Page 359 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

Design and Improvement of Service Processes—Process Management 319

Cell

Raw materials

Products

Figure 10.5 A Typical Flow Chart for Cellular Manufacturing

There are three types of job flow patterns in cellular manufacturing:
• Serial flow cells
• Random flow cells
• Virtual cells

In a serial flow cell, all parts flow through the same sequence of machines and,
hence, a miniature production line is established. In random flow cells, different
parts have different routings within the cell, with the effect being somewhat
similar to a job shop. Machine utilization tends to be less in a random flow cell
than in a serial flow cell. The concept of a virtual cell was first proposed by the
National Bureau of Standards (NBS) [now the National Institute of Standards
and Technology (NIST)]. This concept uses a process layout of equipment just
like a job shop, rather than a cellular layout. Machines are treated logically as
a group even though they are physically separated. A virtual cell functions as a
cell based on the needs at the time. Individual workstations are allocated to a
virtual cell on a dedicated or time-sharing basis with other virtual cells. The
concept of virtual cells developed from the philosophy that changing production
requirements alter the part family makeup for a given production period. When
the requirements alter, the allocation of individual workstations will change.

The benefits of cellular manufacturing include the following:
• Better lead times provide fast response and more reliable delivery.
• Work in process and finished stock levels are reduced.
• Output is increased because of improved resource utilization.
• Less material handling is needed.
• Better space utilization is achieved.
• Better production planning and control is possible.
• Quality is improved, and scrap is reduced.
• Estimating, accounting, and work measurement are simplified.