Patent Application
20190143624
The present application claims priority of German Application Number 10 2017 120 192.0 filed Sep. 1, 2017, the disclosure of which is hereby incorporated by reference herein in its entirety.
The disclosure relates to a downholding press for producing a semi-finished product from sheet-metal material having thickness-reduced regions.
The disclosure furthermore relates to a method for producing a sheet-metal formed part having mutually dissimilar wall thicknesses.
The production of motor vehicle components is well known from the prior art for metal sheets to be formed. To this end, metal sheets from steel alloys but also metal sheets from light-metal alloys are used.
The forming method is performed in such a manner that the sheet-metal material is provided in the form of a blank having a consistent wall thickness and is formed to the desired sheet-metal formed part. Such sheet-metal formed parts in the automotive sector, consequently motor vehicle components, are for example longitudinal beams, cross beams, crash boxes, or other structural body components. Axle components such as, for example, arms, axle sub frames, or similar, can also be produced by means of such forming methods.
In order for the omission of CO2 to be reduced or for crash properties to be improved while simultaneously improving the properties of driving dynamics, the implementation of light construction measures is required.
Sheet-metal formed parts for motor vehicles are dimensioned in such a manner that said sheet-metal formed parts have an ideally low deadweight while having sufficient rigidity properties as required. To this end, tailored formed blanks are known from the prior art. Blanks which have mutually dissimilar wall thicknesses and/or dissimilar material properties are thus provided. For example, two metal sheets having mutually dissimilar wall thicknesses are welded together and subsequently formed to the sheet-metal formed part. A blank can also be partially rolled and subsequently be formed to the motor vehicle component.
A method for producing a sheet-metal formed part having mutually dissimilar wall thicknesses in regions, in which a convexity on a sheet-metal material having initially a consistent wall thickness is generated in a downholding press, is furthermore known from DE 10 2015 103 721 B3. This convexity elongates the sheet-metal material in a localized manner. The sheet-metal material in terms of the wall thickness thereof is thus reduced in the elongated region. After the sheet-metal material having the convexity is subsequently straightened, a semi-finished product or a blank, respectively, which has mutually dissimilar wall thicknesses is thus provided. Further forming to the sheet-metal formed part can then be carried out subsequent thereto.
The advantage of this method is that as opposed to, for example, the case of localized rolling of the blank in which the rolling process has to be carried out across the entire width of the blank, a region can be elongated in a targeted manner by localized elongation, for example in an inner region of the blank.
The entire content of the aforementioned publication is incorporated in this document by way of reference.
It is an object of at least one embodiment of the disclosure to further improve a downholding press for producing a semi-finished product and a method for producing a sheet-metal formed part.
The aforementioned object is achieved by a downholding press for producing a semi-finished product from sheet-metal material having thickness-reduced regions, wherein the semi-finished product after forming has regions with mutually dissimilar wall thicknesses and the downholding press has an upper tool and a lower tool as well as a downholding element, and a convexity on the sheet-metal material is generated between the upper tool and the lower tool such that the sheet-metal material is reduced in thickness in regions by elongation. A blocking cam is configured on the downholding element in such a manner that a follow-on of the sheet-metal material is suppressed. The aspect of the object in terms of method technology is furthermore achieved by a method for producing a sheet-metal formed part by providing a sheet-metal material having a wall thickness; preforming the sheet-metal material to a semi-finished product as a preform by way of a downholding press, wherein at least one convexity is generated in an internal region of the sheet-metal material such that the material is elongated and has a reduced wall thickness, wherein a downholding element is disposed externally on this region, said downholding element having at least one blocking cam in such a manner that the sheet-metal material is jammed by the downholding element and does not continue to flow in from the outside; flattening and/or spreading the preform thus produced; wherein the sheet-metal material is singularized to a blank before, during, or after preforming; optional trimming and/or perforating of the blank; and forming the blank to the sheet-metal formed part.
The downholding press is provided for producing a semi-finished product from sheet-metal material having thickness-reduced regions, wherein the semi-finished product after forming in the downholding press has regions with mutually dissimilar wall thicknesses. The downholding press has an upper tool and a lower tool. The upper tool and the lower tool can also be referred to as the female die and the male die.
The downholding press furthermore has a downholding element. The downholding element can come to bear on the lower tool. However, the downholding element can also come to bear on a bearing face that is opposite the downholding element and is not part of the lower tool. The sheet-metal holder can also already be part of the lower tool but not directly of the male die. Moreover, the male die and the female die can also be reversed such that the female die is disposed in the lower tool.
A convexity on the sheet-metal material is generated between the upper tool and the lower tool. The convexity requires an increase in length which at the same time requires a reduction in the wall thickness. The region of the sheet-metal material is thus reduced in thickness by way of an elongation. Said region is the region which lies within the downholding element.
According to at least one embodiment it is now provided that a blocking cam is configured on the downholding element per se in such a manner that a follow-on of the sheet-metal material is suppressed.
According to at least one embodiment it is thus provided that the sheet-metal material is jammed and held tight in the region of the downholding element such that a follow-on or a successive feed of the sheet-metal material from a region outside the downholding element is substantially completely suppressed. The wall thickness in the region enclosed by the downholding element, or in the inner region of the sheet-metal material that is enclosed between two downholding elements, respectively, can thus be elongated and thus reduced in thickness in a targeted manner by way of the produced geometry of the convexity.
The blocking cam is configured as a cam or protruding feature, respectively, that projects beyond the downholding element. The blocking cam per se in cross section can be configured so as to be rounded, but also so as to be angular, rectangular or trapezoidal or graduated in multiple steps in cross section. The blocking cam in plan view is configured so as to be linear. The blocking cam can also be configured as an interrupted line. In the case of punctiform blocking cams, a plurality of blocking cams are disposed so as to be distributed beside one another, on one line. In the case of a blocking cam that runs in a linear manner, said blocking cam can run in a straight line. The linear blocking cam can however also run in an arcuate or undulated manner. On account thereof, the blocking effect which prevents a continuing flow of material from the outside can be improved.
In one or more embodiments of the disclosure, a blocking seam is configured on or in a bearing face that lies opposite the downholding element. The blocking seam can be configured in such a manner that said blocking seam has a geometry which is configured so as to be complementary to that of the blocking cam. In the converging of the downholding press the sheet-metal material is thus enclosed and held tight, or fixed or jammed, respectively, between the blocking cam and the blocking seam. The blocking seam in relation to a surface is configured so as to be widened and depressed by the dimension of the sheet-metal thickness.
Alternatively, two blocking cams can also be configured on one bearing face in such a manner that the blocking cam of the downholding element in this instance in the converging engages either in the blocking seam or between the two blocking cams while enclosing the sheet-metal material. An inverse arrangement is likewise conceivable. Two blocking cams are thus configured on the downholding element as well as one blocking cam on the bearing face. In the converging of the downholding press the blocking cam of the bearing face in this instance comes to bear in a form-fitting manner between the two blocking cams of the downholding element, the same applying to blocking cams and blocking seams.
To this end, the blocking cams project by way of less than 10% of the sheet-metal thickness such that the blocking cams penetrate the material at most up to 10% and suppress a continuing flow from the outside. This means, the material lying on the outside has the original wall thickness. After the release of the downholding element, a penetration in the region of the blocking cam is barely noticeable by virtue of the minor penetration depth.
In one or more embodiments of the disclosure, the blocking cam of the downholding element in the open state projects in such a manner that the blocking cam in the closing of the downholding press comes to bear on the sheet-metal material ahead of the upper tool. It can thus be guaranteed in the positioning of the sheet-metal material in the downholding press that the sheet-metal material is first jammed by the blocking cam of the downholding element and is subsequently correspondingly formed and elongated by way of the convexity by further converging the upper tool and the lower tool.
The blocking cam in cross section can furthermore have a rounded contour. This has an advantageous effect on the sheet-metal material in that the latter is not constricted or kinked on the corner regions otherwise present, such that cracks could form here later. Depending on the specific application, the blocking cam in cross section can however also have an angular contour. Fixing or jamming, respectively, in the regions of the corners is performed by way of a high retention force such that a continuing flow of the sheet-metal material is specifically avoided. A hybrid form is configured such that the blocking cam, or blocking seam, respectively, to be generated in the direction of the elongation has an angular contour in cross section, wherein the corner or edge, respectively, that is disposed in the direction toward the elongation is configured so as to be rounded. The highest stress in the direction of traction arises at this corner or edge, respectively, such that any constriction or notch formation, respectively, is avoided. Positive fixing is performed on account of the angular contours of the blocking cam and the blocking seam that are disposed on the side opposite the elongation direction, such that a continuing flow is avoided.
A critical reduction in thickness, or a constriction, respectively, or even bending or kinking of the sheet-metal material is thus avoided specifically in this region.
The disclosure furthermore relates to a method for producing a sheet-metal formed part having mutually dissimilar wall thicknesses. The sheet-metal formed part is used as a motor vehicle component from a steel material or a light-metal material. The method is distinguished by the following features:
The method is carried out on a downholding press described above. In the context of at least one embodiment, a sheet-metal material having a uniformly consistent wall thickness can be used, said sheet-metal material being converted by a method to a so-called tailored blank, consequently to a semi-finished product that is configured so as to be adapted to stress and/or forming. However, it is also possible for a sheet-metal material to be used that already has dissimilar wall thicknesses in cross section or in longitudinal section, so as to achieve by the method according to at least one embodiment a more targeted distribution of thickness and thus a maximum light construction potential in the sheet-metal formed part. In the context of at least one embodiment a so-called tailored extruded blank from a light-metal alloy can also be used as sheet-metal material, said tailored extruded blank being produced according to EP 3 170 570 A1 by extrusion and having dissimilar wall thicknesses in cross section. Said tailored extruded blank is then once more elongated in a localized manner.
In an advantageous refinement of the method it is furthermore provided that a convexity is not only produced in an inner region but rather a plurality of convexities in each case one inner region are produced simultaneously on a preform. These convexities can be configured in opposite directions, for example, but also in the same direction. Further convexities, for example three, four, or more convexities, can also be provided for elongating an inner region. This has an advantageous effect on the subsequent process for producing a blank from the preform.
The process can also be carried out by hot-forming technology and press-hardening technology. To this end, the straightened blank austenitized at least in regions is hot-formed and hardened. It would also be conceivable for the production of the preform to be carried out as at least a semi-hot forming process or a hot-forming process, since the shape-imparting degrees of freedom are enhanced here in the case of a steel alloy that is capable of hardening. Thermal pre-treatment methods in order to achieve corresponding shape-imparting degrees of freedom, or in order to subsequently set desired hardening properties in a targeted manner, respectively, are likewise possible when light-metal alloys are used.
Further advantages, features, properties, and aspects of the disclosure are the subject matter of the description hereunder. One or more of the embodiments will be illustrated in schematic figures.
For an understanding of embodiments of the disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
In a further method step, a compression forming tool 5 is shown here in which the produced preform 6 is flattened and thus a blank 7 having a central elongated region 16 having a reduced wall thickness W1 is produced. Said blank 7 has a length L1, wherein the length L1 is longer than the length L, and the wall thickness W1 in the elongated region is smaller than the wall thickness W of the original sheet-metal blank 1, said wall thickness W still being present in the respective peripheral region, or in the non-preformed regions of the blank 7, respectively. The flattening is performed as crash forming such that no further centering or adjustment is required. In the shaping to be produced later in a forming tool (not illustrated in more detail here) self-centering in the forming tool can be performed by virtue of the transition in thickness, or else by virtue of the convexity (preform), from the elongated regions having a reduced wall thickness W1 to regions having a regular wall thickness W.
The preform thus produced is illustrated in
Two intermediate portions 27 are configured in the spring bridge 26, wherein the reduced wall thickness is produced in the intermediate portions 27. The original wall thickness is present in a respective end portion 28 as well as in a central portion 29. An elongation by way of blocking cams 8 is carried out herein in a downholding press 2 according to the disclosure, wherein blocking cams 8 are in each case disposed to the left side and to the right side of the intermediate portion 27 such that the wall thickness here is elongated by the convexity and thus reduced in thickness.
The foregoing description of some embodiments of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. It should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017120192.0 | Sep 2017 | DE | national |
