These lecture notes are based on the subject Global Supply Chain Management of 2015-2016.
Lecture 1 focuses mainly on:
- simulation
- Deterministic performance estimation
Both are approaches to to analyze and design a process.
There are different criteria to determine if a design is good or bad. A design is made in a flow diagram. These criteria are used to analyze the design. The main goal of analyzing a design, is to attain contiguous improvement.
Differences :
- Deterministic: easy and fast, but rough overview
- Simulation: long and complex, but gives a better and more specific outcome.
Simulation:
Simulation experiments many times, and tries to duplicate a real environment into its model. Mathematically, a real world situation is imaged. After wards, a conclusion is stated, and a company will decide if it will adapt to this conclusion.
Main advantages:
- It is used in difficult situations
- There is no investment needed
- Uncertainty is incorporated, so it is very functional in real life
- More solutions are shown
Main disadvantages:
- Analyzing and interpreting outcomes is difficult
- High computation time
- Difficult to make
- Value of the result is overestimated many times
Most of the large companies use this method.
To be able to understand the following topic, one must understand the following things:
- Throughput time
- Work-in-progress
- Bottleneck
- Throughput/departure rate
- Utilization & efficiency
Deterministic performance analysis:
There is a distinction between deterministic and stochastic determination time
- Deterministic: everything is known in advance
- Stochastic: things might change, not everything is known in advance
In order to know the deterministic throughput time, you must know the time between the point that the customer/product enters the system, and the costumer/product is ready. Always take the average time that is needed.
Design & effective capacity:
- Design: Theoretical maximum output
- Effective: capacity that can be expected given the circumstances
We distinct serial and parallel processing
- Serial: steps follow each other up
- Parallel: steps are done at the same time.
Parallel servers:
- One server can only serve one customer
- Other servers serve other customers simultaneous
You must be able to find the bottleneck in a system. Bottleneck = the part of a design that makes the rest of the design slower. It is similar to the statement: a design is a strong as its weakest link.
Departure rate = number of customers/products that leave the system per hour. Depends on the bottleneck of the system.
Utilization rate & efficiency:
- Utilization rate = total operating time/ total time = actual output/ design capacity
- Utilization efficiency = actual output/ effective capacity
Effective capacity = the time that could actually have been used.
Note: for the.....read more
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