Make your own free website on


Home Up





Back to Example of Input-Output Control

Table of Content

Forward to Gantt Chart

7.    Comment on the Solution of the Example and Input-output 

        Comment on the solution for the tutorial of the Input-output Control:

The actual output(270 hours) is substantially less than planned.

Therefore, neither the input plann or the output plan is being achieved.

Indeed, the backlog of work centre has actually increased by 5 hours by week 4.

This increases work-in -progress inventory, complicating the scheduling task and indicating the need for manager action.

        Comment on the Input-output Control:

            The Input-output Control Sheet like Figure 2 can be used to see whether actual               results are in reasonable agreement with the plan and to show the impact of a plan on the               queue at work centre. The relationship between the actual flow to a centre and the actual               flow out determines the growth or shrinkage of the queue.

            paw_pr.gif (128 bytes)    The numbers in the "cumulative deviation" and "cumulative deviation" rows are
                      computed by subtracting the planned amount for a week and adding the result to the
                      cumulative deviation for prior week.
            paw_pr.gif (128 bytes)    The actual backlog numbers refer to the backlog at the end of a week and are
                      computed by starting with the prior weeks' actual backlog and then adding the actual
                      input during the week and subtracting the actual output during the week.

Input-output control might be maintained to monitor tha gateway or starting work
            centres, because the output of these centres determines the input to subsequent centres and             the entire factory. If the capacity of some downstream work centre(a bottleneck) is less
            than that of the gateway work centre, the input at the gateway can be geared to the output
            at the bottleneck to prevent excessive WIP. Capacity at any work centre should be
            adjusted, if practicable, to keep queues from becoming large, because coordinated plans
            can be wreaked by unplanned delays at any work centre through whcihc one part of an
            assembly passes. Effective input-output control should keep the average actual lead time
            equal to the lead time offsets used when the schedules were made.

Gantt Chart   Gantt Chart

Back to top   Back To Top

[Input-output Control]     [Example for Input-output Control]   
[Comment on Solution and Input-output Control]