Key points
- Release every production lot against a written inspection plan that names method, stage, frequency, record, and failure response.
- Define the lot before sampling: one melt, one heat-treatment batch, one die or cavity, or a date range.
- Match sampling to the characteristic: dimensions at agreed frequency, composition per melt, X-ray of agreed zones, and leak as agreed per part.
- Tie each result to part revision, lot or sample ID, requirement, actual result, disposition, reviewer, and releasing approval.
- Verify heat treatment per batch with batch records, hardness as a quick lot check, and the agreed test set.
- Keep qualification records separate from lot records; write the hold, review, and concession route before a dispute.
- Repeat first article after drawing revision, cavity repair, alloy or heat-treatment change, process move or a tool transferred from another supplier.
- Use the buyer's drawing and specification as the acceptance basis; records show how the lot met it.
First article approval versus production lot release
First article approval qualifies the drawing revision, tool, alloy, heat treatment and inspection method at one point in time; it is repeated after agreed changes. Lot release then checks each production lot against the inspection plan, characteristic by characteristic.
| Characteristic | At first article | On each production lot | Record the buyer receives |
|---|---|---|---|
| Dimensions | Ballooned drawing and dimensional report on qualified samples. | Critical dimensions at plan frequency, including after heat treatment and machining where specified. | Report tied to part revision, lot or sample ID, requirement, result, and disposition. |
| Composition | Material composition and identification. | Composition per melt, with alloy and condition stated. | Report tied to melt or lot, alloy, and condition. |
| Mechanical properties | Mechanical results with alloy, condition, specimen basis, and method. | Mechanicals as agreed, per heat-treatment batch or lot. | Report stating alloy, condition, specimen, method, requirement, result, and disposition. |
| Hardness after heat treatment | Hardness after heat treatment where the drawing requires it. | Quick lot check after heat treatment at agreed frequency. | Report tied to heat-treat batch and lot. |
| Internal soundness (X-ray) | Images and grades for agreed zones. | Agreed zones, sampled per lot if required. | Images or grades tied to part ID, zone, method, criteria, and disposition. |
| Leak tightness | Results with medium, pressure, method, limit, and result where required. | Drawing criterion, full or sampled as agreed, stage stated. | Report stating medium, pressure, units, threshold, stage, result, and disposition. |
| Finish | Finish checks in qualification package. | Finish checks at plan frequency and stage. | Result tied to lot and requirement. |
| Traceability | Tool, cavity, lot, date, and sample IDs. | Lot identification on every result and record. | Release record naming reviewer and releasing approval. |
Define the lot before you set sampling
Sampling only means something after buyer and supplier agree what one lot is. A lot can mean one melt, one heat-treatment batch, one die or cavity, one shift, or a date range, matching how the process can vary. A sample represents only its population, so one cavity does not represent another and one heat-treat batch does not represent a different batch.
Each result should tie to part number, drawing revision, lot or sample ID, requirement, actual result, and disposition, with reviewer and releasing approval named. The plan should state lot definition, quantity or frequency, and selection method.
Sampling by characteristic: dimensions, composition, X-ray, and leak
Set sampling for each characteristic separately. Dimensions are checked at agreed frequency and stage, including after heat treatment and machining where required. Composition is checked per melt, with alloy and condition on the report. X-ray covers agreed zones, sampled per lot if required; the porosity requirement states zone, condition, discontinuity type, method, reference standard with edition and level, sampling, evidence, and response.
Leak acceptance is separate: method, medium, pressure, leak rate, stage, 100% or sampled testing, and whether impregnation is permitted. CEX's in-house lab uses helium leak detection by sniffer and a water immersion tank, and leak testing can be 100% or sampled, agreed per part with the test stage (company-reported). The inspection and leak testing page describes the lab scope.
Verifying heat treatment on production lots
Heat treatment is verified batch by batch. For T6 parts, T6 heat-treatment verification sets out the batch record, hardness and tensile checks in more detail. For each heat-treat batch, records should show material identification, heat-treatment condition, and applicable test reports. Hardness is a quick lot check after heat treatment, not a design value; run it at agreed frequency and tie it to the batch. The published drawing note template uses one test set per heat-treat batch, and the A356 and A356-T6 casting specification explains specimen source, represented lot, and test method.
A mechanical property requirement states condition (as-cast, T5, or T6), specimen basis (separately cast bar, cast-on, or cut from a named zone with orientation), method (ASTM B557 or ISO 6892-1), sampling (per heat-treatment batch, per lot, or first article only), and failure response. When a result is below requirement, check in order: specimen location, fracture surface for porosity or oxide films, batch record completeness, chemistry against limits, test method, and machine calibration. A coupon result does not replace component testing for a loaded or safety-critical part.
What keeps later lots the same as the approved samples
Later lots stay like approved samples when changes are controlled and first article is repeated after events that move the process. Repeat first article after drawing revision, cavity repair, alloy or heat-treatment change, or process move, as agreed in advance. A tool that comes from another supplier is reviewed for condition and records and the part is qualified again through first article, and a design change is re-approved through first article as well.
Alloy grade wording can let later lots drift. If a proposed grade allows a wider element range than the drawing, a sample inside the limit does not prove future lots ordered to the wider grade will stay there. Either write the limit into the supply requirement with verification and change control, or qualify a revised requirement. The alloy substitution approval checklist sets out records to request. Approval records should name part, revision, supplier, material requirement, process, lots, and review triggers.
When a lot fails
Agree the failure route before a disputed delivery. The plan should state failure response, containment, and approval path. The acceptance agreement should state how material is held, who reviews it, whether more examination is allowed, and who signs a concession. Agree who interprets results, how uncertain results escalate, and a referee procedure before the first disputed delivery. Keep qualification records separate from lot records so approved first article is not confused with a released lot.
How CEX handles lot release (company-reported)
CEX's in-house lab includes a fully automatic CMM, video measuring system, calipers and gauges, optical emission spectrometer for melt and incoming ingot composition, tensile testing machine, hardness tester for post-heat-treatment hardness, X-ray inspection of agreed regions, helium leak detection by sniffer, and a water immersion tank for leak location (company-reported). Ingot is checked before melting and the melt verified so the pour is confirmed (company-reported).
CEX performs heat treatment including T6 in-house (company-reported). That matters for A356-T6 squeeze-cast parts, where the heat-treat batch record is part of lot release. CEX also makes die casting and squeeze casting tooling in-house, runs 25 CNC machining machines in-house, has X-ray equipment for checking internal soundness against agreed acceptance criteria, and has helium leak testing equipment (all company-reported). Overseas customers can visit the factory or book a live video audit of the inspection lab (company-reported).
Qingdao Dechengxin Metal Products Co., Ltd. is the factory and holds the certificates in its own name: IATF 16949:2016 (scope: manufacturing of aluminium alloy die-cast parts) and ISO 9001:2015 (company-reported). CEX is a combined factory and trading company, and the trading company, Qingdao Chengenxin, has the same owner. CEX has cast aluminum in Jimo District, Qingdao since 1995 and has developed its squeeze casting process in-house since 2015 (company-reported).
When you send an inquiry, attach the inspection plan, lot definition, and sampling by characteristic so the quotation can reflect the release method. The casting RFQ checklist lists the documents to include. The casting inspection plan guide covers characteristic, method, sampling and record, and PPAP and first article inspection covers the approval that lot release builds on.