Shop-floor diagnosis
Defect Troubleshooting Table
Trace weld defects from visible symptoms to first controlled checks, adjustment choices, section triggers, and next-step validation.
Start withThe symptom
Use the visible defect to choose the first check instead of changing every setting.
First ruleChange one variable
Avoid changing power, speed, focus, and gas all at once.
Stop pointSection or escalate
Hidden defects, cracks, and repeated failures need sectioned evidence before release.
Start with the visible defect, then isolate one variable
Use the defect as a routing signal. Check surface, fit-up, shielding, focus, and path control before changing the full power-speed recipe.
- Do not change power, speed, focus, and gas together.
- Stop and section cracks, repeated porosity, and drifting penetration.
- Keep rejected settings because they define the usable process edge.
Laser weld defect troubleshooting chart
Use this matrix before widening a parameter window. The first check should confirm whether the problem is preparation, shielding, path control, fixture contact, or heat input.
| Visible defect | Common checks | First check | Controlled adjustment | Stop and section when |
|---|---|---|---|---|
| Porosity | Surface contamination, oxide or moisture, shielding disruption, and keyhole stability. | Repeat after controlled cleaning and gas-flow/nozzle verification | Adjust the power-speed pair only after preparation and shielding are confirmed | Pores persist after cleaning and shielding checks or appear below the surface |
| Cracking | Material susceptibility, restraint, cooling condition, contamination, and weld sequence. | Check material certificate, joint restraint, specified thermal controls, and weld sequence | Reduce restraint, adjust the thermal strategy, or change sequence under the project specification | Any crack is visible or sectioning shows crack initiation at fusion line or HAZ |
| Undercut | Toe geometry, edge gap, beam position, focus height, and delivered power density. | Measure edge fit-up, toe location, beam alignment, and focus height | Adjust travel behavior or power density while tracking penetration | Toe defect remains while penetration is already near the upper limit |
| Spatter or expulsion | Local energy concentration, surface state, plating condition, and contact repeatability. | Check surface state, clamp contact, plating, and whether absorption changes after first pulse | Reduce peak energy concentration or adjust pulse rise while holding clamp force | Expulsion damages nearby layers or creates inconsistent bonded area |
| Lack of fusion | Delivered heat, oxide barrier, joint gap, focus, path alignment, and heat sinking. | Verify focus, joint prep, local gap, material thickness, and delivered spot size | Increase delivered energy in small steps or improve joint preparation | Depth varies along the same seam or root fusion cannot be confirmed visually |
| Distortion | Total heat input, fixture support, weld sequence, and fixture temperature. | Record part movement, fixture temperature, and sequence before changing recipe | Reduce total heat input, split sequence, or improve heat sinking | Geometry change affects assembly fit or repeats after fixture cooldown |
Defect triage table
| Symptom | Checks to make | First checks |
|---|---|---|
| Porosity | Surface cleanliness, oxide or moisture, shielding coverage, and keyhole stability. | Clean surface, verify gas flow/nozzle angle, reduce speed, and section a sample. |
| Cracking | Material susceptibility, restraint, thermal strategy, contamination, and weld sequence. | Check material certificate, specified thermal controls, weld sequence, restraint, and any post-weld treatment requirement. |
| Undercut | Toe profile, beam alignment, focus height, edge gap, and power density. | Adjust travel behavior or focus, verify fit-up, and inspect the weld toe. |
| Spatter / expulsion | Peak energy concentration, contaminated surface, local contact change, or unstable absorption. | Clean surface, lower peak power, adjust pulse shape, and verify clamping. |
| Incomplete fusion | Delivered heat, focus, joint gap, oxide barrier, heat sinking, and path alignment. | Increase delivered energy carefully, improve joint prep, and confirm penetration by sectioning. |
Variable isolation sequence
| Sequence | Action | Result to compare |
|---|---|---|
| 1. Surface and fit-up | Clean the same way, reclamp, and confirm gap/mismatch before changing settings. | If the defect disappears, keep the process row and tighten preparation controls. |
| 2. Shielding | Verify gas type, purity, flow, nozzle distance, angle, and backside/trailing coverage. | If oxidation or porosity changes, document the gas setup as a process variable. |
| 3. Focus and path | Check focus height, spot position, beam alignment, robot path, and acceleration zones. | If the defect follows corners or starts/stops, tune path control before heat input. |
| 4. Power-speed pair | Adjust power or speed in small steps while holding all previous checks constant. | Compare bead shape, penetration, HAZ, and defect frequency after each step. |
| 5. Thermal strategy | Review preheat, interpass temperature, heat sinking, weld sequence, and restraint. | Use when cracks, distortion, hardness, or HAZ width remain the limiting issue. |
Stop and section when
| Signal | Reason | Action |
|---|---|---|
| Cracks appear | A surface crack can indicate metallurgical or restraint failure, not a cosmetic issue. | Stop release, section the sample, and review material/preheat/restraint assumptions. |
| Porosity persists after cleaning and gas checks | The pore source may be trapped contamination, keyhole instability, or material condition. | Section representative samples and compare pore location to the weld pool geometry. |
| Penetration varies along the same seam | Path height, fixture movement, or heat buildup may be changing during the weld. | Cut start, middle, end, and any corner or speed-transition location. |
| A correction fixes one defect and creates another | The process is at a window boundary, not a stable center point. | Build a smaller matrix around the last passing setting and record rejected edges. |
Next engineering checks
Surface Quality EstimatorEstimate roughness, visible imperfections, and quality-level planning against ISO 13919 references.Crack Risk CalculatorScreen material, carbon equivalent, restraint, and cooling assumptions for crack risk.Multi-Variable AnalyzerCompare power, speed, focus, gas, and material interactions for early parameter selection.Weld Quality Inspection GuideConnect ISO 13919 quality levels with shop-floor inspection steps for visible weld outcomes, section checks, records, and process-window decisions.Material Preparation GuidePrepare common laser welding materials with surface cleaning, oxide control, fixture checks, shielding readiness, and crack-risk planning.
Applicable standards
Confirm final requirements against the current standard text, workplace procedure, and project specification before releasing production settings.