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Drum-Buffer-Rope Scheduling |
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DBR Scheduling takes the principles of Drum-Buffer-Rope and puts them to work on the factor floor. There are 4 primary steps to creating schedules and each step is discussed below. Before continuing, we would recommend reviewing the DBR and Time Buffers pages. |
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4 Primary Steps for DBR Scheduling |
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Step 1 |
Create a DBR Order Time-Line and locate the order’s ship date. Step backwards from this point by the Shipping Buffer quantity, followed by the minimum processing time (transfer batch size = 1). Remember, the minimum processing time does not include queuing, waiting or moving. Format should be similar to "Figure 5" from the Time Buffers page. This determines the order’s estimated starting point. Next, identify any processing time occurring on a drum. Most product chains will be modeled with at least one drum. Repeat this process for each order. |
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Step 2 |
Transfer all drum jobs to a Drum Time-Line. Each order's initial DBR Order Time-Line estimates the start and end points for its drum job(s). Load the drum job(s) onto the Drum Time-Line according to these dates. Initially, jobs are placed on the Drum Time-Line regardless of available capacity. If there is a job(s) already occupying the time slot, work is allowed to "stack-up". |
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Step 3 |
The "stacked height" of the drum jobs should equal the number of drum units (operators) available at the workcenter. A backward scheduling pass levels the drum jobs according to the number of units. The relative position between jobs is |
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maintained as jobs are pushed backwards. Some drum jobs may lie in the past once the backward pass is completed. Execute a forward pass to push work in the past back across the present time line. Now the drum schedule is almost complete. The planner finalizes the schedule by changing job order to meet company priorities. The final schedule establishes the firm Start and End date/time for each job. Repeat Steps 2 & 3 for each drum. |
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Step 4 |
Transfer each drum job back to its order's DBR Order Time-Line. The drum job's start date/time serves as the order's anchor on the DBR Order Time-Line. |
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Now rebuild the rest of the DBR Time-Line. From this point back add the Drum Buffer and upstream processing time. This establishes the Material Release Date. |
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Finally, add the downstream processing time and Shipping Buffer in front of the anchor point. This establishes the completion date/time. Compare this with the order's promised ship date. If the estimated completion date is later, the order will not meet the promised ship date. |
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