What Is Group Explosion in Scheduling?

Group explosion is the engine pre-pass that converts a routing step bound to a machine pool into a concrete nominal primary machine plus one alternate candidate per remaining member, each carrying its own pre-computed hours, immediately before machine selection runs, so the core scheduling engine never has to understand what a group is. It is the dispatcher turning "any mill" into a shortlist of the three actual mills before choosing which one gets the job.

This entry is part of the EDGEBIC by User Solutions glossary; the broader dictionary lives in the manufacturing glossary.

Why the Engine Explodes a Group

A work center group is a routing concept with no capacity of its own. The scheduler cannot book hours against a pool, because a pool is not a machine. So a group-bound step has to be translated into something the engine can actually schedule.

The engine already knows how to schedule a step that has a primary machine plus a list of alternate machines: it picks the best available one. Group explosion reuses that. Rather than teaching the engine a brand-new "group" path, the explosion reshapes the group into the primary-plus-alternates form the engine already handles. The core engine stays simpler, and pooling rides on proven selection logic instead of a parallel code path.

How It Works

Just before machine selection, each group-bound step is expanded:

• The pool's members are sorted deterministically (the designated primary first, then by priority, then by machine identity as a tiebreaker). The top of that list becomes the nominal primary stamped onto the step.
• Every remaining member becomes an alternate candidate.
• Each candidate carries its own pre-computed effective hours, reflecting that machine's speed factor and setup, so the resolver is comparing real numbers.

After the explosion, the step looks exactly like an ordinary step with alternate work centers, and the same selection strategy machinery chooses the winner. If a group is empty or cannot be resolved, the step is left unexploded and a loud warning is logged, so the failure is visible rather than a silent wrong assignment.

A Concrete Example

Group MILLING has three members: Mill-1 (baseline speed, designated primary), Mill-2 (faster), and Mill-3 (slower, simpler setup). A routing step targets MILLING.

At schedule time, group explosion sorts the members, stamps Mill-1 as the nominal primary, and creates Mill-2 and Mill-3 as alternate candidates. It pre-computes each candidate's hours from its own speed factor and setup. The step now reads, to the rest of the engine, as "primary Mill-1, alternates Mill-2 and Mill-3, with these hours each." The resolver then picks whichever member finishes first (or earliest starts, or the primary first) given real capacity. The engine never saw the word "group"; it saw three real machines with real hours.

How EDGEBIC Uses It

In EDGEBIC, group explosion runs immediately before the alternate-machine resolver on every scheduling run. It converts each group-bound step into a nominal primary plus one true-alternate candidate per remaining member, each with its own effective hours, and then the standard resolver picks the member per the group's strategy. Because the explosion is transient and re-runs each time, a not-yet-started step naturally re-shops the pool on the next reschedule against fresh capacity.

The per-member hours the explosion carries come from the group's factor-from-base rule, so speed differences are honored without the setup ever being scaled. And because the pool holds no capacity of its own, the explosion is what keeps phantom capacity impossible: the engine only ever books against real member buckets. For the wider picture, see the work center groups overview, and for how alternates work in general, what is a true alternate work center.