3D printing

The world of printing has taken a giant leap forward with the development of 3D printing. The 3D printing process is a milestone that is of great importance for a wide range of companies. All suppliers or manufacturers of spare parts, small series or even prototypes can produce them faster and more easily, so that company processes have been enormously accelerated and simplified by the 3D printing process. At print24 you can find out exactly what is meant by 3D printing, where its origins lie, what different processes are available and what the advantages are!

Definition of 3D printing

3D printing is also called additive or generative manufacturing. The idea behind this manufacturing process is to convert a numerical model into a three-dimensional model. Furthermore, it belongs to the urforming manufacturing processes, which means that a solid body is produced from a formless one. The body has a geometrically defined shape. So, in summary, 3D printing is the creation of physical objects from digital files. The digital data is generated by CAD modelling, data from 3D scanners or 3D modelling, but the 3D printer cannot read it directly. This in turn requires software that translates the geometric shape into the machine language of the printer through the G-code". The software is called a "slicer", which divides the 3D object into individual layers. The object is then built up/printed layer by layer, hence the name additive manufacturing. This contrasts with subtractive manufacturing, in which material is removed from existing objects. The printout of a 3D printer is three-dimensional, i.e. the object has a predefined width, length and height. Accordingly, the 3D printer works with a vertical axis (Z axis) in addition to the two usual horizontal axes (X and Y axis).

The structure and function of a 3D printer

Among 3D printers, a distinction can be made between open and closed printers, complete devices and kits. While most are delivered complete, kits must first be assembled by the user. Complete devices are usually more expensive than kits, but you save yourself the assembly. In the case of a closed 3D printer, the installation space is closed. Depending on where the printer is to be used, an open or closed version can be chosen. Basically, a 3D printer consists of a print/heat bed, support structure, print object, nozzle, support material and print material. However, the construction may differ slightly within a technology. According to the aforementioned construction, a 3D printer works as follows: First, the heating bed and nozzle warm up. Then the heating bed moves up to the print head. Molten filament (special plastics, metals or other materials) is then applied to the heating bed until the first layer is completed. When the first layer is complete, the heated bed travels down a distance of one layer height, measured here in microns. The second filament layer is applied on top of the previous one and fused with it. If there are areas of overhang, it is possible to use a support structure made of the same material or another, whereby the alternative material should be able to dissolve in water or even another solution. The last step is repeated until the 3D object is completed. 

Types of 3D printing processes

In the following, the most common 3D printing processes will be presented. In addition to the ones mentioned, there are many other variants. The following 3D printing processes can be distinguished:

• Selective Laser Melting (SLM)/Selective Laser Sintering (SLS)
• Electron beam melting (EBM)
• Fused Deposition Modelling/Fused Filament Fabrication (FDM/FFF)
• Stereolithography (STL/SLA)
• Laser build-up welding
• Film Transfer Imaging (FTI)
• Digital Light Processing (DLP)
• Multi Jet Modelling / Poly Jet Modelling

In the Selective Laser Melting process, a metal consisting of a powder is applied and melted by the laser. The desired print object is then lowered by the layer thickness, powder is applied again and fused. 3D printing takes place within a protective atmosphere; metals, plastics, sand or ceramics can be processed. In contrast, selective laser sintering (SLS) does not use pure metal powder but adds a binder. The special powder is also only partially melted, which causes the material to stick together. Electron beam melting (EBM) also uses powder and processes it in the same way as selective laser melting, except that an electron beam is used instead of a laser. A magnetically supported spring positions and directs it.

In the application of Fused Deposition Modelling/Fused Filament Fabrication (FDM/FFF), a special plastic is first heated and then the 3D object is printed in sheets. In this process, the filament is transported via a spool to the nozzle, from where it is applied to the build plate, where it solidifies directly. Since the surface of the object is often somewhat rough after production, it has to be reworked. The result of the precision work is satisfactory. The hardening of liquid plastic with the help of UV light takes place in the process of stereolithography (STL/SLA). The 3D object is produced in a bath of liquid plastic, using a laser to cure the individual layers. Any support structures used are removed after completion and the 3D object is cured. The models have a very high accuracy. Laser build-up welding uses a diode or fibre laser. It applies a metal powder or metal wire to the workpiece with the help of a nozzle. When using the powder, the 3D printer works fully automatically, which makes it suitable for use in component repair or prototype production.

Film Transfer Imaging (FTI) involves the application of a thin film of material onto a transport foil. The layers are created by illumination, whereupon the workpiece is lifted and then a new film is applied. This process continues until the 3D object is completed, which has a very high level of accuracy. Light-sensitive plastics are used as filaments in FTI. In Digital Light Processing (DLP), the 3D object is created from a plastic bath. The process is a mixture of STL and FTI 3D printing technology, whereby the FTI technology is used as in RTI. Multi Jet Modelling/Poly Jet Modelling, on the other hand, uses a technique similar to that of the inkjet printer. Here, several nozzles are attached to a print head, which then prints the 3D model layer by layer. The models are characterised by a very high level of detail and UV-sensitive photopolymers, which are cured with light, are used as filaments.

The materials for 3D printing processes

Due to the advancement of technology, over the years the material for 3D printing had to be adapted to it again and again. We present the most important specialised materials such as plastics or metals in the following:

Plastics for 3D printing

PLA (polyactide) is one of the most popular materials for 3D printing. The synthetic polymers belong to the group of polyesters, are obtained from corn starch, i.e. regenerative resources, and are biocompatible and recyclable. PLA can already be processed at low melting temperatures of 70 °C and generally remains dimensionally stable even when cooling. These two properties make PLA attractive for both private and professional users. PLA is now available in many different colours. The only disadvantage of the material is that it is only slightly robust and heat-resistant, so that it is not suitable for the production of highly stressed components.

ABS (acrylonitrile butadiene styrene) is the second most commonly used plastic material in 3D printing and is also a synthetic polymer. It is made from acrylonitrile, 1.3 butadiene and styrene. Advantageous properties are the strength, stiffness and toughness of the material. It can be used for prototyping and the manufacture of end products. ABS is printed at 220 to 250 °C and should be printed in a heated print room or print bed. In this, the manufactured objects can cool down and deformations can be avoided. Like PLA, ABS is available in different colours and is relatively inexpensive, but due to the high temperatures involved in 3D printing, it is less popular with private users. It also does not have sufficient weather resistance.

PEEK (polyetheretherketone) are synthetic polymers from the polyetherketone group. They can be used to print highly resilient and temperature-resistant objects. They are also biocompatible and resistant to chemicals. The thermoplastic PEEK is approx. 70 % lighter than metals with similar properties, but it has a comparable mechanical and thermal stability. The automotive sector, the chemical industry and the aerospace industry therefore prefer to use PEEK. It is printed at 360 to 380 °C and is therefore not very suitable for private use.

HIPS (High Impact Polystyrene) also belongs to the thermoplastic polymers and is produced by polymerising polybutadiene into polysterol. It has high impact strength and hardness and can be dissolved in chemicals. This makes it particularly suitable as a support material for other polymers. It is chemically removed so that even strict tolerances can be maintained in the manufactured components.

PA (nylon/polyamide) has a high tensile strength, melts at 250 °C and is non-toxic. 3D objects created with nylon are tough and damage resistant. Nylon is not damaged by most common chemicals and is inexpensive. However, the disadvantage of this material is that it is hardly suitable for private use due to the high melting temperatures and requires both a heated print bed and white glue so that it sticks to the print bed during 3D printing.

Most people are probably familiar with PET (polyethylene terephthalate) from drinks bottles. This is also where the advantage lies, because PET is food-safe and can be used for packaging. Since no vapours are produced during the melting process, 3D printing with PET does not require a heated printing room. This makes the application popular in the private sector. 3D objects made of PET are relatively robust but also flexible at the same time.

PETG (PET with glycol) achieves a high transparency of the material through modification with glycol. This also improves the printing properties. This results in a lower melting temperature and less crystallisation. PETG can be extruded faster than PET and is weather-resistant. That is why it is often used for garden furniture and tools as well as vases.

Metals for 3D printing

In addition to the plastics mentioned, metals can also be used in 3D printing.

Aluminium or aluminium alloys are compelling in 3D printing with their strength and good thermal properties. In addition, the 3D objects are light and can be flexibly reworked. The automotive, aerospace and aviation industries benefit from the use of aluminium alloys; engine parts, housings, moulds, prototypes, air ducts and much more are produced using 3D printing.

Titanium or titanium alloys are among the best known in 3D printing with metals. It has outstanding mechanical properties and at the same time only a low specific weight. The material is corrosion-resistant and can be used in many environments with high technical requirements such as aviation. Medical devices, spare parts, functional prototypes or end-user parts are the most common 3D objects made of titanium alloys.

Another metal used in 3D printing is stainless steel/stainless steel alloy. It is low in carbon and very corrosion resistant. Appropriately manufactured parts also have excellent strength, good thermal properties and high ductility. 3D printing with stainless steel is preferably used for machine components or food-safe applications.

In addition to plastics and metals, ceramics, sand, concrete and glass are also among the materials used in 3D printing.

The history of 3D printing - who invented the 3D printer?

The history of 3D printing goes back to the 19th century. In 1859, the Frenchman François Willème, who worked as a photographer and sculptor, invented an apparatus that made it possible to create a 3D model with the aid of several cameras. In 1892, the Austrian Joseph E. Blanther applied for a patent for the production of relief maps. For the production of these maps, wax plates were laminated at that time and the desired shape was cut out of them and glued on top of each other. This created the 3D map through several layers.

After no further known development of 3D printing in the 20th century for several decades, the Japanese inventor Hideo Kodama finally applied for another patent in 1980: In this, he described how a photopolymer material hardens using UV light and in this way, a model is created layer by layer, which is similar to the principle of stereolithography. As he could not continue to pay for the patent application due to financial difficulties, he lost fame. In 1984, the Frenchmen Alain le Méhauté, Olivier de Witte and Jean-Claude André tried to obtain a patent for the process in which a liquid is hardened with a light source. They also called this stereolithography. However, the research institute contacted could not see the potential of the invention and stopped the project. Finally, it was the American Chuck W. Hull who applied for a patent three weeks later. He had already invented stereolithography in 1981, which was first put into practice in 1983. In 1985, the first 3D design programme was available and in 1986, he founded the now world-famous company 3D Systems. In 1988, the first 3D printer (SLA-1 machine) was on the market.

In 1992, the first selective laser sintering machine was produced at DTM, which irradiated powder with laser light according to the process. This was followed by a 3D printer from Z Corp, which used the binder jetting process. By the end of the 1990s, metals could be processed in addition to plastics and more CAD programs were released. During the 2000s, additive manufacturing gained momentum, which was established in medicine. For the first time, a 3D-printed organ was implanted in a human being. The 2000s were marked by further developments. 3D printers could now produce parts for other 3D printers and they entered the workplace. From 2010, the new models could also print car prototypes, 3D food printers emerged, the first 3D-printed components for space stations and jaw and bone prostheses. Likewise, small and medium-sized enterprises benefited from 3D printing, which enabled them to produce prototypes more cheaply. The most productive additive plastic production process is currently the Multi Jet Fusion process, whereby the resulting objects have a homogeneous surface and an almost pore-free material density.

So what does the future hold? It is very likely that the technology of 3D printing will develop towards mass production, as more and more materials can be printed in a shorter time and in high quality.

High-quality printed products at print24

With us you can have your desired object printed for advertising purposes or your everyday office life. print24 offers you a huge range of print products, which we deliver to you quickly and in high quality. Large-format print objects, textile products or photo products are also part of our range. Simply choose the print products you want and design them individually!