Job Shop Optimization

Generic Situation:

Small job shop owners are continuously confronted with scheduling problems. The more complicated the process, the greater the need to know exactly how to schedule a series of jobs.

Example:

Horwath Manufacturing runs a job shop comprised of five different machine groups. Each group consists of a specified number of machines of a given kind as listed below:



Group
Number
Number of
Machines
13
22
34
43
MACHINE BREAKDOWN


Within any group the machines are identical to each other. It does not matter which machine in a group is used to carry out a unit of work-in-progress.

Three types of products (or jobs) are produced at the job shop - designated Type A, Type B, and Type C. Each job type requires that steps be performed at specified machines in a specified sequence. The total number and kind of machine groups each job type must visit, and the corresponding visitation sequence are shown below:


Job TypeNumber of
Machines to Visit
Visitation
Sequence
Expected
Step Time
143.50
1.60
2.85
5.50
2341.10
1.80
3.75
3521.2
5.25
1.70
4.90
31.00
VISITATION AND EXPECTED STEP TIMES


For example, job Type 1 must visit a total of four machine groups in this order: Group 3, then Group 2, then finally Group 5. Mr. Horwath has settled on his present system of production scheduling because it is profitable and restructuring the production flow to optimize profit seems to be an impossibility due to the large number of possible combinations of how jobs arriving can be scheduled.

Profit Maximizing Solution:

Analysis of the present setup determined that if only one machine were added to Group 2, the overall number of completed jobs would rise by almost 13%.