Joining Surfaces or Curves

This task shows how to join at least two surfaces or two curves.

The surfaces or curves to be joined must be adjacent.
Open the Join1.CATPart document.

  1. Click the Join icon.

The Join Definition dialog box appears.

  1. Select the surfaces or curves to be joined.

  2. You can edit the list of elements to be joined:
by selecting elements in the geometry:
Standard selection (no button clicked):
when you click an unlisted element, it is added to the list 
when you click a listed element, it is removed from the list
Add Mode: 
when you click an unlisted element, 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, the list is unchanged 
when you click a listed element, it removed from the list
by selecting an element in the list then using the Remove\Replace contextual menu items.
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.

  1. Right-click the elements from the list and choose the Check Solution command.

This let's you check whether any element to be joined presents any intersection (i.e. at least one common point) with other elements prior to creating the joined surface:

The Checker dialog box is displayed, containing the list of domains (i.e. sets of connected cells) belonging to the selected elements from the Elements To Join list.

  1. Click Apply.
An Information message is issued when no intersection is found.
When an element is self-intersecting, or when several elements intersect, a text is displayed on the geometry, where the intersection is detected.

  1. Click Cancel to return to the Join Definition dialog box.

  1. Right-click the elements from the list and choose the Propagate command. It allows the selection of elements of same dimension to be added to the Elements To Join list.
The initial element to propagate cannot be a sub-element
Forks stop the propagation
Intersections are not detected

  1. Click Apply in the Join Definition dialog box.

The joined element is previewed, and its orientation displayed. Click the arrow to invert it if needed.
The join is oriented according to the first element in the list. If you change this element, the join's orientation is automatically set to match the orientation of the new topmost element in the list.

  1. Check the Check tangency button to find out whether the elements to be joined are tangent. If they are not, and the button is checked, an error message is issued.

  1. Check the Check connexity button to find out whether the elements to be joined are connex. If they are not, and the button is checked, an error message is issued indicating the number of connex domains in the resulting join.
    When clicking Apply, the free boundaries are highlighted, and help you detect where the joined element is not connex.

  1. Check the Check manifold button to find out whether the resulting join is manifold.
The Check manifold button is only available with curves.
Checking it automatically checks the Check connexity button.

The Simplify the result check button allows the system to automatically reduce the number of elements (faces or edges) in the resulting join whenever possible.

The Ignore erroneous elements check button lets the system ignore elements that would not allow the join to be created.

  1. You can also set the tolerance at which two elements are considered as being only one using the Merging distance.

  1. Check the Angle Tolerance button to specify the angle value below which the elements are to be joined.
    If the angle value on the edge between two elements is greater than the Angle Tolerance value, the elements are not joined. This is particularly useful to avoid joining overlapping elements.
If the edges or the faces have a angular threshold higher than the predefined value, a text is displayed on the geometry indicating the error type.
You can either deactivate the check box or increase the value of the angular threshold, or remove all the elements or sub-elements that are in error.

  1. Click the Sub-Elements To Remove tab to display the list of sub-elements in the join.

These sub-elements are elements making up the elements selected to create the join, such as separate faces of a surface for example, that are to be removed from the join currently being created.

You can edit the sub-elements list as described above for the list of elements to be joined.

  1. Check the Create join with sub-elements option to create a second join, made of all the sub-elements displayed in the list, i.e. those that are not to be joined in the first join.
    This option is active only when creating the first join, not when editing it.

  1. Click OK to create the joined surface or curve.

The surface or curve (identified as Join.xxx) is added to the specification tree.

Sometimes elements are so close that it is not easy to see if they present a gap or not, even though they are joined. Check the Surfaces' boundaries option from the Tools -> Options menu item, General, Display, Visualization tab.
Once the Join.xxx element has been created, you can use the Check contextual menu from the specification tree. In this case however it verifies the connexity of all the sub-elements making up the joined surface. This is particularly useful when many elements have been joined, so has to highlight in the geometry which sub-element is not connected to the other ones, thus allowing you to rework the geometry if needed.

 
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