How To Achieve One-Piece Production In Machining Operations

Posted by on Sep 26, 2021 in Flow and Pull Systems, Lean, One-Piece Flow | 0 comments


Last week, I discussed how Henry Ford developed one-piece-flow in his assembly operation and why he could not implement one-piece production in his machining operations. But all was not lost due to Taichi Ohno’s persistence, and one-piece production became a reality in machining operations.

This week I’ll focus on the rules and conditions necessary to implement one-piece production in machining.

Toyota identified five rules and conditions necessary for one-piece production:

  1. Base cycle time on market requirements. This approach starts by coordinating the timing of production with customer needs. In other words, base the number of items to be produced on the number required by customers.
  2. Base equipment capacity utilization on cycle time. Establishing one-piece production is difficult when using large equipment, which engineers have designed for flexible manufacturing systems. Such equipment and machines are intended for batch production and cannot coordinate with one-piece production cycle times.
  3. Center production on assembly processes. When turning away from planning-centered production, we must also shun the traditional emphasis on processing (such as machining) parts. The latest market information is passed exclusively to the assembly department in one-piece production systems, which receives a weekly production plan based on that information. Upstream processes do not receive this information. In other words, the factory follows the pull production principle.
  4. The factory layout must be conducive to one-piece production. The design will include using many U-shaped cells in a verticle structure and several machines operated by one operator. This layout should consider the following elements:
    • Make the factory layout conducive to the overall production flow.
    • The factory must include clear pathways.
    • The production line should clearly distinguish between material input and product output.
    • The production line should consist mainly of single-operator U-shaped cells.
    • Include thorough inspection in the layout.
    • Minimize in-process inventory.  
  5. Goods must be conducive to one-piece production. Very small workpieces are not conducive to one-piece output because of the waste involved in the setup, positioning, and removal. If piece handling is automated and the cycle time is short, one-piece production is still possible. It is also impossible to have one-piece production if changeover times are long.

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