FLEXIBLE MANUFACTURING CELLS
The
flexible manufacturing cell (FMC) is a miniature FMS system, but not as large
or complex. Basically, the FMC consists of three elements: the machines, a part
conveying system, and the cell controller.
Machines
The
type and quantity of machine tools used in a flexible manufacturing cell depend
on the family of parts to be machined and the size range of the parts. These
conditions may require one, two, or even four units to do the necessary work.
For example, in one machine in the cell the rotary operations will be
performed and then the semi-finished part transferred to another cell machine
for the other operations required. The turning center and machining center are
good choices for a cell design, but other machines such as coordinate measuring
machines, part-washing units, or equipment can be added to the system. The
characteristic that is common to a cell is the link of the CNC machines to a
cell controller or simplified host computer.
Fig. 10-3-17
A stand-alone machining center
serviced by a multi-pallet system. (Giddings & Lewis, Inc.)
There are three main manufacturing systems used
to provide productivity and flexibility to suit product volume and variety.
These are the stand-alone manufacturing center, manufacturing cell, and the
flexible manufacturing system:
-
The
stand-alone manufacturing
center
consists of a
multi-pallet system working with a machining center, Fig. 10-3-17. It can
have several parts in process at the same time, selecting them at random
from a pre-loaded queue (line) of parts on pallets. This type of system is
popular because of the multi-pallet design and the minimum attention it
requires during production. When production requirements increase beyond
the capability of the stand-alone manufacturing center, it can be fitted
(integrated) as a module into a flexible manufacturing cell.
-
The
manufacturing cell
consists of a group of processing modules
joined to handle a family of parts and complete all the manufacturing
operations before the part leaves the cell. There are three types of
manufacturing cells generally used to suit various production purposes—the
palletized, robot or automated, and the FMS cell.
Fig. 10-3-18
A palletized cell is used to
machine high-variety low-volume parts. (Giddings & Lewis, Inc.)
-
The
palletized
cell
, Fig. 10-3-18, is
generally used where high-variety, low-volume production is required.
Material handling joins a group of flexible general purpose machine tools
using a common pallet design with pre-fixtured parts on pallets. The
parts generally flow between two or three stations and the cells do not
have central computer control with real-time routing, load balancing, and
production scheduling logic.
Fig. 10-3-19
The robot or automated cell
consists of various CNC machines serviced by a robot or material-handling
system. (Giddings & Lewis, Inc.)
-
The
robot or
automated cell
, Fig.
10-3-19, consists of a group of CNC machines linked together with
robotics or specialized material handling. It is generally used for the
high-volume production of a small, well-defined, homogeneous family of
parts.
Cells usually have a fixed process and an
orderly flow of parts between operations. The cell becomes a fully-automatic
process through the use of robotics, power clamping of parts, special tools,
and other forms of automation.
Fig. 10-3-20
The FMS cell has automated
material flow, machines the part, and removes the finished part. (Giddings
& Lewis, Inc.)
-
The
FMS cell
, Fig. 10-3-20, is a distinct machine
group within an FMS. The characteristics of this cell are the automated
flow of raw material to the cell, total machining of the part across the
machines within the cell, and then the removal of the finished part.
The FMS cell is a station in a larger automated
manufacturing network, where material-handling devices can link various cells.
These systems approach the concept of a computer-controlled factory.