issue: April 2003 APPLIANCE Magazine
Assembly & Fastening
Putting It Together
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Lisa Bonnema, Managing Editor
As product cycles get shorter and the word "inventory" becomes taboo, manufacturers are looking for new options when it comes to appliance assembly, hoping to find a synergy between the two crucial aspects of a quality appliance - its design and how it's made.
During the last
few years, it seems the industry buzzword regarding appliance assembly
is flexibility. According to equipment suppliers, there are several
reasons this term has become commonplace on plant floors.
machine design trend is to be able to change over [tooling] in minutes,
maybe simply in the software," explains Pete Doyon, vice president
of Product Management for Schleuniger (Manchester, NH, U.S.). "Batch
sizes have gone down too, so you can't justify having a machine set
up and a long changeover. Also, with all of the manufacturing philosophies,
people don't want inventory on the floor. You only want to build today
what you ship today. So the machines have to be able to be flexible
to be used for a number of jobs. But batch sizes are really what have
pushed the pressure on the changeover times."
Rexroth's newest generation of intelligent SCARA robots - turboscara
SR4, SR6, and SR8 robots - offer appliance makers several advantages,
including simple programming in a Windows(R) environment, TCP/IP
interfaces for data transfer and remote maintenance, and customer-specific
man-machine interfacing through Visual Basic or C++ programming.
The robots are said to be optimized for fast, precise, and flexible
assembly in cleanroom, dust-proof, or standard versions.
general manager of Siemens Dematic Assembly Systems (Birmingham, AL,
U.S.) says that with the current economic conditions, it is also an
issue of cost. "The biggest thing right now is the amount of capital
investment, especially in the U.S., in this kind of line. You're talking
multi-millions of dollars. In order for someone to justify that process
versus foreign labor costs right now, we have to offer very flexible
lines," he explains. "If a customer just wanted to build
a random product order group, they literally could. The goal is to
develop systems where there is either little or zero changeover time
for the customer to achieve that. That is the ultimate justification
right now. The only people that pretty much can afford to do it are
the ones that are given the highest level of flexibility."
The obvious question
surfaces: What solutions are available that will make my assembly processes
more flexible and more cost effective? The answer to that question,
however, isn't easy: the options are many.
shipments of pressure-sensitive (PS) tapes are projected to increase
2.8 percent annually through 2006, according to The Freedonia Group,
tape leaders are expected to include double-coated, adhesive transfer,
and certain plastic film-backed products. According to Freedonia,
growth industries such as electronics and telecommunications are
disproportionately using double-coated tapes.
makers - especially those with varied product lines - have much to
consider when choosing assembly equipment. Making productive decisions
means carefully reviewing the newest technologies and trends while
keeping in mind specific applications.
of manufacturing equipment [available] varies as widely as the applications
do. If you consider appliances to range in size from, say, electric
toothbrushes to refrigerators and dishwashers, you also cover a massive
range of different manufacturing strategies," notes Kevin Gingerich,
marketing manager at Bosch Rexroth, Linear Motion and Assembly Technologies
(Buchanan, MI, U.S.). "In some cases, that might mean manual
assembly stations linked with conveyors; in others, it might mean
full automation with our turboscara and multi-axis Cartesian robots
- or it might mean a mix of the two."
equipment suppliers agree that a major trend right now is to offer
equipment with increased intelligence. Smarter equipment means less
labor, increased productivity, and higher quality.
equipment has improved substantially over the years, as the needs
of manufacturers get fed back into the engineering departments of
capital equipment suppliers. Robots are a great example," says
Mr. Gingerich. "The turboscara robots we're selling now are
technological light years ahead of the SCARA robot invented by Bosch
30 years ago, and even those sold 10 years ago."
He explains: "For
example, all programming software is now Windows-based and has TCP/IP
connectivity, so they can even be programmed and tested via the Internet.
Let's say a customer is installing a robot in California and is not
sure about a certain programming sequence. They can call us in Michigan,
give us the access code to their robot, and we can troubleshoot their
program online. Capabilities like these not only cut hours or days
out of robot installation, they add convenience and cut costs."
adds that many new robots now have absolute encoders so that the
robot always knows where it is in its operating cycle. "You
don't need to 're-home' the robot every time you power it," he
offers an intelligent palette-based conveyor system that utilizes
radio frequency (RF) tags and is said to allow for quick changeover
and flexibility. "The pallet (or fixture) contains universal
tooling, where we are perhaps given 10 or 20 products from the customer
that they would like to build down the same line, and we build the
tooling - either adjustable or very, very quickly changeable - to
carry multiple products," explains Mr. O'Nions. The system has
several appliance applications, including range, washing machine,
refrigerator, air-conditioner, furnace, and dryer production.
on a range, we're carrying anything from single ovens to very wide
double-oven assemblies with cooktops, all on the same pallet," says
Mr. O'Nions. "The way we have achieved that is 'stair-step tooling,'
where the largest product sits at the highest level, and the smallest
product is at the lowest point of the stair step. Each stair step
as you go down the tooling is a different product outline. So we
achieved, in this case, zero changeover time."
He adds that
the specialty is not so much the mechanical solution, but the software
solution. "We carry intelligence on the pallet usually in the
form of an RF tag that carries the data for the particular product.
So we might be only carrying a serial number to start off with, which
would be tied to the system. Then we would automatically route the
pallet to only the operations that were required for that specific
product. That in itself is nothing revolutionary, it's just done
on a very large scale, and we tie that in with recording the test
results. With a range, for example, you measure gas flow, comparisons,
electrical tests, etc. We actually carry the test results on the
RF tag until we get to the end of the system," Mr. O'Nions says.
When the appliance
reaches the end of the process, the tag's information is downloaded
to a host computer system, which records the results. The advantage,
Mr. O'Nions explains, is that if a manufacturer ever has testing
issues or warranty issues, it has the individual test results of
that particular unit by serial number. In addition, once the information
is downloaded, the RF tag's memory is wiped clean and can be used
again for the next run.
Of course, there
are other tactics an appliance producer can use to add flexibility.
Another trend is the concept of modularity. While traditional fixed
conveyors continue to be the best option for some producers, according
to Dynamic Conveyor Corporation (Muskegon, MI, U.S.), light- and
medium-duty manufacturing applications could benefit by upgrading
to flexible, reusable modular systems. The latest modular conveyor
technologies, the company says, can make dramatic improvements in
uptime, agility, overhead, ROI, and other critical business issues.
Dynamic Conveyor, the term "modular" needs to be clarified
in order for a manufacturer to realize the true benefits. Many so-called
modular conveyors and accessories, it says, are actually sectional
units or adaptable accessories, and may suit only limited production
line requirements. While such products, including special belts and
flights, may indeed offer significant advantages, the benefits can
become much more substantial when the entire conveyor system is designed
to be totally modular, the company says.
Henkel Loctite (Rocky Hill, CT, U.S.) offers two patented, industrial-grade,
hand-held pneumatic spray applicators for dispensing 1.75-in
diam areas with hot-melt adhesives. The Hysol 175-Spray unit
achieves 180°C for dispensing EVA hot melts, while the
Hysol 175-Spray HT reaches 195°C for polyamide hot-melt
dispensing. Both 500-W units feature adjustable flow controls
to tailor spray patterns and are said to be ergonomically designed
for operator comfort and application control. In addition,
both applicators feature automatic end-cycle purge to prevent
nozzle clogs, a high melt rate for maximum output, and a fixed-precision
thermostat temperature control for consistent heating.
is certainly one area of appliance assembly that requires manufacturers
to carefully weigh solution benefits and drawbacks. Options range from
clinching and spot welding (see the sidebar, "The Advantages of
Clinching") to self-piercing fasteners and standard rivets.
One joining alternative
that is gaining a lot of attention is the self-piercing fastener.
AKH Inc. (Indianapolis, IN, U.S.) recently introduced its new Double
Headed FAS-NER(R) for appliance applications. The new FAS-NER adds
an external head to AKH's existing Headed FAS-NER, giving the rivet
additional surface area.
FAS-NER system is a punch-and-die operation that automatically feeds,
punches, inserts, and locks the company's patented FAS-NER to form
a flush joint.
pneumatically operated 752V-SS valve from EFD Inc. is said to provide
exceptional accuracy and reliability when dispensing UV-cure adhesives
on automated and semi-automated assembly lines. Here it dispenses adhesive
into a heart pump for a medical application. The valve's design features
no seals or O-rings to wear out and leak. Instead, a precision diaphragm
rated for tens of millions of cycles reportedly ensures long, trouble-free
operation. A fast, clean cutoff at the end of each cycle is said to
eliminate waste, dripping, and cosmetic damage.
The new Double
Headed FAS-NER works the same as the original FAS-NER, explains Dave
Caulk, AKH sales manager. "With this new FAS-NER, we've actually
taken that second-generation of our FAS-NER with the head end on
it - the one end larger diameter than the smaller punch end - and
we just basically put a button cap on top to capture more material
for the thinner top layer so it won't pull out," he says. "For
applications where the flush surface is not a requirement, this Double
Headed FAS-NER is going to give us additional holding capability."
Mr. Caulk, this new FAS-NER is appropriate for any application that
would have a thin, wrapper material, most notably refrigerator cabinets.
If cost is an issue, Wayne Mundsinger, director or Product Application
at Driv-Lok, Inc. (Sycamore, IL, U.S.) suggests using a simple grooved
pin. "[Our] grooved pins can replace a higher cost fastener while
also providing lower assembly costs in many applications," he says. "Historically,
many engineers have chosen ground dowel pins as their mating part locator
solution. This requires an expensive pin and drilled and reamed hole.
A…grooved pin can perform this function without the cost of a reamed
Uses within the
appliance industry include hinges, timers, part-to-part locators,
spring anchors, and motor drives. Because grooved pins are shear
resistant, they are said to be ideally suited for use in locations
without a high degree of end load.
According to Ted Schaumburg, Driv-Lok's director of Research and Development,
the grooves of a grooved pin are formed by a swaging operation. Three
tools penetrate the nominal diameter of the metal at 120-degree intervals.
displaces a controlled amount of metal to each side of the grooving
tool, forming a raised portion along the side of each groove. When
the grooved pin is used, the hole into which the pin is to be inserted
is drilled a few thousandths larger than the nominal diameter of
grooved pin into a hole compresses the expanded portion of the metal,
generating radial holding forces. These radial forces lock the pin
securely into the drilled hole. However, Mr. Schaumburg explains
that it only produces limited radial forces because interference
is only between the hole and the expanded diameter. This system,
he notes, allows the hole size to vary in diameter without generating
detrimental radial stresses.
It's no secret
that appliance design and production need to go hand in hand in order
to achieve today's demand for quick turnaround. While this may require
some customization on the supplier's part, OEMs may also find that
in order to get the most cost-effective solution, flexibility needs
to go both ways.
"There's only a small portion of our appliance products that are standard.
Most of the time we sell a dedicated piece of equipment," notes Steve Sawdon,
president of BTM Corp. "We have to consider the shape of the customer's
part, which depends on how it is designed."
says, it is crucial that manufacturers design their products with
assembly in mind. "Sometimes we ask them to redesign their products
too. That will help us reduce the tooling cost. We also provide them
with flange size and clearance specifications that we like them to
have in order to make lower-cost machines to join their products."
relationship between assembly and design is so strong that one literally
dictates the other. An example of this, according to Mr. Doyon of
Schleuniger, is the use of flexible flat cable (FFC) in appliance
design. The cable, currently being used in Europe for automotive
applications, also offers major benefits to appliance makers, he
explains. The cable is a light-weight alternative to round wire,
which makes it ideal for portable appliances and consumer electronic
products. It also offers production advantages. "The appliance
industry is moving toward using more FFC in manufacturing because
it allows for mass termination, which means labor savings, flexibility,
and increased quality," explains Mr. Doyon. "The fact that
you can mass terminate means that instead of running, say, 12 individual
wires and then terminating them and putting them in a connector housing,
you basically run one piece and terminate on both ends and just plug
The holdup, according
to Mr. Doyon, is the capital investment needed to process the cable. "There
is a cost up front to get capability to process FFC. Most appliance
makers outsource their wire harness assemblies, so as the sub-contractors
gain capability in that area, then it won't be so cost-prohibitive
to start using these new technologies in the appliance design," he
It is important
to note that the equipment is available, Mr. Doyon adds. Schleuniger
currently offers FFC Processing Systems that can be customized for
any application. "What happens is the customer will have an
application, and they'll send us samples and specs. We'll review
it, and we'll build a custom system for their application, based
on standard modules," he explains. "So, rather than have
to redesign from scratch every time, we know that we need to transport
a flat cable up to 3-in wide. Once we know what the customer's needs
are, we can mount the individual process stations on the various
module, and it all ties together with a standard software we developed."
Mr. Doyon says
that until appliance OEMs and wire harness suppliers base their decision
on value instead of expense, the industry will have to wait. "Some
OEMs are even saying, 'We want to use this in our next-generation
design,' but the wire harness manufacturers will quote a really low
price to do it in the current technology, which is discrete single
wires. So, on paper, it looks cost-prohibitive to the OEMs to jump
to that new technology," he explains. "But ultimately,
there will be some sub-contractors that make an investment up front,
and they will go out and look for work. It will happen."
One fastening technique
that is rapidly gaining acceptance among appliance producers is clinching,
the process of creating a joint via punching and squeezing, without
the need for additional fasteners such as screws, rivets, or pins.
According to ATTEXOR, Inc.,
clinching offers several advantages over other fastening methods, specifically
spot welding. "While it is
difficult to tell whether a spot weld is a good one or whether a screw
thread has been stripped, the quality of a clinched joint can be controlled
at any point in time without destroying or disturbing the assembled structure," explains
Dr. Hans Bergkvist, president of ATTEXOR Inc. (Springfield, MA, U.S.)
and ATTEXOR Tools (Ecublens/Lausanne, Switzerland). "This has been
one of the most important arguments in favor of clinching, as well as
the fact that clinching works perfectly on pre-coated, enameled, and
galvanized material found in the appliance industry without destroying
the surface finish."
One of the main advantages
of clinching over spot welding is that clinching can easily join material
couples that are difficult to weld, Dr. Bergkvist
explains. "It is a well-known problem that the punches tend to stick
in aluminum, particularly in larger thicknesses, which can be a major
difficulty when low-weight aluminum profiles are to be joined with sheet
metal. Various ways of solving this drawback have been tried, such as
using a 50/50 alcohol and water spray on the punch side. This mixture
has the advantage of evaporating without leaving any traces that could
have a negative influence on subsequent painting operations. However,
installing and maintaining the spray equipment means additional complications
As an alternative, ATTEXOR has developed patented punch geometries
that are said to significantly reduce the sticking problems. These punch
geometries use double-stroke clinching, the company's proprietary clinching
Dr. Bergkvist also believes that clinching equipment such as his POT
CLINCH(R) Tiger line and the SPOT CLINCH(R) Grip line will replace stitchfolding
machines in applications like vending machines, commercial refrigerators,
machines. One of the main reasons for this, he says, is operator safety.
"In the stitchfolding process, tabs are cut out of the overlapping
material sheets, and they are then folded back to give a staple-like
joint where the staples are made from the base material itself. While
this process is very fast, it presents additional drawbacks over the
risk for hand injuries," Dr. Bergkvist explains. "Operating
quickly means that the tool often gets moved laterally before the punches
have been fully retracted and as a result, they break. Even if replacing
them is rapid, the cost for punches can run up to a considerable amount.
Additionally, a stitchfold joint is not foam tight, requiring tape masking
of the joined material lips before foam is injected between the outer
shell of an appliance and the inner lining."
Steve Sawdon, president of BTM Corporation (Marysville, MI, U.S.) agrees
that recent advancements in clinching have made it the ideal fastening
method in most cases. Specifically, new tooling materials have allowed
his company to further improve its Tog-L-LOC(R) clinching system.
One example of the system's
expanded capabilities was a microwave application performed by BTM's
German distributor. "The microwave was joined
together with the Tog-L-LOC clinching process even though it had some
stainless steel components in its wave guide and body," he says. "That
is fairly new because stainless steel has traditionally been difficult
to join. However, with the advent of some new tool steels, we've been
able to accomplish sufficient joint strength, and the tooling is durable
enough that it can join this harder stainless steel together and can
give the customer acceptable tool life, even in the range of 30,000-50,000
cycles per tool."
According to Mr. Sawdon,
because of the tougher tooling, BTM can now join most metals, including
ferritic stainless steel and austenitic stainless
steel, as well as more ductile metals such as aluminum, copper, brass,
and coated steels.
more than 20 years, Sundance Spas, a Chino, CA, U.S.-based manufacturer
of acrylic hot tubs for the global market, has accumulated an array
of awards and endorsements based on the quality, reliability, and innovations
of its products. The company has always credited part of its success
to the way it assembles its products.
a major reason why the hot tub manufacturer decided to upgrade to
a more efficient method of fastening its hoses to plastic fittings.
The company had been using gluing as their joining method, which
was not only messy, but time consuming.
gluing process included applying the primer to the fitting, applying
glue to the male and female sides, setting the hose to the PVC, and
waiting for the glue to dry. In addition, hoses had to be placed
on the inside of the fittings, which increased the chance of error
because it was often difficult to get exact positioning on how deep
the hose was placed. Inspectors also had a difficult time determining
whether the proper amount of glue had been used, and if the hose
was seated completely against the fitting socket or if had partially
then discovered Rotor Clamp's self-compensating constant tension
band hose clamps (CTBs). The CTB solution not only enhanced spa performance
and increased efficiency by cutting down on defective parts, it also
sped up assembly, according to Bruce Walters, director of Product
Marketing at Rotor Clamp (Somerset, NJ, U.S.). "Their goal was
to save both time and money during manufacturing," Mr. Walter
CTBs made it possible for the hoses to be connected to the outside.
Reducing the number of steps made the manufacturing process more
efficient and constant. In addition, the design utilizing the CTBs
allowed for more flexibility by offering a greater range of tolerance
on the hose and fitting specification.
on the PVC application were viable with the CTBs, whereas gluing
was permanent and resulted in lost resources and ruined
fittings if anything ever needed to be adjusted or replaced.
Another major advantage Sundance received from the CTBs was that they eliminated
any chances of leakage, says Mr. Walters. The clamps compensate for
changes in the joint diameter due to compression set in a hose. This
feature eliminates leaks and the need to re-torque the clamp.
clamps can also be reused. "With any spa or white goods appliance,
our clamps are not a 'one-time' item [to be] thrown away," explains
Mr. Walters. "Should a warranty issue arise and a repair person
is needed to replace a hose, the original clamp can be reused. Crimp-style
clamps, however, must be thrown away and a new one must be installed.
Old-fashioned screw type clamps can be under- or over-tightened, possibly
calling for another service call to the customer. Our constant tension,
self-compensating hose clamps are specifically made for each hose outer
diameter, making installation fool proof."
were three major areas of improvement with the barb and clamp method.
First, instant-use plumbing eliminated the hour-long wait required
for solvent welds to dry before factory testing. In addition, workers
no longer were exposed to VOC (volatile organic chemicals) in solvent
welding. Connections also appeared clean and neat.
to Mr. Walters, there was only one challenge when implementing the
CTBs into Sundance's assembly process. "The main challenge,
like anything new being introduced to an assembly line product, was
change. When people on an assembly [line] are used to doing something,
they are not as open to change," explains Mr. Walters. "By
actually going out on the line with the clamps and special pliers
and showing the worker the ease of installation and cleanliness of
a steel clamp versus messy glue, the process and ease of installation