Batch Process Example

Quiz 1: Solution

Consider a batch production process with three processes A, B and C as shown below

C

C

B

B

A

A

The setup times and run times for the three processes are given below

| Setup Time (mins) | Run Time (mins)/unit |

A | 40 | 4 |

B | 80 | 2 |

C | 10 | 4.5 |

1) Identify the bottleneck process when the batch sizes are as follows ([1+1] x 5 marks)

a) 1 unit per batch

b) 5 units per batch

c) 10 units per batch

d) 30 units per batch

e) 100 units per batch

  | Time taken by |

Batch Size | A | B | C |

1 | 44 | 82 | 14.5 |

5 | 60 | 90 | 32.5 |

10 | 80 | 100 | 55 |

30 | 160 | 140 | 145 |

100 | 440 | 280 | 460 |

2) For each case, also calculate the number of batches processed and the number of units processed by the bottleneck process in a work day (Assume a work day of 8 hours).

Fill in the following table ([1.5+1.5] x 5 marks)

Batch size | Bottleneck process | Number of batches processed | Number of units processed |

1 | B | 5.85 | 5.85 |

5 | B | 5.33 | 26.67 |

10 | B | 4.80 | 48 |

30 | A | 3 | 90 |

100 | C | 1.04 | 104.35 |

3) Does the bottleneck process remain the same for the 5 cases? If not, at what batch size(s) does the bottleneck shift from one process to another? (5 marks)

As seen from the above table, bottleneck process shifts from B to A sometime between batch sizes of 10 and 30. To find the shifting point, we equate the two.

80 + 2n = 40 + 4n => n = 20

At n = 20, both B and A take the same amount of time. For batch sizes greater than 20 (21 and above), A becomes the bottleneck operation.

Bottleneck process shifts from A to C sometime between batch sizes of 30 and 100. To find the shifting point, we equate the two.

10 + 4.5n = 40 + 4n => n = 60

At n = 60, both A and C take the same amount of time. For batch sizes greater than 60 (61 and above), C becomes...