How can you optimize production processes with line balancing?

1 What is cycle time and why is it important?

Cycle time is the time it takes to complete one unit of output from start to finish. It is a measure of the efficiency and productivity of your production process. The shorter the cycle time, the more units you can produce in a given time period. However, if the cycle time is too short, it may cause quality issues, stress, and errors. Therefore, you need to balance the cycle time with the quality standards and customer demand.

2 How to calculate the theoretical minimum number of workstations?

One of the first steps in line balancing is to determine the theoretical minimum number of workstations (TM) that you need to achieve the desired cycle time. You can use this formula:

TM = sum of task times / cycle time

The sum of task times is the total time required to perform all the tasks in the production process. The cycle time is the maximum time allowed for each unit of output. For example, if you have 10 tasks with a total time of 120 minutes and a cycle time of 15 minutes, then TM = 120 / 15 = 8.

3 How to assign tasks to workstations using the longest task time rule?

Once you have calculated the TM, you can start assigning tasks to workstations using a simple heuristic rule called the longest task time rule. This rule states that you should assign the task with the longest time to the first available workstation, as long as it does not exceed the cycle time. Then, you should repeat this process for the remaining tasks and workstations. For example, if you have these tasks and times:

Task A: 20 minutes

Task B: 18 minutes

Task C: 15 minutes

Task D: 12 minutes

Task E: 10 minutes

Task F: 9 minutes

Task G: 6 minutes

Task H: 5 minutes

And a cycle time of 25 minutes, then you can assign the tasks as follows:

Workstation 1: Task A (20 minutes)

Workstation 2: Task B (18 minutes)

Workstation 3: Task C and Task D (15 + 12 = 27 minutes)

Workstation 4: Task E and Task F (10 + 9 = 19 minutes)

Workstation 5: Task G and Task H (6 + 5 = 11 minutes)

4 How to evaluate the line balance and efficiency?

After assigning tasks to workstations, you can evaluate the line balance and efficiency using two indicators: the balance delay and the line efficiency. The balance delay is the percentage of idle time in the production line. It is calculated by subtracting the actual number of workstations from the TM and dividing by the TM. The line efficiency is the percentage of productive time in the production line. It is calculated by dividing the sum of task times by the product of the cycle time and the actual number of workstations. For example, using the previous example, the balance delay and the line efficiency are:

Balance delay = (TM - actual number of workstations) / TM = (8 - 5) / 8 = 0.375 or 37.5%

Line efficiency = sum of task times / (cycle time x actual number of workstations) = 120 / (25 x 5) = 0.96 or 96%

The lower the balance delay and the higher the line efficiency, the better the line balancing.

5 How to improve the line balance and efficiency?

Line balancing is a powerful tool that can help you optimize your production processes and achieve higher levels of efficiency, quality, and customer satisfaction. To improve line balance and efficiency, you can reduce the cycle time by increasing the speed, quality, and reliability of the production process. Additionally, reducing the task times by simplifying, standardizing, or eliminating unnecessary tasks can be beneficial. Reassigning tasks to workstations using different heuristic rules is also a viable option. Furthermore, adding parallel workstations or workers to perform the same or similar tasks and implementing flexible workstations or workers that can perform multiple tasks can be beneficial. Finally, applying lean manufacturing principles such as eliminating waste, reducing variation, and improving flow can help improve line balance and efficiency.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?