9.3 Nonconforming Material Control & MRB

9.3 Nonconforming Material Control & MRB

Regulatory Framework and Principles of Nonconformance Control

In manufacturing and quality inspection, the discovery of a nonconforming product—a component, raw material, or assembly that fails to satisfy drawing requirements, purchase order terms, or technical specifications—represents an immediate operational risk. If an undetected discrepant component enters aircraft assembly, medical device packaging, or automotive brake systems, the consequence can be catastrophic equipment failure and loss of human life.

To safeguard product integrity, modern quality management systems establish rigorous, non-negotiable protocols for controlling nonconforming outputs. Governed by ISO 9001:2015 (Clause 8.7) and aerospace standard AS9100D (Clause 8.7) (Nonconforming Outputs), organizations must ensure that outputs that do not conform to requirements are identified and controlled to prevent their unintended use or delivery.

From a financial and operational perspective, effective nonconformance control directly limits the Cost of Poor Quality (COPQ). Nonconformance costs fall into two categories:

• Internal Failure Costs: Scrap, rework, re-inspection, redesign engineering, and machine downtime incurred before shipment to the customer.
• External Failure Costs: Field failures, customer warranty returns, product recalls, liability litigation, and brand damage incurred after the customer receives the product.

Early containment by quality inspectors halts internal failures before they compound into devastating external failures.

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The Three-Tiered Nonconformance Workflow

When an inspector, technician, or machine operator detects a nonconformance, quality procedures mandate immediate execution of a three-tiered containment protocol: Identification, Segregation, and System Quarantine.

+-----------------------------------------------------------------------------+
|                   THREE-TIERED CONTAINMENT PROTOCOL                         |
+-----------------------------------------------------------------------------+
|  1. POSITIVE IDENTIFICATION                                                 |
|     - Immediately apply prominent, serialized physical tags.                 |
|     - Standard Tag Colors: Yellow (HOLD), Red (REJECT), Orange (SCRAP).     |
+-----------------------------------------------------------------------------+
|  2. PHYSICAL SEGREGATION                                                    |
|     - Physically remove material from production flow.                      |
|     - Transfer to locked Quarantine Area / Cage with restricted access.     |
+-----------------------------------------------------------------------------+
|  3. DIGITAL / SYSTEM QUARANTINE                                             |
|     - Apply administrative hold in ERP / MRP inventory management system.   |
|     - Digitally blocks pick-ticket generation, movement, and invoicing.     |
+-----------------------------------------------------------------------------+

1. Positive Physical Identification (Tagging)

The nonconforming material must be immediately and conspicuously marked to prevent inadvertent mixing with conforming production:

• Hold Tags (Typically Yellow): Applied when material is suspect, pending further engineering investigation, layout inspection, or laboratory testing.
• Reject / Discrepant Tags (Typically Red): Applied when material is definitively confirmed nonconforming and awaiting Material Review Board (MRB) disposition.
• Scrap Tags (Typically Red or Orange): Applied once material is condemned to scrap, prior to physical destruction.
• Tag Contents: Every tag must display the Part Number, Revision Level, Serial/Lot Numbers, Discrepant Quantity, Originating Operation, Inspector Name/Stamp, Date, and the generated NCR tracking number.

2. Physical Segregation (The Quarantine Area)

Tagging alone is insufficient; human error can result in a tagged part being picked and assembled. Therefore, nonconforming material must be physically removed from the production line and transferred to a designated Quarantine Area (also termed the MRB Cage or Hold Area).

• Physical Controls: The quarantine area must be physically separated from normal production (e.g., a fenced, locked enclosure or a clearly painted, chained floor zone).
• Restricted Access: Access to the quarantine cage must be strictly restricted to authorized quality personnel holding key or badge access. Machine operators, supervisors, and material handlers are legally barred from removing parts from the quarantine area.

3. Digital System Quarantine (ERP / MRP Locking)

In computerized manufacturing environments running Enterprise Resource Planning (ERP) or Manufacturing Execution Systems (MES) (such as SAP, Oracle, or JobBOSS), physical segregation must be matched by digital inventory quarantine:

• The quality inspector enters a transaction placing the specific lot, bin, or serial numbers on Quality Hold.
• The digital lock programmatically disables inventory movement: the ERP system will not generate warehouse pick-lists, will not allow transfer to subsequent assembly routers, and will refuse to generate shipping manifests or billing invoices for the quarantined parts.

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Nonconformance Report (NCR) Architecture

A Nonconformance Report (NCR) (also known as a Discrepancy Report [DR] or Quality Notification [QN]) is an auditable legal document that records the technical facts surrounding a quality failure. An NCR must be written with objective, unambiguous precision.

Standard Fields of a Professional NCR

1. Administrative Metadata: Unique serialized NCR number, date of discovery, originator name, department/workstation, purchase order, and customer job number.
2. Part Identification: Part Number, Part Name, Drawing Revision Level, Serial Numbers, Lot/Batch Number, Total Lot Quantity, and Discrepant Quantity.
3. Objective Description of Nonconformance: The description must clearly state three fundamental elements:
   • The Requirement: What the engineering drawing or specification mandates (e.g., "Drawing 541-1002 Rev C, Zone B-2, Feature #8 mandates: Bore $\varnothing 1.2500 +0.0005/-0.0000\text{ in}$, Surface Finish $16,\mu\text{in Ra max}$").
   • The Condition Found: Exactly what was measured (e.g., "Inspection using calibrated bore gage #BG-12 revealed bore diameter measured $1.2514\text{ in}$ across 6 parts; surface finish measured $28,\mu\text{in Ra}$").
   • The Delta / Extent of Discrepancy: The mathematical magnitude of deviation (e.g., "Bore is $0.0009\text{ in}$ oversize beyond the upper specification limit; roughness exceeds maximum by $12,\mu\text{in Ra}$").
4. Containment Verification: Details regarding adjacent lot screening, upstream/downstream inventory audits, and confirmation that the parts are tagged and locked in quarantine.
5. Root Cause Analysis (RCA): Identification of the underlying process, machine, tooling, or human factors that generated the discrepancy.
6. Disposition and Authorization: Formal MRB disposition instructions, engineering approvals, and customer waiver references.

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The Material Review Board (MRB)

The Material Review Board (MRB) is a designated cross-functional governing committee established within a manufacturing organization possessing the sole authority and responsibility to evaluate, adjudicate, and disposition nonconforming material.

Critical ASQ CQI Competency: An individual quality inspector does NOT have the legal authority to disposition nonconforming product as "Use-As-Is" or "Repair". The inspector's authority is limited to identifying, documenting (raising the NCR), and containing the product. Only the authorized MRB can determine the final fate of discrepant material.

MRB Composition and Functional Responsibilities

A standard Material Review Board is comprised of four primary voting disciplines:

The Customer's Role in MRB

When a manufacturing facility produces parts under government, defense, or aerospace contracts (e.g., FAA, Department of Defense, NASA, Boeing), internal MRB authority is strictly constrained by contract terms. The internal MRB can unilaterally disposition parts as Scrap, Rework, or Return to Vendor. However, if the proposed disposition is Repair or Use-As-Is, the organization must submit a formal Customer Concession Request, Deviation Request, or Waiver to the customer's design authority. The parts cannot be shipped until written customer concession approval is secured.

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Dissecting MRB Disposition Pathways

The MRB must select one of five standardized disposition pathways for nonconforming material:

+-----------------------------------------------------------------------------------+
|                             MRB DISPOSITION PATHWAYS                              |
+-----------------------------------------------------------------------------------+
|  1. REWORK                                                                        |
|     - Returns part to 100% DRAWING COMPLIANCE using standard processes.           |
|     - No customer waiver required; mandatory re-inspection.                       |
+-----------------------------------------------------------------------------------+
|  2. REPAIR                                                                        |
|     - Makes part structurally/functionally sound, but NOT to drawing print.       |
|     - MANDATORY Customer / Design Authority Concession/Waiver required.           |
+-----------------------------------------------------------------------------------+
|  3. USE-AS-IS (CONCESSION / WAIVER)                                               |
|     - Material accepted outside blueprint limits based on engineering analysis.   |
|     - Design Authority approval mandatory; customer approval required for specs.  |
+-----------------------------------------------------------------------------------+
|  4. SCRAP                                                                         |
|     - Unusable, un-repairable, or uneconomical to recover.                        |
|     - MANDATORY physical mutilation/destruction to prevent counterfeit re-entry.  |
+-----------------------------------------------------------------------------------+
|  5. RETURN TO VENDOR (RTV)                                                        |
|     - Discrepant material rejected back to external supplier for credit/replace. |
+-----------------------------------------------------------------------------------+

1. Rework: Returning to 100% Drawing Compliance

• Definition: An action taken on a nonconforming product to make it conform completely to the original engineering drawing requirements and specifications using approved standard manufacturing operations.
• Examples: An exterior turned shaft is machined to $\varnothing 1.005\text{ in}$ against a print requirement of $\varnothing 1.000 \pm 0.002\text{ in}$ (oversized material). The MRB dispositions the part to "Rework: Set up on engine lathe and turn down diameter to $\varnothing 1.000 \pm 0.001\text{ in}$." Another example: chasing damaged threads with a standard tap, or re-deburring an edge.
• Customer Approval: Not required. Because the finished component will satisfy 100% of the blueprint requirements upon completion of rework, no engineering waiver is necessary.
• Mandatory Requirement: Reworked features must undergo full re-inspection by the quality department, and the specific rework instructions must be documented on a supplemental rework routing traveler.

2. Repair: Functional Restoration Without Full Blueprint Compliance

• Definition: An action taken on a nonconforming product to make it acceptable for its intended use, but where the final product will NOT conform to original drawing requirements.
• Examples: A machinist accidentally drills a tapped hole $0.060\text{ in}$ oversized. The MRB proposes installing a threaded insert (Keensert or Helicoil) where no insert is authorized on the blueprint. Another example: structural weld buildup on a mis-machined casting web followed by blend grinding.
• Customer Approval: MANDATORY. Because the physical configuration departs permanently from the released engineering baseline, a repair legally alters the technical contract. It requires formal engineering stress analysis and a signed Customer Concession / Waiver.

3. Use-As-Is (Concession / Deviation)

• Definition: A disposition authorizing the acceptance and release of material that does not conform to specified drawing requirements, based on formal technical evaluation demonstrating that the discrepancy does not impair form, fit, function, structural strength, fatigue life, or reliability.
• Examples: A structural bracket has an overall non-critical exterior chamfer dimension measuring $0.080\text{ in} \times 45^\circ$ instead of $0.050 \pm 0.010\text{ in} \times 45^\circ$. Stress engineering calculates that the excess chamfer removes negligible material and does not affect mounting or load-bearing capability.
• Authorization: Requires signed technical concurrence from the Design Authority. If the affected characteristic governs a customer-controlled interface or customer specification, formal customer concession approval is mandatory.

4. Scrap and Mandatory Mutilation Protocols

• Definition: A disposition indicating that nonconforming material cannot be made acceptable through rework, repair, or use-as-is, or where the cost of recovery exceeds the economic value of the part.
• The Risk of Counterfeit Salvage: Historically, un-mutilated scrap parts thrown into disposal dumpsters have been illicitly retrieved by rogue brokers, cosmetically polished, re-marked, and fraudulently sold back into commercial aviation and defense supply chains as "new, surplus" parts. These are known in aviation as Suspected Unapproved Parts (SUP).
• Mutilation Mandate (FAA AC 21-29 / AS9100): Quality organizations must enforce strict mutilation and destruction protocols before scrapped parts leave the facility. Scrap must be permanently, physically rendered unusable by:
  • Cutting structural web sections with an abrasive torch or plasma cutter.
  • Crushing hydraulic valve bodies in a hydraulic press.
  • Sawing precision threaded fittings longitudinally in half.
  • Obliterating critical mounting lugs and drilling holes through sealing surfaces.
• Scrapped items are logged on Scrap Certificates, witnessed by quality personnel, and transferred directly to certified metal recyclers.

5. Return to Vendor (RTV)

• Definition: Discrepant material received from an external sub-tier supplier or raw material mill is rejected back to the vendor.
• Action: Purchasing issues a shipping debit memo; the quality engineering department issues a Supplier Corrective Action Request (SCAR) requiring formal root cause analysis and preventive action.

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Root Cause Analysis and CAPA Escalation

Dispositioning discrepant material via the MRB addresses only immediate containment and correction. To prevent defect recurrence and drive continuous improvement, organizations escalate nonconformances into the Corrective and Preventive Action (CAPA) system (governed by ISO 9001 Clause 10.2).

When Does an NCR Escalate to a CAPA?

Not every isolated, non-systemic NCR requires a full CAPA. Organizations define formal escalation triggers:

1. Any Critical Defect involving product safety, regulatory violation, or field escape.
2. Repetitive Discrepancies: The third recurrence of the same defect code or feature failure within a rolling 90-day window.
3. High Financial Impact: Scrap or rework costs exceeding defined corporate thresholds (e.g., > $5,000).
4. Major Customer Rejections: Rejection of production lots at the customer's receiving dock or assembly line.

Root Cause Methodologies (5 Whys & Ishikawa)

Effective CAPA requires finding the fundamental root cause, not merely treating symptoms:

• The 5 Whys: An iterative interrogative technique that explores cause-and-effect relationships. By repeatedly asking "Why?" (typically five times), investigators peel away superficial human errors to reveal underlying systemic procedural failures.
• Ishikawa (Fishbone) Diagram: Categorizes potential root causes into the classic 6Ms of manufacturing: Machine (spindle runout, worn leadscrew), Method (ambiguous work instructions, incorrect feed rate), Material (hardness variation, raw stock bow), Manpower (operator training, shift fatigue), Measurement (gage calibration drift, parallax error), and Milieu / Mother Nature (ambient temperature swing causing shop floor thermal expansion).

The 8D Problem-Solving Framework

High-reliability industries structure CAPA investigations using the Eight Disciplines (8D) methodology:

• D1 (Form Team) $\rightarrow$ D2 (Define Problem) $\rightarrow$ D3 (Implement Interim Containment) $\rightarrow$ D4 (Identify & Verify Root Cause) $\rightarrow$ D5 (Choose Permanent Corrective Actions) $\rightarrow$ D6 (Implement & Validate PCA) $\rightarrow$ D7 (Prevent Recurrence / Update Procedures & PFMEAs) $\rightarrow$ D8 (Recognize Team).

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Real Shop Inspection Scenarios & Common Exam Traps

• Real Shop Scenario — Rework vs. Repair Decision: A CNC operator machining hydraulic cylinder rods mills an exterior keyway $0.015\text{ in}$ too shallow. The lead machinist suggests welding the keyway solid and cutting a completely new keyway. Analysis: Welding and re-machining is a Repair, not rework, because welding introduces a Heat-Affected Zone (HAZ) and metallurgical changes that depart permanently from drawing specifications. This would require customer engineering approval. The proper, simpler disposition is Rework: mount the rod back on the milling machine and mill the keyway $0.015\text{ in}$ deeper to bring it into 100% blueprint compliance without customer approval!
• Exam Trap: Rework vs. Repair on the ASQ CQI Exam: This is one of the single most heavily tested distinctions in the entire ASQ CQI examination. Remember:
  • Rework: Re-establishes 100% compliance with original engineering drawings. Does NOT require customer concession.
  • Repair: Restores serviceable function, but leaves the part out of compliance with original drawings. ALWAYS requires design authority / customer concession.
• Exam Trap: Authority to Authorize "Use-As-Is": Exam questions frequently present a scenario where a quality inspector discovers a dimension $0.0005\text{ in}$ out of tolerance, determines it will not hurt the assembly, and stamps the router as "Accepted Use-As-Is". Analysis: This is a severe compliance violation. An inspector NEVER has the authority to disposition material as Use-As-Is. Only the Material Review Board, with signed concurrence from the Design Engineering authority, can approve a Use-As-Is disposition.
• Exam Trap: The Primary Purpose of Scrap Mutilation: When asked why scrapped aerospace or safety-critical components must be crushed, cut, or mutilated, do not select answers regarding scrap metal resale value or recycling efficiency. The primary legal reason is to permanently prevent scrapped parts from being illegally salvaged, re-marked, and reintroduced into the supply chain as counterfeit or Suspected Unapproved Parts (SUP).