How to Troubleshoot Expulsion in Wire Mesh Resistance Spot Welding

Expulsion is the ejection of heated metal from a resistance weld region. It can leave a damaged intersection, deep indentation or an inconsistent joint, but a visible burst alone does not identify the cause. A useful investigation checks contact and force delivery before changing electrical settings, then verifies both joint strength and finished mesh dimensions.

Locate when and where the event occurs

Record whether the event happens at first energisation, later in the weld pulse or repeatedly at one position. Distinguish expelled metal from loose scale or debris displaced at electrode contact. Note the wire lot, intersection location and machine recipe. Stop and inspect under the machine's approved procedure; do not place hands or inspection tools inside an active welding area.

Inspect intersection fit and contamination

Check whether crossing wires sit together before force is applied. Bowed wire, inconsistent spacing or a fixture that holds one wire away can change local contact. Compare a troublesome intersection with a stable one. Look for oil, loose scale or an unexpected coating change. Restore the approved material preparation method rather than improvising a cleaning process that alters the surface inconsistently.

Check the electrode system

Inspect tip shape, alignment, seating and cooling condition against the machine instructions. An uneven contact face may concentrate current differently from the approved setup. Establish when the tips were last maintained and whether problems increase with running time. For maintenance detail, consult wire mesh welding quality and electrode wear before deciding whether dressing or replacement is appropriate.

Verify force and squeeze timing

Confirm that the electrodes establish the required contact before current begins. A regulator setting alone does not prove the force delivered at the joint. Check actuator response, fixture resistance and any delays after a restart. The comparison of pneumatic and servo electrode force helps frame questions about what the system actually measures and controls. Use qualified personnel for force measurement and adjustment.

Review the electrical recipe after mechanical checks

Compare actual settings with the approved current, weld time and pulse sequence. Excessive heat input relative to the joint condition can contribute to expulsion, but lowering current indiscriminately can leave an inadequate weld. Check for an unintended recipe change or a material change first. Do not transfer a setting from another wire diameter or coating without qualification.

Change one variable in a controlled trial

Start from the last acceptable setup when available. Hold material, fixture and electrode condition constant while changing one approved parameter at a time. Label every trial coupon and record the result. Use the manufacturer's permitted adjustment range and the site's welding procedure. If contact remains unstable, return to fit and force checks instead of compensating with repeated electrical changes.

Verify strength dimensions and surface together

Inspect indentation, cracking or material loss and perform the joint test specified for the product. A quiet weld can still be weak. Check panel flatness and spacing after the complete weld sequence, not just after a single intersection. The guide to reducing wire mesh deformation during resistance welding covers this separate dimensional concern.

Save the correction and recurrence conditions

Record the accepted recipe, wire lot, tip condition, force verification method and test results. Define the inspection interval and the signs that trigger a check. When reviewing replacement equipment, use Jinchun's automatic multi spot row welding machine page to discuss electrode access, monitoring and your actual mesh sample. Require a representative joint trial rather than accepting appearance alone.

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