CNC Machined Housings First Article Inspection Guide for Automotive Tier Suppliers: the 2026 production season Guide No.1618

The CNC machined housings market in South Korea rewards buyers who issue a complete drawing package, because an incomplete specification is the single biggest cause of quotation delay. It is written for Automotive Tier Suppliers and covers specification, supplier checks, pricing and the documentation that protects the order.

Quality System and Inspection Points

For critical programmes, put a dimensional report in the carton so that receiving can verify the lot without opening the packing. Agree in writing what happens when a lot fails, including who pays for sorting, rework and the return freight. Ask for the measurement equipment list and its calibration status, because a good part measured badly is still a reject. Track the reject rate by characteristic rather than only in total, so you can see whether the process is drifting.

Certifications and Compliance

Traceability claims need heat numbers or lot numbers that follow the parts through every operation. Surface treatments and coatings carry their own documentation, so keep the process certificates on file for the programme. A declaration of conformity should reference the standard and the revision, not just the supplier's name and stamp. Ask for quality system documentation such as ISO 9001, IATF 16949 or AS9100, dated and covering the site that will run your parts.

How the Part Is Actually Made

For CNC machined housings, the critical characteristic is wall thickness mapping and leak test, and it should be measured on the production run rather than on a hand-finished sample. Where a feature is difficult to machine, ask for a design-for-manufacture comment before the order rather than a deviation after it. Ask the shop to state the process capability it will hold, and to report actual measurements rather than a pass or fail. Confirm the drawing revision in writing, and make sure the shop is programming from the same revision you approved.

Where the Price Actually Comes From

Ask what the price would be at double the quantity; the answer shows you how much of the quotation is fixed cost. Setup cost is spread across the batch, so a small batch carries a disproportionate share of programming and tooling time. Most quotation gaps come from a different material grade, a different finishing route or a different inspection level, not from shop margin. Ask for a cost breakdown by operation; it turns a price argument into a process conversation.

Finding a Reliable Machine Shop

Confirm who owns the drawings, the fixtures and the part programme, especially if you may move the part to another supplier later. Ask for two customers already running CNC machined housings programmes and speak to them directly. Check how the shop handles subcontracting, because hidden outsourcing of heat treatment or finishing is a common cause of inconsistent quality. Ask the shop how many machines run CNC machined housings and whether your order shares a machine with another customer.

Industry Demand and Buying Cycles

The strongest CNC machined housings programmes share one habit: they are planned against a build schedule rather than against a purchase order date. South Korea is a demanding market for CNC machined housings because buyers there compare process capability, documentation and lead time in the same conversation. Repeat business in this category goes to the shops that hold tolerance across thousands of pieces, not the ones that win the first quotation. A single rejected lot can stop an assembly line, so CNC machined housings are bought on evidence rather than on price alone.

Five Boxes to Tick Before You Order

Release the drawing, approve the first article, book the inspection, lock the packing and prepare the paperwork. Five steps, and the programme runs smoothly.