Eaton is a global technology leader in power
management solutions that make electrical, hydraulic and mechanical power
operate more efficiently, effectively, safely and sustainably. The Eaton
Electric General Supplies is a manufacturing unit that is divided into three
independent production units based on the product characteristics: Sheet Metal,
Turning and Milling, and Copper Bars. The improvement project started at the
Copper Bar (CB) unit.
This CB unit is able to perform a number of
processes, such as punching, trimming, bending, drilling, milling and bench
working. The number of different routings are high. Furthermore, the processing
times per product, per process type, differ also substantially.
The CB unit did have major problems. The
work-in-process was high: sometimes more than 200 jobs in the system. The release
of the jobs was done by the Material Requirement Planning system of the
company, basically a push system. Planners released the jobs, when the process
planning was done. There idea was: the earlier we release jobs, the higher the
probability that the job will be finished on time. The delivery performance was low. The planning department used several priority
rules (urgent, very urgent, super urgent, extreme urgent,) by which they
informed the workers about priorities.
The customers of the CB Unit expect fast and on-time product deliveries, with high quality and at low cost. Reducing lead time (speed) and improving the service level (reliability) is thus of major importance.
In order to realize this, the CONWIP/FIFO/TAKT
system has been developed. Three key lean principles were translated to the
high-variety/low-volume situation of Eaton.
1.
CONWIP:
a limit was set on the number of jobs in the CB unit. This measure takes care
of short average throughput times of jobs.
2.
FIFO:
the workers were stimulated to focus on the oldest jobs in the on-line
scheduling of jobs on the work floor. This principle reduces the variability in
throughput times of jobs.
3.
TAKT:
the time principle was added to the system. The workers should be informed
about their productivity: do they realize the manufacturing target of the day?
The workers in the CB unit are responsible for having no more than a certain number of jobs in the system. The daily output of the CB unit, in terms of the number of jobs, indicates the number of jobs that may be released daily by the planning department. Released jobs are made visible in an input buffer. The first operation in the CB unit was punching. At this station, some nesting of jobs was important to save setup time. The puncher picks the best jobs from the input buffer A.
In order to support the workers in the CB unit, a screen is placed at the work floor that gives information about the Work-in-Process level, the FIFO-priority of jobs, and the extent to which the unit realizes the required TAKT-output.