Five Whys

The practice of asking why repeatedly whenever a problem is encountered in order to get beyond the obvious symptoms to discover the root cause.
For instance, Taiichi Ohno gives this example about a machine that stopped working (Ohno 1988, p. 17):
1. Why did the machine stop?
There was an overload and the fuse blew.
2. Why was there an overload?
The bearing was not sufficiently lubricated.
3. Why was it not lubricated?
The lubrication pump was not pumping sufficiently.
4. Why was it not pumping sufficiently?
The shaft of the pump was worn and rattling.
5. Why was the shaft worn out?
There was no strainer attached and metal scraps got in.


Without repeatedly asking why, managers would simply replace the fuse or pump and the failure would recur. The specific number five is not the point. Rather it is to keep asking until the root cause is reached and eliminated.

The Five Ss

Five related terms, beginning with an S sound, describing workplace practices conducive to visual control and lean production. The five terms in Japanese are:
1. Seiri: Separate needed from unneeded items—tools, parts,
materials, paperwork—and discard the unneeded.
2. Seiton: Neatly arrange what is left—a place for everything
and everything in its place.
3. Seiso: Clean and wash.
4. Seiketsu: Cleanliness resulting from regular performance
of the first three Ss.
5. Shitsuke: Discipline, to perform the first four Ss.

The Five Ss often are translated into English as Sort, Straighten, Shine, Standardize, and Sustain. Some lean practitioners add a sixth S for Safety: Establish and practice safety procedures in the workshop and office.


However, Toyota traditionally refers to just Four Ss:
1. Sifting (Seiri): Go through everything in the work area, separating and eliminating what isn’t needed.
2. Sorting (Seiton): Arrange items that are needed in a neat and easy-to-use manner.
3. Sweeping Clean (Seiso): Clean up the work area, equipment, and tools.
4. Spic and Span (Seiketsu): The overall cleanliness and order that result from disciplined practice of the first three Ss.
The last S—shitsuke (sustain)—is dropped because it becomes redundant under Toyota’s system of daily, weekly, and monthly audits to check standardized work. Whether four, five, or six Ss are used, the key point to remember is that the effort is systematic and organic to lean production, not a “bolt-on” stand-alone program.

 #Five S, #Lean manufacturinG

The FIFO

The principle and practice of maintaining precise production and conveyance sequence by ensuring that the first part to enter a process or storage location is also the first part to exit. (This ensures that stored parts do not become obsolete and that quality problems are not buried in inventory.) FIFO is a necessary condition for pull system implementation. The FIFO sequence often is maintained by a painted lane or physical channel that holds a certain amount of inventory. The supplying process fills the lane from the upstream end while the customer process withdraws from the downstream end. If the lane fills up, the supplying process must stop producing until the customer consumes some of the inventory. This way the FIFO lane can prevent the supplying process from overproducing even though the supplying process is not linked to the consuming process by continuous flow or a supermarket. FIFO is one way to regulate a pull system between two decoupled processes when it is not practical to maintain an inventory of all possible part variations in a supermarket because the parts are one-of-a-kind, have short shelf lives, or are very expensive but required infrequently. In this application, the removal of the one part in a FIFO lane by the consuming process automatically triggers the production of one additional part by the supplying process.