|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.
|4 Primary Steps for DBR Scheduling
||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
||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".
||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
|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.
||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.
|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
|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.