You can position a rectangular, cylindrical, or spherical datum coordinate system by selecting two edges that define it. The first edge defines the X- or R-axis, and the X–Y or R-
-plane passes through the second.
To create a datum coordinate system defined by two lines:
From the main menu bar, select Tools
Datum.
The Create Datum dialog box appears. The dialog box outlines the types of datum geometry you can create.
Abaqus/CAE displays prompts in the prompt area to guide you through the procedure.
Tip:
You can also create a datum coordinate system using the 
tool, located in the module toolbox. For a diagram of the datum tools in the toolbox, see “Using the Datum toolset,” Section 62.2.
From the list of types at the top of the dialog box, choose CSYS.
The Method list indicates the methods you can use to create a datum coordinate system.
From the Method list, select 2 lines.
Abaqus/CAE displays the Create Datum CSYS dialog box.
From the dialog box, enter the name of the datum coordinate system.
To help keep track of your datum coordinate systems, Abaqus/CAE displays its name in the Model Tree. In addition, you can use the Model Tree to rename the datum coordinate system.
From the dialog box, select one of the following datum coordinate systems:
Rectangular: The X-, Y-, and Z-axes are aligned with the 1-, 2-, and 3-global axes, respectively.
Cylindrical: The R-, -, and Z-axes are aligned with the 1-, 2-, and 3-global axes, respectively.
Spherical: The R-, -, and 
-axes are aligned with the 1-, 2-, and 3-global axes, respectively.
From the Create Datum CSYS dialog box, click Continue.
From the part or assembly in the current viewport, select a straight edge that will define the X- or R-axis of the datum coordinate system.
Select a straight edge that will lie in the X–Y or 
-plane.
The datum coordinate system appears. You cannot move or rotate a datum coordinate system.
