Case Study in One Piece Flow

March 1, 2008
By Darren Dolcemascolo

Creating flow is one of the five principles of lean thinking. It is also considered the ideal state in manufacturing since it results in the least inventory and shortest lead-time or cycle time. In this article, I will describe a case study based on an actual kaizen event that EMS facilitated. The event dealt with a medical device company that assembles its own products (while purchasing most of the component parts from suppliers).

The tools/principles utilized in this event were as follows:

1. Standardized Work

2. One Piece Flow / Cellular manufacturing

3. 5S Principles

The current state metrics for this particular operation were as follows:

  • Average manufacturing cycle time: 10 days
  • Productivity: 10 units/person per hour
  • WIP: 5 days
  • Mode of Manufacturing: Batches of 50 units
  • Over 300 ft of product distance traveled

  • A kaizen team consisting of assemblers, manufacturing engineers, an area supervisor, and a few employees from outside the area was formed. After spending day one in training, the team began to observe and collect time data for each step in the manufacturing process. The team discovered significant waste in the process:

  • Excessive batching of work at each stage caused extra handling
  • Out of cycle work: Operators were doing their own material handling and preparation
  • Excessive WIP as a result of batching
  • Motion waste, due to improper tool and material presentation
  • Layout was not conducive to one-piece flow; there was a long distance between operations.
  • Each operator has his/her own way of performing a job step- lack of standardization.

  • Using the principles of one piece flow, standardized work, 5S, and SMED, the team instituted the following changes:

  • The team developed standardized work sheets that identified each job step and the sequence and time associated with each step. This significantly reduced the variation between operators.
  • The team developed a status and problem board that was used to communicate hourly progress (plan versus actual) as well as problems.
  • The team developed and implemented a new cellular layout that was conducive to one piece flow; it physically limited the amount of WIP between operations.
  • The team also recommended and later implemented modifications to molds that further reduced the internal setup time.

  • The improvements resulted in a 50% reduction in manufacturing cycle time, a 70% productivity improvement and a 30% reduction in floor-space used.

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