U.S. patent application number 14/899852 was filed with the patent office on 2016-05-19 for method for bending the machine bed of a stamping press, and stamping press.
This patent application is currently assigned to Bruderer AG. The applicant listed for this patent is BRUDERER AG. Invention is credited to Josef Thomas Hafner.
Application Number | 20160136710 14/899852 |
Document ID | / |
Family ID | 48782803 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160136710 |
Kind Code |
A1 |
Hafner; Josef Thomas |
May 19, 2016 |
METHOD FOR BENDING THE MACHINE BED OF A STAMPING PRESS, AND
STAMPING PRESS
Abstract
A method for warping the machine bed of a punching press, which
machine bed has an aperture for carrying away punching parts and
rubbish, compensates at least partially for a bending of the
machine bed caused by the punching force during the punching
operation. Thereby, forces acting transverse to the punching
direction are introduced into the machine bed and/or forces acting
transverse to the punching force direction are produced inside the
machine bed, by means of which the machine bed warps in the
direction towards the press ram and indeed such that it warps
stronger in the area adjacent to the aperture than in the areas
adjacent to its longitudinal sides. By the method, apertured
machine beds of punching presses can, with very little expenses on
the equipment side, be spatially pre-deformed in order to
compensate at least partially bendings caused by punching
forces.
Inventors: |
Hafner; Josef Thomas;
(Rorschacherberg, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BRUDERER AG |
Frasnacht |
|
CH |
|
|
Assignee: |
Bruderer AG
Frasnacht
CH
|
Family ID: |
48782803 |
Appl. No.: |
14/899852 |
Filed: |
June 27, 2013 |
PCT Filed: |
June 27, 2013 |
PCT NO: |
PCT/CH2013/000114 |
371 Date: |
December 18, 2015 |
Current U.S.
Class: |
72/352 |
Current CPC
Class: |
B30B 15/34 20130101;
B30B 15/042 20130101; B30B 15/007 20130101; B21D 22/02
20130101 |
International
Class: |
B21D 22/02 20060101
B21D022/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2013 |
CH |
PCT/CH2013/000107 |
Claims
1. A method for warping a machine bed of a punching press to
compensate at least partially a bending caused by the punching
force during punching operation, wherein the machine bed has an
aperture for carrying away punching parts and rubbish, wherein
forces acting transverse to the punching force direction are
introduced into the machine bed or are created within the machine
bed for warping the machine bed in the direction towards the press
ram such that the machine bed is warped stronger in the area
adjacent to the aperture than in the areas adjacent to the
longitudinal sides.
2. The method according to claim 1, wherein the machine bed with
tie-rods extending in its longitudinal direction is set under
compressive stress in its lower area for warping the same in the
direction towards the press ram.
3. The method according to claim 2, wherein the tie-rods are
arranged such that they cross the machine bed in its lower
area.
4. The method according to claim 2, wherein on both sides of the
aperture of the machine bed, in particular symmetrical to both
sides of the aperture, in each case a tie-rod is arranged such that
the tie-rod in each case has a smaller distance to the aperture
than to the respective longitudinal side of the machine bed.
5. The method according to claim 1, wherein a temperature gradient
is produced within the machine bed or a supporting structure for
the lower tool parts built with the machine bed, by means of which
the machine bed warps in the direction towards the press ram.
6. The method according to claim 5, wherein the temperature
gradient is produced by heating the machine bed in the area of its
side facing the press ram.
7. The method according to claim 6, wherein the machine bed near to
the boundaries of the aperture is heated stronger than near to the
longitudinal sides.
8. The method according to claim 5, wherein the temperature
gradient is produced by cooling the machine bed in the area of its
side facing away from the press ram.
9. The method according to claim 8, wherein the machine bed is near
to the boundaries of the aperture is cooled stronger than near to
the longitudinal sides.
10. The method according to claim 5, wherein flow channels arranged
within the machine bed are flown through by a heated or cooled
gaseous or liquid medium for producing the temperature
gradient.
11. The method according to claim 10, wherein heated lubricating
oil of a lubricating oil circuit of the press is passed through the
flow channels.
12. The method according to claim 5, wherein electrical heating
elements arranged within the machine bed are charged with electric
current for producing the temperature gradient.
13. The method according to claim 5, wherein a clamping plate
arranged on the machine bed is present which is heated for warping
the machine bed in the direction towards the press ram as a
consequence of a heating of it by the clamping plate on its side
facing the ram and/or for warping the machine bed in the direction
towards the press ram as a consequence of an introduction of shear
forces produced by a thermal expansion of the clamping plate into
the side of the machine bed facing the ram.
14.-40. (canceled)
41. The method according to claim 5, wherein a clamping plate
arranged on the machine bed is present and a heating device
arranged between the machine bed and the clamping plate, which is
heated for warping the machine bed in the direction towards the
press ram as a consequence of a heating of it by the heating device
on its side facing the ram and/or for warping the machine bed in
the direction towards the press ram as a consequence of a heating
of the clamping plate by the heating device and by an introduction
of shear forces produced by a thermal expansion of the clamping
plate into the side of the machine bed facing the ram.
42. The method according to claim 1, wherein the warp of the
machine bed is adjusted depending on parameters of the punching
process, in particular depending on a calculated or measured
maximal punching force, and in particular, wherein the warp is
adjusted during the intended operation of the press.
43. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by an introduction of forces
acting transverse to the punching force direction into the machine
bed and/or by producing forces acting transverse to the punching
force direction within the machine bed, wherein the machine bed has
an aperture for carrying away punching parts and rubbish and the
means for warping the machine bed are designed such that they warp
the machine bed stronger in the area adjacent to the aperture than
in the areas adjacent to the longitudinal sides of the machine bed,
and wherein the means for warping the machine bed comprise tie-rods
extending in longitudinal direction of the machine bed, by means of
which the machine bed can be set under compressive stress in its
lower area for warping the machine bed in the direction towards the
press ram.
44. The punching press according to claim 43, wherein the tie-rods
cross the machine bed in its lower area.
45. The punching press according to claim 43, wherein on both sides
of the aperture of the machine bed in each case a tie-rod is
arranged such that in each case the tie-rod has a smaller distance
to the aperture than to the respective longitudinal side of the
machine bed.
46. The punching press according to claim 45, wherein the both
tie-rods are arranged symmetrically to both sides of the
aperture.
47. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by introducing forces acting
transverse to the punching force direction into the machine bed
and/or by producing forces acting transverse to the punching force
direction within the machine bed, wherein the machine bed has an
aperture for carrying away punching parts and rubbish and the means
for warping the machine bed are designed such that they warp the
machine bed in the area adjacent to the aperture stronger than in
the areas adjacent to the longitudinal sides of the machine bed,
wherein the means for warping the machine bed are designed for
producing a temperature gradient within the machine bed or a
supporting structure for the lower tool parts built with the
machine bed, respectively, in order to produce the forces acting
transverse to the punching force direction for warping the machine
bed in the direction towards the press ram, wherein the means for
warping the machine bed comprise flow channels arranged within the
machine bed, which can be flown through by a heated or cooled
gaseous or liquid medium during the intended operation of the press
for producing the temperature gradient, and wherein the press
comprises a lubricating oil circuit and the means for warping the
machine bed comprise arrangements, by means of which heated
lubricating oil of the lubricating oil circuit can be passed
through the flow channels during the intended operation of the
press.
48. The punching press according to claim 47, wherein the means for
warping the machine bed are designed for heating the machine bed in
the area of its side facing the press ram.
49. The punching press according to claim 48, wherein the means for
warping the machine bed are designed to heat the machine bed in the
area of its side facing the press ram stronger near to the
boundaries of the aperture than near to its longitudinal sides.
50. The punching press according to claim 47, wherein the means for
warping the machine bed are designed to cool the machine bed in the
area of its side facing away from the press ram.
51. The punching press according to claim 50, wherein the means for
warping the machine bed are designed to cool the machine bed in the
area of its side facing away from the press ram stronger near to
the boundaries of the aperture than near to its longitudinal
sides.
52. The punching press according to claim 47, wherein the means for
warping the machine bed comprise electrical heating elements
arranged within the machine bed, which can be charged by electric
current during the intended operation of the press for producing
the temperature gradient.
53. The punching press according to claim 47, wherein on both sides
of the aperture of the machine bed in each case one or more flow
channels and/or electrical heating elements are arranged within the
machine bed such that, per side, the sum of the distances of the
flow channels and/or the heating elements to the aperture is
smaller than the sum of the distances of the flow channels and/or
heating elements to the respective longitudinal sides of the
machine bed.
54. The punching press according to claim 53, wherein the flow
channels and/or the heating elements are arranged symmetrically to
both sides of the aperture.
55. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by introducing forces acting
transverse to the punching force direction into the machine bed
and/or by producing forces acting transverse to the punching force
direction within the machine bed, wherein the machine bed has an
aperture for carrying away punching parts and rubbish and the means
for warping the machine bed are designed such that they warp the
machine bed in the area adjacent to the aperture stronger than in
the areas adjacent to the longitudinal sides of the machine bed,
wherein the means for warping the machine bed are designed for the
production of a temperature gradient within the machine bed or a
supporting structure for the lower tool parts built with the
machine bed, respectively, in order to produce the forces acting
transverse to the punching force direction for warping the machine
bed in the direction towards the press ram, and wherein a clamping
plate arranged on the machine bed is present which can be heated by
the means for warping the machine bed during the intended operation
of the press for producing the temperature gradient by heating the
machine bed on its side facing the ram by the clamping plate.
56. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by introducing forces acting
transverse to the punching force direction into the machine bed
and/or by producing forces acting transverse to the punching force
direction within the machine bed, wherein the machine bed has an
aperture for carrying away punching parts and rubbish and the means
for warping the machine bed are designed such that they warp the
machine bed in the area adjacent to the aperture stronger than in
the areas adjacent to the longitudinal sides of the machine bed,
wherein the means for warping the machine bed are designed for the
production of a temperature gradient within the machine bed or a
supporting structure for the lower tool parts built with the
machine bed, respectively, in order to produce the forces acting
transverse to the punching force direction for warping the machine
bed in the direction towards the press ram, and wherein a clamping
plate arranged on the machine bed is present which can be heated by
the means for warping the machine bed during the intended operation
of the press and which is connected with the machine bed such that
it can transfer shear forces to the machine bed for warping the
machine bed in the direction towards the press ram as a consequence
of an introduction of shear forces produced by a thermal expansion
of the clamping plate into the side of the machine bed facing the
press ram.
57. The punching press according to claim 56, wherein a thermal
insulation layer is present between the clamping plate and the
machine bed for reducing a heat transfer from the clamping plate to
the machine bed.
58. The punching press according to claim 57, wherein the thermal
insulation layer is present in the areas, which adjoin the
longitudinal sides of the clamping plate or of the machine bed,
respectively, between the clamping plate and the machine bed and in
the areas, which adjoin the aperture, a layer between the clamping
plate and the machine bed is present which has an essentially
better thermal conductivity for promoting a heat transfer from the
clamping plate to the machine bed in these areas.
59. The punching press according to claim 55, wherein the clamping
plate can be heated by the means for warping the machine bed during
the intended operation of the press such that it is warmer in the
areas which adjoin the aperture than in the areas which adjoin the
longitudinal sides.
60. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by introducing forces acting
transverse to the punching force direction into the machine bed
and/or by producing forces acting transverse to the punching force
direction within the machine bed, wherein the machine bed has an
aperture for carrying away punching parts and rubbish and the means
are designed for warping the machine bed such that they warp the
machine bed in the area adjacent to the aperture stronger than in
the areas adjacent to the longitudinal sides of the machine bed,
wherein the means for warping the machine bed are designed for the
production of a temperature gradient within the machine bed or a
supporting structure for the lower tool parts built with the
machine bed, respectively, in order to produce the forces acting
transverse to the punching force direction for warping the machine
bed in the direction towards the press ram, and wherein a clamping
plate arranged on the machine bed is present and wherein the means
for warping the machine bed comprise a heating device arranged
between the machine bed and the clamping plate, which can be
operated during the intended operation of the press for warping the
machine bed as a consequence of a heating of it on its side facing
the ram.
61. A punching press for performing the method according to claim
1, with a machine bed and with a press ram working against the
machine bed, wherein means are present for warping the machine bed
in the direction towards the press ram by introducing forces acting
transverse to the punching force direction into the machine bed
and/or by producing forces acting transverse to the punching force
direction within the machine bed, wherein the machine bed has an
aperture for carrying away punching parts and rubbish and the means
for warping the machine bed are designed such that they warp the
machine bed in the area adjacent to the aperture stronger than in
the areas adjacent to the longitudinal sides of the machine bed,
wherein the means for warping the machine bed are designed for the
production of a temperature gradient within the machine bed or a
supporting structure for the lower tool parts built with the
machine bed, respectively, in order to produce the forces acting
transverse to the punching force direction for warping the machine
bed in the direction towards the press ram, and wherein a clamping
plate arranged on the machine bed is present, which is connected
with the machine bed such that it can transfer shear forces to the
machine bed, and wherein the means for warping the machine bed
comprise a heating device arranged between the machine bed and the
clamping plate, which can be operated during the intended operation
of the press for warping the machine bed in the direction towards
the press ram as a consequence of an introduction of shear forces
produced by a thermal expansion of the clamping plate into the side
of the machine bed facing the ram.
62. The punching press according to claim 60, wherein the heating
device arranged between the machine bed and the clamping plate is
designed such that with it the areas of the machine bed or of the
clamping plate, respectively, which adjoin the aperture can be
heated stronger than the areas of the machine bed or of the
clamping plate, respectively, which adjoin their longitudinal
sides.
63. The punching press according to claim 43, wherein the means for
warping the machine bed are built adjustable, in particular during
the intended operation of the press, for enabling a specific
adjustment of the warp of the machine bed.
64. The punching press according to claim 43, wherein the punching
press comprises a press control, by means of which the warp of the
machine bed, in particular automatically, is adjustable depending
on parameters of the punching process, in particular depending on a
calculated or measured maximal punching force, and in particular is
adjustable during the intended operation of the press.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] Applicant hereby claims priority benefits under U.S.C.
.sctn.119 from International Patent Application Serial No.
PCT/CH2013/000114 filed on Jun. 27, 2013, and from International
Patent Application Serial No. PCT/CH2013/000107 filed on Jun. 19,
2013, the contents of which are incorporated by reference
herein.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to a method for warping the
machine bed and/or the press ram of a punching press to compensate
at least partially a bending caused by the punching force during
punching operation and a punching press, in particular to perform
the method, according the preambles of the independent claims.
BACKGROUND OF THE INVENTION
[0003] For the industrial manufacturing of punching parts from
metal strips, fast running automatic punching machines are used
nowadays, at which an upper tool part with punches is moved over a
certain stroke towards a lower tool part with dies and makes cuts
and shapings at the metal strip by doing so. The today's, so called
progressive dies, which mostly comprise a larger quantity of
modules, which handle different tasks like cutting, bending, metal
forming and stamping, call for more and more longer installation
spaces.
[0004] Correspondingly the length of the tool installation space of
punching machines has practically been doubled in the last three
decades at unchanged tonnage, which leads to a corresponding growth
of the moved and unmoved masses due to the longer components and at
the same time to problems with the stiffness of the press
structure, because the stiffness typically decreasing due to the
increase of the length of some critical components, in particular
of the machine bed, cannot be arbitrarily compensated by
corresponding increases of cross section due to limited available
space.
[0005] Hereby again there is the problem that it is more and more
difficult with increasing length of the tool installation space to
keep the deformations of the press structure and in particular the
bending of the machine bed under punching load, which should be as
small as possible for a high process precision and a little tool
wear within passable limits. At machine beds with an aperture for
carrying away punching parts and rubbish, as it is used in today's
automatic punching machines, there is a spatial bending of the
machine bed during the punching operation because it is punched
more or less over this aperture, so that the bending in the area of
the aperture is bigger than in the areas of the longitudinal sides
of the machine bed. In particular for the case that punching work
is performed in the rather unusual punching direction from back to
front, these bendings are a big problem.
[0006] For decreasing or compensating the bending by the process
load at machine beds or tool clamping plates without aperture, it
is known from prior art to warp the machine bed or the tool
clamping plate, respectively, against the bending direction,
preferably such that this warping is just neutralized by the
process load, or however to support the tool clamping plate
dynamically with height adjustable supporting elements on a
supporting structure possibly bending under the load, that even
under the punching load the tool clamping plate does not experience
a substantial bending.
[0007] Like that, a press is known from EP 0 653 254 A2, at which
support elements are arranged between the press bed and the tool
clamping plate, which are adjustable in height. These support
elements can be of a mechanical, electromechanical or hydraulic
nature and can be operated by a controller such that it is
counteracted the deformation of the tool clamping plate under the
working pressure of the press. It is also possible to produce with
these support elements a warp of the clamping plate to compensate
tool characteristics.
[0008] A machine table with a tool clamping plate for presses in
the sector of metal forming is known from DE 44 15 577 A1, at which
a plurality of hydraulic compensation pistons are arranged between
a base plate and a tool clamping plate. There are present range
sensors or bending sensors, respectively, and a suitable controller
to control the pressure in the compensation pistons such that it
counteracts a deformation of the tool clamping plate under the
working pressure of the press.
[0009] The systems known from EP 0 653 254 A2 and DE 44 15 577 A1
have basically the disadvantage that they are mechanically complex
and therefore their production and maintenance is elaborate and
cost-intensive and that they allow a relatively low structural
stiffness for the needed construction height due to their
construction principle with multiple punctual support of the tool
clamping plate in the punching direction on a supporting structure
lying under it. For the variants with hydraulic support
elements/compensation pistons, there is the additional disadvantage
that the supporting oil cushion has a low stiffness in the punching
direction and that the inevitable deformations of the entire
hydraulic system under the oil pressure produced by the supporting
pressure lead to a deflection of the support under the punching
load. For the variants, at which a bending of the tool clamping
plates shall be avoided by a dynamic height adjustment of
supporting elements, it is to say that, if realizable at reasonable
costs, these possibly suit for very slow metal forming processes,
but not for fast automatic punching machines for processing metal
strips by the progressive die process.
[0010] A press is known from DE 100 10 197 A1, at which the machine
bed can be warped in the direction towards the press ram by
pre-loading of tie-rods longitudinally crossing the machine bed in
the lower area to correct a bending of the press bed or to produce
a warping in the unloaded state. There is present a controller, by
which the pre-loading of the tie-rods can be controlled depending
on detected warps. This system avoids the disadvantages mentioned
before of the two first mentioned systems as far as possible.
[0011] None of the known systems solves the problem mentioned at
the beginning of the spatial bending at machine beds with an
aperture for carrying away punching parts and rubbish.
SUMMARY OF THE INVENTION
[0012] Therefore an objective is to provide a technical solution
which at punching presses with a machine bed with an aperture for
carrying away punching parts and rubbish enables an at least
partial compensation of a spatial bending of the machine bed caused
by punching forces both in longitudinal and in cross direction of
the machine bed and thereby does not show the previously mentioned
disadvantages of the prior art or avoids these at least partially,
respectively. This objective is solved by the method and the
punching press according to the independent claims.
[0013] According to these, a first aspect of the invention concerns
a method for warping the machine bed of a punching press, which
machine bed has an aperture for carrying away punching parts and
rubbish, for compensating at least partially a bending of the
machine bed caused by punching forces during punching operation.
Thereby, according to the invention forces acting transverse to the
punching force direction are introduced into the machine bed and/or
forces acting transverse to the punching force direction are
produced within the machine bed, by means of which the machine bed
warps in the direction towards the press ram, and in fact such that
it warps stronger in the area adjacent to the aperture than in the
areas adjacent to its longitudinal sides.
[0014] Apertured machine beds of punching presses can be spatially
pre-deformed by the method according to the invention with very
little expenses on the equipment side in order to at least
partially compensate bendings caused by punching forces.
[0015] In a preferred embodiment of the method, the machine bed
with tie-rods extending in its longitudinal direction is set under
compressive stress in its bottom area for warping the same in the
direction towards the press ram. This method of the production of
deformation forces has the advantage that it reachs without any
time lag and that the deformation forces or the resulting
deformations, respectively, are well controllable.
[0016] Thereby, it is preferred to arrange the tie-rods such that
they cross the machine bed in its bottom part. Hereby, there is the
advantage that practically no additional space is needed.
[0017] With advantage, a tie-rod is arranged at these embodiments
in particular symmetrically at both sides of the aperture in each
case such that the tie-rods in each case have a smaller distance to
the aperture than to the respective longitudinal side of the
machine bed. Hereby a stronger warp can be reached in the area of
the aperture than in the area of the longitudinal sides in an easy
way.
[0018] In a further preferred embodiment of the method, a
temperature gradient is specifically produced within the machine
bed or within a supporting structure for the lower tool parts of
the press tool built with the machine bed by means of which the
machine bed is warped in the direction towards the press ram as a
consequence of locally different thermal expansion or thermal
shrinkage of the machine bed, respectively, and/or different
thermal expansion or thermal shrinkage, respectively, of components
of the supporting structure for the lower tool parts built with the
machine bed. This method of production of the deformation forces
has the advantage that it can be applied without having to deviate
from existing and proven structural concepts. This is of
outstanding significance particularly in the area of fast operating
high performance automatic punching machines, because detail work
for years is often needed here to optimize the press structure with
respect to its dynamic behaviour and to its life time. Additionally
the method according to the invention can be applied with little
effort also to existing presses.
[0019] Thereby, in a preferred embodiment of the method, the
temperature gradient effecting the warp is produced by heating the
machine bed in the area of its side facing the press ram, wherein
it is further preferred that it is stronger heated near to the
boundaries of the aperture than near to the longitudinal sides of
the machine bed. The local heating is a particularly simple and
often also economical method to produce a temperature gradient, in
particular because waste heat is often available for free at
production lines.
[0020] Alternatively or additionally it is preferred to produce the
temperature gradient by cooling the machine bed in the area of its
side facing away from the press ram, wherein it is further
preferred to stronger cool it near to the boundaries of the
aperture than near to the longitudinal sides of the machine bed.
This method is particularly appropriate if these machine components
get relative warm in operation and can be cooled locally in this
way without having undershootings of dew point with condensation
water at machine parts.
[0021] The introduction of heat and/or coldness into the parts can
be performed in different ways.
[0022] For this, in a preferred embodiment of the method, flow
channels arranged within the machine bed are flowed through by a
heated or cooled, respectively, gaseous or liquid medium.
[0023] For this for example, heated lubricating oil of a
lubricating oil circuit of the press can be used which is passed
through the flow channels before cooling back. Last mentioned
method has the advantage that no additional energy is needed for
heating.
[0024] In a further preferred embodiment of the method, electrical
heating elements are arranged within the machine bed and are
charged with electric current for producing heat. At this variant,
there is the advantage that with very simple means a precise and
specifically tailored to the particular operation control of the
temperature gradient is possible.
[0025] In an even further preferred embodiment of the method, the
temperature gradient is produced in that a clamping plate is
arranged on the machine bed, which is heated.
[0026] In another preferred embodiment of the method, a clamping
plate is arranged on the machine bed and a heating device is
arranged between the machine bed and the clamping plate, which is
heated.
[0027] In this case, according to a preferred variant of these two
last mentioned embodiments, the machine bed is heated by the heated
clamping plate or by the heating device arranged between the
machine bed and the clamping plate at its side facing the ram, with
the consequence that there is a warp of the machine bed in the
direction towards the press ram.
[0028] According to another preferred variant of these two last
mentioned embodiments, the clamping plate is connected in a shear
stiff manner with the machine bed, directly or indirectly over the
heating device. At this variant, the warp of the machine bed in the
direction towards the press ram can also be done exclusively as a
consequence of an introduction of shear forces, produced by a
thermal expansion of the clamping plate, into the side of the
machine bed facing the ram, or also as a consequence of a
combination of shear forces produced by a thermal expansion of the
clamping plate into the side of the machine bed facing the ram with
a heating of the machine bed by the clamping plate or the heating
device, respectively.
[0029] In an even further preferred embodiment of the method, the
warp of the machine bed is adjusted depending on parameters of the
punching process, for example depending on a pre-calculated or
product-specific punching force, respectively, or depending on a
maximal punching force measured during operation. Further it is
preferred that the warp is adjusted during the intended operation
of the press. In this way, it can be accommodated the respective
operating situation and possible changes, for example due to
additional tool wear, particularly well.
[0030] A second aspect of the invention is related to a punching
press which is suited for performing the method according to the
first aspect of the invention. The punching press has a machine bed
and a press ram working against the machine bed. The machine bed of
the punching press has an aperture for carrying away punching parts
and rubbish. Further the punching press comprises means for warping
the machine bed in the direction towards the press ram by
introducing forces transverse to the punching force direction into
the machine bed and/or by producing forces acting transverse to the
punching force direction within the machine bed. Thereby, these
means are designed such that they warp the machine bed stronger in
the area adjacent to the aperture than in the areas adjacent to the
longitudinal sides of the machine bed.
[0031] By the invention it becomes possible to provide cost
effective, highly precise, fast running high performance punching
presses with apertured machine beds.
[0032] In a preferred embodiment of the punching press, the means
for warping the machine bed comprise tie-rods extending in the
longitudinal direction of the machine bed, by means of which the
machine bed is set under compressive stress in its bottom area for
warping the machine bed in the direction towards the press ram.
This method of production of deformation forces has the advantage
that it works without any time lag and that the deformation forces
or the resulting deformations, respectively, are well
controllable.
[0033] Thereby, it is preferred to arrange the tie-rods such that
they cross the machine bed in its bottom area. Hereby, practically
no additional space is needed.
[0034] With advantage, a tie-rod is arranged at these embodiments
in particular symmetrically at both sides of the aperture in each
case such that the tie-rods in each case have a smaller distance to
the aperture than to the respective longitudinal side of the
machine bed. Hereby a stronger warp can be reached in the area of
the aperture than in the area of the longitudinal sides in an easy
way.
[0035] In a further preferred embodiment of the punching press, the
means for warping the machine bed are designed to specifically
producing a temperature gradient within the machine bed or within a
supporting structure for the lower tool parts built with the
machine bed, by means of which the machine bed is warped in the
direction towards the press ram as a consequence of locally
different thermal expansion or thermal shrinkage of the machine
bed, respectively, and/or different thermal expansion or thermal
shrinkage, respectively, of components of the supporting structure
for the lower tool parts built with the machine bed. This method of
production of the deformation forces has the advantage that it can
be realised without having to deviate from existing and proven
structural concepts. As already mentioned, this is of outstanding
significance particularly in the field of fast operating high
performance automatic punching machines, because detail work for
years is often needed here to optimize the press structure with
respect to its dynamic behaviour and to its life time. Additionally
the method according to the invention can be applied with little
effort also to existing presses.
[0036] In a preferred embodiment of the punching press, the means
for warping the machine bed are built such that the machine bed in
the area of its side facing the press ram can be heated by them for
effecting the warp due to a non-uniform heating with corresponding
non-uniform spatial thermal expansion of them. Thereby, it is
further preferred that the machine bed is stronger heated by these
means near to the boundaries of the aperture than near to the
longitudinal sides.
[0037] Alternatively or additionally the means for warping the
machine bed are built such that the machine bed in the area of its
side facing away from the press ram can be cooled by them for
effecting the warp due to a non-uniform cooling with corresponding
non-uniform spatial shrinkage of them. Thereby, it is further
preferred that the machine bed is stronger cooled more by these
means near to the boundaries of the aperture than near to the
longitudinal sides.
[0038] For introducing heat or coldness, the punching press
according to the invention can have different arrangements:
[0039] In a preferred embodiment of the punching press, flow
channels are arranged within the machine bed, which are flowed
through by a heated or cooled, gaseous or liquid medium during
intended operation for producing the temperature gradient.
[0040] With advantage, arrangements exist according to a preferred
variant of this embodiment, by means of which heated lubricating
oil of a lubricating oil circuit of the press can be passed through
the flow channels during the intended operation of the press for
producing the temperature gradient. This solution is energetically
very advantageous because practically no heating energy is needed
to provide the heat.
[0041] In a further preferred embodiment of the punching press,
electric heating elements, in particular resistance heating
elements, are arranged within the machine bed, which can be charged
with electric current during the intended operation of the press
for producing the temperature gradient effecting the warp. This
construction allows a particularly good controllable production of
the temperature gradient.
[0042] Preferably, one or more flow channels and/or electrical
heating elements are arranged within the machine bed on both sides
of the aperture of the machine bed in each case, preferably such
that, per side, the sum of the distances of the flow channels
and/or the heating elements to the aperture is smaller than the sum
of the distances of the flow channels and/or heating elements to
the respective longitudinal sides of the machine bed. Thereby, it
is further preferred that the flow channels and/or heating elements
are arranged symmetrically to both sides of the aperture. Hereby,
the desired stronger warp of the machine bed in the area of the
aperture can be effected in a simple way.
[0043] In an even further preferred embodiment, the punching press
has a clamping plate arranged on its machine bed which clamping
plate can be heated, in particular electrically, during the
intended operation of the press.
[0044] In another preferred embodiment, the punching press has a
clamping plate arranged on its machine bed, wherein an in
particular electrical heating device, is arranged between the
machine bed and the clamping plate which can be operated during the
intended operation of the press.
[0045] Thereby according to a preferred variant of these two
embodiments, the clamping plate or the heating device arranged
between the clamping plate and the machine bed, respectively, are
connected with the machine bed such that the clamping plate, if it
is heated, or the heating device, if it is operated, respectively,
heats the machine bed at the side facing the ram for producing the
temperature gradient effecting the warp. Thereby, it is preferred
that the machine bed by the clamping plate or by the heating
device, respectively, is heated stronger near to the boundaries of
the aperture than near to its longitudinal sides.
[0046] According to another preferred variant of these two
embodiments, the clamping plate is connected with the machine bed
in a shear stiff manner, directly or indirectly over the heating
device.
[0047] Thereby according to a first preferred sub-variant, the
heatable clamping plate or the heating device arranged between the
clamping plate and the machine bed, respectively, is basically
thermally decoupled from the machine bed such that during heating
the clamping plate or during operating the heating device,
respectively, it comes basically to a heating up and a
corresponding expansion of the clamping plate by means of which the
warp of the machine bed in the direction towards the press ram is
caused in consequence of the shear stiff coupling of them to the
machine bed.
[0048] The thermal decoupling can be realized expediently by a
thermal insulation layer arranged between the clamping plate and
the machine bed, which effects a reduction of the heat transfer
from the clamping plate to the machine bed.
[0049] Thereby, in a preferred variant, this thermal insulation
layer is present in the areas, which adjoin the longitudinal sides
of the clamping plate or the machine bed, respectively, while in
the areas, which adjoin the aperture, a layer is present between
the clamping plate and the machine bed which has an essentially
better thermal conductivity for privileging a heat transfer from
the clamping plate to the machine bed in these areas. Also by this
measure, the desired stronger warp of the machine bed in the area
of the aperture can be effected in a simple way.
[0050] According to a second preferred sub-variant, the clamping
plate is connected with the machine bed such that it, if it is
heated, heats the machine bed at its side facing the ram or the
heating device arranged between the clamping plate and the machine
bed is connected with the clamping plate and the machine bed such
that it, if it is operated, heats the clamping plate and warms
upthe machine bed at its side facing the ram. By this embodiment,
during heating the clamping plate or during operating the heating
device, respectively, the warp of the machine bed is caused by
shear forces introduced by the clamping plate into the machine bed
in combination with the non-uniform spatial thermal expansion of it
resulting from the heating of the machine bed.
[0051] The use of heatable clamping plates or of heating devices
arranged between the machine bed and the clamping plate is suited
particularly well for the cost effective retrofit of existing
punching presses.
[0052] With advantage, the means for warping the machine bed can be
adjusted and indeed preferably during the intended operation of the
press such that an adjustment of the warp of the machine bed, which
is specific and suited to the respective operating situation, is
possible.
[0053] For this, the punching press has preferably a press control
by means of which the warp of the machine bed is adjustable,
preferably automatically, depending on parameters of the punching
process, preferably depending on a calculated or product-specific
punching force, respectively, or a maximal punching force measured
during operation, and indeed preferably during the intended
operation of the press. Hereby, a process control with automatic
adjustment of the warp of the machine bed to the particular
operating conditions becomes possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Further preferred embodiments of the invention result from
the dependent claims and from the now following description by
means of the figures. Thereby it show:
[0055] FIG. 1 a sectional view through an automatic punching
machine with top drive;
[0056] FIG. 2 a section through the bottom part of the automatic
punching machine along the line X-X in FIG. 1;
[0057] FIG. 3 a view like in FIG. 2 through the bottom structure of
a first automatic punching machine according to the invention;
[0058] FIG. 4 a view like in FIG. 2 through the bottom structure of
a second automatic punching machine according to the invention;
[0059] FIG. 5 a view like in FIG. 2 through the bottom structure of
a third automatic punching machine according to the invention;
and
[0060] FIG. 6 a section along the line A-A in FIG. 5.
DETAILED DESCRIPTION
[0061] In FIG. 1, an automatic punching machine with top drive is
shown wherein the top part of the machine with the drive unit 1,
the ram 2 and the ram guides 3 is shown in section in longitudinal
direction whereas the bottom part of the machine is shown not in
section with the clamping plate 4 and the machine bed 5.
[0062] FIG. 2 shows a section through the bottom part of the
automatic punching machine along the line X-X in FIG. 1, as
designed according to prior art. As can be seen, the clamping plate
4 is arranged on the machine bed 5 and comprises centrally arranged
an aperture 6a which leads in the direction of gravity into an
aperture 6b arranged centrally in the machine bed 5. The apertures
6a, 6b serve for carrying away punching parts and rubbish out of
the punching zone.
[0063] As can be seen further, the machine bed 5 to both sides of
the aperture 6b in each case forms a closed cavity 7a, 7b, which
cavity serves as a tank for the lubricating oil 8 of the
lubricating oil circuit of the automatic punching machine. During
operation, the machine bed 5 is in its lower part stronger heated
by the heated lubricating oil 8 than in its upper part by means of
which it already warps down without punching force load due to
different thermal expansions. Under the load of the punching force,
there is an additional bending of the machine bed 5 during
operation, and subsequently there is a corresponding loss of
precision and an increased tool wear.
[0064] FIG. 3 shows a section through the bottom part of the
automatic punching machine along the line X-X in FIG. 1, as it is
designed according to a first embodiment of the invention. As can
be seen, the outer contours of the clamping plate 4 and of the
machine bed 5 are identically here to the embodiment according to
FIG. 2. However, the inner structure of the machine bed 5 differs
clearly from that in FIG. 2. In the present case, the machine bed 5
at both sides of the aperture 6b in each case forms two closed
cavities 9a, 9b; 9c, 9d arranged one upon the other, out of which
only the upper ones 9a, 9c in each case serve as tank for the
lubricating oil 8 of the lubricating oil circuit of the automatic
punching machine. Above the cavities 9a, 9b; 9c, 9d, the machine
bed 5 at both sides each of the aperture 6b in each case comprises
three flow channels 10a, 10b, 10c; 10d, 10e, 10f arranged side by
side, out of which in each case the flow channels 10c, 10d arranged
closest to the aperture 6b have a clearly bigger flow cross-section
than the remaining flow channels 10a, 10b, 10e, 10f. The flow
channels 10a-10f are flowed through by the heated lubricating oil 8
of the lubricating oil circuit of the automatic punching machine
during operation, which lubricating oil is subsequently guided into
the cavities 9a, 9c, wherefrom it is passed again to the
lubricating points of the punching machine by the lubricating oil
pump of the lubricating oil circuit, if applicable after previously
going through a cooling device. Thereby, the heated lubricating oil
8 is passed firstly through the flow channels 10c, 10d arranged
closest to the aperture 6b, then through the central flow channels
10b, 10e and at the end through the outer flow channels 10a, 10f,
thereby transferring heat to the machine bed 5. Hereby, the machine
bed 5 in its upper area is stronger heated than in its lower area
during operation, by means of which machine bed due to of different
thermal expansion warps upwards and therefore in the direction of
the ram 2.
[0065] Thereby, the machine bed 5 is stronger heated in the areas
adjacent to the aperture 6b than in the areas at its longitudinal
sides as a consequence of the sequence of the flow through the flow
channels and of the different flow channel cross-sections, which
leads to a stronger warp of it upwards in the areas adjacent to the
aperture 6b than in the areas of its longitudinal sides.
[0066] The clamping plate 4, which is fixed on the machine bed 5 by
a plurality of screw connections, follows the warp of the machine
bed 5. During operation, under the load of the punching force there
is a compensation of this warp caused by thermal expansion such
that the machine bed 5 in the ideal case is flat under maximal
punching force load both in longitudinal and in cross direction,
i.e. not warped or not bended, respectively. Hereby, it can be
counteracted a loss of punching precision and an increased tool
wear effectively.
[0067] FIG. 4 shows a section through the bottom part of the
automatic punching machine along the line X-X in FIG. 1, like it is
designed according a second embodiment of the invention. As can be
seen, the outer contours of the clamping plate 4 and of the machine
bed 5 are identical here to the embodiment according to FIG. 2, and
also the inner structure of the machine bed 5 is identical to that
of the machine bed of FIG. 2. However, an intermediate plate 11 is
arranged here between the clamping plate 4 and the machine bed 5
with a plurality of flow channels 10a-10l, which are flown through
by a warm water circuit during operation, e.g. from a re-cooling
device of the lubricating oil circuit of the automatic punching
machine. Thereby, the warm water is passed first through the flow
channels 10d, 10e, 10h, 10i which are closest to the boundaries of
the aperture 6b in the machine bed 5, then through the inner and
central flow channels 10c, 10f, 10g, 10j arranged beside them and
at the end through the outer flow channels 10a, 10b, 10k, 10l.
Thereby, the intermediate plate 11 is heated by the warm water
circuit and heats on its part the contact faces of the machine bed
5 and the clamping plate 4 abutting to it. Hereby again, the
machine bed 5 in its upper part is heated stronger than in its
bottom part, by means of which it warps upwards, i.e. in the
direction towards the ram 2, as a consequence of different thermal
expansion.
[0068] Because here the heating by the flow channels 10d, 10e, 10h,
10i arranged closest to the boundaries of the aperture 6b is the
strongest, the machine bed 5 warps in the areas adjacent to the
aperture 6b more upwards than in the areas of the longitudinal
sides which are heated less strong by the outer flow channels 10a,
10b, 10k, 10l. The clamping plate 4, which is connected in a shear
stiff manner with the machine bed 5 via the intermediate plate 11
and is made of a material witch has a bigger heat expansion
coefficient than the material of the machine bed 5, transfers
additional shear forces into the machine bed 5 which increase the
warp towards upwards. Like at the embodiment according to FIG. 3,
there is a compensation of this warp during operation under the
load by the punching force, which in ideal case leads to the
situation that the machine bed 5 is flat both in longitudinal and
in cross direction under maximal punching load, i.e. not warped or
not bended, respectively. This solution has the advantage that
existing machines with a corresponding intermediate plate 11 can be
converted in a simple way into a punching press according to the
invention.
[0069] FIG. 5 shows a section through the bottom part of the
automatic punching machine along the Line X-X in FIG. 1, as it is
designed according to a third embodiment of the invention. As can
be seen, the outer contours of the clamping plate 4 and of the
machine bed 5 are essentially identical here like at the embodiment
according to FIG. 2, and also the inner structure of the machine
bed 5 is basically identical with that one of the machine bed of
FIG. 2. However, the machine bed 5 in its bottom part is crossed
here by two tie-rods 19 expanding in longitudinal direction of the
machine bed, by means of which the machine bed 5 is set under
compressive stress in its bottom part for warping the machine bed 5
in the direction towards the press ram 2. The tie-rods 19 are
arranged symmetrically at both sides of the aperture 6b of the
machine bed 5 such that in each case they have a smaller distance
to the aperture 6b than to the respective longitudinal side of the
machine bed 5.
[0070] Because by this arrangement the tie-rod 19 the areas of the
machine bed 5 which are arranged nearest to the boundary walls of
the aperture 6b are set strongest under compressive stress by the
tie-rod 19, the machine bed 5 warps in the areas adjacent to the
aperture 6b stronger upwards than in the areas of the longitudinal
sides. The clamping plate 4, which is connected with the machine
bed 5 by a plurality of screws, warps together with the machine bed
5. Like at the embodiments according to the FIGS. 3 and 4, there is
a compensation of this warp during operation under the load by the
punching force, which warp ideally leads to the situation that the
machine bed 5 is flat both in longitudinal and in cross direction
under maximal punching force load, i.e. not warped or not bended,
respectively.
[0071] As could be seen in FIG. 6, which shows a longitudinal
section through the bottom structure of FIG. 5 along the Line X-X
in FIG. 5, the tie-rods 19 in each case are set under tension
stress between a nut 12 and an adjustable pre-loading device 13,
14, 15, 16, 17, 18. The pre-loading device 13, 14, 15, 16, 17, 18
comprises a clamping nut 13 with an actuating lever 16, which
clamping nut can be twisted by a hydraulic cylinder 15 by about
90.degree., for adjusting the tension stress of the tie-rod 19 and
an unloading device with a hydraulic piston/cylinder arrangement
14, 17, 18 by means of which the tie-rod 19 can temporarily be
hydraulically pre-loaded, for unloading the clamping nut 13 during
adjustment of it. After adjusting the clamping nut 13, the
hydraulic piston/cylinder arrangement 14, 17, 18 is switched
ineffective for the operation of the press.
[0072] At the bottom side of the machine 5, a strain meter 20 is
arranged below every tie-rod 19 by means of which the length
shortening of the machine bed 5 can be measured in this area as a
consequence of the appliance of compressive stress by the tie-rod
19.
[0073] This third embodiment of the invention has the advantage
that the adjustment of the warp of the machine bed 5 is without any
time lag and that the deformation forces or the resulting
deformations of the machine bed 5, respectively, are well
controllable.
[0074] While the present disclosure has been illustrated and
described with respect to a particular embodiment thereof, it
should be appreciated by those of ordinary skill in the art that
various modifications to this disclosure may be made without
departing from the spirit and scope of the present disclosure.
* * * * *