Main Surface for Transfer Die
The MainSurface GCD represents a portion of the part that retains a relatively stable orientation relative to the press table all throughout the stamping process, except during active tipping (which the model does not currently support). For transfer die, a pad that spans the main surface holds the part in place during operations such as drawing and pad & wipe. aPriori chooses a main surface as described below. The choice attempts to minimize expensive tooling and minimize the number of stations required to make the part.
The MainSurface GCD consists of the group of associated surfaces that has the following characteristics:
• No surface in the group is part of any bend.
• No surface in the group is nearly vertical; that is, the normal to each surface in the group is within 60 degrees of the ram direction (see Ram Direction for Transfer Die).
• Every surface in the group is accessible from the ram direction.
aPriori identifies multiple main-surface candidates that have the above characteristics, and then selects one of the candidates by weighing the following considerations:
• Height of the surfaces, measured from the bottom of the part bounding box. Higher candidates are favored.
• Area of the surfaces; or, more precisely, the area of the projection of the surfaces—including holes—onto a plane normal to the ram direction. Larger candidates are favored.
• Distance of the surfaces from the centroid of the part. Closer candidates are favored.
Note that surfaces within a given group may by separated into disjoint islands by deformations in the part.
The XY orientation of the surface is determined within the cost model. You can override aPriori’s choice of ram direction (which affects main surface choice) by using the Ram Direction tool in the Viewer. See Ram Direction for Transfer Die.
The images below show the main surface in yellow.
