The spare part functionality allows you to forecast the demand for spare parts as if they are component parts. These spare part forecasts are seen by MRP as a source of demand for the part that is over and above the component demand. Once the spare part forecasts have been generated, the system consumes these forecasts as customer orders for the parts each time spare parts are ordered. This allows you to see the actual demand for the part - as a replacement part - in the form of customer orders.
Note: Only spare part forecasts are seen by MRP as demand. Spares family forecasts that have not been disaggregated to the spare part level are not seen as demand by MRP.
Spares families are a logical grouping of spare parts that share some common characteristic(s). The members of a spares family may comprise a kitted part (such as a carburetor kit) that is sold as a replacement part. Alternatively, a spares family may consist of a set of similar parts with independent demand, such as different size gaskets or water pumps.
It is important to realize that shop orders and customer orders cannot be placed for a spares family. Such orders can only be placed for individual spare parts that are members of a family.
If you desire, you can create spares families consisting of parts associated with several different sites. Thus, spares families are not necessarily tied to a single site. This gives flexibility to the concept of a spares family, but this has a price; there can be a different calendar associated with each part in a spares family.
Attributes that are defined for a spares family become the defaults for each spare part that is added to that family. This provides you with a convenient way to create a template for all spare parts in a family. However, it is also possible to override the family defaults at the individual spare part level, permitting you to deal with exceptions to the template as well.
Spares families are uniquely identified by their Family Code. The Family Code is a sequence of alphanumerics up to 25 characters in length. This code is accompanied by a text description. Spare families also have a Consumption Window, used during the available-to-promise check, in order to control the range of days in which the system can consume forecasts when a customer order is taken for the spare part. The system attempts to find sufficient forecasts within the time frame specified by the Consumption Window to satisfy the quantity ordered. If it does find these, the order process proceeds. If it does not, an MRP action message is generated. The Consumption Window that is defined for a spares family is inherited by all spare parts subsequently added to that family; it can be overridden.
Spare families also have a Roll Flag attribute associated with them. The Roll Flag determines how the system will handle past due forecasts during the disaggregation process. The disaggregation process converts spares family forecasts into spare part forecasts for each spare part in the family.
There are two settings for the roll flag: Roll Out and Drop Forecast. If the roll flag is set to Roll Out (during the disaggregation process), the system will total all past due spare part forecast quantities, consumed forecast, and actual demand and place them in a rolled record on the date the disaggregation process is being run or on the next working day. If the roll flag is set to Drop Forecast, only the past due consumed forecast and actual demand are totaled and placed in the rolled record. The past due forecast quantity is discarded. The roll flag defined for a spares family is inherited by all spare parts in that family but can be overridden.
Once you have created one or more spares families, you can add spare parts to that family. As mentioned above, these parts can be associated with any site in the system.
Spare parts inherit the values for Roll Flag and Consumption Window from their family. However, this value can be overridden for the spare parts. In addition, spare parts have the attributes Overage and Quantity Per.
Quantity Per represents the percentage of a spares family forecast that should be assigned to this spare part when the family forecasts are disaggregated to the spare part level. It is not necessary that the Quantity Per sum for a spares family total 100. It is possible to overplan (the total is > 100%) or underplan (the total is < 100%) the spare parts in a spares family, depending on the situation. The result of overplanning is that, after disaggregation, the sum of the spare part forecasts for all parts in that spares family will total more than the original spare family forecast. The result of underplanning is that, after disaggregation, the sum of the spare part forecasts for all parts in that spares family will total less than the original spare family forecast.
The spare part forecast calculated using the value for Quantity Per is rounded up to the next whole number during the disaggregation process. The Overage column stores the difference between the last calculated forecast and the actual (rounded) forecast amount. The benefit to compiling an overage amount is that it results in a more accurate tally of actual orders. By tracking (and accumulating) the rounding up that occurs during disaggregation, it is possible to reduce the quantity of the spare part that will need to be manufactured or purchased. Although the overage will never amount to more than one unit between any two forecasts, it can accumulate to a significant amount in cases where multiple forecasts are disaggregated at once.
It is only when multiple forecasts are disaggregated at once that overages are taken into consideration. In this case, the overage from the first disaggregated forecast is factored into the calculation of the second disaggregated forecast, while the overage from the second is factored into the calculation of the third, and so on. However, when forecasts are disaggregated one at a time, the existing overage will not be factored and the overage that results will reflect only the rounding for the forecast that was just disaggregated.
Once you have defined a spares family, you can create forecasts for that family. A spares family forecast is an estimate made by a planner of the expected replacement demand for all members of the spares family on a specified date. The planner bases this estimate on experience or historical data, such as the average number of units of the family ordered per week or month over the past year.
The spares family forecasts are a convenient way for the planner to generate spare part forecasts for the all of the spare parts that comprise the spares family. The disaggregation process is the method by which spare family forecasts are converted into spare part forecasts.
Note that it is not necessary to associate spare parts with the family before creating family forecasts. However, family forecasts are not seen as demand by MRP. MRP sees only the spare part forecasts as demand. To have spare family forecasts seen as demand by MRP, it is necessary to disaggregate them first. Therefore, although spares family forecasts can be created without spare parts being associated with the family, these forecasts can never be disaggregated and seen by MRP until spare parts have been defined.
Note: Customer orders for spare parts do not consume spares family forecasts, only spare part forecasts.
Spares family forecasts have a Forecast Quantity and Forecast Date. The Forecast Quantity is the predicted demand for all spare parts in that family at the Forecast Date.
Note that the forecast date for a spares family forecast may or may not be a working day in the manufacturing calendars defined for the sites associated with the spare parts that comprise that family. The date of a spare part forecast can differ from the date of the spares family forecast from which it was disaggregated.
In addition, spares family forecasts have an Allow Disaggregation flag. This flag permits spares family forecasts to be marked so that they are not 'seen' during the disaggregation process. When a spares family forecast is created, the flag is set to Allow Disaggregation. The disaggregation process itselfdoes not change the value of the Allow Disaggregation flag. You can set this flag manually. This permits you to experiment with the results of different sets of spares family forecasts to achieve a desired result at the spare part forecast level.
A spare part forecast is an estimate of the expected demand for a particular spare part on a specified date. There are several different types of spare part forecasts. The different types of forecasts are derived from different sources. In one instance, a spare part forecast of the type Disaggregated or Rolled is generated by the system via the disaggregation of spares family forecasts. Note that the system-generated spare part forecasts of the type Disaggregated are calculated based on a combination of spares family forecast and spare part information. In another instance, a spare part forecast of the type Forecast is imported from the Demand Planning module. A spare part forecastof the type Order is created when a customer order is booked. A spare part forecast of the type Manual is created when data is entered manually by the planner. Both the Manual and Forecast types of forecasts are based on experience or historical data, such as the average number of units of the family ordered per week or month over the past year.
Forecasts of the type Order are simply the sum of the quantity of the spare part for which orders have been booked with a due date of this day. The formula that is used by the system during disaggregation to break a spares family forecast down into one or more Disaggregated spare part forecasts is as follows:
Spares family forecast qty * spare part qty per = spare part forecast
Note: The date of a spare part forecast can differ from the date of the spares family forecast from which it was disaggregated. This occurs when the manufacturing calendar defined for the site associated with the spare part does not show the spares family forecast date as a working day.
Like the spares family forecasts from which they are often derived, spare part forecasts have fields for a Forecast Quantity and a Forecast Date. The Forecast Quantity represents the predicted demand for a single spare part at the Forecast Date. In addition, spare part forecasts have fields for Consumed Forecast, Actual Demand, and Note Text. Consumed Forecast is the amount of the forecast quantity that has been consumed by booked customer orders. Consumed Forecast can never exceed forecast quantity for a given record. Actual Demand represents the quantity of the spare part for which there are open orders. Actual Demand is updated by the system whenever a customer order for a spare part is placed, modified, or canceled. Actual Demand is also calculated initially immediately after installation and setup of the spares logical units to show you the existing actual demand for the parts designated as spares.