Lean manufacturing aims to eliminate wastes and improve productivity, primarily by operating on a pull system known as just-in-time (JIT) production. The JIT method is opposite to push systems on the spectrum of supply chain management and can often be the barrier for a company going Lean.
In a push system, production is scheduled to meet the forecasted rate of demand. Also known as mass production, the push method has been around for centuries and while there are instances in which it might be beneficial, this kind of system can easily become a wasteful strategy. There are no limits on WIP and products are processed in large batches before moved down the production line or into storage. An inaccurate prediction can have a major impact on inventory levels or cycle times, and many organizations find themselves producing excessive inventory,
Pull systems on the other hand, are dependent on actual customer demand. The idea is that nothing is made, and no process is started without a submitted order from the customer. It’s virtually impossible for an organization to order materials and plan a strict pull system, which is where Heijunka comes in. Developed as part of the Toyota Production System, Heijunka translates to mean production leveling. By leveling either by volume or type, you can develop a system that not only works for your specific product and facility but sets your organization up for Lean success.
JIT and Kanban
Arguably the most important tool in operating this kind of production method is Kanban, a tool also developed by the Toyota Motor Corporation. Kanban uses visual cues, like cards or bins, to trigger an action further down the production line. Processes (like value-added activities) only occur when the bin or card is received, and operators ensure only quality products are moving to the next stage. Kanban can be tailored to fit the needs of an organization, some companies just starting out may go with a 1-card system while others may choose to use a more sophisticated electronic system with barcodes and scanners.
Other tools you may want to be familiar with in a Kanban system are:
- Kanban Boards: A simple visual representation of work in process. A basic board would usually be split into three different stages of “To Do,” “in Progress,” and “Completed.” People can quickly track orders as they move through the process and office departments can even utilize them for administrative purposes.
- Other visual cues: Bins and cards don’t need to be the only visual trigger! Think outside of the box and use something like color-coded floor markings to indicate when something may need to be produced or ordered.
A system using JIT manufacturing and following the principles of Lean with a pull system will find their system is much more flexible. If demand fluctuates or market conditions shift unexpectedly, you will have an easier time adapting production accordingly. It ensures production is only happening effectively eliminating overproduction and over-processing, which can hide defects and cause a whole bevy of other wastes.
Sources:
https://www.creativesafetysupply.com/articles/kaizen/
https://whatis.techtarget.com/definition/just-in-time-manufacturing-JIT-manufacturing
Additional Resources
- Kanban (With Examples)– creativesafetysupply.com
- Mass Production & Lean: What’s the difference?– blog.5stoday.com
- 5 Easy Rules For Kanban Success– blog.creativesafetysupply.com
- The History of Kanban– creativesafetypublishing.com
- Using Kaizen with Kanban– jakegoeslean.com
- Pull System – Kanban– lean-news.com
- Lean Manufacturing + Just-in-Time (JIT) Production– 5snews.com
- Basic Overview of Kanban– iecieeechallenge.org
- Using Kanban to Improve Manufacturing Flexibility– hiplogic.com