Process analysis Flashcards
What assumption do we make on the values
all values are deterministic
What performance criteria are to be determined?
Throughput time
Work in progress
Location and maximum capacity of the bottleneck
Departure rate (=throughput)
Utilisation, efficiency
Inter-arrival time
Time between two subsequent arrivals of products at their entrance in the process
Arrival rate
Number of products that arrive per time unit
(eg: number of products that arrive per hour)
Throughput time
Time that passes between the moment at which the customer/product enters the system and the moment at which the customer/product is ready.
Deterministic throughput times
Can be estimated by adding up the expected processing times of the different process
Definition of deterministic
You ignore any probability distributions and just use the average.
What do you never consider when calculating the throughput time?
Do not consider the inter-arrival time
In calculating deterministic throughput times you need to follow the following 4 steps:
Estimate deterministic throughput time for one of the paths
Multiply resulting deterministic throughput time with probability that the path will be followed
Repeat 1 and 2 until all paths are handled.
Compute the total deterministic throughput time - sum of results of step 2
What happens when there are different types of products/customers in one system?
You don’t mix them up
Design capacity
Theoretical maximum output of a system or process in a given period.
Effective capacity
Actual capacity that can be expected given the product mix, methods of scheduling, maintenance and standards of quality.
Three step procedure for sufficiency of design capacity
Calculate design capacity of each process
Calculate the expected number of products arriving at that process (use percentages in systems with multiple paths)
Co pare answers from steps 1 and 2
Bottleneck
An operation that limits output in the system
What determines the departure rate?
The departure rate is determined by the capacity of the bottleneck
Only if the system has not bottlenecks that the arrival and departure rate are the same.
