**Process selection and Facility layout/ Line Balancing**

**Question: How many operations can the second workstation do in the course of the day? The third? The fourth? The fifth?**

** **

Let each station represent a machine that does one step of a five-step operation to make a widget.

According to the diagram, the first workstation takes 0.1 minutes to complete the first step of the operation.

In this operation, the worker is employed for 8 hours but loses 1 hour through lunch and planned breaks thus working for 7 hours or 420 minutes.

One operation takes 0.1 minutes, therefore in 420 minutes can do?

Output rate = Operating rate per day = 420 = 4200 operations in a day

Cycle time 0.1

The second workstation takes 0.7 minutes, therefore in the course of the day, which is 420 minutes, it can do?

420 = 600 operations in a day

0.7

The third workstation takes 1.0 minutes, therefore in the course of the day, which is 420 minutes it can do?

420 = 420 operations in a day

1.0

The fourth workstation takes 0.5 minutes, therefore in the course of the day, which is 420 minutes it can do?

420 = 840 operations in a day

0.5

The fifth workstation takes 0.2 minutes, therefore in the course of the day, which is 420 minutes it can do?

420 = 2100 operations in a day

0.2

**Question: How many worker-machines do you need for the other workstations?**

Input of a workstation = output of the previous workstation

Output of system is determined by worker-machine with the lowest output, which in this case is the third worker-machine with an output of 420 operations a day.

Therefore, the first workstation is essentially 90 percent idle, that is:

420 * 100 = 10 % working

4200

For the first workstation, you would need only one worker-machine because its output is 4200 operations a day, which is above 800 operations a day.

For the second workstation, you would need two worker-machines because its output is 600 operations a day, which is below 800 operations a day.

For the fourth workstation, you would need only one worker-machine because its output is 840 operations a day, which is above 800 operations a day.

For the fifth workstation, you would need only one worker-machine because its output is 2100 operations a day, which is above 800 operations a day.

**Question: How many worker-machines would you need if the system output has to be 1,200?**

If the system output has to be 1,200 operations a day:

For the first workstation, you would need only one worker-machine because its output is 4200 operations a day, which is above 1200 operations a day.

For the second workstation, you would need two worker-machines because its output is 600 operations a day, which is below 1200 operations a day, and two would make it have an output of exactly 1200.

For the third workstation, you would need three worker-machines because its output is 420 operations a day, which is below 1200 operations a day, and three would make it have an output of just over 1200 (1260 to be exact).

For the fourth workstation, you would need two worker-machines because its output is 840 operations a day, which is below 1200 operations a day.

For the fifth workstation, you would need only one worker-machine because its output is 2100 operations a day, which is above 1200 operations a day.

**Reference**

Stevenson, W. J. (2009). *Operations Management*. New York, NY: McGraw-Hill Irwin