Requesting a quote for die-cast components is easy. Comparing those quotes fairly isn’t, because suppliers differ on what they assume by default—who owns the tool, what tolerance the process carries, and what happens when a casting leaks. The eight questions below are the ones experienced buyers put in writing before an RFQ goes out. They take an hour to ask and save weeks of rework.
## 1. Which alloy — and who owns the trade-off?
The alloy decision drives cost, porosity risk, and finishing more than any other line item. A380 is the general-purpose workhorse: strong, machine-friendly, and available everywhere. A413 trades some strength for superior pressure-tightness, which matters for housings and anything that must hold fluid. Zinc alloys such as Zamak 5 fill thin walls sharply and produce as-cast finishes that often skip coating entirely, at the price of higher raw-material cost per part. A capable supplier should walk you through the alloy decision explicitly — see our [A413 vs A380 die casting alloys comparison](https://kastdiecast.com/materials/a413-vs-a380/) for how the two aluminum grades differ in practice — rather than defaulting to whatever alloy their machines were tooled for last year.
## 2. Who owns the die, and what do the amortization clauses say?
Three arrangements dominate: you own the tool outright, the supplier owns it and amortizes it into piece price, or ownership transfers after a volume threshold. Each has traps. Supplier-owned tooling can leave you captive if you want to move the program; buyer-owned tooling means you pay for maintenance and storage. Ask what a “tooling refresh” costs, how many shots the die is rated for, and whether the amortization balance is due if you cancel mid-program.
## 3. Are tolerances quoted as-cast or machined?
As-cast capability for aluminum die casting is commonly ±0.1 mm on small features, but it degrades with part size, wall thickness, and draft. The question that matters on an RFQ is not “what is your tolerance?” but “what tolerance do you commit to on the print, measured how, and at what Cpk?” A quote without inspection methodology attached is an assumption, not a commitment.
## 4. What are the leak-test and porosity acceptance criteria?
Pressure-tight parts deserve pressure-tight language. Specify the test method (pressure decay is the usual choice), the media and pressure, and the pass/fail threshold. Then ask how porosity is classified — by size, location, and volume fraction — and whether impregnation (resin sealing of micro-porosity) is available as a fallback for marginal parts. Suppliers who already run leak testing in-house will answer in sentences; those who outsource it will answer in caveats.
## 5. What happens after the casting leaves the machine?
Trimming, machining, finishing, and inspection are where schedules slip. Ask which operations are in-house, which are subcontracted, and who inspects the final dimension stack. A casting that needs three outside vendors before it reaches your dock carries three extra lead-time risks.
## 6. Is die casting even the right process for this part?
A good molder will sometimes talk you out of die casting. Permanent mold and sand casting handle certain geometries, wall thicknesses, and low volumes more economically, and gravity-fed processes avoid the porosity that high-pressure injection can introduce. The honest answer depends on part size, annual volume, and feature detail — our [die casting vs permanent mold comparison](https://kastdiecast.com/blog/die-casting-vs-permanent-mold/) covers the crossover points in detail. If a supplier cannot explain when their process loses, they are selling, not engineering.
## 7. What is realistic on volume, lead time, and capacity?
State your annual volume honestly, including the low quarter. Ask for the die’s cavity count, the expected cycle time, and how many shifts the schedule assumes. Then ask what happens when your forecast doubles mid-year: is there machine capacity, or does the program re-queue behind someone else’s? Capacity answers that arrive as hedged ranges are worth probing twice.
## 8. What does the quality system certify, and what does traceability reach?
Ask for the certificate — ISO 9001 at minimum for industrial work, IATF 16949 where automotive is involved — and then ask what the traceability actually reaches: heat lots, alloy certs, inspection data per cavity, or just a packing slip. When a field failure appears two years later, the difference between “we can pull the heat-lot record” and “we can tell you which cavity, which shift, and the leak-test value” determines how the investigation ends.
## Putting the checklist to work
None of these eight questions require engineering sophistication — they require the answers to be written down before prices are compared. Suppliers who answer them readily tell you how the program will run; suppliers who answer them slowly tell you something too. Send the checklist with your RFQ, and make response quality part of your evaluation.
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*By Kast Die Cast engineering team (kastdiecast.com) — an aluminum and zinc die casting manufacturer. This article is original and unpublished.*