One of the main drivers of non-lean behavior such as local optimization, batch work, and building up inventory is the desire to avoid time lost during changeovers between one job to another type of job. Sometimes this is reinforced by how we make financial measurements, seeking to earn hours or absorb cost (both of which ought to be in quotes) by utilizing the asset to the maximum. If we delve into the reasons why we would see more than one root cause for this behavior that builds up barriers between processes and people, lengthens cycle time to the customer, and drives overproduction: the mother of all wastes.
The changeover analysis sheet used in combination with a pencil, a stopwatch and two feet planted firmly within an Ohno circle is usually good to chop 50% to 80% of the time off of a changeover process that has not been kaizened in the past. Often repeated reductions of 50% are possible all of the way down to single digit changeovers, the aim of Single Minute Exchange of Dies (SMED). There is always a smaller unit of measure, after all.
When working on changeover reduction, the main thing you need to know is the difference between internal time and external time. Internal set up time or internal changeover time (same thing) is time spent on the changeover with the machine or process stopped. This work is “internal” to the down time. External set up or external changeover time is the changeover time for work done while the machine or process is still running. This work is “external” to the downtime. The goal of course is to minimize the downtime so the less internal time you have the better.
As in this example of changeover analysis, many unexamined changeovers are purely internal changeover work. The machine stops, and then the worker goes to look for the work order, the materials, the tools, the inspector to sign off on the first piece, etc. It’s a simple matter of categorization, planing and coordination to externalize much of set up work.
Using a video camera with a timer can give changeover analysis a powerful boost. In addition to being able to pause the video, observe the process repeatedly, and check the times against a running clock, you can spend less time worrying about writing down task times and more times observing the work and asking “why?” during the live changeover. If a video camera is not available, do this changeover kaizen as a team effort with 2 to 4 people, each assigned a specific task such as calling out times on the running clock, writing down comments and observations, or drawing the lines of movement on a spaghetti diagram – next week’s template.
Whether video taping, timing or asking questions about the changeover process, always practice respect for the people being watched, timed and taped. For most people it is really not comfortable to have a team silently scribbling away with stop watches, or worse, sighing and shaking their heads at all of the waste they see. Involve, educate and empower the team member and they will reward you with many great ideas on how to kaizen changeover time.