Sample PSM ATP Calculations

Overview
Below is a sample of the default Available-to-Promise inventory calculations currently performed by the TRG Production Schedule Manager (PSM). This sample applies to users of Time Critical Manufacturing System (TCM) enterprise management software.when PSM is determining if the required item can be manufactured by the Customer Request Date(CRD), Note these calculations are usually tailored for each installation of the PSM.

First, PSM checks the Available to Promise (ATP) for the week being requested. The Available-to-Promise function builds a table (behind the scenes) that contains all open Shop Orders representing the "supply" side of the item. Then, all open Customer Order line items for this item are gathered. These quantities represent the "demand" side for the item.

The first entry in the table is the on-hand quantity from the Item Location. Then, for each supply/demand item, the appropriate adjustment to inventory is made for that date. PSM compares the CRD and the Release Quantity in this table to determine the available inventory at the time of the CRD. If there is sufficient quantity "Available-to-Promise", no further processing is required; the customer date can be met and the new Customer Order release can be created.

Example of entries in the Available-to-Promise Table:

 Trx ATP
Starting Inventory 100 100 2/6/99 (today's date)
SO #10001 +10 110 2/15/99
COP Order #33333 -50 60 2/16/99
Our Incoming EDI Trx -20 40 2/18/99 (CRD)
COP Order #44444 -30 10 2/22/99

This example shows that PSM would have enough quantity to satisfy this demand, so no additional checking would be required.

If there is not sufficient quantity at the time of the CRD, PSM checks to see if there is a scheduled Shop Order (supply) after the CRD. If there is, PSM generates a Processing Exception Message to note that there is an open Shop Order after the CRD. This notifies the PSM user that, if possible, an existing Shop Order date can be moved up to meet the demand. Even if there is an open Shop Order, after the CRD, PSM continues with the PSM calculations.

PSM gets the Standard MRP Lead Time from the Item Reorder Point/MRP record in the TCM ERP system.

From the TCM Item Base Record, PSM identifies the Primary routing, links to the Routing Operation file, and gets the first routing operation record. PSM then gets the department and work center for this first operation and links it to the Work Center Availability table within PSM to get the first open date for the Work Center. This date will be referred to as the Work Center Availability Date. PSM calculates the Work Center Lead Time by taking the Work Center Availability Date minus the current date (exclude weekends and special dates).

From the bill of material, PSM searches for components for the incoming item number and checks each component in the Item Base record to see if it is a Purchased item. If no "Purchased" parts are found on the first level, PSM takes all of the items found, and searches for components in the Product Structure table for the next level of items.

If the purchase raw material is found, PSM checks to see if the item is in the Consigned Material table within PSM. If it is, the Purchased Part Lead Time will be zero. Consigned material is assumed to always be available.

If it is not, PSM multiplies the incoming quantity by the qty per (at each BOM level) to get the Required Material Quantity. PSM creates an Available to Promise Table for the component material by getting open PO line items for the Supply Side and SO Material Records for the demand. PSM determines if there will be enough material available by the CRD. If there is, the Purchased Part Lead Time will be zero.

If there will not be enough on hand, PSM gets the Reorder Point record for the primary vendor and gets the standard lead time. PSM assigns this value to the Purchased Part Lead Time.

PSM compares the Purchased Part Lead Time and the Work Center Lead Time. If the Purchased Part Lead Time is greater than the Work Center Lead Time, PSM adds the Standard MRP Lead Time to the Purchased Part Lead Time to get the ERP Lead Time. If the Purchased Part Lead Time is less than or equal to the Work Center Lead Time, PSM adds the Standard MRP Lead Time to the Work Center Lead Time to arrive at the ERP Lead Time for the requested release. PSM adds the ERP Lead Time to the current date to arrive at the ERP Calculated Promise Date.

PSM compares the ERP Promise Date to the CRD. If the ERP Promise Date is less than or equal to the CRD, PSM creates the release with the CRD equal to the Promised Date and the Requested Date. If the ERP Promise Date is greater than the CRD, PSM creates the release with the Request Date equal to the CRD and the Promise Date equal to the ERP Promise Date. PSM generates an exception message on the Processing Exception Report.