Most aerospace CNC machining orders fail at receiving, not at machining. The parts arrive, the dimensions pass, and then the customer finds the material certificate does not match the batch, or the anodizing report is missing, or the first article inspection was never signed off. The certificate was the entry ticket, not the guarantee. For UAV, eVTOL, and aviation aftermarket buyers, the real question is whether the factory can deliver the parts with the documents that make them traceable and installable. This guide walks through the aerospace cnc machining checks that belong in the RFQ and the receiving dock, so the parts you approve match the parts that fly.
The Drawing: GD&T, Key Characteristics, and What the Print Demands
The drawing decides the order, and the notes on the print matter more than the geometry. The notes are the part of an aerospace cnc machining print that nobody models and everybody quotes. GD&T callouts - position, flatness, profile - tell the programmer which features are functional and which are cosmetic. Key characteristics, marked as KPC on the print, demand a higher inspection level than the rest of the part. Material grade, heat treatment, surface finish, and special process flags all live in the drawing notes, and a quote that skips them quotes the wrong part. When you compare aerospace cnc machining suppliers, send the full print with the notes, not a simplified model, and ask the factory to restate the critical callouts in the quote. A quote that lists the KPCs and the material spec understands the job; a quote that only counts the holes does not.
Material Certificates: AMS Grades and the Wrong-Aluminum Problem
Aerospace materials carry their own grades, and the certificate is the proof of the grade. Aluminum for flight hardware is specified by AMS grades, not by the generic 6061 that a commercial job accepts; titanium and nickel alloys follow the same rule. The mill certificate ties the material to a heat number, and the heat number must match the batch in your carton. The wrong-aluminum problem is real: a bar of generic 6061 cut for an aerospace part fails certification, and if the factory substituted it silently, the part is scrap with a wrong certificate. Put the material spec with the AMS or MIL grade on the RFQ, and require a mill certificate with the heat number for every batch. That single line separates aerospace cnc machining from commercial work more than any tolerance does.
Tolerances and the CMM Report: What ±0.005 Means in Practice
Aerospace parts hold tolerances tighter than the machine's brochure. Common flight hardware runs ±0.005 mm to ±0.02 mm on functional features, and the machine shop proves it with a coordinate measuring machine, or CMM, report. The report should list every critical dimension with the measured value and the tolerance, not a summary page that says "within spec." Ask how the factory decides between sampling and full inspection: critical characteristics often get 100% measurement, cosmetic ones get a sample. Require the CMM report per batch, with the temperature and date recorded, so the numbers can be traced. That report is the audit trail an aerospace cnc machining buyer keeps on file. The tolerance is the spec; the CMM report is the evidence, and both belong in the aerospace cnc machining delivery file.
First Article Inspection: AS9102 and the Golden Part
The first article inspection, or FAI, is the gate before production. AS9102 defines the standard form, and it covers dimensions, materials, processes, and functional requirements on the first part of a new setup. The approved FAI part becomes the golden part that production batches are measured against. Require an AS9102 or equivalent first article report from the factory, and review it before the production order ships. A factory that can produce the FAI without being chased has the process control you need; a factory that treats the FAI as paperwork is shipping risk in a box. The FAI is the moment aerospace cnc machining stops being a promise and becomes a record.
Special Processes: Anodizing, Heat Treatment, and NDT Outsourcing
Most CNC shops do not do everything in-house. Special process control is the part of aerospace cnc machining that does not show up in the machine shop brochure. Anodizing, heat treatment, and non-destructive testing, or NDT, are usually subcontracted, and the subcontractor is where quality control goes missing. Require the special process certificates with each delivery: the anodizing spec and thickness report, the heat treat cycle record with the batch number, the NDT method and acceptance criteria. Ask which subprocessors the factory uses and whether they hold customer or NADCAP approval, and name the approved list in the purchase order. In aerospace cnc machining, the part is only as good as its weakest subprocess, and the subprocess you do not audit is the one that fails.
Traceability and the Delivery File
The delivery file is the product. Every aerospace part ships with a file: the material certificate and heat number, the CMM report, the FAI record, the special process certificates, and the batch record tying each carton to each lot. Check the file before the parts: if the document does not match the batch number on the box, treat the parts as unapproved. Keep the file with the parts for the lifetime of the aircraft, because traceability survives the warranty period. The aerospace cnc machining supplier that ships a complete file without being asked has a quality system; the one that needs reminding does not.
The checks line up: read the drawing notes and the KPCs, verify the AMS or MIL material grade with the mill certificate, demand the CMM report per batch, gate production on the AS9102 first article, audit the special process subcontractors, and inspect the delivery file before the parts. Run every aerospace cnc machining order through those six checks and the receiving failures you hear about stay in other warehouses. Our precision CNC machining guide explains why batch consistency beats single-part accuracy, our precision machining service guide covers the questions to ask before sending a drawing, and our 5 axis CNC machining guide shows how complex aerospace geometry gets produced. Send your print, volumes, and certification requirements to our contact page, and get a quote built around the checks in this guide - the documents first, the price second.
