Module 4 Process Analysis

Process analysis

Determines how many flow units can be processed per unit of time (the process capacity) and how busy the resources of the process are (utilization).

Process flow diagram

A graphical way to describe the process. It uses boxes for activities/resources, arrows for flows, and triangles for inventory location.

Upstream

The parts of the process that are at the beginning of the process flow.

Downstream

The parts of the process that are at the end of the process flow.

Processing time

The time it takes a resource to complete one flow unit.

Process capacity

The maximum flow rate a process can provide per unit of time. This determines the maximum supply of the process. The process capacity is the smallest capacity of all resources in the process.

Resource capacity

The maximum number of flow units that can flow through a resource per unit of time

Flow rate or throughput rate of a process

The number of flow units that go through the process in a period of time

Demand rate

The number of flow units that customers want per unit of time.

Input rate

The number of input flow units that are available per unit of time

To find flow rate, flow rate equals

Min{Input, Demand, Capacity}

Available supply equals

Min{Input, Capacity}

If demand < supply,

flow rate is demand-constrained. Flow rate = demand

If demand > supply,

flow rate is either input-constrained or capacity-constrained. If input-constrained, flow rate = input. If capacity-constrained, flow rate = process capacity.

Capacity-constrained

The case in which demand exceeds supply and the flow rate is equal to process capacity.

Demand-constrained

The case in which process capacity exceeds demand and thus the flow rate is equal to the demand rate.

Throughput

A synonym for flow rate, the number of flow units flowing through the process per unit of time.

Utilization (U)

The ratio between flow rate & capacity (either at the level of an individual resource or at the entire process). Measures efficiency

Cycle time

The time between completing two consecutive flow units

Lead time

The time between when an order is placed and when it is received.

Bottleneck

Resource with smallest capacity. Process capacity is equal to this. This has the highest utilization.

Implied utilization (IU)

The ratio between demand (workload) & capacity (either at the level of an individual resource or at the entire process). Measures demand pressure and helps manage capacity.

Worker-paced flow process

A process line in which each resource is free to work at its own pace

Machine-paced

Resources connected by conveyer belt. Must work at the same rate, regardless of capacities

Time through the empty system

The time it takes the first flow unit to flow through an empty process; that is, a process that has no inventory.

Idle time

Paid time not used for working (paid idling)

Total idle time

The amount of idle time per flow unit added up across all resources.

Average labor utilization

Average utilization across employees