PRODUCTION SCHEDULE
Production schedules coordinate activities to increase productivity and minimize operating costs.
A production schedule can identify resource conflicts, control the release of jobs to the shop, ensure that required raw materials are ordered in time, determine whether delivery promises can be met, and identify time periods available for preventive maintenance.
The two key problems in production scheduling are “priorities” and “capacity” in other words,
“What should be done first?” and “Who should do it?”
scheduling is “establishing the timing for performing a task” and observes that, in manufacturing firms, there are multiple types of scheduling, including the detailed scheduling of a shop order that shows when each operation must start and complete.
detailed scheduling is “the actual assignment of starting and/or completion dates to operations or groups of operations to show when these must be done if the manufacturing order is to be completed on time.” . note that this is also known as operations scheduling, order scheduling, and shop scheduling
Unfortunately, many manufacturers have ineffective production scheduling systems. They produce goods and ship them to their customers, but they use a broken collection of independent plans that are frequently ignored, periodic meetings where unreliable information is shared, expediters who run from one crisis to another, and ad-hoc decisions made by persons who cannot see the entire system. Production scheduling systems rely on human decision-makers, and many of them need help dealing with the swampy complexities of real-world scheduling
decision support tools that have been developed to improve production scheduling, from Gantt charts to computer-based scheduling tools. Computer software has been useful in cases.
However, information technology is not necessarily the answer.
computer-based scheduling can help manufacturers improve on-time delivery, respond quickly to customer orders, and create realistic schedules,
but success requires using finite scheduling techniques and integrating them with other manufacturing planning systems.
Finite scheduling uses actual shop floor conditions, including capacity constraints and the requirements of orders that have already been released. However, only 25% of the firms responding to their survey used finite scheduling for part or all of their operations. Integration is also difficult. Only 48% of the firms said that the computer-based scheduling system received routine data automatically from other systems, 30% said that a “good deal” of the data are entered manually, and 21% said that all data are entered manually.
FREDERICK TAYLOR ANDTHE PLANNING OFFICE ;production scheduling is a distinct decision-making process in which individuals share information, make plans, and react to unexpected events.
Scheduling is defined as “the timing of all operations with a view to insuring their completion when required.” Mitchell emphasizes that, in some shops, the shop foremen may be responsible for determining which specific worker and machine does which task. In others, the scheduling personnel have already determined this.
Generally known for his fundamental contributions to scientific management in the late 1800s, Frederick Taylor’s most important contribution to production scheduling was his creation of the planning office (described in Taylor, 1911). separation of planning from execution justified the use of formal scheduling methods, which became critical as manufacturing organizations grew in complexity. It established the view that production scheduling is a distinct decision-making process in which individuals share information, make plans, and react to unexpected event
Here we briefly describe some of the positions that are most closely related to scheduling.
The route clerk created and maintained routings that specified the operations required to complete an order and the components needed.
The instruction card clerk wrote job instructions that specified the best way to perform the operations.
The production clerk created and updated a master production schedule based on firm orders and capacity.
The balance of stores clerk maintained sheets with the current inventory level, the amount on order, and the quantity needed for orders. This clerk also issued replenishment orders.
The order of work clerk issued shop orders and released material to the shop. Recording clerks kept track of the status of each order by updating the route charts and also creating summary sheets (called progress sheets). The relative priority of different orders was determined by the superintendent of production.
An interesting feature of the planning office was the bulletin board. There was one in the planning office, and another on the shop floor (Thompson, 1974). The bulletin board had space
or every workstation in the shop. The board showed, for each workstation, the operation that the workstation was currently performing, the orders currently waiting for processing there, and future orders that would eventually need processing there. (In modern software, this bulletin board has been replaced by the dispatch lists that show all of the work waiting for processing at a workstation.)
HENRY GANTT AND HIS CHARTS The man most commonly identified with production scheduling is Henry Gantt, who worked with Taylor at Midvale Steel Company, Simonds Rolling Machine Company, and Bethlehem Steel and then worked as a consultant
Gantt explicitly described scheduling, especially in the job shop environment.
He discussed the need to coordinate activities to avoid “interferences” but warned that the most elegant schedules created by planning offices are useless if they are ignored. To improve managerial decision-making, Gantt created innovative charts for visualizing planned and actual production.
According to Cox et al. (1992): a Gantt chart is “the earliest and best known type of control chart especially designed to show graphically the relationship between planned performance and actual performance.”
Gantt designed his charts so that foremen or other supervisors could quickly know whether production was on schedule, ahead of schedule, or behind schedule.
His charts were improvements to the forms that Taylor developed for the planning office. Gantt was a pioneer in developing graphical ways to visualize schedules and shop status. He used time (not just quantity) as a way to measure tasks. He used horizontal bars to represent the number of parts produced (in progress charts) and to record working time (in machine records). His progress (or layout) charts had a feature found in project management software today: the length of the bars (relative to the total time allocated to the task) showed the progress of tasks.
Gantt’s work on charts reflects the decision-making perspective, which is the view that scheduling is a decision that a human must make. Schedulers perform a variety of tasks and use both formal and informal information to accomplish these. Schedulers must address uncertainty, manage bottlenecks, and anticipate the problems that people cause (McKay and Wiers, 2004).
Gantt’s charts attempt to provide clearly the key data needed to make these decisions.
Clark (1942) provides an excellent overview of the different types of Gantt charts, including the machine record chart and the man record chart, both of which record past performance. Of most interest to those studying production scheduling is the layout chart, which specifies “when jobs are to be begun, by whom, and how long they will take.”
JOHNSON AND THE FLOW SHOP SCHEDULING PROBLEM set a standard for the analysis of production scheduling problems of all kinds from the very beginning
AN INTEGRATIVE STRATEGY
A production schedule can identify resource conflicts, control the release of jobs to the shop, ensure that required raw materials are ordered in time, determine whether delivery promises can be met, and identify time periods available for preventive maintenance.
The two key problems in production scheduling are “priorities” and “capacity” in other words,
“What should be done first?” and “Who should do it?”
scheduling is “establishing the timing for performing a task” and observes that, in manufacturing firms, there are multiple types of scheduling, including the detailed scheduling of a shop order that shows when each operation must start and complete.
detailed scheduling is “the actual assignment of starting and/or completion dates to operations or groups of operations to show when these must be done if the manufacturing order is to be completed on time.” . note that this is also known as operations scheduling, order scheduling, and shop scheduling
Unfortunately, many manufacturers have ineffective production scheduling systems. They produce goods and ship them to their customers, but they use a broken collection of independent plans that are frequently ignored, periodic meetings where unreliable information is shared, expediters who run from one crisis to another, and ad-hoc decisions made by persons who cannot see the entire system. Production scheduling systems rely on human decision-makers, and many of them need help dealing with the swampy complexities of real-world scheduling
decision support tools that have been developed to improve production scheduling, from Gantt charts to computer-based scheduling tools. Computer software has been useful in cases.
However, information technology is not necessarily the answer.
computer-based scheduling can help manufacturers improve on-time delivery, respond quickly to customer orders, and create realistic schedules,
but success requires using finite scheduling techniques and integrating them with other manufacturing planning systems.
Finite scheduling uses actual shop floor conditions, including capacity constraints and the requirements of orders that have already been released. However, only 25% of the firms responding to their survey used finite scheduling for part or all of their operations. Integration is also difficult. Only 48% of the firms said that the computer-based scheduling system received routine data automatically from other systems, 30% said that a “good deal” of the data are entered manually, and 21% said that all data are entered manually.
FREDERICK TAYLOR ANDTHE PLANNING OFFICE ;production scheduling is a distinct decision-making process in which individuals share information, make plans, and react to unexpected events.
Scheduling is defined as “the timing of all operations with a view to insuring their completion when required.” Mitchell emphasizes that, in some shops, the shop foremen may be responsible for determining which specific worker and machine does which task. In others, the scheduling personnel have already determined this.
Generally known for his fundamental contributions to scientific management in the late 1800s, Frederick Taylor’s most important contribution to production scheduling was his creation of the planning office (described in Taylor, 1911). separation of planning from execution justified the use of formal scheduling methods, which became critical as manufacturing organizations grew in complexity. It established the view that production scheduling is a distinct decision-making process in which individuals share information, make plans, and react to unexpected event
Here we briefly describe some of the positions that are most closely related to scheduling.
The route clerk created and maintained routings that specified the operations required to complete an order and the components needed.
The instruction card clerk wrote job instructions that specified the best way to perform the operations.
The production clerk created and updated a master production schedule based on firm orders and capacity.
The balance of stores clerk maintained sheets with the current inventory level, the amount on order, and the quantity needed for orders. This clerk also issued replenishment orders.
The order of work clerk issued shop orders and released material to the shop. Recording clerks kept track of the status of each order by updating the route charts and also creating summary sheets (called progress sheets). The relative priority of different orders was determined by the superintendent of production.
An interesting feature of the planning office was the bulletin board. There was one in the planning office, and another on the shop floor (Thompson, 1974). The bulletin board had space
or every workstation in the shop. The board showed, for each workstation, the operation that the workstation was currently performing, the orders currently waiting for processing there, and future orders that would eventually need processing there. (In modern software, this bulletin board has been replaced by the dispatch lists that show all of the work waiting for processing at a workstation.)
HENRY GANTT AND HIS CHARTS The man most commonly identified with production scheduling is Henry Gantt, who worked with Taylor at Midvale Steel Company, Simonds Rolling Machine Company, and Bethlehem Steel and then worked as a consultant
Gantt explicitly described scheduling, especially in the job shop environment.
He discussed the need to coordinate activities to avoid “interferences” but warned that the most elegant schedules created by planning offices are useless if they are ignored. To improve managerial decision-making, Gantt created innovative charts for visualizing planned and actual production.
According to Cox et al. (1992): a Gantt chart is “the earliest and best known type of control chart especially designed to show graphically the relationship between planned performance and actual performance.”
Gantt designed his charts so that foremen or other supervisors could quickly know whether production was on schedule, ahead of schedule, or behind schedule.
His charts were improvements to the forms that Taylor developed for the planning office. Gantt was a pioneer in developing graphical ways to visualize schedules and shop status. He used time (not just quantity) as a way to measure tasks. He used horizontal bars to represent the number of parts produced (in progress charts) and to record working time (in machine records). His progress (or layout) charts had a feature found in project management software today: the length of the bars (relative to the total time allocated to the task) showed the progress of tasks.
Gantt’s work on charts reflects the decision-making perspective, which is the view that scheduling is a decision that a human must make. Schedulers perform a variety of tasks and use both formal and informal information to accomplish these. Schedulers must address uncertainty, manage bottlenecks, and anticipate the problems that people cause (McKay and Wiers, 2004).
Gantt’s charts attempt to provide clearly the key data needed to make these decisions.
Clark (1942) provides an excellent overview of the different types of Gantt charts, including the machine record chart and the man record chart, both of which record past performance. Of most interest to those studying production scheduling is the layout chart, which specifies “when jobs are to be begun, by whom, and how long they will take.”
JOHNSON AND THE FLOW SHOP SCHEDULING PROBLEM set a standard for the analysis of production scheduling problems of all kinds from the very beginning
AN INTEGRATIVE STRATEGY
This hierarchy suggests the following integrative strategy for improving production scheduling. It is important to note that, throughout this process, the input and feedback of those doing and supervising production scheduling must be included.
Based on the above discussion, it is clear that these three perspectives form a hierarchy, with the problem-solving perspective at the lowest level, the decision-making perspective in the middle, and the organizational perspective at the highest level.Moving among these three perspectives corresponds to shifting one’s focus from the production planning organization to one person to one task.
1. Study the production scheduling system. Create a model of the persons in the production scheduling system, their tasks and decisions, and the information flow between them
2. Analyze this model and determine if changes to the information flow, task assignments, or decision-making responsibilities are desirable and feasible. If changes are needed, go to Step 6.
3. Given that the patterns of information flow are satisfactory, consider the decision-making process that the scheduler uses. Determine if the scheduler is able to manage bottleneck resources effectively, understand the problems that occur (whether caused by others or by themselves), and take steps to handle future uncertainty (McKay and Wiers, 2004). If not, changes in these areas are suggested. If changes are needed, go to Step 6
4. Consider dividing the workload between the human scheduler and a decision support tool. As suggested by McKay and Wiers (2006), the design of a scheduling decision support tool should be guided by the following concepts: (1) the ability of the scheduler to directly control the schedule (called “transparency”), (2) the amount of uncertainty in the manufacturing system, (3) the complexity of the scheduling decison, and (4) how well-defined the scheduling decision is. An ill-defined scheduling decision is characterized by incompleteness, ambiguity, errors, inaccuracy, and possibly missing information (McKay and Wiers, 2006). If a new or improved decision support tool is needed, go to Step 6..
5. Finally, consider improving production scheduling problem-solving by developing a more appropriate problem formulation or installing more powerful algorithms that can find better solutions faster. Consult the enormous literature on scheduling problems for different approaches to these challenges.
6. Implement the changes that were selected.
7. Assess the impact of the implemented changes and repeat the above steps as necessary.
Based on the above discussion, it is clear that these three perspectives form a hierarchy, with the problem-solving perspective at the lowest level, the decision-making perspective in the middle, and the organizational perspective at the highest level.Moving among these three perspectives corresponds to shifting one’s focus from the production planning organization to one person to one task.
1. Study the production scheduling system. Create a model of the persons in the production scheduling system, their tasks and decisions, and the information flow between them
2. Analyze this model and determine if changes to the information flow, task assignments, or decision-making responsibilities are desirable and feasible. If changes are needed, go to Step 6.
3. Given that the patterns of information flow are satisfactory, consider the decision-making process that the scheduler uses. Determine if the scheduler is able to manage bottleneck resources effectively, understand the problems that occur (whether caused by others or by themselves), and take steps to handle future uncertainty (McKay and Wiers, 2004). If not, changes in these areas are suggested. If changes are needed, go to Step 6
4. Consider dividing the workload between the human scheduler and a decision support tool. As suggested by McKay and Wiers (2006), the design of a scheduling decision support tool should be guided by the following concepts: (1) the ability of the scheduler to directly control the schedule (called “transparency”), (2) the amount of uncertainty in the manufacturing system, (3) the complexity of the scheduling decison, and (4) how well-defined the scheduling decision is. An ill-defined scheduling decision is characterized by incompleteness, ambiguity, errors, inaccuracy, and possibly missing information (McKay and Wiers, 2006). If a new or improved decision support tool is needed, go to Step 6..
5. Finally, consider improving production scheduling problem-solving by developing a more appropriate problem formulation or installing more powerful algorithms that can find better solutions faster. Consult the enormous literature on scheduling problems for different approaches to these challenges.
6. Implement the changes that were selected.
7. Assess the impact of the implemented changes and repeat the above steps as necessary.
