Constant-Force Mechanism

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This mechanism is designed to represent a constant force mechanism, which provides a constant force through a specific range of motion. This design uses crank-slider compliant mechanism configuration with nested cams. The mechanism has a cantilever spring which deflects and travels along a cam (rigid component). As the cantilever spring deflects, a resistance force is produced. The predetermined path of the rigid component is a function of the displacement, deflection, and resistance to provide the constant force. The mechanism compensates for the varying resistance from the springs by varying the mechanical advantage, where mechanical advantage is defined as a ratio of the mechanism’s output force to input force (see more details below).

The version available for download has been simplified to allow for ease of 3D printing and assembly and is meant to portray the overall concept, while not being an optimized constant-force mechanism. This 3D printable version is a single part that can be printed four times and easily snap together without the need for any additional materials such as bolts, bearings, etc..

Applications include electrical connectors, exercise equipment, microscopic devices, and robotic end-effectors. (see more details below).