101 Kaizen Templates: Changeover Analysis

There are many common non-lean behaviors such as local optimization, batch work, and building up inventory. Creating WIP lengthens cycle time, worsens quality, builds up barriers between processes and people contributes to late deliveries and overproduction. So why do we do it? It’s often the result of the desire to avoid time lost to changeovers between one job and another type of job.

Fewer Changeovers are Better?

Sometimes large batches production is reinforced by how we make financial measurements. Accounting norms call inventory an asset, seek to earn hours or absorb cost by utilizing the asset to the maximum. The costs of moving, storing, retrieving and obsolete inventory

Changeover activity costs money but doesn’t produce valuable product. It’s lost capacity. The logic goes, the fewer changeovers, the less lost time. When changeovers are infrequent, we need to run bigger batches of that product, since it may be a while until the next time we’ll run it.

The Need for Speed and Frequent Changeovers

Whatever our reasons may be, when changeovers are not frequent, we come to accept this lost time as cost of doing business. But Lean thinking takes the view that smaller batches, ideally one at a time, is the way to delivery lowest cost, best quality, on-time. This requires frequent changeovers from A to B and back to A, based on just-in-time customer needs. But the more we do changeovers, the more time we lose. This is a conundrum, unless we can reduce changeover times.

Changeover Analysis Sheet

Often all you need is the changeover analysis sheet a pencil, a stopwatch and two feet planted firmly on the shop floor to reduce changeover time by half. It’s not unusually to see reductions of 80% or more after several rounds of improvement. By making repeated reductions of about 50% we can achieve single-digit changeovers. This is the aim of the Single Minute Exchange of Dies (SMED) concept. After achieving single minutes, we aim for continuous improvement down to seconds.

Internal Time vs. External Time

When working on changeover reduction, the main thing to know is the difference between internal time and external time. Internal set up time or internal changeover time 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.

At first, many 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 the changeover work.

Documenting Video Analysis of Changeovers

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.

Respect for People and Quick Changeover

Whether video taping, timing or asking questions about the changeover process, always practice respect for the people. It can feel awkward to be watched, timed and taped. It’s unsettling to have a team silently scribbling away with stop watches, or worse, chuckling and shaking their heads at all of the waste they see. When doing changeover time reduction activity, communicate, be upfront, involve, educate and empower the people to give suggestions. They will reward you with many great ideas.

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