Let’s face it, machine changeover time is a non-value-added activity that can really impact your uptime and your ability to respond to customer demand. Reducing changeover time is usually one of the first projects a company undertakes when they start a lean journey. The changeover process must go smoothly and efficiently. A good analogy is to think of a Nascar driver making a pit stop. The crew rushes out, each person has their assigned job, they do it extremely well and the car is gone in a matter of seconds.
To effectively reduce your changeover time, you need to separate internal changeover time from external changeover time. External changeover time includes all the things you can do while the machine is running the current part number before the machine goes down and you start the changeover to the next part number. These activities should include the following:
- Make ready the new tooling, i.e., dies, fixtures, etc. prior to shutting the machine down. Make sure the tooling is de-bugged and ready to go. When the machine is down is not the time to look for tooling that needs repaired, punches need replaced, etc. Think about the pit crew. When the car comes in, they’re not checking the air in the replacement tires and filling the gas can!
- Stage the tooling, dies, etc. at the machine. Once the machine is down, the tooling should be ready to install quickly. It is not the time to start looking for the new tooling, fixtures, hammers, wrenches, die carts, etc.
- Eliminate all the unnecessary walking and motion. Keep everything necessary for the change as close as possible. A good idea is to do a spaghetti diagram of the changeover process before making any improvements to get an idea of all the unnecessary walking and motion.
- Another good idea is to video tape the changeover process to observe the methods used. Can the method be improved. Can clamps, bolts, screws, etc. be revised to make them quick change and more efficient.
- Organize and manage the changeover process. Establish assigned jobs. Don’t let the process have a life of it’s own and not be controlled.
- Monitor your progress. Install white boards at each machine. State the goal, the current changeover time, and the team’s best changeover time. Improvement is an iterative process and you can’t expect everything to be accomplished in a day or a week. It may take several months to reach the goal, but huge improvement can result in a matter of a few weeks.
Internal changeover time is the time the machine is actually down. It is the time during which no “good parts” are being produced and everything to physically change from one part number to another is accomplished. That is why it is extremely important to get everything ready and staged prior to shutting the machine down.
The goal is to make the changeover in less than 10 minutes. This is what’s called “SMED,” or Single Minute Exchange of Die. When I tell clients this I usually get some pushback and they tell me that it’s impossible. But within a couple of weeks when they’ve reduced their changeover times from 90 minutes or more to less than 20 minutes, they start to become believers.
Changeover, like any activity, must be coordinated and practiced to work smoothly and efficiently. It must be continuously improved till the goal of less than 10 minutes is achieved.