braille2

In accordance with an ongoing project between the University of Maryland and The Maryland School for the Blind, a full design of tactile graphics pages has been completed. Tactile graphics are pages created for the visually impaired. Textures are utilized to represent words, shapes and colors for those who cannot see a normal page.
This particular tactile graphics model focuses on the representation and comparison of butterfly species. This is used to help relate the general concept of what a butterfly is to the child who cannot see the creature. The concept of color is a focus of this model. Textures are chosen with qualities similar to those of the colors. The model can also be used to demonstrate the concept that butterflies are different in shape, size, and color.

The monarch and black swallowtail butterfly species were chosen for inclusion in the model. Both are familiar butterfly species, which feature significantly different colors and shapes. The monarch (Danaidae family) is observed to be very colorful, with wings featuring an intensely orange hue. The black swallowtail (Papilionidae family) is less extraordinary in its color. Its wings are mostly black, with dull yellow bands along the edges. The geometry of the swallowtail's wings features distinctive extrusions at the wingtips that the monarch lacks.

Figure 1: Monarch and Black Swallowtail Butterflies

Monarch Black & Swallowtail

http://monarchwatch.org/biology/sex.htm

http://mcnet.marietta.edu/~biol/butter/blacksw.html

Several steps are necessary to produce the braille page that the blind student will use. Once a design model is chosen, a Pro/ENGINEER® model of the part is created. This model is exported to a stereolithography machine, which generates a physical model of the computer model. This model can be used as a mold to produce Brailon thermoforms (the actual braille pages).

Textural Representation of Colors

The various colors will be represented by textures. Such textures attempt to relate their visual sensation of color to the blind student through tactile sensations. Thus, a striking, vivid color should have a sharp distinctive texture.

To prevent cluttering and confusion, the design is limited to the four main colors present on the butterfly species: red-orange, orange, black, and yellow. They will be represented by textures as shown in Figure 2.

Figure 2: Textural Representation of Colors

The red-orange color on the upper wings of the monarch is the most vivid and eye-catching color in the model. The texture should relate such a quality; thus, the individual nodes that represent red-orange are relatively thin and widely spaced. This texture feels relatively sharp and distinctive to the touch, consistent with the intensity of the color.

The orange texture is slightly less vivid than the red-orange. The nodes for orange are the identical size of the red-orange nodes, but are placed closer together, into distinct rows. The finger is able to glide across the surface of this texture more easily, yielding a less intense sensation. However, the texture suggests that the two colors are quite similar in nature.

The yellow texture of the swallowtail butterfly is composed of larger nodes that are relatively closely spaced. This texture is quite apparent to the user, yet it is not as sharp as the orange textures. The relative dullness of the yellow color, as it exists on the swallowtail, is demonstrated by the texture.

Black represents an essential absence of color; thus the color black is represented on the model by a flat raised surface. This will distinguish the fact that there is indeed a feature of note, but its color is not particularly eye striking.

Br aille Language

As the blind student can not read printed text, the familiar braille language has been established. The Internet Braille Wizard is a helpful tool provided online by Access 20/20, a company that produces braille transcriptions and audio tapes for the visually impaired. The Braille Wizard also provides instant braille transcriptions of words.

Proper formation of standard braille characters is necessary, so that the student can easily distinguish and recognize them. Each cell is approximately the size of a fingertip, so that the character can be distinguished quickly and easily (Burnham). A cell is created by a certain arrangement of nodes in a 3x2 matrix. Each node is raised 1/64" from the surface and features a rounded, dome-like top. (The Ingenious System of Louis Braille).

Figure 3: Braille Alphabet and Character Dimensions

The character signifies that the following character will be a capital letter. Thus, the word "Butterflies" would transcribe to braille as:

B u t t er f l i e s

Design Model

A basic design model can be formulated. The main page features the two butterflies with appropriate braille labels. The second page is a legend that identifies the textures by their respective color names. This will allow the blind student to attribute the particular color names with the butterfly species.

Figure 4: Design Model

This model will be utilized as a basis for the Pro/Engineer model, which will be used to produce the stereolithography model, which in turn will be used as a mold to produce the Brailon thermoform sheets.

Pro/Engineer Model

Integration of braille text and textured surfaces to the basic design model allows for creation of a Pro/Engineer model of the part. The part is dimensioned 7" high by 9" wide, allowing creation in the stereolithography (SLA) chamber and reproduction in the thermoform machine. The base thickness is relatively thin (1/8"), in order to minimize the time necessary for SLA construction while maintaining some degree of structural integrity.

Figure 5: Butterfly: Pro/Engineer model

Figure 6: Pro/Engineer model of legend

As the SLA molding is fairly thin, it is susceptible to breakage or warping when exposed to heat. Therefore, a Plexiglas base plate must be created and mounted to the SLA model. The SLA part mold features extrusions that allow it to be mounted to the base plate without impairing the surface quality. Any impairment of the model surface (i.e. a screw head or depression) would be transferred to the resulting thermoform. This could cause confusion for the blind student, who may mistake this surface imperfection for a feature of the part.

Figure 7: a) Pro/Engineer model of base plate b) assembly

The fillet radius at the corners of the SLA model correspond to the radius of the mill bit that will be used to machine the base plate. This will prevent excessive rework of either part in order to mate them effectively.

Figure 8: Mounting point design for SLA model

Stereolithography

Rapid prototyping methods allow for a complex design to be constructed directly from a computer model. The stereolithography machine is utilized in this instance to create a physical version of the Pro/Engineer model.

The Pro/Engineer model is initially exported in .stl format. A triangular mesh is created, similar to the finite element meshes created for ANSYS or other FEA software.

Figure 9: Pro/Engineer output mesh

Maestro® software is utilized to process the exported file for use on the stereolithography machine. The model is oriented to the position that is most suitable for prototyping and a support structure is automatically designed into model.

This file is then exported to the stereolithography machine (SLA-250/40) in the Advanced Design and Manufacturing Laboratory. The essential components of the SLA machine are a computer, a vat of resin, a support platform, and a laser beam. Based upon the part model, the computer directs the movement of the platform and laser. The part is built upwards, layer by layer. The platform is gradually lowered into the resin, one increment at a time (.006" for this model). At each step, the model geometry of that layer is solidified from the resin vat by the laser beam.

Figure 10: Stereolithography machine

The stereolithography modeling takes several hours to complete. After completion, the base structure can be cut away from the model and the part can be cleaned with alcohol. At this point, approximately 10% of the resin on the interior of the part has not fully hardened. It is necessary that the SLA model be held in a UV light chamber for a period of time to allow for complete hardening.

Figure 11: Complete butterfly stereolithography model

Figure 12: Complete legend stereolithography model

Thermoforms

Once both SLA models (butterfly page and legend) are complete, they are mounted to their respective base plates. For proper creation of the thermoform images, several small holes are drilled through the model and base plate assembly. These holes allow for some permeability of the mold. A vacuum force to be generated between the model and the Brailon® thermoform sheet in the thermoform duplicator.

Figure 13: Model assembly with holes drilled

The Brailon® Thermoform Duplicator consists of a vacuum tray and a series of heating coils. The mold (SLA model) is placed on the vacuum tray and a Brailon page is secured above it. The page is heated for several seconds under the heating coils. The coils are then removed and the suction pump operates briefly, allowing for the surface geometry of the mold to be transferred to the Brailon sheet.

Figure 14: Completed Brailon thermoform pages: a) main page b) legend

The final Brailon pages emerge as shown, ready for use by the blind student. They will be presented to the Maryland School for the Blind, who will determine the practical application. The pages are recommended for independent use or for inclusion in volumes concerning color or biology, and can be used at various grade levels.

Works Cited

Braille Alphabet and Numbers Used by the Blind. Flyer. The Maryland School for the Blind.

Burnham, Betsy. Tactile Media Coordinator. The Maryland School for the Blind. Correspondence. November 9, 1998.

Internet Braille Wizard. Access 20/20^®. http://www.access2020.com. November 23, 1998.

Monarch Watch. University of Kansas Dept. of Entomology. & University of Minnesota Dept. of Ecology, Evolution, and Behavior. http://monarchwatch.org. November 28, 1998.

Marietta College Biology Department. http://mcnet.marietta.edu/~biol/. November 28, 1998.

Magrab, Edward B. Integrated Product and Process Design and Development, Boca Raton, FL: CRC, 1997

The Ingenious System of Louis Braille. Author/Publisher unknown. Provided by Betsy Burnham, Maryland School for the Blind, November 9, 1998.

Tactile Graphics. Second National Conference booklet. National Braille Association, Inc. Rochester, NY, 1993.

Thermoform Brailon Duplicator Owner's Manual. American Thermoform Corporation, City of Commerce, CA.