Types of 3D Printing
ASTM (The standard for 3D) classifies 3D Printing into 7 main categories. Let us understand these further!
Material Extrusion
Vat Photo-polymerization
Material Jetting
Binder Jetting
Directed Energy Deposition
Powder Bed Fusion
Sheet Lamination
1. Material Extrusion
Material extrusion 3D printing is similar to drawing with a pen on a paper, only this time instead of a pen there is a nozzle that pushes out heat melted plastic instead of ink. The process of depositing plastic is repeated layer on layer to form the desired shape. The process is known by various names such as FFE - Fused Filament Extrusion, FFF - Fused Filament Fabrication, FFD - Fused Filament Deposition, FDM - Fused Deposition Modeling. All of these are essentially the same.
The process is commonly referred to as FDM (Fused Deposition Modelling).
The following video by Loughborough University clearly demonstrates the working of this type of 3D printing.
Materials
ABS - Durable, Impact Resistant
PLA - Easy to Print
NYLON - Strong, Flexible, Durable
PET - Flexible, Durable
PVA - Water Soluble, Biodegradable, Oil Resistance
HIPS - Dissolves, Biodegradable
PC - Strong, Flexible, Durable, Transparent, Heat Resistant
PP - Flexible, Chemical Resistance
ACRYLIC - Rigid, Durable, Transparent, Impact Resistant
TPC - Extremely Flexible
PC ABS - Rigid, Durable, Impact Resistant, Resilient, Deflecting Heat
TPU - Extremely Flexible
2. Vat Photo-Polymerization
A Vat is simply a tank used to store liquid. A Photo-polymer is a liquid that hardens when exposed to light. This type of 3D printing focuses a laser light on the surface of a photo-polymer stored in a vat. The area exposed to the laser hardens. After every layer, a new layer of liquid is exposed to laser. When this process continues, an object in the desired shape is achieved. The process is commonly referred to as SLA (Stereo-lithography) and was the first type of 3D printing introduced.
There are 4 sub-types of this technology: Laser Stereo-lithography (SLA), Projection SLA, Micro SLA, and Two-photon SLA.
The following video by Loughborough University clearly demonstrates the working of this type of 3D printing.
Materials
Photo-curable Resins liquids- The exact compositions are dependent on the manufacturer. Additives are added in the composition to simulate properties of engineering materials. For example, some resins might be very rigid while others can be extremely flexible.
3. Powder Bed Fusion
As the name suggests, this type of 3D printing uses powder as material. The powder can be plastic and even metal. Like all 3D printing processes, this is also a layer-by-layer process. Laser is focused at different points on a layer of powder. The extensive heat energy from the laser melts the powder particles which then stick together. This is similar to the welding process. After every layer, a new layer of powder is spread evenly and the process continues.
There are mainly two types of Powder Bed Fusion 3D printing processes differentiated by the material they use: SLS (Selective Laser Sintering) for plastics and SLM (Selective Laser Melting) for metals.
Visuals are a better way to understand so watch the video from Loughborough University demonstrating this 3D printing process.
Materials
Metals
Stainless Steel
Aluminium Alloys
Cobalt Chrome
Titanium Alloy
Nickel Alloy
Polymers
Nylon
PEEK
Polystyrene
4. Material Jetting
This 3D printing type works exactly like the inkjet printer which most of us have owned at some point. Just like ink, material is deposited in drops on a surface. After every layer, UV light is used to cure the material ( a chemical reaction initiated by light is termed UV curing). Curing solidifies and hardens the material. However, unlike your inkjet printer, this process is repeated for multiple layers to create a 3D object. It is somewhat similar to repeatedly printing on a sheet of paper using your normal 2D printer.
Watch the video from Stratasys explaining their Poly Jet material jetting 3D printing technology!
Materials
Polymers and waxes are suitable and commonly used materials for Material Jetting. A few examples are : Polypropylene, HDPE, PS, PMMA, PC, ABS, HIPS, EDP
5. Binder Jetting
Instead of depositing material directly as explained for the ‘Material Jetting’ type, a binder (an adhesive liquid) is jetted (deposited in droplets) on the surface of a powder material. Being an adhesive, the binder droplets make the powder particles stick to each other. After one layer, a fresh layer of powder is uniformly spread over the previous layer. Binder is deposited again and the process continues until the final 3D object is formed.
Materials
Metals: Stainless steel
Polymers: ABS, PA, PC
Ceramics: Glass
6. Directed Energy Deposition
The process very similar to Material Extrusion in principle: melted material is deposited through a nozzle. However, here the nozzle is mounted on a arm that can freely move in 5 axis. Moreover, laser is used to generate heat to melt the material (electron beam or plasma arc is used in some cases). It is best suited for metals.
Watch the video to better visualize how the process works!
7. Sheet Lamination
The process is simply putting one sheet over another to form a stack. After every layer, the required shape is cut (mostly using CNC methods). Repeating this process forms a 3D object. The two types are: ultrasonic additive manufacturing (UAM) and laminated object manufacturing (LOM). UAM using ultrasonic welding to join the layer of sheet. LOM uses adhesive to do the same. Almost all materials including plastic, paper, metal sheets etc. can be used.