SYMMETRY

 

This function allows the user to mirror the symmetrical die about a symmetry plane.

 

The user has to define a part as DIE prior to defining the symmetry plane. If the DIE is not defined, a eta/DYNAFORM QUESTION dialog box as illustrated in Figure 6.1.11 is displayed when the function is activated.

 

Figure 6.1.11 DYNAFORM Question dialog box

 

If YES is selected, current part is set as DIE and the user will continue to define the symmetry plane using the functions provided in SYMMETRY dialog box as illustrated in Figure 6.1.12. 

 

If NO is selected, eta/DYNAFORM will abort the operation.

Figure 6.1.12 Symmetry dialog box

 

Four geometry options are available in the SYMMETRY dialog box. There are described as following:

 

          NO SYMMETRY (Default)

This is the default option. All other functions provided in the SYSMMETRY dialog box is disabled.

 

          SYMMETRY

         The part is defined as symmetrical.

 

          HALF SYMMETRY INPUT

Only one half of the part geometry is available. The function will mirror the other half of the part about a symmetry plane to create a complete part.

 

          QUARTER SMMETRY INPUT

Only one quarter of the part geometry is available. The function will mirror the other three quarters of the part about two symmetry planes to create a complete part.

 

 

There are three types of symmetry options available. There are described as the following:

 

X-Z PLANE


The symmetry plane is parallel to the XZ plane of the Global Coordinate System. The user must select two points to define the XZ plane. The first point is used to define the location of the symmetry plane, while the second point is used to define direction of the axis of symmetry.

 

         Y-Z PLANE

 

The symmetry plane is parallel to the YZ plane of the Global Coordinate System. The user must select two points to define the YZ plane. The first point is used to define the location of the symmetry plane, while the second point is used to define direction of the axis of symmetry.

 

         TWO-XY-POINT

 

The symmetry plane is normal to the XY plane of the Global Coordinate System. The user must select two points to define the XY plane. The first point is used to define the location of the symmetry plane, while the second point is used to define direction of the axis of symmetry.

 

If the nodes at the plane of symmetry are not collinear along the symmetry plane, the ALIGN NODES function can be utilized to correct the problem.  When the part is defined as Half Symmetry or Quarter Symmetry, eta/DYNAFORM will activate the ALIGN NODES function.  The user can define the tolerance input field to align the nodes along the line of symmetry.  eta/DYNAFORM will show the result from the operation and send the user a message to confirm the operation.

 

If QUARTER SYMMETRY INPUT is selected, there are two symmetry planes and two symmetry axes. One symmetry axis is vertical to the first and through the base point (first selected point), while the other symmetry axis is vertical to the first plane and through the second symmetry axis.

 

If HALF SYMMETRY INPUT or QUARTER SYMMETRY is selected, the MIRROR GEOMETRY button will be activated. This function allows the user to select elements which will be mirrored about the symmetry plane(s). The UNDO button is used to undo the mirror operation.

 

The steps needed to define a symmetrical die are listed as the following:

 

1.     Read in the symmetrical geometry, mesh it and assign it as DIE.

2.     Select a geometry type, for example, HALF SYMMETRY.

3.     Select a symmetry type, for example, X-Z PLANE.

4.     Using the SELECT POINT button to select two points to define the symmetry plane and the axis direction.

 

Figure 6.1.13 Half Symmetry Part With X-Z Plane

 

5.     Click on the MIRROR GEOMETRY SYMMETRY button, following by selecting the part as illustrated in Figure 6.1.13. The mirror result is illustrated in Figure 6.1.14.

 

 

Figure 6.1.14 The Mirroring Result

 

NOTE: Once the symmetry axis is defined, the created binder will be symmetrical and consist of two surfaces as shown in Figure 6.1.15.

Figure 6.1.15 Binder With Symmetry Plane