GCD Extraction
aPriori extracts the geometry of a CAD model in the form of geometric cost drivers (GCDs) that include surfaces and holes, as well as bending and forming GCDs, lances, and a GCD that represents the flattened blank from which the sheet metal part if formed. As usual, there is a special GCD, Component, that represents the part as a whole. Below are some of the important properties of each of these GCD types. Each GCD’s units are shown in metric.
• Component:
o Volume (mm3)
o Surface Area (mm2)
o Length, Width, and Height (millimeters)
o Number of Surfaces
o Min Thickness, Max Thickness, and Avg Thickness (millimeters)
o Length Direction, Width Direction, and Height Direction: each of these is a unit vector, two of whose components are 0 (the other component is 1 or -1). These vectors can be compared with the Direction vector of another GCD (such as a Setup Axis) in order to determine whether the GCD’s direction is aligned with the part’s length, width, or height.
• Blank:
o Perimeter (millimeters)
o SER Length and SER Width (smallest enclosing rectangle dimensions in millimeters)
o Thickness (millimeters)
o Straight Length (millimeters)
• Surfaces (Curved Surface, Curved Wall, and Planar Face):
o Finished Area (mm2)
o Bend Diameter (millimeters)
o Perimeter (millimeters)
o SER Length and SER Width (smallest enclosing rectangle dimensions in millimeters)
o Corner Diameter (millimeters)
o Inside Diameter (millimeters)
o Number of Surfaces
o Fillet Min Angle and Fillet Max Angle (degrees)
o Round Radius (millimeters)
o Round Length (millimeters)
o Wall Corner Diameter (millimeters)
• 
Holes (Simple Hole, Complex Hole):
Holes (Simple Hole, Complex Hole): o Diameter (millimeters),
o Length and Depth (millimeters)
o Volume (mm3)
o Surface Area (mm2)
o Hole type (THROUGH or BLIND)
o Blind, Sleeve Pin, Threaded, Countersunk, and Flanged (TRUE or FALSE)
• Bending/Forming (Bend, Multi Bend, Form, Shear-Form):
o Bend Angle (degrees)
o Length (millimeters)
o Bend Flap Size (millimeters)
o Min Bend Radius (millimeters)
o SER Length (millimeters)
o SER Width (millimeters)
o Perimeter (millimeters)
o 
• Lance:
o Length (millimeters)
• Edge:
o Edge Type (Sharp or Chamfer)
o Is Accessible
o Is Staright
o Length
o Height
o Angle
o Round Radius
o Min Concave Radius
o Min Convex Radius
o Min Wall Angle
o Max Wall Angle
o Internal
You can modify Form GCDs by adding or removing surfaces, and you can define a new Form GCD by the specifying the included surfaces—see Creating and Editing Forms.
In addition to solid CAD models, the Sheet Metal process group supports surface CAD models, which represent surfaces only, rather than solid geometry. See Surface-only CAD Models for Sheet Metal.