An ‘A o Z’ of Lean Six Sigma
Welcome to your ‘F’ instalment of the A to Z of Lean Six Sigma. ‘F’ is another busy letter so two
pages and a top-up in the future.
EMSB Solutions @ http://www.emsb-solutions.co.uk/
F is for ‘Fun’
Yes improvement can be fun – even for engineers. Challenging and at times frustrating, but
the inclusive nature of an improvement project generates a real sense of contribution.
Business Improvement using plain English.
F is for ‘Flow’
We’ve already covered some aspects of flow in ‘B
is for Batch’. Creating flow is one of the goals of
any workplace. If we can create flow in the
manufacture of a product, or the delivery of a
service, we can minimise the inevitable
expensive pile-up of inventory, or the absence of
stock when needed (a so called stock-out). We
must try to balance the workload of individuals
to avoid their step in any process becoming
overloaded and becoming a bottleneck; or
having them wait for work to arrive.
One way of achieving flow is to have a multi-skilled workforce working together as a team.
With this approach, if one worker has a problem, other members of their team can step in
and support them; if they were left to struggle on their own, production would undoubtedly
be impacted and either inventory would build up at previous process steps, or the other
workers would stand idle until the problem was solved.
Flow can also be established using a ‘pull system’ which is driven by demand. The opposite is
a ‘push’ system where each person works flat out producing components or products
regardless of what is happening ahead of them. The demand system works well when
coupled with a ‘first in first out’ (FIFO, see below) approach to make sure that product
travels smoothly between two separate work cells or departments. This avoids inventory
building up and ensures nothing gets stuck in the system.
F is for ‘FIFO’
FIFO stands for ‘first in first out’ and is a simple way to ensure smooth ‘flow’ (see above) in
a process driven by demand. A ‘lane’ (physical or process defined) is devoted to products and
enough are manufactured to fill the lane. No more products are made until someone removes
some from the front of the lane – those ‘first’ in. The lane is replenished - at the back - by
additional products. It needs to be visually very clear when the lane needs refilling. This
approach keeps inventory down to a minimum and ensures that stock does not become
obsolete. It is a particularly good method for small high cost parts whose demand varies.
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Registered office: 78 Loughborough Road, Quorn, Loughborough, Leicestershire, LE12 8DX
An ‘A o Z’ of Lean Six Sigma
F is for ‘Five Whys’
Business Improvement using plain English.
A simple, question based tool for discovering the root cause of a problem. It was first
developed by Sakichi Toyoda (the founder of Toyota Industries) and is great for exploring
problems. It is as simple as asking the question “Why?” several times. By continuing this
questioning approach, we can avoid trying to fix only the symptoms of problems and address
the root cause directly. A simple method to record a ‘5-whys’ analysis is to build a tree of
answers, each branch of the tree ending with a possible root cause. Why only 5 whys? Taiichi
Ohno (father of the Toyota Production System) answered this “the basis of Toyota's scientific
approach . . . by repeating why five times, the nature of the problem as well as its solution
becomes clear” (link). It has its limitations and some of these can be avoided by stopping to
verify the answer after each ‘why’. You need a knowledgeable group to employ this technique
successfully.
F is for FMEA
Or to give its rather daunting full title Failure
Modes and Effect Analysis. It is quite an old
methods developed during the 1950’s but has
stood the test of time. It can be used in all types
of business and manufacturing situations and
provides a documented approach to managing
failures in processes. Essentially FMEA works
out what can go wrong, how bad will it be, how
easy is it to spot and how likely it is to occur;
From BBC News January 6th 2014
then it prioritises the failures allowing an
improvement team to focus on those with the highest score and therefore priority. It is a
useful way to ensure that changes to the way of working have been thoroughly thought
through. Compiling an FMEA can also reveal additional unseen issues. Using your process
map you break down the new way of working. For each step you need;
1.
2.
3.
4.
5.
The possible failure and the mode of failure, for example bearing, wear of bearing.
The outcome of the failure.
Severity of the failure scored 1-5, with 5 the ‘most severe’
Likelihood of the failure, again score 1-5 with 5 being ‘very likely’
Delectability of failure; score 1-5 with 5 be the ‘least easy to see’ given your current
detection methods.
6. Assign a Risk Priority Number (RPN) which is value of ‘3’ x ‘4’ x ‘5’ = 60
This has to be done by a team of knowledgeable individuals and may require an ‘expert’
guest. I have shown 1-5 here as this is more easily for a team to pick apart than say 1-10
degrees. How rigorous you are depends on the situation, but for general improvement work it
should be kept light in content. Obviously a more rigorous approach is necessary for an
aircraft engine component!
©EMSB Solutions. EMSB Solutions Ltd is a limited company registered in England and Wales. Registered number: 8668103.
Registered office: 78 Loughborough Road, Quorn, Loughborough, Leicestershire, LE12 8DX