Using a Line as a 'Symmetry Inference'
While there is no dedicated 'symmetry line' tool, as symmetry is technically and quantitively defined by Geometrical Dimensioning and Tolerancing (GD&T) principles and symbols, you may however add a line which only represents 'Implied Symmetry' - Examples are shown below.
Three ways to make a representative 'Implied Symmetry' line ( Third way preferred )
1. On the model, In a sketch, create a Layout line by checking the Create Layout Curves option.
A sketch construction line can also be used changing it after exiting sketch to a line, then to a layout line in it's properties. Select and change True > False
2. On a model, with a 3D line, create a Layout Curve line. ( If a line or construction line is used, change its properties as above)
3. On a model face in a drawing sheet view ( as shown ), create a Layout Curve line - this the preferred way due to the option of creating a line in the drawn view only
Now change its Line 'Style' properties
Adjust the length by dragging in a sketch plane
Note: Structure Browser listed in both the Model and Drawing Sheet, the curve line may have a separate independent style in Model and Sheet with renaming for identification.
Another possible problem with this symmetry line is with model changes - it will not automatically relocate if model features / faces are moved requiring probably separate repositioning.
Defining Symmetry using GD&T symbols - 2 ways
1. Annotation GD&T manual creation
2. Encoded GD&T logic
1. Using the built-in symbols / dialogue from Dimension > Annotate GD&T
2. Encode with GD&T semantic logic (defined by ASME Y14.5 GD&T (2009) standard and ASME Y14.41 containing additional requirements for tolerances defined in digital models
Please take a look at the GIF below for a demonstration of the application principle
Note: If a GD&T feature / face is moved, breaking a defined relationship, an error red X is shown next to the relevant symbol in the structure browser
If an incorrect symbol is used i.e a positional instead of a symmetry symbol, an error is also shown
Comments
2 comments
この例では、DSMのDrawingにおいて、円筒形の中心線を利用して、中心線が対称の中心線と表示する方法を紹介しているように理解しています。
では、DSMのDrawingにおいて、円筒のような形状ではなく、直方体( rectangular parallelepiped)に、対称の中心線を描く方法を教えてください。
Makoto Aihara
This article has been revised 25-07-21
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