Exact constraint design

Exact constraint design, see also [Skakoon2008], is one of the most important lessons I had to learn in my career as a Mechanical Engineer. I had to learn it the hard way by making many mistakes. In short:

1. Never limit more degrees of freedom than absolutely needed, when mating parts, with an absolute maximum of 6 namely 3 translational and 3 rotational degrees of freedom.

2. For each free degree of freedom of movement (R=Rotation, T=Translation) needed between two parts one less degree of freedom needs to be constrained. The sum of constrained and free degrees of freedom of movement is always 6, namely 3 translational and 3 rotational degrees of freedom of movement.

3. Use force-closure to mate parts, never use form-closure, thus never use matching contra-forms to mate parts.

Mechanical products very often consist of many parts which need to be assembled or need to move/rotate relative to each other. Therefore, these parts need to be:

1. positioned relative to each other and if needed

2. fixated relative to each other or

3. they need to move in 1 or more directions relative to each other.

For the Exact Constrained Design generic cases see the attchment: GenericCasesExactConstrained.pdf.

See the section: Exact Constrained Examples for examples.

Take home message: Always use Exact Constraint design and force-closure to mate parts

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