Hydroforming
Fluid Forming, Rubber Diaphragm Forming, Specialized Die Forming
Specific Advantages of Hydroforming Include:
- INEXPENSIVE TOOLING
A male die (punch)
and a draw ring (blank holder) are generally the only tools required. The
rubber diaphragm in the hydroform machine acts as a universal female die.
Hydroform tools normally cost at least 50% less than conventional press
tooling.
- VERSATILITY IN FORMING COMPLEX SHAPES AND
CONTOURS
Irregularly contoured shapes are easily formed using the hydroform process because matching dies are not required.
- MINIMAL MATERIAL THINOUT
Hydroforming
flows the metal rather than stretching it. Therefore, material thinout is
minimal - usually less than 10%. Wall thickness at the open end of the part
is typically nominal or greater, (a big advantage for trimming, welding and
assembly). This often results in material savings because thinner blanks can
be used - a particularly important factor when expensive alloys or a large
number of parts are ordered.
- FEWER
OPERATIONS REQUIRED
Many parts requiring two or three operations on
conventional presses can be formed in one hydroform operation. First draw
operations frequently hydroformed with reductions of 60% to 70% - compared
to only 35% to 45% using conventional dies.
- SAVINGS IN TOOL MATERIALS
Hardened tool
steels are rarely required. Most punches and draw rings are made of meehanite (cast iron) - an inexpensive, easily machined material that
provides an exceptionally long tool life. Kirksite and cast plastics may be
used for very short runs.
- FAST TOOL CHANGES
Tools are quickly
mounted and are self-centering and self-aligning. Set-ups are quick and
simple.
- SAVINGS IN FINISHING COSTS
Matched die
methods of forming can cause scuff marks, shock and stretch lines. In the Hydroform method, the wrapping action of the flexible diaphragm virtually
eliminates these faults. Savings of up to 90% in finishing costs have been
realized.
- MATERIALS VERSATILITY
Practically all
sheet metals capable of being cold formed - carbon steel, aluminum,
stainless steel, copper, brass, precious metals, high strength alloys, and
others can be hydroformed. Thickness of materials can vary within the
limits of the machine without need for tool revisions.
- PRECISION
The hydroform method forms
parts with extremely difficult configurations while at the same time working
to precise tolerances. Unless the material being formed exhibits abnormal
springback, inside measurements can be held to +/- .005" or +/- .002"
in some instances, depending on material and shape.
- EASE OF DESIGN CHANGE
Development cost
can be a large part of total tooling cost with conventional deep draw
techniques. With hydroforming, material or metal thickness can be altered
usually without any tooling changes being necessary. Hydroforming can also
eliminate or minimize the number of multiple draw operations required with
a corresponding reduction in tryout costs.
- LOW WORK-HARDENING
Hydroforming does not
cause work-hardening of materials at the same rate as conventional drawing
operations. Consequently, annealing between draw operations is rarely
required. The need for multiple draw operations can often be eliminated too.
Palmer Associates proudly represents
Charles Schillinger Company for
hydroforming and metal spinning.
Hydroforming - Process and Equipment
Hydroforming presses use a unique fluid forming process which offers many
advantages over conventional mechanical and hydraulic presses. An elastic
die member (rubber diaphragm) acting as a seal across the bottom of a
fluid-filled forming chamber serves as the upper blankholder and female die
element - a universal die which accommodates any shape. The lower portion of
the press holds a punch attached to a hydraulic piston and a blankholder
ring surrounds the punch.
At the start of the Hydroform machine cycle, the top of the punch (which is
inverted compared to a conventional press) is normally level with the top of
the blankholder ring. The forming chamber is lowered and a hydraulic
precharge is applied.
As the punch is raised into the forming chamber, the flexible diaphragm
wraps the blank around the punch, controlling the material and forming it to
the shape of the punch. At the end of the draw all of the material is
supported on the inside either by the punch or the blank holding ring and the
top by the flexible die member.
To complete the cycle, pressure is released, the forming chamber is raised
and the punch is retracted form the drawn part.
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