Tactile Graphics Introduction
    Most learning tools for sighted people are designed with a high degree of visual content.  Students without the ability to see must use their other senses to learn.  Betsy Burnham of the Maryland School for the Blind develops graphical materials for visually impaired Maryland students who mainly use touch and hearing to learn.  Burnham creates textbooks that contain textured pictures labeled with Braille.  Our design team agreed to create a tactile graphic to be included in one of these special textbooks.
    The technology for creating tactile graphics includes creating a Computer Aided Design (CAD) 3-D drawing, creating a solid mold, then mass-producing sheets from the mold.  The textured sheets are approximately 12" by 10" and have an approximate maximum texture height of 0.5".   The technology for the solid model is laser stereolithography using light sensitive resins that are scanned and solidified in the shape of the mold.   Then a thermoform machine can make a 3-D copy of the pattern.
    The textures on these sheets are required to be simple in design.  The students learn by being able to touch and recognize differences in texture and protrusion.  A broad spectrum of students may use the graphic including some blind students who also have learning disabilities.

Project Objective
    Our goal is to develop a method for creating tactile graphics and apply this to the rendering of the digestive system into a solid 3D mold that can be used to create thermoform sheets.  This schematic is destined for use in Maryland Public School and at the Maryland School for the Blind.  We will create a CAD drawing of the digestive system, from this make a mold, and then create sheets for a textbook from the mold.
    The difficulties in meeting our objective are related to the unusual geometry of the necessary 3D model.  Our team has been trained to create engineering drawings of regular geometry including flat surfaces and round or rectangular outlines in Pro/Engineer.
    Our drawing of the digestive system includes curved outlines and irregular textures.  In order to meet our objectives, we had to learn how to create irregular geometry and to add texture to an ordinarily flat surface.  Parametric Technologies Inc. (PTI) has an online customer support database that we are using to learn how to the draw the digestive system.
    Before us, other students have created tactile graphics for the Maryland School for the Blind.  In addition they learned about the use of the stereolithograph and Brailon Thermoform Duplicator.   We have relied on the previous research, as well as our own to learn how to use these machines.
 
Methodology
    The first step completed for this project was a trip to the Maryland School for the Blind in Baltimore Maryland.  The trip to the School for the blind served many purposes with this project.  Primarily, it gave the project some direction for the group to move forward with.  The schools director, Betsy Burnham requested that tactile graphics be made for the human digestive system.  Betsy Burnham talked with the group at length about the purpose the graphics would serve, and how they would be perceived through the fingers of blind children.  In order to do this, she showed some examples of other tactile graphics.  To help us to understand how blind student see the graphics, she had us close our eyes and feel one of the graphics.  Ms. Burnham discussed which parts of each graphic were more easily read, and what standards, if any, existed for the graphics.  In addition she talked to us about Braille, how it translates to words and the standard way that Braille is made.
    After speaking with Betsy Burnham we began our preliminary drawings in Pro/Engineer.  We made transparent slides of the digestive system schematic and taped them to a computer screen.  We traced the digestive system using the SPLINE command in Pro/Engineer.  The SPLINE command allows the user to draw free hand, only dimensioning the starting points position within the datum plane.  Using this we created two Pro/Engineer drawings.  The first drawing is of the entire body with a square denoting a "blow-up" region (figure 1).  The square is used because there is too much information in the drawing to fit in one page.  Therefore the square tells the person to go to the next page, this is the second drawing of the "blow-up" region (figure 2). Splitting the drawing into two parts allows for greater detail, making the schematic easier to understand for blind students.  The body outline (figure 1) was created using the SWEEP command, while the internal organs (figure 2) were created using the PROTRUSION command.  Different protrusion heights were used to help differentiate between organs.

 

Figures 1 & 2: Digestive system schematics created in Pro/Engineer.

    After the basic schematic is drawn in Pro/Engineer, it was modified to include textures.  This was completed using cut, extrude and the surface command from the advanced geometry menu.  The surface command allows the user to first create a grid over the desired part and then raise or lower individual points in the grid.  See Figures 3 & 4 below of the textured Pro/Engineer drawings.

    After completing the textured drawings they were exported to .slt format in Pro/Engineer.  The .slt drawing files were then analyzed using Maestro.  Bing Cheng (see photograph), a mechanical engineer who graduated from University of Maryland graduate school in the summer of 1999, served as a source of information regarding the Maestro program and stereolithography.  Maestro is the computer program that was used to interface the computer drawings with the SLA-250/40 Stereolithograph machine.  While in Maestro the drawing files are first analyzed to ensure that no errors are present.  After the analysis is completed, a support structure is added to the drawings.  See figure 5 for a picture of the body mold with support structures analysis in Maestro.  The support structure and part are then sliced to create layers. The layer files are then ready to be used by the stereolithograph machine.

    The files created in Maestro were then loaded onto the computer that controls the Stereolithograph machine and the tactile graphics molds were created.  See Figure 6 below for a schematic of the stereolithograph process.
 

    The next step in creating the stereolithograph molds is to remove the support structure from the mold.  See figure 7 and 8 for photographs of removal of the support structures.  After the support structure has been removed the part must be further solidified in the ultraviolet oven.

    Braille labels for the digestive system parts are then added to the mold.  To prevent warping, the stereolithograph mold with the labels will then be inserted into an acrylic frame.  Small holes will then be drilled through both the acrylic frame and the stereolithograph mold.  Finally, the tactile graphics sheets will be created using the Brailon Thermoform Duplicator. This machine will heat up the thin plastic sheets and use a vacuum to wrap them around the solid mold.  The thermoform sheets will then hold the shape of the mold and then serve as a useful tactile graphic.

Summary
    Tactile graphics are a learning tool to help blind students learn by using their hands.  Betsy Burnham of the Maryland School for the Blind pointed out several factors for consideration in the design of tactile graphics.  It is important that the graphics be easily readable.  There are several ways to help make graphics easier to read.  These methods include using leaders to guide students’ hands to features of the graphics, marking the top of the page with a horizontal bar, and using different textures or heights to differentiate between features.  Ms. Burnham requested that textile graphics of the human digestive system be created.  She provided a depiction of the digestive system as a starting point for the tactile graphic creation.  From the depiction a model is created in Pro/Engineer which leads to the production of the mold for the final product.