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Calculate Planning Data

The Calculate Planning Data dialog box is used to automatically calculate and update the planning parameters for selected parts.

The purpose of the calculation is to facilitate calculation and update of planning parameters, safety stock level, order point, and lot size based on part data, using the Wilson formula.

Data used in the calculations

When calculations are performed, the data used are retrieved from different places in the system. The system retrieves the following information from the inventory part record:

• Service Rate (%); used for calculation of safety stock level.
• Inv. Interest (%); used for calculation of economic lot size.
• Setup Cost; used for calculation of economic lot size.
• Predicted Yearly Consumption; used for calculations when the part is not qualified to use the statistics.

If Commodity Group 2 is specified for the inventory part, the system will use the value in the Min Periods field in the commodity group setup. This value is used to control whether the statistical data or the predicted yearly consumption will be used when performing the automatic calculation of planning data. The value in the Min Periods field is the shortest period the part must have been active before the statistical data is used. If the part has been active fewer periods, the predicted yearly consumption will be used. The default value for the column is three periods. If no commodity group 2 is entered for the inventory part, the system will use three periods in calculations, as default.

Service rate, inventory interest, setup cost, and min periods are all controlled by commodity group 2, which is specified in the inventory part record.

The system will retrieve the No of Periods for Plan Data Recalc parameter, which is used to control the number of periods the calculations are based on. The parameter is set in Parameters for Distribution and Manufacturing window. The parameter is used as default in Calculate Planning Data, where you can change it before you start the calculations.

The statistical data that is used in the calculation can be viewed in On Hand Develop per Period. Please note that the data is aggregated per period and not on individual issues.

Calculations

Depending on the type of calculation, inventory parts with different planning methods are subject for calculations. You must have enabled at least one of the automatic update functions. These functions are safety stock, order point, and lot size.

Calculation of Safety Stock

The safety stock is calculated for all planning methods.

Safety stock (pieces) = Safety factor [-] * standard deviation for demand (pieces/period) * square root of part lead time (period)

• The lead time is retrieved from the inventory part record, purchase or manufacturing lead time depending on part type.
• The safety factor is retrieved from the service rate connected to the inventory part. Here the normal standard distribution is used to define the service rate and the safety factor. The service rate is considered as the probability and the safety factor is considered as the standard score of normal standard distribution. It is also possible to retrieve the safety factor for a given service rate by using the standard Excel function NORMSINV(Probability).

Note: The safety stock will not be updated if the predicted yearly demand is used, as standard deviation is zero because of constant demand. Also note that if lead time is zero, the safety stock will be zero.

I will be using both of these recommendations, Very helpful. thank you!