PUPS 1: Pliers

For this problem set, I considered a basic pair of pliers and emphasized durability and robustness in use for the design.

Free-body diagrams and error motion identification for pliers
FRDPARRC Table for a pair of pliers

One piece of feedback that I received from the peer review discussion (see below) was that the clamping force exerted by the jaws and the amount of torque that can be transmitted are related functional requirements. While this is true, my original rationale for separating the two was to try to capture the different things people do with pliers. In the ensuing discussion, I thought of another possible loading configuration when one tries to pull a nail or staple by gripping and twisting. This induces bending and torsional loads on the jaws and introduces error into jaw alignment. In fact, I now remember that I have done this to a pair of cheap pliers I own (see below). This is a reminder that we need to consider not just intended loading configurations, but also configurations that result when the machine is abused/misused!

Permanently sprung plier jaws; this permanent deformation adds to the misalignment caused by pivot clearance! (Photo by Shien Yang Lee, CC-BY-SA 4.0)

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