Six Sigma DMAIC – Analyze Stage


Value Streams and Their Analysis – The term value stream is used in Six Sigma as a descriptor of the necessary factors that contribute to the value of a product or service from the viewpoint of the customer.  It is directly lifted from the Lean methodology and shows the overlap of the two methodologies very clearly.

When you have a process map, you can look at each part of the process and identify each stage as having one of three roles:

  • Something that creates value for the customer
  • Something that creates no value to the customer but is a necessary requirement or dependency within the overall process
  • Something that adds no value to the customer and is not needed by any part of the process

Those items that fall within area 3 are waste and can be eliminated.  When thinking about identifying these elements, it is worth considering if the customer would pay for them or if they modify the product in some way.   Is the output at this point different to the input to such an extent that it is necessary in the overall output? A slightly wordy expression granted, but it gives the general thought process required.

One consideration through a value stream is the complexity of activity during the cycle time.  This may be related to the previous unit, where we identified one of the metrics of scheduling that can be elongated cycle times.  Simplifying the process can be one of the easiest ways of reducing the cycle time. So, if the opportunity to remove specialized elements or time-consuming activities within a process is possible this should be identified and removal should take place.

Reducing, restricting, or even removing non value-added items can provide a clear and easy approach to reducing overall cycle times.  Some companies have found that an examination of many processes can identify up to 50% of non value-added activity that has crept into the historical process methodology.

Unnecessary movement of materials or people can be a big non-value component in a process.  Sometimes, the physical environment can be examined to alleviate this by reducing journey times and thus, cycle times.  Some of the outcomes from this examination can be reductions in the supplier to customer journey – both internally and externally.

Sometimes materials, outputs, or even people are viewed in batches rather than a flexible commodity to meet needs.  Batches can be very inefficient and cause products and outputs to be kept warehoused for long periods between uses.   Removing batches can remove this wasted time.

Unfortunately, some products are designed to be produced in batches with the most cost efficient or timely machinery producing volumes at one time.  For example, a bread oven may be designed to bake 24 loaves at a time; it would be ineffective to just bake one at a time or only 6 to meet a particular customer order, as the cost of running the oven is the same no matter how large the volume of loaves.   This cost will be a constant that has to be assessed in balance with storage cost. This is where the multiple metrics taken in the previous stage of DMAIC can prove their worth.

One value stream examination always worth looking at is the start up or “setting up period” for any activity.  This can be particularly relevant to clerical offices and other non-manufacturing processes. We define “Setup” in terms of preparation, replacement, location, and adjustment.

Preparation refers to gathering materials required to begin, whether that may be logging into the computer or collecting today’s forms for examination.   Each stage of a process has a preparation. For example, a project may involve reducing preparation through cellular teams so transport of product between required personnel takes place almost instantly, and local storage of materials in a ready-to-go state can be achieved.

Replacement refers to the additions or removal of items used within a process. Loading paper in a copy machine or filling the paint sprayer are good examples of this. Reductions in occasions when this is necessary by filling the paint sprayer to the full mark each time and only refilling an empty can help reduce wasted time and efforts in these areas.

Also making sure that all copiers load the same way can help breed familiarity within the workplace and stop hold time while familiarization with a different machine takes place.   While these are obvious, small examples, think about how they can be applied within your workplace.