Chapter 16: Scheduling

Scheduling

pertains to establishing the timing of organizations special resources

1. equipment

2. facilities

3. human activities

Scheduling pertains to…

1. cost savings

2. increases productivity

3. other benefits

Effective scheduling can yield…

Loading Approches

1. infinite loading

2. finite loading

Infinite Loading

giving out tasks without checking if the person has time to do them.

Infinite Loading Example

A print shop schedules 20 print jobs for one day on a printer that can only handle 10 jobs per day. They don’t check the printer’s capacity—they just assign all the jobs anyway.

Finite Loading

means scheduling only the amount of work that fits into the time and space available.

Finite Loading Example

A bakery gets 10 cake orders, but the oven can only bake 5 cakes per day. So, the bakery schedules 5 cakes today and 5 cakes tomorrow, based on how much the oven can handle each day.

Scheduling Approaches

1. Forward scheduling

2. Backward scheduling

Forward Scheduling

starting work right away and planning everything after that based on the order of tasks and used when the issue is: “how long will it take to complete this job?”

Forward Scheduling Example

A construction company begins building a house as soon as the materials arrive, then schedules all the other tasks (like plumbing and painting) to follow as soon as the previous task is done.

Backward Scheduling

means working backward from the deadline to figure out the best time to start each task.

Backward Scheduling Example

A company has a product launch in two weeks. They plan all the tasks (like production, packaging, and shipping) by working backward from the launch date, ensuring everything is completed just in time.

Sequencing Jobs

Specifies the order in which jobs should be performed at work centers

Job time

time needed for setup and processing of a job

Priority Rules of Sequencing

1. First come, first served (FCFC)

2. Shortest Processing Time (SPT)

3. Earliest Due Date (EDD)

4. Longest Processing Time (LPT)

5. Rush

First Come, First Served (FCFS)

processes jobs in the order they arrive, with no special consideration for how long each job takes.

Shortest Processing Time (SPT)

Jobs are processed according to processing time at a machine or work center, shortest job first

Earliest Due Date (EDD)

Jobs are processed according to due date, earliest due date first.

Longest Processing Time (LPT)

Jobs are processed according to processing time at a machine or work center, longest job first.

Rush

Emergency of preferred customers first

Benefits of Shortest Processing Time (SPT)

does well on minimizing flow time and number of jobs in the system

Risks of Shortest Processing Time (SPT)

moves long jobs to the end which may result in dissatisfied customers

Benefits of Earliest Due Date (EDD)

minimizes maximum lateness

Limitations of Rule-Based Dispatching Systems

1.Scheduling is dynamic and rules need to be revised to adjust to changes

2.Rules do not look upstream or downstream

3.Rules do not look beyond due dates

Finite Capacity Scheduling (FCS)

is a smart, visual scheduling tool that keeps work realistic, organized, and flexible when things change.

Finite Capacity Scheduling (FCS) Example

A furniture company uses software to schedule when to cut wood, assemble furniture, and pack orders. If a machine goes down, the system updates the schedule in real time so everything still gets done efficiently and on time.

Steps to Minimize Scheduling Difficulties

1. set realistic due dates

2. focus on bottleneck operations

   1. try to increase the capacity

   2. if not possible schedule the bottle neck operations first

3. consider lot splitting for large jobs

Theory of Constraints: Metrics

1. throughput

2. inventory

3. operating expense

Throughput

the rate at which the system generates money through sales

Inventory

represents money ries up in goods and materials used in a process

Operating Expense

all the money the system spends to convert inventory into throughput: this includes utilities, scrap, depreciation, and so on

throughput up, inventory and operating expense down

From (the Goal) what do we want for the theory of constraints