Sticking/Stuck Tips

Definition

Sticking is a term that refers to the tendency of the electrode tip to adhere to the workpiece.
Same as: pick-up.

Description

Elevated temperature at the electrode/workpiece interface can produce alloying conditions. Zinc coating allows a zinc copper alloy to develop at the electrode tip, promoting adhesion of the tip to the workpiece.

When bare steel is welded, a carbon layer forms on the tip. This layer acts as a barrier to fusion of electrode and workpiece, thereby minimizing sticking.

Sticking may also result from melting and refreezing of the workpiece coating [e.g. zinc], prior to tip removal from the work piece. Detection

• Gun will not open
• Part pulled from fixture
• Gun open; Tips stuck to work piece
• Water flowing from electrode
• Machine control fault
• Irregular weld

Significance

Quality, Workplace Issues, Cost, Downtime, Maintenance, Throughput (cycle time; PPH) are all potentially affected by this condition.

Possible Causes

Strong Possibilities

• Electrode Face Not Parallel to Workpiece
• Hold Time Long
• Incorrect Material/Coating
• Weld Current High
• Weld Force Low
• Wrong Tips

Weak Possibilities

• Defective Air or Hydraulic Cystem
• Excessive Sealer
• Incorrect Cylinder
• Incorrect Electrode Dressing
• Incorrect Hoses
• Incorrect Workpiece Selected
• Insufficient Cooling
• Poor Electrode Follow-up
• Weld Time Long
• Wrong Cables/Shunts
• Wrong Transformer

Nonmatrix Possibilities

• Heavy galvanized coating
• Inadequate tip cooling
• Insufficient edge distance to weld
• Low clamping force
• Low conductivity tips