(Steve Krar, Consultant – Kelmar Associates)
present era of intense global competition is leading U.S. companies toward a
renewed commitment to excellence in manufacturing. Attention to the quality of
products and processes, the level of inventories, and potential improvements in
productivity gained through high tech automation has made manufacturing once
again a key element in the strategies of companies intending to be world-class
meet the demand for a good selection of high quality, reasonably-priced
products, flexible manufacturing systems (FMS) allow manufacturers to quickly change
manufacturing operations to produce any product, at any time, while maintaining
an economical operation. Flexible manufacturing systems (FMS) are one of the
most efficient ways of reducing or eliminating manufacturing problems. FMS is a
manufacturing solution that leads to improved profitability by reducing lead
times and inventory levels, rapid response to market changes, lower labor
costs, and improved manufacturing productivity.
FMS consists of a variety of CNC
machine tools serviced by a material-handling system under the control of
computers. (Cincinnati Machine, A UNOVA Co.)
flexible manufacturing system generally consists of a number of CNC machine
tools and a material-handling system that is supervised (controlled) by one or
more dedicated executive (supervisory) computers, Fig. 10-4-1. A typical
flexible manufacturing system can completely process the members of one or more
part families on a continuing basis without human intervention. FMS brings flexibility
to manufacturing so that a part can be produced when the market requires it,
and not when it is most suitable for production. The system is also flexible
enough to suit changing market conditions and product type without buying other
equipment. FMS can use equipment in off-hours (second and third shifts) when it
is not normally used. This is a major stepping-stone to unmanned manufacturing
and the factory of the future.
WHAT IS FMS?
are many definitions of FMS depending on the user’s point of view. The
following definition applies in most cases:
group of CNC machine tools, linked together with an automated
material-handling and inspection system, and controlled by a central
computer that can randomly process a group of parts and adapt automatically
to changes in parts production, mixes, and levels of output.
NEED FOR FMS
key objective in manufacturing is to get the right raw materials or parts to
the right machines at the time they are required. Leaving too much material or
getting to the machine too soon creates too much material tied up in in-process
inventory. Too little or too late causes delayed work schedules and idle
machines. The result in many cases is a poor use of capital, in the form of
excess in-process inventory or underutilization of equipment.
The use of equipment and
facilities in an average manufacturing operation during a year.
are a total of 8760 hours in one year that can be available to manufacturing
operations, Fig. 10-4-2. In a typical manufacturing operation:
44% of the total time available is lost due to incomplete use of second
and third shifts.
of the total time is taken up by vacations and holidays.
is lost while machines are being set up for the next operation or parts
are being loaded or unloaded.
4% of the time is lost due to process difficulties or unforeseen material,
tooling, or quality-control problems.
leaves only 6% of the total time for actual production.
manufacturer’s capital investment for equipment, and facilities is working,
trying to pay for itself, less than one hour in seventeen.
A percentage of time spent on
typical manufacturing operations.
have shown that in a typical manufacturing operation a part moving through a
metal-cutting operation would be on an individual machine tool only 5-6% of its
total time in manufacturing, Fig. 10-4-3. When a part is on a metal-cutting
machine tool, and a cutting tool is removing material 1.5-2% of the part’s
total manufacturing time and actually performing work and adding value. The
other 95% of the time, the part is either moving through the shop or waiting in
line for the next operation.