As many have said above Gantt charts are one way of organizing the timetable of mini projects that comprise the overall product. My experience in industry pertaining to Gantt charts involves working with the manufacturing supervisors to come up with a feasible time table for going from NPD to NPI with the diagnostic instrument. Because of the huge financial ramifications involved, it was important to know how quickly these instruments can be built, aligned, and pass qualification testing, and be ready for international shipment. The chart also had to account for scale up of the manufacturing facility/ potential instrument output. This was in addition to planning in enough slack time to be able to overcome unexpected manufacturing obstacles while still providing management with a reasonable, attractive timetable for shipment. Lastly, as bb254 mentioned above, the Gantt chart was made highly visible to essential personal on site so that all goals/ milestones were clearly understood and transparent. Without doing so, accountability as well as a feeling of contribution from each department could be lost and add to time waste.