{"id":2178,"date":"2026-07-01T22:50:04","date_gmt":"2026-07-01T14:50:04","guid":{"rendered":"https:\/\/metalstampingparts.ltd\/?page_id=2178"},"modified":"2026-07-01T22:50:04","modified_gmt":"2026-07-01T14:50:04","slug":"metal-stamping-aql-sampling-plan-guide","status":"publish","type":"page","link":"https:\/\/metalstampingparts.ltd\/metal-stamping-aql-sampling-plan-guide\/","title":{"rendered":"Metal Stamping AQL Sampling Plan Guide"},"content":{"rendered":"

Short answer:<\/strong> An AQL sampling plan for metal stamped parts should define the lot size, defect classes, inspection level, acceptance number, critical dimensions, cosmetic rules, and escalation method before production. It is useful when full inspection is not practical, but it should not replace process controls for safety, function, or customer-critical features.<\/p>\n

Sampling plans are often discussed late, after a shipment is rejected or a buyer asks why every piece was not checked. For stamped parts, the right plan depends on risk. A hidden bracket, plated terminal, EMI shield, spring clip, and cosmetic cover should not all use the same acceptance rule.<\/p>\n

Use this guide with the quality control checklist<\/a>, incoming inspection checklist<\/a>, control plan checklist<\/a>, and surface finish inspection guide<\/a>.<\/p>\n

Define defect classes before choosing AQL<\/h2>\n\n\n\n\n\n\n\n\n
Defect class<\/th>\nStamped part example<\/th>\nTypical handling<\/th>\n<\/tr>\n<\/thead>\n
Critical<\/td>\nWrong material, mixed revision, unsafe edge, missing functional feature, or failed conductivity.<\/td>\nOften zero acceptance, containment, and buyer notification.<\/td>\n<\/tr>\n
Major<\/td>\nOut-of-tolerance hole, wrong bend height, plating below minimum, or fit failure.<\/td>\nDefined AQL or tighter sampling, with lot hold if failed.<\/td>\n<\/tr>\n
Minor<\/td>\nSmall non-functional mark, light handling trace, or acceptable burr within agreed limit.<\/td>\nHigher AQL may be acceptable if function and assembly are not affected.<\/td>\n<\/tr>\n
Cosmetic<\/td>\nVisible stain, scratch, color variation, or water mark on a defined appearance surface.<\/td>\nUse approved samples, lighting conditions, viewing distance, and defect limits.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

AQL is not a substitute for process control<\/h2>\n

AQL sampling decides whether a lot is accepted based on sampled parts. It does not prove that every part is good, and it does not prevent the process from drifting. For CTQ dimensions, use sampling together with in-process checks, first-off approval, tooling maintenance, and reaction plans.<\/p>\n

If a dimension needs trend control, connect the sampling plan to the SPC and process capability guide<\/a>. If the issue is burr, flatness, plating, or cleanliness, define the inspection method using the inspection equipment guide<\/a>.<\/p>\n

Lot size and inspection level<\/h2>\n

The same AQL number can mean different sample quantities depending on lot size and inspection level. Buyers should define whether a lot is a production batch, shipment batch, coil lot, plating batch, or customer release. This is especially important when stamped parts are plated, cleaned, or packed after stamping.<\/p>\n

For parts with lot traceability needs, align sampling with the lot traceability and serialization guide<\/a>. A rejected plating lot should not be mixed into an accepted stamping lot without clear labels and records.<\/p>\n

Escalation rules after a failed sample<\/h2>\n

Sampling plans need escalation rules. If a sampled part fails, the next step may be lot hold, re-sampling, 100 percent sorting, process audit, corrective action, or buyer approval. The rule should depend on defect class. A missing functional feature is not handled the same way as a small mark outside a non-visible zone.<\/p>\n

Escalation rules should also state who pays for sorting, whether replacement parts are needed, and how the supplier prevents the same issue in future lots. For repeated problems, use the supplier corrective action guide<\/a>.<\/p>\n

AQL sampling RFQ checklist<\/h2>\n