Hold Time Long

Definition

Hold time is the amount of time programmed into the weld controller, typically between the end of weld time and the command to open the electrodes (see figure).

Description

Hold time allows the weld to solidify before the electrodes are removed. If the cooled electrodes are kept in contact with the workpiece for too long, an unacceptable weld may result in some materials, a condition Hold Time Sensitivity. This is sometimes seen in hardenable metals, in which the excessive quenching effect of the extended hold time can create brittle phases in the cooling weld.

Detection

Detectable evidence may include:

• Brittle Weld
• Interfacial Separation
• Sticking/Stuck Tips
• Excessively long tip-on-workpiece contact times

Significance

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

Quality: Brittle welds may be produced in hold time sensitive materials.

Throughput: Long hold times affect the overall weld time, potentially increasing station cycle time, thereby lowering throughput.

Subordinate Causes

• Improper hold time value programmed in weld schedule
• Faulty weld cylinder
• Faulty gun closing valve operation