3D Printing from Start to Finish
This article has been written by Jeanett Tschiersky, Director CTC Strategic Marketing and Dr. Sergej Stoetzer, Senior Expert CTC Strategic Marketing & Trainings at Conrad Business Supplies
Hardly any technology has developed as quickly as 3D printing within just a few years. In a very short timeframe, a device for professional prototyping became a suitable tool for hobbyists, with which today even large components and complex components are produced – right through to small-batch production using additive technology.
Printing techniques in the 3D world
There are many ways to create 3D objects. The simplest – and one of the first technologies developed in the 1980s – is the layered deposition of molten material, which solidifies and thus "prints" layer by layer into a three-dimensional object. The process is referred to as Fused Deposition Modelling (FDM) or Fused Filament Fabrication (FFF). In essence, 3D printing is also known as "additive manufacturing" because material is added layer by layer – unlike conventional metal-cutting where an object takes on its shape by removing material from a piece of metal.
Other printing methods include Selective Laser Sintering (SLS) and Stereo Lithography (SLA). With the modern SLS process, powder is heated with a laser in a short time, so it melts. After that, it solidifies again. The material cools down very quickly so that it can no longer change its shape. With selective laser sintering, it is possible to create layers in the micrometre range resulting in the creation of delicate and precise structures. Plastic, metal or ceramic powder is used. The use of materials beyond plastic makes this printing process particularly interesting for industrial applications.
Stereo lithography is one of the 3D printing processes involving liquids. It is the first technique used to create three-dimensional, printer-based objects. In this process, the object emerges from a plastic bath, which is cured at the relevant points by a laser. The procedure is technically quite complicated, but nevertheless very well developed. Objects can be produced very precisely, but only certain plastics are suitable for SLA printing.
Another recently popular method is the polyjet technique. With different print heads different materials can be processed and combined accordingly.
The heads carry a building material and a support material. The photopolymers used in this process are cured by UV light. If you use more than two print heads, you can also create objects made from different materials. These can have different hardness or different colours.
A basic classification of the various 3D printing processes can be made according to the type of material being applied:
- 3D printing with powder materials (3DP): this includes, for example, selective laser sintering.
- 3D printing with molten materials, such as FDM processing.
- 3D printing with liquid materials. This includes the SLA process, in which the object emerges from the liquid, as well as the polyjet process, in which a liquid similar to the FDM pressure process is applied layer by layer and cured.
How does a 3D printer work?
With the distinctly different 3D printing processes, also different are the technical requirements for the respective printers. Therefore, the question of the function of a 3D printer can’t be solved separately from the printing process.In a FDM process, a plastic wire is melted in the print head and extruded through a die. The molten plastic is applied to a platform and cooled there. This is how the component is built up in layers. Depending on the component, this method requires a support structure that gives it stability during the printing process for structures with flat angles (overhangs, bridges). The support structure is ideally built of a different material from a second nozzle and removed after completion of the printing process.
Laser sintering, for example, takes place in a thin layer of metal powder, which is melted by a laser. The material combines and then hardens. In the next step, the construction platform is lowered, and a new layer of powder applied. This is the layered structure of the component. Also, in this method, a support structure is used, which additionally takes over the task of heat dissipation. In principle, laser sintering also works with plastic powder, but the process does not require support structures.
When printing with liquid materials, there are, as mentioned above, different pressure principles. The polyjet process uses print heads similar to those of an inkjet printer. The material of photo polymers is applied drop by drop and cured directly by UV light. You can use different materials as well as different colours at the same time. An easily removable support structure is also necessary. In stereo lithography plastic is also cured by UV light. However, this requires a UV laser. This forms the structure of the component directly in a bath of photo polymer, which hardens in the focus of the laser.
From idea to 3D component
Just as conventional 2D printers require a template (a text or image in the form of a file) to make a printout, 3D printing also requires this. However, the user has to create a three-dimensional model for this. For beginners, there are numerous ready-made 3D models that can be downloaded for free on the Internet. In educational institutions or in research, however, it will be important to create the models according to your own ideas. For this, the printer manufacturers all offer the right software for their models, called “slicer”, to break down the model into planes for printing. In addition, independent manufacturers offer appropriate CAD software with a wide variety of equipment and for a wide range of requirements – sometimes free of charge. The possibilities range from relatively simple forms to complex constructions or even entire sculptures. Each user can select the software according to their requirements. Of course, there is also support on the Internet or from the manufacturers. Particularly interesting is the ability to transfer data from a 3D scanner to a 3D printer. In addition to the CAD programs for template creation, there are also software to check or repair CAD templates.
An example of freely available software for creating 3D printed models is the Tinkercad online app. This is great for schools because it does not require any CAD experience or software installed on the computer. From simple shapes, the desired components can be built. These can also be imported. Each form allows the user to assign a material (this is only for visualisation, as the 3D-printed part depends on the 3D-printing method and materials used). The shapes can be moved, rotated and adjusted freely in space. With tools such as the ruler, dimensions can be entered exactly. Furthermore, different shapes can be combined to create models with the desired depth of detail.
Which printer for which applications?
Similar to the software, this applies to the choice of printer. Users first have to clearly define which goal they want to achieve. The differences from lower-end to high-end expensive 3D printers are not fixed. However, the expensive models are usually characterised by better quality of the results as well as higher resolution and ease of use. The equipment, such as the number of printing or extruder heads varies. Of course, the processing also plays a role when it comes to cost, as well as the technology used.
3D printers in education facilities
For beginners and educational institutions, FDM printers are the best choice because they can produce good and usable results very quickly. In addition, the printing material is cheap and maintenance easy. Laser sintered printers, for example, require special security and SLA printers make handling the photo polymer difficult.
To introduce beginners to the possibilities of 3D printing, FDM printers with single extruders are ideal. The flexibility in the production of components is largely determined by the functionality of the CAD software used. Here, the user can choose freely, the offer ranges from simple online applications to highly specialised CAD programs.
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