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Manufacturing System Design Decomposition™
Responding
to production disruptions
Respond rapidly
to production disruptions
Identifying and
resolving problems relates to throughput time variation caused by unplanned
production disruptions. Any manufacturing system experiences disruptions
and must be able to solve them. This section discusses the decomposition of
FR-R1 “Respond rapidly to production disruptions” and its corresponding
DP-R1 “Procedure for detection and response to production disruptions” as
shown in Figure 1. The main goal of the decomposition branch is to achieve
a manufacturing system that can be improved by being able to recognize and
eliminate weaknesses.
Figure 1: Identifying and resolving problems branch of the MSDD
In order to accomplish
DP-R1, disruptions must be recognized (FR-R11), communicated to the right
resource (FR-R12), and eventually be solved (FR-R13). The associated DP’s
are conceptual and refer to sub-system configurations (DP-R11), feedback
procedures (DP-R12), and standard improvement methods (DP-R13). The
dependencies follow the logic that disruptions must first be recognized,
then communicated and then resolved (see Figure 2)
Figure 2: Decomposition of requirements to reduce variability in
throughput time.
The underlying
thinking of the decomposition of DP-R11 is that the sub-system
configuration (design and operation) supports the operator in recognizing
disruptions (when, where and what). Technology can be a great help in
achieving these goals by providing instantaneous feedback about the state
of the manufacturing system. However, the perspective taken here is that
the operator is the ultimate source of dealing with disruptions, which is
expressed in the wording of DP-R11 and DP-R12.
Minimize
production disruptions
Rapidly responding to
and resolving of production disruptions creates the basis to eliminate
production disruptions. To minimize production disruptions (FR-P1),
predictable production resources are required (DP-P1). Four types of
production resources must be predictable: information (FR-P11), operator
(FR-P12), equipment (FR-P13), and material (FR-P14), as shown in Figure 1.
Figure 1: The output of production resources must be as predicable
as possible.
Figure 1 highlights
the importance of a capable and reliable information system (FR-P11). An
information system allows the gathering and storing of data, its
transformation into information, and the transfer of information from
sender to receiver. Thus, the information system supports the achievement
of predictable output from all resources of the manufacturing system by
providing timely, reliable, and relevant information.
The decomposition of
FR-P12, “Ensure predictable equipment output,” and its corresponding DP
stresses that equipment must be designed for serviceability (FR-P121) to
achieve successful maintenance (FR-P122). Further details about equipment
maintenance can be found in the literature of total productive maintenance
[e.g. Nakajima, 1989].
There are numerous
norms and guidelines for the design of work systems from ergonomic to
psychological aspects to achieve stable operator output (FR-P13) [e.g.
ReFa, 1993; Grote et al., 2000]. Quality and cost aspects of standard work
procedures are covered by DP-Q122 for stable quality output and by the
decomposition of the direct labor branch (DP-D1). Three requirements are
defined to achieve stable time output from operators as shown in Figure 1:
reducing variation of task completion time (FR-P131) by defining standard
work methods (DP-P131); ensuring that operators are available when tasks
need to be performed (FR-P132); and avoiding production disruptions due to
worker allowances (FR-P133) by mutual relief (DP-P133). Cross training also
increases operators’ competence and flexibility and helps to improve
quality and reduce costs.
The performance of
standard work influences the availability and delivery of material. Thus,
DP-P13 affects FR-P14 “Ensure material availability” (see arrow between
DP-P13 and FR-P14 in Figure 1). FR-P14 requires parts to be available when
demanded (FR-P141) and to ensure proper timing of part arrival at
downstream processes (FR-P142). Standard Work In Process (SWIP) between
subsystems (DP-P141) serves as a buffer against production uncertainties
and transportation delays. Low volume manufacturing may require a different
strategy to ensure part availability, since it might not be possible to
keep standard amounts of material between the manufacturing processes.
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