3D Printing

 3D Printing creates 3D objects adding material layer by layer using the information from a computer-generated 3D model.

What is 3D printing?

The fundamental principle of 3D printing is that it fabricates a 3D object directly from a 3D model by adding layer by layer of material and fusing them. It uses CAD-generated 3D models to manufacture a three-dimensional object by adding material layer upon layer and fusing them.

topology optimized 3d printed frame (Source – BMW)

Technologists early on referred to these technologies as rapid prototyping, but since then, they have made huge strides and moved from prototype to production-ready part manufacturing. As a result, these technologies are widely known as 3D printing, coined by MIT for inkjet printing in the 1990s based on a 3D printing technique they invented. As a result, these terms need to adequately describe recent technological advancements in the sector.

History of 3D printing

Chuck Hull, a 3D Systems Corporation engineer from the United States, is credited with inventing 3D printing in 1983 as a solid imaging process known as Stereolithography (SLA), the first commercial 3d printing technology, and the STL file format. Many 3D printing processes still use Hull’s contributions to the STL file format, digital layer slicing, and infill strategies.

Many companies have developed and introduced new techniques since then. However, because the technology is still relatively new, companies that develop and introduce new techniques may do so under new marketing terms, even if the core technology remains the same.

ASTM International technical committee finally defined these processes as Additive Manufacturing (AM) since it builds 3D parts by adding material rather than subtracting material instead of the subtractive manufacturing process.

ISO/ASTM standards define 3D Printing as additive manufacturing and classify it into seven types based on the techniques used to create the layers, the energy source, and the fuse material.

Types of 3D printing technologies

Material Jetting, Powder bed fusion, Vat photopolymerisation, Material Extrusion, Binder Jetting, Sheet lamination and Direct energy deposition are the seven leading additive manufacturing technologies. The standards are here.

Each of the seven types of 3D printing technologies differs based on the underlying technology used to lay material onto the build platform, the material type, the energy type used, and the post-processing.

Material extrusion

Material extrusion is a 3D printing technique that creates 3D parts using a continuous thermoplastic or composite material filament. S. Scott Crump invented and patented material extrusion in the 1980s as part of Fused Deposition Modelling (FDM).

Material-Extrusion – fused-deposition-modeling (FDM) 3D printing (Source:Makerbot)

The FDM printer feeds the thermoplastic filament through a heated nozzle while depositing the melted polymer layer after layer onto the bed to create a 3D part.

How does Material extrusion work?

Material Extrusion

Powder bed fusion (PBF)

PBF is a 3D printing technique that melts and fuses the material to form a 3D geometry part using either a laser or an electron beam. Powder Bed Fusion incorporates the following widely used printing technologies: Direct metal laser sintering (DMLS), Multi Jet Fusion (MJF), Electron beam melting (EBM), Selective laser sintering (SLS), Selective heat sintering (SHS), Selective laser melting (SLM),  are all examples of sintering techniques .

Powder bed fusion 3D printed part ( Source & Credit:GE)

Powder bed fusion processes, particularly Selective Laser Sintering (SLS), were pioneers in industrial additive manufacturing. A laser or electron beam is used in this method to melt the powdered material and fuse it to form a solid object.

How does Powder Bed Fusion(PBF) work?

Powder Bed Fusion

Vat Photopolymerization

This method employs Photopolymerisation, which involves using radiation-curable resins or photopolymers to create 3D objects by selectively exposing them to ultraviolet light. When these materials are exposed, they undergo a chemical reaction and solidify. Unfortunately, these technologies can only print on plastics.

SLA 3D printed parts (stereolithography) (Source:3dnatives)

This category includes three major types: stereolithography (SLA), digital light processing (DLP), and continuous digital light processing (cDLP).

How does Vat Photopolymerization work?

Vat Photopolymerization

Binder jetting process

As the name implies, this technique creates 3D parts by selectively depositing binding liquid, which joins the powdered material to form a 3D part. Since binder jetting does not use heating to fuse the material, this process differs from any other 3D printing technology.

Sand casting mould made using Binder jetting for impeller (credit:voxeljet)

The powder spreading head and the print head with bonding liquid add layers alternatively to create a 3D object. The printing follows the following steps.

• The powder is deposited and spread across the bed.
• Inkjet applies the binder as per the sliced layer data from a 3D model
• Bed moves down by the layer thickness
• The spreading head then recoats the material on top of the previous layer.
• The above steps repeat until the printer completes the entire part

How does Binding jetting work?

Binder Jetting

Material jetting

Material jetting 3D printer selectively deposits material droplets layer after layer into the build plate to create a 3D part. The depositing technique is very similar to traditional inkjet printers in that ink droplets are selectively deposited to create a 2D print. When the 3D printer finishes a layer, it cures it using ultraviolet light before moving to the next layer.

DOD – Drop on demand Material Jetting (Source:Solidscape)

The following commonly used printing technologies are included in powder material jetting: Drop On Demand (DOD), UV-cured Material Jetting, and NanoParticle Jetting (NPJ).

How does material jetting work?

Material Jetting

Directed energy deposition (DED)

Directed energy deposition technology employs focused thermal energy to create 3D parts. DED uses an electron beam, plasma arc, or laser to melt and fuse the material as the print head deposits to create a three-dimensional object. These are very similar to welding processes but much more detailed.

DED parts(credit :Sciaky)

LENS 3D printers use the geometric information in a Computer-Aided Design (CAD) solid model to independently direct the DED print head as it builds up the part layer by layer.

LENS and EBAM are the two leading Directed energy deposition technologies. EBAM employs an electron beam, whereas LENS uses a focused laser to melt the material.

How does Directed energy deposition work?

Directed Energy Deposition (DED)

Sheet lamination

Sheet lamination technologies stack and laminate sheets of material to create 3D objects using adhesive or ultrasonic welding. After the 3D printer finishes the print, the sections’ unwanted areas are removed layer by layer.

Sheet lamination 3D printed part (Source:fabrisonic)

Laminated Object Manufacturing (LOM), Ultrasonic Additive Manufacturing (UAM), and Selective Deposition Lamination (SDL) are all subsets of sheet lamination technology.

How does Sheet lamination work?

Sheet Lamination

Advantages and disadvantages of additive manufacturing

Advantages of additive manufacturing

• Without the use of any tooling, AM can print complex 3D geometries with interior features.
• When compared to machining, there is less waste.
• The part can be printed directly from the 3D model without needing a drawing.
• Product designers can create Prototypes faster, allowing designers to test different iterations more quickly, resulting in a shorter design cycle.
• 3D Printing requires minimum or no tooling compared to traditional machining for smaller batches.
• Printing is an option for production tooling.
• Various materials can be mixed during printing to create a one-of-a-kind alloy.
• Different sections of the 3D printed part can be different alloy variants.

Disadvantages of additive manufacturing

• Some of the 3D printing technology is still in its early stages. Hence the construction process is slow and expensive.
• High production costs as a result of equipment costs
• Depending on the 3D printing type used, various post-processing is required Small build volume compared to other manufacturing part sizes such as sand casting
• Because of the poor mechanical properties of some types of 3D printed parts, they require some post-processing.
• Poor surface finish and texture when compared to manufacturing processes such as CNC and investment casting.
• The parts’ strength is comparably lower.

How 3D printing technology works

Although the 3D printing process flow differs between the different 3D technologies used to create 3D parts, they all follow these simple steps to make the final part.

Three-dimensional modelling (3D model)

The designer uses CAD software or a 3D object scanner to create a 3D model. Since the 3D printer prints every feature from its 3D model, every detail on the model must be correct, and its external geometry must be fully defined.

CAD model

Although 3d printing gives the product designer greater design flexibility as it can print more complex parts than some traditional manufacturing processes, there are still constraints and rules to follow when designing for the best results.

The design guides differ depending on the additive manufacturing technology and material used. Part design guides are available from equipment manufacturers and 3D printing service providers. Refer to the 3d printing technology and their manufacturers to find out more.

CAD software for 3d printing

What CAD software can you use for 3D printing?

Solid works	CATIA
Blender	Creo elements
FreeCAD	Rhinoceros
Fusion 360	SolveSpace
OpenSCAD	Autodesk inventor
Onshape	BricsCAD Shape
Meshmixer	SketchUp Free
SelfCAD	TinkerCAD

CAD software

STL file creation

When the designer is satisfied with the product part design, the user converts the CAD file to a standard 3D printing format known as standard tessellation language (STL), which 3D Systems created in the late 1980s for use in its Stereolithography (SLA) machines. Here’s how the STL file is created and used for 3D printing.

STL file

Most CAD software can save 3D models as an STL files. However, all printer manufacturers have software that can convert any CAD format into an STL file. STL file tessellates the 3D shape and slices the part into digital layers. Along with other factors, layer thickness determines the final print quality.

STL file transfer  – 3D printing software

The user transfers the STL file to the printer, often manipulated to orientate for printing using either 3D printing software or custom 3D printer software. At this stage, machine software may create a file with additional information, such as support structure and temperature.

3D printer set-up

Each 3D printing technology and its variants have steps and requirements for creating a new printing job. Material selection, orientation, printer temperature, support structure, and build platform levelling are all part of the setup process. It also entails loading print material, binders, and other consumables into the Machine.

Machine setup – with support

Then the 3D printer software converts STL information into G-code. Multiple parts can be set up to reduce printing costs, and waste can be reduced by selecting the correct orientation.

What is a G-code?

G-code instructions instruct the machine axes the positions to move in a three-dimensional space, how fast to move, and what path to take.

3D printing step

When the build begins, it builds the design one layer at a time. A typical layer is about 0.1mm thick, but it can be as thin as 20 microns, depending on the technology and material used.

Part in build platform

Depending on the build size, printing machine, 3D printing technology, material, and printing resolution, the build process could take minutes, hours or days.

Part removal

Sometimes, printed parts require a cooling-off period before removing them from the Machine. Removal can vary depending on the Machine and technology, from simply peeling off the build platform like in FDM printers to cutting the DMLS parts using wire EDM.

3D-built part with supports

Post-processing step

Almost all 3D printing techniques need some level of post-processing. Depending on the 3D printing technology used and the end-user requirement, it can range from removing supports and gentle cleaning to machining and heating treating the part.

Finally, post-processing steps such as cleaning, polishing, and painting may be necessary.

3D printing materials

Every year, the number of 3D printing materials available multiplies as market demand for specific materials and mechanical properties drives advancements in material science. These countless material choices make it impossible to overview all 3D printing materials comprehensively. Still, Because each 3D printing method is only suitable for a limited number of materials, some broad generalisations are possible.

So, what material is used in 3d printing? The most common 3D printing materials are thermoplastic and thermoset polymers, but composites, metals, ceramics, and sand can also be 3D printed.

• Polymers
  • Thermoplastics – FDM & SLS
  • Thermosets – Material jetting, SLA & DLP
  • Metals – DMLS, SLM, Binder jetting & FDM
  • Composites – FDM & SLS
  • Other – Sand – Binder jetting

Material Extrusion

 In material extrusion, plastic filament is fed through a heated extruding nozzle and deposited onto the building platform layer by layer.

What is Material extrusion?

Material extrusion is an additive manufacturing technique using continuous thermoplastic or composite material filament to construct 3D parts. The plastic filament is fed through an extruding nozzle, which heats the material to a molten state and then deposits it layer by layer onto the building platform to create a 3D part.

Material extrusion – FDM printer

Material extrusion is now the most popular additive manufacturing process in terms of availability for general consumer demand and quality under the Fused Deposition Modeling (FDM) type of printer.

As per ISO/ASTM 52900:2021, it is one of the 7 Additive manufacturing processes. You can read the other types here.

How does Material Extrusion work?

Material extrusion printers typically have a build platform and a printing nozzle head gantry in a three-axis system. The schematic image shows that the printing head gantry moves in X & Y while the build platform moves in the Z-axis. Variants of this printer configuration include Cartesian, CoreXY, delta, SCARA, belt, H-bot, and polar.

Part Preparation – The 3D model is converted into layer-based information – Read our “How AM works?” article to understand how the model is converted by slicing software.

Machine set up – The printer is loaded with thermoplastic filament in spools or pellets. This will depend on the printer manufacturer and material extrusion types.

Printing – The extrusion nozzle head move along the X-Y plane which allows the nozzle tip to move and will start depositing the material layer by layer in predefined areas to cool and solidify.

The following video by Solid Concepts explicitly outlines the Material extrusion process.

FDM technology (Source:Solid concepts)

Material extrusion types

Material extrusion technology was first developed in the 1980s by S. Scott Crump under the registered name of Fused Deposition Modelling (FDM). The term fused deposition modelling (FDM) and its abbreviation FDM are trademarked by  Stratasys Inc., a company co-founded by Scott Crump.

Since FDM’s inception, new material extrusion technologies have emerged with slight variations. 

• Fused Deposition Modeling (FDM)
• Fused Filament Fabrication (FFF) – Plastic Jet Printing
• Pellet Extrusion
• Composite Filament Fabrication (CFF)
• Direct Ink Writing (DIW)
• Bound Metal Deposition(BMD) / ADAM

Fused Deposition Modeling (FDM)

Developed by Stratasys, FDM is one of the earliest and most well-known forms of material extrusion. It involves melting thermoplastic filaments and depositing them layer by layer to create a 3D object.

Read our ultimate guide to Fused Deposition Modeling, which details the FDM process, its pros and cons and the material choices.  

Fused Filament Fabrication (FFF) – Plastic Jet Printing

Similar to FDM, Fused Filament Fabrication is a term often used interchangeably. It’s a more open term for similar processes that utilise melted filament for layer-by-layer printing. This method is not limited by proprietary technologies.

Fused filament fabrication (FFF) is developed by the members of the RepRap project which is not restricted to use by others. You can read all about RepRap here. This is also referred to as Plastic Jet Printing.

Pellet Extrusion printer & Fused Filament Fabrication printer

Pellet Extrusion

This technique involves using raw plastic pellets instead of filaments. In Pellet Extrusion, the pellets are melted and extruded through a nozzle to create the layers.

The most significant advantage of Pellet extrusion technology is its material availability. Pellets are the most widely available and used polymer format in the manufacturing industry. Hence, Pellet Extrusion benefits from an established supply chain with lower material costs. 

Pellet Extrusion printers by Pollen

How does Pellet Extrusion Work?

As the image shows, the extruder consists of an auger screw, extruder die, heating elements, and a material cartridge for the pellets. The process works very similar to an injection moulding machine in how it melts the pellets and pushes the molten plastic through the nozzle.

Pellet Extrusion head ( Source:Pollen)

The printer head is then articulated by an XYX gantry system to print the parts as per the 3D model. 

Composite Filament Fabrication (CFF)

What is Composite Filament Fabrication (CFF)?

Composite Filament Fabrication (CFF) adds continuous fibre strands such as carbon or fibreglass reinforcement to create composite, lightweight yet metal-like solid parts. CFF material extrusion technology, which uses two print nozzles, was introduced by Markfroged. 

Composite Filament Fabrication printed part

CFF is very similar to reinforced concrete with rebar. Like rebar reinforcement increases the strength of the brittle concrete, in CFF, the continuous fibre increases the strength of the part by increasing the strength. 

Fibreglass	Fiberglass is sturdy and comparably cost-effective and increases the part strength.
Carbon Fibre	Carbon Fibre is stiff and strong and behaves like aluminium alloy 6061. It is used for lightweight parts that carry medium to heavy loads.
Kevlar	Kevlar would make high-toughness and shock resistance parts, making it ideal for parts that undergo shock loading and are high-impact. It bends instead of breaking.
HSHT Fiberglass	High Strength High Temperature (HSHT) Fiberglass is a good candidate for high-temperature applications as it maintains strength and stiffness. This is because of its high heat-deflection property.

Composite Filament Fabrication fibre options

How does Composite Filament Fabrication Work?

Composite Filament Fabrication printing steps

• The CFF process begins by extruding and depositing a thermoplastic layer, which forms the part’s infill and shells. This serves as the composites’ matrix material.
• Next, the continuous fibre is introduced into the matrix, which fuses with the thermoplastic using compatible resin coating. 
• The above process is repeated layer by layer to create a composite structure with fibres as the backbone of the 3D-printed part. 

Composite Filament Fabrication advantages

• High strength-to-weight ratio – Like conventional concrete and rebar, continuous fibres with thermoplastic materials create parts with exceptional strength-to-weight ratios, making them strong and lightweight.
• Design flexibility – Since fibres form the backbone, they can be laid out in specific orientations or patterns to optimise the part’s functionality.
• Part feature enhancement – Fibres can be placed in specific areas to increase localised strength per the part’s functionality. 

Composite Filament Fabrication disadvantages

• Cost – As with any other 3D printing technology, initial equipment costs are high, which drives the manufacturing cost higher.
• Post-processing – Depending on the part design and final use, manufacturers might need post-processing techniques such as curing and heating.

Direct Ink Writing (DIW)

Direct Ink Writing

Direct Ink Writing (DIW)is another material extrusion technology variation predominantly employed at meso- and micro-scales.  This method dispenses liquid-phase “ink” through tiny nozzles at controlled flow rates, depositing it along digitally defined paths to construct 3D structures layer-by-layer.

Direct Ink Writing video

The DIW process can achieve very high material resolution, enabling the development of embedded circuitry and rapid manufacturing of sensors. Compared to traditional manufacturing, DIW eliminates masking and etching steps in electronic manufacturing.

Bound Metal Deposition (BMD)

BMD is a metal extrusion-based AM technology process where the metal powder-filled thermoplastic rods are extruded to create 3D parts. Instead of filament spools and pellets, bound metal rods, which are metal powders held together by either wax or polymer binders, are used. BMD is also known as Atomic Diffusion Additive Manufacturing (ADAM). 

Bound Metal Deposition (BMD) – ADAM

Desktop Metal’s patented process is called Bound Metal Deposition (BMD), while Markforged Inc. named their AM process Atomic Diffusion Additive Manufacturing (ADAM).

Advantages and Disadvantages of Material Extrusion

Advantages of Material Extrusion

• Wide selection of print material
• Easily understandable printing technique
• Easy and user-friendly method of material change
• Low initial and running costs compared to other AM techniques
• Comparably faster print time for small and thin parts
• Printing tolerance of +/- 0.1 mm (+/- 0.005″)
• No supervision required
• Small equipment size compared to other AM
• Comparably low-temperature process

Disadvantages of Material Extrusion

• Visible layer lines
• The extrusion head must continue moving, or else the material bumps up
• Supports may be required
• Poor part strength along the Z-axis (perpendicular to the build platform)
• Finer resolution and wider area increase print time.
• Susceptible to warping and other temperature fluctuation issues such as delamination
• Toxic print materials

Material extrusion materials

Although a variety of materials can be used in material extrusion, thermoplastics like acrylonitrile butadiene styrene (ABS), aliphatic polyamides (PA, also known as Nylon), high-impact polystyrene (HIPS), polylactic acid (PLA), and thermoplastic polyurethane are the most popular.

Lately, material extrusion 3D printing has successfully extruded paste-like materials like ceramics, concrete, and chocolate, as well as plastic materials like polyether ether ketone (PEEK) and polyetherimide (PEI).

As long as the base thermoplastic material is present sufficiently to ensure fusion between the layers, material extrusion can also be used with composite materials. This implies that components made of printed materials can contain components made of wood, metal, or even carbon fibre.

Material	Key properties
ABS (Acrylonitrile Butadiene Styrene)	Strength, Impact Resistance, Durability
PLA (Polylactic Acid)	Biodegradability, Ease of Printing, Low Warping
Nylon (Aliphatic Polyamides)	Toughness, Flexibility, Chemical Resistance
HIPS (High-Impact Polystyrene)	Rigidity, Impact Resistance, Smooth Finish
TPU (Thermoplastic Polyurethane)	Elasticity, Abrasion Resistance, Flexibility
PEEK (Polyether Ether Ketone)	High-Temperature Resistance, Chemical Resistance
PEI (Polyetherimide)	High Strength, Flame Resistance, Dimensional Stability
Fiber Reinforced Filaments	Enhanced Strength, Stiffness, Lightweight
Metal-Infused Filaments	Metallic Finish, Conductivity, Mechanical Strength
Wood-Infused Filaments	Natural Appearance, Texture, Wood-like Characteristics
Ceramic Filaments	Heat Resistance, Smooth Surface Finish, Non-conductive

Material extrusion materials

Material extrusion applications

Material extrusion can produce non-functional prototypes, production jigs, and small pre-production batches for testing and concept models. 

During the embodiment design stages of product design, it can make rapid prototyping for multiple iterations cost-effective.

Material	Applications
ABS (Acrylonitrile Butadiene Styrene)	Prototyping, Automotive Parts, Electronics Casings
PLA (Polylactic Acid)	Prototyping, Medical Devices, Food Packaging
Nylon (Aliphatic Polyamides)	Gears, Bearings, Functional Prototypes
HIPS (High-Impact Polystyrene)	Prototyping, Models, Display Items
TPU (Thermoplastic Polyurethane)	Flexible Components, Phone Cases, Footwear
PEEK (Polyether Ether Ketone)	Aerospace Components, Medical Implants, Automotive
PEI (Polyetherimide)	Electrical Components, Aerospace Parts, Automotive
Carbon Fiber Reinforced Filaments	Automotive Parts, Aerospace Components, Prosthetics
Metal-Infused Filaments	Jewellery, Prototyping for Metal Parts, Decorative Items
Wood-Infused Filaments	Furniture Prototyping, Decorative Objects, Artifacts
Ceramic Filaments	Prototyping for Ceramics, Artwork, Custom Pottery

Typical application

What Is the Difference Between Material Jetting and Material Extrusion?

Material jetting and Material extrusion are two different 3D printing technologies that differ in their processes and mechanisms.

Material Jetting operates similarly to inkjet printing. It involves jetting tiny droplets of photopolymer materials onto a build platform. These droplets are often cured with UV light to solidify and form layers. This process is repeated layer by layer until the object is fully printed.

Material extrusion involves the deposition of molten thermoplastic filament through a heated nozzle onto a build platform. The nozzle moves according to the design specifications, laying down layers of material that fuse together upon cooling to form the final object.

Property	Material Jetting	Material Extrusion
Material	photopolymers or resins that solidify under UV light are used in material jetting. These materials can produce high-resolution prints with fine details and smooth surface finishes.	A wide range of thermoplastics, such as PLA, ABS, PETG, and more, can be used in material extrusion. The choice of material affects properties like the final print’s strength, flexibility, and temperature resistance.
Accuracy & Resolution	Material jetting offers high resolution and accuracy, making it suitable for applications requiring intricate details and precise dimensions.	While material extrusion can produce detailed prints, its resolution might be lower than that of material jetting. Layer lines might be more visible, affecting the surface finish.
Post-processing	Often, parts produced by material jetting may require additional post-curing to achieve optimal mechanical properties and surface finish.	Parts printed through material extrusion often require less post-processing. However, smoothing techniques or additional treatments might be applied to improve surface quality.

Material Extrusion vs Material Jetting

Recommended reference

Diegel, Olaf, et al. A Practical Guide to Design for Additive Manufacturing. Springer Nature Singapore, 2019.

Celik, Emrah. Additive Manufacturing: Science and Technology. Walter de Gruyter GmbH, 2020.

Stratasys. Stratasys – Industrial 3D Printing Manufacturers, https://www.stratasys.com/en/Desktop Metal. Desktop Metal. Define the future. Make it real. | Desktop Metal, https://www.desktopmetal.com/.