Job Management System - LogicJMS

Operations managers are interested in process aspects such as cost, quality, flexibility, and speed. Some of the process performance measures that communicate these aspects include:

• Process capacity - The capacity of the process is its maximum output rate, measured in units produced per unit of time. The capacity of a series of tasks is determined by the lowest capacity task in the string. The capacity of parallel strings of tasks is the sum of the capacities of the two strings, except for cases in which the two strings have different outputs that are combined. In such cases, the capacity of the two parallel strings of tasks is that of the lowest capacity parallel string.

• Capacity utilization - the percentage of the process capacity that actually is being used.

• Throughput rate (also known as flow rate ) - the average rate at which units flow past a specific point in the process. The maximum throughput rate is the process capacity.

• Flow time (also known as throughput time or lead time) - the average time that a unit requires to flow through the process from the entry point to the exit point. The flow time is the length of the longest path through the process. Flow time includes both processing time and any time the unit spends between steps.

• Cycle time - the time between successive units as they are output from the process. Cycle time for the process is equal to the inverse of the throughput rate. Cycle time can be thought of as the time required for a task to repeat itself. Each series task in a process must have a cycle time less than or equal to the cycle time for the process. Put another way, the cycle time of the process is equal to the longest task cycle time. The process is said to be in balance if the cycle times are equal for each activity in the process. Such balance rarely is achieved.

• Process time - the average time that a unit is worked on. Process time is flow time less idle time.

• Idle time - time when no activity is being performed, for example, when an activity is waiting for work to arrive from the previous activity. The term can be used to describe both machine idle time and worker idle time.

• Work In process - the amount of inventory in the process.

• Set-up time - the time required to prepare the equipment to perform an activity on a batch of units. Set-up time usually does not depend strongly on the batch size and therefore can be reduced on a per unit basis by increasing the batch size.

• Direct labor content - the amount of labor (in units of time) actually contained in the product. Excludes idle time when workers are not working directly on the product. Also excludes time spent maintaining machines, transporting materials, etc.

• Direct labor utilization - the fraction of labor capacity that actually is utilized as direct labor.