Issue: Sticking or Stuck Electrodes

Sticking is a term that refers to the tendency of the electrode tip to adhere to the workpiece.

Same as: Electrode 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.

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 faces not parallel to workpiece
• Hold time long
• Incorrect material/coating
• Weld current high
• Weld force low
• Wrong tips

Weak Possibilities

• Defective air or hydraulic system
• Excessive sealer
• Incorrect cylinder
• Incorrect electrode dressing
• Incorrect hoses
• Incorrect workpiece selected
• Insufficient cooling
• Poor electrode follow-up
• Weld time long
• Wrong cable/shunts
• Wrong transformer

Other Possibilities

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