March 21st, 2012 Gantt Charts
Gantt charts are sometimes called as Gant Chart . The following discussion of Gantt charts originally appeared in Herrmann (2005)
It is important to note that Henry Gantt created many different types of charts. Moreover, Gantt designed his charts so that foremen or other supervisors could quickly know whether production was on schedule, ahead of schedule, or behind schedule. Modern project management software includes this critical function even now.
Henry Gantt (1903) describes two types of balances: the man's record, which shows what each worker should do and did do, and the daily balance of work, which shows the amount of work to be done and the amount that is done. Gantt gives an example with orders that will require many days to complete. The daily balance has rows for each day and columns for each part or each operation. At the top of each column is the amount needed. The amount entered in the appropriate cell is the number of parts done each day and the cumulative total for that part. Heavy horizontal lines indicate the starting date and the date that the order should be done. According to Gantt, the graphical daily balance is a method of scheduling and recording work. In this article, Gantt also describes the use of production cards for assigning work to each operator and recording how much was done each day.
In Work, Wages, and Profits (originally published in 1916), Henry Gantt explicitly discusses scheduling, especially in the job shop environment. He proposes giving to the foreman each day an order of work that is an ordered list of jobs to be done that day. Moreover, he discusses the need to coordinate activities to avoid interferences. However, he also warns that the most elegant schedules created by planning offices are useless if they are ignored, a situation that he observed.
In Organizing for Work (originally published in 1919), Gantt gives two principles for his charts: one, measure activities by the amount of time needed to complete them; two, the space on the chart can be used the represent the amount of the activity that should have been done in that time. Gantt shows a progress chart that indicates for each month of the year, using a thin horizontal line, the number of items produced during that month. In addition, a thick horizontal line indicates the number of items produced during the year. Each row in the chart corresponds to an order for parts from a specific contractor, and each row indicates the starting month and ending month of the deliveries. It is the closest thing to the Gantt charts typically used today in scheduling systems, though it is at a higher level than machine scheduling.
Gantt's machine record chart and man record chart are quite similar, though they show both the actual working time for each day and the cumulative working time for a week. Each row of the chart corresponds to an individual machine or operator. These charts do not indicate which tasks were to be done, however.
A novel method of displaying interdependencies of processes to increase visibility of production schedules was invented (and aplicated) in 1896 by Karol Adamiecki and described in "Przeglad Techniczny" No 17, 18, 19 and 20 of 1909. In 1931, Adamiecki published a number of articles popularizing this diagram, which he called the Harmonogram or Harmonograf. With minor modifications, this chart is now more commonly referred to as the Gantt Chart.
Using Gant Chart for project planning and scheduling
Gant Chart is a graphical representation of tasks as segments on a time scale. It helps plan and monitor project development or resource allocation. The left hand side of the Gant chart is a column with lists of tasks. The horizontal axis is a time scale, expressed either in absolute or relative time.
In a Gant chart, each task takes up one row. Dates run along the top in increments of days, weeks or months. Rows of bars in the Gant chart show the start and end dates of each task in the project. Tasks may run sequentially, in parallel or overlapping.
Use Gantt Chart at Project Scheduling Stage to
- Assess time characteristics to a project
- Show the task order
- Define resources involved
- Show links between scheduled tasks
Use Gantt Chart at Project Planning Stage to
- Monitor project completion
- Display the results of correctional activities
- Show links between scheduled tasks
History of a Gantt Chart
Gant chart was created by Henry L. Gant, an American engineer, in 1917. He developed the first Gant chart for planning of building ships in the First World War times. The chart proved to be such a powerful analytical instrument that it had not undergone any changes for almost 100 years. It was only in 90s of the last century when link lines between tasks were added to the Gant chart.