The PDCA wheel held in place on a slope by a wedge is a common representation of how standards are essential to sustains continuous improvement. On the one hand, this is intuitive and easy to demonstrate. On the other hand, it’s insufficient to guide us in developing systems and mechanisms for sustaining improvement.
Visually, the position of the continuous improvement wheel on the inclined plane seems precarious. There is the possibility that we roll the ball uphill, and it rolls back down because we fail to put a proper standard in place. Even when the wedge is present, a ball with enough momentum may be able to roll over it and down the slope. Wheels can fall over or roll sideways.
The idea of the wedge or wheel block as the method to sustain improvement comes from the Japanese term hadome (歯止め). It means “brake” or something that stops movement or action, either mechanically or due to policies and governance. The nuance is to lock a thing into place.
In the eighth step of the Toyota Business Practice (TBP) problem solving method we often talk about standardizing, sustaining and sharing the result of the improvement. But if we fail to grasp the spirit of hadome we may fail to meet the intended purpose of this step. Unlike wheeled vehicles, organizations wishing to sustain improvement need more than standards to prevent us from slipping backwards.
A ratchet is a better metaphor for a system of standards, visual controls, huddle meetings, gemba walks, and other daily activities to sustain improvement. These are some of the components of a Daily Management System. A ratchet allows continuous motion in only one direction while preventing motion in the opposite direction. When we talk of “ratcheting up” something we increase force, torque or achievement by a fixed degree. Due to the nature of a ratchet, we expect that there will be no decrease or slipping back.
In the figure above the ratchet features a gear (1) which creates the progress or motion. The pawl (2) provides the braking and prevents backwards motion. These two must be linked together, in this example by being mounted on a common base (3). A ratchet is not a separate wheel and wedge, but a set of parts that always operate together as a system.
When we turn the ratchet mechanism, the pawl automatically clicks into place and holds the gear. We don’t need to hold the PDCA wheel with one hand while we move the standards wedge into place with the other hand. Wouldn’t it be great if we could apply the same principle to organizational progress?
The chart below illustrates year-on-year improvement when daily management, long-term strategic (hoshin) management, and continuous improvement (kaizen) are paired together as a lean management system.
This is why leaders can’t delegate kaizen to teams, engineers, or a promotion office. This is why hoshin fails without a daily management system. This is why leaders need to get into the weeds to confirm that their big initiatives are ratcheted into place through daily checks, problem escalations and problem solving. If a leader doesn’t get this, put a ratchet in their hand to see if they figure it out.