Production Quality Control: Inspection Plans and Nonconformance

By P-Soft Expert Team October 10, 2026 10 min read

Production quality control means deciding before you make a part what will be inspected, where, with which gauge and against which acceptance limit; recording the result; and making a clear decision for every out-of-tolerance part: scrap, use as is, or rework. Without a written inspection plan and nonconformance records, quality depends on whoever happens to be inspecting.

In many workshops, quality control means one person with a caliper checking a few parts at the end of the job. That sometimes catches a bad part, but it does not tell you where the defect came from, how many other parts are affected, or how to stop it happening again. This guide is a practical framework for small and mid-sized manufacturers: from writing an inspection plan to handling nonconformance and keeping traceable records, plus the mistakes that create the most scrap.

Where Does Manufacturing Quality Control Start?

Quality is checked at three points, and each has a different purpose:

Inspection point	What is checked	Why it matters
Incoming (materials and purchased parts)	Material grade, dimensions, supplier certificate, appearance	Wrong material wastes all the work that follows
In-process (between operations)	Critical dimensions after each key operation	Defects are caught before more value is added to the part
Final (before delivery)	Full conformance to the drawing and customer requirements	The last chance before a defect reaches the customer

A common mistake is to put the whole burden on final inspection. The later a defect is found, the more work has already gone into a bad part.

What Is an Inspection Plan, and How Do You Write One?

An inspection plan is a document that sets out, for each part or process, which characteristics are inspected, at which stage, with which instrument and how often. A simple plan has these columns:

Characteristic: for example hole diameter, surface finish or hardness.
Nominal value and tolerance: the target value and the acceptable upper and lower limits, taken exactly from the drawing.
Measuring instrument: caliper, micrometer, go/no-go gauge or another suitable tool.
Stage: after which operation it is measured.
Quantity and frequency: every part, the first piece, or a sample from each batch.
Responsibility: the operator, the quality inspector, or both.

Not all characteristics carry the same weight. Mark the ones that affect the part’s function or safety as “critical” and give them stricter inspection.

Tolerances and Acceptance Limits: Where to Be Strict

A tolerance is the permitted deviation from the nominal size, usually shown on the drawing. Two practical points:

Match the instrument to the tolerance: a common rule in industry is that the measuring instrument should resolve much more finely than the tolerance band; with the wrong tool, the accept/reject verdict cannot be trusted.
Take near-limit results seriously: a part accepted at the edge of the tolerance is a sign of process drift. Recording the actual value instead of just “pass/fail” makes that trend visible.

Sampling or 100% Inspection?

Inspecting every part makes sense for low volumes, expensive parts or critical characteristics. At higher volumes, most factories use sampling: a number of parts from each batch are checked and a decision is made for the whole batch. Take the sample size and acceptance criteria from your industry’s reference standard or the customer contract, and write them into the inspection plan so every inspector works the same way. In low-volume custom work, first-article inspection before making the rest is the simplest and most effective step.

Operator Self-Inspection: Quality Is Not Just the QC Department’s Job

In small shops, a quality inspector cannot stand next to every machine. The practical approach is to hand some measurements to the operators and let the inspector focus on the more sensitive points:

First piece: after setting up the machine, the operator measures the first part, and production does not continue until it is approved.
Periodic checks: during the run, defined characteristics are measured and recorded at set intervals.
Stop on drift: the operator is authorized to stop the machine and call the supervisor if results approach the tolerance limit.

For self-inspection to work, the right gauge has to be at the machine, the acceptance criterion has to be written in plain language, and recording a result should take only a few seconds. Otherwise the measurement gets done but not logged, and in practice no record remains. Independent inspection by the quality department still has its place, especially for final inspection and critical characteristics.

Nonconformance Management: What to Do With a Rejected Part

A nonconformance is a part or product that does not meet the drawing or customer requirements. Handling it properly takes four steps:

Identify and segregate: tag the part and pull it out of the flow so it does not move on to the next operation by accident.
Record: which defect, at which stage, on which order and how many parts.
Disposition: one of three common decisions:
- Scrap: the part cannot be used or corrected.
- Use as is: the deviation is minor and, with approval from an authorized person, the part continues on its route.
- Rework: the operation is repeated or the part is remade.
Corrective action: find the root cause: a worn tool, an ambiguous drawing, a wrong machine setting or defective material. If you fix the part but not the cause, the defect comes back.

Rework also has a cost: it takes machine time again and pushes other orders around. In our article on make-to-order production planning we explain why you should leave capacity margin for exactly these events.

Quality Traceability: Which Records Should You Keep?

When a customer complains about a part, you need to find out quickly which order it belonged to, which material it was made from, who made it, and at which stage it was made and inspected. At a minimum, that requires:

Every inspection result with the actual value, date and inspector’s name
The production report for each stage and its operator
The receipt for incoming material and its supplier
Every nonconformance, the decision taken and who approved it

A record that can be edited later is worth little in a customer dispute or an audit, so keep it somewhere that logs changes.

What Does Quality Control Software Make Easier?

Paper inspection records work until the day you need to find one part’s history among hundreds of sheets. A quality system that is connected to production keeps the inspection result next to the production report and turns nonconformance decisions into a formal approval flow.

In Data, the factory ERP from Barsavosh, recording inspections alongside production stage reports is available from the Start plan, and for every nonconforming item one of three decisions is recorded: scrap, continue, or rework. In the Elite plan, the quality manager can switch on automatic acceptance of in-tolerance results for chosen processes, so inspectors spend their time only on out-of-limit cases. Warehouse records in Data are tamper-proof, and users’ digital signatures are recorded on documents from the Pro plan. Data runs on the factory’s own server and its interface is in Persian. To see where quality fits alongside the other departments, read our page on factory management software.

Common Quality Control Mistakes in Workshops

Recording “pass” instead of the number: gradual process drift stays invisible until a part fails.
Inspecting only at the end: the defect is found after several expensive operations.
Verbal decisions on defective parts: nobody knows who authorized “use as is”.
Ignoring calibration: an instrument that is itself off will reject good parts and accept bad ones.
Fixing the part without fixing the cause: the same defect repeats on the next order.

Checklist: Set Up Quality Control in One Month

List the critical characteristics of your most frequent parts.
Write an inspection plan for each, with tolerance, instrument and stage.
Create a nonconformance form with three disposition options and an approver.
List your measuring instruments and check their calibration status.
Each month, group nonconformances by cause and act on the most frequent one.

Frequently Asked Questions

What is the difference between inspection and quality control?

Inspection is measuring and comparing with requirements; quality control includes inspection, deciding what to do with defective parts and acting to stop the defect recurring.

How should we disposition a nonconformance?

With one of three decisions: scrap, use as is with an authorized approval, or rework; and record the reason and the approver.

Should every part be inspected?

For critical characteristics and low volumes, usually yes; at higher volumes, sampling according to a standard or the customer contract is common.

How does automatic inspection approval work in Data?

In the Elite plan, results within tolerance are approved automatically for the processes where the quality manager has switched it on.

Which Data plan includes quality inspection?

All three plans, Start, Pro and Elite, let you record inspection results and production stage reports.

To see inspections and nonconformances recorded on a sample order, explore Data manufacturing ERP and request a demo.