Expanding Tolerance Analysis for a Robust Product Design Expanding Tolerance Analysis for a Robust Product | Page 4

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Expanding Tolerance Analysis for a Robust Product Design

Fig. 4. Critical Surfaces of a locking mechanism
Fig. 2. Conceptual Design of an oven

Eventually, the concept design needs to be created in a
CAD system. During this stage, a review of basic tolerance
assumptions can occur.

Surfaces such as the pin’s outer surface that touches a hole,
or the inner surface of a whole that surrounds a pin are
highlighted.
After the critical functions are identified, equations can be
used to translate the model into a mathematical representation
of the surfaces. For a pin in a hole, the equations would be:

3.3. Identify Critical Functional Features
The progression from a conceptual design to detailed
design begins with the identification of the critical function
features. Many features are cosmetic in nature, such as the
roundness of a door handle. But the critical functional features
would include the hole where a spring attaches, or the gear
surfaces that interact with each other.
In this example, a simple locking mechanism is shown in
the whole parts:

The translation into mathematical representation leaves a
visual of the model that looks more like this:

Fig. 3. Solid model of a locking mechanism

As the critical functional features are identified, the
representation of the assembly looks more like this:

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