LOCAL COORDINATE SYSTEM

eta/DYNAFORM refers to the local coordinate system to translate, rotate, mirror, copy, and generate points, lines, or nodes. When such a function is selected, the program will automatically prompt the user to generate a local system designated as the UVW coordinate frame. The LCS dialog window will be displayed (Figure 2.5.1). The user can create a new LCS or select a system as the current LCS by selecting GLOBAL, CURRENT LCS, LAST, or VIEW DIRECTION.

Figure 2.5.2 LCS

GLOBAL

Defines the global coordinate system as the current local C. S.

                              CURRENT LCS

Creates a local coordinate system as the current local C. S.

LAST

Defines the last coordinate system as the current local C. S.

                     VIEW DIRECTION

Defines the view directions as the W-Axis of the current local C. S. The user can select or define a point as the origin, or the origin of the global coordinate system can be the origin of the current local C.S

There are two ways to create a LCS based on whether the DEFINED BY 3 LOCATIONS toggle is checked.

1. CHECKED

The user can select one, two, or three points/nodes to create a system. To select a node, choose NEAR NODE. To select points, choose NEAR POINT.

  • ONE POINT

    • Select a point and choose OK. The created LCS has an origin at the selected point and is a translation to the origin of the global system.

  • TWO POINTS

    • Select two points and choose OK. The first point is the origin. The W-axis is the vector from the first point to the second point. The LCS is a translation and a rotation from X to U of the global system.

  • THREE POINTS

    • Select three points P1, P2, and P3. The point, P1, is the origin. The vector, P1-P2, is the U-axis. The cross product of U and the vector, P2-P3, is the W-axis. The V-axis is determined by the cross product of W x U.

    2. UNCHECKED

    DEFINE ORIGIN, U-AXIS, V-AXIS, and W-AXIS will be activated. To create a system in this case, the user needs to define an origin and axis. The LCS system will be a translation and a rotation of the global system.

  • Select DEFINE ORIGIN, and The INPUT COORDINATE dialog will appear. Select a point or node as the origin, and then select OK.

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  • Select one of the AXIS buttons to define the axis in the LCS dialog.

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  • Select BY POINT or ALONG AXIS from the U/V/W AXIS dialog (Figure 2.5.2) to define the axis. If BY POINT is selected, select a point in the display window to define the vector for the desired axis. If ALONG AXIS is selected, a dialog is displayed. The choices are ALONG X, ALONG Y, ALONG Z, ALONG U, ALONG V, ALONG W in the next dialog window. Select one, and then select DONE.

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  • Select OK from the AXIS dialog.

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  • Select OK from the LCS dialog.

    • Note: If the local coordinate system is not acceptable, use the NO button to reject and redefine the coordinate system.

  • The coordinate system is displayed.

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    Figure 2.5.2 Define W Axis