Note: Descriptions are shown in the official language in which they were submitted.
4
CA 02402945 2002-09-27
METHOD AND DEVICE FOR PRODUCING COMPONENTS FROM A DEEP
DRAWABLE BLANK
The present invention relates to a method for producing
components from blank made of a reshapable material,
particularly steel, in which the blank is supported
against a shaping tool by a fluid cushion during the
deforming. In addition, the present invention relates to
a device which is particularly suitable for performing
such a method. These types of devices typically have a
receptacle into which a fluid, for example water or a
comparable liquid, is poured as an action medium. A blank
is held over the opening of the receptacle by suitable
mechanisms, so that, for example, it may be deformed by a
stamp which is positioned in the opening and movable into
the receptacle. In this case, during the deforming, the
fluid contained in the receptacle supports the blank as a
cushion against the pressure -exercised by the stamp, so
that the blank takes on the shape predetermined by the
stamp as the stamp progresses.
In an alternative method of the type initially described,
the blank is pressed against a stationary tool, which is
positioned in or over the receptacle opening, by
elevating the pressure exercised by the fluid contained
in the receptacle, through which the shape of the
workpiece to be produced is determined. Combinations of
the methods described are also in use.
Methods and devices of the type described above are
suitable for the production of complex components having
improved properties. In this case, the advantage of
deforming performed with the aid of a cushion formed by a
flowing action medium is that, unlike in typical deep
drawing, in which a stamp deforms the blank in a matrix
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forming the countermold, the flowing of the material into
the final shape is made easier. However, it is
problematic that very high pressures are necessary for
exact implementation of the desired component shape.
Therefore, calibration of the preshaped component occurs
at the end of the reshaping procedure in the conventional
method, during which the shaping precision is elevated by
a strong increase in pressure in the fluid cushion.
The production of "additional form elements", which have
small radii, has been shown to be particularly
problematic in practice. These types of additional form
elements may only be shaped into the component after the
blank is deformed into the main shape of the component.
The high calibration pressures necessary for shaping the
additional form elements lead to large forces,
particularly in large area components, which are
necessary for holding the blank in the respective device
during the deforming procedure. Both the outlay for
apparatus necessary for this purpose and the technical
outlay which must be made for producing the high
calibration pressures and for sealing the overall system
which has these high pressures applied to it leads to
high costs for the provision and operation of devices of
the type discussed.
Reducing this outlay by mounting fixed counter mold
pieces in the receptacle of the respective device,
corresponding to the conventional deep drawing
deformation of blanks, has been attempted. The blanks are
pressed against these static, fixed counter mold pieces
in the course of the movement performed by the tool, so
that the implementation of the respective additional form
elements is forced. This method has the disadvantage that
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the rigid counter mold elements in the receptacle engage
in the reshaping at the time in which the main material
flow has not yet ended and therefore uncontrolled
material flow may be caused. This may in turn lead to
overshoot edges, local damage to the surface, and sink
marks, which reduce the quality of the components
produced.
The object of the present invention is to provide a
method and a device of the type described above, using
which exactly shaped components may be produced cost
effectively without the danger of reduction in quality.
This object is achieved, on one hand, by a method for
producing components in which a blank made of a
reshapable material, particularly steel, is supported by
a fluid cushion against a shaping tool during the
deforming and the following steps are completed:
- deforming of the blank into an intermediate shape
using the tool and
- subsequent localized.deformi.ng of the blank, which
is deformed into the intermediate shape, using a
counter mold piece, which is moved against the blank
against the action direction of the tool.
According to the present invention, the reshaping of the
blank is divided into at least two steps. In the first
step, the main part of the deforming occurs in that the
blank is reshaped using the tool enough that all basic
elements of the component shape are essentially
implemented. When this main deforming is finished, the
additional form elements are produced.
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In contrast to the related art, an actively movable and
controllable counter mold piece is moved toward the blank
for this purpose. Its dimensions are implemented in such
a way that at each case a deformation of the blank occurs
which is restricted to the region of the additional form
element. Since the counter mold piece actively works
against the blank, it acts like a shaping tool itself. In
contrast, the tool causing the main deforming forms the
"matrix", on which the blank is shaped, during the
implementation of the respective additional form element.
The advantage of the method according to the present
invention, which has at least two parts, is that the main
deforming is performed only against the pressure of the
fluid cushion, uninfluenced by a fixed counter element.
In this case, both the material flow and the shaping can
be laid out in such a way that optimum conditions for the
final shaping of the respective additional form elements
are provided.
Therefore, additional form elements having complex shapes
may be produced exactly without the extreme elevation in
pressure still required in the related art being
necessary for this purpose. Damage to the blank or flaws
of the material distribution which interfere with the
visual impression are very reliably avoided. As a
consequence, components which meet the highest
requirements may be produced from blanks in the way
according to the present invention with reduced outlay
for apparatus.
A embodiment of the present invention which allows a
particularly expedient performance of the method
according to the present invention is characterized in
that the tool is a stamp which is adjustable in its
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position. Using a movable stamp tool of this type, which
is positionable on the blank, the shape of the workpiece
to be produced may be generated using high shaping
precision, with optimum utilization of the supporting
effect of the fluid cushion.
It is particularly advantageous if the localized
deforming is first performed when the pressure in the
fluid cushion has reached a minimum value. This minimum
value of the pressure may be reached automatically in the
course of the main deforming of the blank. If this is not
the case, then a pressure state more favorable for
implementing the respective additional form element may
be produced by a supplemental increase in pressure in the
fluid cushion. Depending on the course and complexity of
the shaping of the additional form element, it may
additionally be expedient, using the counter mold
element, to vary the pressure of the fluid cushion during
the deforming in relation to the previously existing
pressure. The minimum pressure existing in the fluid
cushion should preferably correspond in this case to the
pressure at which shaping of the additional form element
caused by the pressure of the fluid cushion begins.
The generation of a specific pressure state by the
counter mold piece at the beginning and during the
production of the additional form elements is used for
further improvement of the work result. If the blank is
supported against the shaping tool using a sufficiently
high pressure, the danger of the occurrence of
uncontrolled material flows during the shaping of the
respective additional form element is reduced. Surface
damage of the component may be reliably prevented in this
way.
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The shaping precision of the component produced according
to the present invention may be elevated further if the
pressure of the fluid cushion is elevated after reaching
the final shape. This final elevation in pressure is
used, like the calibration procedure typical in the
conventional method, for the purpose of correcting
changes of the main shape of the component generated by
the shaping tool which may occur as a consequence of the
production of the additional form element.
On~the other hand, the object described above is achieved
in regard to a device for producing components from a
blank made of a reshapable material, particularly steel,
which is equipped with a receptacle filled with a fluid,
with a device for holding the blank over an opening of
the receptacle, and with a shaping tool, which is
positionable over an opening of the receptacle, in that
at least one counter mold piece, which is movable against
the blank against the action direction of the tool, is
positioned in the receptacle. Such a device equipped with
an actively adjustable counter mold piece is particularly
suitable for performing the method according to the
present invention because the counter mold piece is
controllable in such a way that it only engages in the
deforming procedure when the main deforming of the blank
by the tool is finished. In this way, an extreme
elevation in pressure, as is still necessary in the
related art for implementing complex additional form
elements, is no longer necessary during operation of a
device implemented according to the present invention.
Therefore, these types of devices may be produced and
ogerated at lower costs.
~
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A particularly high-capacity device of the type according
to the present invention may be implemented if the tool
is a stamp which is adjustable in its position.
A device according to the present invention is preferably
equipped with a control unit which outputs a signal for
adjusting the counter element against the blank as soon
as a specific deformation of the blank is achieved. This
embodiment of the present invention is particularly
suitable for automated production of deep drawn
components. In principle, it is conceivable in this
connection that the appropriate signal for adjusting the
counter piece is output, for example, as a function of
the adjustment path of the shaping tool which has been
covered. However, the control unit preferably outputs the
signal for adjustment when the pressure of the fluid
contained in the receptacle has exceeded a specific value
which is favorable for the shaping of the additional form
element.
In order to be able to adjust the pressure existing in
the receptacle purposefully, a controllable valve is to
be provided, using which the pressure in the receptacle
is changeable. In addition, it is favorable if, in a
device implemented according to the present invention, a
pressure generation device is present, using which the
pressure of the pressure [sic] contained in the
receptacle may be elevated. A pressure state favorable
for implementing the additional form element may be
achieved purposefully using such a pressure generation
device.
In the following, the invention is described in more
detail with reference to a drawing which illustrates an
exemplary embodiment. In schematic illustration:
CA 02402945 2002-09-27
Fig. 1 shows a device for producing a component from a
blank in a first operating position in a
longitudinal section;
Fig. 2 shows the device shown in Fig. 1 in a second
operating position;
Fig. 3 shows the device shown in Fig. 1 in a third
operating position;
Fig. 4 shows the device shown in Fig. 1 in a fourth
operating position.
The device shown in the figures is used for producing,
for example, a car body component from a blank 1, which
is cut to size from thin sheet metal. For this purpose,
the device includes a receptacle 2, which is implemented
like a box and is open on top, a mechanism 4 for holding
blank 1, which is implemented as a blank holder ring and
may be placed on the upper edge 3 of receptacle 2, which
surrounds the receptacle opening, and a stamp 5, forming
a shaping tool, which may be introduced using an
adjustment mechanism, not shown, in adjustment direction
R into the opening of receptacle 2 from a rest position
(Fig. 1) located above the receptacle.
In addition, there is a counter mold piece 6 in
receptacle 2 carried by a piston 8, which is
hydraulically adjustable in an adjustment direction S,
directed against the adjustment direction R of the stamp,
using an adjustment mechanism 7. A pressure generation
device 9 is provided for filling receptacle 2 with a
liquid F, for example water.
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Stamp 5 has a shape on its side facing blank 1 which
corresponds to the shape of the component to be produced
from the blank. In this case, an additional form element
N is implemented in a region A, at which two wall
elements of the component to be produced, which run into
one another nearly perpendicularly, merge into one
another in a small radius. Counter mold piece 6, which is
provided for producing this additional form element N and
is positioned aligned with additional form element N in
the vertical direction, has a shape corresponding to the
counterpart of the shape of additional form element N on
its side assigned to blank 1.
In the operating position illustrated in Fig. l, stamp 5
and mechanism 4 are in their raised rest position, so
that blank 1 may be laid unobstructed on edge 3 of
receptacle 2. Counter piece 6 is simultaneously located
in its starting position, directly neighboring the
receptacle floor, in which the distance between blank 1
and counter piece 6 is greater than the stroke of stamp 5
performed during the deforming of blank 1. Receptacle 2
is filled with liquid F.
After the insertion of blank 1, mechanism 4 is lowered,
so that the edge of blank 1 is held clamped over the
receptacle opening between mechanism 4 and upper edge 3
of receptacle 2. Stamp 5 is brought into a position,
starting from which the deformation of blank 1 is
performed. Counter piece 6 is in its rest position, as
before. If necessary, a pre-deforming of blank 1 is
performed in the direction of stamp 5 at this time, in
that the pressure of liquid F, which receptacle 2 is
filled with, is elevated. In this way, the change in
shape in the region of the center of the blank is
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elevated and material for the subsequent main deforming
in the region of receptacle 2 is stockpiled (Fig. 2).
Subsequently, stamp 5 is introduced into the opening of
receptacle 2 in adjustment direction R, so that blank 1
is deformed. At the same time, as a function of the steel
material of blank 1 and/or the component shape to be
produced, the holding forces exercised by mechanism 4 are
dimensioned in such a way that, starting from the edge of
blank 1, a material flow in the inside of receptacle 2 is
allowed or the edge of blank 1 is held fixed. During the
deforming of blank 1 by stamp 5, liquid F, with which
receptacle 2 is filled, forms a fluid cushion, by which
blank 1 is supported on its side facing away from stamp
5. Support pressure P in liquid F is controlled and/or
regulated according to the progress of the deformation of
blank 1 caused by stamp 5. At the end of the stroke path
of stamp 5, blank 1 has obtained an intermediate shape in
which all form elements of the component have reached
their final shape except for additional form element N.
The main deforming of blank 1 performed by stamp 5 is
thus finished (Fig. 3) .
To produce additional form element N, support pressure P
is elevated by pressure generation mechanism 9 to a
minimum value at which the shaping of additional form
element N due to support pressure P exercised by liquid F
just begins. However, further elevation in pressure does
not occur at this time. Instead, counter mold piece 6 is
now moved in adjustment direction S toward blank 1, so
that blank 1 is drawn into the shape of additional form
element N predetermined by stamp 5, which is at a
standstill at this t~.me (Fig. 4) .
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When the production of additional form element N is
finished, support pressure P is elevated again in order
to definitively calibrate the shape of blank 1 on stamp
5.
Finally, stamp 5, mechanism 4, and counter piece 6 are
moved back into their starting position illustrated in
Fig. 1, so that the finished component may be removed
from the device.
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List of reference numbers
1 blank
2 receptacle
3 edge of receptacle 2
4 mechanism for holding blank 1
stamp
6 counter mold piece
7 adjustment mechanism
8 piston
9 pressure generation mechanism
A region
F liquid
N additional form element
R adjustment direction
S adjustment direction
