The Revolution of Just-In-Time (JIT) and Lean Manufacturing

1
The Revolution of Just-In-Time (JIT) andLean
Manufacturing
2
The essence of the JIT revolution and Lean
Manufacturing

• Try to reduce the system operational
  inefficiencies and the resulting waste by
  identifying the sources of these inefficiencies
  and working proactively to eliminate them as much
  as possible.
• In the emerging philosophy, inventories should be
  carefully controlled and they should not function
  as the mechanism for accommodating the system
  inefficiencies gt Just-In-Time (JIT)
• The aforementioned effort should be an ongoing
  process towards continuous improvement rather
  than one-time/shot effort.

3
Targeting the sources of inefficiency

• input
• unreliable quality of raw material
• unreliable delivery times
• operation
• unreliable processes in terms of
• required processing times
• process outcome
• complex interacting process flows
• long set-up times
• unreliable (irresponsive and irresponsible)
  personnel
• output
• Highly variable production requirements in terms
  of
• production volume, and
• production scope

4
JIT enabling factors and practices

• Emphasis on quality at both the process and the
  supply side by promoting
• Statistical Process Control (SPC) theory and
  practice
• Quality certification programs
• Deployment of stable automated processes and
  foolproof practices (like checklists and machines
  gauges) to guarantee the desired performance
• Employee empowerment and knowledge management
  (quality circles)
• Tightening of the supply chain by promoting
• Long-lasting and trustful relationships between
  the different parties in the supply chain
• Timely and reliable information flow across these
  parties that takes advantage of modern IT
  technologies, like
• Electronic Data Interchange (EDI), and e-commerce
  practices
• Real-time communications and global positioning
  systems
• Promotion of vendor owned and managed inventory
  practices that
• Establish economies of scale and protection to
  variability through pooling
• Enhance the demand visibility across the entire
  supply chain.

5
JIT enabling factors and practices (cont.)

• Simplification of the process flows by promoting
  cellular manufacturing practices
• Dedication of separate production cells to
  product families with similar processing
  requirements
• U-shaped layouts for facilitating employee
  sharing
• Employee cross-training for more flexible and
  higher utilization
• Set-up time reduction through
• The adoption of cellular manufacturing
• Externalization of set-up times
• Employment of flexible processes and pertinent
  auxiliary equipment like pertinent fixtures
• Part standardization
• Focus on repetitive manufacturing and promote the
  establishment of stable production rates through
• Smoothing of the aggregate production
  requirements by appropriate quota setting
• Pertinent sequencing of the final assembly to
  support a desired product mix
• Use of buffer capacity (planned overtime) to
  protect against slippages from the target
  production rates
• Component standardization

6
Institutionalizing the JIT practice through the
KANBAN-based Production Authorization Mechanism

• Remarks
• The KANBANS at each station cap the WIP at that
  station and they offer a natural
• mechanism for reacting to various disruptions
  taking place in the system operation.
• In particular, production at each station is
  pulled as a result of the downstream
• activity rather than pushed by an
  MPS-generated schedule.
• The KANBANS at each station should be set at a
  level that enables production
• at the target rate
• A safe approach to set the KANBAN level at each
  station is by setting it initially to
• the historical WIP level, and subsequently
  decrease it incrementally while
• observing its impact on the production rate
• Frequent KANBAN changes are ineffective, since
  the production rate of the line is
• rather insensitive to these changes, and they
  should be avoided

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From KANBAN to CONWIP

• Why?
• It maintains the WIP cap but at the same time it
  offers more operational flexibility than
• KANBAN.
• The unrestricted flow of WIP within the line
  enables better utilization of the (shifting)
• bottleneck, and therefore, higher throughput.
• Less stress for the line operators since it
  enables them to work at the natural pace of the
  line.
• It enables more flexible scheduling of the line,
  since in the CONWIP operational context,
• WIP is interpreted more generally as some
  aggregate amount of workload loaded into
• the line (even measured in time-units, rather
  than number of parts) new parts are pulled from
• an available work backlog according to a
  pertinent set of dispatching rules.
• Easier to analyze and parameterize through the
  theory of closed-queueing networks.
• Remark While the above features of CONWIP
  mitigate the rigidity of the KANBAN-based
• shop-floor control, its pull nature still
  implies that it requires stable target production
  rates
• in order to function well, and therefore, it is
  appropriate for repetitive manufacturing
  contexts.