What Is a Sequence Number in a Routing?

A sequence number is the value that orders the steps of a routing, telling the schedule which operation comes first, second, and so on. It is the backbone of a routing: before the engine can decide when each operation runs, it needs to know the order they run in, and the sequence number provides it. Steps are conventionally numbered 10, 20, 30 rather than 1, 2, 3, leaving room to insert later without renumbering. EDGEBIC by User Solutions reads sequence numbers to place every operation in order before it schedules a single date.

How it works

Each step in a routing carries a sequence number, and the engine sorts the steps in ascending order of that value. Step 10 comes before step 20, which comes before step 30. That order is what lets the engine build the chain of operations, so machining precedes assembly and assembly precedes final inspection.

The gap convention, numbering by tens rather than ones, exists for a practical reason: insertion. When you later need an operation between two existing steps, you give it a number in the gap, such as step 15 between 10 and 20. It slots in without disturbing anything else. Number the routing 1, 2, 3 and there is no room, so a single insertion forces a renumber of every step downstream.

Sequence numbers set order, not dates. The calendar placement of each step comes from capacity, setup, run time, and any queue or transit delay, layered on top of the ordering. The sequence tells the engine what must come before what; the schedule turns that into start and finish times.

A concrete example

Think of a recipe card written with room to grow. A cook numbers the steps 10 (mix the batter), 20 (bake), 30 (frost). Later they decide the cake needs to cool before frosting, so they add step 25 (cool for an hour) between baking and frosting. Nothing else on the card changes; the new step simply falls into place because the numbers had gaps.

Had the cook numbered the steps 1, 2, 3, adding the cooling step would have meant crossing out "3. frost," writing "3. cool," and "4. frost," and hoping nothing referenced the old numbers. The gap-based numbering avoids all of that.

In the plant, a routing numbered 10 (mill), 20 (drill), 30 (deburr) reads in that order every time. Insert a wash step as 15 and it runs after milling and before drilling, with no other change. The engine schedules them in ascending order, exactly as written.

How EDGEBIC uses it

Sequence numbers order the steps of every routing, and they work hand in hand with the explicit predecessor links that connect one step to the next. Building those ordered, linked steps is the subject of how to sequence operations with dependencies in EDGEBIC. When steps land in an order you did not expect, the causes and fixes are in steps scheduled out of sequence.

Because ordering comes before dating, a clean sequence keeps the whole schedule readable: the engine walks the steps in order, applies capacity and any delays, and produces dates that respect the routing. A muddled sequence, such as two steps sharing a number, is where out-of-order surprises begin. When a routing visits the same machine more than once, the repeat visits are kept apart by a work center occurrence suffix rather than collapsing into one confused step.

The related idea of steps meant to run at the same time rather than one after another is captured by independent parallel processing, a companion glossary term. For the wider vocabulary, see the manufacturing glossary, and to see sequenced routings inside a live plan, explore EDGEBIC.