Ledgr/Documentation/Bills of materials

Bills of materials

A recipe for something you make: what goes into one unit, what that costs, and how far ahead each component has to be ordered. Everything the planner does downstream reads from here.

Plan.

Bills of materials is included from Manufacturing upwards. See pricing.

This is not the same as inventory assemblies.

If you are on Business or Enterprise you already have simple assemblies under Inventory — one level, build on demand. Nothing about that changes. Bills of materials is the deeper thing: many levels, planning parameters, where-used, and a cost roll-up that MRP and procurement both read.

Create a recipe

Bills of Materials → Recipes → New
Pick the product this recipe makes. A product can carry more than one recipe — an older revision and its replacement, or a variant built from different parts — so mark one of them the default. That is the one MRP plans against.
Give it a version and an output quantity
Output quantity is how many units the listed components produce. If the sensible way to write your recipe is "this makes 100 litres", say 100 rather than dividing everything by a hundred to make it read per-unit.
Add the component lines
Each line is a stock item and a quantity per output. A component may itself have a recipe — that is what makes the bill multi-level, and Ledgr follows it down.
Set the build lead time
How long the make itself takes, in days. MRP subtracts it when it works out the date a job has to start for the finished goods to exist when they are needed.
Set effective dates if the recipe changes
A recipe can be given an effective-from and effective-to date. Use it when a formulation or a supplier part changes on a known date, so planning ahead of that date uses the old bill and after it uses the new one.

Explosion & cost

The Explosion & Cost tab answers two questions at once: what does one unit actually consume once every sub-assembly is followed down, and what does it cost.

Explosion flattens the whole tree. A component that appears at three different levels is shown at each, and totalled.
Cost roll-up prices that explosion from stock cost and adds the labour and overhead on the recipe, giving a unit cost you can compare against the price you sell at.
Where-used is the same question backwards — given a component, which recipes consume it. Run it before you discontinue a part or accept a price increase.

Circular recipes are refused, not tolerated.

If A is built from B and B is built from A, exploding either would never terminate. Ledgr detects the cycle and names the products in it rather than running out of memory.

Item planning

The Item Planning tab is where each stock item is told how it should be replenished. MRP reads these and nothing else, so a blank planning record is the usual reason a planned order does not appear where somebody expected one.

Make or buy — whether a shortfall becomes a work order or a purchase.
Lead time — days from ordering to having it on the shelf. For a bought item this is the supplier's; for a made item the build lead time above.
Safety stock — the cushion you never intend to eat into. MRP plans to stay above it, not to reach it.
Reorder point and order quantity — the level that triggers replenishment and the multiple you buy in, so a plan does not ask for 7 of something sold in boxes of 12.

Use bulk source to set make-or-buy across many items at once rather than opening each one — on a first setup that is the difference between an afternoon and a week.

Issues

The Issues tab is the pre-flight check. It lists what would make a plan wrong before you rely on it: components with no planning record, recipes with no default, items marked "make" with no recipe to make them from, and lead times of zero that will quietly plan everything for today.

Fix issues before the first MRP run, not after.

An MRP run against an incomplete bill does not fail — it produces a confident plan that is missing things. The Issues tab exists so the first run is worth reading.