 Through ARC Seam Tracking, also known as TAST, is a robotic welding application that automatically adjusts the robot's vertical and lateral trajectory. TAST is an optional software-driven tool used to aid with weld joint variation difficulties. It measures feedback in real-time and adjusts the robot's path. Because some weld joints can be very problematic, TAST is a problem-solving option to help you maintain consistency. As a robot programmer, you need to understand the options available when encountering part-location issues. TAST relies on the weaving motion across the joint to collect the real-time data. It uses current changes in the contact tip to work distance to decide when to reverse the weaving motion. In a weaving motion, the TAST software notices the current decreases when the contact tip to work distance increases, such as in the center of the joint. TAST then observes that the current increases when the contact tip to work distance decreases as it approaches the weld joint edge. TAST measures feedback current and adjusts the robot's path accordingly. There is low current in the center of the weld and high current at the edge of the weld. When TAST registers a current peak at the end of the weave, it changes direction. The cycle repeats as the robot welds back and forth, constantly adjusting to the feedback current. The advantage of TAST is its ability to follow the joint regardless of joint variation or placement. TAST adapts to these variations in the lateral across joint movements and in the vertical position, meaning that the robot can maintain a constant stick out if the vertical placement varies. TAST does have some requirements and disadvantages. It must use a weave motion. It must start in the joint, which is often done by touch sensing. It can't be used with aluminum because it's too conductive and doesn't create enough current change to track. And as a final note, TAST must have enough of a recognizable joint in material thickness to create the current change. This requires a material thickness of at least .078 inches. You've completed through arc seam tracking.