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Materials, Inventory, Purchasing & Logistics Management Fundamentals

Production Management Operations Grade 3 生産管理オペレーション (BC検定) · ビジネス・キャリア検定 生産管理オペレーション3級 · Written by Tokutei Pass based on the official study texts; not copied verbatim.

1. Five Principles of Material Management, Material Classification, BOM, and Net Requirements

The "Five Principles of Material Management (and Purchasing Management)" are to procure and supply materials of: ① the right quality, ② the right quantity, ③ at the right time (delivery date), ④ at the right price, and ⑤ from the right supplier (source).

Factory materials are classified into "Main Materials (steel sheets, resin, etc.)" forming the core of the product, "Purchased Parts (screws, motors, etc.)" bought externally and assembled as-is, "Auxiliary Materials (paint, adhesive, etc.)" accompanying the product, and "Factory Consumables (cutting oil, wiping cloths, etc.)" consumed during manufacturing.

A "Bill of Materials (BOM)," which lists the component parts and quantities required to build one unit of a product, comes in two main types: a "Structure BOM (hierarchical BOM—suited for engineering changes and process control)" that displays parent-child assembly levels step by step, and a "Summary BOM" that lists the total usage quantity of each part per product unit.

In Material Requirements Planning (MRP), multiplying planned production quantity by part usage gives "Gross Requirements"; subtracting "Available Inventory = On-Hand Inventory - Allocated Quantity (reserved for other uses) + On-Order Quantity (ordered but not yet received)" yields the "Net Requirements (actual quantity to arrange)."

Key points


  • Five Principles of Material & Purchasing Management = Right "Quality, Quantity, Time (delivery), Price, and Supplier."

  • Structure BOM = displays multi-level parent-child assembly hierarchy / Summary BOM = lists the total aggregated quantity of each part needed per unit of product.

  • Available Inventory = On-Hand Inventory - Allocated Quantity + On-Order Quantity / Net Requirements = Gross Requirements - Available Inventory.

  • Example: Producing 200 products (3 parts per product), on-hand inventory 150 units, allocated quantity 40 units, on-order quantity 90 units → Gross requirement = 200 × 3 = 600 units, Available inventory = 150 − 40 + 90 = 200 units, Net requirement = 600 − 200 = 400 units
WordMeaning
Five Principles of Material and Purchasing Management
Structure BOM and Summary BOM
Available Inventory (On-Hand - Allocated + On-Order)
Net Requirements

2. Inventory Cost Trade-Off and Calculating Economic Order Quantity (EOQ)

While inventory serves as a buffer against demand fluctuations and delivery delays to prevent stockouts, holding too much inventory causes harmful effects such as tied-up capital, interest burdens, cramped storage space, quality deterioration, and obsolescence.

Among total inventory-related costs, increasing the order quantity per order to reduce order frequency lowers "Annual Ordering Cost," but because average inventory rises, "Annual Inventory Holding (Carrying) Cost" increases—creating a "trade-off relationship."

The optimal order quantity per order at the point where "Annual Ordering Cost" exactly equals "Annual Holding Cost," minimizing the sum of both (total inventory-related cost), is called the "Economic Order Quantity (EOQ)."

The formula for Economic Order Quantity is "EOQ = √((2 × Annual Demand × Ordering Cost per Order) ÷ (Unit Price × Annual Holding Cost Rate))." The denominator "Unit Price × Annual Holding Cost Rate" represents the "Annual Holding Cost per Unit."

Key points


  • Increasing order size per order "decreases annual ordering cost" while "increasing annual holding cost" (a trade-off relationship).

  • Total cost is minimized at the point where annual ordering cost equals annual holding cost, and the order quantity at that point is the Economic Order Quantity (EOQ).

  • EOQ = √((2 × Annual Demand × Cost per Order) ÷ Annual Holding Cost per Unit).

  • Example: Annual demand 4,000 units, ordering cost 1,000 yen/order, unit price 800 yen, annual holding cost rate 25% → Annual holding cost per unit = 800 × 0.25 = 200 yen, EOQ = √((2 × 4,000 × 1,000) ÷ 200) = √40,000 = 200 units
WordMeaning
trade-off between ordering cost and holding cost
Economic Order Quantity (EOQ)
inventory holding cost rate
stockout (shortage) cost

3. Fixed-Order-Quantity System (Reorder Point, Double-Bin), Periodic Ordering, and ABC Analysis

The two major inventory replenishment methods are the "Fixed-Order-Quantity System" and the "Periodic-Order System." In the "Fixed-Order-Quantity System (Reorder Point System)," whenever inventory drops to a predetermined "Reorder Point," a "fixed quantity (such as EOQ)" is ordered each time (ordering timing is irregular; order quantity is constant).

The reorder point is calculated as "Reorder Point = Average Daily Demand × Procurement Lead Time (days) + Safety Stock." A simplified fixed-order-quantity method that places identical parts in two bins and treats the emptying of the first bin as the reorder point to trigger replenishment is called the "Double-Bin (Two-Bin) System."

Conversely, the "Periodic-Order System" calculates and orders the required quantity at "fixed ordering intervals (order cycles)," such as the 1st of every month or every Monday (ordering timing is fixed; order quantity varies each time).

The order quantity in periodic ordering is calculated as "Order Quantity = (Order Cycle + Procurement Lead Time) × Average Daily Demand + Safety Stock - Current On-Hand Inventory - On-Order Quantity."

Combining these with "ABC Analysis (Pareto priority management by annual usage value)," expensive and critical "Class A items" use tightly controlled "Periodic Ordering," moderate "Class B items" use "Fixed-Order-Quantity Ordering," and inexpensive high-volume "Class C items" use the "Double-Bin System."

3. Fixed-Order-Quantity System (Reorder Point, Double-Bin), Periodic Ordering, and ABC Analysis

Key points


  • Fixed-Order-Quantity System (suited for B/C items) = irregular order timing, fixed order size / Reorder Point = Average Daily Demand × Lead Time + Safety Stock.

  • Periodic-Order System (suited for expensive A items) = fixed order timing, variable order size / Order Quantity = (Order Cycle + Lead Time) × Average Daily Demand + Safety Stock - Available Inventory.

  • Double-Bin (Two-Bin) System = a type of fixed-order-quantity method where an order is placed when the first bin becomes empty, ideal for low-cost Class C items (screws, small parts).

  • Example: Average daily demand 40 units, lead time 5 days, safety stock 80 units → Reorder point = 40 × 5 + 80 = 280 units (given reorder point 280 units, safety stock = 280 − 40 × 5 = 80 units)

  • Example: Order cycle 20 days, lead time 5 days, average daily demand 30 units, safety stock 100 units, on-hand inventory 180 units, on-order quantity 70 units → Order quantity = (20 + 5) × 30 + 100 − 180 − 70 = 600 units
WordMeaning
Fixed-Order-Quantity System and Reorder Point
Double-Bin (Two-Bin) System
Periodic-Order System
ABC Analysis (priority inventory control)
Safety Stock

4. Receiving & Acceptance Inspection, Physical Inventory (Simultaneous / Cycle), and Valuation (FIFO / Moving Average)

When ordered materials arrive, checking their quantity and quality (receiving inspection) against the delivery slip and formally accepting conforming goods as company assets is called "Acceptance (Kenshuu)." Completion of acceptance finalizes accounts payable (the obligation to pay).

Verifying book inventory records against actual physical counts of stored stock is called "Physical Inventory Taking." It includes "Simultaneous (Wall-to-Wall) Inventory," which halts operations at period-end to count all items at once, and "Cycle Counting," which counts items or locations in rotation without stopping daily operations.

When physical inventory reveals that actual stock is less than book stock due to loss, damage, or recording errors, the shortage is called "Inventory Shrinkage (inventory loss)."

When purchase unit prices fluctuate, the two standard methods for calculating issue unit cost and ending inventory value are "First-In, First-Out (FIFO)," which assumes older stock received first is issued first in order, and the "Moving Average Method," which recalculates the average unit cost upon each new receipt by dividing total inventory value by total quantity.

Key points


  • Acceptance (Kenshuu) = inspecting the quantity and quality of delivered materials, formally accepting conforming items, and confirming payment obligation.

  • Simultaneous Inventory (counting all items at once at period-end) vs. Cycle Counting (counting systematically in rotation without halting daily operations).

  • FIFO (First-In, First-Out) = issuing stock starting from the oldest receipt's unit price / Moving Average = recalculating average unit price as (Remaining Value + New Receipt Value) ÷ Total Quantity upon each receipt.

  • Example: Beginning inventory 100 units (@100 yen = 10,000 yen), received 100 units (@140 yen = 14,000 yen), issued 120 units → FIFO issue cost = 100 × 100 + 20 × 140 = 12,800 yen (ending inventory 80 × 140 = 11,200 yen)

  • Example: Under the same conditions using the moving average method → Average unit cost = (10,000 + 14,000) ÷ (100 + 100) = 120 yen/unit, Issue cost = 120 × 120 = 14,400 yen (ending inventory 80 × 120 = 9,600 yen)
WordMeaning
acceptance inspection (Kenshuu: verifying quantity and quality)
physical inventory (simultaneous inventory and cycle counting)
inventory shrinkage (loss)
First-In, First-Out (FIFO) and Moving Average methods

5. Purchasing & Subcontract Management (Centralized Purchasing, Paid/Free Supply) and the Subcontract Act

"Centralized Purchasing," in which headquarters consolidates requirements from multiple plants to buy in bulk, strengthens price bargaining power through volume discounts and aids material standardization. Conversely, "Decentralized (Local) Purchasing," where each plant buys independently, excels in emergency responsiveness and lower transport costs.

When a parent company supplies raw materials to a subcontractor for processing, "Paid Supply (Chargeable Supply)" sells the material to the subcontractor and buys back the finished part at "Material Cost + Processing Fee" (giving the subcontractor responsibility for improving material yield), whereas "Free Supply (Non-Chargeable Supply)" retains ownership with the parent company, consigns the material free of charge, and pays only the "Processing Fee."

To ensure fair subcontracting transactions and protect subcontractors' interests, Japan enforces the "Act against Delay in Payment of Subcontract Proceeds, etc. to Subcontractors (Subcontract Act)." In manufacturing commission, applicability is determined by "Capital Size Tiers" between the Parent Enterprise and Subcontractor (over 300M yen → 300M yen or less; or over 10M–300M yen → 10M yen or less).

The Subcontract Act imposes "4 Obligations" on the parent enterprise: ① Immediate issuance of a written purchase order (Article 3 document), ② Setting the payment due date as short as possible and "within 60 days from the date the goods are received (not the date inspection is completed)," ③ Creating and retaining records for 2 years, and ④ Paying overdue interest (14.6% per annum).

Furthermore, the Act strictly prohibits "11 Prohibited Acts," including "Refusal to Receive Goods" without fault on the subcontractor's part, "Delay in Payment of Subcontract Proceeds," "Unjust Reduction of Subcontract Proceeds," "Unjust Return of Goods," "Beating Down Prices (setting prices markedly below normal market rates)," and "Forced Purchase or Usage."

Key points


  • Centralized purchasing (cost reduction via bulk buying) vs. Decentralized purchasing (fast, flexible local procurement by each plant).

  • Paid supply = selling materials to the subcontractor and buying back finished goods at material + processing cost (raises yield awareness) / Free supply = providing materials free and paying only the processing fee.

  • Subcontract Act = mandatory written purchase order issuance, and subcontract payment must be made "within 60 days from the date of receiving the goods (not the inspection pass date)."
WordMeaning
centralized purchasing and decentralized purchasing
paid material supply and free material supply
Subcontract Act (Act against Delay in Payment of Subcontract Proceeds)
obligation to pay within 60 days of receiving goods

6. Five Major Functions of Logistics, Warehouses (DC / TC), Location Control, and Picking Methods

The "Five Major Functions" of logistics (six when information is added) are: ① Transportation & Delivery, ② Storage, ③ Material Handling (loading/unloading, warehousing, picking), ④ Packaging, and ⑤ Distribution Processing (price tagging, assorting, etc.). By domain, logistics is divided into procurement, production, sales, and recovery (reverse/venous) logistics.

Logistics centers (warehouses) include "DCs (Distribution Centers: storage type)," which hold inventory and ship upon receiving orders, and "TCs (Transfer Centers: pass-through / cross-docking type)," which hold no inventory and immediately sort and transship incoming goods by destination.

Warehouse storage location control includes "Fixed Location (easy to remember, but lower space efficiency)," which assigns a permanent shelf to each item, and "Free (Random) Location (high storage space efficiency)," which uses a Warehouse Management System (WMS) to store goods flexibly in any open rack.

For outbound "Order Picking Methods," "Single Picking (Order Picking / discrete picking—suited for high variety and fast shipping)" walks the shelves to gather items for one order slip at a time, whereas "Total Picking (Batch Picking / seeding method—shortens walking distance)" gathers the combined item totals for multiple orders at once and then sorts them by destination.

6. Five Major Functions of Logistics, Warehouses (DC / TC), Location Control, and Picking Methods

Key points


  • Five Major Functions of Logistics = Transport, Storage, Material Handling, Packaging, and Distribution Processing (+ Information) / DC = inventory storage center, TC = non-stocking pass-through sorting center.

  • Fixed Location = permanent shelf assigned per item / Free Location = flexible storage in any available rack to maximize space efficiency.

  • Single Picking (discrete picking) = gathering items from shelves one order slip at a time / Total Picking (batch/seeding method) = gathering items for multiple orders in bulk and sorting afterward.
WordMeaning
Five Major Functions of logistics and reverse (venous) logistics
DC (Distribution Center: storage) and TC (Transfer Center: pass-through)
Fixed Location and Free Location
Single Picking (discrete) and Total Picking (batch / seeding)

7. Material Handling Principles, Unit Load System (T11 Pallet), and Material Handling Liveliness Index

Material handling management emphasizes principles such as keeping loads ready to move, utilizing gravity, and eliminating waiting or empty transport. Consolidating cargo onto pallets or containers into a standard unit to enable mechanized handling and transport from origin to destination without repacking is called the "Unit Load System (integrated palletization)."

The standard flat pallet specified by Japanese JIS standards for integrated transport is the "T11 Pallet (1,100 mm length × 1,100 mm width: the 'one-one pallet')," which serves as the dimensional standard for truck beds, automated warehouses, and packaging modules.

To place goods in an "easily movable state (liveliness)," the "Material Handling Liveliness Index" rates from 0 to 4 how many of the four handling actions required to move an item—"Piling (gathering), Raising (lifting), Loading, and Conveying"—have already been eliminated.

Specifically, items scattered loose on the floor have "Index 0"; items placed in a box or bag (piling eliminated) have "Index 1"; items stacked on a pallet (piling and raising eliminated) have "Index 2"; items placed on a wheeled cart (only conveying needed) have "Index 3"; and items on a moving conveyor or chute (zero effort required) have "Index 4."

7. Material Handling Principles, Unit Load System (T11 Pallet), and Material Handling Liveliness Index

Key points


  • Unit Load System (integrated palletization) = consolidating goods onto standard pallets (T11 type: 1,100 mm × 1,100 mm) for mechanized handling and transport without reloading.

  • Material Handling Liveliness Index = number of actions (0 to 4) already eliminated out of the 4 actions: "Piling, Raising, Loading, Conveying."

  • Loose on floor = 0, In a box = 1, On a pallet = 2, On a wheeled cart = 3, On a conveyor/chute = 4 (higher numbers mean easier to move).
WordMeaning
Unit Load System and integrated palletization
T11 standard pallet (1,100 mm × 1,100 mm)
Material Handling Liveliness Index (0 to 4)
eliminating empty transport

8. Material Handling Equipment Characteristics and Packaging Classification (Individual, Inner, Outer)

Among primary transport and material handling equipment in factories and warehouses, the "Forklift" is the most versatile machine, handling both horizontal pallet transport and high-rack stacking in a single unit (including counterbalance and compact reach types).

Depending on application, plants also use "AGVs (Automated Guided Vehicles)" that travel unmanned via magnetic tape or laser guidance, "Conveyors (belt, roller, overhead trolley, etc.)" that continuously transport large volumes along fixed routes, and "Cranes & Hoists" that lift and move heavy loads three-dimensionally.

Meanwhile, "Packaging," which protects the value and condition of goods, is classified by JIS standards into three levels: "Individual Packaging (Kosou), Inner Packaging (Naisou), and Outer Packaging (Gaisou)."

"Individual Packaging (Kosou)" wraps each individual retail unit to enhance consumer appeal and is classified as "Commercial (Consumer) Packaging." In contrast, "Inner Packaging (cushioning materials, moisture-proof bags)" protecting against water, shock, and humidity, and "Outer Packaging" placing goods into corrugated cartons or wooden crates marked with handling symbols (Care Marks) serve transport and storage purposes and are classified as "Industrial (Transport) Packaging."

Key points


  • Forklift = mainstay of pallet handling and transport / AGV = unmanned guided vehicle / Conveyor = continuous fixed-route transport / Crane = overhead lifting of heavy loads.

  • Individual Packaging (Kosou) = wraps the smallest product unit, emphasizing aesthetics and sales promotion → "Commercial Packaging."

  • Inner Packaging (moisture/shock protection) and Outer Packaging (protection via cartons or wooden crates) = emphasize safe transport and storage → "Industrial Packaging."
WordMeaning
Forklift and AGV (Automated Guided Vehicle)
Individual Packaging (Kosou: commercial packaging)
Inner and Outer Packaging (industrial / transport packaging)
Care Marks (handling caution symbols)

High-Frequency Exam Points and Memory Aids

Four calculation problems appear frequently: ① "Available Inventory = On-Hand Inventory - Allocated Quantity + On-Order Quantity (subtract allocations, add on-order!)," and ② "EOQ = √((2 × Annual Demand × Cost per Order) ÷ Annual Holding Cost per Unit)."

Make sure you can also solve ③ "Reorder Point = Average Daily Demand × Procurement Lead Time + Safety Stock (fixed-order-quantity)" and ④ "Issue unit cost and ending inventory valuation using FIFO and Moving Average."

For concept questions, classic exam favorites are: "Class A = Periodic Ordering, Class B = Fixed-Order-Quantity, Class C = Double-Bin," "Subcontract Act payment deadline is within 60 days from the date of receiving goods (not the inspection date)," and "Single Picking (one order at a time) vs. Total/Seeding Picking (bulk picking followed by sorting)."

Finally, memorizing the exact numbers for the "Material Handling Liveliness Index (Floor 0, Box 1, Pallet 2, Cart 3, Conveyor 4)" and "T11 Pallet = 1,100 mm × 1,100 mm" guarantees instant points.

Key points


  • Available Inventory = On-Hand - Allocated + On-Order / Reorder Point = Daily Demand × Lead Time + Safety Stock / EOQ = √(2 × Annual Demand × Order Cost ÷ Holding Cost).

  • Subcontract Act payment deadline is "within 60 days after receiving goods" / Picking: "Single (discrete) = one order at a time; Total (seeding) = bulk pick then sort."

  • Material Handling Liveliness Index: Loose 0 → Box 1 → Pallet 2 → Cart 3 → Conveyor 4 (number of steps eliminated out of Piling, Raising, Loading, Conveying).
WordMeaning
formulas for Available Inventory, Reorder Point, and EOQ
Subcontract Act (payment within 60 days of receipt)
Single Picking vs. Total (Seeding) Picking
Material Handling Liveliness Index (0 to 4)

Materials, Inventory & Logistics

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