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Hydroforming
with a Spin
By Steve
Paluszynski
Metalspun Products Co., Inc.
In metalspinning,
flat metal disks, or pre-formed metal workpieces, are formed over
the mandrel on a metalspinning lathe into conical, hemispherical,
and cylindrical shapes. Though advances in CNC technology are making
the process faster and more accurate, there is still a great deal
of traditional handspinning. In this method, a mechanic uses a levered
hand tool to force the blank to conform to the shape of the mandrel
while the metal workpiece is spinning.
This cold-forming
process is well suited to low volume production. As quantity requirements
increase, stamping usually becomes more cost effective, especially
if the stamping tool requirements are nominal.
Sometimes it
appears metalspinning has been used to produce a part that was a
candidate for the deep draw process. But the cost of deep draw tooling
can be a deterrent to deep drawing parts in small lots. And the
shape of a part can become too complex or too difficult to deep
draw.
Metalspinning
is a manual process. It needs a craftsman's skill to apply pressure
to spinning metal. On the other hand, hydroforming automatically
applies hydraulic pressure to non-spinning metal, seamlessly molding
tight tolerance products of any shape up to 10 inches deep.
As in metalspinning,
hydroforming also uses a mandrel with a metal blank over it. But
unlike spinning, the mandrel is forced into a diaphragm of hydraulically
pressurized rubber. The pressurized diaphragm encapsulates the mandrel
and workpiece, making the metal blank conform top the shape of the
mandrel.
Whereas spinning
can thin the material in certain areas, hydroforming does not thin
the material - thickness is uniform. Deep fry oil filters, soup
kettles warming pots, and stainless steel floats are just a few
of the applications for hydroforming.
The Combination
There is
a unique combination of hydroforming and spinning that can often
be a cost effective solution for some design challenges. The combines
process can help maximize material usage, material integrity, and
efficiency. Metalspun Products is the only spinning shop in Wisconsin
that performs this process combination.
In this technique,
the main body of a part is hydroformed into a cylinder, dome, or
hemisphere. Then the spinning process is used to produce flanges,
or reverse flanges, and to achieve the final shape.
A variation
of the combination process involves hydroforming a preform shape
and them finish-spinning the part to its exact shape. This method
is commonly used when forming stainless steel because it saves on
multiple breakdown and annealing costs.
Hydroforming,
either alone or in combination with spinning, can maintain material
thickness within the 0.005 inch tolerance range. One customer of
Metalspun Products, which previously used only spinning to form
parts, thought the company was using a heavier gauge material than
the specifications required. The finished parts were much heavier
and more durable than those of the previous spinning vendor.
But it wasn't
heavier gauge. Metalspun hydroformed the body of the part and then
spun the flange, producing noticeably less thin-out of the material.
Bowling Ball Spin
Metalspun was
recently called upon to devise a more rounded approach to bowling
ball molds. By using a combination of hydroforming and spinning,
the company was able to make a 14 gauge, cold rolled steel mold
for 8.8 inch diameter bowling balls. The mold produced uniform spherical
shapes, close tolerances, and significant cost savings for the bowling
ball manufacturer. The main body of the mold was hydroformed in
halves. Then the two flanges were spun. The final mold looked as
if it had been machined. The spherical part was excellent, the tolerance
was tighter than before, and the entire part was precise and accurate.
Because the
mold was so smooth and uniform, the bowling ball manufacturer had
very little secondary finishing and polishing to do, which was a
welcome saving for them.
Before approaching
Metalspun, the manufacturer used molds that were spun by others.
But they encountered problems with inconsistent sizes, balls that
were out of round, and excessive machining to finish. Today, they
are bringing repeat business to Metalspun.
Float Halves
In another example,
a stainless steel float for pressure tanks recently challenged Metalspun's
creative process. Spinning, as well as stamping, had failed to produce
a float that would withstand 600 psi for the 10 minutes required
to pass quality standards.
Several companies
had tried, but were unable to hold the required material thickness.
And the manufacturer was reluctant to invest in more tooling that
would not produce acceptable results. Metalspun rose to the challenge,
agreeing to front the cost of the initial tooling. If the samples
passed muster, the customer would pay for the tooling, and the project
would continue.
Instead of using
the 18 gauge stainless the customer had specified, Metalspun was
able to use the thinner 19 gauge. When the two float halves were
hydroformed, they didn't thin out more than two thousandths all
the way through the part. Then, when the float halves were put together,
a step was spun on them to increase strength.
When the float
samples were tested, they surpassed the high pressure test. Being
able to use a thinner material without losing material thickness
added to the savings on this project.
Metalspun was
paid for the tooling, and another customer was satisfied.
New Equipment
Modern Technology
and value added services have enhanced the art of metalspinning
at Metalspun.
Metalspun recently
established a new manufacturing cell consisting of two advanced
spinning lathes, including one heavy duty model. Their fast, accurate
'playback' programming dramatically enhances productivity. It also
makes lathes very cost effective for prototyping and one-of-a-kind
work.
The two-lathe
manufacturing cell will be used primarily to spin the company's
usual array of custom parts, including lead parts for x-ray machines,
aluminum light reflectors, stainless steel bowls, and a wide variety
of other exotic metal components.
These machines
can produce finishes so smooth, there are virtually no spinning
lines. The lathes are three times more efficient than hand spinning,
and can spin materials ranging from light gauge aluminum to 1/4
inch mild steel and 1/8 inch stainless steel. They provide an entirely
new dimension in quality, consistency, and productivity.
This new equipment
has led to a dramatic increase in both efficiency and productivity
with thicker gauge materials. Hand spinning requires great physical
strength on the part of the spinner, and is necessarily slower.
Hand spinning cold formed metals up to 72 inches in diameter requires
the craftsman to literally use his body weight to help form the
piece being spun. Workers must be trained in the highly skilled
and exacting art of hand spinning.
The new CNC
lathes will also be used to fabricated some tooling. The CNC lathes
are not only spinning centers, they are also full machining centers
that can spin and machine in one operation, giving Metalspun a unique
advantage in production capacity.
Metalspun Products
Company, Inc. provides metal forming and fabricating services to
a wide range of customers in the lighting, automotive, food equipment,
dairy equipment, medical equipment, sanitation, and metal fabrication
industries.
Supplementary
services include hydroforming, stamping, welding, trimming, polishing,
assembling, shearing, and inspecting.
Metalspun Products
can spin aluminum, steel, stainless steel, copper, brass, Inconel,
incoloy titanium, lead, and other exotic metals. Sink bowls, filters,
and filter covers are often spun from stainless. Other finished
products are made in a variety of shapes and sizes, including flanges,
rolled rims, cups, cones, ball joints, venturis, diffusers, reflectors,
and hemispheres.
The company
is particularly proud of the four-foot light reflector covers, shaped
like chocolate kisses, Metalspun manufactured for the city of Hershey,
Pennsylvania. Over 30 years later, these remarkable aluminum street
light components are still in use.
Efficiencies,
accuracy, and overall productivity continue to improve at Metalspun
through computer aided processes, such as coordinate measuring,
and programmable automatic controls for both hydraulic and CNC spinning
operations. As printed in
Job Shop Technology
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