You can plan your repetitive assemblies in terms of daily production rates rather than discrete quantities. Many of the repetitive planning functions are similar to those of discrete planning.
You can use repetitive planning to plan supply and demand for repetitive assemblies using daily production rates rather than discrete quantities.
You can use bucket days and planning horizons to define three repetitive planning regions. You can define smaller planning periods in the short term, to maintain an optimal balance between smoothing production and responding to daily demand fluctuations. You can define larger planning periods for your long–term plan plans, to monitor supply and demand trends for your repetitive assemblies.
You can define a repetitive anchor date to stabilize the repetitive planning process during subsequent planning runs within the same repetitive planning period.
You can pass demand down from repetitive assemblies to repetitive components, from repetitive assemblies to discrete components and from discrete assemblies to repetitive components.
You can use safety stock and order modifiers to implement your inventory and production policies for your repetitive assemblies.
You can allocate suggested aggregate repetitive schedules across individual production lines according to line priorities and production rates you define in Oracle Work in Process.
You can firm part or all of your current repetitive schedules in Oracle Work in Process to prevent the repetitive planning process from suggesting daily quantities that differ from your current firm rates.
You can use planning time fences, acceptable rate changes, and overrun percents to control the nervousness of your repetitive plans and to minimize disruption of your short term shop floor and supplier schedules.
You can use the Planner Workbench to implement suggested repetitive schedules as current repetitive schedules in Oracle Work in Process.
You can use a comprehensive selection of reports and on–line inquiries to review and monitor all aspects of your repetitive planning process.
See Also
Overview of Repetitive Manufacturing, Oracle Work in Process User's Guide
Overview of Material Requirements Planning
Repetitive planning allows you to plan your repetitive assemblies using daily production rates rather than discrete quantities.
The output of the repetitive planning process is a set of suggested repetitive schedules for each one of your repetitive assemblies.
Each repetitive schedule for repetitive assembly is defined by:
a daily quantity
a start date
an end date
Although there are many similarities between repetitive planning and discrete planning, there are also a number of important differences.
Repetitive schedules represent planned supply for repetitive assemblies in the same way that planned orders represent planned supply for discretely planned assemblies. The difference, however, is that repetitive schedules are defined using daily quantities; whereas planned orders are defined using discrete quantities. Also, the daily quantities defined for repetitive schedules represent supply for each workday between the repetitive schedule start and end dates. The discrete quantities defined for planned orders represent supply for a single date, the planned order due date, only.
There is another important difference between repetitive planning and discrete planning. The repetitive planning process always suggests new aggregate repetitive schedules that replace current aggregated schedules to satisfy net requirements for a given planning period. This is different from discrete planning where, if net requirements exist, the planning process suggests planned orders to supplement existing scheduled receipts.
In repetitive planning, therefore, suggested repetitive schedules alone match net requirements within a repetitive planning period. With discrete planning, it is the summation of planned orders and existing orders that always match net requirements for the same period.
Unlike the reschedule recommendations that the planning process generates for discrete jobs, the repetitive planning process never recommends that current repetitive schedules defined in Oracle Work in Process be rescheduled. Instead, it always recommends a set of new suggested repetitive schedules that satisfy current net requirements.
The reason for this lies in the way in which repetitive schedules are defined. Since repetitive schedules are defined by a daily quantity, a start date and an end date, if the repetitive planning process were to recommend new daily quantities and new start and end dates, as it would do if it were recommending that a repetitive schedule be rescheduled, it would essentially be defining a new schedule.
The repetitive planning process uses four dates to define repetitive schedules:
First unit start date
Last unit start date
First unit completion date
Last unit completion date
The first unit start date (FUSD) represents the date you plan to start production of the first assembly on a repetitive schedule.
The last unit start date (LUSD) represents the date you plan to start production of the last assembly on a repetitive schedule.
The first unit completion date (FUCD) represents the date you plan to complete production of the first assembly on a repetitive schedule.
The last unit completion date (LUCD) represents the date you plan to complete production of the last assembly on a repetitive schedule.
The difference between the FUSD and the FUCD represents the lead time of a repetitive assembly, and is the amount of time that it takes to complete a single unit of the assembly from start to finish. Oracle Work in Process calculates the lead time based on the routing for lines with a lead time basis of Routing based. Oracle Work in Process defaults the lead time from the production line for repetitive schedules on production lines with a lead time basis of Fixed.
The difference between the FUSD and the LUSD represents the repetitive processing days for your repetitive schedule. These are the number of days you plan to work on your repetitive schedule.
There are four different types of repetitive schedules:
Current aggregate repetitive schedule
Current repetitive schedule
Suggested aggregate repetitive schedule
Suggested repetitive schedule
Current aggregate repetitive schedules represent the sum of all current work in process repetitive schedules for repetitive assemblies, across all production lines, for a specified period. Current aggregate repetitive schedules are defined as an assembly, a daily quantity, a start date and an end date.
Current repetitive schedules are a portion of current aggregate repetitive schedules. They represent individual work in process repetitive schedules producing repetitive assemblies on a single production line. Current repetitive schedules are defined as an assembly, a daily quantity, a start date, an end date, and a production line.
Suggested aggregate repetitive schedules represent the optimal repetitive schedules suggested by the repetitive planning process to satisfy the total demand for repetitive assemblies within a given period. They represent suggested total production across all production lines.
Suggested repetitive schedules are a portion of suggested aggregate repetitive schedules. They represent individual suggested repetitive schedules producing repetitive assemblies on a single production line. The repetitive planning process generates suggested repetitive schedules during the repetitive schedule allocation process. See: Repetitive Schedule Allocation.
The repetitive planning process always tries to smooth supply by suggesting daily quantities that match average daily demand. The time period over which demand is averaged is a user–defined number of days, or bucket, known as the repetitive planning period. Since average daily demand and suggested daily quantities are calculated by dividing total demand by the total number of workdays in your planning periods, the sizes of your planning periods are very important.
Period Sizes and Horizons
You can use three period sizes, called bucket days, and two horizons to define the granularity of repetitive plans across your planning horizon. The first bucket days are used to generate all repetitive planning periods within your first horizon. The second bucket days are used to generate all planning periods within your second horizon. The third bucket days are used to generate all other planning periods up to the end of your workday calendar.
Repetitive planning periods can never overlap. For example, if your first horizon is 20 days and your second horizon is 40 days, your first horizon extends from day 1 to day 19. Your second horizon extends from day 20 to day 59.
You may want to use smaller periods in the short term. Since your daily demand is averaged over smaller time periods, smaller planning periods result in suggested daily quantities that more accurately respond to your short–term fluctuations in demand.
You may want to use larger periods in the long term. Since your daily demand is averaged over larger time periods, larger planning periods result in fewer and less precise suggested daily quantities. These are useful for identifying long–term plan trends in repetitive supply and demand.
There is also a performance advantage to using larger buckets further out along the planning horizon. It takes the repetitive planning process less time to calculate fewer, larger schedules than it takes to calculate many smaller schedules.
You can choose to use Calendar dates or Work dates to generate your planning periods.
Calendar dates allow you to fix the length of your planning periods, regardless of the timing of non–workdays and holidays. This option always creates weekly start dates on the same day of the week.
Work dates do not fix the length of your planning periods. Work dates allow your planning periods to shift out in response to non–workdays and holidays. This option does not create weekly start dates on the same day of the week, for example, if there is a holiday in the middle of the week.
If you want your planning periods to always start on a Monday, regardless of weekends and holidays, use calendar dates and verify that your bucket days and planning horizons are all multiples of 7. Also make sure that your anchor date is a Monday.
You can use the Work Dates window to review your workday calendar and identify which days have been calculated as repetitive planning period start dates.
Repetitive planning always acts on completion dates. Notice that repetitive schedules have two completion dates: first unit completion date and last unit completion date. These two completion dates are analogous to due dates for planned orders. In both cases, the dates represent the date when supply is assumed to be available to satisfy demand. The repetitive planning process always assumes that the supply is available at the beginning of the day.
The planned supply represented by repetitive schedules becomes available to satisfy demand after the first assembly on the schedule is completed. Thereafter, there is supply, for a quantity equal to the daily rate, for each workday between the FUCD and the LUCD.
To ensure that the supply is available on the first date on which demand needs to be satisfied, the repetitive planning process offsets the FUCD by the assembly lead time to determine the FUSD.
The repetitive planning process always assumes that production can only take place on a workday.
Without any restrictions, such as firm or partially firm repetitive schedules, the repetitive planning process always suggests a daily rate that equals the optimal rate.
The basic calculation of optimal rates involves three steps:
Sum net requirements
Calculate average daily demand
Set optimal rate = average daily demand
The repetitive planning process calculates optimal rates by summing net requirements for each repetitive assembly within each repetitive planning period. An average daily demand is calculated by dividing the total demand for the period by the total number of workdays within the same period. The repetitive planning process recommends an optimal rate that matches the average daily demand.
The repetitive planning process passes down demand, from repetitive assemblies to repetitive components as daily rates rather than discrete quantities. Component requirements are offset from using assembly requirements in the same way lead time offsets are used for discrete assemblies and components in discrete planning.
The following diagram illustrates how component demand is passed down as a rate. Notice that when component requirements are offset from using assembly requirements by the assembly lead time, the component demand can sometimes span multiple planning periods. This can result in multiple suggested daily rates that differ from the original demand rate.
Safety stock and order modifiers help you translate discrete and repetitive demand into planned orders and repetitive schedules that match your inventory and production policies.
You can specify safety stock days, together with safety stock percent, as item attributes using the Define Item window in Oracle Inventory. For discretely manufactured items, the planning process calculates the safety stock quantity by multiplying the safety stock percent by the average gross requirements for the period of time defined by the safety stock days.
For repetitively manufactured items, the repetitive planning process multiplies the safety stock percent by the average daily demand for each repetitive planning period. The repetitive planning process calculates the safety stock quantity for each repetitive period across the planning horizon.
Order modifiers for repetitive assemblies work in a similar way to order modifiers for discrete assemblies.
Minimum and maximum order quantities are translated into minimum and maximum daily rates.
Fixed order quantities are translated into fixed daily rates. With fixed daily rates, the repetitive planning process recommends a rate equal to the fixed daily rate or a rate of zero.
Fixed lot multiples are translated into fixed daily rate multiples.
Rounded order quantities are translated into rounded daily rates. Fixed days supply has no real meaning in repetitive environments.
Safety stock and order modifiers are useful when you have repetitive assemblies that report to discrete assemblies or discrete assemblies that report to repetitive assemblies.
You can use safety stock to avoid a stock out for repetitive assemblies. Although your demand should always be satisfied by the end of each planning period, there may be temporary shortages within the period as the schedules build up supply. If you do not want to carry excess inventory in the form of safety stock, you may want to reduce the size and increase the number of your repetitive planning periods. This means that there is less smoothing of supply, resulting in suggested daily rates that more closely match fluctuations in your demand. The best way to avoid shortages within planning periods is to smooth your demand.
If you have a repetitive assembly that has a discretely planned component, then the repetitive planning process suggests planned orders for each day in the period spanned by the repetitive schedules for the assembly. Under these circumstances, you might want to consider using order modifiers, such as fixed days supply, fixed lot multiple or minimum order quantities for the discrete component. This helps to reduce the number of planned orders generated for the discrete component.
The anchor date introduces consistency into your material and distribution plans by stabilizing your repetitive planning periods. The anchor date represents the start date of your first repetitive planning period. The anchor date fixes your repetitive planning periods as time passes so that a plan run on any day during the first planning period does not see fluctuating average daily demand.
Without the anchor date, the planning periods shift each day and individual demands can move from one planning period into the next. This can result in different average daily demands and therefore different suggested daily rates.
Note that the actual demand never changes, it is only the time periods over which they are averaged that move each day.
The anchor date must lie on or before the current date and is defined both manually and automatically. You can manually enter a default anchor date as a planning parameter. You can override the default anchor date when you plan material requirements or when you plan your master schedules. Since the anchor date is a system parameter, overriding the anchor date resets the system anchor date. Resetting the anchor date always triggers a recalculation of the repetitive planning periods.
The anchor date is automatically updated to the beginning of the current planning period when the current date moves out of a prior planning period. The anchor date is also automatically updated when you plan material requirements, plan your master schedules or change your repetitive planning parameters. This allows your planning periods to be automatically rolled forward as time passes. The anchor date is always updated to the start date of the current repetitive planning period.
Repetitive schedule allocation is the process by which the repetitive planning process takes suggested aggregate repetitive schedules and allocates them across one or more work in process production lines. After repetitive schedule allocation, the sum of all suggested repetitive schedules for an assembly should always equal the suggested aggregate repetitive schedule for the same assembly.
The repetitive schedule allocation process is driven by suggested aggregate repetitive schedules, and line priorities and production rates you define in the Oracle Work in Process window, Define Repetitive Assembly. An example of repetitive schedule allocation is illustrated in the following diagram. The example illustrates how various suggested aggregate rates would be divided and allocated across three production lines.
In the example, lines A and B have the same line priority, 1, while line C has a line priority of 2. You assign line priorities to help the repetitive planning process decide which lines it should allocate repetitive schedules to. In the example, you may have customized lines 1 and 2 to manufacture your assembly with minimum waste and optimum speed. It may be possible, but more expensive, to also build the assembly on line C, so you assign it a lower priority.
You define production rates to represent the rate at which an assembly can be manufactured on specific production lines. Different assemblies may require different production rates on the same production line. Similarly, the same assembly may require different production rates on different production lines. The production rate for an assembly, on a given production line, must fall within the minimum and maximum hourly rates defined for the production line in the Oracle Work in Process window, Define Production Line. The example assumes production rates of 400/hour, 200/hour and 100/hour for lines A, B and C, respectively.
Notice that until the aggregate rate exceeds 400/hour, the rate is distributed evenly across lines A and B. This is because lines A and B share the same priority, which also happens to be the highest priority defined for the assembly, and because lines A and B have production rates of 400/hour and 200/hour respectively.
Once the rate exceeds 400/hour, line B is fully loaded. Since there is still capacity available on line A, the repetitive schedule allocation process continues to load line A until it too is fully loaded. It is only when both lines A and B are fully loaded that the repetitive schedule allocation process uses the line priorities to decide which lines to use to allocate any remaining portion of the suggested aggregate rate.
In the example, any aggregate rate between 601 and 700 units/hour is allocated to line C. Once all lines available for building the assembly have been fully loaded, the repetitive schedule allocation process loads any additional unallocated rates evenly across the highest priority lines, in this case lines A and B.
You can firm part or all of your current repetitive schedules for a repetitive assembly in Oracle Work in Process.
If you firm all your current repetitive schedules for an assembly in Oracle Work in Process, the repetitive planning process considers the current aggregate repetitive schedule to be firm. The sum of all your firm schedules for an assembly is called the firm rate. Rather than calculating an optimal rate for assemblies with firm rates, the repetitive planning process suggests the firm rate for the duration of the firm aggregate schedule.
The repetitive planning process suggests the firm rate for the duration of the firm aggregate schedule. After the firm period, the suggested rate is increased to address the previous depletion in supply caused by the firm rate being less than the optimal rate. If the optimal rate was less than the firm rate, the repetitive planning process decreases the suggested rate after the firm period in response to the previous build up of supply.
As an example, the repetitive planning process is 10 units short as a result of the firm rate. The optimal rate is 12/day. However, for the duration of the firm schedule, the suggested rate is restricted to 10/day. This creates a shortage of 2/day for 5 days, resulting in a total shortage of 10 units. This increases the total demand in the next planning period from 36 to 46 units. The firm schedule breaks up two planning periods (Periods 2 and 3) into four smaller planning periods (Periods 2, 3, 4, and 5).
If you have firmed some, but not all, of your current repetitive schedules for an assembly, the repetitive planning process considers your current aggregate repetitive schedule to be partially firm. The sum of all firm schedules is called the minimum firm rate. If the optimal rate calculated by the repetitive planning process is less than the minimum firm rate, the repetitive planning process suggests the minimum firm rate for the duration of the partially firm aggregate schedule. If the optimal rate is greater than the minimum firm rate, the repetitive planning process suggests the optimal rate. The minimum firm rate acts as the floor for the suggested rates for the duration of your partially firm aggregate schedule.
The repetitive planning process suggests the minimum firm rate for the duration of the partially firm schedule. After the partially firm period, the suggested rate is decreased due to the previous build up in supply caused by the minimum firm rate being greater than the optimal rate.
As an example, the repetitive planning process has a 25 unit surplus as a result of the minimum firm rate. The optimal rate is 10/day. However, for the duration of the partially firm schedule, the suggested rate is restricted to 15/day. This creates a surplus of 5/day for 5 days, resulting in a total surplus of 25 units. This reduces the total demand in the next planning period from 30 to 5 units. The partially firm schedule breaks up two planning periods (Periods 2 and 3) into four smaller planning periods (Periods 2, 3, 4, and 5).
Your repetitive assembly lead times create an implicit firm schedule. Inside the lead time, the repetitive planning process always suggests the current aggregate rate. This is true even if your current aggregate rate is zero. The repetitive planning process assumes an implicit firm schedule inside your assembly lead times on the assumption that any new suggested rates, even if implemented immediately, can only be realized as supply outside the assembly's lead time.
The repetitive planning process suggests the current aggregate firm rate for the duration of the assembly lead time. In the example, the current aggregate rate is 5 per day.
After the assembly lead time, the suggested rate is increased to address the previous depletion in supply caused by the current aggregate rate being less than the optimal rate. The firm schedule formed by the assembly lead time breaks the first planning period into two smaller planning periods.
The repetitive planning process uses the planning time fence to help stabilize your material plans and minimize disruption to your short term shop floor and supplier schedules. You can control the nervousness of your repetitive material plans by specifying minimum and maximum rate changes that are enforced by the repetitive planning process inside the planning time fence.
There are two repetitive item attributes used by the repetitive planning process to stabilize production inside the planning time fence. The acceptable rate increase percent and acceptable rate decrease percent represent the percentage of the current aggregate rate by which your suggested daily rates can vary from current aggregate rates within a repetitive planning period inside the planning time fence.
Acceptable rate changes allow you to represent assembly constraints. For example, you might define acceptable rate changes for a repetitive assembly to simulate the rate at which you can realistically ramp production of the assembly up or down.
The repetitive planning process calculates acceptable rate increase amounts by multiplying the current aggregate rate by the acceptable rate increase percent. For example, if the current aggregate rate is 100/day and the acceptable rate increase percent is 10%, the acceptable rate increase amount is 10/day. Inside the planning time fence, the repetitive planning process could not suggest a daily rate greater than 110/day.
Similarly, an acceptable rate decrease amount is calculated by multiplying the current aggregate rate by the acceptable rate decrease percent. For example, if the current aggregate rate is 100/day and the acceptable rate decrease percent is 10%, the acceptable rate decrease amount is 10/day. Inside the planning time fence, the repetitive planning process could not suggest a daily rate greater than 90/day.
If the optimal rate is greater than the current aggregate rate plus the acceptable rate increase amount, the repetitive planning process suggests a daily rate that is equal to the current aggregate rate plus the acceptable rate increase amount. Using the earlier example, the repetitive planning process would suggest a daily rate of 110/day for any optimal rate greater than 110/day.
If the optimal rate is less than or equal to the current aggregate rate plus the acceptable rate increase amount, the repetitive planning process suggests a daily rate that is equal to the optimal rate. Using the same example, the repetitive planning process suggests a daily rate equal to the optimal rate for any optimal rate between 100/day and 110/day.
If the optimal rate is less than the current aggregate rate minus the acceptable rate decrease amount, the repetitive planning process suggests a daily rate that is equal to current aggregate rate minus the acceptable rate decrease amount. Using the earlier example, the repetitive planning process suggests a daily rate of 90/day for any optimal rate less than 90/day.
If the optimal rate is greater than or equal to the current aggregate rate minus the acceptable rate decrease amount, the repetitive planning process suggests a daily rate that is equal to the optimal rate. Using the same example, the repetitive planning process suggests a daily rate equal to the optimal rate for any optimal rate between 90/day and 100/day.
The repetitive planning process is free to suggest any daily rate outside the planning time fence.
Undefined acceptable rate changes remove the planning time fence since they do not restrict the amount by which the repetitive planning process can vary suggested rates. This is not true for zero acceptable rate changes. Zero acceptable rate changes are used to restrict the repetitive planning process from suggesting any rate changes at all inside the planning time fence.
Undefined values allow the repetitive planning process to suggest changes to the current aggregate rate without restriction. Zero values prevent the repetitive planning process from suggesting any changes at all. For example, if you choose to make the acceptable rate increase zero and leave the acceptable rate decrease undefined, the repetitive planning process suggests a rate between zero and the current aggregate rate, but no greater than the current aggregate rate.
You can also use the overrun percent item attribute to control the nervousness of your material plans by allowing current repetitive schedules to overbuild by a small amount without incurring new suggested daily rates. In this way, planning overrun amounts reduces minor and unnecessary rate change suggestions.
The overrun amount is equal to the optimal rate for the planning period multiplied by the overrun percent. For example, if your optimal rate is 100/day and your overrun percent is 10%, the repetitive planning process calculates an overrun amount of 10/day.
The repetitive planning process only recommends a new repetitive schedule if the current aggregate rate is greater than the optimal rate plus the overrun percent. According to the previous example, the repetitive planning process only suggests a new repetitive schedule if the current aggregate rate is greater than 110/day.
The overrun percent for repetitive planning is analogous to acceptable early days delivery in discrete planning. Both attributes allow you to make the business decision that you would prefer to carry additional inventory for a short time, rather than disrupt your shop floor production schedules.
It is important to note that the overrun percent only applies for overproduction. As with acceptable early days delivery, the repetitive planning process allows you to build ahead and carry excess inventory, but does not allow you to plan a shortage. Because the overrun percent often results in overproduction within planning periods, use of this attribute can sometimes have an impact on subsequent planning periods. Later periods may need to produce less as a result of the excess supply produced in earlier periods.
Master production schedules represent build schedules, or statements of planned production.
Each time you implement a portion of your master production schedule as a discrete job or a purchase requisition, you are creating actual supply. To avoid overstating supply, you need to relieve your planned supply by the quantity you have implemented as actual supply.
For discrete assemblies, total supply is considered by the planning process to be the sum of your master production schedules plus the scheduled receipts defined in Oracle Work in Process and Purchasing. With discrete planning, there are two versions of supply that must be kept in balance to avoid overstatement of supply.
For repetitive assemblies, however, master production schedules are not summed with current work in process repetitive schedules. With repetitive planning, these two versions of supply are compared and contrasted, and represent two alternative statements of supply rather than two components that are summed together.
Therefore, with repetitive planning, there is only one version of supply and therefore no need to keep two complementing versions in balance. For this reason, there is no production relief for repetitive master production schedules.
You can use the Planner Workbench to implement your suggested repetitive schedules as repetitive schedules in Oracle Work in Process. The default status for a repetitive schedule loaded from the Planner Workbench is Pending – mass loaded. When implementing your repetitive schedules, you can choose to implement selected schedules as firm repetitive schedules. You can additionally modify the first and last unit completion dates, daily rates and the processing days suggested by the repetitive planning process. You can also override the production lines that were assigned to your suggested repetitive schedules during the repetitive schedule allocation process.