Digital Designs and Scientific Hardware - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 166

FIGURE 6.2 Screenshot of the parametric gasket code is the Thingiverse Customizer App.
Finally, the code is set up as a module so others can copy it and put it directly into a more
complex design. This way anyone wishing to make a custom gasket can adjust the size in the
interface and does not even need to go down into the code. This may seem like overkill for
this simple design, but as the code becomes more complex, this is a really nice favor to do for
those who may need it in the future (may be even yourself).
To illustrate the utility of parametric design for a scientist, consider an optical chopper
wheel, which modulates the frequency of a light beam. For a given chopper wheel setup, the
target frequency can be adjusted by the number of slots in the chopper wheel. Normally, this
involves the separate purchase of a new wheel for each experiment, and the experimenter
does not always know beforehand what the optimal operational frequency is for a given ap-
plication. A parametric design from OpenSCAD is shown in Figure 6.3 , where the slot num-
ber for an open-source optical chopper wheel 6 has been adjusted by changing a single vari-
able in the code from (a) 10, (b) 15 and (c) 60 slots providing ranges of chopper frequency
of 20 Hz-1 kHz, 30 Hz-1.5 kHz, and 120 Hz-6 kHz, respectively. OpenSCAD directly exports
the geometry to an STL file, which is used for 3-D printer open-source slicing programs (e.g.
Skeinforge, 7 Cur a 8 or Slic3r 9 as discussed in the last chapter), which is in turn transformed to
g-code, which provides the vectors for tool path (3-D printer extruder head).