The DBR logistical system is a finite scheduling mechanism that balances the flow of the system. DBR controls the flow of materials through the plant in order to produce products in accordance with market demand with a minimum of manufacturing lead time, inventory and operating expense.
The definitions of DRUM, BUFFER and ROPE are:
The first step is the identification of all the processing, resource, and marketing constraints within the entire system is needed. These constraints become the primary focus of attention. They are then used to derive the planning, scheduling and control of all the plant's resources. The result provides a smooth and continuous flow of materials through the plant with minimum disruptions.
Any schedule or production plan must be productive, reliable, robust and realistic. Productive in that it must relate to the market demand while contributing to and being measurable against the organisation's goal; reliable and robust in that it must reflect the capability of the resources available and stand up to the inevitable disturbances or disruptions that will hit it; realistic in that it is capable of being done with the resources available including material supply.
In any plant, there are only a few Capacity Constraint Resources (CCRs). All CCRs are identified, and the various orders that are to be processed through them are scheduled according their capacity potential and to the market demand. The schedule established for the CCRs determines the drum beat for the system.
The essential operational steps of DBR scheduling are as follows:
Buffers provide the timely protection of CCRs from any likely or expected disruption. The rope is the timely release of raw materials into the system and is tied to the size of the buffer. Buffer Management (BM) provides the means by which the schedule is managed on the shop floor. The strategic points at which buffers are established are called the buffer origins.
Buffer Management & Continuous Improvement.
A schedule needs to be productive, realistic and reliable - it should also be emphasised that a schedule is only as good as the ability to manage it or "make it happen". This is where the Buffer Management control comes in and is a very important aspect of the DBR application. Buffer Management will help identify resources likely to restrict Throughput and/or increase Inventory and is also key to maintaining continuous improvement.
Buffer Management will firstly help to ensure the schedules for the CCRs, and thereby the total schedule, are maintained. Secondly, by identifying trouble-making non-CCRs, it can also focus attention on these and point towards areas for improvement. If, as a result of the improvements there is less disruption from problems then the 'Murphy element' of the buffers can be reduced, resulting in shorter lead times.
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