Question

1. A batch of material must visit two work stations in series to be converted into finished product. Each batch makes 100 units. Setup time at each work station is 30 minutes. Variable processing time is 3 minutes/unit and 5 minutes/unit in station 1 and station 2 respectively. After completing the operation the batch has to wait on average of 1 hour for the material handler to move it to the next machine. Assuming there is no time lost in waiting for the machines, find the time it takes for a batch of material to go through the system. Re-compute the completion time of a batch of 100 parts, if the batch size is reduced to 50. So now a batch of 50 is moved from machine 1 to machine2 as soon as it ready. Comment on the impact of reduction in batch size on completion time of 100 parts. Show that we can move parts through the system faster as we move them in smaller batches. What is the minimum time you can achieve to complete a batch of 100 parts? Make necessary assumptions.

Answer 1

Part (a)

The time required to complete 100 batch process:

Set up time 30 mins.

Station 1 time (100 units x 3 mins/unit) = 300 mins.

Station 2 time (100 units x 5 mins/unit) = 500 mins.

Time for transfer to next machine =   60 mins.

Total time for the batch = 890 mins.

Part (b)

Time required to process a 50 units batch :

Setup Time ( 30 minutes x 2 times) = 60 mins.

Starion 1 Time (100 units x 3 mins/unit) = 300 mins.

Station 2 time( 100 units x 5 mins./unit) =   500 mins.

Total time for the batch = 860 mins.

Note:

1) As the products are processed in the batch of 50 units so, the set up will be required (100units/50units) = 2 times

2) The products are transferred from one machine to another without any time lag. Thus no time will be alloted for the transfer of products from one machine to the next machine.

Part (C)

The Company should produce the products in 50 units batch. Cause it takes lesser time as compared to the 100 units batch. The 50 units batch is taking 860 minutes whereas the 100 batch is taking 890 minutes. Clearly there is a saving of 30 minutes per 100 units produced. The reason behind this is while producing in 50 units batch there is a saving of 60 minutes in terms of prompt transfer of products to the next machine. On the outher hand in 50 units batchs the machine setup will be 2 times which results in 30 minutes extra time for the production. So, the net saving of time is (60-30) = 30 minutes. Thus 50 units batch are taking 30 minutes lesser time than 69 units batch.

Part (d)

If we further reduce the number of units per batch from 50 units per batch then it will take more time to complete 100 numbers of products.

Let's take an example. If we further reduce the number of products per batch to 25 units from 50 units then it will take 4 times machine set up. Which will increase the time of production by another 60 minutes.

Setup time:

25 units batch = (30 x 4) = 120 minutes

Less: 50 units batch = (30 x 2) =  60 minutes

Increase in time = 60 minutes.

So, the minimum time to produce 100 number of units is 860 minutes / 7 hrs and 20 minutes under 50units batch production. If we further reduce the number of products per batch then it will increase the time to produce 100 number of units.