Hi Ravi
Inventory is a list for goods and materials, or those goods and materials themselves, held available in stock by a business. Inventory are held in order to manage and hide from the customer the fact that manufacture/supply delay is longer than delivery delay, and also to ease the effect of imperfections in the manufacturing process that lower production efficiencies if production capacity stands idle for lack of materials.
The reasons for keeping stock
All these stock reasons can apply to any owner or product stage.
Buffer stock is held in individual workstations against the possibility that the upstream workstation may be a little delayed in providing the next item for processing. Whilst some processes carry very large buffer stocks, Toyota moved to one (or a few items) and has now moved to eliminate this stock type.
Safety stock is held against process or machine failure in the hope/belief that the failure can be repaired before the stock runs out. This type of stock can be eliminated by programmes like Total Productive Maintenance
Overproduction is held because the forecast and the actual sales did not match. Making to order and JIT eliminates this stock type.
Lot delay stock is held because a part of the process is designed to work on a batch basis whilst only processing items individually. Therefore each item of the lot must wait for the whole lot to be processed before moving to the next workstation. This can be eliminated by single piece working or a lot size of one.
Demand fluctuation stock is held where production capacity is unable to flex with demand. Therefore a stock is built in times of lower utilisation to be supplied to customers when demand exceeds production capacity. This can be eliminated by increasing the flexibility and capacity of a production line or reduced by moving to item level load balancing.
Line balance stock is held because different sub-processes in a line work at different rates. Therefore stock will accumulate after a fast sub-process or before a large lot size sub-process. Line balancing will eliminate this stock type.
Changeover stock is held after a sub-process that has a long setup or change-over time. This stock is then used while that change-over is happening. This stock can be eliminated by tools like SMED.
These classifications apply along the whole Supply chain not just within a facility or plant.
Where these stocks contain the same or similar items it is often the work practice to hold all these stocks mixed together before or after the sub-process to which they relate. This 'reduces' costs. Because they are mixed-up together there is no visual reminder to operators of the adjacent sub-processes or line management of the stock which is due to a particular cause and should be a particular individual's responsibility with inevitable consequences. Some plants have centralized stock holding across sub-processes which makes the situation even more acute.
Special terms used in dealing with inventory
Stock Keeping Unit (SKU) is a unique combination of all the components that are assembled into the purchasable item. Therefore any change in the packaging or product is a new SKU. This level of detailed specification assists in managing inventory.
Stockout means running out of the inventory of an SKU.[1]
"New old stock" (sometimes abbreviated NOS) is a term used in business to refer to merchandise being offered for sale which was manufactured long ago but that has never been used. Such merchandise may not be produced any more, and the new old stock may represent the only market source of a particular item at the present time.
[edit] Inventory examples
While accountants often discuss inventory in terms of goods for sale, organizations - manufacturers, service-providers and not-for-profits - also have inventories (fixtures, furniture, supplies, ...) that they do not intend to sell. Manufacturers', distributors', and wholesalers' inventory tends to cluster in warehouses. Retailers' inventory may exist in a warehouse or in a shop or store accessible to customers. Inventories not intended for sale to customers or to clients may be held in any premises an organization uses. Stock ties up cash and if uncontrolled it will be impossible to know the actual level of stocks and therefore impossible to control them.
Whilst the reasons for holding stock are covered earlier, most Manufacturing organizations usually divide their "goods for sale" inventory into:
Raw Materials - materials and components scheduled for use in making a product.
Work In Progress, WIP - materials and components that have begun their transformation to finished goods.
Finished goods - goods ready for sale to customers.
Goods for resale - returned goods that are salable.
High level inventory management
It seems that around about 1880[2] there was a change in manufacturing practise from companies with relatively homogeneous lines of products to vertically integrated companies with unprecedented diversity in processes and products. Those companies (especially in metalworking) attempted to achieve success through economies of scale - the gains of jointly producing two or more products in one facility. The managers now needed information on the effect of product mix decisions on overall profits and therefore needed accurate product cost information. A variety of attempts to achieve this were unsuccessful due to the huge overhead of the information processing of the time. However, the burgeoning need for financial reporting after 1900 created unavoidable pressure for financial accounting of stock and the management need to cost manage products became overshadowed. In particular it was the need for audited accounts that sealed the fate of managerial cost accounting. The dominance of financial reporting accounting over management accounting remains to this day with few exceptions and the financial reporting definitions of 'cost' have distorted effective management 'cost' accounting since that time. This is particularly true of inventory.
Hence high level financial inventory has these two basic formulas which relate to the accounting period:
1) Cost of Beginning Inventory (at the start of this period)+ Inventory Purchases (within this period)+ Cost of Production (within this period)= Cost of Goods
2) Cost of Goods - Cost of Ending Inventory (at the end of this period)= Cost of Goods Sold
Inventory Management and Inventory Control must be designed to meet the dictates of the marketplace and support the company's strategic plan. The many changes in market demand, new opportunities due to worldwide marketing, global sourcing of materials, and new manufacturing technology, means many companies need to change their Inventory Management approach and change the process for Inventory Control.
Despite the many changes that companies go through, the basic principles of Inventory Management and Inventory Control remain the same. Some of the new approaches and techniques are wrapped in new terminology, but the underlying principles for accomplishing good Inventory Management and Inventory activities have not changed.
The Inventory Management system and the Inventory Control Process provides information to efficiently manage the flow of materials, effectively utilize people and equipment, coordinate internal activities, and communicate with customers. Inventory Management and the activities of Inventory Control do not make decisions or manage operations; they provide the information to Managers who make more accurate and timely decisions to manage their operations.
The basic building blocks for the Inventory Management system and Inventory Control activities are:
Sales Forecasting or Demand Management
Sales and Operations Planning
Production Planning
Material Requirements Planning
Inventory Reduction
The emphases on each area will vary depending on the company and how it operates, and what requirements are placed on it due to market demands. Each of the areas above will need to be addressed in some form or another to have a successful program of Inventory Management and Inventory Control.
Reward if useful to u
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