In manufacturing, changeovers have long been seen as a waste. Changeover represents the time and process of converting a line or machine from processing one product to another. Depending on the facility and industry, changeover times can range anywhere for a few minutes to as long as several weeks. Set-up and changeover time are two terms used interchangeably, although set-up is just one element of changeover. Changeover can be divided into the “3 Ups”:
- Clean-up: The time it takes to remove previous products, materials, and components from the production line.
- Set-up: The time elapsed while the equipment is set up for the next production process.
- Start-up: Any fine tuning that must be done after the equipment was re-started.
In traditional manufacturing processes like mass production, the number of changeovers would be reduced and not the time. This would lead to large lots and higher defects. On the other hand, Lean manufacturing facilities should be aiming for quick changeover with single-minute exchange of dies (SMED). The goal of SMED is to dramatically reduce or eliminate the time to change the production line from one method or unit to the to the other.
SMED operates in line with JIT manufacturing or one-piece flow, so facilities with mass or batch production will need to reevaluate their lot sizes. Some techniques to use when implementing SMED includes: converting internal set-up to external, standardizing functions, adopt parallel operations, and more. Following the SMED process though will increase machine work rates, eliminate set-up errors, while increasing safety from simpler set-ups.
There are many benefits to cutting down changeover time. Having quicker changeover times will reduce the defect rate of the production line, meaning fewer defective products will make it all the way through the manufacturing process. Additionally, quick changeover times will reduce costs associated with inventory, increase flexibility in production, and improve on-time delivery.