by Mark Stover

How long would it take you to change all four tires on your car, fill the tank with fuel, and make minor body repairs? All afternoon? A couple of days?

NASCAR pit crews do all that and more in only 12 to 14 seconds on race days. How do they do it? Teamwork, of course – but also through an intense study of what it takes to perform all the tasks necessary to keep a car race-ready. 

Time is money at NASCAR. It is in business, too. How long does it take to change over your key production equipment from one part to another?

A defined difference

Changeover is the process of preparing machinery or equipment to shift from the production of one particular product to the production of another. Changeover time is the time between when the last good piece is produced by the previous run to when the first good piece is produced by the subsequent run.

Quick changeover is sometimes referred to as setup reduction. However, this term actually describes something more limited – the time required for equipment setup – and does not include the crucial capability of the new setup to actually produce good parts.

Another term that’s sometimes used is SMED, which stands for “Single Minute Exchange of Dies.” Toyota began using the term when Shigeo Shingo first experimented with reducing the time it takes to change over equipment. SMED does not mean changing a die (as in a stamping press) in 60 seconds, but rather in under 10 minutes (a single-digit number of minutes). 

While SMED was originally intended to work on stamping press die changes, the basic process improvement approach Shingo created has been extended to all types of changeovers.  Any machine on the shop floor with dies, spindles, or other tooling requiring a change to make new parts can be a focus of the approach Shingo innovated.  Quick changeover techniques can also be applied to office and information flow activities.

Take a strategic view

Manufacturers that pursue a quick changeover improvement initiative generally do so with strategic intent. That’s because quick changeover is a lean tool that requires integration with other lean tools.  Reducing changeover time will not produce a measurable impact if it’s not part of a larger lean effort.

Typically, a manufacturer will decide to initiate a quick changeover project when it faces the need for smaller batch sizes. It first realizes that lead times are too long due to scheduling that only produces needed parts periodically. To produce a wider variety of parts more often, the company must switch to shorter runs with smaller batch sizes. In other words, it must produce four to five types of products from a machine per day rather than just one or two.

Smaller batch sizes require more changeovers. Therefore, productivity losses will quickly add up unless the company reduces the amount of time it takes to change over its machines.

Five steps to quick changeover

To initiate a successful quick changeover project, a manufacturer can follow this simple five-step process pioneered by Shingo.

1. Establish the baseline. Use a video camera to capture what really happens during a changeover. The video lens is utterly objective, and the recording often proves to be very revealing. It’s also useful for analyzing the internal and external activities of an actual setup.
   
   
2. Separate internal from external. Internal setup activities are those actions that can be safely performed only when the machine is not running. External setup activities are those actions that are performed while the machine is running in preparation for the next changeover. Often, there are a number of external activities that are actually performed when the machine is down that could be performed before the end of the last run.
   
   
3. Convert internal to external. Reduce the amount of work that must be performed when the machine is idle. This will have a significant impact on the overall time of the changeover.  It will also keep the machine producing parts for a larger portion of the available time.
   
   
4. Streamline all changeover efforts. Once internal and external activities are separated, determine which internal actions can either be eliminated entirely or made easier.  An example would be using guide pins to seat a new die and clamps to hold it in place. This is much faster than having to measure each dimension of the die and then bolt it into place.
   
   
5. Standardize the gains. Once a new procedure for conducting a changeover is established, ensure that everyone becomes familiar with it. Give workers experience in using the new procedure (training), and have someone audit the process periodically to ensure that standards are maintained.

Mark Stover is a senior consultant in Wipfli’s manufacturing and distribution practice. Mark’s areas of expertise include business process improvement, lean manufacturing practices (focusing on standardized work and 5S), lean performance measurement, value stream mapping, manufacturing process auditing, policy management, training and facilitation, team development, and sales process improvement. He can be reached in Wipfli’s Madison office at (608) 661-2639 or mstover@wipfli.com.