The Braille Authority of North America publishes Guidelines and Standards for Tactile Graphics. While these guidelines are important, some of them are not directly applicable or possible with the use of a 3D printer. Below is a discussion of best practices and considerations for tactile graphic generation using a 3D printer based upon the aforementioned guides and standards document. This is by no mean a comprehensive document, and we encourage users to read the BANA standards

Keep It Simple!

• Tactile graphics do not have to be an exact reproduction. "Represent, don't reproduce"
  • Print graphics should be modified as long as the original intent is not changed.
  • If the task does not involve measurement scale/size/position/layout may be made to clarify
  • If a change is made it is helpful to include a brailled "transcriber note" about the change to accompany the graphic
• Irrelevant design elements should be omitted (i.e. decorative borders/image outlines/frames). Just because something is visually appealing does not mean it's tactually legible or meaningful.
• Avoid cluttered elements. Add blank spaces between adjacent textures or where lines cross other lines or textures when contrasts in texture and line width is not clear.
• In general a single graphic should contain no more than 5 different textures, 5 different line styles, and 5 different types of point symbols, if more are needed consider using a key

Keep Things as Consistent as Possible

• 2.3 in the BANA standards states, "The braille code and format used in preparation of the tactile graphic must be consistent with the transcription of the main body of text." This however is not always possible given the resolution of a 3D printer when printing braille. For that reason, if consistency is of the utmost importance, try adding braille manually to the graphic.
• 2.4 in the BANA standards states, "The dimensions of the braille text page(s) and any inserted tactile graphic page(s) should be the same." This may not be possible give the size of your 3D print bed. Try to keep things close or forgo cutting the paper if possible. Braille is usually printed either on 8.5"*11" or 11.5"*11"
• Tactile graphics produced with different methods CAN be combined in the same volume

Orientation and Layout Matters

• The graphic should be positioned near the left margin of the page rather than centered.
• Place page numbers (if appropriate) in braille in a consistent spot

Keys and Symbols

• Use a key if a braille word does not fit in the available space between elements or detracts from clarity.
• Maintain constancy when using keys/symbols/textures to items
• Consider the age and experience of the reader, it may be necessary to limit the number of key symbols
• Facing pages should be used to allow a reader to see both key and graphic when they do not fit on the same page.
• Keep keys the same size for texture keys, BANA recommends 1/2" (12.5mm) * 1" (25mm)

Sizes

Considerations of size while important are more guidelines instead of set and fast rules. Design choices should always be made with the braille reader and their feedback in mind.

Line Widths

Consider scaling these up 50% (needs more testing...)

Style	Point Value	Millimeter Value
Axis Line	2.5pt	.88mm
Grid Line	1.0pt	.35mm
Measurement Dimension Line	1.5pt	.53mm
Tick Mark	1.5pt	.53mm
Plotted Line 1	6pt	2.12mm
Plotted Line 2	4pt	1.41mm
Plotted Line 3	2pt	.71mm
Plotted Line 4 (dashed)	3pt	1.06mm
Dashed (half dash sized spacing)	1.5pt	.53mm
Dashed (half dash sized spacing)	2.5pt	.88mm
Dashed (half dash sized spacing)	3pt	1.06mm
Dashed (full dash sized spacing)	1.5pt	.53mm

Graphic Size

• According to BANA standard 3.4.2 the maximum width and length of a tactile graphic is 40 cells by 25 cells on 11 by 11.5" paper given adjacent cells are .092" cell to cell horizontally and .245" vertically the max dimensions are 9.8" by 10" for 11"*11.5". Given most printers do not have a bed size large enough to support that large of graphic, we suggest maintaining a margin of 1" and 1.5" around the width and height of the graphic.

Element Sizes

• Areas should be a minimum size of 1/4 square inch (6mm)
• Lines should be a minimum of 1/2" in length (1.25mm)
• Dashed lines, each dash should be 1/4"-3/8" (6mm-10mm) long and separated by spaces approximately half the length of the dash (3mm-5mm)
• Secondary lines, for tick marks on graphs - the length should be 1/2" (12.5mm) or 1/4" (6mm) on each side of the line the intersect and be of a smaller stroke width than the primary lines. For clocks, tick marks should extend from 3/16" (4.5mm) to 1/4" (6mm) on each side.
• Lead lines should be the least significant line (the lowest stroke width) in the graphic length 3/4" (20mm) to 1.5" (37.5mm)
• Lead lines should touch the component it identifies, and the other end should be at least 1/8" (3mm) from the associated braille label.
• Lines (especially lead lines) should be kept straight if possible to make for easier reading.
• Arrow heads are typically more legible if they are left open
• Grid lines should have a smaller stroke width than other information on a graph and are recommended to be 3/8" (10mm) apart to not be confused as a texture
• Axis lines should be thicker than grid lines and have an arrowhead if they have one in print.
• Points should be at least 1/4" (6mm)
• Labels, placed a 1/8" (3mm) - 1/4" (6mm) from other components or lead line
• Labels, have a 1/8" (3mm) margin in an area texture

Braille Size and font

The BANA document for braille sizing considerations for embossed documents and signage gives a good idea of minimum and maximum dimensions for braille on tactile graphics. Due to the resolution of 3D printed braille it may not be achievable using a 3D printer, that said larger braille than the maximum dimension cited by BANA has proven to be tactually legible in trials.

We have found that the public domain Braille Kiama font works well for 3D printing. The dot sizes are smaller than other braille font sizes and allow for more variation in spreading with different nozzles and slicer settings on different 3D printers.

Currently, the 35-37pt font sizes (design actual 3D printed sizes may vary) are recommended for achieving readable results with the Braille Kiama font. This is a 50% increase from the typical embossed/ swell font size which is usually around 24pt. Anything smaller is illegible and difficult to print and anything too much larger is more difficult to accurately and efficiently read. For a more in depth and detailed discussion of dimensions, please see the Braille page of the wiki

The font DejaVu Sans includes square braille dots (instead of the common round dots) that can reduce the computer workload when rendering 3d models. We have not found any readability problems in initial tests with square dots.