Additive manufacturing and near-net-shape production · reference card
Monitoring for wire arc additive manufacturing
WAAM is welding with no interpass inspection access and no wrought equivalent to compare against. The codes that apply, the four monitoring pain points, and which Therness signal addresses each.
- Industry
- Additive manufacturing and near-net-shape production
- Dominant processes
- Gas metal arc directed energy deposition, including cold metal transfer variants; Gas tungsten arc deposition with cold or hot wire feed; Plasma arc deposition for titanium and nickel alloys
Wire arc additive manufacturing inherits every process variable of arc welding and removes the two things welding relies on to stay in control: a large parent mass that absorbs heat, and access to inspect the joint before the next run covers it.
The consequence is that WAAM control is thermal control. Interlayer temperature is not one variable among many; it is the variable that ties deposition rate, geometry, microstructure and residual stress together, and the standard remedy — a dwell between layers — is either a guess based on a timer or a decision based on a measurement. Only one of those two scales to a build that runs for hours.
Qualification pushes in the same direction. A deposited part has no wrought equivalent to be compared with, so the argument that it is sound rests substantially on evidence that the process stayed inside its qualified envelope for the entire build. A build package with a complete per-layer record is a different conversation from one with a coupon and a signature, and that difference is often what a buyer’s acceptance turns on.
Governing codes
| Code | Why it applies |
|---|---|
| AWS D20.1 | Specification for fabrication of metal components using additive manufacturing by arc directed energy deposition. |
| ISO/ASTM 52900 series | Terminology and the general framework additive standards are written against. |
| ISO 3834-2 | The welding quality system underneath the deposition process, since WAAM is arc welding by another name. |
| Customer-specific qualification | Aerospace and energy buyers commonly impose their own build and witness requirements on top of the published standards. |
Monitoring pain points
| Pain point | Consequence | Signal that sees it |
|---|---|---|
| Heat accumulates layer after layer with nowhere to go | Interlayer temperature climbs, the pool grows, wall geometry drifts and the microstructure at the top of the build differs from the bottom. | Interlayer temperature measured on every layer, and a dwell decision driven by that measurement instead of a fixed timer. |
| There is no inspection access between layers | An imperfection deposited early is buried under everything built after it, and the only remedy is scrapping or machining away hours of deposition. | Continuous per-layer thermal and parameter record, so a suspect layer is known when it happens. |
| Geometry drifts slowly and within tolerance until it is not | Machining allowance is consumed unevenly and a near-net-shape part becomes a scrap part late in the build. | Layer-to-layer bead width and height evidence, tracked as a trend rather than checked at the end. |
| There is no wrought equivalent to qualify the part against | Qualification rests on process evidence, so a build with thin records is difficult to accept whatever the coupons show. | A complete per-layer record retained for the whole build and exportable as part of the build package. |
What that means for the cell
- HeatCam IR-S compact thermal camera Built to be mounted close to a deposition head where a full-size camera does not fit.
- WAAM build monitoring The hub covering layer-to-layer drift and the evidence a build qualification needs.
- WeldTrace parameter acquisition Per-layer electrical and wire feed records, synchronised with the thermal signal for the build package.
Questions from additive manufacturing and near-net-shape production
Why is interlayer temperature more critical in WAAM than in multi-pass welding?
Because the part is the weld. In conventional welding a limited number of runs sit on a large parent mass that acts as a heat sink; in a deposition build every layer heats the layers underneath it and there is no separate mass to absorb it, so the thermal state changes continuously through the build.
Does a thermal record replace destructive testing of a WAAM build?
No. Qualification schemes still call for coupons and destructive checks. The record makes the case that the qualified build conditions were held for every layer, which is the part a coupon cut from one location cannot show.
Bring the evidence forward, not the inspection
Therness measures what happens while the arc is running — parameters, thermal signature, per-weld records — so the problems on this page surface on the shift that made them.
