Question

2. Consider the following batch flow process consisting of three process steps performed by three machines: Step 1 Step 3 Step 2 Processing time 1 minute/part Processing time 1.5 minute/part Processing time 2 minute/part Setup time No Setup No Setup 20 minutes Work is processed in batch at each step. Before a batch is processed at step 1, the machine has to be set up. During There are no inventory buffers between steps. a setup, the machine is unable to process any product Find the best batch size that achieves a flow rate of 24 parts per hour

Answer 1

Flow rate = 24 parts per hour = 24/60 parts per minute = 0.40 parts per minute

Capacity of step-2 = 60/2 = 30 parts per minute
Capacity of step-3 = 60/1.5 = 40 parts per minute

So, step-2 and 3 are non-bottlenecks in producing 24 parts per hour flow rate.

For step-1:

Use the following formula to compute the recommended batch size:

Flow rate xSetup time Recommended batch size 1-Flow rate x Processing time

So,

Recommended batch size = 0.4*20 / (1 - 0.4*1) = 13.33. So, the batch size should at least be 14 to produce a flow rate of 24 parts per hour. More than this batch size will cause additional inventory.