Core Structural Topology & Shop Floor Modeling

The structure of the In-House Manufacturing domain is built around three integrated models: the physical production topology, the engineering BOM hierarchy, and the cost accumulation model. Together they define how production is planned, executed, measured, and capitalized.

---

1. Production Topology: Factory → Line → Work Center → Machine

The physical production topology models the organizational and spatial hierarchy of manufacturing resources. Each level carries capacity, calendar, cost rate, and ownership attributes that govern scheduling and costing.

Factory / Plant
└── Production Line / Cell
    └── Work Center
        ├── Machine A
        ├── Machine B
        └── Tooling / Fixtures

Level	Purpose	Key Attributes
Factory / Plant	The highest physical manufacturing unit; owns legal entity, location, and shift calendars.	Location code, operating calendar, currency, cost center.
Production Line / Cell	A logical grouping of work centers organized around a product family or flow pattern.	Line code, throughput target, product family, supervisor.
Work Center	A capacity-managed resource where one or more routing operations are performed.	Work center code, capacity calendar, labor crew, overhead rate, OEE target.
Machine	A specific piece of equipment that consumes time and may require tooling.	Machine code, asset tag, availability calendar, hourly run cost, maintenance status.
Tooling / Fixture	Auxiliary equipment required for specific operations; may be shared or dedicated.	Tool code, life quantity, sharpening/maintenance cycle, setup association.

Capacity Model

Capacity is expressed as available production time per calendar period, reduced by planned downtime, holidays, and maintenance reservations:

$$ \text{Effective Capacity} = \text{Gross Calendar Hours} - \text{Planned Downtime} - \text{Maintenance Reservations} - \text{Holiday Hours} $$

Load is accumulated from confirmed manufacturing orders and their routing operations:

$$ \text{Operation Load} = \text{Setup Time} + (\text{Run Time per Unit} \times \text{Order Quantity}) $$

A work center is considered overloaded when cumulative load exceeds effective capacity within a scheduling window.

Work Center Cost Rates

Each work center carries standard cost rates used for overhead absorption:

Rate Type	Definition	Use
Labor Rate	Cost per labor hour for operators assigned to the work center.	Direct labor cost absorption.
Machine Rate	Cost per machine hour for equipment utilization.	Machine overhead absorption.
Overhead Rate	Indirect cost per hour (supervision, utilities, depreciation).	Manufacturing overhead absorption.

---

2. BOM Structure Hierarchy

The Bill of Materials defines the engineering structure of a product as a hierarchical tree. Each node represents an item, and each edge represents a quantity relationship.

Finished Product (FG)
└── Sub-Assembly A
│   ├── Intermediate Component X
│   │   └── Raw Material 1
│   └── Raw Material 2
└── Sub-Assembly B (Phantom)
    ├── Raw Material 3
    └── Raw Material 4

BOM Level	Description	Inventory Treatment
Level 0	Finished Good or top-level parent item.	Held as finished goods inventory upon completion.
Level 1	Direct components of the finished good, including sub-assemblies and raw materials.	May be WIP, semi-finished, or raw material.
Level N	Deeper components, recursively expanded until raw materials are reached.	Typically raw materials or purchased components.
Phantom	Logical grouping only; never stocked or costed independently.	Exploded directly into lowest-level components.

BOM Engineering Attributes

Attribute	Purpose
Item Code	Unique identifier of the component or sub-assembly.
Quantity per Parent	Standard quantity required to produce one unit of the parent.
Scrap Factor	Additional percentage applied to gross up material requirements.
Issue Method	Backflushed or manual issue for this component.
Operation Reference	The routing operation at which the component is consumed.
Valid From / To	Date range controlling BOM revision applicability.
Alternate BOM	Optional alternate formulation for the same parent item.

Multi-Level Explosion

When a Manufacturing Order is created, the BOM is exploded recursively to calculate gross and net requirements:

$$ \text{Gross Requirement} = \text{Order Quantity} \times \text{Quantity per Parent} \times (1 + \text{Scrap Factor}) $$

$$ \text{Net Requirement} = \text{Gross Requirement} - \text{Available Inventory Allocated to Order} $$

Phantom BOMs are fully absorbed into their parent level and do not generate independent inventory transactions.

---

3. Routing & Operation Structure

A routing is the ordered sequence of operations required to transform inputs into outputs. Each operation links to a work center and defines time, labor, and tooling requirements.

Routing for Finished Product
├── Operation 10: Cut / Prep
│   └── Work Center: Cutting
├── Operation 20: Machine / Form
│   └── Work Center: CNC Cell
├── Operation 30: Assemble
│   └── Work Center: Assembly Line A
└── Operation 40: Inspect / Pack
    └── Work Center: QC Station

Operation Attribute	Purpose
Sequence Number	Strict ordering of operations within the routing.
Work Center	Resource where the operation is performed.
Setup Time	Fixed time to prepare the work center.
Run Time per Unit	Variable time per unit produced.
Move Time	Time allowed between completion of one operation and start of the next.
Queue Time	Time spent waiting before the operation can begin.
Labor Skill	Required operator qualification or skill code.
Tooling Required	Fixtures, dies, or cutting tools needed.
Inspection Required	Flag indicating mandatory quality inspection.
Parallel Execution Flag	Flag allowing overlap with previous or next operation.

Standard vs. Actual Times

Time Type	Source	Use
Standard Time	Engineering estimate from routing.	Planning, scheduling, and standard costing.
Actual Time	Recorded from shop-floor time tickets.	Variance analysis and actual costing.

---

4. Cost Accumulation Model

In-House Manufacturing accumulates production cost in real time as operations execute and materials are consumed. The total cost of a Manufacturing Order is the sum of direct material, direct labor, and absorbed overhead.

$$ \text{Total Production Cost} = \text{Direct Material Cost} + \text{Direct Labor Cost} + \text{Machine Overhead Cost} + \text{Absorbed Overhead} $$

Cost Components

Cost Component	Source	Capitalization Behavior
Direct Material Cost	BOM component issues at their inventory valuation (moving average, FIFO, or standard cost).	Transferred from raw material inventory asset to WIP asset.
Direct Labor Cost	Operator time tickets multiplied by labor rate.	Added to WIP asset as production progresses.
Machine Overhead Cost	Machine run hours multiplied by machine hourly rate.	Added to WIP asset as operations are completed.
Absorbed Overhead	Work center overhead rate applied to operation hours.	Added to WIP asset to capture indirect production costs.

Cost Flow Diagram

Raw Material Inventory Asset
            │
            │ GIN / Material Issue
            ▼
   Work in Progress (WIP) Asset
            │
            │ Labor Tickets + Machine Hours + Overhead
            ▼
  Finished Goods Inventory Asset
            │
            │ Sales Shipment / Consumption
            ▼
    Cost of Goods Sold (COGS)

Variance Model

Upon order closure, standard/planned costs are compared with actual costs to identify variances:

Variance Type	Formula	Business Interpretation
Material Quantity Variance	$(\text{Actual Quantity} - \text{Standard Quantity}) \times \text{Standard Price}$	Over- or under-consumption of materials.
Material Price Variance	$(\text{Actual Price} - \text{Standard Price}) \times \text{Actual Quantity}$	Cost difference from standard purchase price.
Labor Efficiency Variance	$(\text{Actual Hours} - \text{Standard Hours}) \times \text{Standard Rate}$	Operator productivity vs. routing standard.
Labor Rate Variance	$(\text{Actual Rate} - \text{Standard Rate}) \times \text{Actual Hours}$	Wage rate difference from standard.
Overhead Absorption Variance	Actual Overhead Incurred − Overhead Absorbed	Difference between absorbed and actual overhead.
Yield Variance	$(\text{Actual Output} - \text{Expected Output}) \times \text{Standard Cost per Unit}$	Output shortfall or excess vs. expected yield.

Variances are sealed at order closure and reported to Accounting / FMS for period-end analysis; they are never overwritten by subsequent corrections.