Guide
What containment action should you take in the first forty-eight hours after finding defective supplier parts?
A containment action is freezing every part that might carry the defect where it is, whether that is your line, your stores, a container on the way or the supplier's shelves, and keeping it frozen until the cause is known and verified parts are arriving. In the first two days after defective supplier parts turn up at the dock or on the line, it means four things: put every suspect part on hold, find all of the suspect population including stock in transit and at the supplier, sort it against written criteria so production can continue on verified parts, and tell the supplier exactly what you need back and by when.
By Saola Manufacturing engineering team · Published · Updated
Containment is the step most buyers get half right. The bad parts in hand go into a quarantine cage, an email goes to the supplier, and the line keeps running on whatever is left in stores, which often came from the same lot. A few days later more bad parts appear, this time from the shipment that was already on the water or from a bin that nobody thought to check. This guide is for the supplier quality engineer, buyer or production lead who has just found a problem with custom machined, cast, stamped or finished parts. It covers how to recognize that containment is needed, why defects escape, how to draw the boundary of the suspect population, a checklist for the first two days, what a quality alert and the request to the supplier should say, and what to put in the purchase order so the next containment is faster. Root cause and permanent corrective action are a separate job, covered in the 8D report guide.
On this page
When do defective supplier parts call for containment rather than a simple return?
Contain whenever the defect could exist in parts you have not looked at yet. A single damaged part in an otherwise good lot can be returned; a dimensional, material, thread or finish defect that came from the process almost always affects more parts than the ones you found.
The quality management standards treat this as a requirement, not a courtesy. General quality management systems require nonconforming outputs to be identified and controlled so they cannot be used or delivered by mistake, through segregation, containment, return or suspension of supply. The automotive standard IATF 16949:2016 makes the two most useful ideas explicit: product with unidentified or suspect status is to be classified and controlled as nonconforming (clause 8.7.1.3), and the customer is to be notified immediately if nonconforming product has already shipped (clause 8.7.1.6). Even if that standard does not apply to your business, those two ideas are the core of good containment: suspect means nonconforming until proven otherwise, and whoever is downstream needs to know.
Typical signals that you are past a one-off return: the defect is a dimension, thread, hardness or material property rather than a dent; more than one part in the sample shows it; the lot traveler or certificate shows the parts came off a process that also made other lots you hold; or the parts are already built into assemblies. In any of those cases, start containment before you know the cause. The cause tells you how to fix the process; it does not need to be known to stop bad parts from moving.
Why do defects in custom metal parts escape the supplier and reach your dock or line?
Most escapes come from a change that the supplier's inspection plan did not anticipate: a new setup, worn tooling, a different material heat or a finishing step done elsewhere. The defect is real at the supplier, but the sample or the gauge that should have caught it was not looking in the right place.
The usual causes, each of which leaves a different pattern in the suspect parts, are:
- Setup or program change. A repeat order run on a different machine, fixture or program revision, with first-piece inspection that checked the features most likely to drift and missed the one that did.
- Gradual drift. Tool wear, insert changes or thermal growth move a dimension across the limit partway through a run, so the first and last pieces measured are good and the middle is not.
- Mixed or misidentified material. Bar from two heats, or two similar grades, in one lot, which no dimensional check will catch.
- A downstream process. Anodizing, plating, heat treatment or coating changes dimensions, thread fit or appearance after the machining inspection was done, and the parts are shipped without a final check after finishing.
- Drawing interpretation. An old revision, an unclear datum or a note the supplier read differently, which affects every part in every lot until the drawing is fixed.
- Handling and transit damage. Nicked threads, dents or corrosion from packing, which tends to be scattered and can be sorted visually.
The cause matters for containment because it sets the boundary. Drift affects part of a run; mixed material can affect any part in the lot; a drawing misread affects every lot since the revision changed. Ask the supplier early which of these it is, even before a full root cause.
A quick way to tell them apart. Measure the failing feature on every bad part you hold and note where each came from (box, layer, lot, label). Readings that creep in one direction across consecutive parts point to drift; good and bad parts mixed at random in the same box point to mixed material or a sorting failure; every part off by the same amount points to a setup, program or drawing issue; damage only on the outside of a pack points to handling. A hardness or material check on one good and one bad part separates a material mix from a dimensional problem before anyone argues about it.
How do you find every suspect part and sort them without letting more bad parts through?
Draw the boundary from the last known good parts to the first parts proven good after the fix, then search every place that population can sit. Sort it with a written criterion and a gauge, not by eye alone, and record the counts.
Locations to check. Make a list and assign a name to each: receiving dock and incoming inspection, raw stores and line-side bins, work in process and built subassemblies, finished goods, spares and service stock, goods in transit from the supplier, stock still at the supplier and its finishing or heat-treat subcontractors, and anything already shipped to your own customer. Shipments in transit are the most often forgotten; ask the supplier and your forwarder for every open shipment, its lot numbers and the expected arrival, and flag those receipts in your system so they go straight to hold.
Prove the boundary. A boundary is a guess until it is tested at both ends. Pull parts from the last lot you believe is good and the first lot after the suspect range, and check the failing feature on them. If either end shows the defect, widen the boundary by one lot or one date and check again before you release anything outside it.
Sort criteria. Write the criterion as a measurable check: the feature, the limits from the drawing, the gauge (a go/no-go plug, a thread gauge, a height gauge, a hardness tester) and what to do with each result. If the defect is cosmetic, attach limit samples or photos of acceptable and rejectable parts. Use one sorting team per criterion where possible, and have a second person check a sample of the parts the first person passed; an attributes plan from ANSI/ASQ Z1.4 at a low AQL, choosing a plan whose acceptance number is zero, is one practical way to size that check. Z1.4 is written for a continuing stream of lots with switching rules, so using one of its plans for a one-off audit is a convenience for sizing, not a statistical guarantee.
Why the double check matters. One hundred percent visual inspection is not one hundred percent effective. In a Sandia National Laboratories study in which 82 inspectors visually inspected 140 precision-manufactured parts, inspectors correctly rejected 85% of defective items while also rejecting 35% of acceptable ones, and the author compared that hit rate with an industry average of about 80% (See, Human Factors, 2015). A sort that relies on eyesight alone will let some bad parts through and will scrap some good ones. Use a gauge wherever the defect can be measured, and keep sorted-good parts marked so they are not mixed back with unsorted stock.
Records. For each location log the quantity found, sorted, accepted and rejected, the lot or date codes and who sorted. Those numbers are what you will need for the non-conformance report, any cost claim and the decision on when containment can end.
What should be done in the first two days, step by step?
Hold and identify first, then define the boundary, then sort and notify, and close the first two days with a written interim response from the supplier. The table below is a working checklist; the time buckets are common industry practice rather than a requirement of any standard.
Treat each line as an owner and a done-or-not check. If a step cannot be done, write down why; a gap in containment that nobody recorded is the one that produces the second escape.
| When | Action | Done when |
|---|---|---|
| First hours | Stop use of the part number at the line; tag and move every suspect part found so far to a marked hold area | No suspect part is in an open bin or on the line |
| First hours | Place a system hold on the part number and lots so new receipts and in-transit shipments go straight to hold | Receiving and stores cannot issue the part without quality release |
| First hours | Phone and email the supplier: stop shipping, hold its stock, list open shipments and lot numbers | Supplier has acknowledged in writing |
| Day 1 | Define the suspect boundary (lots, dates, heats) and search every location, including built assemblies and finished goods | Every location has a named owner and a count |
| Day 1 | Write the sort criterion with gauge and limit samples; start sorting, with a second check on accepted parts | Sorted-good parts are marked and released to the line |
| Day 1 | Audit a sample of each sorted-good batch with a second inspector, sized from an attributes sampling plan at a tight AQL | Zero defects found in the audit sample, or the batch is re-sorted |
| Day 1 | Issue an internal quality alert to receiving, stores, production and inspection | Alert posted at each point of use and acknowledged |
| As soon as known | If suspect product has shipped to your customer, notify them immediately with lots and quantities | Customer notified; detailed follow-up planned |
| Day 2 | Receive the supplier's interim containment response: stock sorted, in-transit plan, clean-point marking, suspected cause | Clean-point date or lot agreed for the first verified shipment |
| Day 2 | Raise the NCR, decide disposition of held parts, and request root cause and corrective action | NCR number issued; corrective action due date set |
What should the quality alert and the request to the supplier say?
The quality alert tells your own people what is wrong, how to recognize it and what to do with a suspect part. The request to the supplier asks for specific actions with dates, so the reply can be checked rather than just acknowledged.
Internal quality alert, on one page. Part number, revision and description; the defect in one sentence; a photo of a bad part beside a good one with the feature circled; affected lots or date codes; how to check (gauge and limit); what to do with a suspect part (tag, move to hold, call a named person); the clean-point mark that identifies verified parts; and the date the alert starts and who can withdraw it. Post it at receiving, stores and each point of use, and get a signature from each shift lead.
Request to the supplier. Ask for, in writing:
- Immediate stop on shipment of the part number until containment is in place, and a hold on finished and in-process stock at the supplier and at any subcontractor that touched the parts.
- A list of every shipment in transit and every lot made since the last known good lot, with quantities.
- Sorting of all stock at the supplier against the same criterion you use, with counts accepted and rejected.
- A clean-point plan: how the first shipment of verified parts will be marked on the parts, the packaging and the packing list, and the lot or date from which it applies.
- Whether the supplier will sort or replace your held stock, and who covers the sorting cost.
- An early view of the suspected cause, which of the causes above it is, and when the full corrective action report will follow.
Keep the disposition decision separate from containment. Whether held parts are scrapped, reworked, returned or accepted under a deviation is decided on the NCR; see the supplier deviation request guide if use-as-is is on the table.
What should the purchase order and quality agreement say so containment is faster next time?
Write traceability, notification and containment expectations into the documents before there is a problem. A supplier that marks lots on every package and knows the response you expect can contain in hours instead of arguing about scope for days.
- Lot traceability. Lot or date code on every package label and the packing list, and material heat numbers on the certificate, so a boundary can be drawn without opening every box.
- Notification duty. The supplier must tell you promptly if it finds that suspect parts may have shipped, mirroring the idea in IATF 16949, rather than waiting for you to find them.
- Containment response. What an interim response must include (the list in the section above) and how fast you expect it, stated as your requirement.
- Clean-point marking. How the first verified shipment after any nonconformance is to be identified.
- Subcontracted steps. That finishing, heat treatment and other outside processes are declared, so a hold reaches the plant that actually holds the parts.
- Sorting and cost. Who sorts held stock at your site and on what basis costs are recovered.
- Critical features. The features that need a measured final check after finishing, marked on the drawing, so a finishing step cannot quietly move them out of tolerance.
Pair this with a sensible incoming plan; the receiving inspection guide covers when lots can be skipped and when they cannot.
Who does what when parts on a Saola order are suspect?
Aximora Global Trading, the company behind Saola Manufacturing, is the contracting party for every step, so you send one notice to one contact and we run containment across every plant involved. CNC turning and milling are done at our lead CNC plant in Vietnam; casting, stamping and surface finishing go to partner plants we manage, and each quote names the production site and country of origin.
When you report suspect parts, we place a hold on the part number at the plants that made it, check what is in transit and what is still at those plants, and come back with the lot list, a sort plan and a clean-point proposal. For turned and milled features the work is done with the machining and inspection team at the lead plant, which runs CNC turning and CNC milling and has a 2D vision measuring machine, height gauge and hardness tester on site. If the defect involves a cast, stamped or finished feature, the managed partner that did that step is brought into the hold and the sort, and the response says which steps were done at the lead CNC plant and which at a managed partner plant; see surface finishing and die casting for how those processes are arranged.
ISO 9001 certification is in progress, not held. The quality and inspection page lists the records available with each lot. If you need a particular containment response, labeling or traceability rule, put it in the RFQ and it is confirmed in the quote. To start, send the drawing and your quality requirements for a quote.
Frequently asked
What is the difference between containment, correction and corrective action?
Containment stops suspect parts from moving while the cause is unknown. Correction fixes the nonconforming parts themselves, for example by rework or replacement. Corrective action removes the root cause so the defect does not recur. In 8D terms containment is discipline D3, ahead of root cause in D4 and permanent corrective action in D5 and D6.
What is a clean point?
A clean point is the first lot, date or serial number from which parts are verified free of the defect, marked on the parts or packaging so receiving can tell new stock from suspect stock. It lets you lift the hold on new receipts without lifting it on old ones.
Who pays for sorting suspect parts?
That depends on the purchase order and quality agreement, which is why it belongs there before a problem happens. Commonly the supplier sorts or pays for sorting of nonconforming product it shipped, but agree the basis in writing at the start of containment so the sort is not delayed by the argument.
When can containment be lifted?
When the corrective action has been implemented and verified, verified parts from after the clean point have been received and checked without the defect recurring, and all held stock has a disposition. Ending containment on the strength of a promised fix, before evidence, is the most common way the same defect returns.
Should you keep running production on sorted parts?
Usually yes, if the sort criterion is measurable, the gauge is right and sorted-good parts are kept separate and marked. If the defect cannot be detected reliably, for example a material mix-up that needs a lab test, hold the parts until each lot is verified.
Sources
- IATF 16949:2016, Automotive quality management system standard (about the standard), International Automotive Task Force, 2016
- J. E. See, Visual Inspection Reliability for Precision Manufactured Parts, Human Factors 57(8), Sandia National Laboratories, 2015
- ANSI/ASQ Z1.4-2003 (R2018), Sampling Procedures and Tables for Inspection by Attributes, American Society for Quality, 2003, reaffirmed 2018
- What are the Eight Disciplines (8D)?, American Society for Quality, accessed October 2026