Changing a Sketch Support  

This task shows you how to change the position of a sketch by changing its support. Changing a sketch support amounts to editing the absolute axis definition of the sketch.
Open the Change_Sketch_Support.CATPart document.

In this scenario, you will edit the absolute axis definition of Pocket.2/Sketch.3 by making it associative to Pocket.1. This will ensure that, when moving Pocket.1, Pocket.2 follows Pocket.1 without requiring you to edit the geometry of Sketch.3.

  1.  From the specification tree, right-click Sketch.3. and select Sketch.3 object > Change Sketch Support....
    If a message appears, informing you that if you change its position, the sketch may become inconsistent or over-constrained, simply click OK.
    The Sketch Positioning dialog box appears.

  2. If the Move geometry option at the bottom of this dialog box is checked, uncheck it. This will prevent the geometry from moving when performing the next operations in the dialog box.
    In the Type field in the Sketch Support area, three options are available:

    • Positioned: positions the sketch using the origin and orientation of the absolute axis.
    • Sliding: default type used for non-positioned sketches (i.e. when you edit a non-positioned sketch, this option will be selected by default, as is the case in our example). This option is mainly used for compatibility purposes, and to enable you to turn non-positioned sketches into positioned ones.
      With the Sliding option, the sketch is not positioned, i.e. the origin and orientation of the absolute axis is not specified. As a result, its absolute axis may "slide" on the reference plane when the part is updated.
    • Isolated: isolates the sketch in order to break all absolute axis links (support, origin and orientation links) with the 3D or to solve update errors. Only the 3D position will be kept, to ensure that the sketch does not move. With the Isolated option, you cannot define the sketch support, origin and orientation.
  3. Select the Positioned option, and make sure Pad.1/Face is selected as the reference element for the sketch support (Reference field).

  4. At this point, check the Move geometry option to specify that, from now on, the geometry should be moved when the sketch position is modified.

  5. Check the Swap box to swap H and V directions. The new sketch position is previewed in the geometry area.

    You are now going to make the absolute axis associative with Pocket.1.

  6. Uncheck Move geometry once again to ensure that the geometry does not move according to the newly defined axis.

  7. In the Type field in the Origin area, select Intersection 2 lines.

  8. You will now specify the reference element for the origin. To do this, make sure the Reference field is active, and select a horizontal edge of Pocket.1 as shown below.

  9. Now, select a vertical edge of Pocket.1 as shown below.

  10. In the Orientation areas, leave the Type field set to Implicit and the Reference field set to No Selection. For more information on the other options available in the Origin and in the Orientation areas, refer to Creating a Positioned Sketch in the Sketcher User's Guide.

  11. Click OK.
    The absolute axis definition of Sketch.3 is modified and the position of the pocket is changed.

  12. From the specification tree, double-click Sketch.2 to edit it.

  13. On the sketch, double-click the the offset value as shown:

  14. In the Constraint Definition dialog box which is displayed, enter a new value, 90 for example, and click OK. The constraint is updated, and Sketch.2 is moved accordingly.

  15. Exit the Sketcher workbench. As you can see, Pocket.1 has been moved, and Pocket.2 is still positioned according to the absolute axis you defined for Sketch.3.