Waterspiders and Mizusumashi: What Nature teaches us about Lean Manufacturing
Do you know that lean factories use a principle given by nature to supply the production line with material? How can that be implemented within 3 steps? – Mizusumashi / waterspider. The Mizusumashi is the Japanese term for waterspider. Hence both terms are often found in literature. But what is the meaning of these terms?
The waterspider symbolizes a person able to work on the surface between water and air. In terms of a production plant it is the thin line between production and logistics with the ability to swim and move quickly to all spots whenever required.
Lean factories use the Mizusumashi or waterspider to feed the line highly frequently but with small quantities. Higher line dynamics gives the possibility to produce more accordingly to the customer’s demand.
Why should any Production switch to a Mizusumashi principle?
The Mizusumashi is the core element of a lean production system like the TPS from Toyota. He not just brings material to the line, he is responsible to provide all information needed at the line to produce according to the customer need and demand. That includes the production plan.
When delivering all parts per route to the line the process becomes much more transparent. Thus leading to a far better control of quality and process.
How do we implement the Waterspider?
To implement the Mizusumashi three elements have to be defined.
- Line-side packaging – Though devices exist to bring parts in big boxes to the line most packages have to be in small standardized boxes – as the frequency of delivery is high the quantity is low. Handling big boxes will cause to high stock level line-side. Better: Use small packages with the quantity equal to the quantity of the finished-goods palette/box (i. e. you produce your product and place 15 products finally on a palette of finished goods. Than bring 15 parts per box of raw material to the line. You will then have a full palette of finished goods and empty boxes of raw material).
- The Mizusumashi device – The Mizusumashi or waterspider is no forklift! Use a device which allows you to handle multiple smaller boxes at once similar to a train with several wagons behind.
- Route and timetable – create routes for the Mizusumashi starting at the line. The finished-goods palette triggers the Mizusumashi. He first takes the full palette and prepares an empty palette/customer packaging. Next he needs the information of the upcoming customer palette. Therefor he is informed by a Heijunka box or any other production planning principle. To not let the production line stops, make sure to have two boxes of each material line-side (two-box-principle). The Mizusumashi then is always one cycle ahead. If feeding several lines prepare a timetable similar to a bus timetable. If feeding one line, the cycle time of the Mizusumashi is according to the cycle of a full customer palette.