Die Casting Supplier Audit Checklist

Selecting a die casting supplier is a high-stakes decision. A single vendor can determine whether your parts meet dimensional tolerances, pass functional tests, and arrive on schedule. A structured supplier audit checklist helps you verify capability evaluation, quality checks, and compliance before committing to long-term production. This guide provides a copyable numbered list grouped by theme. Each item includes a short explanation and red flags to watch for during the on-site or remote review.

Facility and Infrastructure Assessment

Begin the supplier audit by evaluating the physical and digital infrastructure of the facility. Die casting is a precision process that relies on stable environmental conditions and well-maintained equipment.

1. Inspect die casting machines and auxiliary equipment.
   Verify the make, model, and age of the machines. Ask for maintenance logs and recent repair records. Look for evidence of regular preventive maintenance, such as lubrication records and component replacement schedules.
   Red flag: Machines showing visible wear, leaks, or missing safety guards. Inconsistent maintenance records or a lack of documentation for critical components.

2. Review the melt shop and die handling area.
   The melt shop controls metal temperature and purity. Check for proper filtration, degassing, and temperature monitoring. Die handling areas should be organized to prevent cross-contamination and damage to dies.
   Red flag: Melt temperatures outside the specified range for the alloy. Lack of temperature logging or uncontrolled die storage areas.

3. Evaluate the layout and workflow.
   A logical workflow from melting to finishing reduces handling time and defect risk. Observe how parts move through the facility. Check for segregation of materials by alloy and product.
   Red flag: Parts moving backward in the process, mixed alloys, or congested workspaces that increase handling errors.

4. Check environmental controls.
   Humidity and temperature can affect finishing processes and die life. Review HVAC systems and any dehumidification equipment.
   Red flag: No climate control in finishing areas. High humidity levels that promote corrosion or affect coating adhesion.

Capability Evaluation and Process Control

Capability evaluation determines whether the supplier can consistently produce parts within your specifications. This section focuses on the statistical and process controls that prove this capability.

5. Request process capability reports (Cpk/Ppk).
   Ask for Cpk or Ppk values for critical dimensions. Cpk measures the ability of the process to produce conforming parts. Values below 1.33 for critical features are often a concern.
   Red flag: Cpk values consistently below 1.33 for critical dimensions. Lack of capability studies for new or complex parts.

6. Verify the use of statistical process control (SPC).
   SPC involves monitoring process variables in real time to detect trends before defects occur. Ask how often critical parameters are measured and how out-of-control signals are handled.
   Red flag: No SPC charts or data collection for critical parameters. Failure to investigate or document out-of-control conditions.

7. Review die design and maintenance protocols.
   The die is the core of the casting process. Ask about die inspection frequency, repair procedures, and die life tracking.
   Red flag: No die inspection logs. Unplanned die repairs without customer approval. Lack of die life tracking or replacement criteria.

8. Assess the quality management system.
   Review the supplier’s quality manual and how it aligns with recognized standards. Look for documented procedures for nonconforming material, corrective action, and internal audits.
   Red flag: No formal quality manual. Informal or undocumented corrective action processes. History of unresolved customer complaints.

Material and Certification Verification

Material integrity is fundamental to die casting performance. The supplier must be able to trace materials back to their source and verify their chemical composition.

9. Check material traceability and certification.
   Request mill test reports or certificates of conformance for aluminum alloys. Verify that lot numbers match the production records.
   Red flag: Missing mill certificates. Mismatched lot numbers or inability to trace material to the melting process.

10. Review alloy qualification and testing.
    Ask how the supplier qualifies new alloys or verifies existing ones. Look for chemical analysis records and mechanical property tests.
    Red flag: Lack of chemical analysis for each melt. No mechanical testing or reliance on assumed properties.

11. Evaluate scrap management.
    Scrap can introduce contamination if not properly managed. Ask how scrap is sorted, stored, and re-melted.
    Red flag: Mixed scrap streams. No segregation of different alloys. Lack of documentation for scrap re-melting.

Quality Checks and Inspection

Quality checks are the final line of defense. This section focuses on inspection methods, testing, and acceptance criteria.

12. Review inspection methods and equipment.
    Ask about the types of inspection used, such as CMMs, optical comparators, or dimensional gauges. Verify calibration status and frequency.
    Red flag: Unverified or uncalibrated inspection equipment. Lack of documented calibration schedules.

13. Check for non-destructive testing (NDT).
    NDT, such as X-ray or dye penetrant, can detect internal defects. Ask when NDT is performed and what acceptance criteria are used.
    Red flag: No NDT for critical parts. Lack of documented acceptance criteria or inconsistent testing.

14. Review the final inspection and packaging process.
    Final inspection should verify that all parts meet specifications before shipment. Check for proper packaging to prevent damage during transit.
    Red flag: No final inspection records. Inadequate packaging that risks part damage.

Compliance and Documentation

Compliance ensures that the supplier meets regulatory and customer requirements. This section focuses on standards, certifications, and documentation.

15. Verify compliance with relevant standards.
    Ask for evidence of compliance with industry standards for die casting, quality management, and environmental regulations.
    Red flag: Lack of certifications for key standards. Inability to provide compliance documentation.

16. Review customer-specific requirements.
    Ask how the supplier manages customer-specific requirements, such as PPAP, special inspection requests, or material restrictions.
    Red flag: No documented process for managing customer requirements. Lack of communication on special requirements.

17. Check for internal and external audit history.
    Ask about recent internal and external audits. Review findings and corrective actions taken.
    Red flag: No audit history. Unresolved findings from recent audits.

Risk and Financial Assessment

Finally, assess the supplier’s financial and operational risk. A stable supplier is more likely to maintain quality and meet deadlines.

18. Review financial stability.
    Ask for financial statements or credit information. Look for indicators of financial health and long-term viability.
    Red flag: Declining revenue, high debt, or lack of financial transparency.

19. Evaluate business continuity planning.
    Ask about backup plans for equipment failure, supply chain disruptions, or other risks.
    Red flag: No business continuity plan. Lack of backup suppliers or equipment.

Summary Table: Key Audit Areas

Audit Area	Key Questions	Red Flags
Facility	Machine age, maintenance, layout	Visible wear, no maintenance logs
Capability	Cpk values, SPC use, die management	Low Cpk, no SPC, no die logs
Material	Traceability, certification, scrap	Missing certificates, mixed scrap
Quality	Inspection methods, NDT, final check	Uncalibrated equipment, no NDT
Compliance	Standards, customer requirements, audits	No certifications, unresolved audits
Risk	Financials, continuity planning	Financial instability, no backup plan

Final Steps

A supplier audit is not a one-time event. Build a relationship with the supplier based on ongoing communication and regular reviews. Use the checklist to structure initial audits and periodic reviews. Document findings and share them with your internal team. This approach ensures that your supplier audit process is consistent, defensible, and focused on long-term quality and performance.