Manufacturing Operations & Production Planning

Material Requirements Planning (MRP) is the backbone of manufacturing planning. It answers three questions: What to produce/buy, How much, and When.

MRP inputs:

• Master Production Schedule (MPS) — the authorised production plan for finished goods, derived from demand forecasts and actual orders
• Bill of Materials (BOM) — the recipe: every parent–child relationship, quantity-per, and scrap allowance
• Inventory records — on-hand quantity, open POs, and work-in-process at every level of the BOM

MRP output: time-phased planned orders (purchase or production) for every component, offset by lead time. The logic is:

Net Requirement = Gross Requirement − On-Hand − Scheduled Receipts
Planned Order Release = Planned Receipt − Lead Time

MRP II extended MRP to include capacity requirements planning (CRP), financial simulation, and rough-cut capacity checks, integrating the shop floor with the business plan.

ERP systems (SAP S/4HANA, Oracle, Microsoft Dynamics) embed MRP II logic as a core module, connecting demand management, procurement, manufacturing, and financials in a single system of record.

An MES bridges the planning layer (ERP) and the physical shop floor (machines, operators, PLCs). While ERP says what to make and when, MES manages the how — in real time.

Core MES functions (ISA-95 / ISA-88 standard):

• Work order management — release, sequence, and dispatch production orders to work centres
• Labour and machine tracking — capture actual time against each operation, compare to standard
• Material traceability — scan barcodes or RFID to record exact materials consumed in each unit/batch (critical for recall management in pharma, food, aerospace)
• Quality management — in-process inspections, Statistical Process Control (SPC) charts, non-conformance capture, and CAPA integration
• OEE monitoring — real-time Availability, Performance, and Quality KPIs per machine/line, with downtime reason coding
• Electronic device history record (eDHR) — regulated industries (FDA 21 CFR Part 11, EU GMP Annex 11) require complete electronic batch records

Leading MES platforms:

Platform	Vendor	Specialty
SIMATIC IT	Siemens	Discrete & process, tightly integrated with Siemens automation
Opcenter	Siemens	Pharma, medical device, electronics
FactoryTalk	Rockwell Automation	Discrete manufacturing, Allen-Bradley PLCs
SAP ME / MII	SAP	SAP ERP integration, automotive
Plex	Rockwell Automation	Cloud-native MES, automotive & food
AVEVA MES	AVEVA	Process industries, oil & gas, batch
Tulip	Tulip Interfaces	No-code, operator-centric, SMB-friendly

Lean originated with the Toyota Production System (TPS) and was codified by Womack & Jones (1996) as five principles:

1. Specify Value — define value from the customer's perspective (price willing to pay)
2. Map the Value Stream — identify all steps; categorise as value-add, necessary non-value-add, or pure waste
3. Create Flow — eliminate interruptions so value flows continuously (one-piece flow, U-cells)
4. Establish Pull — let customer demand pull production; avoid over-production
5. Pursue Perfection — continuous improvement (kaizen) toward zero waste

The 8 wastes (TIM WOODS):

• Transportation — unnecessary movement of materials
• Inventory — excess raw material, WIP, or finished goods
• Motion — unnecessary operator movement
• Waiting — idle time for machine, operator, or material
• Overproduction — making more than needed, earlier than needed
• Over-processing — more steps or precision than the customer values
• Defects — rework, scrap, warranty
• Skills — unused human potential and creativity

Key lean tools: Value Stream Mapping (VSM), 5S, SMED, Poka-Yoke (error-proofing), Andon (problem-escalation signal), OEE dashboards, A3 problem-solving.