Changeover Time is an important factor in determining the amount of Lead Time required to deliver to your customers. The capability of any organization is demonstrated by how flexible it can change from one product or service to the next to align with customer demand. The more your customer demand fluctuates, the more flexibility is needed to allow you to deliver products or services on time, every time.

There is a direct correlation between Changeover and Lead Time:

• Long Changeovers increase Lead Time.

• Short Changeovers reduce Lead Time.

I always find it interesting to ask a simple question during a first visit to a company. "How long does it take to changeover this machine to run the next good part?"

One answer I received was, "Well, it takes about an hour." When the changeover was recorded using a video camera it actually took 2 hours 35 minutes to produce a good part. It demonstrated a lack of understand by the management team about how to define a changeover. Once we understand that machine downtime (including changeovers) is an important factor directly impacting process lead time, one would think every company would track it effectively. Unfortunately, this is not the case.

To fully understand Changeover Time, we must clearly define it. The definition of Changeover Time is:

The time between the last good part off the current run and the first good part off the next run.

Typical most companies will only include the time taken to replace the tooling/equipment in its changeover time. However this does not allow for all the other activities which must be completed to produce a good part. There are four specific processes required to complete any changeover. Each process takes a specific amount of time, lets take a look at a typical breakdown of changeover activities. The following diagram shows these four processes based on the percentage of time to complete:

The length of Changeover Time for any machine or process will determine if you can "Manufacture on Demand" or forced to use "Batch Manufacturing."

The ability to "Manufacture on demand" requires a very short changeover time to achieve total flexibility throughout the manufacturing process in order to supply customers on demand.

Batch Manufacturing is usually a result of long changeover times which increases the overall lead time required to get a finished product into the hands of the customer.

Lean Manufacturing creates an environment where you only produce what's required to meet the demand of the customer. Long machine Changeover Times will not allow you to do this. To successfully compete in today's global market, one of the key steps in your lean implementation is to dramatically eliminate or reduce changeover times .

It's not unusual to reduce Changeover Time from hours to minutes by following a simple process called "SMED" which is the acronym for "Single Minute Exchange of Dies." This process was developed by Shigeo Shingo during the 1950's.

It requires an analysis of the changeover procedure to identify specific activities and group them into "Internal" and "External" elements

• External elements of work can be completed while the machine is still running e.g. get the next tool, get all your clamps, get lifting equipment in place, put equipment away, etc.

• Internal elements of work can only be done while the machine has stopped e.g. change the tool, adjust the machine depth, sharpen a tool, change toner in a printer, etc..

As you can see from the diagram once you can define the "Internal" or "External" elements, you can separate them. Now you can create a procedure to complete all "External" elements for the next changeover while the machine is still running the current parts (Part A). When the current run is finished, everything required for the changeover to the next part (Part B) is available and ready which will reduce Machine Downtime and speed up Process Lead Time.

Quick Changeover Case Study

Roplast Industries Inc. went through their lean implementation program. Included in their program was a series of Quick Changeover events in a conversion area of their facility. There are several machines which took on average 120 minutes to changeover to production readiness for the next part. Because of these long changeover times Roplast would run a product for as long as possible (typically 3-4 days). Roplast management preferred to build up inventory rather than break the machine down and changeover to the next job.

Over a period of 12 months and after a series of kaizen events which focused on Quick Changeover, the time was reduced to an average of 23 minutes. Roplast set a goal to reduce their average changeover time to 15 minutes.

When we first approached the operators during a changeover training session and suggested that they could reduce their changeover times by at least 50%, many of them thought we were crazy. After the first kaizen event the changeover times were reduced to 38 minutes, that's a saving of 68%.