Lean Thoughts

Most of the tools in these roadmaps relate to the six sigma approach that seeks to use data to understand the way in which process inputs affect the process output. These tools, used in the context of the roadmap, help to guide our logic and analysis.

Train1

The six sigma approach is complemented by the use of "Lean" methods, which focus on the resources required to operate the process. Lean methods:

  • provide a set of tools for using at the workplace to improve organisation and efficiency
  • support a culture for communication, sharing, and solution of operational problems
  • are traditionally visual in nature: you can see the impact of their application
  • offer a framework for rapid, focused improvement interventions
  • direct our attention to the removal of wasteful activities from processes.

Lean Viewpoint

Traditionally, lean initiatives focus on getting work to flow smoothly, rapidly, and uninterruptedly through the process.

This is very different to traditional "productivity" initiatives that focus on maximising resource utilisation and minimising unit costs of production.

When looking to understand a process, the lean viewpoint follows the unit of work from initial order (or other trigger) through to fulfilment. This view is at 90 degrees to the view of watching each process step. The lean viewpoint is like looking out from the train at the stations passing by. The productivity viewpoint is like standing on a station watching the trains go by.

Definitions of Value

VAtree

Lean analysis asks a few simple questions of each step in the process, based on our knowledge of the process and of our customers' requirements.

  1. Does this step add value for our primary customers?
  2. Is this step required for management or regulatory requirements?
  3. Is this step required for preventive or corrective action?

If the answer to #1 is yes, we say the step is Value Add (VA).

If the answer to either #2 or #3 is yes, we say the step is Business Value Add (BVA). The customer doesn't need it, but we need to do it. 

However, the strategy for dealing with #2 involves negotiation with the relevant stakeholders, whilst the strategy for #3 involves improving the process to obviate the need for the preventive / corrective step.

If the answers to all three questions is no, we say the step is Non Value Add (NVA) and it becomes a candidate for elimination.

The flowchart at right shows a slightly more detailed view of the decision tree.

Value Stream Map

The Value Stream Map (VSM) is a rich style of documenting processes, typically processes involving the handling of physical materials through a chain of dependent processing steps. It is ideally suited to repetitive "production line" processes. It offers a single view that can show the performance of each step in the process, build ups of inventory, and issues regarding co-ordination. 

The VSM is less well suited to documenting processes with complex logic and interdependencies, for which other types of process map may be more suitable.

Identifying Waste

According to one popular acronym, there are eight types of waste, namely:

  • Defects
  • Overproduction
  • Waiting
  • Non-use of staff brainpower
  • Transport
  • Inventory
  • Motion
  • Extra processing

Non-use of brainpower is an overarching waste: we need to engage the people who know the most about the process in our efforts to continually improve the process. That's easy to say, but in many organizations there may be significant cultural and social issues to work through to get widespread involvement.

Defects are whatever the customer (or next process) rejects. We have wasted the resources used to create them, and we have to do the work all over again. The cost of poor quality was, and remains, a prime driver of overall business performance.

Extra processing means doing things that don't add value to the customer such as excess packaging (which may however be required by some intermediate process so perhaps not so easy to fix ...)

Transport is usually related to moving the work around more than necessary; motion is usually related to moving the worker more than necessary to get the job done (including, for example, having to click on several web links or open several documents to cut and paste to create or develop a document). 

Over-production means doing things before the customer (or next process step) is ready for them. It inevitably leads to the accumulation of inventory, which causes waiting, and if the customer changes his mind in the meantime then all of the accumulated work is in effect wasted. So why do we over-produce? Often, because we are worried that if we run the process "just in time" then something will go wrong and we will be late. In other words, we over-produce to compensate for variation in our process, and the result is that we make things worse.

Levelling and Flow

The idealised lean process consists of a sequence of steps each having the same processing time such that work flows through the process at a constant rate. If one of the process steps is slower than the others, it will act as a bottleneck, identifiable by a build up of inventory (work in progress) that is waiting to be processed. 

For work which flows at constant rate, we can synchronize our processes by setting a pace (known as the Takt time) that is fast enough to meet customer requirements whilst allowing enough time for each process step to complete. Work moves in lockstep through the process at the rate of the Takt - each process step is started at the same time.

If work arrives at a variable rate, we need to adjust our resources to compensate. Unless we have adequate forewarning, we have to balance the risk of not having enough capacity with the cost of carrying too much capacity. A useful tool to get insights into the variability of volumes is to apply a control chart to the difference between the forecast and actual volumes, thereby developing an estimate of the accuracy of the forecasting process.

Toyota Production System

Toyota remains the exemplar of lean thinking. This exhibit on their website shows numerous examples of lean innovation over a period of more than 60 years. (60 years of continuous improvement!)