WIP Tracking: Know What Is on the Floor Without Walking It
Work in process, WIP for short, is the money your factory has already spent that is not yet a sellable product: material drawn from stores, labor logged, machines fed, and nothing to ship. A surprising number of managers learns how much of it exists only when a customer calls about a late order. WIP tracking exists to answer two questions about all of it: where is order X right now, and is it moving? If answering those takes a walk across the floor and three conversations, this article is about the fix.
Work in Process Is Money Parked on the Floor
Every unit sitting between operations carries raw material cost and conversion cost already sunk into it, and it earns nothing until it ships. Worse, WIP hides problems: a queue of a thousand units in front of a slow station can absorb a defect for days before anyone sees it. That is why the oldest advice in production, keep WIP low and visible, is also the hardest to follow without a system. Queues grow quietly, one batch at a time.
The Question a Manager Actually Asks
Not utilization, not OEE by line, at least not first. The question is: where is order PO-4471 right now, and will it make Friday? A useful WIP tracking setup answers that in one lookup: which operation the order is at, how long it has been there, how many units are done against the plan, and whether anything is actively moving. The reports, the dashboards, the month-end numbers are all downstream of answering that one question quickly.
What WIP Tracking Has to Capture
Four things, per operation, per order:
- Status: which operation the order is at now, and whether that operation is running, paused, or waiting.
- Timestamps: when the order arrived at the operation and how long it has sat there.
- Quantities: units done versus units planned, including scrap, so remaining work is arithmetic instead of memory.
- Last touch: who worked on it last, and from which terminal, so a question about a count has an owner.
Pauses belong in the log with reasons, because a paused order with no reason is how a two-hour stoppage becomes a two-day discovery.
Why Terminal-Side Capture Beats End-of-Day Entry
The alternative to capturing events at the terminal is reconstructing the day at five in the afternoon, and reconstruction has a known failure mode: it flatters the day. Quantities get rounded up, pauses get forgotten, and the record becomes a story rather than a log. Terminal-side capture inverts it: the operator confirms a start, keys quantities as they happen, and records a pause with its reason while the reason is still true. This is the same argument as the shift from paper travelers to a digital logbook, with one addition: an append-only log cannot be quietly corrected later, so the record stays honest even when the afternoon went badly.
The Payoff: Bottlenecks Show Up in the Queue
When every operation reports its state, the bottleneck stops being a surprise at shipping and becomes a visible stuck operation. Nine orders queuing in front of operation 30, the oldest waiting two days, is the constraint wearing a name tag. You can staff it, rebalance it, or reschedule around it, decisions the schedule board makes concrete by showing capacity against the queue. Without WIP visibility, the same information arrives as a missed delivery and an apology, which is the usual output of spreadsheet-driven planning (covered in MES vs Excel scheduling).
Voltrus MES works exactly this way. Work orders are dispatched to station terminals, and the terminal writes an append-only production log: starts, quantities, pauses with reasons, checklist results, completions, every entry tied to the operation. The schedule board rolls that up into live WIP, so where is order X becomes a lookup instead of a walk. How this layer relates to the books is in MES vs ERP.
Frequently Asked Questions
Does WIP tracking need barcode scanning?
It helps, but it is not the requirement. The requirement is that work starts at a terminal that already knows the order, which is what dispatch gives you. Scanning makes handoffs faster; it does not create the record.
Is this not what our ERP production module does?
An ERP knows what was planned and what someone entered later. WIP tracking is about the actual: what the floor did this hour. The two pair well but are not interchangeable, as we describe in the ERP comparison above.
How much WIP is too much?
There is no universal number, but there is a reliable symptom: when a queue is big enough that a defect can hide in it for days, it is too big. Get visibility first, then shrink the queues you can finally see.
Can we keep using the whiteboard?
For a snapshot, yes. A whiteboard tells you what someone believed at eight in the morning. It cannot answer is it moving, because nothing on it updates when the floor does.
Dispatch to the Terminal, Not the Whiteboard
Voltrus MES is live: work orders dispatched to station terminals, every event logged, WIP visible live. See what ships today.
See Voltrus MES