Ram Direction for Transfer Die
The RamDirection GCD represents the direction from which the ram approaches the workpiece. aPriori chooses a part-relative ram direction as described in How the Default Ram Direction is Chosen. This choice attempts to minimize undercuts and provide access to the part’s primary form. You can override aPriori’s choice as described in Overriding the Default Ram Direction.
Overriding the Default Ram Direction
You can override aPriori’s choice of ram direction by using the Ram Direction tool, , in the Viewer. Follow these steps:
4 Select the Ram Direction tool from the Viewer toolbar.
5 An orange arrow indicates the ram direction. The arrow points to the region of space from which the ram approaches; the direction in which the ram moves as it approaches the part is the opposite of the ram direction.
When you hover over a flat or cylindrical surface, the Viewer highlights the surface, and a yellow arrow indicates the candidate ram direction associated with that surface.
Click a highlighted surface to set the new ram direction.
You can also use the Advanced mode of the Ram Direction tool in order to set the ram direction by specifying Azimuth and Zenith.
How the Default Ram Direction is Chosen
In order to choose a ram direction, aPriori identifies a number of candidate directions:
• Direction of each (simple or complex) hole.
• Direction associated with the part’s largest, accessible surface
The direction associated with the part’s largest accessible surface is a direction that provides the best accessibility to the maximal group of adjacent surfaces that has the following characteristics:
• Group includes the part’s largest, accessible surface.
• Every surface in the group is accessible from the same direction.
The direction that provides best accessibility to such a group is the direction that maximizes the projected area of the surfaces onto a plane perpendicular to the direction.
(Note that a group of adjacent surfaces is a group such that for any pair of surfaces in the group, there is a path from one surface to other that never leaves the group.)
In order to pick the ram direction from among the candidate directions, aPriori also associates such a maximal group of surfaces with each hole. That is, for each hole, it finds the maximal group of adjacent surfaces that has the following characteristics:
• Group includes the surface that contains the hole
• Every surface in the group is accessible from the same direction.
To select the ram direction, aPriori weighs the following factors for each candidate direction:
• Area of the projection of the candidate’s associated surfaces onto a plane perpendicular to the candidate. Larger areas are favored.
• Area of the holes that are parallel to the candidate. Larger areas are favored.
• Projected area of all the part’s planar surfaces that are perpendicular to the candidate. Larger areas are favored.
• Area of the surfaces that are not in the candidate’s associated group. Smaller areas are favored.
The selected direction actually represents a pair of opposite directions (such as East/West or Up/Down). aPriori selects one element of the pair of opposites based on the following factors:
• Cross-sectional area (parallel to the ram direction) of the part’s SER below and above the part. If one area exceeds about twice the other area, the ram direction points towards the smaller volume
• Side-accessible projected area of the flange surfaces that wrap around the part. This is the area of the projection of the outside flanges onto planes that contain the ram direction. If the projected area of one side of the flange surfaces exceeds the projected area of the other side of the flange surfaces by about 10% or more, the side with larger projected area faces the ram direction.