3D Printing (also called additive manufacturing) refers to a number of techniques and processes used to create a three-dimensional object.
These objects can be of a huge range of shapes, sizes and geometry types, and are controlled by a computer that is fed 3D object data in what is termed as an AMF or Additive Manufacturing File.
Unlike the traditional machining processes where material is removed from a stock, 3D printing or AM builds a three-dimensional object layer by layer using the information fed to it via a computer-aided design (CAD) or AMF file.
Originally, the process known as 3D printing involved depositing a binder material layer by layer onto a powder bed using inkjet printer heads. It was associated with polymer or plastic technologies, whereas additive manufacturing or AM was used for metalwork and other such production contexts.
‘Additive manufacturing’ emerged as an umbrella term in the early 2000s, while ‘3D printing’ gained traction among the masses due to its use by consumer-oriented producers.
Lower-end machines (either in terms of capability or price) have been historically associated with it, and AM is the preferred term in formal or industrial manufacture, due to the basic nature of the process: sequential layer addition to create a 3D object under computer control.
The earliest additive manufacturing technologies, materials, and equipment were developed in Japan in 1981.
Hideo Kodama invented a method for fabricating three-dimensional models using a light and temperature-sensitive polymer with the area of exposure being controlled by a mask pattern to give the object proper shape.
In 1986, Chuck Hull of 3D Systems in the USA patented his process of stereo lithography, which is a type of 3D printing technology that uses light-sensitive (photopolymerisation).
His technology is used even today for digital slicing of CAD models and infill strategies to construct the physical object.
He is also the mastermind behind the STL (Stereolithography) file format in printers that use the photopolymerisation technique.
In 1988, S. Scott Crump of Stratasys developed the plastic extrusion technique of fused deposition modelling (FDM), and the first machine to employ this method was available for sale in 1992.
3D printing in the sense of powder beds being shaped by polymers was first invented at the Massachusetts Institute of Technology in the USA and commercialised by the products of Z Corporation in 1993.
In the same year, Solidscape introduced a high-precision polymer jet fabrication system with a ‘dot-on-dot’ system of soluble support structures for the model being printed.
In this period, AM for metal structures was done through automation, but using (as they came to be called in recent times) subtractive or non-additive methods such as sintering, casting, fabrication, melting.
These were known by their own names, such as direct metal laser sintering, or selective laser melting).
The concept of a tool head moving to generate a shape layer as per one’s desire was associated in the metalwork industry with processes that removed metal rather than used it.
By the mid 1990s, this was being challenged through developments at educational institutes in the USA such as Stanford University and Carnegie Mellon University where engineering techniques like micro casting and spraying were being developed.
Sacrificial or support materials were also becoming more common, thereby enabling the design of new, complex kinds of geometry.
However, it was in the 2010s that such metal casting was done. Car parts like engine brackets and large nuts were created though additive manufacturing rather than being machined from stock, and major manufacturers like the Swedish company Koenigsegg have used 3D printed parts in their cars (notably the Koenigsegg One:1, a supercar).
3D printing is also used extensively in the medical field for producing custom casts and prosthetics.
3D models for printing may be made using computer aided design, or by 3D scanning.
The advantage that CAD has is that the modeller has complete control over the output and models can be made with a very high degree of accuracy.
Further, if there are any errors of intersection, face normal, or noise shells causing problems when the models is sliced for printing, they can be easily adjusted.
On the other hand, 3D scanning collects digital data on the shape of an existing object and renders a digital model based on that data.
As 3D scanning is dependent on point-to-point data collected by the camera, these errors are more likely to occur when reconstructed in a digital geometry.
After the model is complete, the data is converted to the STL file format, and then digitally sliced the model into ultra-thin layers in a G-code file, using which the printer does its work.
Printers are available in different resolutions, and this factor defines printing ability and price of the machine.
Typical layer thickness is around 100µm (around 250 dots per inch), with some printers capable of printing 16µm (about 1600 dots per inch). XY resolution is comparable to that of laser printers, with an average range of 100-300 DPI.
In three dimensions, the 3D particles of the objects are typically 50-100µm (510-250 dots per inch) in diameter.
Construction of a model can take anywhere between a few minutes to several days, depending on the size and complexity of the object being printed, the type of machine used, and the number of models being printed simultaneously.
The most significant advantage that additive manufacturing holds over traditional engineering methods like injection moulding is the reduction in the time taken to produce a finished product.
Recently, MAAC Chowringhee, Kankurgachi, Rashbehari had organized a seminar for students on 3D printing.
It was an interesting and educational experience, and the students got to see a small model of (?) being printed during the session.
An FDM type printer was used, and the speaker explained that these are more common due to the versatility of thermopolymers, which is the material used in most lower and mid-range printers: they can be shaped easily through the use of heat and the printer head can produce models of great precision and complexity.
The students were also shown other models that the speaker’s company had made, along with a presentation highlighting the different applications of 3D printing.
In addition to engineering, scientific and medical applications, they are also used for previewing conceptual prototypes before actual production, as it is less expensive than producing a product directly.
The bottom line: 3D printing is the future of design, and there great potential for development.