Manufacturing Quality Glossary

The 5 Whys is a simple way to dig past the symptom of a problem by asking "why did that happen?" and then asking it again of each answer.

5S is a method for organizing a work area so that it is clean, orderly and easy to keep that way.

8D is a team method for solving a problem in eight ordered steps, often called disciplines.

APQP is a structured way to plan a new or changed product so it can be built right from the first production run.

AQL is the worst average defect rate that a sampling plan is designed to accept most of the time.

Calibration is comparing a measuring instrument with a reference of known, better accuracy to find out how far off the instrument reads, and adjusting it if needed.

CAPA is the process a quality system uses to remove the causes of problems.

A concession is a decision to accept or release product that has already been made and does not meet a requirement, because the people with authority judge it fit for use.

A control plan is a table that says how each important product and process characteristic is kept under control during production.

A controlled copy is a copy of a document that the document control system knows about and will keep current.

Cpk is a number that tells you how well a stable process fits inside its tolerance, taking into account both how much it varies and whether it is centered.

A deviation is written permission, given before the work is done, to depart from a requirement for a limited quantity or a limited time.

A DFMEA is a risk review of a product design before it is released.

Document control is the set of rules a company uses to manage the documents people work from, such as procedures, work instructions, drawings and forms.

An engineering change notice, or ECN, is the record that announces an approved change to a product or its documents and tells everyone affected what to do about it.

First article inspection is a full, documented check of one of the first parts made by a new production process, to prove the process can meet every requirement on the drawing and purchase order.

A gauge R&R study measures how much of the variation you see comes from the measurement system rather than the parts.

GD&T, short for geometric dimensioning and tolerancing, is a symbolic language on engineering drawings that controls the form, orientation and location of features, not just their size.

A job aid is a short reference that a person uses while doing a task, so they do not have to remember every detail.

Kaizen is a Japanese word meaning change for the better.

A layered process audit, or LPA, is a short, frequent check of a process done by people from several levels of the organization, the layers.

MSA is a set of studies that check whether a measurement system can be trusted before its numbers are used for decisions.

An NCR is the record raised when a part, material or process does not meet its requirement.

OEE is a single percentage that shows how much of a machine's planned production time actually produced good parts at full speed.

A PFMEA is a team review of a manufacturing or assembly process, step by step, asking how each step could go wrong, what that failure would do to the part or the customer, what could cause it, and what currently prevents or detects it.

Poka-yoke is a Japanese term for mistake-proofing: designing a part, fixture or process so that an error either cannot happen or is caught at once.

PPAP is the package of evidence a supplier sends a customer to show that a production process makes parts that meet every requirement, at the planned rate, with the real tooling and people.

Ppk measures how a process actually performed against its tolerance over a period of time.

Revision control is how a company identifies and tracks each version of a controlled document or drawing.

Risk-based thinking is the habit of asking, before you plan or change something, what could go wrong, how likely and how serious it is, and what you will do about it, along with what opportunities you could take.

Root cause analysis is the work of finding the underlying reason a problem happened, as opposed to the most visible symptom, so the fix stops it from coming back.

A SCAR, or supplier corrective action request, is a formal request asking a supplier to find and fix the cause of a problem with what they delivered.

An SOP, or standard operating procedure, is a controlled document that describes how a process runs from start to finish: its purpose, its scope, who is responsible for each part, the main steps, and the records it produces.

SPC is the practice of measuring a process while it runs and plotting the results on control charts, so you can tell normal variation from a real change.

Standard work is the agreed, current best way to do a job, written down so everyone does it the same way.

Takt time is the pace at which you need to finish one unit to keep up with customer demand.

A tolerance stack-up is a calculation of how the tolerances of several parts or features add together along one dimension of an assembly, such as a gap or a clearance.

Traceability is the ability to follow the history of a product through records: which material lot it came from, which machine, operator and settings made it, how it was inspected and where it was shipped.

True position is the exact, theoretically perfect location of a feature such as a hole, set on a drawing by basic dimensions from datums.

A work instruction is a controlled document that tells one person how to do one task, step by step, at the place where the work happens.