalesced, together by a heat source, typically a laser. Working on a powder-sized scale, this method is known to create high-precision structures with fine details and intricate geometries. Generally speaking, parts made from powder-bed infusion display exceptional weight distribution and dimensional accuracy, resulting in extraordinary mechanical properties unfeasible to traditional manufacturing methods.

Examples: Direct metal laser melting, direct metal laser sintering, electron beam melting, selective laser sintering, selective heat sintering

Sheet lamination bonds sheet stacks of various materials — paper, plastic or metal foil — using either welding, heat, pressure or a type of adhesive. Excess build surrounding the solidified object serves as structural support, which is eventually removed and recycled for the next project.

Examples: Ultrasonic additive manufacturing, selective deposits layer, laminated object manufacturing

This additive manufacturing technique uses ultraviolet light to turn liquid polymers into solid structures in a process known as photopolymerization. Sitting in a vat of resin, the object is cured by light that is directed and intensified with mirrors. This route of additive manufacturing forms accurate, intricate parts complete with fine details and smooth surfaces and is commonly used to create surgical tools, hearing aids and facial prosthetics.

Examples: Stereolithography, digital light processing, liquid crystal display

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Perhaps the greatest benefit credited to additive manufacturing is its unbound possibility. If it can be designed into a CAD model, then it can be built. Today’s techniques have reached a level of intricacy in crafting fine detail and complex geometric shapes previously impossible via traditional methods.

Some of the most complex designs to date include AI-engineering startup Hyperganic’s aerospike engine and a pair of 3D-printed lung scaffolds, bioprinted using 44 trillion voxels that consist of 4,000 kilometers of pulmonary capillaries and 200 million alveoli.

One major benefit of partnering a heavily computerized process in combination with pristinely accurate technology is effortless personalization. Additive manufacturing can reproduce a design to a near exact degree, reducing variance between batches as well as cost.

When juxtaposing a factory made part next to its 3D-printed clone, it’s likely the latter is lighter in weight. This is because additive manufacturing enables creators to remove as much material as possible without impeding on a part’s functional integrity, building smarter designs with optimal geometry. The lightest material used in this field, as 3D-printing blog Bitfab has it, is polypropylene, weighing in at 0.9 grams per cubic centimeter. Although two parts may seem identical to the eye and even operate the same, lightening the load is a gamechanger in automotive and aerospace industries.

Once a user presses “print,” machines and software systems take it from there. They can expect their design to be delivered as a whole — no joining necessary with minimal post-production requirements. A user may need to remove supportive structures before they can move on to sand, polish and paint.

Additive manufacturing machines offer on-demand access to any possible design. For companies, this means being able to print parts as needed, bypassing supply-chain bottlenecks or regenerating spare parts for legacy products with access to a virtual inventory. For creators, this means rapid prototyping and accelerated product development cycles, with the ability to tweak the design as you go.

While NASA and SpaceX explore the future use of additive manufacturing printers in space to construct habitats on celestial bodies, naval aircraft carriers now commonly carry these machines to produce spare parts as needed.

“Users can make novel applications and form factors, including conductive and functional materials when they need it,” nano3Dprint CEO Stevens said. “Additive manufacturing, such as 3D printing, allows users to turn ideas into reality within a day.”

Additive Academy’s Chandavarkar describes additive manufacturing as one of the most material efficient ways of production. By definition, it’s a process of addition. So when a project begins, it is calibrated to only use the essential amount of raw materials necessary to complete a design. Less waste is inherent in this approach, which translates to a stronger circular economy and more sustainable manufacturing processes in the long run.

Consider the end-to-end production cycle. Scott Shuppert, CEO of 3D modeling company CAD/CAM Services, explained how industry-wide adoption of additive manufacturing practices could lend itself to greener practices, such as localized, on-site production of parts and therefore reduce transportation needs.

“By only using the necessary amount of material for each part,” he said, “additive manufacturing also leads to energy savings.”

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Today, the cost of additive manufacturing remains too high to be considered viable for a number of applications. According to 3D printing, post-processing and automation company AM Flow, the price of 3D printing is still between 10 to 100 times more expensive than an injection molding alternative. Initial startup costs for machinery can set one back anywhere from $200 to $500,000 and upward. Additionally, raw materials used in many cases are expensive, as they are difficult to source, and need to be prepared in proper form, whether as filament, powder or paste-like gel, relative to the machine.

The primary classes of materials used in additive manufacturing only span polymers, metals, ceramics, composites and sand. That’s it. Additive manufacturing is in its infancy compared to well-established procedures with decades of materials development to stand on, but that seems to be changing.

“The range of materials available for additive manufacturing is rapidly expanding, with advanced composites, aluminum, titanium and various poly and carbon materials constantly being introduced,” Shuppert said. “These advancements will contribute to the production of stronger, lighter and more cost-effective parts.”

Additive manufacturing’s biggest challenge, as Chandavarkar sees it, is accessing information being gatekept by major players in the space.

“There are more technologies that are expensive only due to the fact that they are held back by intellectual property rights, leading to an increase in capital expenditures when investing in such technologies,” he said.

It’s only when the cost of printers, raw materials and other essentials, like software programs, steadies that industry will be able to pull additive manufacturing into the mainstream.

Sure, additive manufacturing is commonly viewed as a quick turnaround solution, capable of constructing a three building, 1,851 square-foot project in eight days or producing a prototype on the fly. But this advantage is limited to sole projects delivered in small batches.

“While additive manufacturing is well suited for prototyping and low-volume production,” Shuppert said, “scaling up to high-volume manufacturing can be difficult due to factors such as print speed, limited printer capacity and post-processing requirements.”

Additive manufacturing is an umbrella term that refers to several types of manufacturing methods, one of which is the material extrusion process known as 3D printing.

Types of additive manufacturing include binder jetting, material jetting, directed energy deposition, material extrusion, powder bed infusion, sheet lamination and vat polymerisation.