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Enhancing Design with Compliant Kinematic Couplings: Balancing Degrees of Freedom

This document discusses the application of compliant kinematic couplings (KCs) in design, focusing on the addition and removal of Degrees of Freedom (DOF) to achieve better coupling performance. It highlights that KCs may struggle to form seals, and adding compliance can facilitate this. Important considerations include managing the compliant direction carefully to avoid sensitive areas. The paper details design metrics such as stiffness ratios, actuation loads, and tolerances, providing insights into various applications, including assembly and casting.

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Enhancing Design with Compliant Kinematic Couplings: Balancing Degrees of Freedom

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  1. PARTIALCONSTRAINT

  2. Ball Seated in V Mold Halves Flexures Adding and taking away constraints • It may be helpful to add/remove DOF in coupling applications • For instance, KCs can not form seals • We can add compliance to KCs to allow this to happen • This is equivalent to adding a Degree of Freedom • Care must be taken to make sure • compliant direction is not in a sensitive direction • Parasitic errors in sensitive directions are acceptable

  3. Stiffness ratio • Actuation loads should be: • Applied through center of stiffness • In compliant direction • Error loads are often proportional to applied loads • Example: Bolt head friction • TB ~ FB RBm • Design for ksensitive >> knon-sensitive • Practical metric is stiffness ratio: • ksensitive >> 1 • knon-sensitive

  4. w2 t2 Stamped compliant kinematic couplings Characteristics Stroke ≤ 0.25 inches Repeatability 5 -10 microns Ball movement in non-sens. direction Applications/Processes 1. Assembly 2. Casting Design Issues (flexure) 1. Kr ~ 2. Tolerances affect Kr Cost $ 10 - 200 U.S. Patent 5, 678, 944, Slocum, Muller, Braunstein

  5. Kguide Kspring Integral spring compliant kinematic couplings Characteristics 1. Repeatability (2.5 micron) 2. Stroke ~ 0.5 inches Applications/Processes 1. Assembly 2. Casting 3. Fixtures Design Issues (flexures) 1. Kr = 2. Press fit tolerances Cost $ 2000 U.S. Patent 5, 678, 944, Slocum, Muller, Braunstein

  6. Plastic compliant kinematic couplings Characteristics 1. 180 microns 2. ~ 0.125 inches 3. 1 Time Use Applications/Processes 1. Sand Casting • Design Issues • Loose Sand • Kr application specific Cost 1. Modify Pattern 2. Purchase Balls 3. Tie Rods U.S. Patent 5, 769, 554, Slocum

  7. Stamped Springs Plastic Experimental results

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