Q&A: What is lift in stud welding?
Lift is a term that is thrown around by many in relation to stud welding, but it is often not fully understood. To define lift as it relates to stud welding:
Lift is the action of raising the item to be welded (often a stud) off of the work piece a preset distance.
This sounds simple enough, right?
In actuality there are many things going on simultaneously that all happen in a split second. Once the system (power source and connected gun) receives a “go” signal things are set in motion. This “go” signal can be a trigger pull or a signal from a PLC or Robot to initiate the weld sequence. Once initiated the power source sends out a trickle current (10-40Amps) to establish current flow. If this current is too big, the stud will create a spot weld and stick. In the trade we like to call that a “sticker”. If it is too small, establishing the arc may fail. Once the trickle current is flowing the gun (weld tool/weld head) will begin to raise the stud off of the work piece. As the stud breaks contact with the work piece the power source increases current flow to begin the weld. This lifting action stops at a predetermined distance. This is often a hard stop, but can also be programmed with stepper motors and the like. This final lift distance is the welding arc length.
The welding arc length controls the voltage during weld. A longer arc length creates a higher weld voltage. A shorter arc length has a lower weld voltage.
MIG, TIG and Stick welders instinctively know this and they vary the distance they are holding the electrode away from the work during the welding process. In stud welding the same process happens in 1/3 of a second!