3D printing

For methods of transferring an image onto a 3D surface, see Pad printing. For methods of generating autostereoscopic lenticular images, see Lenticular printing and Holography.

3D printing, also called additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in many different ways. Material is placed, joined, or hardened under computer control. The object is built up bit by bit, usually one layer at a time. The material can be plastic, liquid, or tiny grains of powder that are fused together.

In the 1980s, 3D printing techniques were only good for making test models and display pieces. At that time, people often called it rapid prototyping. By 2019, 3D printing had become precise, reliable, and able to use many more materials. Some methods were then useful for making products in factories. In this setting, the term additive manufacturing can be used instead of 3D printing.

One of the main benefits of 3D printing is that it can make very complex shapes that would be too hard to build by hand. These include hollow parts or parts with inner truss structures. These shapes weigh less and create less wasted material.

Fused deposition modeling (FDM) uses a continuous strand of thermoplastic material. As of 2020, it was the most common 3D printing method.

Terminology

The umbrella term additive manufacturing (AM) became popular in the 2000s. It is based on the idea of building material up together in any of various ways. Later, the term subtractive manufacturing was used as a retronym for the large group of machining processes, which cut material away. At first, many people used 3D printing only for plastic-based methods, while AM was used more for metal work and for making final parts.

By the early 2010s, 3D printing and additive manufacturing had both come to mean a wider range of meanings as umbrella terms for adding material. Popular media and hobby makers used 3D printing, while industry and standards groups used additive manufacturing. Today the two terms are still often used to mean the same thing, but some experts say additive manufacturing includes 3D printing plus other technologies and parts of a manufacturing process. The American National Standards Institute says additive manufacturing means building parts layer by layer from 3D model data. It says 3D printing means putting down material through a print head or a similar nozzle.

History

The idea of 3D printing first appeared in science fiction. Murray Leinster wrote about it in a 1945 story. In 1974, David E. H. Jones explained the idea in a science column. In 1971, Johannes F Gottwald received a patent for a "Liquid Metal Recorder," which may be the first patent to describe 3D printing. Early machines were made in the 1980s. Chuck Hull created stereolithography, a way of building objects in layers. His company, 3D Systems, released the first commercial 3D printer. In 1988, S. Scott Crump developed fused deposition modelling, which is now the most common method. His company, Stratasys, sold its first machine of this kind in 1992.

During the 1990s and 2000s, 3D printers were expensive and were mostly used by industry and researchers. In 2004, Adrian Bowyer designed plans for a printer that could make many of its own parts. This project was called RepRap. Open-source projects like this helped more people use the technology. By the 2010s, companies in fields like aviation began using 3D printing to make parts. In the 2020s, printers became cheap enough for most people to buy. Researchers have also used 3D printing to make things like a prosthetic eye and a full-face prosthesis for a patient in the UK.

Benefits of 3D printing

3D printing, also called additive manufacturing, has become more important in engineering. It offers design freedom, custom products, and ways to make things that were hard to make before. Some benefits include faster prototyping, lower manufacturing costs, more product customization, and better product quality. People also use 3D printing for prosthetics, food, rocket building, art, and renewable energy systems, including battery energy storage.

3D printing can make complex shapes with high precision and accuracy. It adds material only where it is needed, instead of cutting away extra material, so it makes less waste. This can lower material costs and help the environment. It can also help create a smaller carbon footprint.

General principles

Main article: 3D modeling

A 3D printable model can be made with computer-aided design (CAD) software, with a 3D scanner, or with a regular digital camera and photogrammetry software. Models made with CAD usually have fewer mistakes, and mistakes can be found and fixed before printing. CAD models can be saved in the stereolithography file format (STL), a common file format for additive manufacturing. An STL file describes a shape's surface with many small triangles. STL files can become very large for complicated parts, so a newer format, the additive manufacturing file format (AMF), was introduced in 2011 to solve this problem. Before printing, an STL file must be checked for mistakes, such as holes. Models made by 3D scanning often have more of these mistakes, and 3D reconstruction often has mistakes too.

Next, a program called a "slicer" cuts the model into thin layers. It creates a G-code file with instructions for a specific printer, such as FDM printers. Printer detail is measured in dots per inch (dpi) or micrometers (μm). Layers are often about 100 μm thick, and the detail is similar to that of laser printers. Building a model can take several hours to several days, though some machines can make it faster, in a few hours.

Printed parts can be improved after printing. Sanding and bead blasting can make surfaces smoother, and some plastics, such as acrylonitrile butadiene styrene (ABS), can be smoothed with acetone. Annealing, a heating process, can make parts stronger in ways such as fracture toughness, flexural strength, impact resistance, and heat resistance. Parts that must work very well, called mission critical, may also be treated with hot isostatic pressing to improve their density and microstructure. Some methods also use machining to remove material, and painted parts are first primed. Support structures can be dissolved if they are made of PVA.

Printing once focused mainly on polymers, but it now includes metals, chocolate, and ceramics.

The most common polymers for personal 3D printers are polylactic acid (PLA) and PETG. A newer process for GMAW 3D printing can remove aluminium or steel from the base surface.

Many printers can only print one material at a time. Multi-material 3D printing allows one printer to make objects with different materials. Each voxel, which is a 3D printing pixel, can have its own material set.

Main article: Multi-material 3D printing

Main article: 4D printing

Some 3D printed objects can change shape over time, with temperature, or with another kind of stimulus. This is called 4D printing.

Processes

Applications

Main article: Applications of 3D printing

3D printing, also called additive manufacturing, is used in factories, medicine, industry, and cultural heritage work. It first helped in toolroom work. Rapid prototyping made it faster and cheaper to build test versions of new parts. Before this, those parts needed CNC cutting and grinding. In the 2010s, printing moved into production on a much larger scale. Scientists are developing additive manufacturing of food. NASA is studying it to reduce food waste and to help feed astronauts. In 2018, Italian bioengineer Giuseppe Scionti used a custom 3D bioprinter to make plant-based food that looks like meat. Fashion designers have tried printed bikinis, shoes, and dresses. Nike and New Balance have also used printing to make shoes.

In motor vehicles and aircraft, printing is changing how some parts are made. These include unibody, fuselage, and powertrain parts. General Electric uses printers to build turbines parts. GE Aviation used design for additive manufacturing to make a helicopter engine with 16 parts instead of 900. This could help simplify supply chains. Other examples include the sports car from Koenigsegg, the car Urbee, the vehicle from Local Motors, and the Airbus A350 XWB, which has over 1000 printed components.

Printing also appears in many other areas. In 2012, Defense Distributed planned to share a plastic 3D-printed firearm design. This raised questions about gun control and do-it-yourself firearms. Since the mid-1990s, surgeons have used 3D printing to plan bone surgery. They also make custom implants that use osseointegration. Biotechnology companies have studied 3D bio-printing to build tissues from living cells, using inkjet printing. It has also been considered for placing stem cells in people. During the COVID-19 pandemic, volunteers printed frames for face shields to help supply PPE. Schools use printers for STEM learning, along with open hardware designs for open-source labs.

Museums in the cultural heritage field have printed missing pieces of relics. These include pieces from Tiwanaku in Bolivia. The Metropolitan Museum of Art and the British Museum have made souvenirs. The Threeding platform shares digital models of artifacts made with Artec 3D scanners. Artist Morehshin Allahyari has recreated cultural treasures that were destroyed in 2014. Architects have modelled the Iran National Bank using Cinema4D. The first 3D-printed steel bridge was unveiled in Amsterdam, over the Oudezijds Achterburgwal canal. Printed soft actuators can be made as one piece, without external joints, adhesives, or fasteners. Hobbyists print items like gears. DIY, maker, early adopter, and hacker communities have helped make printers more affordable.

Legal aspects

See also: Open-source hardware

3D printing has been used for decades in some factories, where patents, industrial design rights, copyrights, and trademarks may apply. There are not many jurisprudence cases yet that show how these laws will work if 3D printers become common. Designs and printed items may be protected. Using them may require asking the owner for a licence, which may have conditions and a cost. Many laws allow private, non-commercial use, which may not need these permissions. A patent usually lasts about 20 years from the date it is applied for. Copyright often lasts for the author's life plus 70 years. Some uses may fall under a fair use exception.

Main article: 3D printed firearms

The US Department of Homeland Security and the Joint Regional Intelligence Center warned that 3D printed guns may be a risk to public safety. They also said that it would be hard to control online sharing of gun plans. Even after the US government had the plans taken down, they were still widely shared on the Pirate Bay. Efforts to limit this sharing have been compared to the spread of DeCSS, which made DVD ripping possible. Some people think rules on 3D printers would be hard to enforce. Professor Hod Lipson suggested that gunpowder could be controlled instead. Europol noted that criminals have other ways to get weapons, but that the risks may grow as technology improves. In the United States, the FAA regulates aircraft parts made with 3D printing. In December 2016, it approved a 3D-printed fuel nozzle for the GE LEAP engine. New quality standards for 3D printing were issued in 2021 and 2023.

Health and safety

Main article: Health and safety hazards of 3D printing

See also: Health and safety hazards of nanomaterials

Some plastics can give off tiny particles and gases called ultrafine particles and volatile organic compounds (VOCs) when they get hot. These have been linked to problems with the respiratory and cardiovascular systems, which are the parts of the body that help us breathe and keep our blood moving. The nozzle of an FFF printer can get as hot as 190 °C to 260 °C, which can burn the skin. Some printers, called vat photopolymerization stereolithography printers, use strong lasers that can hurt skin and eyes. These are considered safe while printing because the laser stays inside the printing chamber.

Printers have many moving parts, such as stepper motors, pulleys, and small fans. These are usually not strong enough to cause serious injury, but they can still catch a finger, long hair, or loose clothing. Scientists are still studying these safety concerns, because 3D printers have only recently become common. In 2017, the European Agency for Safety and Health at Work published a paper about the risks and how to control them. Home printers can be quite different in how loud they are. Loudness is measured in decibels (dB), and home printers range from 15 dB to 75 dB. Fans, motors, and bearings are the main sources of noise. To make a printer quieter, people can add vibration isolation, use larger fans, keep the printer well maintained and lubricated, or use a soundproofing enclosure.

Impact

Additive manufacturing, from its early days, asks companies to be flexible and ever-improving users of all available technologies so they can stay competitive. Supporters of additive manufacturing think it will work against globalization, because people could make many of their own products instead of buying them from others. In practice, the newer methods mostly work alongside traditional methods rather than replacing them. The futurologist Jeremy Rifkin said that 3D printing is the start of a third industrial revolution. The first big change came from the production line, which dominated factories from the late 1800s.

Some people link commons-based peer production with 3D printing, as a way to make products that are more personal and sustainable. Others warn of problems, such as making weapons more easily and copying products illegally. Larry Summers wrote that new technologies could have very harmful effects on people who do routine jobs. Michael Spence wrote that digital technology is taking over work, including in factories, where robots and 3D printing are replacing workers. He pointed to disintermediation as part of this change. Naomi Wu sees 3D printing as the next desktop publishing revolution. In 2024, a printer was given to the Juan Fernandez Women's Group, so women in the remote community could make parts to repair broken equipment.

On the environment, additive manufacturing builds products layer by layer. Traditional CNC milling cuts material away, but this method creates less waste. A Life-cycle assessment estimated that it could lower carbon dioxide emissions by making products closer to where they are used. It can also support lightweighting, which may reduce greenhouse gas emissions from vehicles. However, the method uses a lot of energy. Some highly regulated aerospace industries insist on new powder, which makes recycling hard. Additive manufacturing has not yet reached its material efficiency potential of 97%. Some printers can melt recycled high-density polyethylene (HDPE), an idea explored by the RecycleBot.