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demonstrated its efficacy [5–9]. Following the benchmark-
ing perspective, as well the use of a contrasted tool,
facilitates the interchange of improvements. It is a tool that
provides communication solutions for practitioners to
obtain maximum efficiency and definitions of theoretical
development points to become a reference among redesign
techniques [8]. The recent criticism [29] only shows that
this tool continues being adequate and its flexibility has
allowed to adapt it to complex situations [5]. A detailed
description of VSM can be seen in Rother and Shook [30].
Thus, as improvement tool simplifies the measurement of
times without added value, so the calculation of indexes of
lean metrics is easier and it is possible to enhance the
operative actions with strategic results.
This paper unifies several gaps and it shows how
redesign operative actions can achieve high levels of
performance in a short time and in a real industry, inside
a context of an assembly line with a small space, and that it
requires flexibility, that it is studies in-depth. The academic
literature requires of similar case studies [15].
3 Methodology
Methodology is based on the continuous improvement.
Consequently, it will be a continuous process of status
study, calculation of metrics, implementation of progress,
observation of the results, and new decision-making of
improvement.
A first design of VSM is realized according to the
original data from production processes and the layout,
identifying the key times of each workstation. This design
represents the starting point of improvement. Next, the map
950 Int J Adv Manuf Technol (2009) 43:949–958of the parts flow is shown to verify the materials movement
between the workstations, calculating the productive and
unproductive times, stocks and metrics that will help to
characterize the process, and marking some targets of
progress. This design of the VSM allows the beginning of
the progress in the manufacturing line [30]. Metrics used
are DtD and LR. DtD depicts the material flow through the
value stream, the time it takes for material to flow from the
receiving dock (or order entry point) to the shipping dock
(Eq. 1). LR is the ratio of working time of added value to
DtD or throughput time (Eq. 2):
DtD ¼ Time for material flow through value stream; ð1Þ
LR ¼ Added value work time
DtD : ð2Þ
Another important issue is to regulate and reduce the
accumulated stocks. Consequently, it will be necessary to
establish a control of the accumulated stock. The control
will be accomplished easily in accessible stores and
shelves. This activity facilitates the management of parts
waiting to be processed because the visual control is more
effective. It will use the takt time [6, 20, 24], a fully known
lean metric (Eq. 3), as Eq. (4) defines:
Takt time ¼ Total time available for production per shift
Required numbers of parts per shift
;
ð3Þ
Stocks ¼ Time of entire stepTime added value
Takt time
: ð4Þ
Once the takt time is defined, it is possible to establish
the cycle time, a basic parameter in pull system [6, 24]. So,
traditionally, objectives such as high machine utilization
and high production volume are less important when the
takt time is defined because the aim is work within the time
[20]. However, a better materials flow can conciliate both
objectives: work within the takt time and higher LR.
Next, the necessary progress will be implemented to
achieve the desired state of the manufacturing process.
There are two main improvements: firstly, it is a system to