Section L: Execution and Control Flashcards
production activity control (PAC)
production activity control (PAC)
Includes scheduling, implementation, and capacity control. PAC, along with purchasing, are execution activities. PAC transforms the in-house manufacturing requirements of the material requirements plan into finished goods and services.
What’s the end part of Material Requirements Planning?
The end of the material requirements planning process involves the material planner providing the production coordinator with planned orders to be released after verifying that capacity is available using capacity requirements planning (CRP).
What’s the first step of the Production Coordinator?
The production coordinator starts by scheduling the start and finish dates of these orders.
Operations sequencing is used to dispatch jobs according to their current priority level based on certain rules. What are those methods?
Operations sequencing is used to dispatch jobs according to their current priority level based on certain rules, including the following methods:
- First come, first served (FCFS)
- Earliest job due date (EDD)
- Earliest operation due date (ODD)
- Shortest process time (SPT)
- Critical ratio
- Slack time
How does Capacity control differ based on whether intermittent or flow process types are being used?
Capacity control differs depending on whether intermittent or flow process types are being used.
For intermittent processes (work center or batch), capacity control uses input/output control to monitor and control inputs to and outputs from work centers in order to control backlogs (queues) and thus WIP inventory levels.
In flow (line or continuous) process types, capacity control uses flow control to adjust the rate of the process as needed. Lean may also use flow control.
theory of constraints (TOC)
theory of constraints (TOC)
A holistic management philosophy developed by Dr. Eliyahu M. Goldratt, based on the principle that complex systems exhibit inherent simplicity.
Even a very complex system comprising thousands of people and pieces of equipment can have, at any given time, only a very, very small number of variables—perhaps only one, known as a constraint—that actually limit the ability to generate more of the system’s goal.
How did TOC differ from conventional thinking?
Conventional thinking at the time was additive, meaning that, due to process complexity, streamlining any part of a system where improvements could be found would be beneficial to total system output.
However, according to TOC, real gains in efficiency can be made only by finding the part of the system that constrains total output—the weakest link—and making efficiency improvements to that area and only that area.
constraint
constraint
Any element or factor that prevents a system from achieving a higher level of performance with respect to its goal. Constraints can be physical, such as a machine center or lack of material, but they can also be managerial, such as a policy or procedure.
A constraint is a limit on throughput, or the rate of production, not on inventory or production.
bottleneck
bottleneck
A facility, function, department, or resource whose capacity is less than the demand placed upon it. For example, a bottleneck machine or work center exists where jobs are processed at a slower rate than they are demanded.
Throughput
Throughput
The rate at which the system generates “goal units.” Because throughput is a rate, it is always expressed for a given time period—such as per month, week, day, or even minute. If the goal units are money, throughput is an amount of money per time period. In that case, throughput is calculated as revenues received minus totally variable costs divided by units of the chosen time period.
Cycle time
Cycle time
1) In industrial engineering, the time between the completion of two discrete units of production. For example, the cycle time of motors assembled at a rate of 120 per hour is 30 seconds.
2) In materials management, the length of time from when material enters a production facility until it exits.
What are the 3 types of constraints?
The 3 different types of constraints:
- physical constraints
- capacity-constrained resources (CCR)
- behavior-based constraints (sometimes called “non-constraints”)
Physical constraints
Physical constraints are related to resources (equipment, labor, materials), or they are market constraints.
capacity-constrained resource (CCR)
capacity-constrained resource (CCR)
A resource that is not a constraint but will become a constraint unless scheduled carefully. Any resource that, if its capacity is not carefully managed, is likely to compromise the throughput of the organization.
Behavior-based constraints
Behavior-based constraints are generated by persons and management policies.
This can include administrative or other unnecessary steps that take time away from performing necessary process steps at a bottleneck area. It could be personnel that do not know they are working at a bottleneck work center and unnecessarily delay the process, or it could be a management decision not to spend time on improvement because of past failures.
Principles of Bottleneck Management
How should inputs be provided to a bottleneck area?
The rate at which a bottleneck can process work is the rate at which its inputs should be provided to avoid increasing WIP inventory before it. Work centers that depend on the output of the bottleneck should be scheduled to work at the rate set by the bottleneck.
Principles of Bottleneck Management
The capacity of the production depends on the capacity of what?
The capacity of the production process depends on the capacity of the bottleneck, so breakdowns or slowdowns in this area directly reduce system throughput.
Principles of Bottleneck Management
Why is a setup at a bottleneck work center an opportunity cost?
Priority and capacity are interrelated, meaning that priority (demand) for different types of units promotes more setups, but each new setup at a bottleneck work center is an opportunity cost because it takes time away from processing, thus reducing utilization.
Principles of Bottleneck Management
How should output from a bottleneck area be provided?
Output from bottleneck areas should be provided to the next work center(s) in smaller lots than a full batch size (in a split lot). The amount to move might be the amount finished each day or even more often, depending on materials handling costs. This smaller lot is called a split lot or a transfer batch.
Principles of Bottleneck Management
How should capacity constrained resources be scheduled?
The goal should be to maximize the total throughput of the plant, in other words, to maximize the revenue the plant produces by balancing the flow of units produced to maximize the amount of demand that can be satisfied. This means scheduling capacity-constrained resources to avoid bottlenecks.
split lot
split lot as follows: A manufacturing order quantity that has been divided into two or more smaller quantities, usually after the order has been released. The quantities of a split lot may be worked on in parallel, or a portion of the original quantity may be sent ahead to a subsequent operation to be worked on while work on the remainder of the quantity is being completed at the current operation. The purpose of splitting a lot is to reduce the lead time of the order.
Principles of non-Bottleneck Management
What is the principle of improving nonbottleneck capacity?
Nonbottleneck capacity improvements do not improve total capacity.
Principles of non-Bottleneck Management
How to determine the rate of nonbottleneck areas?
Nonbottleneck areas set their maximum utilization not based on their potential but on the rate determined at the bottleneck. This means that nonbottleneck areas may be idle at times. However, when they are run, they should still be run using proper efficiency, quality, and cost principles (it runs at full speed when running).
Principles of non-Bottleneck Management
Does 100% utilization in a nonbottleneck area make sense?
Using a nonbottleneck area 100 percent of the time does not result in 100 percent utilization, since it would simply build up more and more WIP inventory and eventually need to be stopped.
Drum-buffer-rope (DBR)
Drum-buffer-rope (DBR)
The theory of constraints method for scheduling and managing operations that have an internal constraint or capacity-constrained resource.
Drum schedule
Drum schedule
The detailed production schedule for a resource that sets the pace for the entire system.
The drum schedule must reconcile the customer requirements with the system’s constraint(s).
Buffer
Buffer
In the theory of constraints, buffers can be time or material and support throughput and/or due date performance.
Buffers can be maintained at the constraint, convergent points (with a constraint part), divergent points, and shipping points.
The buffer, or time buffer, is an amount of inventory maintained before the constraint to ensure that the constraint never stops due to a lack of inputs.
time buffer
The Dictionary defines a time buffer as “protection against uncertainty that takes the form of time.”
The duration of the time buffer will be based on the amount of variability in production or purchasing.
The rope metaphor.
The rope is like a demand-pull signal, only, in this case, the signal is the throughput rate at the constraint. One cannot push a rope; one can only pull it.
Imagine that all WIP inventory is attached to a long rope and that the constraint process is pulling on the rope at the rate needed to match its production, neither faster nor slower.
Market Demand as Constraint
There are times when the constraint is not internal, for example, when there is insufficient demand for a company’s product or service—i.e., demand is far below the system’s capacity and the market is constraining the system’s throughput. This is an external market constraint.
Considerations of Market Constraints
Considerations of Market Constraints
- The drum is at shipping and is based on market needs.
- The rope connects the drum to the material release point (as in conventional DBR).
- The time buffer is only at shipping. This will result in a small bank of finished goods in front of shipping, which allows for a greater likelihood that the company will meet its order due dates.
- The S-DBR assumes that all resources have sufficient protective capacity in the event of a higher-than-expected market demand.
- The workflow needs to be managed to match the slowest area in the workflow.
The theory of constraints contains a five-step cyclical process, called the five focusing steps.
In the theory of constraints, a process to continuously improve organizational profit by evaluating the production system and market mix to determine how to make the most profit using the system constraint.
five focusing steps
- Identify the constraint.
Determine throughput rates and demand rate. - Exploit the constraint. Maximize utilization, partly through buffers.
- Subordinate everything else to the constraint. The top priority is effective utilization of the constraint.
- Elevate the constraint. Increase the capacity of the constraint.
- Once the constraint is relieved, identify the new constraint. There is always a new constraint, so the process repeats.
How to identify if sales is the constraint?
If no work centers are working at full capacity and all orders are being released and completed on time, then sales is the constraint. If
How to identify the constraint in a linear process?
Identifying the Constraint in a Linear Process is straightforward.
The work center with the lowest production rate is the constraint.
productive capacity
productive capacity as follows: In the theory of constraints, the maximum of the output capabilities of a resource (or series of resources) or the market demand for that output for a given time period.
