A pallet of robot cable assemblies arrives at your dock. The line needs them tomorrow. Do you release them on the strength of the packing slip, tear every one open, or something in between? That decision is incoming inspection — IQC — and getting it right is the difference between catching a bad lot at the dock and finding it after it is installed on a moving robot.
Incoming inspection is the buyer's gate: a defined, repeatable check on each lot as it arrives, before it reaches production. Done well it is fast, evidence-based, and scaled to risk. Done badly it is either a rubber stamp that lets escapes through, or a 100% re-inspection that duplicates the supplier's own testing and slows every delivery.
This guide is for OEM buyers, incoming-quality teams, and supplier-quality engineers receiving first-article-inspected assemblies from a qualified supplier, with wire harness testing evidence and a path for quality recovery and RMA when a lot fails — for industrial robot arms and collaborative robots. The goal is an IQC plan that catches real defects without re-inspecting everything or trusting a shipment on faith.
TL;DR
- IQC is the receiving gate on each lot — not the first article (first sample) and not supplier qualification (vetting before you order).
- Start with the documents: a Certificate of Conformance, the electrical test report, and lot traceability. Missing paperwork is grounds to hold.
- Sample against an agreed AQL (e.g. ANSI/ASQ Z1.4); reserve 100% for new suppliers, first lots, or safety-critical circuits.
- Check workmanship to IPC/WHMA-A-620 at the agreed class, plus dimensions and electrical continuity.
- Disposition failures formally (hold, NCR, RMA/deviation) and feed the root cause upstream; reduce inspection only as the supplier's data earns it.
Where IQC fits in your quality system
Incoming inspection is one gate among several, and confusing it with the others leads to either duplicated effort or missed coverage. Keep the roles distinct:
- Supplier qualification happens once, before you order — it vets whether the supplier can build your assembly. See the supplier qualification audit checklist.
- First article inspection (FAI) approves the first build against the drawing before production runs. See the first-article and sample-deviation plan.
- The control plan and PPAP are the supplier's evidence that their process stays in control lot after lot — see the control plan and PPAP guide.
- IQC is your recurring check on each lot that arrives. It is the last gate before your line, and it exists because even a qualified supplier with an approved first article can ship a bad lot from a worn crimp die, a substituted contact, or a mislabeled reel.
IQC is not a substitute for the upstream gates — it is the safety net that assumes they can still fail occasionally. The stronger the upstream controls, the lighter your IQC can safely be.
What to inspect on an incoming robot-cable lot
Work from paperwork inward, stopping early if a gate fails.
1. Documents first
Before anyone opens a bag, confirm the lot's paperwork:
- Certificate of Conformance (CoC) tying the shipment to your part number and revision.
- Electrical test report — 100% continuity, and hipot / insulation resistance if your spec calls for it.
- Lot and date traceability, and any deviation or waiver references that apply to this lot.
If the CoC is missing, references the wrong revision, or the test report is absent, hold the lot. Documentation mismatches are the cheapest defect to catch and the most expensive to ignore.
2. Sample the lot
Unless the assembly is safety-critical or the supplier is new, inspect a sample, not the whole lot, against an agreed plan — commonly ANSI/ASQ Z1.4 at an AQL defined in your quality agreement. Sampling only works when the AQL and the accept/reject numbers were agreed before the lot shipped, so IQC is measuring against the same bar the supplier built to.
3. Workmanship to IPC/WHMA-A-620
Inspect the sample against IPC/WHMA-A-620 at the class stated in your agreement. For a robot cable the high-value checks are:
- Crimps — correct tooling marks, no exposed strands, insulation support intact; crimp height or pull-force per the report where specified.
- Strain relief and overmold — no voids, flash, or pull-out at the transition that a moving robot will flex millions of times.
- Shielding and drain — terminated and continuous, not frayed or floating.
- Connector keying and seating — correct gender, keying, and full latch, so it cannot be mis-mated at install.
4. Dimensions and marking
Verify overall length, breakout positions, and connector orientation against the drawing, and confirm labels, part number, revision, and any serialized traceability. A cable that passes electrically but is 50 mm too short or breaks out on the wrong side still stops the line.
5. Electrical verification
For most qualified suppliers, 100% continuity is done by the supplier and evidenced on the test report; IQC confirms the report exists and spot-checks the sample. Where your spec requires it, verify continuity, insulation resistance / hipot, and contact retention on the sample — especially for shielded or high-flex robot cables.
How much to inspect: AQL, 100%, or skip-lot
Match inspection depth to risk, and let data lighten it over time.
- 100% incoming for a new supplier, the first few lots, a safety-critical circuit, or right after an escape.
- AQL sampling for a qualified supplier with a stable history — the normal steady state.
- Reduced or skip-lot once the supplier has earned it with a clean record, so effort shifts to new parts and new suppliers rather than re-checking proven ones.
The mistake to avoid in both directions: rubber-stamping every lot because "they're a good supplier," and 100%-inspecting every lot forever because one failed a year ago. IQC should move with the evidence.
When a lot fails
A failed sample is not a dead end, it is a process:
- Hold the lot — quarantine so it cannot be pulled to the line by mistake.
- Raise a nonconformance report (NCR) describing the defect against the standard and the sample result.
- Disposition: return (RMA), rework by agreement, sort, or accept under a documented deviation for that lot only.
- Drive the root cause upstream so it is fixed in the supplier's process, not just screened at your dock. A recurring incoming failure usually signals a control-plan or first-article gap that is cheaper to fix once than to keep catching every delivery.
Make IQC smooth: agree it up front
Most IQC friction is really a missing agreement. Put these in the quality agreement before the first order so receiving is fast and unambiguous:
- The acceptance standard and class (IPC/WHMA-A-620 Class 2 or 3) and any exceptions.
- The AQL and sampling plan, and which characteristics are inspected.
- The documents required with every lot — CoC, test data, traceability.
- Packaging and labeling requirements, so damage and mislabeling are prevented, not discovered.
With those agreed, incoming inspection stops being a negotiation at the dock and becomes a quick, repeatable gate. Send us your drawing, quality requirements, and volume, and we can align the first article, test evidence, and CoC so your incoming inspection is fast from the first lot — and browse more sourcing and quality guides on our blog.
Article Author
Hommer Zhao serves as the general manager and wire harness engineer for Robotics Cable Assembly. The guidance on this page is written for OEM buyers who need practical sourcing criteria for custom cable assembly and wire harness programs.
Frequently Asked Questions
What is incoming inspection (IQC) for a robot cable assembly?
IQC (Incoming Quality Control) is the check a buyer performs on each lot of robot cable assemblies when it arrives, before releasing it to production. It is the receiving gate: confirm the paperwork, sample the lot against agreed criteria, verify workmanship, dimensions, and electrical continuity, then accept, reject, or hold. It is different from a first article, which approves the first sample before mass production, and from supplier qualification, which vets the supplier before you order at all.
Do I have to inspect 100% of an incoming robot cable lot?
Usually no. For a qualified supplier with a stable history, a sampling plan such as ANSI/ASQ Z1.4 at an agreed AQL is normal, and 100% electrical continuity testing is often done by the supplier and shown on the test report rather than repeated by you. Reserve 100% incoming inspection for a new supplier, a first few lots, a safety-critical circuit, or after a recent escape — and move to reduced or skip-lot inspection only once the data earns it.
What standard defines acceptable workmanship for a robot cable assembly?
IPC/WHMA-A-620 is the widely used acceptance standard for cable and wire harness assemblies, covering crimps, solder, strain relief, overmolding, labeling, and more, with Class 1/2/3 severity. State the class and any exceptions in your quality agreement so IQC checks against the same criteria the supplier built to, rather than an undocumented expectation.
What documents should arrive with the lot?
At minimum a Certificate of Conformance (CoC) tying the shipment to your part number and revision, the electrical test report (continuity, and hipot/insulation resistance if specified), lot and date traceability, and any deviation or waiver references. Missing or mismatched paperwork is itself grounds to hold the lot — IQC starts with the documents, not the connectors.
What happens when an incoming lot fails?
Put it on hold, raise a nonconformance report, and disposition it: return (RMA), rework by agreement, sort, or accept under a documented deviation for that lot only. Feed the finding back to the supplier so the root cause is fixed in their process, not just screened at your dock. A recurring failure usually points to a control-plan or first-article gap upstream, which is cheaper to fix than to keep catching at receiving.
How do I make incoming inspection faster over time?
Reduce inspection as the supplier earns it. Qualify the supplier and approve a first article up front, define AQL and required test data in the quality agreement, and track lot results. A supplier with a clean record can move to reduced or skip-lot inspection, so your effort concentrates on new parts, new suppliers, and safety-critical circuits instead of re-checking proven ones.
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