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Thankfully, the dimensions of a standard 8 ounce reusable plastic bag are roughly 16.5 cm x 14.9 cm, which is a small enough size to be used with materials provided. Every part of our machine was designed with the reusable plastic bag's size in mind. The DC 12V 100RPM Gear Motor used for the joystick controlled robot in Build Exercise #1 was repurposed for the sake of the motor in our bag opening mechanism. A number of elements from previous Build Exercises were repurposed not only due to our group having some familiarity with the pre-existing elements, but reusing pre-existing elements also helped in keeping the overall cost of the mechanism down.
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Instead, we settled on using a wooden box design that would both house the claw and its motor, as well as having a hook that could be used to hold up the reusable plastic bag, allowing it to be opened at numerous different orientations.
Figure #2.3: Initial wooden box design sketches
Using a hook-like mechanism placed within the wooden box, the reusable plastic bag could be first placed onto the hook, without needing to be orientated at any specific angle or direction, and the crank could be activated. At this point, the crank would then be able to slide across the box and latch onto the reusable plastic bag and exert , exerting a shear force on opposing sides of the bag , resulting which would result in the bag opening.