What is Degree of Freedom (DOF), how many types are available, and what is the 3-2-1 rule?
A kinematics and fixture design question essential for manufacturing and robotics.
Why Interviewers Ask This
DOF determines how a part can move. The 3-2-1 rule is fundamental for locating parts. Interviewers check your grasp of fixture design principles.
How to Answer This Question
Define DOF as independent movements (6 in 3D space: 3 translation, 3 rotation). Explain the 3-2-1 principle: 3 points on primary plane, 2 on secondary, 1 on tertiary to fully constrain a rigid body.
Key Points to Cover
- 6 Degrees of Freedom
- 3-2-1 Locating Principle
- Fixture stability
- Constraint logic
Sample Answer
Degree of Freedom refers to the independent movements a rigid body can make, totaling six in 3D space (three translations and three rotations). The 3-2-1 rule locates a part by constraining 3 degrees of freedom on the pr…
Common Mistakes to Avoid
- Miscounting DOFs
- Confusing 3-2-1 with 3-3-3
- Not explaining datum planes
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