For machined parts, the Geometric Cost Drivers pane displays a group of special GCDs, setup axes, named SetupAxis:1, SetupAxis:2, SetupAxis:3, and so forth. They appear under Setup Axes/Candidates, which appears under Component. Each setup axis listed in the Geometric Cost Drivers pane represents a direction in the coordinate system of the part, that is, a part-relative direction (such as top-wards).

Setup axes differ from other kinds of axes (such as a GCD’s axis of symmetry or a part’s turning axis) in an important respect: whereas other types of axes are lines (with a specific location) in the coordinate system of the part, setup axes indicate only directions in the coordinate system of the part. A direction can be thought of as an equivalence class of co-directional lines, or alternatively as a unit vector extending from the origin of the part’s coordinate system.

Setup axis GCDs serve two purposes:

aPriori creates setup axis GCDs to represent every potentially useful setup orientation and every direction from which a tool might usefully approach a GCD in order to machine it. (For each group of planar faces that face the same direction, it creates a setup axis normal to the planar faces in the group; for each group of curved walls whose rules run in the same direction, it creates a setup axis co-directional with the rules; and for each group of axisymmetric GCDs whose axes of symmetry run in the same direction, it creates a setup axis to specify that direction as well. Additional setup axes are created for other GCDs if necessary.)

SetupAxis GCDs are used to represent part-relative directions from which a tool might possibly approach, that is, to represent how a tool might be oriented during the performance of an operation. Each setup axis listed in the Geometric Cost Drivers pane is a candidate tool orientation.

For each of a part’s GCDs, and for each setup axis, aPriori extracts information about the accessibility of the GCD to a tool approaching from the direction represented by the setup axis. This information appears in the Geometric Cost Drivers Pane under the GCD Relation Is Accessible From.

For example, suppose that the direction represented by SetupAxis:1 is normal to PlanarFace:1, and suppose that a tool approaching from that direction has partially obstructed access to PlanarFace:1. Then the Geometric Cost Drivers pane will list an Is Accessible From relation that relates SetupAxis:1 to PlanarFace:1, and whose Direction Type is Normal Obstructed.

aPriori uses this accessibility information to help determine whether it is feasible for a given type of machine to maneuver its cutting tools into position for a given operation. See GCD Accessibility and Tool Orientations for more information.

SetupAxis GCDs are used to represent a part orientation that is established by an individual setup operation. Each setup operation in the Manufacturing Process pane is listed together with a setup axis—the name of the setup axis appears in parentheses next to the operation name.

A given SetupAxis GCD represents the orientation in which the setup axis (a part-relative direction) is co-directional with the machine’s tool approach direction (the machine-relative direction from which the tool approaches).

An exception to this is a rotational setup axis for a 4-axis mill; in this case, the SetupAxis GCD represents the orientation in which the setup axis is parallel to the machine’s axis of rotation—see Setup Axes and Operation Feasibility for more information. (Note that aPriori assumes that rotation about the machine’s axis of rotation is not fast enough to support turning operations.)

For all the operations listed under the Setup operation, the part orientation specified by the associated setup axis allows the tool to perform the operations on the associated GCDs (the GCDs listed under the operations in the Manufacturing process pane).

For turning operations, aPriori represents the part orientation as a turning axis rather than a setup axis, describing whether the part is supported by its left hand side or its right hand side with respect to the turning axis. See Turning Axes. (Note that rotation about a turning axis, unlike rotation about a 4- or 5-axis mill’s axis of rotation, is assumed to be fast enough to support turning operations.)

Feasibility rules for non-turning operations typically attempt to select a setup axis that can render the current GCD accessible to the current operation. See GCD Accessibility and Tool Orientations and GCD Accessibility and Setup Axes.