Work in Process
Also known as: WIP, Work in progress, In-process inventory
Work in process is material that has entered production but is not yet a finished, shippable part. In a forging shop it sits between stages — cut billets waiting to be forged, forgings waiting for heat treatment — and it is the inventory most often wrong, because it is counted as a total rather than per stage.
Work in process is material that has entered production but is not yet a finished, shippable part.
In a forging shop it is most of what is on the floor at any moment: bar cut into billets and waiting to be heated, forgings waiting for a furnace, parts out of heat treatment queued for machining. It is inventory, it has value, and it is routinely the least accurate figure in the system.
Why it goes wrong
The usual cause is treating it as one number.
A single "in production" total cannot be reconciled against anything. It does not say whether 400 pieces are waiting at forging or at machining, which are very different situations for planning. Worse, it silently absorbs process losses: if material is lost to scale, to cutting, or to scrapped pieces, a lump total simply drifts from reality without ever indicating which stage the discrepancy came from.
Held per stage, the same information becomes checkable. Each stage has an input quantity, an output quantity and a difference, and that difference is either an expected loss or a problem worth looking at. The arithmetic is what makes the number trustworthy, and it only exists if the stages are modelled separately.
Why it is where traceability breaks
Stages are precisely where material is transformed, combined and divided — one bar becomes many billets, several billets go into one furnace load. Every one of those transitions is a chance for lot identity to be dropped.
That makes work-in-process records load-bearing for traceability rather than merely useful for planning. A stage that records quantities but not the heat they came from produces accurate totals and unanswerable audits.
Draft and posted quantities
A related distinction matters in practice: whether a record has been entered or has actually moved stock. An entry being drafted, reviewed or corrected should not change on-hand quantities; only a posted entry should.
Without that separation, half-finished data entry and genuine movement look identical, and the inventory figure becomes something people learn not to trust. With it, the posted quantity is a statement about physical material and the draft is a statement about paperwork.
What it is not
Work in process is not scrap, and it is not finished goods. It also is not a measure of progress toward a customer order on its own — knowing 400 pieces are at heat treatment tells you where material is, not whether a due date will be met. That requires the routing and the schedule alongside it.
Common questions
What is the difference between work in process and finished goods?
Work in process has entered production but cannot be shipped; finished goods have completed every operation and can. The boundary is defined by the routing, not by physical appearance — a forging that still needs machining is work in process however finished it looks.
Why is work in process usually the least accurate inventory figure?
Because it is often tracked as a single total rather than per stage. One number for "in production" cannot be reconciled against anything: it hides where material actually is, and it absorbs process losses silently instead of surfacing them at the stage that caused them.
Does work in process need to be traceable to a heat?
Yes, and it is where traceability is most often lost. Stages are exactly where material is combined and split, so a stage record that does not carry the heat forward breaks the chain at the point it is hardest to reconstruct.
Related terms
- Lot Traceability — The ability to follow a defined batch of material forward to the parts made from it and backward from a part to the material it came from.
- Scale Loss — The metal lost as iron oxide when steel is heated for forging, why it has to be accounted for rather than estimated, and how it differs from cut and burning loss.
- Heat Number — The identifier a steel mill assigns to one batch of metal poured from a single melt, and the unit material properties are guaranteed against.