SDCA Discipline

SDCAサイクル

Standardize–Do–Check–Act

Holding the Gains

The cycle that ensures solved problems stay solved — because improvement without standardisation is just temporary relief.

Where It Began — Toyota Production System, 1950s–1970s

PDCA is the improvement cycle. SDCA is the maintenance cycle. Together, they form the complete loop that Toyota built its operational excellence on. PDCA produces a better method; SDCA converts that method into a reliable standard and holds it until the next PDCA cycle makes it better still.

Masaaki Imai, who introduced Kaizen to the Western world, stated it directly: "Without a standard, there can be no Kaizen." Toyota's Standard Work — precise documentation of the best currently known method for each task — is SDCA made operational. Every Standard Work document is dated, versioned, and posted at the point of work.

An organisation that improves without standardising is not improving. It is oscillating. The gains erode when the people who made them move on, because the improvement existed as shared memory — not as documented standard.

The Four Steps of SDCA

Standardize — Document the current best known method precisely and visibly at the point of work
Do — Train every worker to follow the standard; build adherence as a discipline, not an assumption
Check — Monitor adherence and detect deviations; check the method, not just the outcome
Act — Restore the standard when deviation is detected; initiate PDCA when the standard itself is inadequate

"Without a standard, there can be no improvement. The standard is the basis for both maintenance and improvement." — Masaaki Imai, founder of the Kaizen Institute

Why Organisations Lose Their Gains

The improvement was real — but it was not standardised, so it existed only as shared memory
When project team members leave, the knowledge leaves with them
The process reverts to its previous state because the previous state is what was written down
SDCA closes this loop: every PDCA cycle must end with an updated Standard Work document
Deviation from the standard is always a signal — either the standard needs PDCA improvement, or the worker needs support
The goal is not compliance — it is stability, from which genuine improvement becomes possible

Industry Examples

Healthcare — Virginia Mason Medical Center

Standard Work applied to IV medication administration reduced medication errors by 74% in two years. Virginia Mason became a national patient safety reference site by treating every deviation from standard as a learning signal.

Manufacturing — Alcoa under Paul O'Neill

SDCA applied to safety standards: every deviation investigated, not just serious injuries. Worker injury rate fell 90% between 1987 and 2000. Market capitalisation grew from $3B to $27.5B in the same period.

Mining — Rio Tinto Pilbara

SDCA applied across 16 mines and 1,700 km of rail: one standard per key task, monitored centrally. Achieved industry-leading cost below $15/tonne when competitors averaged $20+, through elimination of method variation.

How KaizenWorld Builds SDCA Into Your Organisation

Most improvement programs produce results that fade within 12 months. Ours don't — because we treat standardisation as the primary deliverable, not an afterthought. Every KaizenWorld engagement concludes with updated Standard Work, trained workers, and a monitoring system that detects deviation.

Standard Work development: point-of-work documentation in a format workers can actually use
Leader Standard Work: defining how managers check for adherence systematically
Deviation response training: treating every deviation as a signal, not a nuisance
Standard Work auditing: regular reviews ensuring standards remain current and followed
SDCA-to-PDCA handoff: the formal trigger that converts a recurring deviation into a PDCA improvement cycle