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Thread: Driving vs. Driven Dimensions

  1. #1
    Associate Engineer
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    Driving vs. Driven Dimensions

    Our company policy, for a very long time, is to use only driven dimensions on 2D drawings. Now that we are starting down the Model Based path, that is being questioned. I've been tasked with investigating the pros and cons of each of the options.

    Does your company use driving or driven dimensions and why?

    Thanks,
    ~Kevin

  2. #2
    Lead Engineer Cake of Doom's Avatar
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    I'm not sure there is a case for driving Vs. driven dims. Each has it's own use under it's own set of circumstances.

  3. #3
    Administrator Kelly Bramble's Avatar
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    In general, 3D CAD model driving dimensions are placed and used to best control and define the model geometry. Dimensions used on 2D drawing or with 3D model definition are used to define the end item manufacturing requirements. Most often the 3D CAD model driving dimensions are not what represents the end item manufacturing, function, fit and form requirements.


    Quote Originally Posted by kcampbe View Post
    Our company policy, for a very long time, is to use only driven dimensions on 2D drawings. Now that we are starting down the Model Based path, that is being questioned. I've been tasked with investigating the pros and cons of each of the options.

    Does your company use driving or driven dimensions and why?

    Thanks,
    ~Kevin
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  4. #4
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    OK, I should have been more precise. I'm talking about machined parts. Parts that can be manufactured on a mill or lathe. No free form surfaces, injection molding or additive manufacturing.
    ~Kevin

  5. #5
    Administrator Kelly Bramble's Avatar
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    The dimensions and tolerances specified are what manufacturing/production builds to and should reflect end-item requirements in terms of fit, form and function. CAD is a tool - mostly for productivity. Whatever works best for your organization to communicate effectively to production and maintain design documentation integrity is the goal.

    The cad 3D model usually drives the geometry on the 2D engineering drawing.. The dimensions and tolerance on the engineering drawing usually are driven by the 2D graphics.

    What are you looking for?
    Quote Originally Posted by kcampbe View Post
    OK, I should have been more precise. I'm talking about machined parts. Parts that can be manufactured on a mill or lathe. No free form surfaces, injection molding or additive manufacturing.
    ~Kevin
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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