Identifying Value Streams

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  While we all understand how powerful value stream mapping can be, selecting a value stream to begin with can sometimes be a daunting and task.  Along with exhausting brainstorming sessions, the effects of product flow can be quite deadly if the "spray and pray" approach is used.  Here is a three-step approach for selecting a value stream to map that will put you in a much better position to establish a flow down the line.  

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Family Comes First
  The first step in the selection of a value stream is to group your products into families.  A product family is a group of products that pass through similar processing steps and share common equipment prior to leaving your company (shipping to customer).  The grouping of product families can be done using a product routing matrix like the one shown below.  The left column shows your products/services and the top row lists all of the processes or pieces of equipment within your organization.

   We then would go through each box and place a number in the box to show us the 1'st step, 2'nd step etc.  X's can also be used too.  After the products/services have been matched up with the appropriate process steps or machine centers a simple sort will reveal the initial product families.  As you map your way through each value stream adjustments should be made.
Select your Family
  Now that our families are grouped we can select the family that will provide the biggest impact for your business needs.  This could be based on:

• Product volume in terms of money or units.
• Volume of product defects.
• Volume of WIP.
• Etc.

Once you have established your criterion the next step is to gather the production output data.  For example, if we were focusing on volume in terms of units and money we might collect our data for at least four months, if we did not have it already (chances are your ERP has it).  We then could use a pareto chart to show which of our families to focus on.  Of course, if you only have two families like the example above a bar graph will do the trick.  
Look at the Gemba
  Once you have figured out where the biggest impact for your mapping efforts is, it's time to take a look at the Gemba.  The gemba walk should be performed from a customer’s perspective, meaning you will observe the value stream from the customer and work your way upstream.  It's important that you view the value stream with the following considerations:

• How are customer orders processed (internal and external)?
• How does information flow through the value stream?
• What type of trigger is used if any?
• What types of waste do you observe?
• How does product move from location to location?

  In later posts on Listen to the Gemba we will look into some more important details that will help you to map the appropriate value stream and set our mapping efforts up to create an environment where products flow evenly down the stream.

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