How to identify where work in progress is waiting

A job can spend minutes being processed and hours waiting for the next operation.

For manufacturers, understanding that difference is a useful starting point for improving production flow. Before adding equipment, changing the layout or increasing staffing, establish where Work-In-Progress (WIP) accumulates, how long it remains there and what prevents it from moving.

The first task is to make the journey between production stages visible.

Look at the spaces between operations

Work in progress includes materials, components and partially completed products that have entered production but are not yet finished.

Some waiting is planned. A process may require cooling, curing or enough material to complete a batch. Other waiting reflects an interruption: a machine is unavailable, an inspection has not happened, transport has not arrived or the next team lacks the information needed to proceed.

Start by looking at:

• Queues before machines or workstations.
• Material awaiting inspection or approval.
• Containers waiting for collection or transport.
• Partially completed jobs held between departments.
• Rework awaiting a decision or another operation.

A large queue deserves investigation, but its size alone does not explain the cause. It might reflect a temporary surge, planned batching or a recurring constraint downstream.

Observe how the queue changes across shifts and production cycles. Does it clear, remain stable or continue growing?

Separate processing time from waiting time

Processing time is the time during which an operation is actively being performed. Waiting time is the time work remains pending before it can proceed.

Consider a job that arrives at a workstation at 09:00, begins processing at 11:00 and finishes at 11:20. It spends two hours waiting and 20 minutes being processed.

If it remains beside the workstation until collection at 12:00, another 40 minutes passes after processing. That delay has a different cause and potentially a different remedy.

For each stage, distinguish:

• Arrival: when the work reaches the queue or staging area.
• Processing start: when the operation actually begins.
• Processing finish: when the operation is completed.
• Departure: when the work leaves for the next stage.

Record transport, setup and required process holds separately where they matter. Agree these definitions before comparing teams or shifts.

Physical presence does not necessarily mean processing. A container beside a machine may be waiting, actively involved in production or holding completed work.

Measure before deciding where to intervene

Begin with one product family or route through production. Trying to map every movement at once can make the investigation harder to interpret.

Follow a representative set of jobs across several shifts or production cycles. Record:

Time at each stage. Measure waiting before processing, processing duration and the delay between completion and departure.

Queue size and age. Count the jobs or containers waiting, but also identify how long the oldest work has remained there. Use consistent units: container counts can be misleading when quantities differ.

Variation. Compare typical waiting times with the longest delays. An average can conceal jobs that repeatedly become stuck.

Output and workload. Compare the work arriving at a stage with the work completed. A growing queue may indicate that arrivals are exceeding effective capacity.

Reasons for delay. Record whether work is waiting for equipment, labour, transport, inspection, material, instructions or a scheduling decision.

Operational consequences. Check whether the delay affects delivery dates, starves the next operation, consumes floor space or creates extra handling.

Use these observations to choose an intervention. Faster collection may help when completed work waits for transport. It will do little if the next operation cannot accept more work.

Likewise, increasing the speed of an upstream operation can enlarge a queue if the downstream constraint remains unresolved.

Where location data can help

Location data can make the physical movement of work easier to observe.

When a job is reliably associated with a tracked container, pallet or carrier, its movements can help establish when it enters and leaves defined production areas. Repeated observations can reveal long stays, recurring queues and unexpected routes.

This can reduce reliance on occasional manual checks and help answer questions such as:

• Where was the tracked work last observed?
• How long has it remained in this area?
• Which handovers regularly take longer?
• Does waiting vary by shift, route or product family?

The usefulness of these observations depends on tracking coverage, update frequency, zone definitions and the accuracy of the association between the tracked carrier and its contents.

A carrier’s location is only useful as a record of WIP when you know which work it contains. That association must be updated when contents change, split or move to another carrier.

Location needs production context

Location data can show that work remained in an area. It usually cannot explain, on its own, whether that work was being processed or why it was waiting.

To interpret the movement, combine it with information such as:

• Job identity, product type and quantity.
• Planned route and next operation.
• Actual operation start and completion.
• Machine availability and downtime.
• Inspection, quality hold and rework status.
• Shift calendars, priorities and planned batch rules.

For example, a long stay in an inspection area might reflect a queue, an active inspection or a quality hold. Each requires a different response.

Connecting physical movement with production records helps turn an observation—“this job stayed here”—into a useful operational question: “what prevented this job from progressing?”

Start with one measurable change

Choose a recurring delay with a clear operational consequence. Confirm the cause with the people responsible for the work, then test a specific change.

Compare waiting time, queue age and completed output before and after the change under reasonably similar conditions. Check that the improvement has not simply moved the queue elsewhere.

The aim is to help work progress through the whole route more reliably.

Five questions to ask about your WIP

☐ Where is work accumulating? Identify the stages, queues and handovers where it regularly waits.

☐ How long is it waiting? Separate arrival, processing start, processing finish and departure.

☐ What is preventing it from moving? Confirm the reason using production records and discussions with the team.

☐ What does the delay affect? Check delivery dates, downstream work, floor space and handling.

☐ What evidence would justify a change? Establish a baseline and decide how you will measure the result.

Discuss your production flow with BlueGPS

Start with one production route and the questions you need to answer. Discuss with BlueGPS where location data could help make WIP movement visible, and which production information would be needed to interpret it.