Quality glossary: plain definitions for manufacturing quality terms

Short, plain definitions for the terms that come up in quality work: problem solving, audits, supplier quality, launch and measurement. Each one says what the term means on the floor and links to the guide that covers it in full.

Jump to: 0-9 A C D E F G I L M N O P Q R S T W

0-9

5 Why

A root cause method. You state the problem, ask why it happened, and keep asking why of each answer until you reach a cause you can change and prove. Five is a habit, not a rule.

6M

The six headings on a fishbone diagram: man (people), machine, method, material, measurement and mother nature (environment). They make the team look in places it would otherwise skip.

8D

Eight disciplines: a structured problem solving report that runs from forming a team and containing the problem to verified root cause, permanent corrective action and closing out. Customers often ask for one after a complaint.

A

A3

A one-page problem solving report, named after the paper size. It tells the story of a problem from background to follow-up on a single sheet, and suits internal improvement work.

Action Priority (AP)

The high, medium or low rating the AIAG and VDA FMEA handbook uses to decide which risks need action. It replaced ranking by RPN, and it weighs severity first rather than multiplying three numbers together.

APQP

Advanced Product Quality Planning. The structured way automotive suppliers plan a new part, from design through process validation and launch. PFMEA, Control Plan, MSA and PPAP all come out of it.

AQL

Acceptable quality level. In sampling inspection, the worst average defect level a sampling plan is set up to accept. It sets the sample size and the accept and reject numbers. It is not a target for how many defects are fine to ship.

AS9100

The quality management standard for aviation, space and defense. It builds on ISO 9001 and adds requirements such as first article inspection, configuration management and product safety.

Audit finding

A gap an auditor recorded against a stated requirement, backed by objective evidence. Major and minor findings both need correction, root cause and corrective action that holds.

C

Calibration

Checking a gage against a reference standard of known accuracy, and adjusting or retiring it if it reads wrong. Calibration proves a gage is accurate. It does not prove it is repeatable, which is what gage R&R checks.

CAR

Corrective action request. A formal request to find and remove the cause of a problem, usually raised internally or after an audit. A CAR log tracks every one to a verified close.

Clean break point

The first part, lot or shipment you can prove is good after a problem. Everything before it is suspect. Marking it lets receiving and the customer see where containment ends.

Common cause

The normal, built-in variation in a stable process. It comes from many small sources and needs a change to the process to reduce, not an adjustment after every reading.

Containment

The immediate actions that stop suspect product from reaching the customer: finding, isolating and sorting it everywhere it might be. Containment protects the customer this week. It does not fix the cause.

Control chart

A run chart with control limits calculated from the process itself. Points outside the limits, or patterns such as long runs on one side, signal a special cause worth investigating.

Control Plan

The document that lists every characteristic you control in a process: the specification, how it is measured, how often, by what method, and the reaction plan when it goes wrong. It should trace back to the PFMEA.

Correction

Fixing the specific instance that was found, such as reworking the bad part or filling in the missing record. A correction fixes what was found and nothing more.

Corrective action

An action that removes the cause of a problem so it does not happen again. It is proven by an effectiveness check, not by the date it was put in place.

Cp and Cpk

Process capability indexes. Cp compares the spread of a stable process with the tolerance. Cpk also accounts for how well the process is centered, so it is the lower and more honest of the two.

Customer-specific requirements (CSR)

Extra requirements a customer adds on top of the quality standard, such as how fast to respond to a complaint or which forms to use. They come first when they differ from your own procedure.

D

Detection

In an FMEA, how likely your current controls are to catch a failure before it leaves. In root cause work, the leg of the 5 Why that asks why you did not catch it.

Read more: How to write a PFMEA

Deviation

Written, approved permission to ship or use product that does not meet a requirement, for a set quantity or time. Also called a waiver or concession. It needs a limit and an end date.

DFMEA

Design FMEA. Looks at how a product design can fail to do its job. The process version, the PFMEA, looks at how the manufacturing steps can fail.

Read more: How to write a PFMEA

Disposition

The decision on what happens to nonconforming product: use as is, rework, repair, sort, return to supplier or scrap. Use as is normally needs an approved deviation.

E

Effectiveness check

Proof, from your own data, that a corrective action worked and kept working. Decide what proof you will accept before the fix goes in, then check on schedule before closing.

Error-proofing

Designing a process so a mistake cannot be made, or is caught the moment it is made. Also called poka-yoke. It beats inspection and training as a corrective action.

Escape

A defect that got past your controls and reached the next step, the customer or the field. Every escape is at least two failures: it was made, and it was not caught.

F

First article inspection (FAI)

A full measurement of a part from the production process against every characteristic on the drawing, before regular production. Aerospace calls it AS9102 FAI. Automotive builds similar evidence into PPAP.

Fishbone diagram

A cause and effect diagram, also called an Ishikawa diagram. The problem sits at the head and possible causes are grouped on bones, usually the 6M. It goes wide so the team does not settle on the first idea.

FMEA

Failure mode and effects analysis. A structured look at how something can fail, what happens when it does, why, and what controls are in place. The process version is the PFMEA.

Read more: How to write a PFMEA

G

Gage R&R

Gage repeatability and reproducibility. A study that measures how much of your measured variation comes from the gage and the people using it, rather than the parts.

I

IATF 16949

The quality management standard for automotive production and service parts. It is used together with ISO 9001 and adds requirements such as product approval, customer-specific requirements, problem solving and supplier development.

ISO 9001

The international standard for quality management systems. It sets out what a quality system must do, not how. IATF 16949 and AS9100 build on it.

L

Layered process audit (LPA)

Short, frequent audits of the same process done by different levels of the organization, from supervisors to plant management. They check the controls that matter most are still being followed.

M

MRB

Material review board. The group that decides the disposition of nonconforming material, usually quality, engineering and production. Some customers require their approval for use as is.

MSA

Measurement system analysis. Studies that prove a measurement system can be trusted, including bias, linearity, stability and gage R&R.

N

NCR

Nonconformance report. The record of what was found, where, how much, and the disposition. It is the starting point for a correction and, when the problem matters, a corrective action.

Nonconformance

Anything that does not meet a stated requirement: a part out of tolerance, a missing record, a process not followed. Product that is nonconforming has to be identified and kept apart.

O

Occurrence

In an FMEA, how likely a cause is to happen. In root cause work, the leg of the 5 Why that asks why the defect was made.

OEE

Overall equipment effectiveness. Availability times performance times quality, as a percentage of the time a machine could have been making good parts.

P

PFMEA

Process FMEA. Walks every step of a manufacturing process and asks how it can fail, the effect, the cause and the controls. The Control Plan should follow from it.

PPAP

Production Part Approval Process. The package of evidence an automotive supplier submits to show a part and process are ready for production. It has 18 elements, and customers choose one of five submission levels.

Ppk

Process performance index. Like Cpk, but calculated from overall variation instead of within-subgroup variation, so it shows how the process actually performed over the period studied.

PPM

Parts per million. Defects per million parts shipped or received. A common way customers score supplier quality.

Problem statement

A short, factual description of the problem: what part, what defect, where it was found, how many and since when. A good one can be checked by someone who was not there.

Process flow diagram

A map of every step a part goes through, from receiving to shipping, including inspection, storage and rework loops. The PFMEA and Control Plan follow its steps.

Read more: How to write a PFMEA

PSW

Part Submission Warrant. The summary form at the front of a PPAP package that the supplier signs to declare the part meets all requirements.

Q

Quality alert

A short notice posted at the point of use telling operators and inspectors about a problem, what to look for and what to do. It is temporary and comes down when the corrective action is in place.

Quarantine

Moving suspect or nonconforming material to a controlled area so it cannot be used or shipped by mistake while a decision is made.

R

Reaction plan

The Control Plan column that says exactly what to do when a check fails: stop, contain, who to call, what to record. "Notify supervisor" on its own is not a reaction plan.

Receiving inspection

Checking incoming material against the purchase order and specification before it is accepted into stock. Results also feed the supplier scorecard.

Red tag

A tag that marks material as nonconforming or on hold. It stays on the material until a disposition is made and recorded.

Root cause

The cause that, once removed, stops the problem from coming back. You know you have it when it explains every fact and you can switch the problem on and off with it.

RPN

Risk priority number. Severity times occurrence times detection, the older way of ranking FMEA risks. The AIAG and VDA handbook replaced it with Action Priority.

Read more: How to write a PFMEA

S

SCAR

Supplier corrective action request. A formal request that makes a supplier contain, investigate and permanently fix a problem with what they shipped you.

Severity

In an FMEA, how serious the effect of a failure is for the customer or end user. The highest ratings are kept for safety and legal effects.

Read more: How to write a PFMEA

SPC

Statistical process control. Using control charts and the data from a process to tell normal variation from real change, so you react to signals and leave a stable process alone.

Special cause

Variation from a specific, findable source, such as a worn tool, a new material lot or a setup change. A control chart flags it so you can find and remove it.

Special characteristic

A product or process characteristic that affects safety, regulatory compliance, fit or function, marked on the drawing and Control Plan for extra control.

Supplier scorecard

A regular summary of a supplier's quality, delivery and responsiveness, often including PPM and open corrective actions. It shows trends a single bad lot hides.

T

Traceability

Being able to follow a part back to its lot, material, machine, date and operator. Good traceability is what keeps a containment small.

W

Work instruction

Step by step instructions for doing a job at a station, with the checks, tools and photos the operator needs. It is where a corrective action reaches the floor.

Use these next

All guides, grouped by stage
Problem Router: pick what happened and get the first move
Free Field Books: follow one problem from start to proof