Machine for self-adjusting its operation to compensate for part-to-part variations

A workstation comprising:

• a fixture for holding a workpiece at a fixed location on the fixture;
• a processing unit comprising a vision system and a tool for performing an operation on a workpiece held on the fixture;
• a robot for moving one of the fixture and the processing unit relative to the other of the fixture and the processing unit within a three-dimensional orthogonal coordinate system by translation along X, Y, and Z axes which intersect at an origin of the coordinate system and by turning angularly about each of the X, Y, and Z axes;
• the vision system comprising a three-dimensional scanning camera for scanning workpieces and a processor for developing from scans of workpieces, coordinate data about workpieces within a coordinate system of the vision system,
• a controller which is operable to cause the robot to move the one of the fixture and processing unit relative to the other of the fixture and processing unit to place the scanning camera in a scan start position and then cause the scanning camera to move along a scan path while the scanning camera scans a region of a first workpiece which is held on the fixture and is expected to contain a feature on which the tool could perform an operation, the feature comprising a surface having a two-dimensional area defined by X-axis and Y-axis coordinate data, and at locations within the two-dimensional area, the surface being further defined by Z-axis coordinate data;
• the processor being operable to develop from a scan of the region of the first workpiece, master coordinate data for the feature in the coordinate system of the vision system;
• the controller being further operable to cause the tool to be positioned at a master home position in the robot's coordinate system from which the tool would begin to move along a prescribed operating path if it were to perform a prescribed operation on the feature and to record coordinate data for the master home position in the robot's coordinate system;
• the controller being further operable to cause the scanning camera to move from the scan start position along the scan path while the scanning camera scans a region of a second workpiece which replaces the first workpiece on the fixture and is expected to contain a feature substantially identical to the feature of the first workpiece;
• the processor being operable to develop from a scan of the region of the second workpiece, coordinate data for the feature of the second workpiece in the coordinate system of the vision system, to calculate differences between the coordinate data for the feature from the scan of the region of the second workpiece and recorded coordinate data for the master home position, and to transmit those differences to the controller;
• and
• the controller being operable to create a modified home position for the tool in the robot's coordinate system by modifying the recorded coordinate data for the master home position by those differences and to cause the tool to begin to move from the modified home position along the prescribed operating path when performing the prescribed operation on the feature of the second workpiece.