What is a Water Spider or Mizusumashi?

The activity that adds value in an assembly line is the assembly by itself so, a critical point is not to stop the line.

Share Give it a Spin!
Follow by Email

The activity that adds value in an assembly line is the assembly by itself so, a critical point is not to stop the line. Around this activity, we must try to give all the support required to develop without incident in the most efficient and organized way possible.

When we collect the cycle times of the operations of an assembly line or some assembly work stations, we encounter certain difficulties related to:

  • An excess of inventory in the position that does not allow a correct visibility of the work sequence
  • Operators spend most of their time in the collection of parts and tools that can be found close to the workplace and that can be prepared according to the principles of the 5S methodology.
  • Sometimes operators have to remember which are the right parts or the appropriate tools so this situation leads to a high risk of being wrong.

If we associate a spaghetti diagram with this study, we will see an inefficient process with an excess of operator movement and line downtime (maybe up to 30-50% of the operator’s time).

Is there a better way?

The Lean proposal to improve the performance of the workers who assemble products (assembly) is to start a water spider system, based on the basic principle of “Just In Time” (JIT), which will act in two ways:

  1. The water spider provides the necessary parts for each operator so that the latter can concentrate on the added value task of assembly
  2. The water spider assumes the non-repetitive tasks of the operator so that the work standards of the operator are perfectly defined. In this way, the waste of the assembly line (assembly) becomes more visible so it is easier to discover opportunities for improvement.

The water spider refers to the insect that moves under water with great agility. It is translated into Japanese by MIZUSUMASHI which by definition means “purify the water”. Our Western interpretation is to always keep the jobs clean and free of any element not necessary at the time of execution of the tasks of the operator.

Find a real example in this video:



My proposal is that you reflect on the possibility of applying this system in your company.