2.5D graphic
A tactile graphic for visually impaired people. With a swell form graphic or printing with a Tiger embosser there is not only a 2D view, because lines, areas, dots, braille etc. are raised into the third dimension. However, since these are all the same height, we refer to them as 2.5D graphics.
8-Dot braille
A variant of braille that was originally developed for computer use. Instead of the usual 6 dots, there are 8 dots. With these two additional dots, there are now 256 characters instead of 64 braille characters, so it is possible to assign the 256 characters of a Western European character set to the 256 possible 8-dot braille characters. Thus, with 8-dot braille, there is also a unique symbol for each capital letter, for each number, for each special character, etc.
Blender
Open source software for modelling, animating and creating 3D models. The software is used by professionals and is very powerful. A video editor is integrated and game developers use the game engine for development.
Braille
A system of writing used by visually impaired people to read by touch. The tactile script was invented in 1825 and has become accepted worldwide. Classically, braille has 6 dots, which results in 64 different characters.
Computer-Braille
see 8-Dot braille
Eurobraille
see 8-Dot braille
Extruder
The printing unit of a 3D printer where the filament is melted and pressed onto the printing surface. The hotend is often referred to as the extruder, but the hotend (consisting of the heating block, heating cartridge and nozzle) is only one of the two main parts of the extruder.
A distinction is made between direct drive extruders (where the filament feed is located directly on the print head) and Bowden extruders (where the filament is fed into the extruder through a PTFE tube).
FDM
This stands for Fused Deposition Modelling and is a 3D printing process based on extrusion. Filaments are melted with a heated nozzle and built up layer by layer into a model. The 3D printed component is created on the print bed. The FDM process is the cheapest 3D printing process, which is why it is often used in private and school contexts.
Feeder
The part of the extruder that is responsible for transporting the filament. The feeder is part of the cold end, i.e. the part of the extruder that should not get warm.
The feeder usually consists of a stepper motor on which a gear wheel is mounted and a spring-loaded idler as a counter bearing. The filament is transported between these parts in the direction of the hotend.
Filament
Generally used to refer to a single fibre of any length. In the 3D printing context, filament is the printing material for FDM printers. Various plastics are available and PLA is often chosen by beginners as a cheap and easy-to-print material. The filament is supplied rolled up on a spool. The most common diameter is 1.75mm, although 2.85mm is also sometimes used.
Fusion 360
A commercial software application for computer-aided design, manufacturing and engineering. With the help of the software, developed by Autodesk, 3D models can be designed digitally. It is available for Windows and macOS, with simplified apps for Android and iOS.
Fusion 360 is also aimed at professional users and is therefore very powerful in its range of functions. In an educational context, a free licence can be obtained after registering at Autodesk and providing proof of teaching activities.
Layer height
The setting in the slicer, which influences the quality and also the printing time. In the FDM process models are built up layer by layer from plastic and the height of the layers can be adjusted during slicing. The maximum layer height depends on the diameter of the nozzle and should not exceed 50-75%. A large layer height results in fewer layers being printed, which significantly reduces the printing time. However, the resolution of the printed object also suffers. Layer heights of 0.1 to 0.25mm are common in our context.
Line symbol
Often used on maps and other illustrations. When maps and models are designed for visually impaired learners, line symbols must be tactile. It has been shown that lines should be raised rather than recessed. If different line symbols are to be used on a tactile representation, they must be tactilely distinguishable. See 3.7 Line symbols.
NFC
This stands for Near Field Communication and is the international transmission standard for the wireless exchange of data over short distances. A maximum distance of a few centimetres can be bridged. NFC is based on RFID technology, which transfers data via electromagnetic induction.
An NFC tag is a small memory chip with a storage capacity of 168 to 2048 bytes and can be purchased, for example, in the form of stickers. Various apps can be used to store information on the tag, which can then be read by an NFC-enabled smartphone. With this technology further information can be stored on 3D printed models at a later stage.
Nozzle
Located in the hotend of 3D printers using the FDM process. The heated filament is extruded from this nozzle onto the print bed, creating the model layer by layer. A nozzle with a diameter of 0.4mm is often installed as standard. The nozzle is a wear part and must be replaced from time to time. If replacing the nozzle, one with a larger diameter can be chosen (printing time is reduced, but so is the quality). Special nozzles are also available for special filaments. See 4.2 nozzle size
OpenSCAD
Free CAD software that generates 3D models using a text-based programming language. The objects consist of simple geometric basic bodies and are brought together using transformations and modifications to form a complex 3D model. Since it does not work graphically, OpenSCAD can also be used by visually impaired people. The prerequisite is a good spatial imagination and no fear of programming language.
Penfriend
This is a small device for the voice-based labelling of items. A small sticker is placed on the area to be labelled and a voice recording of this sticker can be created and saved using the penfriend (which looks like a pen). The spoken information is stored on the penfriend itself and can be played back with the same device by scanning it. As the device was developed especially for visually impaired people, it is very easy and accessible to use. See also chapter 6.1 for more information.
Point symbol
Used, for example, to mark cities on tactile maps. As with line symbols, point symbols must always be designed as raised dots and not recessed.
If different point symbols are to be used on a tactile representation, they must be tactilely distinguishable from one another. See also chapter 3.8 for more information.
Print bed
An important component of the FDM 3D printer on which the model is built up layer by layer. Depending on the type of printer, the print bed is stationary or moves horizontally or vertically. The print bed must ensure two things that are not easy to achieve in parallel: the first layer of the object to be printed must adhere well to the print bed but the object must also be easy to remove from the print bed after 3D printing. However, the use of heated print beds and removable coated plates has solved this difficulty to a large extent. The size of the print bed limits the maximum size of the model in the x- and y-directions, 20x20cm being a common size in 2022, but larger print beds of up to 40x40cm are no longer a rarity.
Printing orientation
This is a crucial factor when slicing a model before printing, as it determines the quality and stability. As 3D objects are free to rotate in space, you have to decide on the optimal orientation for printing. It is obvious, for example, that the results of printing a pyramid on its tip will not be ideal. However, overhangs that threaten to collapse can often be printed satisfactorily using a better printing orientation. The quality of braille is also significantly affected by the printing orientation. See also chapter 3.9 for more information.
Real object
The opposite of the 3D printed model. As described in the decision tree (see chapter 1), the real object should be used as often as possible. 3D printed models are used if the real object is not available (too expensive, too small, too big, too unstable, etc.).
SketchUp
Software for designing three-dimensional models. The name alludes to hand sketching because of its speed.
In contrast to CAD programmes that can only be used by professionals, SketchUp is also aimed at beginners, who can make rapid progress here. Unfortunately, complex models always lead to bugs that can’t really be fixed.
SketchUp’s range of functions can be expanded with the help of countless plugins. However it is particularly useful if geometric rather than organic design is required. A discounted licence is available for teachers.
Slicer
A Slicer refers to software used in most 3D printing processes to convert a 3D model into specific printer instruction. Typically, an STL file is converted into G-code here.
The slicer converts the model into a stack of flat slices and describes them as linear movements of the extruder. The resulting G-code a pure text file in some kind of numerical control programming language that instructs the 3D printer to print, move axes, and so on.
Support
The added part of a 3D printed model where large overhangs are threatening to collapse. As the layers are applied one by one from the nozzle onto the print bed, each new layer requires a certain substructure. Without support the cantilevered balcony of a printed house would most likely collapse, as the printer would apply the filament freely into the air.
To avoid this, support can be activated in the slicer. The printer then applies a structure of filament as a support on which the balcony described above can rest during printing. After printing, the support can be removed fairly easily, as the actual component should touch the support but should not be able to bond with it. Support can often be avoided by clever printing orientation.
Superelevation
A special type of linear scale for use in tactile maps on the vertical plane. Often height has to be shown in a different scale to longitude and latitude, as this would otherwise hardly be perceived tactilely. A well-chosen factor of both scales enables mountains to be differentiated from hills, but also does not become too exaggerated. See also chapter 2 for more information.
STL file
The most common file format for the exchange of 3D models. After saving in STL format, the models are difficult to edit but can be easily exchanged. The STL format is similar to the PDF format for documents. See also article 5.2
SVG file
A frequently used file format for two-dimensional vector graphics. Unlike pixel graphics (e.g. JPG or BMP), graphics in SVG format can be scaled to any size without affecting the quality of the graphic.
Swell form graphic
A method for the production of tactile images. A laser printer is used to print the desired graphic (including braille) on swell paper. All black ink areas of the sheet are raised after the paper has been run through the fuser where the paper is heated. Swell paper is available in the sizes DinA4 and DinA3. The method is well suited for the presentation of charts, diagrams, mathematical drawings or simple maps. Drawings can easily be made on a PC, depending on the complexity. Unfortunately, all black areas are raised equally after heating, which is why it is called a 2.5D method. Swell form graphics therefore have a fundamentally different approach to 3D printed models.
Texture
The texture of the surface of a model. When designing models for visually impaired learners, colours cannot be used to distinguish different parts of the model. Instead different textures must be used which can be clearly distinguished tactilely after printing with the 3D printer. Depending on the software, these textures have to be designed differently. See also article 3.2
Tiger embosser
A process for the production of tactile graphics. With a special printer, the so-called Tiger embosser, graphics can be printed tactilely. A printer driver analyses the graphic and converts it in such a way that many embossed dots represent raised lines, areas, etc. It is then printed as a tactile grahic. Braille can also be embossed directly, but the quality is not comparable to that of a braille printer.
Tinkercad
A free online 3D modelling program that runs in a web browser. Especially among beginners, Tinkercad has become a popular platform for creating models for 3D printing. Using an integrated collection of shapes, numbers, texts, characters and more, the models are created and exported in STL format. Advanced users often switch to another programme, as Tinkercad is easy to use but also has limitations when creating complex models.
V symbol
A special symbol that can be digitally attached to existing models and then printed along with them. The symbol can be printed instead of braille, for example, and a key can be used to provide explanations. There are six distinguishable V symbols that can be downloaded as STL files. See also chapter 3.9
Vacuum forming
A plastic manufacturing process in which a plastic sheet or film is heated and sucked onto a matrix using a vacuum (also called thermoforming).
Using this process, copies of the matrix can be produced from thermoplastic materials. Especially in the construction of tactile maps, unique pieces can be easily duplicated in this way.
Wall thickness
A crucial factor for the stability of 3D printed models. When models are designed on a PC they are usually drawn as solids. The thickness of the wall is determined during slicing (in mm or in shells). If a model is printed completely hollow, a wall thickness of 1.2mm (with a nozzle of 0.4mm) should not be exceeded. If infill is used, a wall thickness of 0.8mm is often sufficient (depending on many factors).
Z seam
The seam between the individual printed layers of the model. After one layer is printed, the print head must move up one layer to apply the next layer of filament. When slicing, there are several options for setting the Z seam. This can be selected randomly so that there is no fixed seam that remains visible. However, there is a risk that many small dots will be created as a result of the print head rising. Especially for models with outer edges (such as a cube), it is better to place the Z seam manually on one edge of the model. This way the seam remains more or less invisible.
