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Purchase Planning Lead TIme

  • 1.  Purchase Planning Lead TIme

    Posted Nov 19, 2020 06:30 PM
    Does GP use calendar days, work days or a shop calendar to determine PO release or promise dates. We use MRP and struggle as we are just in time made to order mfg.  We want to make sure that all of our teams are speaking the same language.

    If a supplier has a 90 day lead time we put 90 days in purchase planning lead time. Wil this calculate out to be approximate  3mth window or does it only use only work days and therefore will calculate out to 4.5 month window (5 day weeks).  Or is this all determined on the MRP shop calendar.

    Sabrina Burtlow

    Academy - Online Interactive Learning from Experts

  • 2.  RE: Purchase Planning Lead TIme

    Posted Nov 20, 2020 07:21 AM
    Hi Sabrina.
    I believe there is a setting that controls this.  Under Manufacturing >> Setup >> System Defaults >> MRP.  In the upper left you'll see a drop down called "Down Days Constraint".  This will tell MRP if you want release dates to consider the shop calendar down days for None of your items, just Made items, just Buy items, or Both.

    Andrew Kennedy
    Principal Consultant
    Seven Hills OH

    Academy - Online Interactive Learning from Experts

  • 3.  RE: Purchase Planning Lead TIme

    Posted Nov 20, 2020 11:17 AM
    Hi Sabrina,

    If you have a test environment, please test the settings. We use MRP extensively and use calendar days for all purchased items . This is industry practice for many manufacturers. The MRP down day constraint determines if an item's release date for MRP-planned orders will fall on a down date. I've included an example of settings and a purchased item showing the due and release dates. The shop calendar if 5 working days M - F.

    We tested this originally to ensure it handled the lead-times correctly, providing a release date on a work day but using the calendar lead-time. If the lead-time calculation fell on a down day, the release day backs up to the 1st prior workday.

    Hope this helps,


    Down Day Setting for Bought Items

    Calendar Days with down day constraint

    Keith Paul
    VP Business Management Systems
    UNICOM Engineering, Inc.
    Plano TX

    Academy - Online Interactive Learning from Experts

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