Gantt chart

This tool has two objectives: to plan and communicate on the established schedule and the choice it imposes.

The chart can:

  • determine the dates of completion of a project.
  • identify existing margins on certain tasks.
  • see at a glance the delay or progress of the work.

The Gantt chart does not solve all the problems, especially if one has to plan competing fabrications for the use of certain resources of the company.

Method

The method consists of placing the tasks to be performed in the order of priority and taking into account the resources still available. The most common rules are:

  • priority to the realization of the fabrications whose delivery date is closest.
  • priority to the first arrival order.
  • priority to manufacturing with the shortest total duration.
  • priority to manufacturing that uses at least one critical resource.
  • priority to manufacturing who have the minimum margin.

This chart (or planning) has numerous advantages:

  • simple reading and accessible to all.
  • tracking can be done easily at the project’s progress by comparing planned dates and actual dates.
  • the start and end dates of each task are read directly on the time scale.
  • it allows assigning resources to tasks to establish the load plan.
The diagram is represented on two axes: time and allocation; and contains two types of elements: bars representing a task as well as its execution time, and arrows representing the links of anteriority.

The Gantt chart allows to analyze all the relations that exist between the activities, to release the sequences of activities, to identify the critical path (without margin of maneuver) and the dates of beginning and end (at the earliest and at the latest) of each activity. The Gantt chart makes it possible to choose the dates that will be effectively selected to carry out the activities and, possibly, to show the relations between the activities and thus the incidences in term of delay.

Drawing a Gantt chart must be done in three steps:

  1. To identify and to structure the task list stating the antecedents or other constraints.
  2. To create the task diagram (time criterion). For each of them, it is necessary to determine the duration as well as the margins of maneuver.
  3. To complete the diagram with the other criteria.

Example

gantt1

Establishment of the time diagram:

gantt2

Added criteria (here the numbers of staff to accomplish a task:

gantt3.png

 

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