Industrial machine vision is standard on many lines – dimensions, surface inspection, completeness. Acoustic methods complement it on a completely different level: the inside of the part. Combined cleverly, more is inspected in less time.
What does vision see, what does acoustics see?
Vision: anything visible or near-IR – dimensions, colours, surface cracks, contamination, completeness, prints. 3D vision measures heights to µm.
Acoustics: anything reflected in vibration – internal cracks, voids, material mix-up, heat treatment defects, density variation, functional issues.
Comparison matrix
| Criterion | Machine vision | Acoustic testing |
|---|---|---|
| Surface defects | ★★★★★ | ★☆☆☆☆ |
| Internal defects | not visible | ★★★★★ |
| Dimensional | ★★★★★ | indirect (via natural freq.) |
| Functional assessment | not possible | ★★★★★ (NVH) |
| Material mix-up | surface only | integral, very reliable |
| Inline speed | 0.01–0.5 s | 0.2–2 s |
| False positive rate | often 1–5 % | 0.1–1 % |
| Investment | 20–200 k€ | 30–250 k€ |
Why vision alone is often not enough
Vision sees only what optics images. Voids in castings, hardness variations, sub-surface micro cracks, identical-looking material mix-ups – all invisible.
Why acoustics alone is often not enough
Conversely, acoustics misses contamination, missing print, dimensional deviations or surface defects < 2 mm.
Combined: 100 % coverage with two fast stations
- Vision station: dimensions, completeness, surface cracks, contamination – 0.3 s/part.
- Acoustic station: internal defects, heat treatment, material mix-up – 0.8 s/part.
Both fit a 3 s line. Result: near 100 % defect coverage across both worlds.
