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Demand, Supply and Planning

MRP takes demand, explodes it through the structures, nets off stock and what is already coming, and proposes planned orders: what to make or buy, how many, and when to release the order. It suggests and never acts. A planner reviews the planned orders on the Production console, firms the ones to keep, and converts them into work orders or purchase requisitions.

Where to find it

Architect Panel → ERP - Operations:

  • Production — the console: the Planned orders (MRP) and Demand tabs
  • Demand — the demand MRP plans against
  • Supply — purchase supply already on order
  • Structures — the read-only Requirements preview

Admin Panel → Inventory & Production:

  • Production — the same console for planners

What MRP reads

  • Demand up to the horizon. Past-due demand counts as due today. Demand is entered on the Demand tab; sales orders do not feed it automatically.
  • Open work orders: their remaining output is supply and their remaining components are demand.
  • Purchase supply: committed purchase orders, relieved when an order is closed or cancelled, and planned buy orders already converted to a pending requisition.
  • Firm planned orders, which count as supply.
  • Stock that can be netted, less safety stock.
  • Planning settings from the item: lead time, safety stock, lot sizing, reorder, minimum and maximum quantities, and make or buy (an item with a structure is made unless it says otherwise).

Lot sizing is Lot-for-lot (exactly the net requirement), Fixed order quantity (multiples of the reorder quantity) or Min / max (up to the maximum), never below the minimum order quantity. The due date is the date of the shortfall; the release date is the due date less the lead time.

Entering demand

  1. On Production, go to Demand.
  2. Under Add demand, enter the Item, Quantity and Needed by, optionally a Location, and choose the Source: Forecast, Customer order, Safety stock or Manual.
  3. Click Add. Demand shows under Demand MRP plans against; Remove takes it out.

Running MRP and working the plan

  1. Go to Planned orders (MRP), set Horizon (days) (1 to 730) and Location, and click Run MRP. Each run replaces the earlier unfirmed planned orders; firm and converted ones are kept.
  2. Review the list: Item, Type (Make or Buy), Order qty, Net need, Due, Release by (a Past due pill means it is already late), Level, Status and Pegged to / exception.
  3. Click Firm on orders you want kept as they are.
  4. Click Make work order on a make order or Raise requisition on a buy order. Use Convert selected, Firm selected or Cancel selected for many at once (up to 200).

A converted row shows the work order or requisition it became. A buy order becomes a purchase requisition, never a purchase order directly; the requisition then goes through Purchasing (see Transactional Documents). Nothing runs MRP on a schedule: it runs when someone clicks Run MRP.

On the Structures console, the Requirements tab runs the same calculation as a read-only preview, with Open the MRP workbench to go to Production.

What goes wrong

  • "Release date D is already past - expedite or reschedule.": the lead time cannot be met.
  • "Plan between 1 and 730 days ahead."
  • Nothing to plan: there is no demand inside the horizon, or stock and open orders already cover it.
  • MRP suggests buying what is on order: the purchase order is not committed yet, so it is not supply.
  • Surprising suggestions: usually stock accuracy, a lead time, or a structure date. Treat the first runs as a data-quality exercise.

Worked example

A planner adds a forecast of 500 pump assemblies needed by 15 December and runs MRP for 90 days. MRP proposes a make order for 500 assemblies releasing on 1 December, and, one level down, a buy order for 800 seals (1,000 needed, 200 on hand) with a 21-day lead time releasing on 10 November. They firm both, convert the seals into a requisition for the buyer, and convert the assemblies into a work order nearer the release date.

Recommendations

  • Fix stock accuracy before trusting MRP.
  • Enter achieved lead times, not quoted ones.
  • Firm what you intend to keep, so the next run does not replace it.
  • Run MRP in parallel with your old method for a cycle or two first.