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May 12, 2010

Single Minute Exchange of Die - SMED

Changeover Time is the amount of time it takes to change over equipment/programs/ files/people from the end of the previous step to the beginning of the current step. Changeover time includes set up, warm up, trial run, adjustment, first item/work inspection, etc.

Examples include: Creating a new file for a new customer; Reviewing an existing file before seeing a client; Changing computer programs; and Searching your desk for the correct form.
External setup involves tasks that can be performed to prepare for changeover while the machine is still running.Internal setup involves tasks that can only be performed while the machine is turned off. Lean philosophy recommends that internal setup be facilitated by the use of tools and equipment that make the changeover processes fast and smooth.

Briefly, this methodology includes:

MEASURE the current changeover times and record them in order to monitor improvement.

SEPARATE EXTERNAL AND INTERNAL ACTIVITIES “External” activities are simply the jobs/work that can be carried out while the step or process is continuing (e.g. getting ready for the next customer while the service packet for the last customer is copying, etc.). “Internal” activities are those jobs which cannot be carried out while the step/process is going on (e.g. interviewing the customer while completing a service request packet on the prior customer). By identifying and separating internal and external activities, the intention is to do as much as possible while the step/process is continuing.

CONVERT INTERNAL TO EXTERNAL ACTIVITIES The next step is to try and convert some of the internal tasks into external tasks.

REDUCE THE TIME TO CARRY OUT INTERNAL TASKS Of the remaining internal tasks that cannot be converted to external tasks, efforts should be made to reduce the time taken to carry out them out -- to eliminate, modify, or streamline the changeover tasks. This can include re-design of the forms, protocols, and requirements. Consider tackling no- or low-cost reductions first, but keep in mind that you must not lose your focus on implementing the other reductions.

Techniques to reduce changeover time
You can use several techniques to reduce changeover time:
1- staged tooling and fixtures – this involves preparing parts or tools in advance so that while one part or tool is in the machine, the second can be set up in the fixture.
2- operations conducted in parallel – this technique involves having more than one operator perform a changeover so that the operators can perform their tasks simultaneously.
3- standardization – this involves having one set of tools that can be used to perform changeovers on all the machines, rather than a different set of tools for each machine.
4- quick attachments – this involves using parts and tools that have quick attachments to make changeovers more efficient.
5- assisted tool movement – this involves using simple tools to move machinery, rather than moving heavy equipment with forklifts or cranes.