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Chapter 4 Process design 89
Table 4.1 The impact of strategic performance objectives on process design objectives and performance
Operations performance
objective
Quality
Speed
Dependability
Flexibility
Cost
Typical process design objectives
• Provide appropriate resources, capable
of achieving the specification of product
of services
• Error-free processing
• Minimum throughput time
• Output rate appropriate for demand
• Provide dependable process resources
• Reliable process output timing and volume
• Provide resources with an appropriate range
of capabilities
• Change easily between processing states
(what, how, or how much is being processed)
• Appropriate capacity to meet demand
• Eliminate process waste in terms of
– excess capacity
– excess process capability
– in-process delays
– in-process errors
– inappropriate process inputs
Some benefits of good process design
• Products and services produced
‘on-specification’
• Less recycling and wasted effort within
the process
• Short customer waiting time
• Low in-process inventory
• On-time deliveries of products and
services
• Less disruption, confusion and
rescheduling within the process
• Ability to process a wide range of
products and services
• Low cost/fast product and service change
• Low cost/fast volume and timing changes
• Ability to cope with unexpected events
(e.g. supply or a processing failure)
• Low processing costs
• Low resource costs (capital costs)
• Low delay and inventory costs (working
capital costs)
Process design should
reflect process objectives
Throughput rate
Throughput time
Work in process
Utilization
requesting a product or service and their receiving it. Similarly, if an operation competed on
low price, cost-related objectives are likely to dominate its process design. Some kind of logic
should link what the operation as a whole is attempting to achieve and the performance
objectives of its individual processes. This is illustrated in Table 4.1.
Operations performance objectives translate directly to process design objectives as
shown in Table 4.1. But, because processes are managed at a very operational level, process
design also needs to consider a more ‘micro’ and detailed set of objectives. These are
largely concerned with flow through the process. When whatever are being ‘processed’ enter
a process they will progress through a series of activities where they are ‘transformed’ in some
way. Between these activities they may dwell for some time in inventories, waiting to be
transformed by the next activity. This means that the time that a unit spends in the process
(its throughput time) will be longer than the sum of all the transforming activities that it
passes through. Also the resources that perform the processes activities may not be used all
the time because not all units will necessarily require the same activities and the capacity of
each resource may not match the demand placed upon it. So neither the units moving through
the process, nor the resources performing the activities may be fully utilized. Because of this
the way that units leave the process is unlikely to be exactly the same as the way they arrive
at the process. It is common for more ‘micro’ performance flow objectives to be used that
describe process flow performance. For example:
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Throughput rate (or flow rate) is the rate at which units emerge from the process, i.e. the
number of units passing through the process per unit of time.
Throughput time is the average elapsed time taken for inputs to move through the process
and become outputs.
The number of units in the process (also called the ‘work in process’ or in-process inventory),
as an average over a period of time.
The utilization of process resources is the proportion of available time that the resources
within the process are performing useful work.