Page 72 - Lean six sigma demystified

Chapter 2 Lean Demy S tifie D 51

Redesign for One-Piece Flow

One of the goals of Lean is to reduce the size of a batch or lot to one. While
this may not always be possible, small lots and quick changeover approach it.
In the beginning, changeover took an hour or more. Now, it’s 3 minutes or less.
What are the benefits of one-piece flow?
1. Builds in quality
2. Creates flexibility
3. Increases productivity

4. Frees flow and space
5. Improves safety
6. Improves moral
7. Reduces inventory

Here’s the mindset shift for one-piece flow.
From. Big batches
To. Single pieces or small batches

The trick is eliminating all of the delay between value-adding steps and lin-
ing up all of the machines and processes so that the product or service flows
through the value channel without interruption. Mass production and large
batches ensure that the product will have to sit patiently waiting for the next
step in the process. The mental shift required to move from mass production
to Lean thinking is to focus on continuous flow of small lots.

Common Measures of Flow
• Lead (or cycle) time. Time product stays in the system

• Value-added ratio. (Value-added time)/(lead time)
• Travel distance. Of the product or people doing the work
• Productivity. People hours per unit; number of handoffs
• Quality rate. Or first-pass yield

Tesco, a grocery store chain in the United Kingdom, reduced stock outs
dramatically while slashing in-store inventories by more than 50%. In-store
inventories are one-eighth of the U.S. average (Lean Thinking, Womack &
Jones).