Multiple design iterations were required to achieve a 3D tagging system that repeatedly and easily, snapped onto the head of a t-pin. The 3D tagging system needed to be easily removable to facilitate the frequent replacement of the T-pin necessitated by corrosion created by the exposure to embalming fluid.
Autodesk Fusion 360® (Autodesk, San Rafael, CA, US) three-dimensional modeling software was used to design the prototypes. Given the design requirement easy visual differentiation of the 3D tagging system, a contrast color palette of white lettering on a black background, and red lettering on a white background were selected.
T-Pin Design
Design 1 - Annular Snap Joint
The first design iteration, featured a two-part tag, consisting of a top and bottom, where the pin would be inserted from above (Fig 1: A.1). The lid would then be placed on the top, snapping into place, trapping the pin in position (Fig 1: A.2). A raised surface on the outside of the lid provided a level of friction to aid in removal of the top. This model failed as the annular design, with small ridges inside made it difficult to snap the lid into place, without simply snapping off the ridges. In addition, the longevity of this design was doubtful (Fig 1: A.3). Design 1 was eliminated for the reasons given above.
Design 2 - Flanged Annular Snap Joint
A modified version of Design 1 was created to reduce the force needed to snap the lid into place (Fig 1: B.1). This featured cutout flanges (Fig 1: B.2) to allow the lid to flex while snapping into place. Due to the small size of the tags, printing these flanges proved structurally unreliable and resulted in a high breakage rate under the pressure of lid placement (Fig 1: B.3). Design 2 was eliminated for the reasons given above.
Design 3 - Press Fit Tag
A complete redesign of the prototype incorporated a press-fit design, with paired projections on the top section (Fig 2: A.1) and two matching indentations to receive them on the base (Fig 2: A.2). Due to the print tolerance, specifically the XY-axis resolution, of the desktop printer, it proved unreliable to 3D print a top section that remained in place, whilst still being easily removable (Fig 2: A.3). Design 3 was eliminated for the reasons given above.
Design 4 - Toothed Pin Tag
It was determined that a single-piece design would be an ideal solution and allow for a thinner, lighter pin tag (Fig 2: B.1). In this iteration, the pin is inserted from below into a small channel on the tag (Fig 1: B.2). Small teeth snap into place between the bent portion of the metal structure of the T-pin. Challenges involved in reliably printing such small features, led to variance in the teeth and not every pin fitting securely into the channel (Fig 2: B.3). Design 4 was eliminated for the reasons given above.
Design 5 - Final Tapered Design
To minimize 3D print tolerance issues with small features, a tapered design was modeled. This solution featured a narrow opening on the bottom of the tag, that gradually widened to allow the pin to snap in place (Fig 3: A). This feature was easily printed and did not require any support material. Additionally, it allowed the tag to have smaller dimensions allowing unobstructed viewing of the anatomical structures below the pin. Printing of this design proved reliable for large batch printing. The circular section was created for the “A” tag (Fig 3: B) while a square section was used for the alternative “B” tag (Fig 3: C). The 3D printed tagging system requirements of the black & white vs red & white tags were then applied in the modeling software.
Non-Pin Version
A pin type tag is not always the best labeling method for anatomical structures. When labeling very small, or thin and long structures such as nerves and vessels, the common practice is to tie a small string around the structure and attach a label to this string. To accommodate this, a design was needed for a very light tag that could be tied to a string. The finalized tapered design was adapted to create a thin tag incorporating a hole to allow a string to pass though the tag, while maintaining the shapes and color schemes of the original 3D tagging system requirements (Fig. 4).
3D Printing Workflow
Model Placement
Due to the high production numbers of tags required, large batch printing became a necessity. The first step in the 3D printing process was to export the CAD files from Fusion 360 into the .STL file format. The next step was to import the .STL files into ideaMaker (v3.1.7.1850) slicing software from Raise3D and orient them to the printing surface. Parts were oriented flat with the letters facing up. In addition, to achieve optimal print surface quality with dual extrusion, a single vertical row was used (Fig. 5). This helps prevent the admixture of multiple colors, which can result from the idle extruder ‘oozing’ material onto the tag as the nozzle travels over it. Due to the fact that printer results vary largely by printer type and settings, printing multiple rows simultaneously may also be feasible depending on the equipment used. Thus, with the right equipment, higher volume production of the 3D tagging system may well be achievable.
Print Settings
After a series of test prints to determine the optimal print parameters, the following settings were chosen for consistent printing of the 3D tagging system; however, these settings can only be recommended as a guide as numerous factors affect print quality and these differ between 3D printer technologies and manufacturers. The prototype 3D tagging system was printed on a heated bed utilizing a raft. Table 1 shows the ideal print settings for a Raise3D N2 Dual extruder printer with Acrylonitrile Butadiene Styrene (ABS) plastic. A “wipe wall” and “wipe tower” were both used to ensure proper material flow when changing between colors. The same settings were able to be used for both the T-pin system and the adapted system to be used with a string.
Table 1
Primary Print Settings for a Raise3D N2 Dual extruder printer with ABS plastic
Setting
|
Value
|
Layer Height
|
0.15 mm
|
Left Nozzle Temperature
|
230 °C
|
Right Nozzle Temperature
|
230 °C
|
Bed Temperature
|
110 °C
|
Infill Density
|
20%
|
Shells
|
2
|
Platform Adhesion
|
Raft
|
Support
|
No
|
Wipe Wall # of Lines
|
2
|
Default Printing Speed
|
50 mm/s
|
Adaptation for Alternative Uses
The two-tag system was designed specific to our purposes due to the double nature of our anatomy exam station set up, this could easily be expanded with the addition of other shapes and colors. The design itself can be changed from text “A” and “B” to other numbers or symbols as required. These tags could be used within a large number of medical programs that use specimen-based examinations including but not limited to nursing, physical therapy and veterinary schools.