This question is a little different then some in that it asks about the connection between a group of Japanese words. Not every organization is enthusiastic about learning new Japanese words as the lean lexicon is complex enough. Actually these are really very old words, and both ringi-sho and nemawashi are not specific to Toyota, but to Japanese management more generally. Anyone who was studying Japanese management back in the 1980s when the quality movement was in full gear learned these concepts–though in the abstract apart from a system.
As you will see from the answers from some of my colleagues with direct experience at Toyota ringi was a formal process of making a proposal, generally for a capital purchase. And in Japan personal stamps are used to vote. It is used across industry, service, and government and goes back to ancient traditions. Within Toyota it is part of the broader philosophy of respect for people and continuous improvement.
Ringi is the formal approval process that is related to nemawashi. Nemawashi is preparing the soil to plant the tree. Ringi is a formal process of writing up a proposal–could be an A3–and bringing it from person to person to get their feedback and ultimately approval. Sometimes the formal Ringi process is used and sometimes not, but nemawashi still means the person leading the effort meets with the people effected and management prior to actually formally presenting the proposal. There is usually one individual responsible who is ushering the proposal through and modifying it based on feedback. The reason it is usually an individual is because “one person should be accountable or nobody is accountable.” The goal is both to get many different eyes on the problem, and so that when you get to the formal approval stage there is buyin and the meeting itself is a rubber stamp. A large meeting is not a great place to have a deep discussion about issues that involved integrating complex data analysis.
The A3 is simply a way to visually document the thinking process that follows PDCA. A proposal A3 would be used to formally propose something, and ringi might be involved, particularly for capital projects.
In a broader sense, the use of ringi, nemawashi, and A3 as part of a system reflect a number of core beliefs within Toyota:
1. The problem solving process will be better in quality and buy-in if we get broad input and involvement.
2. An individual should be responsible and is developed by leading a proposal or problem solving process learning to listen, integrate broad inputs, and to be persuasive based on the facts.
3. It is best to avoid embarrassing situations in a public meeting where the presenter is not prepared and it is even worse to waste the time of a large group of people.
4. Planning and preparation based on deep thought and analysis are critical before we actually begin any action.
This would happen prior to a meeting, kaizen event, or launching of a project and can continue at various points in the process. It is not simply getting people together for an event or meeting but happens in preparation for that. As an example, at the Toyota Technical Center in Michigan, decades ago, they created formal courses on nemawashi, problem solving, and A3 when they realized the American managers were not well educated in these. They put it in this sequence: nemawashi was a prerequisite to practical problem solving which was a prerequisite to A3.
Last time I heard about Ringi was talking to a former TMMK employee who said: ”I used to hate those damn Ringi.” It can be frustrating when it seems like a lot of wasted effort for a project with an obvious payback. Yet many more people I have known at Toyota marvel how going through ringi and/or nemawashi, in retrospect, greatly improved the process and led to a better result.