As we enter
the new millennium, it might be constructive to critique the many
changes we are experiencing in the way we must do business to survive,
grow and prosper in an ever changing and expanding global market.
Market pressures have never been more demanding, whether we are
in the automotive or non-automotive sectors of the world economy.
In the U.S.
market, there are tremendous changes occurring in our manufacturing
facilities today to keep competitive and still maintain ever-increasing
product quality standards. We are forced to find and implement better
methods and procedures to meet ongoing global market demands. Many
companies are developing the "Kaizen" approach to Continuous
Improvement Programs, (TQM) Total Quality Management, ISO 9000,
etc.
In the field
of grinding, polishing, buffing and deburring, both large and small
manufacturing plants must continue to upgrade their finishing operations
and facilities. Manual finishing methods are becoming less desirable
and highly ineffective as we plan to meet future manufacturing goals
and projections. The available labor force today typically is not
interested in working in "dirty" polishing departments,
as there are many other much more appealing job opportunities. Also,
current environmental rules and regulations help to discourage and
limit hand grinding and deburring approaches in most U.S. plants.
There is a definite trend to minimize hand-finishing operations,
as well as to replace many of the older and long established polishing
and buffing machines. Another option is to send this type of work
off shore to the Far East, India, Latin America or Mexico; however
this is not a good long-term solution. Problems with extended deliveries,
excessive inventory of parts, additional shipping costs, quality
issues and overall control negatively affects U.S. companies trying
to find alternative sources to meet high-quality part supplies at
controlled costs.
In defining
mechanical finishing of specific part types related to various industries,
basic categories can be classified under "decorative"
and "functional."
Decorative
Parts
Most
metalworking plants are faced with market pressures to upgrade their
products in appearance and performance, as well as improve their
manufacturing cost base to better meet domestic and worldwide competition.
Especially on decorative consumer products that are coated or plated,
significant manufacturing costs are directly related to polishing
and buffing operations. Preparation by mechanical surface finishing
is important for decorative lock and plumbing hardware, hand tools,
cookware and appliances, lamps and lighting fixtures, golf clubs,
motorcycles, handguns and rifles, aluminum extruded building products,
automotive bumpers and cast aluminum wheels.
Functional
Parts
On functional internal part components that affect product efficiency
and performance, deburring and super finishing are becoming important
secondary operations. With extended part warranties, such as in
the automotive field, quality control to ensure the integrity of
the part components becomes a key cost factor. Specifications for
surface finish and geometry of bearing and load surfaces for transmission
shafts, gears, yokes, drums, axles, camshafts, crankshafts, connecting
rods, pistons and engine blocks are being continually upgraded.
Other non-automotive applications requiring better controlled surface
finish and tolerances are found on truck and earth moving vehicles,
medical prostheses or implants, pump screws and valves, air compressor
and air conditioner components, motor rotor components aircraft
engine compressor discs and blades, aircraft frame components, and
hydraulic telescopic cylinders.
The examples
listed above represent only a portion of the total mechanical surface
finishing applications that are influenced by current market factors.
These market factors are causing many changes in the way we control
and operate our plants.
Market
Factors
The following
are market factors that affect decision making regarding mechanical
surface finishing operations and equipment.
- There is
a need for greater machine flexibility in finishing a wider range
of products on a common system with greater emphasis on rapid
machine changeover, simplified tooling and combined finishing
operations within the same system.
- The quality
level required continues to rise worldwide. Both cosmetic and
functional finishing specifications are better defined and controlled
by continuing market pressures. Part geometry, uniformity and
consistency relative to surface finish as well as visual specifications
are essential as a result of continuous quality improvement programs
established in the automotive and non-automotive industries. Kaizen,
TQM, ISO 9000 and QS 9000, represent current examples of how we
must conduct our businesses today and in the future to maintain
our companies as qualified and acceptable suppliers to our customers.
- Competitiveness
in the marketplace is an ongoing factor. Finishing costs have
traditionally been significant, especially on decorative consumer
items. Not only have the labor costs been substantial, but also
the cost of buffs, compounds, abrasive belts, wheels and brushes
have been key contributors to the overall cost of the end product.
There has been a definite trend to develop more cost-effective
ways to finish products. Product development in the areas of buffs,
compounds, abrasive belts and wheels, nylon belts, brushes and
wheels and micro-polishing rolls has been a challenge to abrasive-media
manufacturers. There are many new products and options available
today to help maintain higher quality surface finishing standards
at controlled costs.
a. A
recent example in the field of coated abrasive belts, is the
development of "structured abrasives." Coated abrasive
belts use a technology known as "microreplication,"
which has given the ability to obtain precisely shaped composite
grains bonded to a belt backing. More uniform fine belt finishes
can be achieved to reduce sequential belt steps, extend belt
life and ultimately improve final surface quality finishes
at reduced operating costs.
- Stricter
enforcement of laws regarding operator safety, plant working conditions
and hazardous waste disposal has created a tremendous burden on
our manufacturing plants, to the point where many of the job shops
and smaller plants can no longer financially assume the costs
incurred in meeting these requirements. OSHA and other environmental
regulations continue to be enforced by local, state and federal
agencies to help improve plant safety and overall working conditions.
Custom designed machine enclosures are becoming much more common
on finishing systems in order to protect the operator in terms
of reduced noise levels, dust and dirt air contamination, and
overall machine safety and exposure to potential plant hazards.
- High hidden
costs related to carrying in-process inventories, based on traditional
batch-type manufacturing operations, have forced most manufacturers
to investigate better methods of handling and scheduling production
parts throughout the plant. "Just-in-time" (JIT) manufacturing
and "single-part flow through" are two examples of improved
inventory control being used throughout many manufacturing plants.
Specialized work cells combine a number of machining and secondary
finishing operations, using common operators to perform multiple
tasks within a given work cell. In these cases, common part families
can be conveniently routed within each line.
- Labor shortages
of qualified and trained personnel continue to affect most U.
S. manufacturers. Local, state and federal training programs are
being expanded, but this does not solve the complete problem.
There must be other ways to offset the lack of qualified labor
pools. Programmable and flexible finishing systems can also help
to offset reduced labor conditions.
Robotic
and Programmable Controlled Finishing Systems
As
an answer to many market conditions and pressures outlined above,
electronic and computer hardware and software technology have been
developed for grinding, polishing, buffing, deburring and satin
finishing. Examples of current applications illustrate a variety
of computerized and programmable electronic systems that have been
integrated into basic mechanical finishing equipment and processes.
These systems
address many of the critical market factors challenging modern manufacturing
environments.
- Machine
flexibility and rapid changeover;
- Improved
part quality and consistency of finish;
- Reduced
finishing costs and better utilization of abrasive media;
- Operator
safety and environmental regulations;
- Improved
parts handling and scheduling procedures to minimize inventory
and in-process manufacturing costs; and
- The growing
shortage of trained and qualified or willing labor.
The machine
tool industry has been making excellent progress in addressing the
market conditions and pressures outlined above. New programmable
computer technology using Robotic, PLC, CNC and PC-based devices
applied to mechanical finishing systems for grinding, polishing,
buffing, deburring and satin finishing can be integrated into many
robotic and programmable controlled finishing systems.
The following
robotic and programmable controlled finishing systems illustrate
and describe a variety of finishing applications for automotive
and truck aluminum wheels, telescopic hydraulic cylinders, lock
and plumbing hardware, aluminum building extrusions and a complete
family of stainless steel ball valves. These typical applications
cover a series of diverse mechanical finishing requirements necessary
to establish typical bench marks into the new millennium.
Case
1: Aluminum Cast and Forged Wheels
The
automotive and truck industry has created a growing demand for bright
aluminum cast and forged decorative wheels. Figure
1 shows a variety of wheel designs, which are presently automatically
polished and buffed to a uniform mirror finish. For high production
requirements, Figure 2 illustrates an eleven
head rotary system provides the operator with maximum buffing control
in "cut" and "color" buffing automotive cast
wheels. In this case, the wheels are fixtured vertically to easily
satisfy the parts handling of the smaller automotive wheels. With
eleven workstations, electronic and programmable controls assist
the operator to better monitor and control the machine for rapid
set-up and production operations.
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In
Figure 3, specially designed Acme O.D. and I.D.
individual buffing heads perform a series of "cut" and
"color" buffing operations on the inside surfaces of 22-
and 24-inch diameter truck wheels on a large index table with wheels
fixtured horizontally having specialized tooling for easier part
handling.
An alternative
wheel buffing system for lower volume requirements provides a five-axis,
four workstation machine as shown in Figures 4 and
5. A (CNC) computer numerical controlled buffing machine provides
maximum flexibility for rapid machine changeover. Minimum tooling
allows the four-station system to be more cost-effective for a variety
of automotive wheel buffing requirements. The basic four-head arrangement
can be set up for "cut" or "color" tangent wheel
buffing or wide wheel "mush" buffing to meet lower production
requirements. Various wheel designs are preprogrammed on the five-axis
system, allowing machine changeover in a matter of minutes.
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Case
2: Four-Head Abrasive-Belt Centerless Tube Grinding System
A
Four-Head Fully Programmable Centerless Abrasive Belt Grinding and
Polishing System provides high stock removal on telescopic hydraulic
cylinder tubes on a "single-pass-through" operation. A
15-axis programmable controlled system is shown in Figure
6. Approximately 0.60 inch stock removal can be ground to a
controlled finish and precise tolerance standards on thin-walled
D.O.M. tubing from 1-10 inches O.D. "Smart-Screen" operator
controls allow complete machine changeover normally in less than
five minutes.
The abrasive
belt grinding process and the automatic tube handling system help
provide a very cost effective and productive integrated system for
high volume O.D. tube and rod grinding when compared to other methods,
including bonded wheel centerless grinding and CNC turning. This
method of centerless abrasive belt grinding has become a universal
standard in the hydraulic cylinder industry for both low and high
production requirements for tube and rod finishing on many types
of truck lift cylinders in the United States, Canada, England and
Brazil.
Case
3: Brass Lock Hardware
High production, continuous, in-line buffing and satin finishing
systems with programmable controls for rapid machine changeover
offer maximum flexibility to finish brass doorknobs and rosettes
for a variety of different lock hardware styles. Production rates
of 6,000 parts per hour are feasible.
Figure
7 illustrates an in-line conveyor machine with seven adjustable
buffing heads. They are controlled by a "smart-screen"
with menu-driven software (Figure 8) for ease
of operator control. The buffing heads are equipped with automatic
head positioning through a Programmable Logic Controller (PLC) system.
This concept allows the manufacturer to produce at high rates and
still have the ability to changeover quickly to other part styles
to meet "just-in-time" production scheduling goals.
Case
4: Brass and Aluminum Levers
One of twelve robotic finishing work cells for decorative lock hardware
uses coated abrasive belts and nylon abrasive belts/wheels to satin
finish various door levers in a programmable work cell. The overall
systems shown in Figures 9 - 10 show how an
Acme designed over and under and a six-sided part server are integrated
into the systems. These arrangements allow the robotic cells to
run for several hours without need of operator attention. The indexing
part server is designed to allow the addition of a second robot.
This will double output without adding additional material handling.
The robotic
cell is completely enclosed in a sheet metal housing to meet safety
and environmental requirements. Figure 12 shows
the robot satin finishing the underside of a brass lever using a
nylon abrasive wheel for consistent and uniform cosmetic finishes.
Case
5: Brass Plumbing Castings
A
variety of different brass cast plumbing housings, bases and faucet
spouts are ground and polished in a robotic work cell, as shown
in Figures 13 to 16. The parts are selected
from multiple queuing trays. Dual trays provide a continuous part
supply to the robot for approximately one to two hours, as shown
in Figure 13. A series of four coated abrasive
belt operations rough grind and finish polish the contoured shaped
brass castings on a consistent and repeatable basis. Custom software
provides the operator with a simplified menu-controlled screen for
changing part programs and maximizing the abrasive belt life by
use of programmable force-control and variable belt speeds on the
grinding/polishing heads.
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Case
6: Aluminum Extrusions
The buffing of aluminum extrusions can be programmed on a 4-ft wide
by 24-ft long stationary worktable in conjunction with a wide traversing
buffing head. A series of extrusions can be preloaded on interchangeable
work platens for more efficient part handling to maximize "up
time" on the buffing table. The basic machine, Figure
17, is enclosed in a sheet metal house to control the environmental
conditions from the operator. The operator can load the fixtured
worktable outside the house enclosure from both sides of the machine
(Figure 18). A programmable control system
is provided with a CRT screen for ease of operation control and
monitoring. An automatic multiple spray gun compound system is mounted
on a 40 hp, 4-ft wide traversing buffing head for "cut and
color" buffing operations. Satin finishing operations can also
be adapted when using nylon abrasive finishing wheels for added
machine flexibility.
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Case 7: Stainless Steel Ball Valves
A
robotic work cell is capable of abrasive belt polishing and buffing
to a mirror finish a family of stainless steel ball valves in sizes
from 1-12 inches O.D. In Figure 19, the robot
is located on a common base with two belt heads and two buff heads,
with exhaust ducts mounted in the base and connected to an exhaust
system for dust collection evaluation. In Figure
20, the family of ball valves are fixtured on queuing trays
with dual drawers for intermittent operator load and unload, without
affecting the robot operation. The robot controls are provided with
"operator friendly" software through a Smart Screen for
ease of operator control. The 12-inch O.D. ball valve, weighing
90-100 lb, is the largest ball valve of many sizes to be programmed
in the robotic work cell. This particular application demonstrates
excellent flexibility of a robotic work cell performing a number
of difficult edge deburring and super finishing operations that
were previously performed in manual operations.
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It is important
to note that many manual operations of this type are being converted
to robotic polishing and buffing methods. The manual fatigue factor
of handling the larger ball valves is now minimized at greatly reduced
cycle times for a very cost effective operation. In addition, new
structured abrasive belt products help to provide more efficient
belt polishing operations by reducing the number of abrasive belt
sequences in order to achieve a final mirror finish throughout the
ball valve family of parts.
Case
8: Robotic Grinding, Polishing, and Buffing of Orthopedic Implants
Another classic benchmark robotic application includes the grinding,
polishing, and buffing of knee implant prostheses parts, which in
the past had required an equivalent of 15-20 manual polishers to
perform the work of one robotic work cell (Figures
20 and 21) Acme robotic work cells have evolved to a level where
grinding and polishing can combine gate removal, contour and tolerance
grinding, and super finishing of chrome-cobalt investment cast knee
and hip implants using very sophisticated finishing technology.
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In summary,
the global market factors will continue to push our manufacturing
and finishing concepts to higher levels of achievement. The changes
in mechanical finishing for cosmetic and functional part products
have been greatly influenced through growing technology of robotic
and computer controlled finishing processes and systems. Progressive
companies today must support and encourage continuous improvement
and concepts in order to grow and maintain a strong position in
their particular future markets. As we move into the new millennium,
these changes will continue to expand throughout the U.S. and the
world economy.
