Gantt chart and Scheduling techniques

Abstract

The scheduling techniques that are going to be explained in this article are Gantt and CPM - hereby Network Diagram - have they works - have to use them in practice - have they are connected and supplement each other
Goal: to simplify the different scheduling techniques, how to use them and connecting them to each other

Scheduling

A plan can only show the practicability of accomplishing its objectives when the actions and activities in the plan, are put together in a schedule that illustrates when each action or activity will be carried out.

Today there is many different methods and approaches to scheduling. It can either be by computer-based planning tools or done manually .
Tools like Gantt chart and Critical Path Method (CPM) are tools often used in the planning process of a project.

Gantt chart

What is a Gantt chart?

Gantt chart is the oldest form of a formal scheduling tool. The Gantt chart was developed in the 1910s by Henry Gantt, and today used widely as a scheduling tool in projects.

Definition

"A graphic display of schedule-related information. In the typical bar chart, schedule activities or work breakdown structure components are listed down the left side of the chart, dates are shown across the top, and activity durations are shown as date-placed horizontal bars."

When and why use Gantt chart?

Assess how long a plan should take, lay out the order in which tasks need to bed carried out Manage the dependencies between tasks See what should have been achieved at a certain point in the time See how remedial action may bring the plan back on course

How to create a Gantt chart?

Developing a Gantt chart takes some steps. In the scoping phase determines the level of details and the activities identifies in the project. There are many ways to create a Gantt chart and in the end, it depends on the project and the working style. In the table below are some general steps to developing a Gantt chart described.

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How to create a Gantt chart. Received from: [1]

Creating a Gantt chart step by step

Step 1 - Creating the axes: Create a sheet with vertical and horizontal axes. The vertical axis represents the activities, and the horizontal axis represents the timescale. To make the Gantt chart more clear and get and an idea of the total time that needs for each activity, adding the calendar time in timescale is a good idea, see figure 1. Step 2 - Creating the bars: Create bars representing each activity. The length of the bars should be proportional to the duration time. If there are multiple activities it is a good idea to create a summary or hammock activity, see figure 1. By using hammock activities the project can be summarized in fewer activities, which gives a better overview of the project, but in the same time, you can still go into the level of detail with the activity group in the hammock. The bar of the hammock activity begins when the earliest activity in the group starts and end when the latest activity in the group ends, see figure 1. Figure 1: How to create a Gantt chart. Reproduced from: [4] Step 3 - Revise til Gantt chart: Have a look at the Gantt chart again. Are all the important activities there and are they logically placed in the chart? What about the timescale? Are the durations reasonable? Make the necessary changes in the chart.

Critical path method (CPM)

What is the Critical path method

Develop in the 1950s by Morgan R. Walker and James E. Kelley. CPM is very similar to PERT(Program evaluation and review techniques), but represent information in a different way.

Definition

"A schedule network analysis technique used to determine the amount of scheduling flexibility (the amount of float) on various logical network paths in the project schedule network, and to determine the minimum total project duration. Early start and finish dates are calculated by means of a forward pass, using a specified start date. Late start and finish dates are calculated by means of a backward pass, starting from a specified completion date, which sometimes is the project early finish date determined during the forward pass calculation.”

How to create the Critical path method

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Creating a Gantt chart step by step
Step 1 - Specify each activity: Step 2 - Sequence the activities: Step 3 - Creating a Network Diagram: Dummi activities caption Step 4 - Estimate activity durations: Step 5 - Identyfy the critical path: Step 6 - Use and update:

Constructing a Network Diagram

Checklist when creating a Network Diagram
1. 2.

The Importance of the Gantt Chart and the Critical Path for Project Management

Pros and cons

	colspan="6" style="text-align: left; color: #699EB4;" Pros	colspan="6" style="text-align: left; color: #699EB4;" Cons The lack of a timeframe makes it harder to show the development status.
Gantt	An easy way to schedule all tasks and track them in the project progress next to the deadline(s) Simple: everyone can read it and make it. Easy to read from all the stakeholders. It could be used to show fragments/portions of big projects previously elaborated with PERT. Powerful visual communication tool. Short time to make. Useful tool to see the development of the project. Useful too to reallocate resources among activities.	It doesn't show activities' dependencies It cannot be used for project with large number of activities and dependencies. It need constant updates (changes to the schedule require a redrawing of the chart). It doesn't highlight the activities with the highest risk of failure or delay.
CPM	Identifying critical activities is fundamental to be aware of possible delays. TIME=MONEY. This tool is really useful for planners to forecast the length of the project taking into account that critical activities could delay it. It makes dependencies visible.	For large projects it's difficult to handle the dependencies and calculating the slack. In this case it is possible to use software that calculate everything. It does not account for resource and resource allocation.