Compliant mechanism

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• Compliant mechanism design Facts of Mech
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• Compliant precision lathe

• Spring Stiffness
  • Stiffness can be said as the derivate of the force with respect to the deflection. In a linear spring, this deflection will be a straight line.
  • Ways to affect the stiffness,
    • Topology
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    • Geometry, making the blades thinner, longer and wider.
    • Material, Making the spring out of more compliant materials.
  • Non linear springs
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    • Even though they can be considered linear, after certain deflection, the stiffness begins to increase appreciably.
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    • The stiffness changes almost immediately as the beams have to stretch and bend as they deform.
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    • Some springs can be designed to reduce the stiffness as they buckle.
    • Most metals exhibit a linear stress strain relationship, but some elastomers have non linear elastic properties that change as the material is deformed. If we combine the stiffness properties of a design with a complementary material we can alter the design to have optimal stiffness along the range of motion.
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    • The nonlinear elastic properties of the spring are canceled by the nonlinear properties of the material.
  • Elastic strain Energy
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    • Under elastic conditions and given the material is not permanently damaged, all the work under the force displacement graph is said to be stored in spring as Elastic strain energy.
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  • Bi Stable switch
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    • The stiffness of the two elements can be added together because they are parallel, ie they experience the same displacement of the shuttle.
  • Axiomatic design
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    • Functional parameter only affect one area of the design parameter and the requirements are uncoupled from the design parameters.
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    • Compliant systems are inherently nonlinear and optimizing for all the variables is difficult and time-consuming. In nature, all systems are coupled and influence one another.
    • For eg, if we wanted a circular motion about an axis, its easier to use rigid bodies and put a pin joint there, if we were to make it compliant then it becomes a non linear problem where the center of rotation will depend on the force, location and the material.
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    • Compliant clutches.
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    • 360 Robot joint
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      • These are rigidly constrained in all directions but offer zero stiffness in rotation. Used for robot joints. These can be taken a step further with engineered materials.
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    • Over running clutch
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    • Bi Stable Switch
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    • Lamina Emergent Systems
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      • Making things in 2D that can assemble on fold into 3D shapes.
  • Flexure
    • A flexure is a mechanism consisting of a series of rigid bodies connected together by compliant elements that is design to produce a geometrically defined motion upon application of force. - Stuart Smith
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tags: #Mechanical #Compliant mechanism #Machine Design

Compliant mechanism