5. Creating a Gantt Chart

Transcription

1 5. Creating a Gantt Chart Whilst the network diagram is a useful way to describe how tasks are linked to each other, the Gantt chart is used to display the schedule of a project. The Gantt chart is the most common report within Microsoft Project (and indeed all project management systems), yet it is often misused. The discussions below describe how a Gantt chart can be created and illustrate the types of information that it can readily provide. The purpose of a Gantt chart The Gantt chart takes its rather strange name from its inventor; Henry Gantt. Mr. Gantt was an American industrial engineer who created a chart to, in its most basic form, describe what happens when. A simple Gantt chart can be created on paper, or by using software. The examples below were created using Microsoft Excel. A fundamental component of a Gantt chart is its timescale. This timescale should cover the entire duration of the project; from the project start date to the project finish date. The timescale between these dates should then be broken down into equal increments. A Gantt timescale of 30 days: Once the chart's timescale has been created, tasks can be added. These tasks should be the complete list of subtasks as described within the network diagram, or from the lowest level of the outline (Work Breakdown Structure). Tasks and a timescale: The chart's timescale can be in days, weeks, months, and so on. It must be linear and in equal increments; for example 1 increment per day OR one increment per week. Copyright Inixindo,

2 Tasks are normally sorted into a sequence based upon their early start order for hand drawn Gantt charts. Microsoft Project generated Gantt charts will usually display summary tasks, normal tasks and milestones. The normal tasks and the milestones are shown as subtasks beneath their respective summaries. Displaying a task's schedule Once the chart has been created and the task's added, task bars can be drawn on the chart. Draw a bar from a task's earliest start to its earliest finish: The bar is scheduled from the end of day 0 (beginning of day 1) to the end of day 5. Microsoft Project draws a task bar from a scheduled start date (and time) to a scheduled finish date (and time). When a task has no constraints against it, or it has not been delayed by leveling; it's early start and scheduled start will be identical. Displaying succeeding tasks Drawing task bars for successive tasks is simply a matter of taking the early start and early finish for each of the tasks, and creating the bars between these dates: For the immediate successors to 'Design structure': For all the remaining tasks within the project: Copyright Inixindo,

3 For simplicity and consistency, follow predecessor / successor paths. This should ensure that the correct bar is drawn on the correct row and from / to the correct dates. Displaying link lines between tasks Within Microsoft Project, the default layout for the Gantt chart depicts link lines. These lines illustrate the various dependencies between the tasks. A hand-drawn Gantt chart can also have these link lines added: Link lines depict HOW the tasks relate to each other. When a Gantt chart has a lot of links between tasks (especially cross-project links), the chart can become very busy with detail. This in turn can lead to confusion. When producing a Gantt chart for a client or a sponsor, decide if it is appropriate to tell them how tasks relate. They probably only need to know when tasks are scheduled to occur. Displaying free and total slack for tasks Once the task bars have been drawn, slack bars can be added to the chart. These bars are drawn to the right of the bars for non-critical tasks. Total slack is drawn from the task's early finish date to its late finish date (depicted below as a thin purple line): Copyright Inixindo,

4 If free slack is known (in addition to total slack), it can also be added to the chart (depicted below as a thin green line): o o Create exercises only possesses total slack. If it is delayed for any reason, its successor Test exercises will be subsequently delayed. This in turn would reduce the slack available to the Test exercises task. Test exercises possesses free slack as well as total slack. If it were delayed for any reason, it wouldn't affect ANY other task until its slack was used up and it became a critical task. If any tasks have to be delayed, choose ones with the greatest amount of free slack. Aim (where possible) to have as much free slack as possible on tasks that are not in your direct control. Emphasizing the critical path It is useful if a project's critical path can be emphasized on a Gantt chart. This is normally a process of selecting the critical tasks (that possess no slack) and changing their appearance. The Gantt Chart Wizard within Microsoft Project displays critical tasks in red and non-critical tasks in blue, whilst retaining an identical shading pattern for the bars (by default). Copyright Inixindo,

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