Development of a new product according to the design process is always limited by the time available for the entire process. Thus for most engineering problems scheduling is an essential part of design. With a careful planning, deadlines are met and the customer satisfaction increases. Although many techniques exist for scheduling, here one of the most common methods will be briefly discuss. The method makes use of a Gantt Chart.
Table 1.2: Weighted Method
A B DATUM
Criteria Weight (%) Prius MR2 Spyder Corolla
1. Fuel Economy 20 2 −1 0
2. Base Price 8 −1 −2 0
3. People Capacity 5 0 −2 0
4. Styling 6 1 2 0
5. Safety (Crash Testing) 8 0 0 0
6. Fit & Finish (Quality) 5 0 1 0
7. Comfort 7 2 −2 0
8. Suspension Type 2 0 2 0
9. Power to Weight Ratio 3 −2 2 0
10. Powertrain 3 1 2 0
11. Performance 4 −1 2 0
12. Braking Distance 2 1 2 0
13. Turning Circle 1 2 1 0
14. Storage Capacity 3 2 −1 0
15. Standard Features 5 2 0 0
16. Availability of spare parts 3 −2 1 0
17. Warranty 15 0 0 0
Total 100 7 6 0
Total Positive — 13 15 0
Total Negative — −6 −9 0
Weighted Total — 59 −17 0
History
Henry Laurence Gantt (1861–1919) was a mechanical engineer, management consultant and industry advisor. Henry Laurence Gantt developed Gantt charts in the second decade of the 20th century. Gantt charts were used as a visual tool to show scheduled and actual progress of projects. Accepted as a commonplace project management tool today, it was an innovation of world-wide importance in the 1920s. Gantt charts were used on large construction projects like the Hoover Dam started in 1931 and the interstate highway network started in 1956.
Overview
A Gantt chart is a graphical representation of the duration of a project or tasks against the progression of time.
A project is a set of activities which ends with specific accomplishment and which has (1) Non-routine tasks, (2) Distinct start/finish dates, and (3) Resource constraints (time/money/people/equipment).
Tasks are activities which must be completed to acheive project goal. Break the project into tasks and subtasks.
Tasks have start and end points, are short relative to the project and are significant (not going to library, but rather, search literature). Use verb-noun form for naming tasks, e.g. create drawings or build prototype. Use action verbs such as create, define and gather rather than will be made. Each task has a duration. Very difficult to estimate durations accurately. Doubling your best guess usually works well.
early. Name by noun-verb form, e.g. report due, parts ordered, prototype complete.
Your plan will evolve so be flexible and update on a regular basis. It also helps to identify risk areas for project, for example, things you don’t know how to do but will have to learn. These are risky because you may not have a good sense for how long the task will take. Or, you may not know how long it will take to receive components you purchased for a project.
Basics
Gantt charts are a project planning tool that can be used to represent the timing of tasks required to complete a project. Because Gantt charts are simple to understand and easy to construct, they are used by most project managers for all but the most complex projects. Gantt charts are used for planning and monitoring progress.
The reason to use Gantt charts as a useful tools for planning and scheduling projects is that they allow to assess how long a project should take, lay out the order in which tasks need to be carried out, help manage the dependencies between tasks, and determine the resources needed. The reason to use Gantt charts when a project is under way is that they monitor progress, can immediately see what should have been achieved at a point in time, help manage the dependencies between tasks, and allow to see how remedial action may bring the project back on course.
In a Gantt chart, each task takes up one row. Dates run along the top in increments of days, weeks or months, depending on the total length of the project. The expected time for each task is represented by a horizontal bar whose left end marks the expected beginning of the task and whose right end marks the expected completion date.
Tasks may run sequentially, in parallel or overlapping. Some Gantt charts include two extra columns between the task and the dates: the first column holds the duration of the activity and the second one which team members are responsible for such task. MS Excel is a good tool to create Gantt charts.
The first Gantt chart represents the planning of the events. A second one helps to compare the progress with the scheduled timing. Thus as the project progresses, the chart is updated by filling in the bars to a length proportional to the fraction of work that has been accomplished on the task. This way, one can get a quick reading of project progress by drawing a vertical line through the chart at the current date. Completed tasks lie to the left of the line and are completely filled in. Current tasks cross the line and are behind schedule if their filled-in section is to the left of the line and ahead of schedule if the filled-in section stops to the right of the line. Future tasks lie completely to the right of the line.
In constructing a Gantt chart, keep the tasks to a manageable number (no more than 15 or 20) so that the chart fits on a single page. More complex projects may require subordinate charts which detail the timing of all the subtasks which make up one of the main tasks. For team projects, it often helps to have an additional column containing numbers or initials which identify who on the team is responsible for the task.
Often the project has important events which you would like to appear on the project timeline, but which are not tasks. For example, you may wish to highlight when a prototype is complete or the date of a design review.
You enter these on a Gantt chart as milestone events and mark them with a special symbol, often an upside-down triangle.
How to build a Gantt chart?
Basically, there are four steps in preparing a Gantt chart:
1. List all events or milestones in an ordered list, whenever possible.
2. Estimate the time required to establish each event (remember it is an estimate).
3. List the starting time and end time for each event.
4. Represent the information in a bar chart.
A Gantt chart is a matrix and it is:
• constructed with a horizontal axis representing the total time span of the project, broken down into increments (days, weeks, or months)
• constructed with a vertical axis representing the tasks that make up the project.
• constructed with a graph area which contains horizontal bars for each task connecting the period start and period ending symbols.
• has variants such as:
– Milestones: important checkpoints or interim goals for a project
– Resources: for team projects, it often helps to have an additional column containing numbers or initials which identify who on the team is responsible for the task
– Status: the projects progress, the chart is updated by filling in the task’s bar to a length proportional to the amount of work that has been finished
– Dependencies: an essential concept that some activities are dependent on other activities being completed first
It is greatly used in all project management groups and here is an example on how to use it. Figure 1.4(a) shows the planning of a task that starts in the August and ends in December.
For task 1 mark the time period when you will be working on it. Only shade that time interval. For instance if task one will begin at the end of August and conclude by the third week of September then represent this using a bar, as shown in Fig. 1.4(b).
In constructing a Gantt chart, keep the tasks to a manageable number (no more than 15 or 20) so that the chart fits on a single page. More complex projects may require subordinate charts which detail the timing of all the subtasks which make up one of the main tasks. For team projects, it often helps to have an additional column containing numbers or initials which identify who on the team is responsible for the task.
Often the project has important events which you would like to appear on the project timeline, but which are not tasks. For example, you may wish to highlight when a prototype is complete or the date of a design review.
You enter these on a Gantt chart as milestone events and mark them with a special symbol, often an upside-down triangle.