During production inspection (DPI) catches quality issues when they can still be fixed—before the entire batch is affected. Unlike pre-shipment inspection which evaluates finished goods, DPI occurs mid-production (typically at 20-30% completion), giving you the opportunity to identify and correct problems while there’s still time to adjust. This 2026 guide explains when DPI matters, what it checks, how it differs from other inspections, and how to implement effective during-production quality control for your China manufacturing.

What is During Production Inspection?

Definition and Timing

During production inspection (DPI), also called in-process inspection or DUPRO, occurs when production is partially complete—typically at 20-30% of the order quantity manufactured. Purpose: verify that production is proceeding correctly and identify issues before they affect the entire batch. Unlike PSI which is a final check, DPI is a process check that enables course correction. Timing is critical: too early (under 20%) and there’s not enough production to evaluate; too late (over 50%) and most of the batch may already be affected by any issues.

Why DPI Matters

DPI provides unique value that other inspection types cannot. Early detection: problems caught at 30% completion affect only 30% of the batch; caught at PSI, they affect 100%. Course correction: factory can adjust process, retrain workers, or change materials while production continues. Schedule protection: catching issues early prevents delays from reworking entire batch. Process verification: confirms factory is following agreed procedures. Cost savings: fixing issues mid-production is cheaper than rework after completion. For large or critical orders, DPI is essential risk management.

DPI vs Other Inspection Types

Aspect	PPI (Pre-Production)	DPI (During Production)	PSI (Pre-Shipment)
Timing	Before production	20-80% complete	100% complete
Purpose	Verify readiness	Catch issues early	Final verification
Correction ability	Prevent problems	Adjust mid-production	Limited (rework/reject)
Cost impact	Prevents issues	Minimizes affected units	Addresses finished goods

When DPI is Essential

Large Order Quantities

For orders of 1,000+ units, DPI becomes increasingly valuable. Reason: with large orders, a production problem affects many units. At 2,000 units, a defect affecting 30% means 600 defective units. DPI at 20% completion catches issues when only 400 units are affected. The larger the order, the more units are at risk without DPI. For orders over 5,000 units, consider multiple DPI visits at 20%, 50%, and 80% completion.

New Products or Designs

First production runs carry higher risk. New products may have: design issues not apparent in samples, production process problems, worker unfamiliarity with product, or material sourcing challenges. DPI for first production runs identifies these issues early. After successful first production, subsequent runs may not need DPI if the supplier has proven capability. But always maintain PSI as the final check.

Complex Manufacturing Processes

Products with complex manufacturing benefit from DPI. Complexity indicators: multiple production stages, many components or materials, precision requirements, specialized processes (coating, assembly, testing), or long production time. Complex products have more opportunities for things to go wrong. DPI verifies each stage is proceeding correctly. Example: electronics assembly has PCB fabrication, component placement, soldering, testing, and assembly—DPI can check each stage.

Critical Quality Requirements

Products where quality is critical warrant DPI. Critical situations: safety-related products, regulated products (children’s, medical, food), high-value products, products for demanding customers, or brand reputation sensitivity. For these products, the cost of quality failure is high. DPI provides additional assurance beyond PSI. The extra inspection cost is insurance against costly failures.

New or Unproven Suppliers

When working with new suppliers, DPI provides valuable information about their production capability. What DPI reveals: production organization and cleanliness, worker skill and training, quality control processes, communication and responsiveness, and actual production vs. claimed capability. This information helps evaluate whether to continue with the supplier. After multiple successful orders, DPI may become less necessary.

What DPI Checks

Production Status Verification

First, DPI confirms production is on track. Checks: actual quantity produced vs. schedule, production rate (units per day), remaining time to completion, any production issues or delays, and material availability for remaining production. This information helps predict whether order will be completed on time. If production is behind schedule, you can address it before it becomes a crisis.

In-Process Quality Check

DPI evaluates quality of partially-completed production. Process: randomly select samples from completed portion, inspect using same criteria as PSI, classify defects by type and severity, and compare to AQL standards. Unlike PSI which inspects finished packed goods, DPI inspects work-in-progress. This reveals whether production process is creating quality products or if adjustments are needed.

Process Verification

DPI verifies factory is following agreed processes. Check: production line setup matches requirements, workers are trained and following procedures, equipment is properly maintained and calibrated, materials being used match specifications, and quality checks are being performed at each stage. Process problems often lead to product problems. Identifying process issues early prevents systematic defects.

Material and Component Check

For products with multiple components, DPI verifies correct materials are being used. Check: incoming materials match specifications, components are from approved suppliers, materials are being stored properly, and no unauthorized substitutions. Material issues discovered at PSI may be too late to fix—wrong materials may require complete rework. DPI catches material issues when they can still be addressed.

DPI Process and Methodology

Scheduling DPI

Plan DPI timing based on production schedule. Typical approach: request production schedule from supplier, identify when 20-30% will be complete, schedule inspection 2-3 days before that point, confirm with supplier that production will be at expected stage. For multiple DPI visits: schedule first at 20-30%, second at 50-60%, third at 80%. Adjust timing based on production speed and complexity.

Sample Selection for DPI

DPI sampling differs from PSI because not all production is complete. Approach: randomly select from completed units only, ensure samples represent different production times/shifts, sample size based on completed quantity (not total order), and apply AQL standards to completed portion. Example: 2,000 unit order, 500 completed (25%). Sample size based on 500 units = 50 samples at Level II. Inspect these 50 units from the 500 completed.

DPI Inspection Checklist

DPI checklist should include: Production status: quantity completed, production rate, timeline. Quality check: appearance, dimensions, functionality of completed units. Process check: production setup, worker procedures, equipment condition. Materials: verify correct materials being used. Packaging preparation: packaging materials ready, labels prepared. Issues identified: any problems noted, corrective actions needed. The checklist ensures comprehensive evaluation.

Handling DPI Findings

When DPI Finds Issues

If DPI reveals quality problems, take immediate action. Steps: document issues with photos and details, discuss with factory management, identify root cause, agree on corrective action, verify correction is implemented, and consider re-inspection if issues are significant. Common corrective actions: retrain workers, adjust equipment, change materials, modify process, or rework affected units. The goal is to fix the issue and prevent recurrence.

When DPI Finds No Issues

Good DPI results don’t guarantee good PSI results, but they’re encouraging. Actions: continue monitoring production, maintain planned PSI, update supplier performance tracking, and proceed with confidence. Even with good DPI, maintain PSI as final check. DPI verifies process; PSI verifies final product. Both are valuable for comprehensive quality control.

Communication with Factory

Effective DPI requires good factory communication. Best practices: explain DPI purpose (not to find fault but to ensure success), provide advance notice of inspection schedule, ensure factory contact is available during inspection, share findings constructively, and work together on solutions. Position DPI as collaborative quality improvement, not adversarial fault-finding. Factories that understand DPI benefits will cooperate fully.

DPI Cost and ROI

DPI Pricing (2026)

DPI costs are similar to PSI: $150-250 per man-day for standard products. Cost factors: location (travel time to factory), product complexity, sample size required, and whether combined with other inspections. Cost-saving approach: combine DPI with PSI if timing allows—same inspector can do both, reducing travel costs. For multiple DPI visits, negotiate package pricing with inspection company.

ROI Calculation

Scenario	Without DPI	With DPI	Savings
Issue found at 30%	100% batch affected	30% affected, corrected	70% of batch saved
Rework cost (2000 units)	$4,000-8,000	$1,200-2,400	$2,800-5,600
Schedule delay	2-4 weeks	3-7 days	1-3 weeks saved
Inspection cost	$250 (PSI only)	$500 (DPI + PSI)	$250 additional
Net benefit	–	–	$2,550-5,350

Common DPI Mistakes

Implementing Effective DPI

Building DPI into Your Process

Make DPI standard practice for appropriate orders. Decision criteria: orders over 1,000 units, first production runs, complex products, new suppliers, or critical quality requirements. Include DPI in your quality control budget and timeline. Build DPI into supplier agreements: “Orders over 1,000 units will include during-production inspection at 30% completion.” Standardizing DPI ensures it happens consistently.

Working with Inspection Companies

Choose inspection company with: coverage in your manufacturing regions, experience with your product type, good communication and reporting, and competitive pricing. Provide clear instructions: what to check, AQL levels, special requirements. Review reports promptly and act on findings. Build relationship for consistent service quality. Many inspection companies offer package pricing for multiple inspections.

Continuous Improvement

Use DPI data for ongoing improvement. Track: issues found by type and frequency, supplier response and correction effectiveness, correlation between DPI and PSI results, and improvement trends over time. Use data to: identify suppliers needing more oversight, refine inspection checklists, adjust AQL levels if needed, and improve supplier communication. DPI data is valuable for supplier management.

Conclusion

During production inspection catches quality issues when they can still be fixed—before they affect the entire batch. This guide covered the essential elements: DPI definition as mid-production quality check at 20-30% completion, situations requiring DPI including large orders, new products, and complex manufacturing, what DPI checks including production status, quality, process, and materials, DPI process including scheduling, sampling, and inspection methodology, handling findings and working with factories on corrections, and cost-benefit analysis showing DPI ROI. The key principles: use DPI for orders where early detection has high value (large, complex, critical), schedule at 20-30% completion for maximum benefit, combine DPI with PSI for comprehensive quality control, communicate constructively with factories, and use DPI findings for continuous improvement. DPI is not needed for every order—but for orders where it’s appropriate, the value far exceeds the cost. A $250 DPI can save $2,000-10,000 in rework costs and prevent schedule delays. Make DPI part of your quality control toolkit and apply it strategically to protect your China sourcing investment.

Need During Production Inspection in China?
Top China Sourcing provides DPI services at all major manufacturing regions. Our inspectors verify production progress, quality, and processes, helping you catch issues early. Contact us today to discuss your inspection needs.

Last updated: April 30, 2026 | DPI Guide by TCS Editorial Team

Sources

• ISO 2859-1 Sampling Procedures for Inspection
• Quality Control Handbook by J.M. Juran
• TCS Inspection Database 2026
• China Manufacturing Quality Standards
• Third-Party Inspection Industry Reports 2026