Managing Inventory
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Managing Inventory. Module V. TYPES OF INVENTORY. Manufacturing Inventory. Raw Material. Work-In-Process. Maintenance Repair Operating Supplies. Distribution Inventory. Finished Goods. Saleable Spares. Echelon Inventory. Total Supply Chain Inventory

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Managing inventory

Managing Inventory

Module V


Managing inventory

TYPES OF INVENTORY

  • Manufacturing Inventory

  • Raw Material

  • Work-In-Process

  • Maintenance Repair Operating Supplies

  • Distribution Inventory

  • Finished Goods

  • Saleable Spares

  • Echelon Inventory

Total Supply Chain Inventory

Multi- Echelon Inventory


Managing inventory

Supplier

Echelon Lead time

Factory

Echelon

Lead time

Depot

Echelon Lead time

Suppliers

Supplier

Echelon Inventory

Receiving Stores

Holding Stores

Plant

Plant

Plant

Plant

FPS

Factory

Echelon

Inventory

Depot

Dealer

Dealer

Dealer

Dealer

MULTI-ECHELON INVENTORY

Depot

Echelon Inventory


Managing inventory

INVENTORY MANAGEMENT

  • Inventory Management Comprises

    • Inventory Planning

    • Inventory Control

  • Inventory Created By Production Also Supports it & Needs to

    be Managed Together in a Coordinated Way (Not Separately)

  • Inventory Planning Carried Out at All Levels of Management

    • Master Planning Level – End Products

    • Overall Inventory Level

      • Production Planning – Overall Company

      • Master Production Scheduling (MPS) – End Items/ Finished Goods

      • Material Requirement Planning (MRP) – Components/ Parts/ Raw Material

  • Value of Inventory Converts into Cash as Inventories Used by

    Operations Resulting in improved Cash Flow/ Return on Investment

  • Carrying Inventory Absorbs Costs Increasing Operating Costs

    & Decreasing Profits

  • Good Inventory Management Essential for Profitable Running of

    Any Organization


Managing inventory

LEVELS OF INVENTORY MANAGEMENT

  • Aggregate Inventory Management

    • Manage Inventory as Per Classification & Functions They Perform

      • Raw Material

      • Work-in-Process

      • Finished Goods

    • Financially Oriented & Concerned with Costs & Benefits of Carrying Different

      Classifications of Inventory

  • Aggregate Inventory Management Looks into

    • Flow & Kinds of Inventory Needed

    • Supply & Demand Patterns

    • Functions that Inventories Perform

    • Objectives of Inventory Management

    • Inventory Costs

  • Item-Level Inventory Management Involves Establishing Decision Rules

    for Controlling Inventory at the Item Level & Includes

    • Identifying Items Most Important for Business

    • How Individual Items Will be Controlled

    • How Much to Order at One Time

    • When To Place an Order


Managing inventory

INVENTORY CLASSIFICATION BY FLOWS

  • Major Classification of Inventory Based on Flow of Material Into/ Through

    and Out of a Manufacturing Organization

  • Raw Material – Purchased Items Received But Not Issued to Production

    & Include Component/ Parts/ Sub-assemblies

  • Work-In-Process (WIP) - Raw Materials Issued to Production Being Processed/

    Waiting for Next Stage in Processing

  • Finished Goods – End Product of the Production Process Ready for Sale Held at

    Factory/ Central Warehouse

  • Distribution Inventories – Stocked in Various Points in the Distribution System

  • Maintenance, Repair & Operational Supplies (MRO) – Items that Support the

    Production Process But Do Not Become Part of Product – Hand Tools/ Machine

    Spares/ Lubricants/ Cleaning Supplies

C

U

S

T

O

M

E

R

S

Warehouse

Supplier

Raw Materials

Purchased Parts

Sub-Assemblies

Work

In

Process

Finished

Goods

Warehouse

Supplier

Warehouse

Supplier

Inventories/ Flow of Materials


Managing inventory

FUNCTIONAL VIEW OF INVENTORY

  • Anticipation Inventory

    • In Anticipation of Future Demand Ahead of Peak Selling Season/ Sales

      Promotion/ Vacation Shutdown/ Threat of Strike

  • Fluctuation Inventory (Safety Stock)

    • To Cover Random Unpredictable Fluctuations in Supply/ Demand/ Lead Time

    • Safety Stock/ Buffer Stock/ Reserve Stock Prevents Disruption in Manufacturing/

      Deliveries To Customers Due To Stock Out Resulting from Un-Anticipated Delays

  • Lot-Size Inventory (Cycle Stock)

    • Purchased/ Manufactured Quantities Greater Than Immediate Need Create Cycle

      Stock

    • To Take Advantage Of Quantity Discounts/ Reduce Shipping/ Set Up Costs

    • When Making/ Purchasing of Items at Rate Same as These Will Be Used/ Sold

    • Cycle Stock is Portion of Inventory That Depletes Gradually as Customer Order

      Comes in and is Replenished Cyclically When Suppliers Deliver Supplies

  • Maintenance, Repair & Operating Supplies (MRO)

    • Items that Support the Production Process But Do Not Become Part of Product –

      Hand Tools/ Machine Spares/ Lubricants/ Cleaning Compounds/ Pencils/ Erasers


Managing inventory

FUNCTIONAL VIEW OF INVENTORY

  • Hedge Inventory

    • Inventory Procured To Take Benefit of Low Prices When Supply More Than

      Demand in Global Markets

    • Such Products Normally are Minerals/ Grains/ Animal Products

  • Transportation Inventory (Pipeline/ Movement Inventory)

    • Inventory in Transit

    • Created as Time Required to Move Inventory from Plant To Distribution Centre/

      Customer

    • Transit Inventory Not Dependent on Shipment Size But on Transit Time-T, in

      Days & Annual Demand-A, in Units

    • Average Annual Inventory in Transit, I=TA/ 365 in Units

    • Reduction in Annual Average Transit Inventory Possible by Reducing

      Transportation Time

Delivery of goods from a supplier is in transit for ten days. If the annual

demand is 4, 200 Units, what is the Average Annual Inventory in Transit?

Average Annual Inventory in Transit, I = TA/ 365

= (10×4200)/ 365=115.06 Units


Managing inventory

EXAMPLES

  • Delivery of goods from a supplier is in transit for twelve days. If the annual demand is 5, 500 Units, what is the Average Annual Inventory in Transit?

Average Annual Inventory in Transit, I = TA/ 365

= (12×5500)/365=180.82 Units

  • If Transit Time is eleven days and the Annual Demand for an item is

  • 10, 000 Units. What is the Average Annual Inventory in Transit?

Average Annual Inventory in Transit, I = TA/ 365

= (11×10000)/365=301.36 Units

  • A company is using a carrier to deliver goods to a major customer. Annual demand is Rs 2,000,000 and the average transit time is 10 days. Another carrier promises delivery in 7 days. What will be the reduction in transit inventory if the company accepts the offer?

Current Average Annual Inventory in Transit= TA/ 365

= (10×2000000)/365=Rs 54,794.52

If offer Accepted, Average Annual Inventory in Transit= TA/ 365

= (7×2000000)/365=14000000/365= Rs. 38,356.16

Reduction in transit inventory= 54, 794.52-38, 356.16=Rs. 16, 438.36


Managing inventory

INVENTORY MANAGEMENT OBJECTIVES

  • Maximum Customer Service

  • Increased Efficiency in Operations

  • Minimum Investment in Inventory

Effective Inventory Management Helps in Maximizing Profits

While Providing Excellent Customer Service as Desired By Customers


Managing inventory

PROVIDING CUSTOMER SERVICE

  • Making Products Available Exactly When Needed By Customer is Providing Customer Service in Terms of Inventory

  • Customer Could Be Purchaser/ Distributor/ Another Plant in the

    Organization/ Next Workstation Where Next Operation will

    Take Place

  • Stock Availability is a Tool to Measure Effectiveness of Inventory

    Management System in Organization

  • Inventory Helps to Maximize Customer Service By Protecting

    Against Uncertainty

  • Condition of Stock-Out Occurs If No Stock Available When

    Customer Requires it

  • Stock-Out Leads to Customer Dissatisfaction

  • Often Extra Inventory Held as Safety Stock to Avoid Stock-Outs


Managing inventory

IMPROVING OPERATING EFFICIENCY

  • Inventories Help Manufacturing Operations To be More Productive in

    4 Ways

  • Inventories Allow Operations with Different Rate of Production To

    Operate Separately and More Economically

    • Subsequent Operations That Have Different Production Rates & Must be

      Operated More Efficiently Will Build Up Inventories Between Them

  • Strategy of Satisfying Need for Seasonal Products with Non-uniform

    Demand Using Anticipatory Inventory Built Up Through Uniform Level

    Round the Year Production Result in Lower

    • Overtime Costs

    • Hiring/ Firing Costs

    • Training Costs

    • Sub-Contracting Costs

    • Capacity Requirement

  • Inventories Allow Longer Production Runs That Result in

    • Reduced Setup Costs Per Item - With Single Set Up More Quantities Produced

    • Increase in Production Capacity as Processing Time Greater Than Setup Times

  • Inventories Allow Purchase in Larger Quantities Lowering Ordering

    Cost Per Unit While Taking Advantage of Quantity Discounts As well


Managing inventory

OPERATION LEVELING

Quantity

Jan

Mar

Jun

Sep

Dec

Seasonal Demand

Production


Managing inventory

INVENTORY COSTS

  • Item Cost/ Landed Cost

    • Purchased Item=Purchase Price+Transportation Cost+Insurance+Customs Duties

    • Manufactured Item= Direct Material + Direct Labour + Factory Overhead

  • Carrying Costs/ Holding Costs: Incurred Due To Volume of Inventory

    Carried that Increases/ Decreases When Volumes Increase/ Decreases

  • Capital Costs: Depends On Interest Rate/ Credit Rating of Firm/ Other Investment

    Opportunities

    • Money Invested in Inventory & Not Available for Other Uses Thus Representing

    • Loss Opportunity Cost.

    • Minimum Cost is Loss of Interest

  • Storage Costs: Depends on Location & Type of Storage Needed

    • Costs Related to Storing Space/ Workers/ Handling Equipment

  • Risk Costs: Normally Low Value But 100% of Item Value for Perishable Items

    • Obsolescence-Loss of Product Value Due to Model/ Style/ Technology Change

    • Damage – Product/ Packaging Damage in Store/ Transit

    • Pilferage – Goods Lost/ Stolen

    • Deterioration – Rots/ Dissipates in Storage/ Limited Shelf Life

  • Carrying/ Holding Costs Expressed as Percentage of Rupee Value of Inventory per

    Unit of Time (Usually One Year)–Normally 20-35 % Per Year/Higher for Fashion Items


Managing inventory

EXAMPLES

A company carries average annual inventory of Rs. 2, 000,000. They

estimated their costs of capital, storage and risk are 10%, 7% and 6%

respectively. Calculate how much it costs annually to carry the inventory

Total Cost of carrying Inventory = Cost of Capital + Storage Cost + Risk Cost

= 10% + 7% + 6% = 23%

Annual cost of carrying Inventory = 23/100 ×2,000,000

= Rs. 460,000.00

Given the following percentage costs of carrying inventory, calculate the annual carrying cost if the average inventory is $1 million. Capital costs are 10%, storage costs are 6% and risk costs are 7%.

Total Cost of carrying Inventory = 10%+6%+7% = 23%

Annual cost of carrying Inventory = 0.23×1,000,000 = $230,000.00

A florist carries an average inventory of $10, 000 in cut flowers. The flowers need special storage and are highly perishable. The florist

estimates capital cost at 10%, storage cost at 25% and risk costs at 50%, What is his annual carrying cost?

Total Cost of carrying Inventory = 10%+25%+50% = 85%

Annual cost of carrying Inventory = 0.85×10,000 = $8,500.00


Managing inventory

INVENTORY COSTS

  • Ordering Costs

    • Costs Associated With Placing an Order with Factory/ Supplier

    • Not Dependent on Quantity Mentioned in the Order

    • Annual Cost of Ordering Depends On Number of Orders Placed During the Year

  • Ordering Costs in Manufacturing Include

  • Production Control Costs

    • Annual Costs & Effort Expended in Production Control Depend on Number of

    • Production Orders Placed Not the Quantities Ordered in Each

    • Costs Related to Issuing/ Closing Orders/ Scheduling/ Machine Loading/

      • Dispatching/ Expediting

  • Set Up & Teardown Costs

    • Work Centres Need to be Set Up Every Time To Run New Production Order & Tear

    • Down The Set Before New Order is Taken Up

    • Costs Not Dependent On Order Quantity But on Number of Orders Placed Per Year

  • Lost Capacity Costs

    • Every Time Order Placed with Work Centre Time Taken to Set Up is Lost Productive

    • Output Time

    • Particularly Important & Costly are Set Up Costs at Bottleneck Work Centres


Managing inventory

INVENTORY COSTS

  • Ordering Costs in Purchasing

  • Purchase Order Cost

    • Costs Incurred to Place an Order Depends on Number of Orders Not Ordered Quantities

    • Related to Order Preparation/ Follow Up/ Expediting/ Receiving/ Authorizing Payments

    • Quality Inspection/ Transportation Costs

    • Accounting Cost of Receiving/ Paying the Invoice

  • Stock-Out Costs

    • When Demand During Lead Time of Supply Exceeds Forecast Stock- Out

      CostsIncreases due to

      • Back-Order Costs

      • Lost Sales

      • Lost Customers

    • Carrying Extra Inventory Protects Against Stock Outs

  • Capacity-Associated Costs

    • When Output Levels Need To be Changed Cost incurred in Overtime/ Hiring/

      Training/ Running Extra Shifts / Layoffs

    • Costs Can be Avoided By Leveling Production & Producing at Same Rate During

      Slack Times for Sale During Peak Periods

    • Production Leveling Builds Inventory During Slack Periods


Managing inventory

EXAMPLE

  • Calculate average cost of placing one order with the annual costs given below:

  • Production Control department salaries= Rs60,000

  • Supplies & operational expenses for PC department= Rs15,000

  • Cost of setting up work centres for an order= Rs120

  • Orders placed each year= 2,000

Average cost of One order= Fixed Cost/ No. of orders + Variable Cost

= (60000+15000)/2000 + 120= Rs157.50

Annual purchasing salaries are $65,000, operating expenses for the purchasing

Department are $25,000 and inspecting & receiving costs are $25/ order. If the

purchasing department places 9,000 orders a year, what is the average cost of

ordering? What is the annual cost of ordering?

Average cost of ordering=Fixed Cost/ No. of Orders + Variable Cost

= (65000+25000)/ 9000 + 25=$35.00

Annual cost of ordering=Fixed Cost + Variable Cost × Annual No. of Orders

= (65000+25000) + 9000 × 25=$315,000


Managing inventory

EXAMPLE

An importer operates a small warehouse that has the following annual costs

Wages for purchasing are $45,000, purchasing expenses are $30,000, customs

and brokerage costs are $25/ order, the cost of financing the inventory is 8%,

Storage costs are 6% and the risk costs are 10%. The average inventory is

$250,000 and 5,000 orders are placed in a year. What are the annual ordering

and carrying costs?

Total Cost of carrying Inventory = Cost of Capital+Storage Costs+Risk Costs

= 8% + 6% + 10% = 24%

Annual cost of carrying Inventory = 0.24 ×250,000 = $60,000

Average cost of One Order= Fixed Cost/ No. of Orders + Variable Cost

= (45000+30000)/5000 + 25= $40

Annual cost of Ordering=Average Cost of One Order × No. of Annual Orders

= 40 × 5000=$200,000


Managing inventory

EXAMPLE

A company makes and sells a seasonal product. Quarterly Sales forecasts

for the product are 2,000, 3,000, 6,000, 5,000 Items for the next year.

Calculate level production plan, quarterly ending inventory and average

quarterly inventory.

If inventory carrying costs are $3 per unit per quarter, what will be the

annual cost of carrying inventory? Assume opening and closing inventories

as zero.

Q1 Q2 Q3 Q4Total

Sales Forecast200030006000500016000

Production Plan400040004000 4000 16000

Ending Inventory 0200030001000 0

Average Inventory100025002000 500

Inventory Cost ($3/Unit) 300075006000 1500 18000.00

Average Inventory = Opening Inventory + Ending/Closing Inventory

2


Managing inventory

EXAMPLE

A company manufactures and sells a seasonal product. Based on the

Quarterly sales forecasts that follows, calculate level production plan,

quarterly ending Inventories and average quarterly inventories. Assume that

the average quarterly inventory is the average of starting and ending

inventory for the Quarter. If inventory carrying costs are $3 per unit per

quarter, what will be the annual cost of carrying this anticipation inventory?

Opening and ending Inventories are zero.

Q1 Q2 Q3 Q4Total

1000200030002000

8000

Sales Forecast

2000200020002000 8000

Production Plan

1000

1000

0

0

Ending Inventory 0

Average Inventory

500

1000

500

0

Inventory Cost

($3/ Unit)

3000

1500

$6,000

1500

0

Annual cost of carrying anticipatory Inventory = $6,000


Managing inventory

EXAMPLE

Given the following data, calculate a level production plan, quarterly ending

Inventory and average quarterly inventory. If inventory carrying costs are

$6 per unit per quarter, what is the annual carrying cost? Opening and ending

Inventories are zero.

If the company always carries 100 units of safety stock, what is the annual

cost of carrying it?

Q1 Q2 Q3 Q4Total

500080008000 10000

31000

Sales Forecast

7750775077507750 31000

Production Plan

0

0

2750

2500

2250

Ending Inventory

Average Inventory

1375

2625

2375

1125

Inventory Cost

15750

14250

$45,000

8250

6750

$6

Ending Inventory 100 2850 2600 2350 100

Average Inventory 1475 27252475 1225

Inventory Cost $6 8850 16350 14850 7350 $47,400


Managing inventory

SELECTIVE CONTROL OF INVENTORY

  • Inventory Managed By Controlling Individual Items – Stock-Keeping

    Units (SKU) & That Involves Costs

  • For Effective Inventory Control at Reasonable Cost Large Number of

    Items in Inventory Are Classified According To Importance of The SKU

    for Operations/ Business

  • Classifications Used To Render Selective Treatment to Different

  • Category of Material

  • Different Inventory Control Methods Used for Items Based On Different

    Selection Criteria

  • Each Classification Emphasizes On a Particular Aspect

  • Seasonality

  • Stock Turnover Rate

  • Consumption Rate

  • Value of Stocks

  • Annual Usage Value

  • Unit Price of Item

  • Criticality of Item

  • Difficulties in Procurement

  • Procurement Source


Managing inventory

SELECTIVE INVENTORY MANAGEMENT

Item ClassificationCriteria for Selection

A-B-C (Always Better Control)Annual Usage Value

H-M-L (High, Medium, Low) Unit Price of Item

V-E-D (Vital, Essential, Desirable)Criticality of Item

S-D-E (Scarce, Difficult, Easy) Difficulties in Procurement

G-O-L-F (Government, Ordinary, Procurement Source

Local, Foreign)

S-OS (Seasonal, Off- Seasonal) Nature of Supplies

M-N-G (Moving, Non Moving, Ghost Items) Stock Turnover Rate

F-S-N (Fast, Slow, Non Moving) Consumption Rate

XYZ Value of Items in Stores

Categorizing Items in Stock Into Manageable Groups

Facilitates Inventory Control with the Right Focus


Managing inventory

A-B-C CLASSIFICATION - METHODOLOGY

Determine Annual Usage of Each Item

Multiply Annual Usage of Item by Its Cost To Get Total Annual Usage Value

List Items According to Annual Usage Value in a Descending Order

Calculate the Cumulative Annual Usage Value & Cumulative Percentage of Items

Examine Annual Usage Distribution & Group Items into A/ B/ C Groups Based on Percentage of Annual Usage

Used in Controlling Inventories of Raw Material/

Components/ WIP/ Finished Goods


Managing inventory

10% of Items

75% of Value

A -

15% of Items

15% of Value

B -

75% of Items

10% of Value

C -

A–Frequently Monitored+

Lower Safety Stock

To Avoid Stock Outs

C– Least Frequently

Monitored+

Highest Safety Stock

A-B-C CLASSIFICATION

Cumulative

Value %

100

90

75

10

100

25

A

B

C

% Items


Managing inventory

EXAMPLE

A company manufactures a

line of 10 items. Their usage

and unit cost are shown in

the accompanying table along with annual Rupee value usage of each.

Group items into ABC Classification.


Managing inventory

SOLUTION

  • A-Class

  • 20% - Items

  • 78.43%-Value

  • B-Class

  • 30% -Items

  • 16.99%-Value

  • C-Class

  • 50% -Items

  • 4.58%-Value


Managing inventory

INVENTORY CLASSIFICATION - ABC ITEMS

  • A-Class Items

    • High Priority Items Represent About (10-15)% of Items that Account

    • for About 70-80% of Value

    • Tight Control on Inventory

      • Keep Complete & Accurate Records

      • Regular + Frequent Review of Demand Forecasts

      • Close Follow-Up + Expediting Supplies To Reduce Lead Time

  • B-Class Items

    • Medium Priority Items Represent About (10-15)% of Items that Account

    • for About (10-15)% of Value

    • Normal Control on Inventory

      • Keep Good Records

      • Regular Attention To Demand Forecasts

      • Normal Processing

  • C-Class Items

    • Lowest Priority Items Represent About (70-50)% of Items that Account

    • for About (10-15%) of Value

    • Simplest Possible Control On Inventory - Stock Large Quantities

      • Simple Records with Periodic Review of Stocks

      • Order Large Quantities & Carry Safety Stocks


Managing inventory

H-M-L ANALYSIS

  • H - Category of Items

    • High Priced Items

      • Tight Control on Consumption

      • More Frequent Verification of Stocks

      • Purchase Policies for Closer Control on Purchase

      • Higher Storage Security (Locked in Steel Cupboards)

  • M - Category of Items

    • Medium Priced Items

      • Medium Control on Consumption

      • Frequent Verification of Stocks

      • Medium Control on Purchase

      • Medium Security of Storage

  • L - Category of Items

    • Low Priced Items

      • Less Control on Consumption

      • Less Frequent Verification of Stocks

      • Less Stringent Control on Purchase

      • Standards Security Provided

Used In Controlling Purchased Inventory


Managing inventory

V-E-D ANALYSIS

  • V - Category of Items: Vital for Production/ Consumers

    • Item in C Category May Come Under Vital Category If

      • Non-Availability Will Cause Serious Problems/ High Stock-Out Costs

      • Large Lead Time for Procurement

      • Non-Standard Item Purchased Against Purchaser’s Design

  • E - Category of Items: Essential Items

    • High Cost of Stock-Out

  • D - Category of Items: Desirable Items

    • Nominal Cost of Stock-Out Not Affecting Business in a Big Way

  • Factors for Deciding VED Category of Items

    • Stock-Out Costs

    • Lead Time for Procurement

    • Nature of Item: Standard/ Supplier Designed/ Buyer Designed

    • Source of Supply: Local/ Outstation/ Imported/ Controlled Item

  • ABC & VED Analysis Normally Used Together for Controlling

  • Inventory of Spares/ Parts

Criteria of Selection - Criticality of Item


Managing inventory

S-D-E ANALYSIS

  • S-D-E Analysis Based on Problems Related To Procurement

    • Non-Availability/ Scarcity of Items

    • Unusually Long Lead Time

    • Geographical Location of Suppliers

    • Reliability of Suppliers

  • Items Classified Under 3 Groups

    • Scarce

      • Short Supply/ Long Lead Time/ Imported/ Through Govt. Agencies

      • Best to Limit No. of Times to Order

    • Difficult

      • Available Locally

      • No/ A Few Reliable Source Available

      • Needs Advance Notice/ Long Lad time of Procurement

    • Easy: Readily Available Standard Products

  • S-D-E Analysis Mostly Used in Purchase Department

    • For Deciding Purchase Methods of Different Category of Items

    • Allocating Responsibility By Seniority Levels of Purchasers/ Buyers

Used in Lead Time Analysis & Purchase Strategy Formulation


Managing inventory

G-O-L-F ANALYSIS

  • Based on Nature of Suppliers that Determine

    • Quality of Items

    • Lead Time of Supply

    • Terms of Payment

    • Continuity of Supplies

    • Administrative Work Involved

  • Classifies Items into 4 Groups By Source of Supplies

  • G: Government Suppliers – Public Sector Undertakings

    • Involves Long Lead Times

    • Payment in Advance/ Against Delivery

  • O: Ordinary (Non-Government) Suppliers

    • Moderate Delivery Lead Times

    • Credit Facility Available

  • L: Local Suppliers

    • Easy Availability

    • Purchased Against Cash/ Blanket Orders

  • F: Foreign Suppliers

    • Large Amount of Administrative/ Procedural Time & Costs Involved

    • Extensive Sourcing Necessary for Identifying the Right Supplier

    • Letter of Credit Method for Payment

    • Shipping/ Port/ Customs Clearance Needs Special Efforts/ Costs

Used in Procurement Strategies


Managing inventory

S-OS ANALYSIS

  • Items Grouped into 2 Groups Based on Seasonality of Product

    • S: Seasonal

    • OS: Off Seasonal

  • Seasonal

  • Seasonal Availability But Marketing Round the Year

    • Items Available Only During Season – Mangoes/ Oranges/ Fruits

    • Procured for Use in Packaged Food Industry for the Whole Year

  • Seasonal But Available Round the Year

    • Price Lowest During Harvesting Time

    • Procurement Based on Cost Comparison Between

      • Buying at Lower Price During Harvest Season & Holding Stocks for

      • Whole Year

      • Buying Throughout the Year

  • Seasonal Market But Available Round the Year – Winter Garments

    • Produced Round the Year to Meet High Seasonal Demand

    • Higher Inventory Carrying Cost Balanced By Lower Cost of

    • Producing at Uniform Level in Meeting The Seasonal Demand

  • Off Seasonal – Non-Seasonal Items

Used in Procurement/ Holding Strategies for

Seasonal Items – Agricultural Products


Managing inventory

M-N-G ANALYSIS

  • Based on Stock Turnover Rate Items Classified as

    • M: Moving Items – Regular Consumption

    • N: Non-Moving Items – Not Consumed for last 1 Year

    • G: Ghost Items – No Stocks/ No Receipt & Issue Last Financial Year

F-S-N ANALYSIS

  • Used in Controlling Stock Obsolescence

  • Last Date of Receipt/ Issue Considered To Calculate Period When

  • Stocks Did Not Move for Classifying Items

    • F: Fast Moving

    • S: Slow Moving

    • N: Non-Moving

  • S & N Category of Items Further Analyzed Conducting Ageing

  • Analysis To Decide on Appropriate Ways of Disposing Stocks

X-Y-Z ANALYSIS

  • Used to Review Inventories & Consumption at Scheduled Intervals

  • Based On Value of Stocks in Stores

    • X Items: High Value of Inventory

    • Y Items: Moderate Value of Inventory

    • Z Items: Low Value of Inventory


Managing inventory

INVENTORY CONTROL IN COMBINATION

  • X-Y-Z Analysis Used Along with ABC/ FSN Analysis Helps

    • To Identify Few Items Comprising Large Value Locked Up in Inventory

    • Indicate Actions Need to be Taken for Improving Company’s Stock Profile

  • X Items: High Value of Inventory

  • Y Items: Moderate Value of Inventory

  • Z Items: Low Value of Inventory

Class of Items ABC

XWork to Reduce Work to Convert Dispose Off

Stocks To Z category To Y Category Surplus Stocks

YConvert To Z category Tighten Control

Z Review Stock Levels More Often

Class of Items FSN

XTighten Control Reduce StocksDispose Off

To Low Levels at Optimum Prices

YReduce Stocks Dispose Off Earliest

ZLessen ControlDispose Off Even

To Reduce Admin CostsAt Lower Prices


Managing inventory

INVENTORY CONTROL

  • Manage & Control Inventory To Balance

  • Required Level of Product Availability

  • Cost of Providing Desired Product Availability

  • Inventory Management & Control Affects

  • Customers

  • Suppliers

  • Major Departments in Organization

Inventory Control Exercised Through

Inventory Performance Measures


Managing inventory

INVENTORY PERFORMANCE METRICS

  • Product Availability (Service Level)

Quantity of An Item Available as Required During a Period

=

100

Total Demand for The Item During That Period

Higher Service Level Implies

Higher SC Responsiveness

  • Inventory =

Throughput

Cycle Time

Reduce Inventory By Reducing Cycle Time


Managing inventory

FINANCIAL PERFORMANCE METRICS

  • Inventory Turnover Ratio/ Inventory Turns

    Financial Measure of How Effectively inventory is Used in Making Sales

Annual Costs of Goods Sold

Inventory Turns=

Average Inventory in Money Value

  • Days of Supply

    Financial Measure of Equivalent Number of Days of Inventory On Hand

    Based on Daily Usage Rate

Inventory On Hand

Inventory in Days of Supply=

Average Daily Usage

  • Higher Inventory Turns Imply Higher Efficiency in Using Inventory Asset

  • Financial Metrics Relates To Sales/ Revenues Generated By the Inventory

  • Financial Metrics Measure Inventory Management Performance Better

    than Just Measuring Cost of Inventory Managed


Managing inventory

EXAMPLE

A company has 9000 Units on hand and the annual usage is 48,000 units.

Assuming 240 working days in a year calculate what is the inventory in terms

of days of supply?

If the annual cost of the goods sold is Rs 24 million a year and Value of

Average inventory held is Rs 6 million what will be the inventory turns? What

will be the reduction in inventory if the turns are increased to 12 times/ year?

If cost of carrying inventory is 25% of average inventory, calculate the Savings

  • Inventory in days of supply= Average inventory on hand/ Average daily use

= 9000/ (48,000÷240) = 45 Days of Sales

  • Inventory turns=Annual Cost of Goods Sold/ Average inventory

= 24 ÷ 6 = 4

  • When Inventory turns increased to 12,

  • Average Inventory= Annual COGS/ Turns

= 24 ÷ 12 = $2 Million

  • Reduction in average inventory= 6,000,000 – 2,000,000 = $4 Million

Carrying cost of inventory=25%

Savings=25%× 4,000,000= $1,000,000


Managing inventory

DEFINITIONS IN INVENTORY CONTROL

  • Stock Keeping Unit - Items Packed as Individual Units in Inventory

    Controlled By Quantity & Time of Procurement

    • Same Products with Different Colour/ Size/ No. Packed – Different SKU

  • Lot/ Batch – Quantity Produced/ Purchased Together Sharing Same

    Production/ Purchase Costs & Specifications

  • Lot-for-Lot Rule–Order Exactly As Needed & When Required

    • Ordered Quantity Changes Every Time Requirement Changes

    • Unused Lot-Size Inventory Not Created as SKU Ordered When Needed

    • Applicable for High Value Items & JIT Applications

  • Fixed-Order Quantity Rule – Arbitrarily Specifies No. of Units/ SKU

    To Order Each Time Order is Placed

    • Based On Usage Rate/Lead Time/Future Demand For Given Time Period

    • Does Not Minimize Costs Involved

  • Min-Max System – A Variation of Fixed Order Rule

    • When Quantity On Hand Reaches Reorder Level New Order Placed for

      Quantity = Max Level – Quantity On Hand


Managing inventory

INVENTORY COSTS

  • Ordering/ Set Up Costs

  • Transportation/ Receiving/ Inspection

  • Carrying/ Holding Costs

  • Space

  • Capital

  • Inventory Servicing

  • Inventory Risk

  • Stock-Out Costs

  • Inventory Costs are in Trade-Off With Each Other

Total Annual Inventory Costs (TAIC) =

Annual (Material Cost + Ordering Cost + Carrying Costs)


Managing inventory

CARRYING COST ELEMENTS

  • Interest & Opportunity Costs …….82%

  • Obsolescence & Physical Depreciation Costs .. 14%

  • Storage & Handling Costs ……. 3.25%

  • Taxes …….. 0.50%

  • Insurance ……… 0.25%

Annual Carrying Costs 20% to 35% of Value of Inventory


Managing inventory

ANNUAL TOTAL COST

  • Cost of Ordering & Carrying Inventory Depend on No. of Orders

  • Placed in a Year & Quantity Ordered Each Time

  • Relevant Costs for Inventory Control

  • Annual Costs for Placing Order: Ordering Cost

  • Annual Costs of Carrying Inventory: Annual Carrying Cost as % of

    Annual Average Inventory

S = Annual Demand in Units

Cu = Unit Price (Rs)

q = Order Quantity in Units

Cp = Ordering Cost/ Order (Rs)

i = Inventory Carrying Cost as Percentage of Average Inventory Investment

  • Annual Ordering Cost = No. of Orders/Year × Ordering Cost =

S/q × Cp

  • Annual Carrying Cost = Average Inventory × Inventory Carrying Cost

= ½ × Order Quantity × Carrying Cost(%) × Unit Price =

q/2 × i × Cu

  • Annual Total Cost = Annual Ordering Cost + Annual Carrying Cost

ATC = (S/q × Cp) + (q/2 × i × Cu)


Managing inventory

2.S.Cp

i.Cu

S × Cp

i × Cu

2

d(ATC)

dq

Or q² =

=

Or

2.S.Cp

i.Cu

Or q =

2 × Annual Demand × Ordering Cost/ Order

Inventory Carrying Cost × Unit Price

EOQ FORMULA DEVELOPMENT

  • Optimizing of Inventory Model Involves Calculating Order Quantity

    ‘q’ That Minimizes Annual Total Cost (ATC)

  • Differentiating ATC with Respect to ‘q’ & Setting First Derivative to

    Zero will Minimize Annual Total Cost

ATC= (S/q × Cp) + (q/2 × i × Cu)

S × Cp

i × Cu

2

Or

= –

= 0

+

EOQ =


Managing inventory

ECONOMIC ORDER QUANTITY

Total Cost/Unit Time

Cost

Inventory Carrying Cost

Ordering/ Set up Cost

EOQ

Quantity

  • Ordering Cost vis-à-vis Carrying Cost Trade-off

  • Total Annual Cost Gets Optimized When Ordering Cost=Carrying Cost

  • Economic Order Quantity Ensures Optimal Annual Total Cost of Inventory

2 × Annual Demand × Ordering Cost/ Order

EOQ = 

InventoryCarrying Cost × Unit Price


Managing inventory

2 × Annual Demand × Ordering Cost/ Order

Inventory Carrying Cost × Unit Price

EOQ =

EXAMPLE

A company uses 75 number of an item per month. Each unit costs

the company Rs 25/-. Cost of placing each order & inventory carrying

charges per month are computed at Rs 36/- and 1.5% of the average

inventory investment respectively. Calculate the economic lot size for

purchase of the item to minimize total cost.

Annual Demand = 75 × 12 = 900 Units

Ordering Cost/ Order = Rs 36

Inventory Carrying Cost/ Year = 1.5/100 × 12 = 0.18

2 × 900 × 36

0.18 × 25

EOQ =

= 120 Units


Managing inventory

ASSUMPTIONS IN EOQ MODEL

  • Annual Demand is Known & Remains Constant

  • Known Delivery Time that Does Not Change

  • Replenishment of Stock is Instantaneous

  • Unit Price Fixed & No Quantity/ Price Discounts Allowed

  • Inventory Carrying Cost Known and Remains Constant

  • Ordering Cost is Known and Remains Constant

  • No Stock-Outs Allowed

  • Items Can be Procured Free From Any Restriction

One Variation of Classical EOQ Model

is Quantity Discount/ Price-Break Model


Managing inventory

QUANTITY DISCOUNT/ PRICE-BREAK MODEL

  • Constant Unit Price Condition Relaxed & Purchase Quantity

  • Discounts Allowed

  • Purchase Cost & Total Annual Inventory Cost are Important

  • Criteria For Determining Optimal Order Size

  • Lowest TAIC (Total Annual Inventory Costs)

  • = Annual Material Costs + Annual Ordering Costs +

  • Annual Carrying Costs

  • Procedure to Arrive at Best Order Quantity

  • For Each Purchase Price Calculate EOQ

  • If EOQ Too Low To Qualify for Price Discounts Increase Quantity to

  • Match Lowest Qualifying Order Quantity

  • Calculate TAIC for Each Price & Corresponding Quantity

  • Select Price/ Quantity Combination that Results in Lowest TAIC

  • (Total Annual Inventory Costs)


Managing inventory

2 × Annual Demand × Ordering Cost

EOQ =  -----------------------------------------------

Carrying Cost × Unit Price

QUANTITY DISCOUNT/ PRICE-BREAK MODEL

Soccer Ball Example

Supplier’s Offer:

Order Qty. of Soccer Balls Price ($)

Below 1, 000 5.00

Between (1, 001 – 2, 000) 4.50

Above 2, 000 4.00

Customer Data:

Ordering Cost = $40

Annual Demand = 15, 000

Carrying Cost = 25%

  • EOQ with $5 price =  [2×15000×40] ÷ [0.25 × 5] = 980 Balls

  • EOQ with $4.5 price =  [2×15000×40] ÷ [0.25 × 4.5] = 1, 032 Balls

  • EOQ with $4..0 price =  [2×15000×40] ÷ [0.25 × 4)] = 1, 095 Balls

Right Quantity & Price to Achieve Best Savings is the Combination

That Results in Lowest Total Annual Inventory Cost (TAIC)


Managing inventory

QUANTITY DISCOUNT/ PRICE-BREAK MODEL

Soccer Ball Example

Total Annual Inventory Costs (TAIC) = Annual Material Cost (AMC)

+ Annual Holding Cost (AHC) + Annual Ordering Cost (AOC)

TAIC = (Annual Demand × Unit Price) + {(EOQ ÷ 2)×(Carrying %)

×Unit Price} + {(Annual Demand÷ EOQ) × Ordering Cost}

  • TAIC ($5) = (15, 000×5) + {(980/ 2)(0.25)×5} + {(15, 000/ 980)(40)}

    = $ 76, 225

  • TAIC ($4.5) = (15, 000×4.5)+{(1,032/ 2)(0.25)×4.5}+{(15, 000/ 1,032)(40)}

    = $ 68, 662

  • TAIC ($4.0) = (15, 000×4)+{(2,001/ 2)(0.25)×4}+{(15, 000/ 2,001)(40)}

    = $ 61, 300

Best Combination for Purchase of Soccer Ball Is the

Combination of Lowest Quantity Providing Highest Savings

i.e. 2, 001 Balls at Discounted Price of $4 per Ball


Managing inventory

EOQ MODEL IN BUSINESS

  • EOQ Derived From Mathematical Model Used as Guideline &

    Often Modified To Suit Business Requirements & Constraints

  • A Few Constraints That Demands Modification of EOQ Model

  • Supplier’s Minimum Order Quantity Conditions

  • Lead Time

  • Government Regulations

  • Seasonal Availability

  • Price Discounts

  • Packing Size

  • Space Restriction

  • Risk of Obsolescence & Deterioration

  • Unstable Market Conditions

  • EOQ Normally Modified To Take Care of Current Business

    Environment – MOQ (Modified Order Quantity)

Top Management Involved in Developing Inventory Policy To Match Company’s Strategic/ Marketing/ Financial/ SCM Goals


Managing inventory

INVENTORY POLICY ELEMENTS

  • Quantity To Order/ Lot Size Decision

  • Time To Order

  • Safety Stock To Insure Against Uncertainty

  • Use Factor Z from Normal Distribution Chart

  • Supply Lead Time Variability

  • Desired Delivery Service Level

  • Product Fill Rate

  • Order Fill Rate

  • Cycle Service Level (CSL)

Inventory Policy Implemented Through

Stock Replenishment Models


Managing inventory

STOCK REPLENISHMENT MODELS

  • Fixed Order Quantity (FOQ) Replenishment Model – Also Known as

    Order Point Systems

    • A Critical Stock Level of Each Item is Defined Based On

      Average Demand During Lead Time: Reorder Level

    • If Stock Falls below This Level a Replenishment Order Placed

    • Plot of Stock Against Time will Follow a Saw-Tooth Pattern

    • Requires Continuous Monitoring of Stock Levels

    • Assumes Past Demand Good Indication of Future Demand

    • Order Quantity Fixed But Order Interval Varies with Demand

    • Perpetual & Two-Bin Systems Follow the Fixed Order Quantity Models

  • Fixed Review Period (FRP) Replenishment Model

    • Stocks of Group of Products Reviewed at Regular Intervals

    • Sufficient Quantity Ordered so that Stock Levels Fall to

    • Safety Levels by the Time of Delivery after Next Review Period

    • Fixed Interval Between Orders But Quantity Varies with Demand

    • Periodic & Optional Replenishment Systems (Min-Max System) Follow

    • Fixed Review Models

Order Point System Works Well With Steady & Continuous Demand


Managing inventory

Q - Fixed Order Quantity

L – Lead Time of Supply

INVENTORY MODELS

FOQ Model

Quantity

Maximum Level

Q

Q

Q

Q

Average Level

Reorder Level

L

Buffer

Time

P - Fixed Review Period

FRP Model

L – Lead Time of Supply

Order Up to Level

Quantity

L

Buffer

P

P

P

P

Time


Managing inventory

INVENTORY COMPOSITION

  • Cycle Stock

  • EOQ × ½

  • Safety/ Buffer Stock

  • Based on Variation in Demand & Lead Times

  • Random Variation with Normal Distribution

  • Assumed

  • Average Stock

  • Cycle Stock + Safety Stock

  • Seasonal Stock

  • To Counter Predictable Demand Variability

Reduce Variations to Reduce Safety Stock


Managing inventory

SAFETY STOCK

  • Extra Stock To Protect from Stock Out Due To Uncertainty in

    Supply & Demand

  • Uncertainty in Supply & Demand Occurs in 2 Ways

  • Quantity Uncertainty - Occurs When Amount of Supply/ Demand

    Varies – Demand Greater/ Less Than Expected in a Given Period

  • Timing Uncertainty - Occurs When Time of Receipt of Supply/ Demand

    Differs From That Expected

  • Quantity Uncertainty is Protected By Carrying Safety Stocks &

    Timing Uncertainty Handled By Ordering/Receiving Early/ Late

  • Safety Stock Mostly Used To Buffer Against Uncertainty

  • Quantity of Safety Stock Required Depends on

  • Variability of Demand During Lead Time

  • Reordering Frequency

  • Desired Service Level

  • Lead Time Duration

  • Safety Stock Quantities Calculated Using Statistical Tools


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