How to use it
- 1. Edit the MPSSet weekly demand for product A with the +/− steppers - the whole explosion recalculates.
- 2. Read each levelEvery item shows the classic MRP grid: gross, on-hand projection, net, planned receipts and releases.
- 3. Follow the cascadeA's planned releases become B's and C's gross requirements - offset by lead time, multiplied by usage.
- 4. Try the lot ruleSwitch lot-for-lot to fixed-order-quantity and compare orders placed vs inventory carried.
The explosion
Bill of materials
A finished unit of A needs 2×B and 1×C; each B needs 2×D and 3×C. Lead times shown per item.
Master schedule - product A
Lot-sizing rule (B, C, D)
Lot-for-lot orders exactly the net need; FOQ rounds every order up to multiples of 60 - fewer orders, more inventory.
Lead times (weeks)
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Planned orders
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Avg on-hand (units)
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Peak weekly release
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Past-due releases
Swipe each table sideways to see all eight weeks.
Try these experiments
- Raise D's lead time to 3 weeks - the release for the week-3 MPS lands in the past. MRP can plan it, the factory cannot do it.
- Switch to FOQ and compare the tiles: orders drop, average inventory jumps - the classic setup-vs-holding trade.
- Add a one-week spike to the MPS and watch it amplify down the tree: 30 extra A's become 60 B's, 180+30 C's and 120 D's - MRP's own bullwhip.
About this tool
The concept
MRP converts a master schedule into time-phased orders for every component, netting off stock and offsetting by lead time, level by level.
How it works
Gross requirements − on-hand − receipts = net; net becomes a planned receipt, released lead-time weeks earlier; releases explode into children's gross via BOM quantities.
Winning strategy
Watch the releases row, not the receipts: it is what purchasing must act on, and it goes past-due the moment cumulative lead time exceeds the schedule's warning.