Method and device for controlling a short circuiting type welding system

A method for reducing spatter when a welding power supply is employed for depositing metal from a welding wire onto a workpiece by a short circuiting transfer mode wherein a welding current causes the welding wire to alternate between a short circuit condition and an arc condition, with metal transfer requiring a transfer time T.sub.P during which transfer time the welding current rises to a maximum value and then falls, said method comprising the following steps:

• (a) detecting said short circuit condition;
• (b) shifting said welding current to a background current value in response to said detecting step;
• (c) holding said welding current generally at said background current value for a preselected time;
• (d) then allowing said welding current to reach the normal unimpeded current level;
• (e) sensing the slope of the welding current or welding voltage during the transfer time T.sub.P ;
• (f) shifting said welding current to said background current generally when said welding current reaches a level at or just beyond said maximum value as determined by said sensing step;
• (g) again holding said welding current generally at said background current value for a preselected time;
• and
• (h) again causing said second holding step to be terminated by allowing said welding current to reach the normal unimpeded current level.

A device for reducing spatter when a welding power supply is employed for depositing metal from a welding wire onto a workpiece by the short circuiting transfer mode wherein a welding current causes the welding wire to alternate between a short circuit condition and an arc condition wherein the welding current is at a plasma sustaining level, and with metal transfer requiring a transfer time during which the welding current rises and then falls, said device comprising:

• (a) first shifting means for shifting said welding current from said plasma level to a low level background value when a short condition is to occur;
• (b) means for holding said welding current at said background value for a preselected time;
• (c) means for then allowing said welding current to rise from said background value during said short circuit condition for transferring metal to said workpiece;
• (d) means for sensing when said transferring metal starts necking down preparatory to a fuse break;
• (e) means for again shifting said welding current to said background value;
• and,
• (f) second shifting means for shifting said welding current back to said plasma level awaiting the next successive short condition.

A method of reducing spatter when a welding power supply is employed for depositing metal from a welding wire onto a workpiece by the short circuiting transfer mode wherein a welding current causes the welding wire to alternate between a short circuit condition and an arc condition with the welding current being at a plasma sustaining level, and with metal transfer requiring a transfer time during which the welding current rises and then falls, said method comprising the following step:

• (a) shifting said welding current from said plasma level to a low level background value as a short condition begins;
• (b) holding said welding current at said background value for a preselected time;
• (c) then allowing said welding current to rise from said background value during said short circuit condition for transferring metal to said workpiece;
• (d) sensing when said transferring metal starts necking down preparatory to a fuse break;
• (e) shifting said welding current to said low level background value in response to said sensing step;
• and,
• (f) shifting said welding current back to said plasma level awaiting the next successive short condition.