DBA is a demand-driven scheduling system that uses target required dates with flexible feedback.
How It Works
Demand-driven scheduling consists of four schedules, each of which is auto-generated by the program without need for manual intervention.
1. Sales Order Schedule
Sales orders establish the target demand dates that drive the scheduling system. The program calculates a Required Date for each line item, derived from the lead time and order policy settings that comprise the item’s planned Time to Shipment target.
Item required dates are consistent over time
Each item’s Required Date basis is the same number of days from order to order, regardless of quantity, which provides customers with consistent times to shipment. Jobs with larger quantities get higher priority in work center queues, which reduces waiting time and enables such jobs to meet their target demand dates.
Required dates prioritize order picking
Orders for an item are picked in earliest Required Date order so that orders are shipped in the order they were received. The Sales > Picking Manager screen allocates available stock on hand to sales orders in line item Required Date order and indicates which orders are fully or partially ready for picking.
The Expected Ship date reflects actual conditions
Each line item Required Date is accompanied by an Expected Ship date, which reflects actual conditions and can be used as the customer communications date. Unlike the Required Date, which is a target demand date that drives MRP and shop priorities, the Expected Ship date can be freely changed as needed.
Job Finish dates provide feedback for Expected Ship dates
When a job is scheduled late relative to its target required date, it provides feedback for the Late Supply screen, which lists dependent sales order lines that are likely to be shipped late and enables updating of Expected Ship dates and communication to the customer if necessary.
2. PO Schedule
DBA is a demand-driven MRP system. Purchase orders are generated in response to firm demand within each item’s planning period, which is the action window for buying the item. Future demand from jobs outside the planning period is ignored for now and is responded to in future MRP sessions.
Demand-driven inventory replaces forecasts and projections
Future requirements are planned with demand-driven stocking instead of forecasts and projections to avoid injecting longer-term, tentative, and revision-prone demand into the schedule. A monthly demand rate is incorporated into item reorder points for demand-driven stocking. POs only get triggered by actual demand, which caps and minimizes any over-stocking.
PO due dates are derived from item Lead Days settings
PO due dates are derived from item Lead Days settings and do not vary by quantity. This provides consistent date alignment with job planned start dates over multiple MRP sessions.
All POs are for current delivery
PO due dates are derived from item Lead Days settings. Demand-driven stocking eliminates longer-term, tentative, and revision-prone POs from the schedule. All purchase orders are sent to suppliers immediately upon creation and are for current delivery.
The PO line expected date reflects actual conditions
Late POs are monitored in the PO Schedule screen to expedite delivery from suppliers and to assess impact on dependent jobs. If the supplier furnishes a firm delivery date, the line item Expected Date can be updated to update the system supply date.
3. Released Job Schedule
Jobs are released to live production when allocated materials become available, which is often dependent on inbound supply from subassembly jobs and purchase orders. When a job gets released, it is given a new Job Finish date relative to its actual released date. The new Finish Date is a reliable supply date that automatically provides up to date feedback system wide.
Initial job dates are placeholders
Initial dates for new status jobs are placeholder dates that maintain multi-level date alignment in the master job schedule up through job release. The Planned Start date is the target date for Job Release.
Job release is when the schedule goes live
The job release process is when the schedule goes live because it is the point at which jobs begin actual production.
Job release is delayed when materials are not available
A job is only released to production when allocated materials become available. When subassembly jobs or inbound POs are behind schedule, job release is delayed for any jobs that are dependent on those materials. These items will provide clear feedback in the dependency inquiry in the Job Release, Job Schedule and PO Schedule screens.
Jobs are automatically rescheduled with release
When a job does get released, it is given a new Job Finish date relative to its actual released date, which makes the live job schedule self-adjusting.
Job release ensures the correct order of assembly
Job release is performed multiple times per day as lower level jobs are finished, which provides supply for dependent higher level jobs waiting to be released and ensures that jobs are released and started in the correct order of assembly.
The job Finish Date reflects actual conditions
If during the course of a job it becomes apparent that the job will be finished later than scheduled, the Job Finish date can be manually adjusted in the Job Schedule screen and this will update the system supply date.
Late Supply screen improves communication between the shop and the office
When a job is running late and is released for production the finish date (supply date) is moved outward. When the finish date is greater than the sales order requirement date this job will show up in the Sales > Late Supply screen. This will immediately let the office know which jobs are running late and they can update the Expected Ship date and contact the customer if appropriate.
4. Work Center Schedule
The Work Center Schedule screen prioritizes production activities and is used to execute the released job schedule.
Jobs spend more time in queues than in production
A job typically spends more time in work center queues than it does in actual production. Whenever a job arrives in a work center, it competes with other jobs and must wait its turn to begin production. The Work Center Schedule manages this process by allocating queue time based on job priority.
Each job is automatically prioritized
Each released job is prioritized based on remaining production time relative to its target demand date. Jobs running behind schedule get higher priority over jobs running ahead of schedule
Larger jobs get higher priority
When a job has an unusually large quantity, it has more production time, which gives the job higher priority than would otherwise be the case with a normal quantity. The job will experience less waiting time in work center queues, which is how it can meet its target demand date in spite of the larger quantity.
Prioritized production expedites jobs and optimizes production flow
Prioritized production, where work centers are run by job priority, is far more efficient than ad hoc expediting done one job at a time. Jobs are efficiently expedited in coordinated fashion, which optimizes production flow and boosts shop throughput.
Materials are issued in real time
Along with real time labor updating, materials are issued as they are used by job sequences for real time inventory tracking.
Labor sequences are updated in real time
Within the Work Center Schedule job sequences are updated in real time to update job priorities, work center queues, and enable real time job tracking. Labor updating is facilitated by applying standard hours to completion quantities as sequences are closed.
Deploying workers and machines
Monitoring work center queues in the Work Center Schedule identifies bottlenecks and areas of the shop that need attention. This enables efficient deployment of workers and machines or application of overtime hours and extra shifts.
Benefits
Provides customers with consistent times to shipment
With other planning systems ship dates are established ad hoc and vary from order to order.
By contrast, DBA’s demand-driven scheduling provides customers with consistent and reliable ship dates over time. Each item’s sales order required dates are calculated from its planned Time to Shipment target and do not vary with different order quantities. Instead, job priority flexibly adapts so that larger jobs experience less waiting time in work center queues.
Eliminates constant rescheduling
Other planning methods generate longer term jobs and POs from forecast explosions. This demand is tentative and must be firmed up as actual demand materializes, which requires constant rescheduling to avoid shortages and over-stocking. Rescheduling is complex because demand is interdependent among lower level items, which causes many companies to resort to inefficient job linking to simplify the process. Because rescheduling is so time-consuming, planning sessions are limited to once or twice a week, which delays timely response to new demand.
By contrast, demand-driven scheduling only generates jobs and POs from actual demand within item planning periods, which is the action window for making or buying the item. This demand is firmly set and job dates are left as is until jobs are released to live production. MRP generation takes very little time and is run daily for immediate response to new demand.
Provides sales with feedback from production
In other systems the communication between sales and production regarding job status is inefficient and requires manual investigation. Customers are often left in the dark regarding the status of their orders.
By contrast, the Late Supply screen in DBA provides the sales department with feedback from production. The screen lists sales order lines dependent on jobs scheduled for late finish and enables Expected Ship dates to be updated to reflect each item’s likely ship date.
Eliminates material hoarding
Other systems suffer from “rob Peter to pay Paul” syndrome where shop personnel hoard materials so that favored jobs can be started.
By contrast, the job release process in DBA allocates materials on hand to jobs in planned start date order. This eliminates any need for material hoarding and determines when jobs can be started. When inbound supply from purchase orders or subassembly jobs is late, release must be delayed for dependent jobs. When a job does get released, it is given a new job finish date relative to its released date, which makes the job schedule self-adjusting.
Identifies bottlenecks that need attention
In other systems the only way to know what’s going on in the shop is through manual investigation. Bottlenecks easily escape detection and do not receive timely attention.
By contrast, the Work Center Schedule in DBA provides complete visibility of work center queues. Unusual queue sizes quickly identify bottlenecks that can be mitigated by deploying workers and machines or overtime hours or extra shifts.
Prioritizes shop activities
In other systems jobs are expedited one at a time to meet promised ship dates, which penalizes other jobs that get moved to the back of work center queues.
By contrast, the Work Center Schedule in DBA prioritizes shop activities so that workers always know what to run next in each work center. Jobs are run in priority order within work center queues so that jobs running behind schedule get priority over jobs running ahead of schedule. Running work centers by job priority optimizes production flow so that all jobs meet their target demand dates.
Tips for Success
Make target demand dates tight and realistic
Shop productivity and throughput increase when target demand dates push shop personnel to greater performance. By contrast, padded dates are easy to beat and encourage complacency. For best results, make item P item Lead Days and M item Job Days settings tight and realistic.
Apply safety to expected dates, not lead days or job days
If your objective is to pad ship dates with a safety factor, apply padding to line item Expected Ship dates, but not to item Lead Days or Job Days settings. When Lead Days and Job Days settings are padded, numerous problems ensue, including unrealistic sales order required dates, inability to track late POs, chronic early job release, and invalid job prioritization.
Never enter future jobs
Never enter future jobs to explode projected demand because it is not compatible with demand-driven scheduling. Future job projections corrupt the new job schedule with longer term, tentative supply that is highly subject to revisions. Instead, replace long term projections with demand-driven stocking whereby a monthly demand rate is incorporated into item reorder points. It is a far more efficient way to plan for future requirements because jobs only get triggered by actual demand and are firmly set upon creation.
Never enter blanket purchase orders unless required
Do not enter blanket purchase orders unless required by a supplier because they are not compatible with demand-driven scheduling. Future purchase orders corrupt the PO schedule with longer term, tentative supply that is highly subject to revisions. Instead, replace blanket POs with demand-driven replenishment whereby a monthly demand rate and supply days interval are incorporated into item reorder points and min order quantities. Each PO is triggered by actual demand, which prevents shortages and over-stocking and eliminates the constant revisions required to manage blanket POs.
Never release jobs without material
Never release jobs without allocated materials because doing so circumvents the rescheduling process that is central to demand-driven scheduling and feedback.
Run work centers in priority order
When an item has different job quantities, demand-driven scheduling adapts with job priority instead of varying the lengths of jobs. Jobs with larger quantities get higher priority, which reduces waiting time in work center queues. Always run work centers in job priority order and update job labor sequences in real time.
