Save your face

Why do we insist on faces? In robotics we need to provide the location of the robot tool (paint nozzle, welding torch, glue gun etc.) in terms of translation (XYZ) and rotation (angles around X, Y and Z), within the robot coordinate system.
A line (or an edge) has only a direction vector, because a body can rotate freely around it, so its angular orientation is not defined. A face, however, (of any feature, not even flat) has defined vectors at any point.
By analyzing the geometry of the part, RobotWorks is able to create a complete path based on the faces. Therefore, the accuracy of the path no longer depends on the dexterity of the robotics expert or his ability to eyeball a position.
Following the geometry is several times more accurate then any manual method. The difference between the two methods is like that between a driver trying to keep his car on the road, and an engineer trying to keep his train on the tracks.
It is true that not all the robots are engaged in moving along faces. Handling, palletizing and spot welding robots usually spend most of their time in mid air, in point-to-point motion. However, continuous path robots, which weld, cut, paint, seal, polish, sew, slit, trim, and deburr, always follow a part contour or a prescribed path on a part, usually along a face or an edge. They are the hardest to program; therefore they will benefit the most from following geometry.