Editorial Feature

Additive Manufacturing: The Third Industrial Revolution

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"A once-shuttered warehouse is now a state-of-the-art lab where new workers are mastering the 3-D printing that has the potential to revolutionize the way we make almost everything."

These were the words of Barack Obama during his state of the union address of 2013, speaking about the National Additive Manufacturing Innovation Institute located in Youngstown, Ohio. According to CNN, those few words were perhaps the biggest public endorsement of this technology ever since its inception in the 1970s.  But what exactly is additive manufacturing?

Additive Manufacturing

Additive Manufacturing (AM) can be defined as the process of joining materials in order to make objects from 3D computer models, usually on a layer upon layer basis.

This is directly opposed to most traditional manufacturing methodologies, in which an object is created by removing material from a base block in order to obtain the final geometry.

Currently, there are a large number of technologies that employ this innovative method of manufacture. One of the main advantages of this process is its ability to develop extremely complex shapes directly from computer models. These methodologies can be classified by the way they deliver the raw material either in a liquid, a powder, or a solid.

Fused Deposition Modeling

The first of the technologies that are going to be reviewed in this article are those which use a liquid as raw material, starting with the Fused Deposition Modeling (FDM), which is perhaps the most famous of all available AM technologies.

Developed by Scott Crump in the late 1980s, this technology uses a thermoplastic filament which feeds a heated extrusion head. The movement of this head is controlled via a computer and it melts the filament 1°C above the melting temperature.

The head then traces an exact outline of the cross-section of the part in one layer and the material solidifies in one-tenth of a second. As the layer is finished, the extrusion head moves up a programmed distance and starts building the next layer.

Where support is needed, the machine deposits a support material which can be removed after the part is finished. This method allows minimum material wastage which is nontoxic and comes in different colors.

FDM machines can be used anywhere from a production facility, in order to develop functional parts or prototypes, to use by individuals in their homes use to print anything for themselves such as ornaments or cellphone cases, due to their dramatic reduction in price from $20,000 to only $1,000. FDM machines can even be used to print other printing machines, such as in the case of the RepRap project.

The RepRap Project

The RepRap project is a free and open-source piece of hardware that allows the user to build their own 3D printing machine.

Due to the fact that blueprints and computer models for the machine are free on the web, anybody with a RepRap printer can print another of these machines in order to give to a friend.

This community encourages their users to use their imagination and print anything they like. The response has been so positive that some users even started 3D printing their own cakes.

Stereolithography​

Stereolithography is another AM technology which is based on using liquid material in order to create an object. In this technique, a polymer resin in liquid state is solidified via a UV laser, generating one layer with the cross section of the geometry.

Once again, this layer is finished and another one is generated on top using the same procedure. One of the main advantages of using this technology is the quality of surface finish on the object.

Stereolithography can be used to generate components with the characteristics of a final product. This technology has been used in the past to develop custom implants for patients with data derived from X-ray computed tomography.

The Limitations of Using Liquid as a Raw Materials

Although these both Fused Deposition Modeling and Stereolithography​ can be used to generate complex functional parts, they share one major aesthetic disadvantage. They are both ineffective at developing colourful parts.

FDM filaments are comprised of only one colour and in order to add a second colour another filament must be used.  Stereolithography uses one type of resin as raw material which means that the end product is printed in one colour only. These limitations are overcome by another AM technology known as 3D printing.

3D Printing Technology

Unlike the technologies reviewed so far in this article, 3D printing use powder as a raw material. A layer of the material is spread in the top of a piston and an inkjet printing head projects droplets of a binder material into the powder bed in the place where the solidification is required according to a 3D model.

Image Credit: nikkytok/Shutterstock.com

After the layer is completed, the piston drops a preferred distance and a new layer is spread out and selectively glued. Once the part is completed a heat treatment is required to enhance the bonding of the glued powder and then the unbounded material is removed.

This process uses aluminum oxide and alumina-silica ceramic powders with a colloidal silicon carbide as bounding material. The use of a support material is unnecessary in 3D printing as the unbound powder of each layer remains to form a natural support during the layering process.

From Design to Engineering

Apart from the development of functional and colourful prototypes (and even dental implants), this technology moved one step beyond the discipline of design and into the world of engineering.

Finite Element Analysis (FEA) is a standard engineering tool which can be used simulate components in their working environment in order to analyse their response in terms of stress, deformation or other mechanical variables.

Usually, the results from FEA data results are shown in a model of the geometry ‘painted’ in a colour scale which represents the value being analysed. Using 3D printing, engineers can now show these results as physical models in order to better communicate their findings.

The First Ever 3D Printed Gun

It could be argued that most of the materials used in AM technologies have limited mechanical properties when compared to the metals used in the traditional manufacturing technologies. However, in 2013 the first ever ‘3D-printed’ gun was developed in ABS plastic using FDM.

The firearm, known as the ‘liberator’, was developed in the United States by Cody Wilson, founder of the group ‘Defense Distributed’. All the components of the gun were made of ABS except for the firing pin which was made of metal and was successfully discharged.

I 3D Printed a Gun | Mashable Docs

Printing Your Imagination

The Liberator shows the disruptive potential of 3D printing technology not only from a manufacturing or a technological aspect but also from a social one. It is now possible for virtually everybody to have their own desktop manufacturing facility in their own home.

In the final part of this series, metal 3D printing technologies will be reviewed, as well as other state of the art additive manufacturing technologies.

Sources and Further Reading

 

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