# 3D Printing

## Summary


3D printing is an additive manufacturing technology. It creates three dimensional objects using Computer Aided Design software. A 3D printer or fabricator replicates geometric models in the real world by adding materials layer by layer. 

3D printing technology is disrupting traditional manufacturing. Manufacturers today are increasingly adopting 3D printing in their processes. With widening range of printable materials available, more companies are following suit. Because 3D printing allows model testing before producing the actual products. Since it adds materials in layers, it can generate intricate interior designs with high precision. It can also produce rapid prototypes in short periods. .

The technology creates an end product as a single piece in quick time instead of assembling composite items. As it's evolving at a rapid pace, 3D printers are expected to become products for home users like the 2D printers.

## Discussion

### How does 3D printing compare against other manufacturing techniques?

Two age-old manufacturing techniques are formative and subtractive. With **formative manufacturing**, we start with a cast or mould and pour material into it. This is cost-effective for high-volume production but requires a stable design. With **subtractive manufacturing (SM)**, we start with a block of material. With the aid of CAD software, we remove excess material via drilling, cutting, and CNC milling. Complex objects can be created. Design changes are possible in software. However, it has high wastage of material.  

**Additive manufacturing (AM)** creates an object by adding material to it one layer at a time. This results in less wastage of material. It's flexible since design changes are done in software. It's ideal for prototyping and rapid customization. It can create certain features not possible with SM. 

In everyday talk, 3D printing is a term synonymous with AM. AM is often used in industrial settings and refers to the process. 3D printing is often used by hobbyists and refers to the technology.  3D printing may be seen as a type of AM since AM encompasses a broader spectrum of processes. 


### What are the basic steps involved in 3D printing?

3D printing broadly involves three steps: Modeling, Printing and Finishing. 

Models are generated using Computer Aided Design software. A designer forms shapes by scanning real objects in 3D form and feeds them into the *CAD* software. She connects the shapes meaningfully, makes corrections and creates models in an iterative process. The models are finalized and stored in file formats such as Stereolithography (STL) file and Additive Manufacturing File (AMF). 

Before printing the final model, files are checked for errors. . The clean files are processed by another software called *Slicer*. The slicer converts a geometric model into an array of thin layers. The layered output of the slicer is stored in *G-code* files that interact with the client software. G-code files serve as interfaces to pass printing instructions to the 3D printers. 

In the last stage, the printed object is given a finishing touch to make it a complete product. The rough surfaces are removed, cleaned, polished, and/or coated, depending on the type of the product printed. 


### Could you give some examples of 3D printing process types?

**Stereolithography (SLA)** is one of the first 3D printing types in the industry. The process exposes liquid material to a laser source and forms rigid solid parts layer by layer. It's called photopolymerization. The solid parts are treated further with UV rays to fully solidify their outer surfaces. 

**Fused Deposition Modeling (FDM)** is a type suitable to print plastic objects. An extruder forcefully ejects plastic filaments heated to their melting points. Filaments deposit on a platform layer by layer. These layers consolidate to become 3D objects. 

**Powdered Bed Fusion (PBF)** is another process where laser beams are directed on powders loaded on designated plates. The powders melt and form solid shapes. Each solid that forms in the next layer blends with the previous layer till the whole model is printed. *Selective Laser Sintering (SLS)*, *Electron Beam Melting (EBM)* and *Selective Heat Sintering (SHS)* are the basic technologies associated with Powdered Bed Fusion. 

Some other types are *Digital Light Processing (DLP)*, *Material Jetting (MJ)*, *Laminated Object Manufacturing (LOM)*, *Binder Jetting (BJ)* and *Direct Energy Deposition (DED)*. 


### How does one choose a 3D printing process?

Multiple factors may influence the choice of a 3D printing process. Geometric precision, materials used, product appearance, economy and size are some important considerations. .

For example, when the materials used are carbon, Nylon, Carbon fibre and the like, FDM would be suitable. It is cost effective and prints products composite of a variety of items. SLA makes the best fit for clean surface finishing and fine detailing. To produce brittle, multi-colored outputs, designers choose Material Jetting (MJ). Binder Jetting (BJ) that uses liquid agents to bind powder beds is preferred to 3D print metal objects in large volumes. 


### Can you discuss some applications of 3D printing?

**Consumer Products**: 3D printing technology can create custom made products. A broad classification of some common consumer products may include jewelry and fashion accessories, consumer electronics, entertainment props and set pieces, sporting goods, and packaging prototypes. 

**Architecture and Construction**: 3D printing technology can be applied to construct an entire building or build components of it. Apis Cor Printed House in Russia and Canal House in Amsterdam are 3D printed structures. 

**Spare Parts Manufacturing**: Vital parts of obsolete products may become unavailable or hard to find. And they may force us to buy new products. 3D printing of such parts saves money and time. 

Other major industries benefiting from 3D printing technology include prosthetics and bio implants, dentistry, pharmaceuticals, automotive, food, aerospace, robotics, and medical and functional textiles. 


### How could digital twin technologies support 3D printing?

A digital twin is the virtual representation of an object or a process in a real-time simulation environment. Digital twins facilitate interaction between humans, objects and the virtual spaces connecting them. They make use of Internet of Things (IOT), Artificial Intelligence (AI), cloud computing, Simulation and Modeling, Extended Realities and Networks to function effectively. 

Coupling Digital twin technology with 3D printing can enhance performance monitoring and assist in detecting anomalies. The combination of Digital twin and 3D printing offers some advantages:

    + It enables simulations to take temperature and humidity differences which a mere CAD software cannot.
    + Its database allows comparison of designs for future references.
    + Designers can use digital twin systems to verify designs and performance data virtually.
    + Cloud manufacturing environment in the digital twin technology enables real-time data monitoring and troubleshooting.
    + Simulation and early warning systems using digital twin systems can minimize errors and distortions in the final output.
    + It provides reference solutions for other manufacturing equipment online.
    + It enables detection of defects and quality lags during simulation before actual printing. Hence it saves resources and costs.

### What are some of the current challenges of 3d printing technology?

**Material unavailability**: There is no one-size-fits-all solution to printing every product. Some materials may not be available for 3D printing. 

**Material incompatibility**: Some materials may not be compatible with the printers. Not all materials fit into the design when they require temperature control. 

**Lack of Industry standards**: 3D printing across the world lacks standards that are widely accepted or commonly followed. Standards should be in place to create a comprehensive ecosystem of manufacturers, suppliers and users. 

**Post-processing issues**: Most of the 3D printed products need post-processing to become usable. It adds to the costs, consumes extra time and kills consistency. 

**Inconsistencies in output**: A 3D printer may not produce the exact output across all geographies. Depending on the atmospheric conditions, physical dimensions such as height, width and depth may show variances. 

**Scalability issues**: At present, 3D printing may not offer cost effective solutions to mass production in certain fields. For example, biomedical industry. 

## Milestones

1981

Japanese professor Dr. Hideo Kodoma invents Laser beam resin curing system, the first 3D printing system that uses UV rays to harden polymers. 

1983

Charles Hull files patent for the first stereolithography apparatus machine. 

1986

Charles Hull is granted patent for SLA. He co-founds 3D-systems corporation, the first company to introduce SLA 3D printing. 

1987

The first commercial rapid prototyping printer, SLA-1, is released. 

1989

Scot and Lisa Crump apply for a patent for Fusion Deposition Modeling (FDM). Hans Langer establishes EOS GmbH in Germany. EOS (Electro Optical Systems) later becomes an industry leader in 3D printing of metals and plastics. 

1997

Aeromat introduces 3D printer for metals using Laser Additive Manufacturing (LAM) technique. The printer uses high energy lasers to fuse powdered titanium alloys. 

1999

Wake Forest institute of Regenerative Surgery devises the first 3D printer to build a synthetic biodegradable 3D scaffold of human bladder. 

2005

Adrian Bowyer developed an open source concept called ReRap to create self replicating 3D printers. 

2007

The first 3D printer to be commercially available, Darwin, built on RepRap concept is built. When Scott Crumps' patent on FDM expired in 2009, many low cost FDM printers flooded the 3D printer market. Of them, RepRap or the Replicating Rapid Prototyper is significant. It is an open source machine that can copy itself and replicate its own intricate parts. It also produces prototypes rapidly. Since it is an open source, many companies use RepRap designs to print 3D machines and products. It brought down 3D printing costs considerably. 

2009

MakerBot introduces do-it-yourself kits for people to build their own 3D printers and builds Thingiverse file library where one can submit and download 3D printable files. 

2010

Kor Ecologic unveils a prototype car with a 3D printed body. 

2011

University of Southampton designs and prints the first unmanned 3D printed aircraft called Southampton University Laser Sintered Aircraft (SULSA). 

2017

Celink, a Swedish Company, commercializes standardized bio-inks that can be used to print tissue cartilage. The company later introduces the INKREDIBLE 3D printer for bioprinting services