Just in Time (JIT) is a key aspect of Lean Manufacturing. It is concerned with the elimination of wasteful activities and in particular waste due to delay. The JIT approach looks at every stage of the production process from raw material supplies, to delivery to the final customer. The phrase 'final customer' is used to emphasise that JIT also considers intermediate and internal customers at each process stage.
JIT encourages the use of demand pull 1 systems across production operations, in place of the traditional forecast and provide or 'push' approach. In order for pull systems to work effectively, the manufacturing process must be balanced, and small batches processed in a continuous flow of work.
The desired flow of work is achieved by working hard on balancing the production line capacity. A team approach is used, adopting a flexible use of labour and equipment, and by running the line at a pre-determined cycle or TAKT 2 time. Particular emphasis is placed on rapid changeover between product types. The goal of a Single Minute Exchange of Dies (SMED) is often used to describe this principle.
The goals of JIT:
- Zero faults
- Zero time to change or adjust tools or equipment
- Zero inventory
- Zero materials handling
- Zero stoppages
- Zero production flow time (batch transfer)
- Manufacture batch size = 1
Many businesses may feel they are far from realising these goals, however techniques and assistance exist to enable the gap between current performance and the ideal to be reduced rapidly and then to be continuously improved. The list of goals is used to direct improvement activities and is not a rigid target against which to judge success or failure.
TWI helps its Members with JIT manufacture as part of a lean audit and action plan, or as a specific targeted activity.
TWI works with Member companies to review current workflow and changeover characteristics within their processes and make recommendations for improvement. TWI also manages JIT projects as required, in conjunction with relevant individuals from the Members' organisation.
For more information, please contact us.
Bicheno, J., Cause and Effect JIT: The Essentials of Lean Manufacturing, 2nd Edition, PICSIE Books, Buckingham, England, 1994 (ISBN 0 9513829 5 0)
Womack, J.P. and Jones, D.T, Lean Thinking, Simon & Schuster, New York, USA, 1996 (ISBN 0-684-81035-2)
1 Demand pull means that products are only processed through the factory in response to a customer order, so that no Work in Progress (WIP) is generated at the various production steps. Traditional push systems allow production to continue in the absence of a customer demand, hence WIP builds up around the factory.
2 TAKT time refers to the pace of production balanced to the rate of sales.