The 7 Types of Additive Manufacturing
What is Additive Manufacturing?
Additive manufacturing is the process of creating a solid object from a 3D model using 3D printers. In AM, the material, or filament, is added one layer at a time and a fusing application, such as a heated printhead or laser, is used to bind the layers. This results in a 3D-printed object.
For example, stereolithography is considered the first industrial rapid prototyping technology and is known today as a 3D printing or additive manufacturing method.
In this article, we’ll go over seven of the most common additive manufacturing technologies to help you identify the one that meets your particular needs.
7 Types of Additive Manufacturing Processes
Here are the seven most commonly used additive manufacturing techniques.
Material extrusion is an additive manufacturing technique in which thermoplastic material is pushed through a heated extrusion nozzle and deposited layer by layer to build an object.
Fused filament fabrication (FFF), also referred to as fused deposition modeling (FDM), is the most commonly used additive material extrusion process.
Here’s how FFF material extrusion works:
A heated extrusion head precisely lays thermoplastic material over the print bed according to 3D CAD (computer-aided design) data. The build platform then lowers by a thickness of one layer and the next layer of material is applied. Layers solidify and fuse together as they cool down, thus building the part.
The completed part is removed from the print bed and support materials are cleaned. Freshly printed FFF parts have visible layer lines, so post-processing is done to produce a smooth surface finish.
Industrial-grade materials such as ABS and PLA are commonly used for FFF due to their high heat resistance and excellent strength-to-weight ratio.
FFF is used in a number of industries, including aerospace, automotive, and medical, to produce functional and durable prototypes and parts.
Sheet lamination, also called laminated object manufacturing (LOM), is a rapid prototyping process in which sheets of material are joined together to create an object.
It is commonly used for building durable 3D objects with complex geometries.
Here’s how sheet lamination works:
A roll of build material, such as paper, is introduced on the build surface. Next, a bonding adhesive is applied to the build material and a heated roller moves over the surface of the material, thus binding the material. A computer-guided laser beam or knife is then used to cut the sheet according to 3D CAD data, removing excess material. The next layer of the material is positioned on the print bed and this process is repeated until the part is complete
Ultrasonic additive manufacturing (UAM) is a type of sheet lamination process that uses principles of ultrasonic welding to produce metal parts. It uses CAD data to ultrasonically bind layers of metal sheets to metal substrate surfaces.
A bonding adhesive is used to join paper sheets, whereas moderate force and high-frequency vibratory energy are required to create metal parts.
Binder jetting, also known as drop-on-power printing, is a 3D printing process that creates solid objects using a 3D CAD file. It works with a variety of materials, including ceramics, composites, sand, and plastics.
In binder jetting, the process uses a modified version of the inkjet printing process, therefore not requiring a heat source to bind the materials.
Here’s how binder jetting works:
Building material is applied to the print bed. Next, the print head selectively binds the build material according to the part’s 3D CAD data. The build platform is then lowered by the thickness of a single layer. This process is repeated, connecting the layers of powder into a finished part.
Material jetting is a full-color additive manufacturing technique in which droplets of thermoplastic are selectively deposited using drop on demand (DOD) technology, similar to how an inkjet printer dispenses individual ink drops only when needed.
In material jetting, the print head is not heated to bind the material. Instead, an ultraviolet (UV) light source is used to cure the liquid resin.
Here’s how the material jetting process works:
The print head deposits a layer of liquid photopolymer resin on the print bed. A UV source moves over the deposited layer, polymerizing the build material. The build platform then moves down by the thickness of one layer, and another layer of material is added over the previous layer. This process repeats until the entire 3D object is finished.
Directed Energy Deposition
Directed energy deposition (DED) is an additive manufacturing process that uses a heat source, such as a laser or electron beam, to melt metal powder or wire. Parts are created by melting material and placing it where it is needed. It is commonly used to repair or add additional features to existing parts.
Here’s how DED works:
Metal powder or metal wire is fed through a nozzle, and an energy source is introduced to melt the metal feedstock. This melted metal pool is then applied using G-code to the specified surface where it hardens into a solid structure.
Powder Bed Fusion
Powder bed fusion (PBF) is an additive manufacturing technology that uses a heat source, such as an electron or laser beam, to melt and join material powder to create three-dimensional objects. This technique can be used to create both plastic and metal parts.
There are four types of powder bed fusion processes depending on the source of heat used. Direct metal laser sintering (DMLS), selective laser sintering (SLS), and selective laser melting (SLM) use laser fusion, electron beam melting (EBM) uses electronic beam fusion, multijet fusion uses agent and energy fusion, and selective heat sintering (SHS) uses thermal fusion.
Here’s how powder bed fusion works:
A thin layer of powdered material is spread over the overbuild stage. Next, the PBF machine applies a heat source to selectively scan over and fuse the powder into a first cross-section of the part using the 3D CAD data. The build platform is then lowered by the thickness, and a new layer of powdered material is spread on the previously deposited layer. This process is repeated over and over again until the entire part is created.
Support structures are not required in PBF processes. The printed part is simply removed from the build platform and cleaned to undergo post-processing.
Vat polymerization is an additive manufacturing process that uses a vat, or container, filled with photosensitive liquid resin and a light source to create solid objects.
Here’s how vat photopolymerization works:
The build platform lowers from the top of the tank filled with liquid polymer. An ultraviolet light source selectively cures liquid resin according to the pattern defined in the 3D CAD data file.
Upon contact with the light source, the photopolymer undergoes a chemical reaction and solidifies. This process is known as photopolymerization.
The build platform then lowers by one layer height and more resin flows over the top of the print bed. A sweeper blade moves over the previous layer to ensure that a thin coat of liquid resin is spread out evenly on the surface. This process is repeated layer-by-layer until the part is finished.
The printed part is then removed from the resin and from the build platform. It is then submerged in a chemical bath that washes away excess resin and cured in a UV oven to increase its stability and strength. At this point, any support materials are removed from the printed part.
Vat polymerization is a broad class, encompassing a number of 3D printing technologies, including stereolithography (SLA), digital light processing (DLP), and continuous liquid interface printing (CLIP).
New Additive Manufacturing Technologies
Digital Light Synthesis™ is the newest innovation in additive manufacturing that uses Carbon’s CLIP™ (continuous liquid interface production) technology to produce functional parts with exceptional surface finish and mechanical properties.
Here’s how Carbon DLS™ works:
- A transparent tank is filled with ultraviolet-curable liquid as base material.
- UV images are projected from the bottom of the tank causing the UV curable resin to solidify.
- The print bed is slowly raised, allowing the resin to flow under the cured layer.
- An oxygen-permeable window called the “dead zone” is created between the uncured resin below the printed part and the window. Since oxygen is known to inhibit radical polymerization, it prevents curing between window and resin.
- As a result, liquid resin continuously flows under the part just above the dead zone.
- This process continues until the entire object is printed from bottom to top.
The printed part is then baked in a thermal bath which strengthens the material to achieve the desired material properties.
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