What Is Queue Time in Manufacturing Scheduling?

Queue time is a fixed buffer of hours inserted between two sequential operations to allow for staging, inspection, cooling, or waiting, and it is shift-aware: the hours count only while a work center's shifts are active. Nights, weekends, and holidays never consume the buffer. That makes queue time represent real elapsed working time rather than raw clock time, so a buffer set on Friday afternoon carries over correctly into Monday.

EDGEBIC by User Solutions walks the shift calendar to consume queue hours, so you never have to reason about overnight gaps yourself. This article defines the term and its neighbors. The full composition order, where queue, flow, and transit interact, is in how EDGEBIC handles queue and transit times.

How It Works

You set queue time as a number of hours on a routing step. After that step finishes, the engine holds the next step's earliest start until the queue hours have elapsed. The consumption is shift-aware: the engine walks forward through the work center's active shifts, subtracting queue hours only from time the plant is actually open.

The result is that a queue buffer never gets eaten by idle time. Set four hours of queue starting at 14:00 on a Friday with an 08:00 to 16:00 shift, and the engine consumes two hours that afternoon, skips the overnight and weekend, and consumes the remaining two hours starting Monday 08:00. The buffer represents four real working hours, wherever they land on the calendar.

Queue time is distinct from the other gaps. It is not setup time, which is machine preparation counted as part of the operation. It is not transit time, which is whole-day travel to an outside process. And when a step also carries a flow overlap, the flow value replaces the queue result, so the two should not sit on the same step.

A Concrete Example

Think of a dentist's fifteen-minute gap between appointments so the hygienist can clean the room. No one is treating a patient during that gap, but the next appointment cannot start until it passes. Queue time is that gap, scaled to working hours.

Take a drilling step that ends Monday 14:30, feeding an assembly step, with a four-hour queue for inspection and an 08:00 to 16:00 shift. The engine starts consuming queue at 14:30. It has ninety minutes left in Monday's shift, so it uses those, leaving two and a half hours. The overnight gap does not count. Tuesday 08:00 it resumes, consumes the remaining two and a half hours, and lands at Tuesday 10:30. Assembly cannot begin before Tuesday 10:30. The overnight hours between Monday 16:00 and Tuesday 08:00 never touched the buffer.

Where Queue Time Sits in the Sequence

Queue time is the first of three gaps the engine can apply between two operations, and the order is fixed. Queue time is computed first, walking the shift calendar to hold the downstream start by its working hours. A flow overlap, if set, is computed next and replaces the queue result, which is why queue and flow should not sit on the same step. Transit days, if set, are added last, after queue and flow, to model parts leaving the plant.

Knowing that order lets you stack gaps deliberately. A step can carry a queue for on-site inspection and then a transit for an outside vendor, and the two combine predictably: the parts finish the operation, wait out the shift-aware inspection queue, then start their day-based transit from there. Because each gap has a defined place in the sequence, you can reason about a routing that mixes waiting, overlap, and travel without guessing how they interact. The one combination to avoid is queue plus flow on a single step, where the flow value silently wins and the queue you set has no effect.

How EDGEBIC Uses It

Queue time is a field on a routing step, and the engine applies it as the first gap in the sequence between two operations. The Gantt shows the downstream step held back by the buffer, and because the arithmetic is shift-aware, the held start always lands on real working time.

Queue time composes with transit and flow in a fixed order, so you can stack an inspection queue and an outside-vendor transit on the same step and know exactly how they combine. The manufacturing glossary covers the related terms, what is transit time explains the day-based sibling, and how to add queue time before an operation gives the configuration steps.