Additive Manufacturing processes

 What is Additive Manufacturing?

As the name suggests, Additive Manufacturing (also known as 3D printing) is a group of manufacturing techniques, which manufacture parts by adding successive layers of material with the help of computer control systems. Various materials that can be used in additive manufacturing (AM) are plastic, metal, concrete, also human tissue.

In the additive manufacturing process, Computer-Aided Design (CAD) is created and utilized to manufacture 3-Dimension (3D) objects. Various CAD-CAM software is required to Design, Analyze, and Manufacture parts. Once CAD data is produced, Slicing software slices the design in different layers (as required by different  AM processes), and then data utilized to manufacture required material parts.

Different terms like “3D printing” and “rapid prototyping” are also casually used to describe Additive manufacturing, but each one is a subset of additive manufacturing.

Hence in the simple sense, Additive manufacturing technology is the opposite to Subtractive manufacturing technology. Instead of material removal, the material is added in a properly controlled way to get the desired object. 

Types of Additive Manufacturing processes:

Officially, as per the International Organization for Standardization (ISO/ASTM 52900), Additive manufacturing can be categorized into 7 different types.

Fig: Additive Manufacturing Family chart

1. VAT polymerization

2. Powder Bed Fusion

3. Binder Jetting

4. Material Jetting

5. Sheet Lamination

6. Material Extrusion

7. Directed Energy Deposition

1. VAT polymerization

VAT polymerization is the oldest method of Additive manufacturing.  The process is based on hardening the photopolymers on exposed to ultraviolet light. VAT polymerization uses a  VAT liquid of photopolymer resin, out of which the CAD model is created layer by layer. At first, the resin is in the liquid phase and with the help of ultraviolet (UV) light, the resin is cured or hardened as required. At the end of one layer, supporting a platform moves upward or downward directions.

Fig: SLA and DLP techniques

Stereolithographic Apparatus (SLA), Digital Light Processing (DLP), and Continuous Liquid Interface Production (CLIQ) are the most common types of VAT polymerization techniques. 

2. Powder Bed Fusion

Powder Bed Fusion (PBF) methods use some thermal heat source (either laser or electron beam) to melt and fuse the material powder layer by layer. In this Additive Manufacturing method, the 3D Object layer is created using fine powder as a print medium. This powder is sintered or melted using a selective heat source. 

All Powder Bed Fusion method involves the spreading of powder material over the previous layer, using some suitable mechanisms like a roller or blade. Spreading with decided based on required layer height in the model. 

Fig: Metal printing using SLS

Powder Bed Fusion includes the following commonly used methods: Selective Laser Sintering (SLS), Selective Heat Sintering (SHS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), and Electron Beam Melting (EBM). It is a wildly use metal additive manufacturing method. Plastic and metal parts - both can be manufactured using differently suitable Powder Bed Fusion methods.

3. Binder Jetting

Binder Jetting is a category of additive manufacturing (AM) process that uses a liquid binding agent deposited into a build platform to bond layers of powder material and form a part.

In biner jetting, a binder is selectively deposited on the powder bed, bonding these are together to form a single solid part layer. Commonly used binder jetting materials are sand, metals, and ceramics that come in a  powder form. After printing the part, sintering is required.

Fig: Color printed binder jet object using sand

High-resolution metal parts are advantages of binder jetting. Binder Jetting technique used in many industrial applications like dental and medical devices, part casting, aerospace devices, luxury applications, and more. 

4. Material Jetting

5. Sheet Lamination

6. Material Extrusion

7. Directed Energy Deposition