Weld Quality Inspection with AI: Visual, Ultrasonic and Data

By James C on October 21, 2026

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A robotic seam weld can look perfect from the outside and still hide a lack of fusion at the root. Another can carry an undercut that nobody spots until the part reaches final inspection. Each inspection method sees only part of the story: cameras see the surface, ultrasonic testing sees inside, and the arc data shows what happened while the weld was made. Weld quality inspection with AI joins all three for every seam. See it on real weld data in a short weld QC demo.

AI VISION · ROBOTIC SEAM WELDING

Surface, Inside and Arc Data for Every Seam, in One Record

iFactory Weld QC AI runs bead vision models and tracks weld current and voltage signatures per seam. When a signature goes abnormal, it raises an NCR with the images attached.

Robot cell 2 · Seam S3NCR raised
Fillet weld, 6 mm leg · MAG · part 48-1172
V
Bead visionUndercut 0.6 mm at 210–240 mm
A
Arc signatureVoltage +2.1 V over window, same section
U
PAUTNo planar indication found
NCR-22913 images · arc trace · seam position attached
Routed to weld cell lead for disposition
WELD DEFECT DETECTION

Where Each Weld Defect Lives

Weld defects are easier to manage once you know where they sit in the joint. Some break the surface, some hide inside the weld metal and some sit at the root, out of sight. That location decides which inspection method can find them, which is why porosity detection at the surface and inside the weld needs different tools. ISO 6520-1 gives the common names and reference numbers for these imperfections. Review the defects your welds produce most with our weld quality team.

Surface
UndercutA groove melted into the base metal at the weld toe
Surface porosityGas pores that break the bead surface
CracksLinear breaks, often at the toe or crater
Inside
Buried porosityGas trapped as the weld metal solidifies
Incomplete fusionWeld metal not fused to the sidewall or a previous pass
Root
Lack of penetrationWeld metal does not reach through the joint root
Root cracksCracks starting at the unfused root
VISUAL, ULTRASONIC AND DATA

Which Method Sees Which Defect

No single method covers every defect. Vision is fast and covers every seam, but it only sees the surface. Ultrasonic testing finds planar defects inside the joint, but takes longer per seam. Arc data costs almost nothing to collect and covers every weld, yet it shows conditions that cause defects rather than the defects themselves. The matrix shows typical coverage. Map it to your joints in a coverage review.

Defect
Bead vision
Arc signature
Ultrasonic (PAUT)
Undercut
Measures depth
High voltage or speed
Not its job
Surface porosity
Sees pores
Unstable arc, gas loss
Limited
Buried porosity
Cannot see
Unstable arc, gas loss
Volumetric, often seen
Incomplete fusion
Cannot see
Low heat input
Planar, well suited
Lack of penetration
Only if root visible
Low current or fast travel
Root indication
Cracks
If surface-breaking
Weak link
Planar, well suited
ACCEPTANCE CRITERIA

What "Good Enough" Means Under ISO 5817 and AWS D1.1

AI does not decide what is acceptable. Your code and your customer do. ISO 5817 sets three quality levels for fusion welds in steel, nickel and titanium: B is the most stringent, C intermediate and D moderate. The visual acceptance criteria in Clause 8 of AWS D1.1 set limits for structural steel, for example no cracks at all and undercut up to 1/32 in (1 mm) on statically loaded members under 1 in thick. Always work from the edition named in your contract. Load your own limits with our support team.

Level B
StringentSmallest allowances for undercut, porosity and shape
Level C
IntermediateCommon choice for general structural work
Level D
ModerateLargest allowances, still finite limits
How iFactory uses the limits

Each seam is linked to its quality level or code clause. Bead vision measurements are compared with those limits, and anything outside them is routed for human disposition.

WELD BEAD VISION

What a Seam Camera Actually Measures

Weld seam inspection on robotic cells usually combines a laser line profile with 2D images. The laser profile gives geometry: bead width, reinforcement height, undercut depth and toe angle, measured along the whole seam. The 2D image shows surface pores, spatter and craters. Trained vision models then label what they find and where. Plan camera positions with our vision engineers.

AUndercut at the toeDepth compared with the level's limit
BBead widthToo narrow can mean fast travel or low heat
CReinforcement heightExcess or underfill against the drawing
DSurface flawsPores, spatter and craters from 2D images
WELDING PARAMETER MONITORING

Arc Signatures and the Heat Input Check

Every robotic seam produces a stream of current, voltage, wire feed speed and travel speed. Comparing that signature with a known good seam shows where conditions moved. Heat input ties it together. Arc energy is V × I × 60 ÷ (1000 × travel speed in mm/min), in kJ/mm, and heat input multiplies that by a process efficiency factor: 0.8 for MAG and MIG, 0.6 for TIG and 1.0 for submerged arc. The worked numbers below are illustrative. Check your own WPS windows with our welding specialists.

Normal seam
Voltage × current28 V × 260 A
Travel speed450 mm/min
Arc energy28 × 260 × 60 ÷ 450,000 = 0.97 kJ/mm
Heat input, MAG k = 0.80.97 × 0.8 = 0.78 kJ/mm
Travel speed fault
Voltage × current28 V × 260 A
Travel speed600 mm/min
Arc energy28 × 260 × 60 ÷ 600,000 = 0.73 kJ/mm
Heat input, MAG k = 0.80.73 × 0.8 = 0.58 kJ/mm
Assumed WPS window 0.65 to 0.95 kJ/mm0.58 kJ/mm is below it, so the seam is flagged for fusion and penetration checks

One Abnormal Signature, One NCR, All the Evidence

iFactory runs bead vision models on every seam and tracks weld current and voltage signatures against known good welds. When a signature goes abnormal, it raises an NCR automatically with images and the arc trace attached.

Robot cell 2 · Weld lead and iFactory
Weld leadWhy did S3 on part 1172 get an NCR?
iFactoryUndercut of 0.6 mm between 210 and 240 mm, and voltage was 2.1 V above the window on the same stretch.
Weld leadIs it only this part?
iFactoryThe last four parts show the same voltage rise from 200 mm. Contact tip wear is a common cause. Images are on the NCR.
ULTRASONIC WELD TESTING

Phased Array UT in Plain Terms

Phased array ultrasonic testing uses a probe with many small elements. Firing them with tiny time delays steers and focuses the sound beam, so one probe position can sweep a range of angles through the weld. ISO 13588:2019 covers automated phased array testing of full-penetration welds from 6 mm thick. It defines testing levels but leaves acceptance levels to other standards. Plan where PAUT adds the most with our NDT specialists.

01
Many elementsEach fired with a set delay to shape and steer the beam
02
Sectorial scanOne probe sweeps several angles across the joint
03
Encoded recordPosition-linked data that can be stored and reviewed later
04
Planar defectsStrong at lack of fusion and cracks that vision cannot reach
FROM SIGNATURE TO NCR

What Happens When a Seam Goes Abnormal

An alert nobody acts on is just noise. iFactory turns an abnormal seam into a nonconformance record with the evidence already attached, so the weld lead can decide quickly and quality can see patterns later. People keep the disposition decision. Set up your NCR routing with our support team.

Seam finishesArc trace and bead images saved against part and seam ID
CompareSignature checked against the known good seam and WPS window
LocateAbnormal section matched to vision findings by position along the seam
Raise NCRImages, arc trace and seam position attached automatically
DispositionWeld lead chooses accept, repair, PAUT check or scrap
TrendRepeat NCRs grouped by robot, seam and consumable
WELD QUALITY INSPECTION AI TEMPLATE

A Seam Record Worth Keeping

Whether or not you use AI, every critical seam should leave a record like this. It makes NCRs faster to judge and audits easier to pass. Ask our weld QC team for a blank version.

Part and seamPart ID, seam ID, joint type
ProcedureWPS number and parameter window
Quality levelISO 5817 level or code clause
Robot and torchCell, program, contact tip count
ConsumablesWire and gas batch
Arc traceCurrent, voltage, wire feed, travel speed
Heat inputCalculated per seam section
Vision resultsProfile values and labelled images
NDTPAUT result where required
DispositionDecision, who made it and when
WELD QUALITY INSPECTION AI EXAMPLES

Three Seams, Three Different Clues

These illustrations show how combining evidence changes the response. They are not case studies. Walk through your own recent weld NCRs with our quality engineers.

Vision and arc agree
Undercut with a voltage riseBoth point to the same section. The tip is changed and the next seams return to normal.
Only the arc sees it
Low heat input, bead looks fineA travel speed fault cuts heat input. The seam is sent for PAUT, which confirms sidewall lack of fusion.
Only vision sees it
Surface pores, normal arcPores cluster on one fixture station. A draught from an open door is disturbing gas cover.
WELD QUALITY INSPECTION AI COST AND ROI

A Sizing Worksheet for Plant Managers

The value of robotic weld quality monitoring comes from defects found at the cell instead of at final inspection or at the customer. Every input below is an assumption to show the arithmetic only. Replace each one with your own figures, or build the case with our ROI specialists.

Welded parts per month20,000, assumed
Parts with a weld defect found late0.5%, assumed
Late finds per month20,000 × 0.005 = 100
Share caught at the cell instead60%, assumed
Parts caught earlier per month100 × 0.6 = 60

Multiply by the difference between a repair at the cell and one found downstream, then add fewer PAUT checks on seams with clean signatures where your code allows it.

WELD QUALITY INSPECTION AI IMPLEMENTATION GUIDE

Start With One Robot Cell

A focused pilot proves the value faster than a plant-wide launch. Pick a cell with known weld issues, collect evidence first and switch on NCRs only when signatures are trusted. Scope your pilot cell with our support team.

1Choose a cell with a known defect history
2Record arc data and images on known good seams
3Compare signatures with PAUT and visual results
4Switch on automatic NCRs and review weekly
TURNKEY AI DEPLOYMENT

Seam Cameras, Arc Monitoring and NVIDIA Server in One Package

iFactory delivers Weld QC AI as a turnkey bundle. Seam cameras and arc data connections are installed at the robot cells, and a pre-configured NVIDIA AI server ships racked and ready with the bead vision and signature models pre-loaded, so every seam is checked on site. You rack it, plug in power and Ethernet, and the AI is live. To scope it for your weld shop, request a turnkey quote.

What's Included
  • Pre-configured NVIDIA AI edge server, racked and ready
  • Laser profile and 2D seam cameras with spatter protection
  • Arc data links for current, voltage, wire feed and speed
  • Bead vision models trained on your joints
  • Heat input checks against each WPS window
  • Automatic NCRs with images and arc traces
  • 24×7 remote monitoring of models and hardware
Live in 6–12 weeks
Wk 1–4
Install and Record

Cameras, arc data links and server installed, good seams recorded.

Wk 5–8
Train and Compare

Bead models trained, signatures checked against PAUT and visual results.

Wk 9–12
NCRs and Training

Automatic NCRs switched on, weld leads and quality teams trained.

HOW iFACTORY FITS

Weld Quality You Can Trace Seam by Seam

iFactory brings surface, inside and process evidence together for each robotic seam. Our support team can walk you through a pilot plan.

1
Runs bead vision models. Undercut, pores, width and height are measured along every seam.
2
Tracks arc signatures. Weld current and voltage are compared per seam with known good welds.
3
Raises NCRs automatically. Abnormal signatures open an NCR with images and the arc trace.
4
Links in ultrasonic results. PAUT findings sit in the same seam record.
1000+
Industrial clients running iFactory
99.9%
Platform uptime for production weld cells
6-12 wks
From racked server to live seam records
FREQUENTLY ASKED QUESTIONS

What Plant Managers Ask About Weld Quality Inspection with AI

Can AI vision find incomplete fusion?
Not on its own. Incomplete fusion and lack of penetration usually sit inside the joint, out of a camera's view. Arc data can show the conditions that cause them, such as low heat input, and ultrasonic testing can confirm them. That is why iFactory combines all three.
How is heat input calculated?
Arc energy in kJ/mm is voltage × current × 60 divided by 1000 × travel speed in mm/min. Heat input multiplies arc energy by a process efficiency factor, such as 0.8 for MAG and MIG or 0.6 for TIG. Check which value your code and WPS use, because some codes use arc energy directly.
Does this cover spot welds?
This page focuses on arc welding, especially robotic seam welds. Resistance spot welds are monitored differently, using current, force and electrode data, and are handled by separate iFactory spot weld quality tools.
Does the system accept or reject welds by itself?
No. It measures, compares with your quality level or code limits and raises an NCR when something is outside them. A weld lead or inspector makes the disposition decision, and that decision is logged on the record.
Can it reduce how much PAUT we do?
Possibly, but only where your code and customer allow it. Some plants use clean arc signatures and bead results to focus PAUT on seams with abnormal evidence. Any change to an NDT plan should be agreed with your quality and customer representatives first.
What do we need to start?
A robot cell with access to its weld data, a place to mount seam cameras and a set of known good seams to learn from. Our support team can check your cell and welding power sources before the pilot.

Catch the Weld Defect at the Cell, Not the Customer

Combine bead vision, arc signatures and ultrasonic results in one record per seam, and get NCRs with images when something goes abnormal. The full system is delivered turnkey and goes live in 6 to 12 weeks.

Example shift summary · Robot cell 2
Seams recordedEvery seam, every part
Bead visionProfile and surface checks
Arc signaturesCompared with known good seams
NCRsRaised with images, decided by people
Every seam traceable from robot to result

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