A during-production inspection (DPI) checks the goods and the process while the order is being manufactured, so problems can be fixed while the line is still running. A pre-shipment inspection (PSI) verifies the finished, packed lot before it leaves the factory. Which one you need depends on the risk of the order.
- DPI suits complex products, large orders, new suppliers and high quality requirements.
- PSI suits standard products, repeat orders and final shipment approval.
- High-risk orders should combine both — the inspection plan should follow the risk.
What Is a During Production Inspection?
A during production inspection takes place while the order is being manufactured, usually after a defined share of the goods is done (for example 20–30% of the quantity). It checks both the products coming off the line and the conditions they are being made under.
A DPI typically covers:
- Production status. Whether production has actually started, how much is complete, and whether the schedule is on track.
- Process issues. Whether the line is running to the approved process and work instructions.
- Early defects. Whether defect levels are within limits before the whole order is built.
- Assembly problems. Whether fit, function and finish issues are appearing in real parts.
The value of a DPI is that it happens while correction is still possible. A defect found at 25% completion can be fixed for the remaining 75%; the same defect found at pre-shipment means rework or a rejected shipment.
What Is a Pre-Shipment Inspection?
A pre-shipment inspection is the final check on the finished goods before they leave the factory. It is typically performed when production is complete and the goods are packed, using a sampling plan to judge the whole lot.
A PSI typically covers:
- Finished products. Appearance, dimensions and function against the approved sample and specification.
- Quantity. Count verified against the packing list and the order.
- Packaging. Inner and outer packaging, protection, and carton condition for transit.
- Labeling. Marks, labels, barcodes and documentation match the order requirements.
- Final quality requirements. Acceptance criteria applied to the sampled pieces under the agreed standard.
A PSI is a gate: the lot passes or fails before shipment. It is the last chance to catch a problem while the goods are still at the factory, where they can be reworked or replaced.
Pre-Shipment vs During Production: The Comparison
| Dimension | During Production Inspection | Pre-Shipment Inspection |
|---|---|---|
| Timing | Mid-production, e.g. 20–30% complete | After production, before shipment |
| Purpose | Find and correct problems while the line is running | Approve or reject the finished, packed lot |
| Advantages | Time to fix defects, verify process, check schedule | Verifies final quantity, packaging and compliance |
| Limitations | Cannot see the finished, packed lot | Too late to fix; only tells you the lot is good or bad |
The two inspections do not replace each other. A DPI looks at the process and early output; a PSI looks at the final result. Choosing between them is a question of risk, not preference.
When Buyers Should Use During Production Inspection
Use a DPI when the cost or difficulty of fixing a problem rises sharply after production is complete:
- Complex products. Multi-part assemblies, electronics or products with many function tests deserve a mid-production check.
- Large orders. With a lot of value at risk, an early checkpoint protects the majority of the run.
- New suppliers. Until a supplier has proven consistency on your product, verify while the line is running.
- High quality requirements. Certified or safety-critical products should be checked before the whole order is committed.
A DPI should be timed after enough production to see real output but early enough to act — typically when 20–30% is complete.
For an electronic product with function tests, a DPI can catch a calibration or firmware problem while the supplier still has the line open and the components on hand. The same problem found at pre-shipment would mean rework of the whole lot and a schedule hit.
When Buyers Should Use Pre-Shipment Inspection
Use a PSI when the main question is whether the finished lot matches the order:
- Standard products. Products the supplier has made before with a stable process need a final verification rather than mid-production intervention.
- Repeat orders. Once a supplier has proven consistency, a final lot check is usually sufficient.
- Final shipment approval. Even with a DPI already done, a PSI confirms quantity, packaging and labeling before goods leave.
A PSI is also the natural choice when the supplier's process is already verified and the order is simple. It protects the shipment at a fraction of the cost of a full inspection program.
Combining Both: A Risk-Based Inspection Strategy
Most buyers do not need to inspect every order with both methods. The practical approach is to match the inspection plan to the risk:
| Order risk profile | Recommended plan |
|---|---|
| New supplier, complex product, or large order | DPI + PSI on the first one to two orders, then relax based on results |
| Medium risk: some complexity, moderate volume | PSI with expanded sampling, plus one mid-production check on key components |
| Low risk: standard product, repeat supplier | PSI only, with periodic spot DPIs to confirm the process has not drifted |
The plan should be written into the order before production starts, with the sampling standard and the criteria defined. Risk-based inspection is a tool for concentrating attention where a failure would hurt most — not for inspecting everything at maximum intensity.
A practical example: a buyer ordering an electronic appliance from a new supplier scheduled a DPI at 25% completion and a PSI before shipment. The DPI caught a calibration error and a labeling mistake while the line was still open; both were corrected before the remaining 75% ran. The PSI then confirmed the finished lot, quantity and packaging. The cost of the two inspections was a small fraction of the rework and delay a PSI-only plan would have required on the same order.
For how defects are classified and counted under a sampling plan, see our guide on AQL inspection explained and on defect classification in manufacturing.
Common QC Planning Mistakes
Relying on PSI only for new suppliers
A final inspection on a bad first order only confirms the loss; a DPI would have caught it early enough to fix.
Inspecting too late to act
Scheduling the check after the line has closed removes the main benefit of inspection — the chance to correct.
No written criteria
Inspecting without a defined sampling plan and acceptance criteria leaves the result open to argument.
Ignoring packaging and labeling
A lot can pass on appearance and fail in transit because packaging or labels were never checked.
Not recording results
Without records, you cannot track a supplier's trend or defend a reject decision later.
Practical Takeaway
Inspection timing decides how useful the result is. Use a during-production inspection where problems are expensive and fixable only during the run; use a pre-shipment inspection to approve the finished lot; and combine both when the order is new, large or complex. Define the plan and the criteria in writing before production starts, and let the risk profile — not habit — decide the checkpoints.