Apparatus and method of controlling a welding cycle

A method of maintaining a generally constant voltage in a welding wire as the extension of said wire varies during plasma boost portions of successive weld cycles during a welding procedure including a succession of short circuit conditions, plasma boost portion and plasma conditions each having a controlled welding current and said short circuit conditions having a given current curve, said method comprising the steps of:

• (a) creating a first reference signal proportional to a desired wattage value during successive plasma boost portions of said welding procedure;
• (b) measuring the voltage level across said extension for said welding wire for a short time and at a precise location on said given current curve during said successive short circuit conditions;
• (c) averaging said measured voltage levels;
• (d) multiplying said average of said voltage levels with said instantaneous welding current to provide a second signal representative of the wattage during said successive plasma boost portions of said welding procedure;
• and
• (e) adjusting said welding current during said successive plasma boost portions to cause said second signal to approach said first reference signal.

A system for maintaining a generally constant wattage in a welding wire as the extension of said wire varies during plasma portions of successive cycles during a welding procedure including a succession of short circuit conditions and plasma conditions having a controlled welding current, said short circuit conditions having a given current curve, said system comprising:

• (a) means for creating a first reference signal proportional to a desired wattage value during successive plasma portions of said welding procedure;
• (b) means for measuring the voltage level across said extension of said welding wire for a short time and at a precise location on said given current curve during said successive short circuit conditions;
• (c) means for averaging said measured voltage levels;
• (d) means for multiplying said average of said voltage levels with said instantaneous welding current to provide a second signal representative of the wattage during said successive plasma portions of said welding procedure;
• and,
• (e) means for adjusting said welding current during said successive plasma portions to cause said second signal to approach said first reference signal.

In a short circuiting arc welding apparatus comprising a D.C. power supply means for causing a welding current of different levels to pass through a welding wire extending from a holder and between said wire and a workpiece at a molten metal pool on said workpiece, wire feeding means for feeding said wire from said holder toward said workpiece whereby said welding wire is subjected to a succession of welding cycles, each of said welding cycles including an arcing condition during which said wire is spaced from said pool and the energy applied to said wire exceeds a given value raising the temperature at the end of said wire to a molten temperature to form a molten metal ball on the end of said wire and a short circuit condition during which said molten metal ball on the end of said wire first contacts said molten metal pool and then transfers from said wire to said workpiece by a necking action breaking said molten metal ball from said wire to initiate an arc in a subsequent welding cycle, the improvement comprising:

• means for creating a current pulse upon initiation of said arcing condition, said current pulse having a first occurring plasma boost portion with a current increasing to a first general current level and a second occurring plasma portion with a second general current level, said first general current level being at a controlled high current level and said second general current level having a curve gradually decreasing from said controlled high current level.

In a short circuiting arc welding apparatus comprising a D.C. power supply means for causing a welding current of different levels to pass through a welding wire extending variable distances from a holder and between said wire and a workpiece at a molten metal pool on said workpiece, said current flowing in response to an arc voltage whereby said welding wire is subjected to a succession of welding cycles, each of said welding cycles including an arcing condition during which said wire is spaced from said pool and the energy applied to said wire exceeds a given value raising the temperature at the end of said wire to a molten temperature to form a molten metal ball on the end of said wire and a short circuit condition which said molten metal ball on the end of said wire first contacts said molten metal pool and then transfers from said wire to said workpiece by a necking action breaking said molten metal ball from said wire to initiate a arc in a subsequent welding cycle, means for controlling the shape of the current pulse when said wire first contacts said metal pool, said shape being a first rapidly increasing current portion and a subsequent, second gradually increasing current portion with said portions intersecting at a break point, the improvement comprising:

• control means for reducing the current level of said break point, said control means responsive to detection for a short circuit during said arcing condition.

In a short circuiting arc welding apparatus comprising a D.C. power supply means for causing a welding current of different levels to pass through a welding wire extending variable distances from a holder and between said wire and a workpiece at a molten metal pool on said workpiece, said current flowing in response to an arc voltage whereby said welding wire is subjected to a succession of welding cycles, each of said welding cycles including an arcing condition during which said wire is spaced from said pool and the power applied to said wire raises the temperature at the end of said wire to a molten temperature to form a molten metal ball on the end of said wire, and a short circuit condition during which said molten metal ball on the end of said wire first contacts said molten metal pool and then transfers from said wire to said workpiece by a necking action breaking said molten metal ball from said wire to initiate an arc in a subsequent welding cycle, the improvement comprising:

• means for creating a plasma boost current pulse at the start of the arcing condition of successive ones of said welding cycles, means for maintaining said applied power by controlling the welding current during said plasma boost current pulses to provide a predetermined wattage in said wire during each said plasma boost current pulses and means for terminating said power boost pulse after a selected time.

In an arc welding apparatus comprising a D.C. power supply means for causing a welding current of different levels to pass through a welding wire extending variable extension distances from a holder and between said wire and a workpiece at a molten metal pool on said workpiece, wire feeding means for feeding said wire from said holder toward said workpiece whereby said welding wire is subjected to a succession of welding cycles, each of said welding cycles including an arcing condition during which said wire is spaced from said pool and the energy applied to said wire exceeds a given value raising the temperature at the end of said wire to a molten temperature to form a molten metal ball on the end of said wire and a short circuit condition during which said molten metal ball on the end of said wire first contacts said molten metal pool and then transfers from said wire to said workpiece, the improvement comprising:

• means for creating a current pulse upon initiation of said arcing condition, said current pulse having a first occurring plasma boost portion with a current at a first general current level, means for applying a low level background current between said wire and said workpiece after termination of said current pulse and until the next short circuit condition of said welding cycle and control means for maintaining a generally constant wattage in said wire during said plasma boost portion as said extension distances change whereby said extension can be adjusted to change the welding current flow in the workpiece.

In a short circuiting arc welding apparatus comprising a D.C. power supply means for causing a welding current of different levels to pass through a welding wire extending from a holder and between said wire and a workpiece at a molten metal pool on said workpiece, wire feeding means for feeding said wire from said holder toward said workpiece whereby said welding wire is subjected to a succession of welding cycles, each of said welding cycles including an arcing condition during which said wire is spaced from said pool and the energy applied to said wire exceeds a given value raising the temperature at the end of said wire to a molten temperature to form a molten metal ball on the end of said wire and a short circuit condition during which said molten metal ball on the end of said wire first contacts said molten metal pool and then transfers from said wire to said workpiece by a necking action breaking said molten metal ball from said wire to initiate an arc in a subsequent welding cycle, the improvement comprising:

• means for creating a current pulse upon initiation of said arcing condition, said current pulse having a first occurring plasma boost portion with a current increasing to a first general current level and a second occurring plasma portion with a second general current level, said first general current level being at a controlled high current level and said second general current level decreasing gradually from said controlled high current level.