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While the Planner’s reasons for selecting a practical solution
are often intuitive, the Heijunka planning tool has a tangible goal –
stability or smooth flow in production. Thus there is a
mathematically attainable goal for optimisation. To achieve this
goal the Heijunka planning tool runs thousands of scenario daily
using Monte Carlo simulation techniques. It then selects from the
best of these results.
The output is the hourly, daily, weekly and monthly plans for
the lines.
In addition to stability of the production plan and lower
stock holding, the Heijunka planning tool provides security to the
business because planning constraints are explicitly captured and are
not reliant on person centred experience.
Many of the rules used by the Planner and other key
operational persons can be captured through an interview process.
However, there are other planning rules that will be “tacit”. That
is, they are used by the Planner but remain unspoken – often because
the Planner only understands them at an intuitive level.
Over time the Heijunka planning tool captures and incorporates
these rules.
By interrogating the output of the Heijunka planning tool with
the Planner and other key operational persons and comparing them to
the decisions the Planner would recommend, these “tacit” rules will
be exposed. Through this process the sophistication of the Heijunka
planning tool rapidly improves as more and more of the planning
constraints are incorporated into the algorithm.
The smoothing of the production plan that results from
implementing Heijunka planning will decouple the plant from the
higher variability of the market pull. The introduction will be
based around the practical ability of the plant to change from
product to product.
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