You can position a datum plane by selecting any plane on the model (including another datum plane) and specifying an offset from the selected plane; you can specify the offset by entering a value or selecting a point.
To create a datum plane offset from a selected plane:
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 plane 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 Plane.
The Method list indicates the methods you can use to create a datum plane.
From the Method list, select Offset from plane.
From the part or assembly in the current viewport, select a plane.
From the buttons in the prompt area, select one of the following:
Enter Value
An arrow appears, indicating the offset direction.
Click Flip to reverse the arrow, if necessary. Click OK to accept the indicated offset direction.
In the text field in the prompt area, enter the offset from the selected plane. The offset can be positive or negative. A positive value offsets the datum plane in the direction indicated by the arrow.
Select Point
From the part or assembly in the current viewport, select a point to define the offset from the selected plane.
The datum plane appears. You can modify the position of the datum plane by selecting FeatureEdit from the main menu bar and modifying the value of the offset.
