2. Special Requirements of Learners with a Vision Impairment

Table of Contents

Being a computer-based process, 3D printing requires a certain basic knowledge of operating computers and their peripherals. To design objects the designer must have a basic understanding of shapes and orientation in space. In addition, they should also know about planning and design criteria and how to apply them.

Introducing learners with a vision impairment to the design of 3D models on the computer involves further specific challenges and fields of learning, in addition to the general prerequisites mentioned above. These will be outlined below in order to teach educators about them so that they can provide individualised pre-modelling plans for their learners and offer specific support during the learning process.

At this point, however, it is also important to emphasise that the basic conditions described here assume a high level of competence. Of course, gradations are also possible depending on the learning age or degree of vision. These can then be compensated for by modifying the preparation or teaching as appropriate. Likewise, it is possible that a 3D printing activity can also encompass the teaching of vision-impairment-specific skills (e.g. improving understanding of shapes and orientation in space) in addition to simply creating a haptic product.

2.1 Basic Understanding of 3D Concepts

People who have been blind since birth often have a different or no idea of the relationship between objects in space. It is also important to recognise that the physical dimensions and nature of certain objects cannot be readily understood, as it is not possible to explore them through touch (too big, too small, too dangerous, too far away, etc.). It should therefore never be an objective to construct an object of which there is no or only a vague idea, since constructing means moving to a further level of abstraction. The spatial imagination and the knowledge of the nature of objects must therefore be clarified and discussed in advance in order to prevent frustrations during the construction process.

If this prior knowledge is not available, the objects should be introduced in 3D-printed (or other) form at the beginning. The learners should explore them independently under guidance. Verbalising what they have touched can also help to consolidate the idea. It is advisible to explain every single step using models already available.

Especially with younger learners, it is a good idea to go to a more basic level and first explore basic geometric shapes and bodies (cube, cuboid, sphere, cylinder, etc.). These can then be combined into more complex structures through physical movement (as when playing with building blocks). Operations that are fundamental for 3D printing (such as rotating, repositioning, scaling, etc.) should also be made tangible in advance in this way. The same goes for procedures that make new objects out of combinations of other objects (e.g. merging).

In addition, active exploration of space can be of great benefit. Actively moving through rooms, avoiding obstacles, rearranging furniture, etc. help develop an understanding of how three-dimensional spaces are designed and how individual objects are aligned with each other. Cross-curricular projects can also work here (e.g. in cooperation with physical education), where someone is positioned with objects and other people in a huge coordinate system or in which tasks relating to shape, movement and orientation are mastered.

Ultimately, all these preliminary exercises serve to enable learners with a vision impairment to develop an abstract idea of three-dimensionality in order to be able to create it virtually in a code- or block-based manner.

2.2 Basic Computer Skills

In our many years of work with learners with a vision impairment in regular school subjects, certain applications have emerged in computer work whose usability and compatibility with assistive technologies are particularly suitable for everyday use. We focus mainly on PC applications in Windows, as this operating system is also widely used in the working world and becoming familiar with it is therefore a learning objective in itself. The same applies, for example, to the slicing software, which can be controlled via a command line. It makes sense to use the modelling software in Windows first as well, since open-source variants such as Blender etc. are available for this but also for other operating systems such as Linux. The limitation to one operating system also helps to narrow down the skills and knowledge that are required from the learners in order to be able to actively engage in the design process of a 3D printing activity.

The first skills to be taught are, of course, those related to file management. This is not only the basic understanding of how files and folders are structured (tree structure), but also how they can be copied, moved, renamed, deleted, etc. This explicitly includes the use of externally stored files and therefore also the use of external storage media or network environments. It is particularly beneficial for users who cannot work with a mouse to learn the most common key commands (e.g. CTRL+C for copying or CTRL+V for pasting files, folders but also text modules).

Generally, users with a vision impairment should have a solid knowledge of the keyboard layout, as this prevents typing errors during coding and avoids frustration. Frustration when programming can arise simply from the large number of special characters needed which are only rarely used under other circumstances (e.g. semicolons or square and curly brackets). Another aspect of programming is that the structure of code is often made readable by indenting, a technique not readily available to users with a vision impairment. It can therefore make sense to minimise these difficulties, especially for beginners, as we did in the Miniature Block Worlds Activity (cf. 3.4) by avoiding as many special characters as possible.

Furthermore, we recommend coding in a low-complexity program such as the Windows text editor, as too much functionality can lead to confusion. After all, it is good for learners to develop strategies to orientate themselves in menu ribbons so they can find less frequently used functions for which the key commands may not be known. Macros that simplify complicated key sequences may be considered as a way of easing the burden on learners with different levels of this specific knowledge. Other editors that can be easily adapted are available. They can be used to automate steps in the printing process (e.g. rendering, slicing).

Finally, we would like to mention the command line used in Windows. This makes it possible to enter actions as a text-based chain of commands. For many people with no vision, this is more comfortable than dialogue windows, which are not always reliably displayed in a clear way by assistive technologies. In later sections we will describe how it can be used in 3D printing.

2.3 Assistive technologies

Even though we have so far mainly dealt with applications that were not developed specifically for people with a vision impairment, the term “assistive technologies” has already been mentioned several times. This term is used to refer to software and hardware that enable users with a vision impairment to read screen contents on a computer. We cannot go into detail here, as this is a very broad and specific field of expertise. Nevertheless, we would like to give those who are dealing with this topic for the first time a basic understanding in order to sensitise them to the fact that the field of assistive technologies is an additional field of learning for all learners with a vision impairment, so extra time has to be given to this in their education and additional challenges will arise. But again, an action-oriented 3D printing activity that empowers learners in a positive and constructive way to make a physical product on their own can be used as a practice space for this specific learning.

But what are the basic building blocks of a computer workplace supported by assistive technologies?

2.3.1 Screen Readers – a solution for learners without sight

First of all, there is a need for a screen reader. This is software that reads the screen content and can convert it into two non-visual forms. The content can either be reproduced as audio via speech output, or explored tactilely line by line by means of a braille display.

The most popular screen readers are the free open-source project NVDA and the commercial software JAWS. There are other screen readers, for example those included in operating systems. Despite all the similarities and differences, it should be noted that both products are controlled via the regular computer keyboard or the additional keys on the braille display. This fact alone results in numerous key stroke combinations and sequences that have to be memorised by the learners. Fortunately, the key combinations used by the two screen readers mentioned above are identical in the vast majority of cases, thus simplifying the work in learning groups in which different screen readers are used.

Less obvious, but no less challenging, is the fact that the visually perceivable screen content and the conversion processed by the screen reader are structured differently. So, for example, when communicating where a certain control element is located on the screen, one must always be aware that this may well differ on the braille display or in the audio transcription. Moreover, it is not uncommon for individual control elements, text fields or entire program windows not to be processed by the screen reader software at all. In these cases, the speech output remains mute and the braille display remains blank or only incomprehensible character strings are transmitted. (However, these difficulties tend to occur less frequently in text-based environments).

Another special feature of working with screen readers arises in web-based environments. In web browsers, the ordinary letter keys are needed to perform navigation commands (e.g. moving directly to buttons, edit boxes, headings, check boxes, etc.). However, this useful feature prevents direct text input in browsers and requires activation of the editing mode. We mention this special feature here to emphasise that additional knowledge must be imparted or assumed here as well.

These are the main reasons why we have tested different environments in this project and have worked out a setting that aims to run as smoothly as possible.

2.3.2 Magnifiers – a solution for learners with a less severe vision impairment

Screen magnification programs are available for learners who have visual perception. The fastest and cheapest solution here is certainly the Windows magnifier. However, commercial programs such as ZoomText offer greater functionality and adaptability for a wide range of needs. For example, contrast can be improved or colour inversion and edge smoothing can help to better recognise details. However, especially at very high magnification, the handling needs to be practised, as the section of the image displayed becomes smaller and smaller and thus context might get lost. Modifying the hardware used can help here. For the visual design of 3D models, larger monitors or a two-monitor arrangement, on which the model preview and the program code are displayed separately, have proven helpful.

Learners with a visual impairment who work with magnification can still use the possibilities offered by a graphical representation of models in any CAD-software. However, this usually has to be adapted to individual needs. This is possible both through the assistive software used and directly, for example within the modelling software.

Working with magnification software and additional hardware is a separate field of learning, and its possible applications cannot be presented in detail here.

2.3.3 Non-technical aids

It is also worth mentioning that non-technical aids can also contribute towards successful outcomes in 3D printing for non-sighted and visually impaired learners. For example, adhesive dots can help to mark frequently used keys on the keyboard or essential buttons on the 3D printer. Magnifying glasses enable close inspection of 3D-printed objects and rubber mats prevent slipping when objects are being explored. And in general, a well-lit workplace improves visual perception.

Even learners with a vision impairment can extrude 3D objects from a 2D shape. For example, turning a circle into a cylinder. Before starting the actual coding, it is helpful if two-dimensional sketches are used to exemplify the idea. This can be done with tactile foil, magnetic boards or fuser foil. (Note: A sketch must not represent a two-dimensional projection of a 3D object because this cannot be properly perceived through sense of touch.)

For further non-technical aids, the relevant literature on Daily Living Skills offers more tips and tricks.

2.4 Basic Understanding of 3D printing

This field encompasses computer skills as well as the basic understanding of 3D concepts described in 2.1. Learners should receive an explanation of how 3D printers work and how objects are built layer by layer. As the actual printing process cannot be experienced using one’s fingers, play dough, salt dough or clay can function as a means of representation. The dough must first be formed into a spaghetti shape. Then each strand can be laid on top of each other to form a simple model, for example a cylinder. In this way, it is possible to experience tactilely how three-dimensional objects are created from threads in the 3D printer.

A particularly important aspect of understanding how a 3D printer works is to understand what “overhangs” are and how important they are to the printing process. An overhang refers to the portion of a model that protrudes horizontally parallel or at a shallow angle to the build platform. Even with dough it will not be possible to construct overhangs without deformation because the overhanging dough will fall to the ground. This explains why overhangs should not be printed without supports as the layers cannot maintain their position.

Nevertheless, we recommend a haptic exploration of a 3D printer, when it is turned off and has cooled down. The previous experience with the dough can be transferred to the printer. If you let the printer extrude a little manually and then switch it off and let it cool down, you can touch the “spaghetti” on the nozzle. This is deposited on the printing table, in a similar way to the process just described. The filament coil attached to the printer serves as the dough supply. It is also important to allow the moving parts of the printer to be changed manually, for example, in order to be able to understand the dynamics of the process.

In order to teach the various steps that have to be taken to turn a source file into a tangible model, one can start by downloading models from www.tactiles.eu (or any other 3D model database). Taking it from there, learners can familiarise themselves with all required procedures and practise using their assistive technologies in these particular environments.

More advanced users will be able to modify the downloaded models and start honing their design skills. Yet another option is to use 3D scanners to avoid having to design from scratch and to get straight to practising the slicing and printing processes.

It is important to keep in mind that all these approaches have to be tailored to the skills, needs and learning objectives of each individual learner. There is a great variety of options that educators can choose from.

2.5 Competency of Educators

To carry out 3D printing activities with learners with a vision impairment, educators should possess certain important qualities. Firstly, they need to empathise with the experiences of their learners and understand how to achieve the intended learning goals within their specific perceptual capabilities. It is crucial that educators do not simply transfer assumptions from the sighted world, but instead develop alternative approaches and solutions tailored to the needs of learners with visual impairments. This also requires educators to apply these alternative approaches themselves, such as operating assistive technologies, and to experiment in order to find alternative methods.

Another important aspect is considering the heterogeneity of learners’ experiential world. Each student is unique, with specific abilities, needs, and interests and one type of vision impairment is not the same as another. Educators should promote this diversity and align their teaching accordingly. Moreover, establishing consideration and mutual support within the learning group is of great significance. This fosters a positive learning environment in which all learners can develop their skills.

Educators should also encourage variability in the use of different tools and approaches. As shown above, there is a wide range of aids that can facilitate 3D printing for learners with a vision impairment. Educators should present learners with various options and encourage them to explore different approaches in order to find the one that is most suitable for their individual needs.

By incorporating these qualities and approaches into their teaching, educators can effectively engage all learners in 3D printing activities and provide them with an inclusive learni