Lean Tools: Kanbans

If you need to change the way you schedule materials, including internal and external suppliers, Kanbans may be the best tool to use. Traditional management systems like MRP may not support your plan to adopt Just-In-Time practices, lot size reductions, or mixed-model production. Good preparation with standardized containers (for material movement) and physical tickets to signal needs and movement instructions will provide good support for the other tools and techniques you want to implement.

Basic Kanban principles translate to some of the following techniques and applications:

  • Empty containers accompanied by ticket that says “fill me”
  • Full containers staged with precise maximums clearly marked
  • Tickets displayed in the “make” area that cause precise quantities to be made
  • Tickets attached to full containers that cause product to be moved to defined destinations
  • Marked “floor parking spaces” or marked shelf space to limit overproduction
  • Maintaining a tight loop of ticket flow that minimizes opportunities for quality-related reworks
  • Housekeeping and safety practices that greatly assist Kanban scheduling
  • All of the people involved knowing what’s going with visual Kanban scheduling

Materials and production planners can use many of the same skills that they did in traditional environments. Instead of having to regularly feed elaborate planning systems or manually intervene in the production process, planning professionals use their skills to define, then redefine, the number of containers and tickets to be employed in particular processes. Same skills, but a much less tedious application.

In its simplest form, a planner’s job is to determine the level of daily quantities (per part) and the desired standard container content. The daily demand number is divided by the standard container content number to determine the number of uniquely marked tickets that should be issued in the process. In some settings, set-up quantities or lengthy transportation routes cause planners to “fudge” the arithmetic to issue a few extra tickets.

Here’s a specific example that applies Kanban:

In a factory with Visual Controls and proper JIT supplier agreements, plans are in place to make 600 assemblies every day during the peak season. According to the plans, 20 finished assemblies are to be nested in sturdy containers for movement to an adjacent department. Planners would therefore issue 30 make-and-move tickets which would facilitate steady production. The “piece-parts” in this assembly example would likewise be controlled with Kanban techniques. Tickets would be used just the same during the assembly process.

In this example, to be even more specific, you could use a “two-bin” Kanban approach, and that would also create an adequate visual signal. That is, parts from one bin would be consumed in production, at the production pace, and when empty, the second bin is pulled into place and the first empty bin is placed in a signal station (parking space) that says “fill me.” The “fill” (replenishment) cycle must, of course, be shorter than the consumption cycle of the full bin.

Kanbans can facilitate very steady production using simple visual controls—as long as its commonly understood by all production personnel. Together with other visual controls, they can have a huge, low-cost impact on production and efficiency.

 

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