Method of forming relatively hard materials

A method of forming relatively hard materials is disclosed. The method includes providing tooling for performing the forming operation on a strip (10) of relatively hard material. The tooling includes a forming tool (22) and a mating die (24) coupled to a high speed stamping and forming machine (70). The tooling and machine are arranged so that the forming operation is performed within a time period that is less than the stress relaxation time constant for the material being formed.

The present invention is related to the forming of relatively hard 
materials in a stamping and forming machine and more particularly to the 
forming of such materials without adverse effects such as fracturing at or 
near the forming site. 
BACKGROUND OF THE INVENTION 
In the forming of certain relatively hard materials using procedures and 
apparatus that are current in the industry, the deformation of the 
material caused by the forming operation must be above some minimum value 
or fracturing of the material at or near the deformation will occur. For 
example, in the case of bending, either the radius or the degree of bend 
must be above some minimum value. It is commonly believed that the 
material work hardens as the forming takes place and then fractures as 
bending continues and the elastic limit of the material is exceeded at the 
work hardened area. Heat treatment procedures have been developed for some 
materials, such as hard aluminum alloy used in the aircraft industry that, 
coupled with the forming operation, allow limited forming without 
fracturing. However, these procedures are cumbersome, expensive to 
implement, and limited to a few relatively hard materials. Certain 
materials, however, cannot be meaningfully formed at conventional stamping 
and forming speeds and there are no heat treatment procedures available 
that will enable these materials to be easily formed. An example of such a 
material is Paliney 7, a high strength palladium gold alloy, in its full 
hard condition of about 195,000 pounds per square inch ultimate tensile 
strength, manufactured by J. M. Ney Company of Hartford, Conn. The forming 
of this material at normal stamping and forming speeds is limited to a 
certain minimum radius, however, as will be explained below, forming of 
this material to a much smaller radius is possible utilizing the method 
taught by the present disclosure. It is known that certain explosives can 
be utilized to successfully form some relatively hard materials. For 
example, Lead Azide, which has a shock wave velocity of over 20,000 feet 
per second has been used to bend and even weld materials that would 
generally fracture when bending and forming is attempted using 
conventional processes and equipment. This procedure is generally used 
with relatively large components such as ends for large tanks, autoclaves, 
boilers and similar structures. However, the use of explosives to form 
small parts such as electrical contacts for electrical connectors is 
unknown and deemed impractical. 
What is needed is a method of easily forming these relatively hard 
materials in the manufacture of relatively small parts such as electrical 
contacts without resorting to complex heat treatment procedures or methods 
that employ dangerous explosives. Manually bending a piece of wire back 
and forth to break it causes a substantial temperature rise in the area of 
the bend. This local temperature rise is proportional to the speed of 
bending. Forming these materials at a high speed is perceived to generate 
sufficiently high temperatures in the forming area to make it behave as if 
annealed, and further, if the forming is accomplished in a period of time 
which is shorter than the stress relaxation constant of that material, the 
forming limit of the material is substantially improved. 
SUMMARY OF THE INVENTION 
A method is disclosed for performing a forming operation on a strip of 
relatively hard material. The method includes the following steps. Tooling 
is provided having a first tool and a second tool matable with the first 
tool for performing the forming operation. A stamping and forming machine 
is provided having the first and second tools coupled thereto. The first 
tool is arranged to undergo movement toward the second tool into mated 
engagement therewith and movement away from the second tool out of mated 
engagement. A strip of relatively hard material is placed between the 
first and second tools. The stamping and forming machine is then operated 
so that the movement causes the first tool to move toward the second tool 
to a first position in engagement with the strip of relatively hard 
material. And then further to move the first tool to a second position in 
mated engagement with the second tool thereby completing the forming 
operation. Wherein the first tool moves from the first position to the 
second position at a rate sufficiently fast so that the forming operation 
is completed without cracking the strip of relatively hard material.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
When bending a metal member, such as a wire, heat is generated at the site 
of the bend. It has been discovered that if the bend is performed at very 
high speed, fracturing that would normally occur does not occur. It is 
believed that during bending a sufficiently high temperature is developed 
at the site of deformation that the crystal planes are allowed to slip as 
though the material were fully annealed. While the effect of strain rate, 
that is speed of bending, on the ability of the material to withstand 
large deformation is not well understood, it was found that if the bend is 
performed in a sufficiently short time, work hardening does not have 
sufficient time to occur. Therefore, there is no fracturing of the 
material as a result of the bending operation. For this to occur the time 
period of the bending operation must be less than the stress relaxation 
time constant for the material. 
Current stamping and forming machines and practices do not provide the 
speeds necessary for the successful forming of these relatively hard 
materials. However, an apparatus has been constructed and tested that 
demonstrates that such forming is easily achievable. This apparatus and 
the method of the present invention will now be described. 
There is shown in FIG. 1 a cross section of a strip 10 of relatively hard 
material, which in the present example is Paliney 7 in its full hard 
condition of about 195,000 pounds per square inch ultimate tensile 
strength, as manufactured by the J. M. Ney Company. The strip 10 is 0.0018 
inch thick and includes a starting hole 12 having a diameter of 0.005 inch 
that extends through the strip. The strip is to be formed to the shape 
shown in FIG. 2 by deforming the material around the hole 12 downwardly to 
form an annular flange 14 having an inside diameter of 0.010 inch and a 
length 16 of about 0.006 inch. An audio speaker 20, as shown in FIG. 3, is 
used as a transducer to drive a forming tool 22 into mating engagement 
with a die 24 to form the flange 14. A signal generator 26 is 
interconnected to a voice coil 28 of the speaker by means of a circuit 30. 
The voice coil 28 is attached to and drives a movable cone 32 to which the 
forming tool 22 is attached by any suitable means, such as adhesive. The 
voice coil 28 is magnetically coupled to a magnetic core 36 in the usual 
manner so that movement of the cone can be very precisely controlled by 
controlling the rise time, length, and amplitude of a signal 34 that is 
transmitted to the voice coil by the signal generator 26 via the circuit 
30. As shown in FIG. 4, the forming tool 22 has a somewhat spherical end 
40 and a diameter 42 that is substantially equal to the diameter 12, 0.010 
inch in the present example. The die 24 includes an upwardly facing die 
face 44 having a die opening 46 therethrough that conforms to the shape of 
the forming tool 22 but is sized slightly larger to allow for the desired 
wall thickness of the flange 14. The upper edge of the die opening 46 
includes a radius 48, that is 0.0001 to 0.0005 inch in the present 
example, as is the practice in the industry to help prevent tearing during 
the forming process. In operation, the strip 10 is placed on the die 
surface 44 with the starter hole 12 in alignment with the die opening and 
the forming tool 22, as shown in FIG. 4. The signal generator 26 is then 
operated to transmit a single pulse 34 having an amplitude sufficient to 
drive the cone 32 and attached forming tool 22 so that the tip 40 moves 
into the die opening 46 to the position shown in FIG. 5. The pulse 34 is 
shaped to provide a coil travel time of 0.15 millisecond so that after the 
tip 40 moves into engagement with the strip, it will continue to move to 
the position shown in FIG. 5 within that time period. That is, the entire 
forming operation from the time that the tip 40 first engages the strip 10 
to the time that the tip is fully mated with the die 24 is about 0.15 
millisecond. 
A similar forming tool and die were arranged in a conventional stamping and 
forming machine that included a ram having a stroke of 1.5 inches and 
operated at 1200 strokes per minute. A strip of full hard Paliney 7, 
similar to the strip 10, was placed between the forming tool and die and 
the machine actuated to form a flange similar to the flange 14. The 
forming tool, after moving into engagement with the strip, required 0.39 
millisecond to continue movement to its fully mated positions with the 
die. This relatively long time period to perform the forming operation was 
greater than the stress relaxation time constant for the material and the 
strip fractured at the forming site as expected. 
While the speaker 20 is suitable for applying the teachings of the present 
invention to very small parts, a high speed stamping and forming machine 
having the capability of performing the forming operation in the desired 
time period of 0.15 millisecond would be more suitable for larger parts 
such as electrical contacts for electrical connectors. Such a high speed 
machine 70, shown in FIG. 6, is disclosed in copending patent application 
Ser. No. 08/496,376, filed Jun. 29, 1995 by the present inventor and 
assigned to the present assignee, having the title "A MACHINE FOR 
PERFORMING HIGH SPEED STAMPING AND FORMING OPERATIONS". The high speed 
machine 70, includes a ram 72 that moves toward and away from a bolster 
plate 74 at a rate of 6000 strokes per minute. The length of the stroke is 
0.4 inch. An electric motor 76 is coupled to a drive shaft 78 having an 
eccentric 80 which drives the ram by means of a crank 82. The drive shaft 
and crank are journaled in hydrostatic bearings and the ram in a linear 
hydrostatic bearing, including unique fluid conduits, all of which are 
specially designed to allow the machine to operate at such high speed. An 
upper tooling mount 84 is attached to and carried by the ram 72. The 
forming tool 22 is secured to this tooling mount 84 and the mating die 24 
is secured to the bolster plate 74 in the usual manner. 
These two examples utilizing the stamping and forming machine 70 having a 
ram stroke of 0.4 inch and operating at 6000 strokes per minute and the 
conventional stamping and forming machine having a ram stroke of 1.5 
inches and operating at 1200 strokes per minute are illustrated in two 
graphs having curves 90 and 92 shown in FIGS. 7 and 8, respectively. As 
shown in FIG. 7, the curve 90 depicts the movement of the ram 72 of the 
machine 70 through its 0.4 inch stroke, along the Y-axis, and the time 
from 0.00 second to 0.01 second for completing a single stroke, along the 
X-axis. The point at which the tip 40 of the forming tool 22 first engages 
the strip 10 is indicated as a line 94 at the 0.0018 point on the Y-axis. 
The curve 90 intercepts this line at the 4.85 millisecond point along the 
X-axis as indicated at 96 in FIG. 7. The curve 90 also intercepts the 
X-axis at the 5.00 millisecond point along the X-axis as indicated at 98. 
All of the forming takes place between these two points, over a ram 
displacement of 0.0018 inch and a time period of 0.15 millisecond. The 
curve 92 shown in FIG. 8, on the other hand, depicts the movement of the 
ram of a conventional stamping and forming machine through its 1.5 inch 
stroke, along the Y-axis, and the time from 0.00 second to 0.05 second for 
completing a single stroke, along the X-axis. The point at which the tip 
40 of the forming tool 22 first engages the strip 10 is indicated as a 
line 102 at the 0.0018 point on the Y-axis. The curve 92 intercepts this 
line 102 at the 24.61 millisecond point along the X-axis as indicated at 
104 in FIG. 8. The curve 92 also intercepts the X-axis at the 25.00 
millisecond point along the X-axis as indicated at 106. All of the forming 
takes place between these two points, over a ram displacement of 0.0018 
inch and a time period of 0.89 millisecond. As indicated above, this time 
period is greater than the stress relaxation time constant for the 
material of the strip 10 and, therefore, will result in fractures at of 
near the site of forming. 
While the present invention may be practiced by means of the speaker 20, 
shown in FIG. 3 and the high speed stamping and forming machine 70, shown 
in FIG. 6, other suitable apparatus may be utilized to perform the forming 
operation within the critical time period of between about 0.39 
millisecond and 0.15 millisecond or less, depending upon the specific 
material being formed and its stress relaxation time constant. Such other 
suitable apparatus may include tools operating in a conventional press at 
conventional speeds but having a speed enhancing mechanism that provides 
the necessary tool closure rate to assure that the forming occurs within 
the required time period. Further, while the forming operation exemplified 
herein is a drawing operation that displaces the material, it will be 
understood that the teachings of the present invention may be 
advantageously practiced with other stamping and forming operations that 
displace the material such as bending, blanking, coining, twisting, 
upsetting, drawing, and other operations where the material is cut or 
deformed. 
An important advantage of the present invention is that many different 
relatively hard materials that heretofore were not able to be easily 
formed can now be considered for use. This allows the use of many alloys, 
such as beryllium nickel, manufactured by the NGK Metals Company of 
Reading, Pa., and Paliney 7 that are attractive electrical contact 
materials that would otherwise not be usable if forming were attempted at 
conventional forming speeds.