Adaptive control system for welding inverted seams

In an apparatus for arc welding a workpiece, the apparatus including arc moving means for oscillating an electrode laterally across the workpiece about a predetermined center reference point, an improvement for welding an edge joint on the workpiece, comprising:

• noncontacting means for sensing the lateral profile of edge joint while the electrode is moving laterally across the edge joint and for obtaining data representative of the edge joint profile;
• means for comparing at least a portion of said representative edge joint data to reference data and for providing an error signal as a function of the difference between said representative edge joint data and said reference data;
• control means responsive to said error signal for adjusting a first welding parameter related to the position of the electrode with respect to the edge joint;
• means responsive to said representative edge joint data for providing an edge proximity signal upon the detection of the approach of a lateral edge of the edge joint;
• and
• adjusting means responsive to said edge proximity signal for adjusting a second welding parameter related to the fill height of the weld during the lateral movement of the electrode toward said lateral edge.

In an apparatus for arc welding a workpiece, the apparatus including arc moving means for oscillating an electrode laterally across the surface of a workpiece about a center reference point and for moving the electrode longitudinally along the workpiece, the electrode moving along a path on the surface of the workpiece defined by projecting a line from the end of the electrode to intersect perpendicularly with a point on the surface, an improvement for welding an edge joint on the workpiece, comprising:

• means for measuring a parameter of the welding arc and for providing an arc signal having a magnitude related to the vertical distance between the electrode and the surface of the edge joint by periodically holding the electrode vertically stationary as the electrode is moved laterally across the edge joint;
• memory means for storing a plurality of samples of said arc signal corresponding to a predetermined portion of the path;
• edge detecting means responsive to said stored arc signal samples for detecting a lateral edge of the edge joint;
• means for detecting when the electrode has been moved along the path to a predetermined lateral distance from a lateral edge of the workpiece detected by said detecting means and for providing an edge proximity signal;
• means responsive to said edge proximity signal for adjusting a welding parameter related to the fill height of the weld while the electrode is within said predetermined distance and approaches said detected lateral edge;
• and
• signal processing means responsive to said stored arc signal samples for changing the lateral direction of movement of electrode along the path when the electrode approaches to within a second predetermined lateral distance from said detected lateral edge.

A method for welding an edge joint on a workpiece such as a turbine blade or the like, comprising the steps of:

• moving an arc electrode along a path on the surface of the edge joint, said path defined by projecting a line from the end of the electrode to intersect perpendicularly with a point on the surface;
• periodically holding the electrode vertically stationary while the electrode is moved laterally across the edge joint;
• while the electrode is held vertically stationary, measuring a parameter of the arc and providing an arc signal having a magnitude related to the vertical distance between the electrode and the surface of the edge joint as the electrode is moved along the path;
• repeatedly storing in a memory plurality of samples of the arc signal corresponding to a predetermined portion of the path of the electrode;
• detecting an edge of the edge joint by comparing the stored arc signal samples to a reference value;
• detecting when the electrode has been moved along the path to a predetermined distance from the detected edge of the edge joint;
• reducing the welding current provided to the electrode while the electrode is within said predetermined distance and approaches the detected edge to prevent melting of the edge;
• processing the stored samples of the arc signal so as to determine when the electrode has approached to within a second predetermined distance from the detected edge;
• and
• changing the direction of movement of the electrode along the path when the electrode has approached to within said second predetermined distance.

In an apparatus for arc welding a workpiece, the apparatus including arc moving means for oscillating an electrode laterally across the surface of a workpiece about a center reference point and for moving the electrode longitudinally along the workpiece, the electrode moving along a path on the surface of the workpiece defined by projecting a line from the end of the electrode to intersect perpendicularly with a point on the surface, an improvement for welding an edge joint on the workpiece, comprising:

• means for measuring a parameter of the welding arc and for providing an arc signal having a magnitude related to the vertical distance between the electrode and the surface of the edge joint by periodically holding the electrode vertically stationary as the electrode is moved laterally across the edge joint;
• memory means for storing a plurality of samples of said arc signal corresponding to a predetermined portion of the path;
• edge detecting means responsive to said stored arc signal samples for detecting a lateral edge of the edge joint and for providing an edge proximity signal;
• means responsive to said edge proximity signal for adjusting a welding parameter related to the fill height of the weld while the electrode is within a predetermined distance from a detected lateral edge;
• and
• signal processing means responsive to said stored arc signal samples for changing the lateral direction of movement of the electrode.

In an apparatus for arc welding a workpiece, the apparatus including arc moving means for oscillating an electrode laterally across the surface of a workpiece about a center reference point and for moving the electrode longitudinally along the workpiece, the electrode moving along a path on the surface of the workpiece defined by projecting a line from the end of the electrode to intersect perpendicularly with a point on the surface, the improvement comprising:

• means for measuring a parameter of the welding arc and for providing an arc signal having a magnitude related to the vertical distance between the electrode and the surface of the workpiece;
• memory means for storing a plurality of samples of said arc signal corresponding to a predetermined portion of the path;
• means for sensing the lateral profile of the workpiece and for providing a sensed lateral profile signal comprising a plurality of samples of said arc signal;
• means for detecting when the electrode has been moved along the path to a first predetermined distance from a previously-detected edge of the workpiece and for providing an edge proximity signal;
• means for responsive to said edge proximity signal for adjusting a welding parameter while the electrode exceeds said first predetermined distance and approaches the edge of the workpiece;
• and
• signal processing means responsive to said arc signal for adjusting the location of said center reference point and for changing the direction of movement of the electrode along the path when the electrode approaches to within a second predetermined distance from the edge of the workpiece,
• said signal processing means further responsive for adjusting the location of said center reference point in relation to an error signal, said error signal being related to a mathematical criterion of the degree of match between said lateral profile signal and a template signal, said template signal corresponding to a predetermined idealized lateral profile of the workpiece, and
• said signal processing means further responsive for comparing said lateral profile signal to each one of a plurality of discrete template signals, each of said template signals corresponding to the lateral profile signal expected for a particular center of oscillation of the electrode and a particular width of oscillation about said particular center.