A method of calibrating a position of an article relative to an end effector of a robot, comprising: providing a robotic component having the end effector with a vertical axis and end effector fingers (104A, 104B) for grasping a teach tool and having a light beam sensor provided in a fixed orientation to the end effector fingers(104A, 104B); providing the teach tool at an approximately known location on the article within a work envelope reachable by the end effector, the teach tool having a geometrical calibration feature; positioning the end effector with the light beam sensor at a first location proximate to the geometrical calibration feature, the geometrical calibration feature adapted for use to determine a positional calibration; positioning the end effector and sensing with the light beam sensor a first engagement edge of the geometrical calibration feature of the teach tool; positioning the end effector and sensing with the light beam sensor a second engagement edge of the geometrical calibration feature of the teach tool; and using the sensing of the first engagement edge and the second engagement edge to calibrate a position of the article relative to the end effector of the robot; the method being characterized by moving the end effector with the light beam sensor to a second location proximate to the geometrical calibration feature of the teach tool, the second location being different than the first location, wherein the geometrical calibration feature comprises a cylinder oriented with a longitudinal axis being vertical and located at an approximately known location on the article, the end effector rotates about the vertical axis, sc that the fingers (104A, 104B) are precisely oriented relative to a sample container in a sample rack; rotating the end effector and sensing with the light beam sensor a third engagement edge of the geometrical calibration feature of the teach tool; rotating the end effector and sensing with the light beam sensor a fourth engagement edge of the geometrical calibration feature of the teach tool; and calculating a location of the geometrical calibration feature of the teach tool. providing a robotic component having the end effector with a vertical axis and end effector fingers (104A, 104B) for grasping a teach tool and having a light beam sensor provided in a fixed orientation to the end effector fingers(104A, 104B); providing the teach tool at an approximately known location on the article within a work envelope reachable by the end effector, the teach tool having a geometrical calibration feature; positioning the end effector with the light beam sensor at a first location proximate to the geometrical calibration feature, the geometrical calibration feature adapted for use to determine a positional calibration; positioning the end effector and sensing with the light beam sensor a first engagement edge of the geometrical calibration feature of the teach tool; positioning the end effector and sensing with the light beam sensor a second engagement edge of the geometrical calibration feature of the teach tool; and using the sensing of the first engagement edge and the second engagement edge to calibrate a position of the article relative to the end effector of the robot; the method being characterized by moving the end effector with the light beam sensor to a second location proximate to the geometrical calibration feature of the teach tool, the second location being different than the first location, wherein the geometrical calibration feature comprises a cylinder oriented with a longitudinal axis being vertical and located at an approximately known location on the article, the end effector rotates about the vertical axis, sc that the fingers (104A, 104B) are precisely oriented relative to a sample container in a sample rack; rotating the end effector and sensing with the light beam sensor a third engagement edge of the geometrical calibration feature of the teach tool; rotating the end effector and sensing with the light beam sensor a fourth engagement edge of the geometrical calibration feature of the teach tool; and calculating a location of the geometrical calibration feature of the teach tool.