The goal of manufacturing systems
today is to fulfill the ever growing demands of customers, which
requires a greater amount of flexibility in the manufacturing process.
Innovative production approaches are needed that will allow companies
to deliver a large variety of products at a low cost and with short
production cycles. Flexible manufacturing work cells provide excellent
opportunities for enhancing both efficiency and productivity in
an automated manufacturing environment.
Flexible manufacturing work
cells have minimal downtime and maintenance, maximum product family
range, the ability to adapt to variability in materials and process
conditions and the ability to handle increasingly complex designs
and technologies with minimum disruption and at reduced cost levels.
Such cells typically integrate robots, a wide variety of machine
tools, material handling equipment, packaging devices, sensors,
actuators, controllers, and similar other hardware.
Flexible work cells use high level distributed data processing
and automated material flow, which is enabled by highly flexible,
computer controlled material and information processors within
an integrated, multi-layered feedback architecture. In order
for flexible work cells to become economically viable they
reduce the Manufacture Lead Time, (MLT), or total time required
to manufacture a given part, and 2) the partially completed
inventory. Ideally, a flexible work cell is aimed to minimize
key idle times that comprise the MLT:
i) the setup time for machines to adapt manufacturing from one
part to another,
ii) the process (or manufacturing) time of those machines operating
on the part being machined,
iii) the move time from one machine to another, and
iv) the waiting time for a part to be taken up to the next process.
Maintaining high cost performance is important because flexible
systems are apt to generate idle machining time. The speed at which
various cells operate and the close scheduling of processes are
crucial in minimizing machine idle time. The flow of work materials
for automatic manufacturing systems, with small lot sizes is not
fixed, while that of mass production is; hence, the idle time is
a variable that can be optimized.
Recent advances in hardware and software have made flexible manufacturing
systems capable of handling relatively complex tasks with a modest
and affordable investment. Much of the credit for this development
lies with the advent of fast microprocessors, and sophisticated
robotic manipulators and end-effectors. The use of multiple robots
and their coordination via intelligent control strategies has expanded
the capabilities of flexible manufacturing to satisfy a wide spectrum
of industrial applications. A response to changing market requirements,
product designs, and technological developments can be easily accommodated.
Moving parts from one place to another and loading and unloading
machines automatically has been an important and crucial aspect
in flexible manufacturing systems. Currently, it is feasible to
handle the movement of parts during manufacturing very efficiently
using the existing technology. As the motion of parts progresses
along the manufacturing line, the vision sensor system identifies
them via a bar code or a magnetic tag attached to the part. By
the time the part reaches a machine tool, it is picked up by a
robot and is properly positioned to be worked upon by the tool.
The currently available vision systems are quite versatile. They
can easily accommodate identification of fast moving parts, misoriented
or mispositioned parts, or parts yielding blurry images.