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Set-up Reduction

Changeover or set-up time is an important indicator of lead time. The capability of any organization is demonstrated by how flexible it is to change between products or services to meet customer demand. When demand fluctuates more flexibility is required to deliver the product or services on time, every time.

There is a direct correlation between changeover and lead time:

  • Longer changeovers increase lead time.

  • Shorter 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." One would think that because machine downtime (including changeovers) is an factor which influences lead time that all companies would track it effectively. 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.

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 changeover the tooling in its set-up 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 the 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 taken to complete:

 

1 Preparation. 30%
2 Removing and mounting.  5% 
3 Measurements, calibration and settings. 15%
4 Trail runs and adjustments. 50%

 

The length of set-up time for any machine or process will determine if you can "manufacture to demand" or have to use "batch manufacturing."

The ability to "manufacture to demand" requires a very short set-up time to achieve total flexibility throughout the manufacturing process in order to supply customers on demand.

Batch manufacturing is usually a result of long set-up times which increases the overall lead time required to get a finished product into the hands of the external customer.

Lean manufacturing creates an environment where you only make what is required to meet the demand of the customer. Long machine set-up times will not allow you to do this, so as part of the lean implementation you will need to reduce set-up time, preferably to 10 minutes or less.

It is not unusual to experience a reduction of set-up time from hours to minutes by following a simple process called "SMED" which is short for "Single Minute Exchange of Dies." This process was developed in Japan by Shigeo Shingo during the 1950's.

It required an analysis of the set-up procedure to determine which activities are internal and external.

  • 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 is stopped e.g. change the tool, adjust the machine depth, sharpen a tool (which requires the machine to be stopped), etc..

 

As you can see from the diagram once you can define an internal or external element, you can separate them. This will allow you to complete all external elements for the next set-up while the machine is still running the current parts. When the current run is finished, everything required for changeover to the next part is available and ready.

Set-up Reduction Case Study

TEiM coached Roplast Industries Inc. through their lean implementation. Part of this process was set-up reduction in a conversion area of their facility. There are several machines which took on average 120 minutes to changeover to get a good part and the machine was ready for production. Because of these long set-up times Roplast would run a product for a long as possible (typically 3-4 days). Roplast management preferred to build up inventory rather than break the machine down and set-up the next job.

Over a period of 12 months and after a series of kaizen events which focused on set-up reduction, the changeover times are now down to an average of 23 minutes. Roplast has set a goal to get the average changeover time down to 15 minutes.

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

The people at Roplast went through a major paradigm shift which allowed them to take a chance at the possibilities. In doing this they have achieved great success.

 

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Why should I worry about changeover times?
Well its really your choice at the end of the day.

However there is one simple fact that no one can avoid.

If you have long changeover times, you run the machine for long periods of time to justify the downtime for changeover.

This causes large inventories of parts and longer lead times.

 

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