Engineering Field Guide No. 001MIG Troubleshooting

Control the variables. Find the cause. Verify the result.

Revision 2.0 | 2026-07-30

Start with the symptom, not the knob. Record the approved baseline, change one variable at a time, and confirm the result on a controlled test piece before returning to production.
1

Define the Problem

  • Identify the exact defect, instability, or discontinuity.
  • Note when it started and what changed. Return to the last confirmed process change.
  • Separate appearance concerns from the applicable acceptance criteria for weld soundness.
  • Photograph or retain the defect or discontinuity and any other visual clues, including secondary-cable connections.
2

Verify the Approved Setup

  • Confirm the approved WPS, base metal, and joint design.
  • Verify filler-metal type, diameter, and classification.
  • Confirm shielding-gas type and mixture.
  • Verify polarity and work-lead connection.
  • Perform a visual inspection of the entire system from "tip to barrel."
3

Inspect the Wire Delivery System

  • Check spool condition, hub tension, and wire condition.
  • Verify drive-roll type, size, pressure, and wear.
  • Inspect inlet and intermediate guides, conduit connections, and fittings.
  • Check the liner to ensure it is cut to the proper length. Improper liner length can cause wire-slippage and feeding problems.
  • Inspect the contact tip for wear and proper bore size. The wire can arc inside the contact-tip bore and cause burnback; this is called micro-arcing.
  • Release drive-roll tension and pull the wire from the contact tip to evaluate total delivery-system drag. A typical target is approximately 3-5 lb of pull force.
4

Check Shielding Gas

  • Confirm that the cylinder or bulk gas supply is available.
  • Measure shielding-gas flow at the gun, not only at the regulator.
  • Inspect hoses, fittings, O-rings, diffuser, and torch for cuts, leaks, damage, or improper assembly.
  • Remove nozzle spatter and verify proper nozzle seating.
  • Control drafts, fans, and excessive shielding-gas flow.
  • Measure air movement at the weld joint with an anemometer. Less than approximately 3 mph of draft is ideal where practical.
5

Measure Electrical Variables

  • Record actual arc voltage and wire-feed speed.
  • Check contact-tip-to-work distance (CTWD); CTWD affects amperage.
  • Verify travel speed and gun angle.
  • Inspect the work cable, secondary-cable connections, and cable size.
  • Use 4/0 secondary cable for pulse applications where required by approved equipment and application guidance.
  • Compare all readings with the approved baseline.
6

Confirm Material Condition

  • Remove oil, rust, scale, paint, and moisture from the weldment as required.
  • Verify fit-up, root opening, and alignment are within the WPS.
  • Check preheat and interpass temperature per the WPS.
  • Confirm wire and base metal were stored dry.
7

Test One Change

  • Choose the most likely root cause only after the previous items have been validated.
  • Change only one variable at a time.
  • Weld a controlled test piece instead of a production part whenever possible.
  • Record the settings, the single change made, and the observed result.
8

Lock In the Result

  • Verify weld acceptance using the applicable criteria: visual inspection, cut/etch, quality procedure, or another approved method.
  • Ensure all parameters remain within the WPS.
  • Document the root cause and corrective-action plan.
  • Standardize the corrective action across the manufacturing facility where applicable.

UYWP Diagnostic Flow

Define the symptom→Verify the approved WPS and setup→Inspect the wire-delivery system→Verify shielding gas→Measure electrical variables→Confirm material condition→Test one variable→Document and standardize the result
UYWP Engineering Principle
The best troubleshooters do not guess. They identify the symptom, verify the variables, measure the process, and document the solution.

Field Notes

Stop and escalate: If the approved WPS may be incorrect, the equipment is unsafe, the defect is code-related, or the corrective action requires changing qualified variables, involve the responsible welding engineer, CWI, or quality authority.
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