Inventory

Inventory vs. Service Trade off

Problem Statement: A consumer electronics company with operations around the world is facing strong, growing demand for its products in the key South American markets of Argentina, Brazil and Chile.

Currently, the company has a single Central DC in Asuncion, Paraguay, and has the option to lease or buy local warehouse space. Since the possible feasible warehouse locations are already well known, optimization won’t help. We need to simulate various inventory deployment strategies, to determine the best trade-off between cost and service [figure1].

Analysis Results

1. Using Guru's Demand Flow policies, establish a baseline of customer delivery times in a pure “Make To Order” environment. Customer delivery times are consistently between seven and eight days for the baseline demand flow strategy [figure 2].

2. Using a baseline identical R-Q with a periodic review appears to be acceptable for the Chilean DC, but for Brazil and Argentina, this policy will cause large service problems [figure 3]. The network inventory investment holding cost = $7382.

3. Implementing an inventory policy using DOS - days of supply, using a moving average forecasting method immediately produces improvements:

The blue lines are the inventory levels, and the yellow lines are the back orders. After an initial adjustment period, inventory levels stabilize and service rates hover around 95% or so. However the inventory carrying cost under this scenario is $43,311 to achieve these service levels [figure 4].

Inventory in Supply Chain Guru is continuously tracked, and the inventory investment calculated by multiplying the Inventory Value x Inventory Level for each product, summed over all products.

In a supply chain with random variance in the demand and in segments of the supply delivery system, simulation is the only way to predict the actual service and inventory costs. This is a lot more intelligent than guessing and simply "hoping for the best" when you evaluate inventory strategies.


Guru Inventory Policy Table

Supply Chain Guru has numerous capabilities to model alternative inventory strategies and approaches, including:
R,Q: fixed reorder point, fixed reorder quantity
s,S: reorder threshold, variable reorder quantity
Demand Flow: one for one unit replacement (with or without base inventory level)
Days of Supply Demand: dynamic inventory targets based on moving average of demand
Days of Supply Forecast: dynamic inventory targets based on user specified forecasts and targets
Custom Inventory Policy: use Guru's powerful scripting capabilities to emulate your own planning algorithms



[figure 1]
Guru screen shot demonstrating probability distributions, GIS graphics and flowchart of supply chain process



[figure 2]
Graph cycle time of each individual order in the model to observe service rate and variability



[figure 3]
View detailed inventory levels and back orders over time



[figure 4]
Observe inventory targets, reorder thresholds and actual inventory levels

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