Multi-Process Handling

Definition

Ohno distinguishes two ways a single worker can operate multiple machines. A "multi-unit operation" is one operator running several identical machines — five lathes, say. "Multi-process handling" is different in kind: one operator runs one lathe, one milling machine, and one drilling machine — several different processes in sequence. The glossary is explicit that this shift requires workers to move "from being single-skilled to becoming multi-skilled," not simply faster at one task.

In the Book

Ohno dates his first deliberate step toward multi-process handling to 1949–1950, when as machine-shop manager he rearranged machines and "adopted a multi-process system that assigns one operator to three or four machines" as part of establishing production flow — a change he says was intended, alongside just-in-time, to overhaul a conservative production system and met real resistance from workers accustomed to single-machine, single-skill roles. The glossary entry ties the practice directly to the Toyota production system's priority on flow: because setting up flow matters more than keeping any one machine at maximum output, Toyota "tries to achieve a multi-process operation system that directly reduces the number of workers" — a worker moving with the part through several different operations rather than the part being pushed process-to-process between narrowly-skilled specialists. This connects to autonomation (Chapter 1): because autonomated machines need a human only when they signal an abnormality, a worker is freed to tend several different kinds of machines rather than babysitting one.

Why It Matters

There's a real difference between "faster at one thing" and "capable across several adjacent things," and only the second lets a single person follow work across a process boundary instead of parking it in a queue for the next specialist. Multi-process handling trades depth-of-specialization for continuity of flow: fewer handoffs, less queueing between stages, and workers who understand the whole sequence rather than one narrow slice of it. The same tradeoff shows up wherever work is organized into narrow specialist roles versus generalists who can carry a task across several stages — the generalist version reduces coordination overhead at the cost of requiring broader (and harder-won) skill in each person.