Edges/Limits

The shell plate must meet certain restrictions and conditions in order for the plate to be possible to develop. Examples are:

• The number of seams/limits must be in the range 3 to12

• In the internal development process the plate is always treated as if it has four edges (with an exceptional case when one of the shorter edges has collapsed, for example, for a triangular plate)

• If there are more than four edges some consecutive edges must be linked together to form one of the edges of the internal process.

Suppose that the plate is surrounded by its least circumscribed rectangle as shown in the figure below.

Then the limit parallel to the shorter side to the left is called edge 1, the one to the right 3, the lower longer edge 4 and the upper longer edge 2. Any of edge 1 and edge 3 (but not both!) may collapse to a point (for a ‘triangular’ plate).

Remarks:

Normally, but not necessarily, edges 1 and 3 are the shorter ones. A more general definition is that edges 1 and 3 are edges between which the baseline is generated (cf. below).

The edge numbers of the internal ‘four-edged plate’ need not be the same as the order numbers of the seams pick to define the plate.

Any required linking of given limits to the internal ones is performed automatically by the development function. The figure below shows how two given seams will be combined to form an internal edge. Even if this is done automatically you may take over control of this linking in special cases via the input form.