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3D Printing - An Overview

What is 3D Printing?

3D Printing has revolutionized and democratized manufacturing. From complex designs, bioprinting human tissues, affordable housing to on-demand manufacturing, the technology is at forefront of defining the potential of collaboration for the human race.

3D printing or additive manufacturing is a process of making three dimensional solid objects from a Computer-Aided Design (CAD) digital file. It started out in the 1980s as a tool for rapid prototyping but has evolved over time to have multiple applications such as in bioprinting of live tissues, accelerating affordable housing, creation of custom prosthetics and decentralized manufacturing of critical and complex components for various industries. This has become possible due to increased precision and availability of a range of materials such as metals, ceramics and various polymers that can be used in the printing process.

How is a 3D object created?

The creation of a 3D printed object is achieved using additive processes in which material is deposited, joined or solidified using various techniques.  The object is created by laying down successive layers of material under automated control and then solidifying or curing it into the required shape using energy sources such as UV light, plasma arcs and heat. Each of these layers can be seen as a thinly sliced horizontal cross-section of the eventual object.

The process starts by creating a 3D model and then using slicing software to slice it into layers and individual 'voxels' to be fed into the 3D printer. 

The required 3D model can be created using CAD or by using a simple phone camera and photogrammetry techniques with the former having greater precision. Real-life objects can also be modelled using 3D scanners and then corrected for errors such as holes, noises or intersections using CAD software for greater accuracy. 

Not all 3D printers however use the same technology. There are several ways to print and all those available are additive, differing mainly in the way layers are built to create the final object. Some methods use melting or softening material to produce the layers. 

Processes of 3D Printing

The American Society for Testing and Materials classify the 3D printing process into the following 7 categories: 

1. VAT Polymerization

The process involves solidifying a photopolymer resin using an ultraviolet (UV) light source. The following 3 methods employ vat polymerization:

  • Stereolithography (SLA): This method cures photopolymer resin one layer at a time using UV light and galvanometers. The process is repeated on successive layers my moving point to point on the surface of the polymer and fusing it together. The process often requires support structures. 

  • Digital Light Processing (DLP): Similar to stereolithography - DLP is the sister technology and uses arc lamps instead of UV lasers and exposes the surface all at once. This key difference makes it faster compared to stereolithography. Its performance is limited by the quality of the lamp and the curved surfaces of the print are often a little boxy but can be smoothed out by sanding. 

  • Continuous Liquid Interface Production (CLIP): The process is based on the Digital Liquid Synthesis technology that uses oxygen-permeable optics and heat programmable materials that have higher Young's Modulus and are truly isotropic. The products so formed are engineering grade and not as brittle as other polymerization methods. The heart of the process is a "dead zone" which allows curing of material only above it and allows maintaining a continuous liquid interface avoid the peeling process which is inherent in many resin-based printers. 

2. Material Jetting

In this process, the material is applied through a nozzle similar to inkjet print heads onto a platform and later hardened by UV light. 

3. Binder Jetting

The process uses powder base material and liquid binder which is applied to the powder using a nozzle thus glueing it into the required shape. The powder base material which has not been bound can be used again to print. 

4. Material Extrusion

The process is also referred to as Fused Deposition Modelling where a plastic filament is passed through a heated nozzle and extruded into the desired shape using a controlled mechanism. The nozzle can move in 3d space and is not limited to manufacturing by layering. 

5. Power Bed Fusion

The technique is similar to binder jetting and uses a powder-based material with small variations in methods of curing such as :

  • Selective Layer Sintering (SLS) - The powder material is fused together using a laser and successively lowered into the powder to allow curing of the material above. 

  • Multi Jet Fusion (MJF) - This method was developed by Hewlett Packard and used multiple inkjets that fuse the material selectively. The object is then heated causing agents to react creating isotropic and rigid products. 

  • Direct Metal Laser Sintering -  The method uses a metal powder instead and the process is similar to SLS. 

6. Sheet Lamination

The sheets of materials such as metals, paper or polymer are welded together using ultrasonic waves and then milled into proper shape using CNC machines. 

7. Directed Energy Deposition

The process used a multi-axial robotic nozzle that deposits metal powder or wire onto the surface which is then exposed to an energy source such as plasma arc or laser beams to melt and then solidify into the desired shape. 

Applications of 3D Printing

Low Volume Production

3D Printing has lots of applications for various industries. It is specifically beneficial for industries where complex parts are produced in low volume thereby reducing the need for investment in expensive tools thereby making it an ideal choice for original equipment manufacturers (OEMs) especially in the aerospace and defence industry. 

Lightweight Parts

3D printing also allows manufacturing hollow designs without compromising the structural integrity and therefore finds applications in the automotive and aerospace industries. Using lightweight parts helps in considerable fuel savings thereby reducing carbon emissions and pollution. 

Less Waste

Since 3D printing is based on additive manufacturing and produces objects layer by layer, it results in less wastage of material. The unused material can be used again and recycled easily.

Complex Consolidation

3D printing also allows the integration of various components into one functional unit thereby simplifying the manufacturing process. 

Maintainance and Repair:  3D printing processes such as Directed Energy Deposition help in the repair of high-end equipment in military and aerospace by adding material to broken or worn out parts. 

Electronics 3D Printing: Creating complex circuit boards and antennas is a new and upcoming use case that can accelerate product development and possibly bring innovation to the nanotech industry. 

Design Flexibility: Testing and making quick design changes give designers the flexibility to innovate and modify parts in a fraction of time. 

Superior Medical Devices and Personal Healthcare: Patients can now have customised and specific medical devices such as prosthetics and implants

What is 4D Printing?

4D Printing is advanced 3D printing that uses programmable materials (such as hydrogels, cellulose composites) and designs that transform upon interaction with parameters such as temperature and humidity. It is also referred to as 'active origami' or 'shape morphing systems'. 

It can have possible applications in medicine, transportation and conductivity to name a few. 

Impact of 3D Printing

The following text highlights the macro-factors that have an influence on the future of 3D printing and how it impacts these macro-factors too: 

Political: Since 3D printing is an easily accessible and decentralized form of manufacturing, governments around the world would want to regulate its use.  3D printing can be used to make functional weapons without a need for a license and can be used by terrorists and insurgents to design undetectable weapons. 

It also concerns the unregulated use of the intellectual property to make functional products and governments would need to put legal limitations on the use of 3D printing in order to protect patents. 

Socio-Economic: 3D printing gives a push to the Do-It-Yourself culture and makes 'mass personalisation a reality. It will impact the manufacturing and distribution of small products impacting several industries leading to the loss of many traditional jobs at the same time creating newer opportunities for 3D designers. It will also impact relations in the wage-labour society as it de-skills labour reducing the bargaining power of the labour class. 

It will also bring down the cost of transportation and can have a significant positive impact on the environment by reducing the carbon footprint of production and will promote decentralization. 

It may also lead to erosion of social interactions and cohesion as mass ownership of 3D printers becomes a reality.