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1.2.4 Henry Gantt: Gantt charts

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By Dr.M.MuthuKrishnan

 Developed by Henry L. Gantt

•A bar chart used for planning and scheduling.

•Each activity is shown by a horizontal bar indicating its start and completion time.

•Revolutionary Concept: Before Gantt, managers looked at quantities (e.g., "We need 500 engines"). Gantt visualized Time as a resource.

•Purpose: To show the dependency between tasks—what must be finished before something else can start.

•Shows activities vs time

•Displays start and finish dates of tasks

•Helps in monitoring progress

•Widely used in production and project management


IMPORTANCE OF GANTT CHART

  1. Visibility: It makes the invisible (time) visible.
  2. Control: It allows managers to see if they are "ahead" or "behind" schedule instantly.
  3. Legacy: It is the foundation of modern Project Management software (like Microsoft Project, Jira, Asan


Features of a Gantt Chart

  • Horizontal bars represent activities

  • Length of the bar indicates duration

  • Time scale shown at the top

  • Actual progress can be compared with planned schedule

  • Simple and easy to understand

Types of Gantt Charts 

  • Order Gantt Chart – Shows progress of individual jobs or orders
  • Machine Gantt Chart – Shows machine loading and utilization

Advantages

  • Simple visual representation
  • Easy to prepare and interpret
  • Helps in effective planning and control
  • Highlights delays clearly

Limitations 

  • Does not show inter-dependence of activities
  • Not suitable for complex projects
  • Difficult to update for large projects

Scenario: Building a House

  1. Foundation – Week 1

  2. Walls – Week 2

  3. Roof – Week 3

  4. Plumbing – Week 3

  5. Painting – Week 5

Sequential Tasks

  • Notice “Walls” cannot start until “Foundation” is finished (Weeks 1–2).

Parallel Tasks

  • Notice “Roof” and “Plumbing” happen at the same time (Week 3).

  • This is called concurrency.

The Goal

  • Reduce the total project time (Makespan) by identifying tasks that can be done simultaneously.



Gantt Chart – Industrial Example

Example: Manufacturing of a Gear Shaft in an Engineering Factory

A factory receives an order to manufacture 100 gear shafts. The production manager uses a Gantt chart to plan and control the operations.


OperationWeek 1Week 2Week 3Week 4
Raw material issue███
Turning operation███
Milling operation███
Heat treatment███
Grinding███
Inspection & packing███

Explanation

  • Sequential operations:
    Turning starts only after raw material issue is completed.
    Grinding starts only after heat treatment.

  • Parallel operations:
    Milling and heat treatment are scheduled simultaneously in Week 3, reducing total production time.

  • Monitoring progress:
    If turning is delayed, the manager can immediately identify the impact on later operations.

Benefits in Industry

  1. Better scheduling of machines and labor

  2. Easy monitoring of progress

  3. Identification of delays and bottlenecks

  4. Reduction in total production time

  5. Improved delivery performance



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