Quality assurance and improvement

You are not the plant quality manager. You still need the language of audits, the seven tools, control charts, and the improvement methods named in the BoK (Body of Knowledge). Most of this section is Understand. SPC (statistical process control) chart selection and reading is Apply.

IV.A Quality improvement concepts Understand

Defect detection vs. prevention. Cost of poor quality. TQM (total quality management) as an organization-wide quality philosophy. Customer satisfaction as the point of the system. Product vs. process: design, material, process steps, and final output are coupled. A sharp tool, a wrong feed, and a loose fixture can each make the same diameter fail. Inspectors who think only in parts miss the process.

IV.B Quality audits Understand

Stages: plan (scope, purpose, resources, schedule, checklist) → perform (opening meeting, interview, observe, sample records, forward and backward trace) → close (closing meeting, report, corrective action requests, follow-up verification). Tools: checklists, log sheets, sampling, document review. Soft skill named in the BoK: interview and listening. A CAR (corrective action request) from an audit is only useful if someone fixes the system, not just the symptom.

IV.C The seven basic tools (six named here) Apply

The classic seven are cause-and-effect, check sheet, control chart, histogram, Pareto, scatter, and flowchart / stratification. The CQI (Certified Quality Inspector) BoK lists Pareto, cause-and-effect, flowchart, check sheet, scatter, histogram here and treats control charts in IV.D.

• Pareto. Rank defects by frequency or cost. Separate the vital few from the useful many.
• Cause-and-effect (Ishikawa / fishbone). Bones are usually Man, Machine, Method, Material, Measurement, Environment.
• Flowchart. The process as it actually runs, not as the binder claims.
• Check sheet. Tally at the point of inspection.
• Scatter. Does Y move when X moves?
• Histogram. Shape of variation: normal, skewed, bimodal (often two processes mixed), truncated (inspection already screened it).

IV.D Statistical process control Apply

Every process varies. Common cause is the stable noise of the system. Special cause is something extra — a new batch, a worn tool, an untrained operator, a cold Monday. Control charts detect special-cause patterns so you do not treat noise as a signal or miss a real signal.

Patterns that are not random: a point beyond 3σ control limits, runs (several consecutive points on one side of the center), trends (steady climb or fall), hugging (too many points near center — sometimes wrong calculation or mixed data), cycles, a sudden shift.

Variables charts

Measured data. X-bar and R: subgroup averages and ranges. X-bar watches the mean, R watches short-term consistency. X-bar and s when subgroups are larger. Individuals and moving range (I-MR (individuals and moving range)) when you cannot rational-subgroup.

Attributes charts

Unit vs. defect: a part is nonconforming if it has one or more defects. A part can carry three defects and still be one nonconforming unit. That is why p/np and c/u are different families.

Capability

Do not compute Cpk (capability index that includes centering) on a process that is out of control. You would be describing a fantasy.

IV.E Problem-solving and continual improvement

PDCA (Plan-Do-Check-Act) / PDSA (Shewhart / Deming). Plan the change, Do it small, Study / Check the data, Act to adopt, adjust, or abandon. Then loop. Understand-level: know the four steps and that it is iterative.

Lean. Remove waste. Classic wastes: transport, inventory, motion, waiting, overproduction, over-processing, defects (and unused talent). Tools named: error-proofing (poka-yoke), value-stream mapping. Concepts: kaizen (continuous small improvement), flow, pull.

5S (Sort, Set in order, Shine, Standardize, Sustain) / 6S (5S plus Safety) (Apply). Sort, Set in order, Shine, Standardize, Sustain. The sixth S is Safety. A marked shadow board and a clean surface plate are 5S you can see.

DMAIC (Define, Measure, Analyze, Improve, Control). Define, Measure, Analyze, Improve, Control. The Six Sigma project spine. Know the letters and the intent of each phase.

FMEA (failure mode and effects analysis). Structured “how can this fail, how bad, how often, how detectable,” then prioritize (often RPN (risk priority number) = severity × occurrence × detection) and act on the high ones. Understand the purpose.

8D (eight-discipline problem solving). A team problem-solving format used heavily in automotive: D0 prepare, D1 team, D2 describe, D3 containment, D4 root cause, D5 choose correction, D6 implement, D7 prevent recurrence, D8 recognize the team. Versions vary by company. Know that containment is not root cause.

5 Whys. Ask why until you hit a cause you can act on. Stop when the next why leaves the system you own. Do not stop at “operator error” if the fixture invites the error.

Fault tree. Deductive, top-down logic diagram from an undesired event through AND/OR gates to basic causes.

CAPA (new in 2025 BoK). Corrective action fixes the root of an existing nonconformity and prevents recurrence. Preventive action addresses a potential nonconformity that has not happened. Containment is the immediate protection of the customer. All three words get abused. Use them correctly.

IV.F Resources

Safety Apply

SDS (Safety Data Sheet) (Safety Data Sheet): hazards, PPE (personal protective equipment), first aid, spill, disposal. Required for hazardous chemicals. MDS (material data sheet) is a material data sheet for product properties — not the same document. PPE matches the hazard: glasses, gloves, hearing protection. Inspect it. Use it.

Reference documents Apply

ISO (quality systems), ANSI (American National Standards Institute) / ASME (drawings, GD&T), ASTM (test methods), NIST (traceability), QS / customer extras (PPAP (Production Part Approval Process), AS9100 (the aerospace quality-management standard)). The contract and the drawing beat shop habit. When documents conflict, the contract order of precedence wins.

Employees and teams Remember

Empowerment: the people who do the work can stop a bad process and suggest changes. Teams need a purpose, a charter, ground rules, and a facilitator who runs the meeting rather than owning the content. Roles: leader, facilitator, recorder, members, sponsor.

Tuckman stages: forming (polite, unclear) → storming (conflict) → norming (rules settle) → performing (work flows) → adjourning (done). Storming is normal. Killing the team during storming is the mistake.

Quality documentation Apply

• Use the current revision. Check the document-control stamp.
• Hierarchy: policy → procedure → work instruction → form / record.
• A document says what should happen. A record proves what happened.
• Fill required fields. No blanks.
• Errors: single line through, initial, date. No white-out. Do not scribble so the original disappears.
• Packages you will hear: ISO 9001 (the international quality-management-system standard) records, First Article Inspection Report (FAIR (First Article Inspection Report) / AS9102 (the aerospace first-article inspection form)), ISIR (Initial Sample Inspection Report), PPAP (control plan, dimensional results, capability).