Assembly Line Balancing

1. Assembly Line Balancing Introduction to Industrial Engineering

2. The Line Balancing Problem • The problem is to arrange the individual processing and assembly tasks at the workstations so that the total time required at each workstation is approximately the same. • Nearly impossible to reach perfect balance

3. Things to consider • Sequence of tasks is restricted, there is a required order • Called precedence constraints • There is a production rate needed, i.e. how many products needed per time period • Design the line to meet demand and within constraints

4. Terminology and Definitions • Minimum Work Element • Total Work Content • Workstation Process time • Cycle Time • Precedence Constraints • Balance Delay

5. Minimum Work Element • Dividing the job into tasks of a rational and smallest size • Example: Drill a hole, can’t be divided • Symbol – Time for element j: • is a constant

6. Total Work Content • Aggregate of work elements

7. Workstation Process time • The amount of time for an individual workstation, after individual tasks have been combined into stations • Sum of task times = sum of workstation times

8. Cycle time • Time between parts coming off the line • Ideally, the production rate, but may need to be adjusted for efficiency and down time • Established by the bottleneck station, that is station with largest time

9. Precedence Constraints • Generally given, determined by the required order of operations • Draw in a network style for understanding • Cannot violate these, an element must be complete before the next one is started

10. Balance Delay • Measure of line inefficiency due to imbalances in station times

11. Method – Largest Candidate Rule • List elements in descending order of T • Assign elements to first station, from top to bottom of list, minding constraints, and not causing sum to exceed cycle time • Continue assigning elements to stations where each station < cycle time, largest assigned first, until all assigned • EXAMPLE