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Part Three
Planning and control
Figure 15.10 Levelled scheduling and mixed modelling: mixed modelling becomes possible
as the batch size approaches one
The 5 Ss
individual products emerging from the unit could be reduced progressively as illustrated
in Figure 15.10. This would produce a steady stream of each product flowing continuously
from the unit. However, the sequence of products does not always fall as conveniently as
in Figure 15.10. The unit production times for each product are not usually identical and
the ratios of required volumes are less convenient. For example, if a process is required to
produce products A, B and C in the ratio 8:5:4, it could produce 800 of A, followed by
500 of B, followed by 400 of A, or 80A, 50B, and 40C. But ideally, sequencing the products
as smoothly as possible, it would produce in the order ...BACABACABACABACAB ...
repeated ...repeated ...etc. Doing this achieves relatively smooth flow (but does rely on
significant process flexibility).
Keep things simple – the 5 Ss
The 5-S terminology came originally from Japan, and although the translation into English
is approximate, they are generally taken to represent the following.
1 Sort (Seiri) – eliminate what is not needed and keep what is needed.
2 Straighten (Seiton) – position things in such a way that they can be easily reached whenever
they are needed.
3 Shine (Seiso) – keep things clean and tidy; no refuse or dirt in the work area.
4 Standardize (Seiketsu) – maintain cleanliness and order – perpetual neatness.
5 Sustain (Shitsuke) – develop a commitment and pride in keeping to standards.
The 5 Ss can be thought of as a simple housekeeping methodology to organize work areas
that focuses on visual order, organization, cleanliness and standardization. It helps to eliminate
all types of waste relating to uncertainty, waiting, searching for relevant information,
creating variation, and so on. By eliminating what is unnecessary, and making everything
clear and predictable, clutter is reduced, needed items are always in the same place and work
is made easier and faster.
Adopt total productive maintenance (TPM)
Total productive maintenance aims to eliminate the variability in operations processes caused
by the effect of breakdowns. This is achieved by involving everyone in the search for maintenance
improvements. Process owners are encouraged to assume ownership of their machines
and to undertake routine maintenance and simple repair tasks. By so doing, maintenance
specialists can then be freed to develop higher-order skills for improved maintenance systems.
TPM is treated in more detail in Chapter 19.