Three-dimensional printing or 3D printing is a modern technology for printing (manufacturing) of a three-dimensional solid object with any shape using a digital model. It is implemented as an additive process, applying successive layers of material so as to form the desired object. In this sense, three-dimensional printing is radically different from traditional techniques, in which material (eg cutting and turning) is usually taken to form the desired object.[1].

3D printing is based on digital technologies. The first working 3D printer was created in 1984  by Chuck Hull.[2] Since the beginning of the 21st century, there has been an increase in sales of these printers and a drop in their price.[3]

3D printing is used both in the production of prototypes and in regular production in the sectors architecture, construction, automotive industry, aircraft construction,  biotechnology, fashion, etc.

Thanks to open-source technology for FDM printing, amateurs and professionals create 3D printers working with all kinds of materials, such as chocolate, metal, even sand.

 

History

Terminology and methods

Файл:Hyperboloid Print.ogv

Video of the process of making a hyperboloid from molten polymer  with printer “Prusa Mendel”

CAD model used for 3D printing

The first equipment and materials for additive production (AP)  were developed in the 1980s.[5] In 1981, Hideo Kodama of the Nagoya Municipal Industrial Research Institute invented two methods for AP production of 3D plastic models using photo-hardening polymer and control of the area exposed to ultraviolet rays by imposing a template, or by scanning optical transmitter.[6][7] Then, in 1984, Chuck Hull of 3D Systems Corporation,[8] developed a prototype system, based on this process, known as stereolithography, in which the added layers of photopolymers are hardened by ultraviolet light lasers. Hull’s contribution is the design of the STL file format (STereoLithography), which is widely accepted by 3D printing software, as well as digital cutting and filling strategies widely used today in many processes. Initially, the term 3D printing refers to a process in which standard and simple inkjet printing heads were used. Today, the technology used by most 3D printers (especially models related to hobbies and user-centric ones) is material deposition modelling, a special application for extrusion of plastic.

AP processes for metal sintering or melting (such as selective laser sintering, direct laser metal sintering and selective laser melting) were usually known under their own names in the 1980s and 1990s. Almost all metalworking production at that time used the technologies of pouring, moulding, punching and machining; although there was a large dose of automation (such as robotic welding and CNC), the idea of a tool or working head moving along three-dimensional outlines of the object and transforming the workpiece from source material into the desired layer by layer shape, most people connected only to processes that removed metal (instead of adding it), such as CNC milling, CNC electro-erosion processing and much more. By the mid-1990s, new technologies for material deposition, including micropouring [11] and spraying materials, were developed at Stanford University and Carnegie Mellon University. [12]

The broad concept of additive production gained wider popularity in the first decade after 2000 [13], when the various additional processes are developing more and it becomes clear that very soon the removal of metal will not be the only metalworking process carried out under this type of control (tool or head moving along the three-dimensional contours of the workpiece, transforming the mass from the source material into the desired shape, layer by layer). It was during this decade that the term consuming production appeared as a retronym for a large group of machine processes, in which metal removal was their unifying idea. However, at this time, the term 3D printing is still used only for polymer technologies by most people, and the term AP is used in the context of metalworking rather than by people actively engaged in polymer/fatty jet/stereolithographic technologies. The term consuming does not replace the term machining but rather complements it when a term denoting any kind of material removal technology is needed.

In the first years after 2010, the terms 3D printing and additive production developed a new meaning in which they became synonymous with the broad concept covering all AP technologies. Although this is a departure from their earlier and narrower technical meaning, it reflects the simple fact that all technologies share the common idea of sequential and layered addition/joining of material, following the 3D profile of the workpiece, under automated control. Other terms that appear and which are commonly used as synonyms of AP (although sometimes hypervisible) are desktop manufacturing, fast production (such as the logical successor to a production level of rapid prototyping) and on-demand production (which reflects on-demand printing in the sense of two-dimensional printing). It is the first time that metal parts, such as engine supports [14] and large gassies [15] (both before and instead of machining) are constructed in the context of a single production, instead of necessarily being processed on a machine by rod blanks or plates.

Applications

Turbine model demonstrating the advantages of 3D printing in the industry.

AP technologies found their applications in the first years after 1980 in the field of product development, data visualization, rapid prototyping and specialized production. Their entry into production (single production, serial production and distributed production)[16] developed in the following decades. Since the beginning of the 21st century, there has been great growth in sales of AP machines and their prices have decreased significantly. According to consultancy Wohlers Associates, the global 3D printer and services market in 2012 was valued at $2.2 billion, a 29% increase from 2011. AP technologies have many applications, including architecture, construction (AEC), industrial design, automotive, aerospace industry, [18] military industry, mechanical engineering, dental and medical industries, biotechnology (human tissue replacement), fashion, shoes, jewellery, glasses, education, food industry and many other fields.

 

RepRap version 2.0 (Mendel)

In 2005, a fast-growing market was created with the introduction of open-source projects RepRap and [email protected] designed for people with hobbies and home application. In practice, all 3D home application printers sold to date use RepRap project technology and relevant open-source software initiatives[19]. A study has found that 3D printers can become a mass product that allows consumers to save money on buying the usual household items.[20] [21] For example, instead of buying an item produced factory-made by injection moulding from the store (such as a measuring cup or funnel), a person can print it at home using a three-dimensional model downloaded from the internet.

 

Basic principles

3D model of the “slicing” process

Modeling

3D models can be created with computer-aided design (CAD), through a 3D scanner or a simple camera and specialized software for measuring the distance and size of the objects in the photo. The processes of preparing 3D image information are similar to those of creating a sculpture. The information about the shape and location of the objects is analysed. Based on this information, a three-dimensional image of the scanned object can be created. Regardless of the object modeling software used, the model (usually in .skp, .dae, .3ds format) must be converted to .STL or .OBJ format so that the software responsible for printing can read the information.

Printing

Printer for 3D print “ORDbot Quantum “.

Before the model is printed from the STL file, it must be checked for errors and removed, if found any. This is especially true for models obtained with a 3D scanner, which most often receives errors. The errors can be of different nature: related to the image – parts of the object that are not connected to each other, missing parts of the image and more. These errors can be corrected by specialized software – netfabbMeshmixerCura и Slic3r [22].

Then, the STL file must be “cut” by software that converts the model to very thin layers and creates a G-code file containing specific instructions for the type 3D printer used. Then this G-code file can be printed (the software responsible for this loads the G-code and sends instructions to the printer). Often, the slicing software is included in the main package that is attached to the printer. There are several free Programs Skeinforge, Slic3r and Cura, as well as paid Simplify3D and KISSlicer.

A common program is gcode viewer. It allows you to track the path of the printer nozzles. This allows the user to change the G-code and print the object differently, as well as save on the necessary material for printing.

 

According to the instructions given to him, the printer sequentially lays the material layer by layer. In this way, the pattern is created by superimposing the many layers. The materials used can be plastic, sand, metal, even chocolate. These layers represent the cross-sections of the CAD model object, interconnected to form the shape of the final object. Depending on the size and complexity of the site, this process can take from minutes to days. The advantage of this way of printing is that almost any possible shape can be created.

From the printer, the resolution depends on how thin each layer can be and the detail of the object (imered at dots per inch (DPI) or micrometres (μm)). Usually, 1 layer is about 100 μm (250 DPI), although some printers can also reach up to 16 μm (1600 DPI) [23] which is comparable to the resolution of a laser printer. The individual particles (3D points) are 500 to 100 μm (510 to 250 DPI) in diameter.

Building a model with modern techniques can take from several hours to days, depending on the methods used, its size and complexity. Using several machines can significantly reduce the time required, although again it depends largely on the type of machine, size and number of models running at the same time.

 

Final phase

Although for many applications the resolution of the printer is quite sufficient, it can be significantly increased by using a process to remove the residual material from the original printing.

Some polymers allow smoothing of the surface by evaporation of various chemicals.

There are techniques that can use several materials in making the model. Thus, it can be printed in different colours or colour combinations without the need to be painted.

Printers

MakerBot Cupcake CNC

Industrial application

Since the end of October 2012, Stratasys has been producing systems ranging from $2,000 to $500,000, designed for a variety of industries: aviation, architecture, automotive, defence, and dentistry. For example,  General Electric uses a top-end model to make parts for turbines. One of the most important areas of application is in medicine, and by 2015 the preparation of dental implants and parts for hearing aids on  3D printers became the norm[24].

 

Application for the home

Airwolf 3D AW3D v.4 (Prusa)

Several projects and companies are developing affordable 3D printers for home use. Much of this activity is driven by (and is designed for) do-it-yourself enthusiasts, with additional help from the scientific and hacking circles.

RepRap is one of the longest-running projects in the desktop category. The RepRap project aims to produce free and open-source hardware for 3D printers that is able to make a copy of itself by printing many of its own (plastic) parts to create more machines. RepRaps is also capable of printing circuit boards and metal parts.

The price of 3D printers has dropped dramatically since 2010, machines that used to cost $ 20,000 now cost less than $ 1,000. For example, in 2013, several companies and individuals sold parts to make different types of RepRap, with a starting price starting at around $ 500. The Fab @ Home open-source project has developed printers for general use with everything that can be created, from chocolate to silicone sealant and chemical reagents.

In 2016, 500,000 3D printers were sold.

In 2019, this number is expected to be 5.6 million.

The number of 3D printers sold is expected to double each year.

Big 3D Printers

Large delta-style 3D printer

Large 3D printers have been created for industrial, educational and demonstration use. A large delta-style 3D printer was created in 2014 by SeeMeCNC. The printer is capable of creating an object up to 1.2 meters in diameter and 3 meters high. It also uses plastic pellets instead of the typical plastic threads used in other 3D printers.

Another type of large printer is Big Area Additive Manufacturing (BAAM). Its goal is to produce printers that can create a large object at a fast pace. Cincinnati Incorporated’s BAAM machine can produce an object at speeds 200 to 500 times faster than typical 3D printers from 2014. Lockheed Martin is developing another BAAM machine that aims to print objects up to 30 meters long to be used. in the space industry.

 

 

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