Engineering Change Management
A complete guide to engineering change management: the ECO/ECN process, the drawing REV system, Title Block fields, PLM & Configuration Management, Deviation vs. Waiver, MRB decisions, and ITAR/EAR export control requirements.
📋 Engineering Change Process — ECO/ECN
1. Change Request (ECR)
· Submitter: engineering / manufacturing / customer
· Change description + rationale + impacts
· Part number + current Rev
2. Impact Analysis
· Affected parts (Where-Used)
· Existing inventory — what to do with it?
· Cost + timeline
3. Approval (ECO Board / CCB)
· Engineering + manufacturing + purchasing + stores
· Effectivity date
4. Implementation
· Drawing + Rev update
· BOM / requirements update
· Notification to all departments (ECN)
5. Closure and Filing
· Record in PLM/ERP
· Baseline preserved
· Submitter: engineering / manufacturing / customer
· Change description + rationale + impacts
· Part number + current Rev
2. Impact Analysis
· Affected parts (Where-Used)
· Existing inventory — what to do with it?
· Cost + timeline
3. Approval (ECO Board / CCB)
· Engineering + manufacturing + purchasing + stores
· Effectivity date
4. Implementation
· Drawing + Rev update
· BOM / requirements update
· Notification to all departments (ECN)
5. Closure and Filing
· Record in PLM/ERP
· Baseline preserved
ECR — Engineering Change Request
The entry point to the process: who is requesting, what's the problem (field failure? cost reduction? supplier issue?), proposed solution, impact estimate. The CCB approves/rejects.
ECO — Engineering Change Order
The binding instruction: what changes + new Rev, Effectivity (S/N/date), disposition of existing inventory (Use-As-Is/Rework/Scrap).
ECN — Engineering Change Notice
The official distribution to everyone affected — manufacturing, purchasing, quality, suppliers. Ensures everyone is working from the same version.
🔎 Where-Used — Change Impact Analysis
Before any ECO — the first question: where else does this part live? A change to a "simple" bolt used in 40 assemblies = 40 required impact checks. A PLM answers this with one click; manual file-based tracking is a recipe for trouble.
🔤 REV System — Revision Management
| Version | Method | Usage |
|---|---|---|
| A, B, C... | Letters A-Z | ISO/ASME — very common |
| 0, 1, 2... | Numbers | Some manufacturers |
| P1, P2... | P=Preliminary | Development stage, before approval |
| Rev - | Dash | Initial drawing, pre-REV |
| Rev A | First change | After initial Release |
Don't skip letters! I, O, Q, S, X, Z are avoided (confusion with 1, 0, 0, 5, ×, 2). MIL-STD-100 explicitly prohibits them.
📋 REV Block on a Drawing — Example
| REV | Description | Date | Approved |
|---|---|---|---|
| A | Changed GD&T on ⌀12 hole | 01.01.24 | A.L. |
| B | Material change from 6061 to 7075 | 15.03.24 | J.B. |
| C | Added 3×10mm slot | 01.06.24 | A.L. |
Redline — Red-Pen Correction
A temporary handwritten mark on a field drawing copy — until an official update. Only legal with an authorized signature + date + a follow-up ECO opened!
As-Built
The actual final condition — including approved deviations, material substitutions, and field repairs. Critical for project handover and failure investigations.
Interchangeability — FFF
Form-Fit-Function: a change that preserves FFF = same part number + new Rev. Breaking FFF = a new part number is mandatory!
📐 Drawing Title Block
| Field | Content | Importance |
|---|---|---|
| Part Number | Unique part number | Critical |
| Part Name | Part name | High |
| Revision | Rev A / B / C | Critical |
| Material | Material + standard | Critical |
| Scale | 1:2 / 1:1 / 2:1 | High |
| Projection | ⊕ First / ⊗ Third | Important |
| General Tolerance | ISO 2768-mK | Important |
| Surface Finish | ✓N7 (default) | Important |
| Drawn By | Name + date | Medium |
| Approved By | Name + date | Critical |
| Drawing Number | Drawing number | Critical |
The first field checked upon receiving a part: does the drawing Rev match the Rev on the purchase order! A part made perfectly to the wrong Rev = a rejected part.
📄 Drawing Types
| Type | Description |
|---|---|
| Detail Drawing | A single part — all dimensions and requirements |
| Assembly Drawing | An assembly — BOM, balloons, assembly relationships |
| Installation Drawing | How the assembly installs into the larger system |
| Tabulated Drawing | A family of similar parts in one table (Dash Numbers) |
💾 PLM — Product Lifecycle Management
The system that holds everything in one place: versioned CAD files, BOM, electronic ECO processes, digital signatures. The main benefit: a single source of truth — no "version sitting on someone's desk".
PDM — Product Data Management
The vault for CAD files: check-in/out (no overwrites!), automatic versioning, assembly-part relationships. SolidWorks PDM is common.
Full PLM
From idea to end-of-service: requirements, CAD, BOM, ECO, manufacturing, service. Windchill, Teamcenter, 3DEXPERIENCE.
📐 Configuration Management
Baseline — an approved configuration anchor point. Types: FBL (Functional — requirements), ABL (Allocated), PBL (Product — the full manufacturing documentation). Once fixed — every change goes only through an ECO.
Configuration Audit — compares: what's documented (Baseline) against what was actually built (As-Built). Mandatory before handing over a critical project.
Configuration Audit — compares: what's documented (Baseline) against what was actually built (As-Built). Mandatory before handing over a critical project.
Deviation — pre-approved deviation
"We know we won't meet requirement X — is that OK?" → engineering analysis → approval before production, for a defined batch/quantity.
Example: a hole diameter in raw stock deviates by 0.05mm — pre-approved because it doesn't affect assembly.
Example: a hole diameter in raw stock deviates by 0.05mm — pre-approved because it doesn't affect assembly.
Waiver — after-the-fact approval
"An anomaly came out — what do we do?" → MRB reviews → approval after the part has already been produced non-conforming.
Example: a part already manufactured with a slightly rougher surface finish than required — MRB checks if it's still functionally acceptable.
Example: a part already manufactured with a slightly rougher surface finish than required — MRB checks if it's still functionally acceptable.
⚠️ Golden Rules
• Both documents are limited in quantity/time — they do not change the official drawing!
• Full documentation is mandatory — not a "verbal decision"
• Repeated/permanent use of the same exception = a red flag — time to issue a real ECO and update the drawing
• A Deviation/Waiver living for months without a follow-up ECO = a ticking time bomb of conflicting versions
• Full documentation is mandatory — not a "verbal decision"
• Repeated/permanent use of the same exception = a red flag — time to issue a real ECO and update the drawing
• A Deviation/Waiver living for months without a follow-up ECO = a ticking time bomb of conflicting versions
🔍 MRB — Material Review Board
The forum that decides the fate of nonconforming parts — those not meeting drawing requirements. Composition: engineering + quality (+ customer, on defense/critical programs).
| Decision | Meaning | Requires |
|---|---|---|
| Use-As-Is (UAI) | Good as it is — despite the nonconformance | Documented engineering justification! |
| Rework | Additional processing to bring it within requirements | Approved process, re-inspection |
| Repair | Fix (not identical to original, but acceptable) | A specially-approved repair process |
| Scrap | Complete rejection | Documentation + destruction/marking |
⚠️ UAI (Use-As-Is) authority — for authorized personnel only! MRB Crib = a physical holding area for nonconforming parts awaiting a decision, preventing them from accidentally "rolling" into the production line.
🔒 ITAR / Export Control Requirements
▸ ITAR: International Traffic in Arms Regulations (USA)
▸ USML: US Munitions List — controlled items
▸ EAR: Export Administration Regulations (civilian + dual-use)
▸ ECCN: Export Control Classification Number
Drawing marking:
▸ Israel: defense export control — DECA (SIBAT)
▸ TP-10: export license request forms
▸ USML: US Munitions List — controlled items
▸ EAR: Export Administration Regulations (civilian + dual-use)
▸ ECCN: Export Control Classification Number
Drawing marking:
WARNING: This document contains technical data
subject to the Export Administration Regulations
(EAR). Export/transfer in violation of EAR
is prohibited. ECCN: 1C002
subject to the Export Administration Regulations
(EAR). Export/transfer in violation of EAR
is prohibited. ECCN: 1C002
▸ Israel: defense export control — DECA (SIBAT)
▸ TP-10: export license request forms
CAGE Code
A 5-character code identifying a defense supplier worldwide. Appears on drawing title blocks, CoCs, purchase orders. Israel: DSPO. USA: DLIS.
Effectivity + ITAR
An ITAR drawing is an "export" even via email to a foreign national! Access is restricted to US Persons or requires a license. Violation = fines and imprisonment.