Adding a Stagger Origin Point

In the manufacturing process of composite part, it is important to avoid, or at least minimize, the overlapping of the tape and tow junction (chimney effect) that would locally reduce the material strength. This is done by defining precisely an origin point for tooling each ply through staggering.

• 
  Top view of plies without staggering:
  
• Top view of the same plies with staggering:
  
• Front view of the same plies, first without staggering, then with staggering:
  

Define Stagger Origin Points generates stagger origin points for each ply and checks validity of existing ones.

The Origin point is the starting point used to tool a ply. Stagger origin points avoid the overlapping of tapes or tows junction.

The Reference point is the point used to generate stagger origin points, generally the origin of the rosette.

The output will be:

• The origin point for each ply,
• Analysis results and reason when KO,
• Viewer in the suggested UI,
• An exported table containing the stagger indexes and warning messages.

1. Click Define Stagger Origin Points .
   The Stagger Origin dialog box is displayed:
   

2. Select the Plies group to process.
   The dialog box is populated with information gathered from this Plies group.
   

   This Plies group is divided into Homogeneous sets i.e. sets of plies that share the same rosette, the same valid orientation, the same reference point and share a common area of the reference surface with another ply of the set.
   
   They are listed by their index in the second column (Homogeneous set).
   Two plies that share the same common area are linked.
   Filters are now available, based on the Homogeneous sets, Rosette, Reference point and Orientation of the plies.
   Selecting a line in the dialog box highlights the corresponding ply in the 3D window.
   Here, filter has been applied on Homogeneous set 4 and a few plies have been selected:
   

3. Click COMPUTE. Stagger origin points are computed.
   When the computation is done, select a ply in the dialog box.
   It is highlighted in the 3D Window:
   

   For stagger index =0: Starting from a reference point, a geodesic line is created on reference surface using fibber orientation (e.g. -45 degrees) given by rosette transfer. Geodesic curves parallel to previous reference curve are created on surface with a geodesic distance equals to Material Width plus Gap. Those parallels are extrapolated up to the surface limits if needed. Intersection of these parallels with Ply.14 (rectangle in fat pink) are computed. Segment for origin point (solid pink line) is defined as the centered intersection. Origin point is the middle of this segment. For the following indices, the same computation is applied, but the first parallel is offset by a distance equal to the Minimum Staggering Value.

4. In the dialog box, information is given on the computation:
   

5. Modify the Parameters and restart the computation. The status and the diagnostic list displayed at the end of the computation helps you modify these parameters.

   Stagger index, i.e. the integer value associated to a ply to define the position of its origin point with respect to the reference point: with minimum stagger indices: only minimum stagger indices are used, i.e. 0 and 1. with maximum stagger indices: more stagger indices can be used. Tip: they are listed under the Homogeneous set column. Note that two linked plies cannot have the same index. Minimum Stagger Value (MSV): distance between two stagger indices to get optimum shear strength. The default value is 20mm. Width: width of the material, i.e. tape width. The default value is 100 mm. Gap: value of the gap that exists between two adjacent tapes. Minimum nb plies: minimum number of plies that must be located between two plies with the same stagger value in the same homogeneous set of plies. The default value is 4. Tolerance: maximum distance between manual origin point and stagger origin point computed from the stagger index.

6. Select one or several plies in the dialog box. Point management become available:
   

   Place your cursor in Reference and select a point in the 3D window or the specification tree to replace the current reference point of the plies selected. The modification will apply to all the plies selected. Click reset default to revert to the default reference point, that is the origin of the ply rosette. Place your cursor in Origin and select a point in the 3D window or the specification tree to replace the current origin point of the plies selected. The modification will apply to all the plies selected. A confirmation is requested to change the parent body if the point selected does not belong to the open body MANUFACTURING of the ply. This confirmation is requested for each ply selected. Click reset as computed to revert to the computed origin point. Modify from Stagger index provides a drop-down list of the indices used for the computation of stagger origin points. Select one index to change the current one. When one ply only is selected, the drop-down list proposes only the indices that will not lead to an error, while all values are proposed when several plies have been selected. A confirmation to change the Origin is requested when you select a new index.

7. If required, click Export table... to export the result as a file.
   

8. Click OK when done to validate and exit the dialog box. The stagger origin point is created under the ply.
   

9. When stagger origin points already exist in a plies group, start the command and click Check to check their validity.
   You can then edit them as explained above.