Buffer Management is the practice of using buffers to account for process variability. Monitoring time buffers enables planers to focus on Jobs that are at risk of critical delay which can impact on-time delivery and possibly starve Drum Resources. The Buffer Management Workbench is the primary tool to assist in monitoring risky buffer penetration.
Buffer Management Workbench
The Buffer Management Workbench View is used for primarily three purposes:
- Identify which Manufacturing Orders and Purchase Orders are at risk with respect to their various DBR Buffers so that they can be expedited.
- Clarify how much is at risk in terms of throughput and revenue and the level of urgency.
- Compare performance in terms of Buffer Penetration between plants.
To open this view, select “Buffer Management Workbench” from the Performance tab of the Ribbon.
This window is divided into three sections:
- Options along the top: These options control what is shown in the chart and in the grids to enable the user to focus on the information of interest.
- Graphical chart in the middle: The chart provides an easy way to compare various buffer related measures.
- Detailed list along the bottom: The specific purchase orders and manufacturing orders are listed in this section. These lists can be printed and drill-down is available in various areas.
This section describes the various options available to control what data is displayed in the chart and grids. After changing these values, click “Apply” to update the chart and grids based on the current options.
- A list of all Plants is shown.
- Check one or more Plants to filter data for those specific Plants.
- There are three types of Buffers: Material, Drum, and Shipping. Select one or more to filter data for those types of buffers.
- Material Buffers pertain to Purchase Orders. Drum and Shipping Buffers pertain to Manufacturing Orders.
- There are three warning levels, and each is related to the amount of Buffer Penetration that is occurring.
- OK: Less than 33% Buffer Penetration
- Warning: Between 33% and 66% Buffer Penetration.
- Critical: More than 66% Buffer Penetration.
- Note that for Manufacturing Orders this filter works in conjunction with the M.O. Penetration Type described below. The Warning Level is based on the level of Penetration of the Penetration Type specified below.
- If only one Warning Level is checked then the chart is colored in Green/Yellow/Red according to the Warning Level selected.
M.O. Penetration Type:
- For Manufacturing Orders there are two types of Buffer Penetration:
- Current: This is based on the current PC time and the M.O. current status.
- Projected: This is based on where the M.O. is currently scheduled.
- Purchase Orders only have a Current Penetration since they are not scheduled.
- These values only affect the chart, not the grids.
- Primary Group / Secondary Group: These settings work together to determine how the grid summary data is grouped and displayed in the chart. If the Secondary Group is set to “None” then a simple chart is shown, similar to the example above. If the Secondary Group is set to another value then the Secondary values are shown grouped within the Primary Group. Note that if Warning Levels are shown as the Primary Group and the Secondary Group is “None” then the chart is colored in Green/Yellow/Red according to Warning Level.
- Values: This control determines what type of value data is plotted along the Y axis of the Chart.
- Throughput: The sum of the Throughputs of the Manufacturing Order Jobs. Note that if the same Job appears more than once on the lists then it is only counted once.
- Revenue: The sum of the Revenues of the Manufacturing Order Jobs. Note that if the same Job appears more than once on the lists then it is only counted once.
- Count: The total number of Purchase Orders and Manufacturing Orders included in the grids.
- Item Quantity: The sum of the quantities of the Manufacturing Orders. Note that if the same M.O. appears more than once on the lists then it is only counted once.
- Drum Work Hours: The sum of the work hours scheduled on the Drums for all Drum Buffer M.O.s in the grid.
- The Grids are divided into three tabs according to the three types of Buffers: Material, Drum, and Shipping.
- The Drum and Shipping grids allow for drill-down into the Job/Manufacturing Order screen by selecting the “Open” button or double-clicking the row selector.
- Like other grids in APS, these grids can be grouped, sorted, printed, opened in Excel, etc.
Fields for Gantt Labels and Reporting
- DBR Receiving Buffer: Purchased Material should be received this amount of time before the PO Scheduled Receipt Date to protect against variability in delivery times from vendors.
- DBR Shipping Buffer: Production should be completed this amount of time before the MO Need Date to avoid late shipments due to variability after the Drum.
- Manufacturing Order
- Drum Operation: The Operation with an eligible Drum Resource having the largest Buffer. If multiple Operations have eligible Drum Resources with the same maximum Buffer then the earliest one in the Path is used.
- Drum Due Date: The JIT Start Date for the Drum Operation minus the Shipping Buffer.
- DBR Release Date: The date/time when the MO should be released. If the MO uses a Drum then this is the Drum Due Date minus the Drum Buffer. Otherwise this is the JIT Start Date minus the Shipping Buffer.
- DbrShippingBuffer: The Shipping Buffer of the Product’s Inventory. Zero if the M.O. has no Product defined.
- DbrShippingDueDate: The MO NeedDate minus the Shipping Buffer. The MO should be completed by this time to avoid Shipping Buffer penetration.
- DBR Buffer: The longest eligible Resource Buffer of the Drum Operation.
- DrumUsedByCurrentPath: Indicates whether the MOs current path has a Drum Operation.
- Drum ResourceName: The name of the Drum Resource with the largest Buffer for the Drum Operation.
- DBR Shipping Due Date: The datetime when the Job/MO should arrive in shipping. (Job Need Date minus Shipping buffer)
- Current Buffer Warning Level: OK, Warning, Critical (based on the current status of the job relative to the Drum/shipping)
- Projected Buffer Warning Level: OK, Warning, Critical (based on the scheduled readiness at the Drum/shipping)
- Drum Buffer Current Penetration Percent: Penetration is calculated based on the PC time and whether the job is ready at the drum. For example, a Job is marked RED if the current time is within 1/3 of the buffer from the drum start time and the pre-drum operation is not yet completed. If the Drum Operations predecessors are finished then the latest predecessor Reported Finish date is used instead.
- ShippingBufferCurrentPenetrationPercent: Calculates the Shipping Buffer Penetration at the current PC time. If the MO is finished then the Reported Finish date is used instead.
- Drum Buffer Projected Penetration Percent: Penetration is calculated based on when the job is scheduled to be ready at the drum. For example, a Job is marked RED if the time when the pre-drum operation is scheduled to complete within 1/3 of the buffer from the drum start time. If the Drum Operations predecessors are finished then the latest predecessor Reported Finish date is used instead.
- ShippingBufferProjectedPenetrationPercent: Calculates the Shipping Buffer Penetration using the MO’s current Scheduled End Date. If the MO is finished then the Reported Finish date is used instead.
- Purchase To Stock
- DbrReceiving Buffer: The Receiving Buffer of the Inventory for the PTS.
- DbrReceiptDate: Material should be received by this date to avoid penetrating the material receiving buffer. The ScheduledReceiptDate minus the Receiving Buffer.
- DbrCurrentPenetrationPercent: The percent of time between the DbrReceiptDate and the ScheduledReceiptDate that has been passed by the current PC clock.
Gantt Display of Drum Buffer Penetration Warnings
Manufacturing Order Buffer Penetrations can be shown in the Gantt by checking the box in the Activity Display Options window as shown below.
If checked, the Buffer Penetration is shown according to the drop-down shown below. If it’s set to Current Penetration then the warnings are based on the Manufacturing Order’s Drum Buffer Current Penetration Warning Level field. Otherwise it’s set to the Drum Buffer Projected Penetration Warning Level field.
The Label can also be set to display textual information such as the Penetration Percent, the Drum Resource, etc. as shown below.
DBR Hint Info in the Gantt
Click this button to enable Hint Info in the Gantt
When an Activity is clicked, it shows vertical bars for DBR Release Date and Drum Due Date (along with the other Hint Info) as shown below.
This helps to understand how the DBR rules relate to the Manufacturing Order of interest.
In this example, the MO starts at the DBR Release Date. The projected Buffer Penetration is in the OK range so the MO is shown in green:
After dragging the MO to a later time, the projected Buffer Penetration is now in the Warning range so the MO is shown in yellow:
After dragging the MO to an even later time, the projected Buffer Penetration is now in the Critical range so the MO is shown in red:
Case 1: Set Drum Buffers
Description: Periodically the scheduler will set the buffers for Drum Resources. The scheduler will open the “Resources” window and set the Drum Buffers for each Drum Resource.
Case 2: Analyze Buffers Penetrations and take actions to resolve issues
Description: Each day, the scheduler will review the buffer penetrations to look for problems. He will open the Buffer Management Workbench window and set the Warning Levels to “Critical” and possible “Warning”. Then he’ll look at the Drums grid to see which M.O. have warnings. He’ll then filter or sort the alerts in a way that enables him to focus on the alerts from most important/urgent to least. For example, he may filter to only show Jobs for Orders or which have Customers specified and then sort by Drum Due Date.
He’ll start by looking at “Current Penetrations” to deal with issues that are most urgent. The alerts can be opened in Excel and mailed to someone else in the organization to expedite the jobs. The scheduler can also record Notes for each Job to keep track of any actions taken to expedite the materials.
Then he’ll look at “Projected Penetrations” to proactively look for buffer penetrations that are scheduled to occur unless the schedule is adjusted. He can open the Job to further investigate the problem and take corrective action.
Case 3: Set Buy Buffers
Actor: Material Planner
Description: Periodically the material planner will set the buffers for raw materials. The planner will open the Inventory window where Shipping and Material Buffers can be set.
Case 4: Analyze Buffers Penetrations and take actions to resolve issues
Actor: Material Planner
Description: Each day, the material planner will review the material buffer penetrations to look for problems. He will open the Buffer Management Workbench window and look at the material buffer grid for warnings. He’ll then filter or sort the alerts in a way that enables him to focus on the alerts from most important/urgent to least. For example, he may filter to only show POs for Sales Orders and then sort by Scheduled Receipt Date.
The alerts can be opened in Excel and mailed to someone else in the organization for follow-up. The planner can also record comments for each PO to keep track of any actions taken to expedite the materials.