Cause: Hold Time Short

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Definition
Hold time is the period of time programmed into the weld controller, typically between the end of weld time and the command to open the electrode. The actual hold time is the amount of time for which the electrode force is applied after current ceases to flow.

Description
Hold time allows the weld to solidify before the electrodes are removed. If the electrodes are removed before the solidification process is complete the nugget may pull apart resulting in a substandard weld or no weld. Arcing may occur if current is still flowing when tips are removed (see figure).

Detection

• Brittle weld
• Cracks & holes
• Expulsion/burn through
• Interfacial separation
• Sheet metal may separate
• Arcing at end of weld
• Pre-mature tip wear

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

Subordinate Causes

• Insufficient cooling
• Weld controller improperly programmed (longer hold time required)
• Wrong weld schedule
• Incorrect workpiece material
• In some situations the gun closing valve and the weld current may be controlled by independent controllers. Short hold time may be caused by improper synchronization of these controllers.

Note
Similar symptoms may occur if there is inadequate cooling.