In manufacturing, changeover is the process of converting a line or machine from running one product to another. Changeover times can last from a few minutes to as much as several weeks in the case of automobile manufacturers retooling for new models.

SMED, or Single Minute Exchange of Dies, is the technique of reducing the amount of time to change a process from running one specific type of product to another.  The purpose for reducing changeover time is not for increasing production capacity, but to allow for more frequent changeovers in order to increase production flexibility.  Quicker changeovers allow for smaller batch sizes.

The benefits of quick changeover include:

     • Reduce defect rates – Quick Changeover reduces
       adjustmentsas part of setup and promotes quality on the
       first piece.
     • Reduce inventory costs – Elimination of, or reduction in
       numbers of batches, and their sizes, allows for recovery of
       operating cash and manufacturing space.
     • Increase production flexibility – Increase output and
       improve timeliness of response to customer orders.
     • Improve on-time delivery – Quick Changeover supports 
       the ability to meet customer demands.

The terms set-up and changeover are sometimes used interchangeably however this usage is incorrect.  Set-up is only one component of changeover.  Changeover can be divided into the 3 Ups:

     Clean-up – the removal of previous product, materials and
                       components from the line.
     Set-up    –  the process of actually converting the equipment.
     Start-up  –  the time spent fine tuning the equipment after it
                       has been restarted.

The keys to quick changeover are found in changing your thinking about changeover as in the following:

      1. Rethink the idea that machines can be idle, but workers
          cannot be idle.
      2. The ideal setup change is no setup at all or within
          seconds.
      3. Ensure that all tools are always ready and in perfect
          condition.
      4. Blow a whistle and have a team of workers respond to
          each changeover.
      5. Establish goals to reduce changeover times, record all
          changeover times and display them near the machine.
      6. Distinguish between internal and external setup activities
          and try to convert internal to external setup.

To start identify and separate the changeover process into key operations – External Setup involves operations that can be done while the machine is running and before the changeover process begins, Internal Setup are those that must take place when the equipment is stopped.  Aside from that, there may also be non-essential operations. Use the following steps to attack the quick changeover:

Eliminate non-essential operations – Adjust only one side of guard rails instead of both, replace only necessary parts and make all others as universal as possible.

Perform External Set-up – Gather parts and tools, pre-heat dies, have the correct new product material at the line… there’s nothing worse than completing a changeover only to find that a key product component is missing.

Simplify Internal Set-up – Use pins, cams, and jigs to reduce adjustments, replace nuts and bolts with hand knobs, levers and toggle clamps… remember that no matter how long the screw or bolt only the last turn tightens it.

Measure, measure, measure – The only way to know if changeover time and startup waste is reduced is to measure it!

Ron Pereira from the Gemba Academy authored a video on Quick Changeover.  A great summary of quick changeover is shown below: