"Should we integrate acoustic inspection directly into the line, or set up a separate test station?" This question arises in nearly every project. The right answer depends on five factors.
Definition
Inline: station is part of the line, every part inspected at takt time, traceability via MES.
Offline: separate station, manual or robot loading, often 100 % or sampling, loosely coupled.
The five criteria
1. Cycle time: inline must beat line takt (4–60 s typical). Below 4 s, parallelisation needed.
2. Investment: inline 90–345 k€, offline 55–190 k€ typically.
3. Staffing: inline runs personnel-free; offline needs 0.2–1.0 FTE per shift.
4. Traceability: inline provides seamless real-time linkage; offline has data breaks.
5. Flexibility: offline handles 5–20 part types easily; inline is fixed.
5-year example calculation
1.5 M parts/year, 8 s takt time.
| Position | Inline | Offline |
|---|---|---|
| CAPEX | 200 k€ | 120 k€ |
| Staff (5 yr) | 80 k€ | 620 k€ |
| Maintenance | 75 k€ | 40 k€ |
| Double-handling damage | 0 € | ~25 k€ |
| Complaint savings (100 %) | −180 k€ | −180 k€ |
| 5-year total | 175 k€ | 625 k€ |
Inline amortises in ~18 months at this volume. Below 200 k parts/year, offline wins.
Hybrid strategy
Inline for main series, offline for special variants. Line stays economic, special parts do not bloat the inline configuration.
