martes, 12 de enero de 2021

Main concepts of six sigma.

Looking at the lingo .

You can see from Figure 1-1 that Lean thinking involves a certain amount of jargon – some of it Japanese. This section defines the various terms to help  you get Lean thinking as soon as possible:
✓ Heijunka provides the foundation. It encompasses the idea of smoothing processing and production by considering levelling, sequencing and standardising:
• Levelling involves smoothing the volume of production in order to reduce variation, that is, the ups and downs and peaks and troughs that can make planning difficult. Amongst other things, levelling seeks to prevent ‘end-of-period’ peaks, where production is initially slow at the beginning of the month, but then quickens in the
last days of a sale or accounting period, for example.
• Sequencing may well involve mixing the types of work processed.
So, for example, when setting up new loans in a bank, the type of loan being processed is mixed to better match customer demand, and help ensure applications are actioned in date order. So often, people are driven by internal efficiency targets, whereby they process the ‘simple tasks’ first to get them out of the way and ‘hit their
numbers’, leaving the more difficult cases to be processed later on.
This means tasks are not processed in date order, and people are
reluctant to get down and tackle a pile of difficult cases at the end
of the week, making things even worse for the customer and the
• Standardising is the third strand of Heijunka. It seeks to reduce
variation in the way the work is carried out, highlighting the
importance of ‘standard work’, of following a standard process
and procedure. It links well to the concept of process manage-
ment, where the process owner continuously seeks to find and
consistently deploy best practice. Remember, however, that you
need to standardise your processes before you can improve them.
Once they’re standardised, you can work on stabilising them, and
now that you fully understand how the processes work, you can
improve them, creating a ‘one best way’ of doing them.
 In the spirit of continuous improvement, of course, the ‘one best
way’ of carrying out the process will keep changing, as the people
in the process identify better ways of doing the work. You need to
ensure the new ‘one best way’ is implemented and fully deployed.
✓ Jidoka concerns prevention; it links closely with techniques such as
failure mode effects analysis (FMEA), which are covered in Chapter 10.
Jidoka has two main elements, and both seek to prevent work continu-
ing when something goes wrong:
• Autonomation allows machines to operate autonomously, by shut-
ting down if something goes wrong. This concept is also known as
automation with human intelligence. The ‘no’ in autonomation is
often underlined to highlight the fact that no defects are allowed to
pass to a follow-on process. An early example is from 1902, when
Sakichi Toyoda, the founder of the Toyota group, invented an
automated loom that stopped whenever a thread broke. A simple
example today is a printer stopping processing copy when the ink
runs out.
Without this concept, automation has the potential to allow a large
number of defects to be created very quickly, especially if process-
ing is in batches (see ‘Single piece flow’, below).
Stop at every abnormality is the second element of Jidoka. The 
employee can stop an automated or manual line if he spots an 
error. At Toyota, every employee is empowered to ‘stop the line’, 
perhaps following the identification of a special cause on a control 
chart (see Chapter 7).
Forcing everything to stop and immediately focus on a problem 
can seem painful at first, but doing so is an effective way to quickly 
get at the root cause of issues. Again, this can be especially impor-
tant if you’re processing in batches.
✓ Just in Time (JIT) provides the other pillar of the TPS house. JIT 
involves providing the customer with what’s needed, at the right time, in 
the right location and in the right quantity. The concept applies to both 
internal and external customers. JIT comprises three main elements:
Single piece flow means each person performs an operation and 
makes a quick quality check before moving their output to the 
next person in the following process. Naturally this concept also 
applies to automated operations where inline checks can be car-
ried out. If a defect is detected, Jidoka is enacted: the process is 
stopped, and immediate action is taken to correct the situation, 
taking countermeasures to prevent reoccurrence. This concept is 
a real change of thinking that moves us away from processing in 
Traditionally, large batches of individual cases are processed at 
each step and are passed along the process only after an entire 
batch has been completed. The delays are increased when the 
batches travel around the organisation, both in terms of the trans-
port time, and the time they sit waiting in the internal mail system. 
At any given time, most of the cases in a batch are sitting idle, wait-
ing to be processed. In manufacturing, this is seen as costly excess 
inventory. What’s more, errors can neither be picked up nor 
addressed quickly; if they occur, they often occur in volume. And, 
of course, this also delays identifying the root cause. With single 
piece flow, we can get to the root cause analysis faster, which 
helps prevent a common error recurring throughout the process.
Pull production is the second element of JIT. Each process takes 
what it needs from the preceding process only when it needs it and 
in the exact quantity. The customer pulls the supply and helps avoid 
being swamped by items that aren’t needed at a particular time.
Pull production reduces the need for potentially costly storage 
space. All too often, overproduction in one process, perhaps to 
meet local efficiency targets, results in problems downstream. 
This increases work in progress, and creates bottlenecks. 
Overproduction is one of the ‘seven wastes’ identified by Ohno 
and covered in Chapter 9.

Takt time is the third element of JIT, providing an important addi-
tional measure. It tells you how quickly to action things, given the 
volume of customer demand. Takt is German for a precise interval 
of time, such as a musical meter. It serves as the rhythm or beat of 
the process – the frequency at which a product or service must be 
completed in order to meet customer needs. Takt time is a bit like 
the beat of the drum on the old Roman galleys for synchronising 
the rowers.

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