How to Qualify a New Die Casting Supplier

Prerequisites: What to Have Before You Start

Before you contact a supplier or request a quote, assemble the internal documents that define the job. Without these, the qualification process stalls because you will be asking the supplier to guess your requirements.

Start with the drawing package. Include the 2D drawing, the 3D CAD model, and any GD&T callouts. For die castings, the drawing should show the mold flow direction if you have a preference, but do not be dogmatic about it. The foundry will know the best flow path for their machines. If you provide a mold flow direction that fights their tooling design, you will create a rework cycle that costs money and delays the first article.

Next, define the material. For aluminum, specify the alloy and the heat treatment condition if any. For zinc, specify the alloy and the finishing requirements. Do not just say “6061” or “Zinc.” Say “6061-T6” or “Zinc die cast, bright zinc, no plating.” The condition changes the casting process and the downstream plating or painting. If you require a specific finish, include the finish specifications in the prerequisites.

Finally, define the volume. A supplier that is excellent at casting 50,000 parts per year may be a poor fit for a part that requires 5,000 parts per year. The economics of die casting are driven by volume. The tooling cost is spread over the parts produced. If your volume is low, the per-unit cost is high. The supplier needs to know if this is a long-term program or a prototype run. A long-term program changes the supplier’s willingness to invest in tooling, process control, and dedicated capacity.

Step 1: Verify Capability and Tooling

The first step in supplier qualification is to confirm the foundry can build the tooling and run the castings. Do not take the quote at face value. Ask for the tooling design. If the supplier provides a 3D tooling model, review it. If they do not, ask why. A supplier that will not share tooling information before the order is a red flag. They are either hiding a design flaw or they have no process control.

Check the tooling material. For high-volume aluminum parts, tooling is typically made from aluminum or steel. For zinc parts, tooling is usually steel. The material affects the life of the die. A supplier that uses the cheapest tooling material for a high-volume part may deliver a part that looks good on day one and cracks on day two. Ask about the expected die life. If the supplier cannot give you a number, they do not know their own process.

Review the molding process. Die casting is not a single process. It involves die design, die fabrication, die assembly, trial runs, and production. Ask how they manage the transition from trial to production. A good supplier will document the trial process. They will record the parameters for each trial shot. They will not just run parts until they look right. They will capture the settings and verify the process is repeatable.

Step 2: Review Quality Systems and Certifications

A supplier qualification is not complete without a quality review. Look for ISO 9001 certification. This is the baseline. It shows the foundry has a documented quality management system. It does not guarantee quality, but it shows they have a framework for managing it.

For automotive or aerospace parts, look for IATF 16949 or AS9100. These standards go deeper into process control. They require the foundry to manage special processes, control variables, and document their work. If your part is for a regulated industry, these certifications are not optional. They are a requirement.

Do not just look at the certificate. Look at the scope. If the certificate only covers the foundry’s office and not the production floor, it is not useful. The scope must include the manufacturing processes.

Ask for the PPAP, or Production Part Approval Process, for similar parts. If the supplier has produced a part with similar geometry, material, and finish, they should have a PPAP package. This package includes the control plan, the process flow diagram, the capability study, and the sample approvals. Review this package. It tells you how they control the process. If they cannot provide a PPAP for a similar part, they have not mastered their process.

Step 3: Assess Financial Health

A technically excellent supplier that is financially unstable is a dangerous supplier. You do not need to become a banker, but you need to understand the risk. A supplier that is under financial pressure may cut corners to save money. They may delay maintenance. They may hire less experienced workers. They may fail to invest in new tooling or new process controls.

Review their financial statements. Ask for their most recent audited financial statements. If they are a private company, they may not provide audited statements, but they should provide a summary. Look at the debt-to-equity ratio. Look at the cash flow. A supplier with high debt and negative cash flow is a risk.

Check their customer base. A supplier that relies on one large customer is vulnerable. If that customer leaves, the supplier may go out of business. A supplier with a diversified customer base is more stable. Ask about their top five customers. If one customer represents more than a certain percentage of their revenue, that is a risk.

Also, check their location. A supplier located in a region with high unemployment or high labor costs may have different risk factors than one in a stable industrial region. This is not a hard rule, but it is a factor to consider.

Step 4: Evaluate Capacity and Lead Time

Capacity and lead time are the two factors that determine whether your production schedule survives. A supplier that is excellent at quality but cannot meet your lead time is a bad fit.

Ask about their capacity. How many machines do they have? How many shifts do they run? What is their utilization rate? A supplier with 100% utilization is at risk. If one machine goes down, they cannot meet your orders. A supplier with 80% utilization has a buffer.

Review the lead time. Do not just accept the number. Ask how they calculate it. A lead time of 12 weeks is not a single number. It is the sum of tooling lead time, trial lead time, and production lead time. Break it down. If the tooling lead time is 6 weeks, the trial is 2 weeks, and the production is 4 weeks, the total is 12 weeks. If the supplier gives you a single number without breaking it down, ask for the breakdown.

Also, ask about their backlog. If the supplier is fully booked, your part will be in the queue. You may have to pay for priority. You may have to wait. Know the reality of their schedule before you place the order.

Step 5: Conduct a Site Visit or Audit

A site visit is the most effective way to qualify a supplier. You can see the floor. You can see the machines. You can see how the workers operate. You can see the quality control stations. You can see the storage of raw materials.

If a site visit is not possible, request a video audit. Do not accept a virtual tour. Ask the supplier to walk you through the process in real time. Ask them to show you the control plan. Ask them to show you the non-conforming parts. A supplier that does not have non-conforming parts is not telling the truth. Every process produces defects. The question is how they manage them.

During the audit, focus on the special processes. Die casting is a special process. The variables include the melt temperature, the shot pressure, the cooling time, and the die temperature. Ask how they monitor these variables. Ask how they record them. Ask what happens when a variable is out of spec. A good supplier will have a documented response plan. A bad supplier will say “we just adjust it.”

Step 6: Run the Trial and First Articles

The trial is where the qualification happens. Do not skip it. Do not accept a quote and wait for the first production run. Run the trial.

For the trial, ask for a sample of the casting. Inspect it. Check the dimensions. Check the surface finish. Check for defects. Porosity, inclusions, cold shuts, and flash are the common defects in die castings. If you see porosity, ask the supplier how they control it. Do not accept “it is acceptable” as an answer. Ask for the capability study. Ask for the control plan.

For the first article, request the PPAP package. Review it. Check the control plan. Check the capability study. Check the sample approvals. If the PPAP is incomplete, return it. Do not sign off on the first article until the PPAP is complete.

The first article is not the end of the qualification. It is the beginning of production. You need to track the first few lots. Track the defect rate. Track the on-time delivery. Track the communication. If the supplier misses a delivery, do not just take the part. Ask why. Ask for a corrective action. Ask for a preventive action.

Step 7: Onboard and Monitor Performance

Onboarding is a phased release of volume. Do not give the supplier the full order at once. Start with a small lot. Then increase the volume. This reduces the risk. If the supplier fails, you have only lost a small amount of money.

Set up a performance scorecard. Track quality, delivery, cost, and communication. Use a simple scale. 1 to 5. Review it monthly. If the score is below 4, hold a meeting. Ask for a corrective action plan. Do not wait until the score is 2 to have a conversation.

Keep the documentation. Store the audit reports, the PPAPs, the sample approvals, and the performance scorecards in a controlled folder. When a dispute happens, you need to know what was agreed. When a new buyer takes over the account, they need to know the history.

Common Mistakes in Supplier Qualification

The most common mistake is to skip the financial health check. Buyers focus on quality and price. They forget that a supplier that goes out of business in six months is a supply chain failure.

The second mistake is to accept the quote without breaking down the lead time. The quote says 12 weeks. The buyer does not ask how that is calculated. The tooling is 8 weeks. The trial is 2 weeks. The production is 4 weeks. The buyer thinks the total is 12 weeks. It is not. The tooling and trial are not parallel. They are sequential. The total is 14 weeks. The buyer is late.

The third mistake is to skip the site visit. The buyer trusts the quote. The buyer trusts the certificate. The buyer does not see the floor. The floor tells the truth. The machines are old. The workers are new. The quality control is not documented. The buyer finds out after the first production lot.

Final Verification

The final verification is the review of the onboarding plan. Before you place the first production order, review the entire qualification file. Check the capability. Check the quality system. Check the financial health. Check the capacity. Check the trial results. Check the first article. Check the onboarding plan.

If any of these items are missing, do not place the order. Return the gap. Ask for the documentation. Ask for the corrective action. Do not move forward until the file is complete.

The qualification process is not a one-time event. It is a continuous process. Re-qualify the supplier on a schedule. Review the financial health. Review the quality performance. Review the capacity. The supplier changes. The market changes. Your requirements change. The qualification must change with them.