SYMMETRY

This function allows the user to define the symmetrical die by mirroring the available half or quarter about a symmetry-plane.

The DIE needs to be defined in the database in order to define the symmetry plane. If there is no part defined for the die, a DYNAFORM QUESTION window as shown in Figure 6.1.11 will appear.


Figure 6.1.11 DYNAFORM QUESTION window

Select YES, and the current part will be assigned to the die and the function will continue. Selecting NO will exit the function. See Figure 6.1.12.

Figure 6.1.12 Symmetry window

Eta/DYNAFORM51 supports the following four types of part geometry.

NO SYMMETRY (Default)

This option is selected as the default. If the function is toggled ON, other functions in Figure 6.1.12 will be disabled.

SYMMETRY

The part is defined as symmetrical.

HALF SYMMETRY INPUT

Only one half of the part geometry is available. The program will mirror the half part about the symmetry plane to form the complete part.

QUARTER SMMETRY INPUT

Only one quarter of the part geometry is available. The program will mirror the quarter part about both symmetry planes to form the complete part.

There are three types of symmetry that can be defined by the SELECT POINTS button.

X-Z PLANE


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

Y-Z PLANE

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

TWO-XY-POINT

The symmetry plane is normal to the XY plane of the Global System and through the selected two points. The user must select two points. The first point defines the location of the symmetry plane, and the second point determines the direction of the symmetry axis.

If the nodes at the plane of symmetry are not perfectly collinear along the symmetry plane, use ALIGN NODES function to correct the problem. When the part is defined as Half Symmetry or Quarter Symmetry, DYNAFORM will activate the ALIGN NODES function. The user can define the tolerance in the dialog window to align the nodes along the line of symmetry. The program will show the result of the align nodes operation and prompt the user for acceptance.

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). The other symmetry axis is vertical to the first plane and through the second symmetry axis.

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

Follow the below steps to design the symmetrical die.

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

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

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

Figure 6.1.13 Half Symmetry Part With X-Z -Plane

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

5. Click MIRROR GEOMETRY SYMMETRY, then select the part as shown in Figure 6.1.13. The result is shown in Figure 6.1.14.

Figure 6.1.14 The Result of Mirroring

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