Operations Management

Operations Management • Lecture 32 • Supply Chain Management • Inventory Management PowerPoint presentation to accompany Heizer/Render Principles of Operations Management, 7e Operations Management, 9e

Recap • Location Strategy-Cost and Innovation • Factors That Affect Location Decisions • Location Decisions • Methods of Evaluating Location Alternatives • Strategic Importance of Layout Decisions • Layout Design Considerations • Types of Layout

Outline • The Supply Chain’s Strategic Importance • Supply Chain Economics • Make-or-Buy Decisions • Outsourcing • Ethics in the Supply Chain • Supply Chain Strategies • Many Suppliers • Few Suppliers • Vertical Integration • Keiretsu Networks

Outline • Inventory • Functions of Inventory • Types of Inventory • Independent vs. Dependent Demand • Holding, Ordering, and Setup Costs • Inventory Models for Independent Demand • The Basic Economic Order Quantity (EOQ) Model • Minimizing Costs • Reorder Points

The Supply Chain’s Strategic Importance Supply chain management is the integration of the activities that procure materials and services, transform them into intermediate goods and the final product, and deliver them to customers Competition is no longer between companies; it is between supply chains

Supply Chain Management Important activities include determining Transportation vendors Credit and cash transfers Suppliers Distributors Accounts payable and receivable Warehousing and inventory Order fulfillment Sharing customer, forecasting, and production information

Reasons for Making Maintain core competence Lower production cost Unsuitable suppliers Assure adequate supply (quantity or delivery) Utilize surplus labor or facilities Obtain desired quality Remove supplier collusion Obtain unique item that would entail a prohibitive commitment for a supplier Protect personnel from a layoff Protect proprietary design or quality Increase or maintain size of company Make-or-Buy Decisions Table 11.4

Reasons for Buying Frees management to deal with its core competence Lower acquisition cost Preserve supplier commitment Obtain technical or management ability Inadequate capacity Reduce inventory costs Ensure alternative sources Inadequate managerial or technical resources Reciprocity Item is protected by a patent or trade secret Make-or-Buy Decisions Table 11.4

Outsourcing • Transfers traditional internal activities and resources of a firm to outside vendors • Utilizes the efficiency that comes with specialization • Firms outsource information technology, accounting, legal, logistics, and production

Ethics in the Supply Chain • Opportunities for unethical behavior are enormous and temptations are high • Many companies have strict rules and codes of conduct that define acceptable behavior • Institute for Supply Management has developed a detailed set of principles and standards for ethical behavior

Supply Chain Strategies • Negotiating with many suppliers • Long-term partnering with few suppliers • Vertical integration • Keiretsu • Virtual companies that use suppliers on an as needed basis

Many Suppliers • Commonly used for commodity products • Purchasing is typically based on price • Suppliers compete with one another • Supplier is responsible for technology, expertise, forecasting, cost, quality, and delivery

Few Suppliers • Buyer forms longer term relationships with fewer suppliers • Create value through economies of scale and learning curve improvements • Suppliers more willing to participate in JIT programs and contribute design and technological expertise • Cost of changing suppliers is huge

Vertical Integration Examples of Vertical Integration Vertical Integration Figure 11.2

Vertical Integration • Developing the ability to produce goods or service previously purchased • Integration may be forward, towards the customer, or backward, towards suppliers • Can improve cost, quality, and inventory but requires capital, managerial skills, and demand • Risky in industries with rapid technological change

Keiretsu Networks • A middle ground between few suppliers and vertical integration • Supplier becomes part of the company coalition • Often provide financial support for suppliers through ownership or loans • Members expect long-term relationships and provide technical expertise and stable deliveries • May extend through several levels of the supply chain

Managing the Supply Chain There are significant management issues in controlling a supply chain involving many independent organizations • Mutual agreement on goals • Trust • Compatible organizational cultures

Inventory • Anything that can be kept for future demand • Planning • Control (Where to buy, How much to buy? and when to buy?) • One of the most expensive assets of many companies representing as much as 50% of total invested capital • Operations managers must balance inventory investment and customer service

Functions of Inventory To decouple or separate various parts of the production process To decouple the firm from fluctuations in demand and provide a stock of goods that will provide a selection for customers To take advantage of quantity discounts To hedge against inflation

Types of Inventory • Raw material • Purchased but not processed • Work-in-process • Undergone some change but not completed • A function of cycle time for a product • Maintenance/repair/operating (MRO) • Necessary to keep machinery and processes productive • Finished goods • Completed product awaiting shipment

Inventory Management • How inventory items can be classified • How accurate inventory records can be maintained

Record Accuracy • Accurate records are a critical ingredient in production and inventory systems • Allows organization to focus on what is needed • Necessary to make precise decisions about ordering, scheduling, and shipping • Incoming and outgoing record keeping must be accurate • Stockrooms should be secure

Independent Versus Dependent Demand • Independent demand - the demand for item is independent of the demand for any other item in inventory • Dependent demand - the demand for item is dependent upon the demand for some other item in the inventory

Holding, Ordering, and Setup Costs • Holding costs - the costs of holding or “carrying” inventory over time • Ordering costs - the costs of placing an order and receiving goods • Setup costs - cost to prepare a machine or process for manufacturing an order

Basic EOQ Model Important assumptions Demand is known, constant, and independent Lead time is known and constant Receipt of inventory is instantaneous and complete Quantity discounts are not possible Only variable costs are setup and holding Stockouts can be completely avoided

Average inventory on hand Q 2 Usage rate Inventory level Minimum inventory 0 Time Inventory Usage Over Time Order quantity = Q (maximum inventory level) Figure 12.3

Curve for total cost of holding and setup Minimum total cost Holding cost curve Annual cost Setup (or order) cost curve Order quantity Optimal order quantity (Q*) Minimizing Costs Objective is to minimize total costs Table 11.5

D Q Annual setup cost = S Annual demand Number of units in each order Setup or order cost per order = = (S) D Q The EOQ Model Q = Number of pieces per order (Quantity Ordered) Q* = Optimal number of pieces per order (EOQ) D = Total Annual demand (in units) for the item which is kept as inventory S = Setup or ordering cost for each order H = Holding or carrying cost per unit per year Annual setup cost = (Number of orders placed per year) (Total Annual Ordering Cost) x (Setup or order cost per order)

D Q Annual setup cost = S Annual holding cost = H Order quantity 2 = (Holding cost per unit per year) = (H) Q 2 Q 2 The EOQ Model Q = Number of pieces per order Q* = Optimal number of pieces per order (EOQ) D = Annual demand in units for the inventory item S = Setup or ordering cost for each order H = Holding or carrying cost per unit per year Annual holding cost = (Average inventory level) x (Holding cost per unit per year)

D Q Annual setup cost = S Annual holding cost = H Q 2 D Q S = H 2DS = Q2H Q2 = 2DS/H Q* = 2DS/H Q 2 The EOQ Model Q = Number of pieces per order Q* = Optimal number of pieces per order (EOQ) D = Annual demand in units for the inventory item S = Setup or ordering cost for each order H = Holding or carrying cost per unit per year Optimal order quantity is found when annual setup cost equals annual holding cost Solving for Q*

2DS H Q* = 2(1,000)(10) 0.50 Q* = = 40,000 = 200 units An EOQ Example Determine optimal number of needles to order D = 1,000 units S = $10 per order H = $.50 per unit per year

Expected number of orders Demand Order quantity D Q* = N = = 1,000 200 N = = 5 orders per year An EOQ Example Determine optimal number of needles to order D = 1,000 units Q* = 200 units S = $10 per order H = $.50 per unit per year

Number of working days per year N Expected time between orders = T = 250 5 T = = 50 days between orders An EOQ Example Determine optimal number of needles to order D = 1,000 units Q* = 200 units S = $10 per order N = 5 orders per year H = $.50 per unit per year

Q 2 D Q 200 2 TC = S + H 1,000 200 TC = ($10) + ($.50) An EOQ Example Determine optimal number of needles to order D = 1,000 units Q* = 200 units S = $10 per order N = 5 orders per year H = $.50 per unit per year T = 50 days Total annual cost = Setup cost + Holding cost TC = (5)($10) + (100)($.50) = $50 + $50 = $100

Robust Model • The EOQ model is robust • It works even if all parameters and assumptions are not met • The total cost curve is relatively flat in the area of the EOQ

1,500 units Q 2 D Q 200 2 TC = S + H 1,500 200 TC = ($10) + ($.50) = $75 + $50 = $125 An EOQ Example Management underestimated demand by 50% D = 1,000 units Q* = 200 units S = $10 per order N = 5 orders per year H = $.50 per unit per year T = 50 days 1,500 units Total annual cost increases by only 25%

1,500 units 244.9 2 TC = ($10) + ($.50) Q 2 D Q TC = S + H 1,500 244.9 An EOQ Example Actual EOQ for new demand is 244.9 units D = 1,000 units Q* = 244.9 units S = $10 per order N = 5 orders per year H = $.50 per unit per year T = 50 days Only 2% less than the total cost of $125 when the order quantity was 200 TC = $61.24 + $61.24 = $122.48

Lead time for a new order in days ROP = Demand per day D Number of working days in a year d = Reorder Points • EOQ answers the “how much” question • The reorder point (ROP) tells when to order = d x L

D Number of working days in a year d = Reorder Point Example Demand = 8,000 iPods per year 250 working day year Lead time for orders is 3 working days = 8,000/250 = 32 units ROP = d x L = 32 units per day x 3 days = 96 units

Operations Management