Creating Variable Offset Surfaces

• Removing sub-elements
• Creating constant offset surfaces

1. Click Variable Offset .

   The Variable Offset Definition dialog box appears.

2. Select the Base Surface to be offset (here Join.1).

3. Select each sub-part to be offset (whether wires or surfaces) and define its offset type from the Offset drop-down list:

   Variable: Applies a variable offset to the sub-part. The offset value field is grayed out. Constant: Applies a constant offset to the sub-part. Specify the offset value.
   	If the sub-part to offset is an element such as a line, curve, or edge, you can select the offset to be: Constant (Border): The element is considered as a border element. Hence, it must lie on a boundary. Constant (Inner): The element is considered as a constant constraint within a variable area. Hence it must lie in a variable area and not on a boundary.

   Both offset types apply to wires and surfaces.

   In our example, we defined a constant offset value of 40mm for Surface.1, a variable offset value for Surface.2 and a constant offset value of 20mm for Surface.3.

   You can use the following: Add Before radio button: to add a surface before the selected surface, Add After radio button: to add a surface after the selected surface, Replace radio button: to replace the selected surface by another surface, Remove button: to remove the selected surface.

4. Select the Offset law type between Linear and S type.

   By default, S type is the offset law type. The extremities are tangent continuous.

5. Click Preview.

   The offset surface is displayed normal to the reference surface.

   You can click Reverse Direction to reverse the offset direction.

6. Specify the following advanced parameters:

   Automatic split of variable areas	Select this check box to perform automatic internal split of variable areas if necessary. This check box is unavailable when the Linear offset law type is selected.
   Merging Distance	Select this check box and enter the merging distance value.
   Angular Threshold	Select this check box and enter the angular threshold value.
   Deviation	Select this check box and enter a deviation value. The entered deviation is applied to all the selected parameters. It is a maximum deviation allowed between actual result and exact result.

7. Click OK.

   One single feature is created: an automatic join of the resulting areas is performed if the result quality allows it (G1 connections).

   The surface (identified as Variable Offset.xxx) is added to the specification tree.

Removing Sub-Elements

The Sub-Elements to remove tab helps you for the analysis in case the offset encounters a problem.

Open the VariableOffset2.CATPart document.

1. Click Variable Offset .

   The Variable Offset Definition dialog box appears.

2. Select the Base Surface to be offset (here Global Surface).

3. Select each sub-element to be offset (whether wires or surfaces) and define its offset type:

4. Click Preview.

   The Warning dialog box appears, the geometry shows the erroneous sub-elements, and flag notes display sub-elements to remove.

5. Click Yes to accept the offset.

   In the Variable Offset Surface Definition dialog box, the Sub-Elements to remove tab lists the erroneous sub-elements and a preview of the offset is displayed.
   If you move the mouse over a flag note, a longer message giving an accurate diagnosis is displayed. You can remove a sub-element by right-clicking it and choosing Clear Selection from the contextual menu.
   The following modes are optional, you may use them if you need to add or remove a sub-element to create the variable offset. Add Mode:  when you click an unlisted element in the geometry, it is added to the list  when you click a listed element, it remains in the list Remove Mode:  when you click an unlisted element in the geometry, the list is unchanged  when you click a listed element, it is removed from the list
   	If you double-click the Add Mode or Remove Mode button, the chosen mode is permanent, i.e. successively selecting elements will add/remove them. However, if you click only once, only the next selected element is added or removed. You only have to click the button again, or click another one, to deactivate the mode.
   	The list of sub-elements to remove is updated each time an element is added. Note that if you modify an input in the Offset dialog box, the list is re-initialized.
   	The availability of context commands depend on the location where you activate the contextual menu, and the context commands act only on the lines that you right-click. If more than one lines are highlighted, right-clicking one highlighted line is equivalent to right-clicking all the highlighted lines at the same time. In this case, the context command acts on all the highlighted lines. Consider the following cases: Case 1: line 1 is highlighted and line 1 is right-clicked: the selected contextual command will act on line. Case 2: line 1 is highlighted and line 2 is right-clicked (but not highlighted): the selected contextual command will act on line 2. Case 3: line 1 and line 2 are highlighted and line 1 is right-clicked: the selected contextual command will act on both line 1 and line 2. Case 4: line 1 and line 2 are highlighted and line 3 is right-clicked (but not highlighted): the selected contextual command will act on line 3.

6. Click Preview.

   The offset surface is displayed normal to the reference surface.

7. Click OK to create the surface.

   The surface (identified as Variable Offset.xxx) is added to the specification tree.

Creating constant offset surfaces

1. Click Variable Offset .

   The Variable Offset Definition dialog box appears.

2. Select the Base Surface as the Base Surface.

3. Select each sub-element to be offset and apply a different constant offset value to each of them as shown in the picture below:

4. Click OK to create the surface.

   	All adjacent surfaces that are tangent continuous must have the same offset value. Otherwise an error message is issued. There should not be any fading edges between two surfaces that have different offset values.