Weld Force Low

Definition

The interfacial welding force is less than that required by the applicable specification.

Description

Weld force brings the metal between the electrodes together and provides electrical continuity, the required welding pressure, and forging force, so that a weld may be generated. The lower the force, the higher the interfacial resistances, resulting in higher heat generation at the tip to sheet and sheet to sheet interfaces.

On a microscopic scale, the surfaces of electrodes and workpieces consist of peaks and valleys. When subjected to low force, the metal-to-metal contact will be only at the contacting peaks. The resulting contact area is less than that produced by an appropriate force. Contact resistance will therefore be higher, causing a greater amount of heat to be generated.

Measured weld force: That value of weld force set, for example, using a force gage, before the workpiece is introduced.

Interfacial weld force: That force actually present at the sheet to sheet interface. This is equal to the measured weld force minus the force required to overcome poor fit up.

Detection

The condition may be indicated by:

Significance

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

Subordinate Causes

Poor Mechanical Connection
Wrong Cables/Shunts
Air or hydraulic fitting loose
Air or hydraulic leak
Air or hydraulic pressure low
Contaminated bearings or bushings
Kinked or broken hose
Leaking cylinder - Piston or rod seals bad
Wrong electrodes or shanks installed (too short for the cylinder stroke)
Wrong force selected for the material / stack-up