It is desired to reduce inventories because, as levels increase, certain costs increase, for example:

Contenido

Los costos relevantes de los involucrados en la administración del desarrollo de los inventarios") son:.

Order cost

The cost generated by the activities carried out in a stock replenishment request is called "order cost", which may include, for example, the cost of paper, the cost of the telephone, the preparation cost and others.

Inventory storage cost

"Storage cost" is called "all the processes and activities carried out to maintain the order, good condition and existence of the inventory within the plant, including the cost of fixed assets of the product"), the cost of cleaning"), the cost of space").

Total inventory cost

The total inventory cost is the sum of the two previous costs: annual storage cost and annual ordering cost, according to the following formula:.

CT = total annual inventory cost.

Q= order size to replenish inventory, in units.

C= value of item handled in inventory, in $$/unit.

h= handling cost as a percentage of the item's value, percentage/year.

D= annual demand for items, which occurs at a certain constant rate over time, in units/year.

o= acquisition cost, in dollars/order.

When and how much are the questions on which stock management is based. In effect, if the inventory is replenished in short periods of time, the quantity ordered must be small, which reduces the cost of storage" but increases the cost of placing orders; if the inventory is replenished in long periods of time, the quantity ordered must be large, which reduces the cost of placing the order, but increases the cost of storage").

In inventory management there are inventory replenishment models that try to balance costs and reduce them as much as possible. With these models it is possible to know how much to order and when to order.

With fixed order interval models, an optimal fixed interval is determined for carrying out inventory reviews. Then each time an order is placed, stock is requested for the difference between some maximum and the quantity on hand.

POQ") determines the number of demand periods that will be covered by each order. This interval is calculated using the average demand and rounded to the next integer greater than zero. Each ordered quantity covers the projected requirements for the next interval with orders varying according to the requirements.

This algorithm is a heuristic approach to determining lot sizes that determines them by balancing ordering and storage costs. Selects the number of periods that should be covered by a replenishment order such that the accumulated storage costs barely exceed the ordering costs. Due to the discrete nature of requirements, an order size increases to the same extent that cumulative storage costs are less than or equal to the order cost. The goal is to determine lot sizes that include an integer number of periods.

This algorithm is similar to the PPA algorithm, except that instead of balancing cumulative storage and ordering costs, it balances incremental costs. The algorithm increases order sizes as incremental storage costs are less than or equal to order costs. The objective is to determine lot sizes that include an integer number of requirement periods. Similarly to the previous method.

Los siguientes modelos dan respuesta a la pregunta: ¿Cuánto pedir?

Economic Order Quantity (EOQ)

It consists of finding the point at which the costs of ordering the items and the costs of keeping them in inventory are equal. This is a method that does not give an optimal solution, but it is close to it.

Economic Production Lot (EPQ)

Items are produced and added to inventory gradually rather than in a single order. The EPQ model assumes continuous gradual releases to inventory (finite replacement rate) throughout the production period. With a finite replacement rate, the inventory level will never be the size of the production lot, since production and consumption occur simultaneously during the production period.

Silver and Meal Heuristics

Edward Silver") and Harland Meal") developed the Silver-Meal") heuristic model based on determining the average cost per period as the number of replacement periods increases. A replenishment order is placed when the first average cost increases. This method selects lot sizes that include an integer number of requirement periods such that the total relevant costs (storage and ordering costs) per period are minimized. This method guarantees a local minimum for the current order. Two situations in particular Where this algorithm does not work well are: (1) when the demand rate decreases rapidly over time and (2) when there are a large number of periods with zero demand.

Minimum unit cost

This method is similar to the Silver-Meal algorithm except that, instead of averaging costs across periods, it averages costs across units. This heuristic determines the average cost per unit as the number of periods in a replenishment order increases. An order is shipped when the average cost per unit first increases. The replacement period is reset and the procedure is repeated until lots are obtained in the time horizon.

The ABC" system is used to classify materials according to the economic value they represent in the inventory.

With this system, it is deduced that it is most convenient for the materials that maintain a greater volume in the inventory to be those that represent the lowest cost.

Exceptions from the ABC system must be made for certain types of materials:.

It is desired to reduce inventories because, as levels increase, certain costs increase, for example:

Contenido

Los costos relevantes de los involucrados en la administración del desarrollo de los inventarios") son:.

Order cost

The cost generated by the activities carried out in a stock replenishment request is called "order cost", which may include, for example, the cost of paper, the cost of the telephone, the preparation cost and others.

Inventory storage cost

"Storage cost" is called "all the processes and activities carried out to maintain the order, good condition and existence of the inventory within the plant, including the cost of fixed assets of the product"), the cost of cleaning"), the cost of space").

Total inventory cost

The total inventory cost is the sum of the two previous costs: annual storage cost and annual ordering cost, according to the following formula:.

CT = total annual inventory cost.

Q= order size to replenish inventory, in units.

C= value of item handled in inventory, in $$/unit.

h= handling cost as a percentage of the item's value, percentage/year.

D= annual demand for items, which occurs at a certain constant rate over time, in units/year.

o= acquisition cost, in dollars/order.

When and how much are the questions on which stock management is based. In effect, if the inventory is replenished in short periods of time, the quantity ordered must be small, which reduces the cost of storage" but increases the cost of placing orders; if the inventory is replenished in long periods of time, the quantity ordered must be large, which reduces the cost of placing the order, but increases the cost of storage").

In inventory management there are inventory replenishment models that try to balance costs and reduce them as much as possible. With these models it is possible to know how much to order and when to order.

With fixed order interval models, an optimal fixed interval is determined for carrying out inventory reviews. Then each time an order is placed, stock is requested for the difference between some maximum and the quantity on hand.

POQ") determines the number of demand periods that will be covered by each order. This interval is calculated using the average demand and rounded to the next integer greater than zero. Each ordered quantity covers the projected requirements for the next interval with orders varying according to the requirements.

This algorithm is a heuristic approach to determining lot sizes that determines them by balancing ordering and storage costs. Selects the number of periods that should be covered by a replenishment order such that the accumulated storage costs barely exceed the ordering costs. Due to the discrete nature of requirements, an order size increases to the same extent that cumulative storage costs are less than or equal to the order cost. The goal is to determine lot sizes that include an integer number of periods.

This algorithm is similar to the PPA algorithm, except that instead of balancing cumulative storage and ordering costs, it balances incremental costs. The algorithm increases order sizes as incremental storage costs are less than or equal to order costs. The objective is to determine lot sizes that include an integer number of requirement periods. Similarly to the previous method.

Los siguientes modelos dan respuesta a la pregunta: ¿Cuánto pedir?

Economic Order Quantity (EOQ)

It consists of finding the point at which the costs of ordering the items and the costs of keeping them in inventory are equal. This is a method that does not give an optimal solution, but it is close to it.

Economic Production Lot (EPQ)

Items are produced and added to inventory gradually rather than in a single order. The EPQ model assumes continuous gradual releases to inventory (finite replacement rate) throughout the production period. With a finite replacement rate, the inventory level will never be the size of the production lot, since production and consumption occur simultaneously during the production period.

Silver and Meal Heuristics

Edward Silver") and Harland Meal") developed the Silver-Meal") heuristic model based on determining the average cost per period as the number of replacement periods increases. A replenishment order is placed when the first average cost increases. This method selects lot sizes that include an integer number of requirement periods such that the total relevant costs (storage and ordering costs) per period are minimized. This method guarantees a local minimum for the current order. Two situations in particular Where this algorithm does not work well are: (1) when the demand rate decreases rapidly over time and (2) when there are a large number of periods with zero demand.

Minimum unit cost

This method is similar to the Silver-Meal algorithm except that, instead of averaging costs across periods, it averages costs across units. This heuristic determines the average cost per unit as the number of periods in a replenishment order increases. An order is shipped when the average cost per unit first increases. The replacement period is reset and the procedure is repeated until lots are obtained in the time horizon.

The ABC" system is used to classify materials according to the economic value they represent in the inventory.

With this system, it is deduced that it is most convenient for the materials that maintain a greater volume in the inventory to be those that represent the lowest cost.

Exceptions from the ABC system must be made for certain types of materials:.