Page 234 - Sensors and Control Systems in Manufacturing

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4.3 Sensors Tracking the Mean Time
between Operator Interventions
The MTOI value should be matched to the factory configuration in
use. In a highly manual operation, it may be acceptable to have an
operator intervene frequently. On the other hand, if the objective is to
achieve operator-independent manufacturing between manual set-
ups, then the equipment must be designed so that the MTOI is longer
than the planned duration between manual setups. The manufacturer
of automated equipment with adequate sensors and control systems
must try to assess the ways in which factories will be configured and
produce equipment that can satisfy manufacturing needs without
incurring any extra cost due to needed features.

4.4 Sensors Tracking the Mean Time of Intervention
Each time an intervention is required, it is desirable to compare the
intervention interval with that for which the system was designed. If
the intervention time becomes large with respect to the planned mean
time between operator interventions, then the efficiency of the auto-
mated manufacturing equipment drops rapidly in terms of the frac-
tion of time it is available to manufacture the desired product.

4.5 Sensors Tracking Yield
In a competitive environment, it is essential that all automated manu-
facturing equipment emphasize the production of quality product. If
the automated manufacturing equipment produces a large quantity
of product that must be either discarded or reworked, then the opera-
tion of the factory is strongly affected, and costs will increase rapidly.
The objective, then, is to determine the product yields required for
given configurations and to design automated manufacturing equip-
ment containing sensors and control systems that can achieve these
levels of yield. Achieving higher yield levels will, in general, require
additional sensing and adaptability features for the equipment. These
features will enable the equipment to adjust and monitor itself and, if
it gets out of alignment, to discontinue operation.

4.6 Sensors Tracking the Mean Processing Time
If more product units can be completed in a given time, the cost of
automated manufacturing equipment with sensors and control sys-
tems can be more widely amortized. As the mean processing time is
reduced, the equipment can produce more product units in a given
time, reducing the manufacturing cost per unit. Again, automated