Preactor APS - Demand Planning, Demand Planning System & Demand Planning Software

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Using Preactor for Capacity Planning

Since its introduction in 1993, Preactor has emerged as the leader in the finite capacity scheduling software market. A key to Preactor's success is the flexibility of its modeling capabilities, including the Preactor scripting language and extensions through DLLs. In Preactor 9.3, additional functionality has been added so that it can be used for long term capacity planning.

	There are many differences between planning and scheduling applications. Capacity Planning is about deciding what, when and where to make product usually based on forecast demand, current stocks and inventory control rules. Adding this data to current sales orders provides the basis for the generation of a master production schedule, MPS. This is then used by ERP systems to provide works or shops orders as well as purchase orders for the period based on the Bill of Materials structure or BoM for each finished product. Scheduling is about deciding when to load operations that makes a product onto which resources and in which sequence based on confirmed orders with defined process routes. This, FCS in the diagram, is where Preactor is used with great benefit in many companies since it takes the orders generated by ERP and then loads them using rules to produce the schedule based on the constraints of the system. The Capacity Plan or Master Production Schedule is part of the planning process and is usually done at SKU (finished product) level. It is a "single point" schedule in
Preactor terms in that one record or operation represents the load on resources. Orders are typically based on forecast and resources represented at departments, cells, plants or factories. Operations are planned to use a certain amount of capacity in "buckets" of time, typically a week, and these buckets are set to be either finite or infinite capacity. Companies often treat MPS, Rough Cut Capacity Planning (RCCP) and Finite Capacity Scheduling as entirely different functions that require different software solutions but to Preactor they do similar things with the difference being in the level of aggregation of both demand and capacity.

Aggregation In a typical FCS application we generally want to see the activities of each individual resource, what the sequence is, when setups start and finish and what the run time periods are, taking into account shift patterns and other constraints such as tooling, operators and so on. In a capacity planning application you would typically aggregate resources into groups such as cells, shops, divisions, or plants. Why aggregate the resources? It really is a question of practicality, do you really need to know what say Machine A will be doing at 10:30 am at this time next year? Aggregation allows a simpler view of your longer-term demand/capacity relationship. So using an FCS set up, Preactor models your resources as individual machines and/or operators. In a RCCP set up resources are modeled as cells, shops and plants, while in an MPS set up resources are divisions, and multi-plant enterprises. Demand aggregation has to reflect capacity aggregation e.g. individual works orders for FCS, finished goods SKUs for MPS, as well as the appropriate time periods. At the MPS level of aggregation you cannot use information such as sequencing of orders within a time period, and thus have no impact of sequence dependent changeover times. Nor can you effectively constrain capacity by such factors such as product mix (e.g. you cannot have all 'red' products within a time period), or other factors such a tool availability. So the accuracy of the results in an MPS configuration will not be as high as in an FCS application. Graphical MPS Preactor Graphical MPS is a capacity planning and stock control example whereby we wish to examine the impact of variable demand on the capacity usage and stock levels of each SKU across more than one plant. Preactor Graphical MPS is not separate product. It is a configuration that will run on Preactor v9.3 licensed for Preactor 300 FCS or Preactor APS.
		The first stage of this example is the generation of forecast demand based on historical data. This plot shows the forecast demand over a period of one year for SKU 1 using a forecasting package. This information is then imported into Preactor. You can also at this point import or enter the expected starting stock data for each SKU as well as any other inputs during the planning period. The next stage is to generate the make orders for each SKU using the information on forecast demand as well as the stock control
rules that have been set up for each SKU. This shows some of the production data generated by the make routine. In this case we have generated an order quantity for SKU-1, Strawberry and Vanilla, for each production period, in this case a bucket of one week.
Having created the make orders to be scheduled Preactor can then be used to decide when and where to make the products based on whatever rule is required. In the example four plants are used, Plant 1, Plant 2, Plant 3 and Plant 4. Plots are used to show the capacity used in each time bucket at each plant.


The main planning screen comprises two windows. The top one is the Hot Spots Grid (HSG) and the lower one is a Multi-plot window. The HSG displays different sets of data for each SKU for each week of the planning horizon. They are color coded to highlight stock levels compared to target stock levels defined by the user either as a value or 'Days of Cover'. Blue indicates a stock level above a multiple of target stock level. Green indicates at or above target stock level. Amber indicates below target but above a stockout warning level. Red indicates at or below stockout warning level.

Preactor also generates a stock plot for each SKU. The colors of the plot matches those used in the HSG. The user has the capability to carry out 'what if' changes to capacity and targets to deal with overstocks or understocks over the period of the plan.





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