Lec 2 Process Analysis

Productivity

• Def: Measure of how well resources are used

• Formula = Productivity = Output/Input

• Relative measure

• Compare to other firms within same industry

• Compare the same operation over time

Partial Measures

Partial Measures = Output/(Single Input)

Multi-Factor Measures

Multi-Factor Measures = Output/(Multiple Inputs)

Total Measure

Total Measure = Output/(Total Inputs)

Capacity

Definition: Maximum possible output rate

Cycle Time

• Definition: Average time between completion of successive units

• (Inverse of capacity)

Bottleneck

Slowest task of the process. Determines the cycle time of the process.

Key Steps in Process Analysis

• Step 1: Draw a flow diagram

  • Determine process boundary and flow unit

  • Determine the activities, sequence, and resources required for each activity

  • Determine buffers in process

• Step 2: Bottleneck Analysis

  • Determine capacity of each activity and of process

Whole Process

• Flow Time: Sum of cycle time

• Capacity Rate: Bottle neck of capacity rates (You want capacity rate to be higher, so bottle neck would be the smallest capacity rate) (minimum)

• Cycle Time: Bottle neck of cycle time (You want cycle time to be smaller, so bottle neck would be longest cycle time) (maximum)

Flow Time

Length of time a unit spends in the system

Theoretical Flow Time

Minimum flow time if no wait

Actual Flow Time

Flow time including waiting

Flow Time Efficiency

Theoretical Flow Time / Actual Flow Time

Little’s Law

Inventory = throughput Rate * flow Time

Throughput Rate

Output rate that the process is expected to produce over a period of time

Little’s Law works on averages

Avg I = Avg R * Avg T