Page 289 - Sensors and Control Systems in Manufacturing

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3. Operational level. Day-to-day tasks, such as scheduling, are
performed at the operational level. The primary responsibility
at this level is the effective utilization of the resources made
available through the decisions made on the strategic and tac-
tical levels. Because of the variability in demand or machine
downtime, the planning horizon at this level must be rela-
tively short, normally 1 to 15 days.
While each of these levels has certain responsibilities in a manu-
facturing plant, the objectives are often conflicting. This can be attrib-
uted to inherent differences between departments (e.g., sales and
marketing may require a large variety of products to serve every cus-
tomer’s needs, while the production department finds its job easier if
there is little product variation). One of the main causes of conflicting
decisions is a lack of communication due to ineffective sensors and
control systems between levels and departments. CIM with adequate
sensors and control systems provides the ability to link together tech-
nological advances, eliminate much of the communication gap
between levels, and bring all elements into a coherent production
system.

5.4.2 CIM with Sensors and Control Systems
at the Plant Level
Some of the important emerging concepts related to CIM with effec-
tive sensors and control systems are flexible manufacturing systems,
material handling systems, automated storage and retrieval systems
(AS/RS), computer-aided design (CAD), computer-aided engineer-
ing (CAE), computer-aided manufacturing (CAM), and microcom-
puters. These components of CIM can be classified into three major
groups (Fig. 5.8).

5.4.2.1 Flexible Manufacturing Systems Incorporating
Sensors and Control Systems
An FMS can link several elements on the shop floor through sensors
in order to coordinate those elements. While CIM can be applied to
any manufacturing industry, FMSs find their niche in the realm of
discrete production systems such as job shops.
The most important FMS elements are numerical control machines
and an automated material handling network to transport the prod-
uct from raw material inventory, through the NC operations, and
finally to the finished goods inventory.
Numerical control technology has made major advances with the
advent of computer numerical control and direct numerical control
(CNC/DNC). Microprocessors and sensors located on the machine itself
can now provide the codes necessary for the parts to be operated on.