EP3519121B1 - Method for producing components having an adjusted bottom region - Google Patents

Description

The invention relates to a method for producing a component, the method comprising preforming a workpiece to form a preformed component having a base region, a frame region and a flange region, such that the preformed component has a material surplus for the frame region and/or the base region and/or the flange region, and calibrating the preformed component to form an at least partially final-formed component having a base region, a frame region and a flange region.

During the production of deep-drawn components, especially open profile components with a U-shaped or hat-shaped cross-section, for example by deep drawing, shape changes usually occur after the component is removed from the tool due to unavoidable elastic springback, for example in the form of springback between the base and the sides of the component or curvature of the sides and/or the base. As a result, components manufactured in this way may not be sufficiently dimensionally stable, depending on the application. This effect is more pronounced with high-strength steel materials or aluminum materials and with thin sheet thicknesses.

To counteract this, calibration is used. This involves first producing a preformed component (preform) with a material surplus (also called material allowance or compression allowance), for example, by deep drawing. However, the indifferent springback of the component that occurs when the load is removed is subsequently realigned through a calibration step using compressive stress superposition, resulting in a component that is at least partially fully formed and dimensionally accurate.

In the state of the art, when using this method, it is particularly intended to use the excess material for the calibration process in the floor areas in the form of one or more waves. During the calibration process itself, however, each wave collapses in the base area into two or more smaller waves. Depending on the additional length produced by the excess material, these waves collapse into even smaller waves. This effect can repeat itself several times until the calibration stamp reaches its final position.

From the printed matter DE 10 2011 005 002 A1 A method for producing a dimensionally accurate component is known. RU 21 94 590 C2 A method for producing a flangeless component is known.

The described effect depends on the size of the excess material, the sheet thickness, the base width and the wave height and leads to deviations from a uniform and/or smooth surface (surface defects) in the base area of the final formed component, at least in some areas, with negative effects on the surface quality in the form of residual waviness, surface irregularities and/or sheet thickness variations or combinations of the aforementioned defects.

Furthermore, the US 2014/356643 A1 , on which the preamble of claim 1 is based, a preforming and a calibration of a steel part in a tool.

Against this background, it is the object of the invention to provide a method which reduces or avoids the described surface defects and enables sufficiently smooth surfaces even in the base area of the calibrated component after the calibration process.

The object is achieved in a generic method of the invention with the features of claim 1.

In contrast to the state of the art, the different approach is taken that the base area of the preformed component essentially has the geometry of the base region of the at least partially finally formed component. For example, the base region can be flat. The base region therefore needs to be subjected to no or only a slight change in shape during calibration, which further reduces the risk of undesirable surface defects in the at least partially finally formed component. In other words, the base region of the pre-formed component can essentially retain its shape during calibration. This means that the excess material is therefore provided, for example, predominantly in the area of the foot of the frames and/or the edge or border area of the base and, for example, uniform areas in the at least partially finally formed component are also provided as a uniform area in the pre-formed component. Preferably, the excess material is only provided in the border area of the base. Particularly preferably, the excess material is provided by the shape of the transition area between the base region and the border area and/or by the shape of the transition area between the flange area and the border area of the pre-formed component. It has been shown that in this way the advantages of processes for the production of dimensionally accurate components which require no or only minimal trimming can be retained, but at the same time surface defects in the base area and/or in the flange area can be reduced or even avoided.

The base area of the preformed component preferably has no excess material for calibration or even a material deficiency in the preformed component. The excess material actually required for the base area is then preferably provided essentially by the transition area between the base and the frame area of the preformed component.

A uniform and/or smooth surface is understood here to mean that the shape profile of the surfaces produced according to this invention, in particular of the bottom area of the at least partially final-shaped component, only has waves with small amplitude, for example less than 0.2 mm, and large wavelength, for example greater than 10 mm.

The workpiece is, for example, a substantially flat blank, such as a sheet metal. The workpiece is preferably made of a steel material. However, other metal materials, such as aluminum, can also be used. The component is preferably a sheet metal component.

Preforming is carried out, in particular, by means of deep-drawing-like forming, which can be performed in a single or multi-stage process. Any combination of drawing, embossing, raising, edging, and/or bending is also conceivable. The process for producing the preformed component can therefore be customized. The preformed component obtained by preforming can, in particular, be considered a component essentially close to its net shape, which, with the smallest possible deviations, already essentially exhibits the intended geometry.

Calibration can therefore be understood, in particular, as the final forming or final shaping of the preformed component, which can be achieved, for example, through one or more pressing processes. Calibration particularly includes a compression process. For example, the frame area, the base area, the flange area, and/or the transition areas of the preformed component are subjected to compression.

However, it is possible that the at least partially final-shaped component can be subjected to further processing steps, such as the creation of connection holes and/or a trimming process and/or post-forming, such as pressing and/or bending. However, preferably, no further main forming steps are necessary.

The described preforming and calibration are preferably carried out sequentially.

According to a preferred embodiment of the method according to the invention, the shape of the transition region between the base region and the frame region of the preformed component leads to a raised or lowered base region of the preformed component. This allows a sufficient excess of material to be introduced into the transition region of the preformed component without, however, having to modify the geometry of the entire base region. Rather, the base region can be raised or lowered as a whole. Preferably, a raised base region is achieved by a transition region that is essentially U-shaped in cross-section. In particular, a substantially uniform raising or lowering across the entire base region is provided. The base region of the preformed component is raised or lowered, in particular compared to the frame base. Compared to the base region of the fully formed component, the base region of the preformed component is thus also raised or lowered. A raised or lowered floor area is understood to mean, in particular starting from the same frame end level or frame head (length level), a raised or lowered floor area compared to the lower floor level (zero level) of a component in which the same excess material is achieved by one or more floor waves extending over the entire floor area.

According to a preferred embodiment of the method according to the invention, the excess material is provided essentially or exclusively by the transition region between the base region and the frame region of the preformed component. This eliminates the need for any further geometric modifications in the base region of the preformed component to provide excess material. This particularly enables a defect-free and smooth base region on the at least partially final-formed component.

According to a preferred embodiment of the method according to the invention, the shape of the transition region between the base region and the frame region of the preformed component, seen in cross section, provides an additional length for the base region and/or the frame region of the preformed component.

By providing excess material in the form of an additional length, the risk of material defects and uneven surfaces on the component that is at least partially finally formed is further reduced, for example in contrast to excess material in the form of waves distributed in the base area.

According to a preferred embodiment of the method according to the invention, by calibrating the preformed component to the at least partially fully formed component, a material flow into the frame area of the preformed component is achieved. For example, the material flow occurs from the transition area and/or the base area of the preformed component. This can have the advantage that the excess material does not require an additional extension of the frame area of the preformed component, since the material flow can provide sufficient material in the frame area.

According to a preferred embodiment of the method according to the invention, preforming is carried out by a deep-drawing-like operation with or without a hold-down device. Preforming with preferably spaced hold-down devices improves material guidance and process stability. However, for components with a simple geometry, such as U-shaped or hat-shaped components in cross-section, the hold-down devices can be omitted during deep drawing. This design is also referred to, for example, as stamping the base with raised sides. This process can be performed in one or more process steps.

According to a preferred embodiment of the method according to the invention, the base region of the preformed component is subjected to a force during calibration, which enables compression of the base region of the preformed component and essentially prevents collapse of the excess material. For example, the base region is subjected to force on both sides. This achieves solidification in the base region during compression of the base, but without causing surface defects.

According to the invention, preforming is carried out in a preforming tool comprising a preforming punch, a preforming die, and a preforming die base movable relative to the preforming die. The workpiece is arranged between the preforming punch and the preforming die base, and the workpiece is preformed by a relative movement between the workpiece with the preforming punch and the preforming die base on the one hand, and the preforming die on the other. The workpiece is fixed, for example clamped, between the preforming punch and the preforming die base. Optionally, hold-down devices or sheet metal holders can also be provided, which enable more reliable forming, particularly with more complex component geometries. This design allows preforming to be implemented with minimal process engineering effort and, in particular, can be integrated into press-supported processes.

Furthermore, according to the invention, calibration is carried out by a calibration tool comprising a calibration punch, a calibration die, and a calibration die base movable relative to the calibration die, wherein the preformed component is arranged between the calibration punch and the calibration die base, and wherein the preformed component is calibrated by a relative movement between the preformed component with the calibration punch and the calibration die base on the one hand, and the calibration die on the other. In particular, by a separate design of the calibration die and the calibration die base, the forces acting during calibration can be precisely controlled in terms of time and location. Furthermore, by means of this design, calibration can also be implemented with little process engineering effort and can be integrated, in particular, into a press-supported process.

According to a preferred embodiment of the method according to the invention, for calibrating the preformed component, the calibrating die frames of the calibrating tool, which define the frame area of the at least partially final-formed component, are moved towards each other. The preformed component can thus They are first inserted into the calibration tool with the calibration die frames open, which can then be closed. This allows, in particular, even components with strong springback to be reliably inserted into the calibration tool.

According to a preferred embodiment of the method according to the invention, the calibration die frames of the calibration tool used for calibrating the preformed component can be designed such that the calibration die frames can preferably be moved in the flange area of the preformed component.

The method according to the invention can be carried out using a device, wherein the preforming tool is designed for preforming the workpiece in such a way that the excess material is provided essentially by the shape of the transition region between the base region and the frame region and optionally essentially by the shape of the transition region between the flange region and the frame region of the preformed component. For example, this is achieved by the geometry of the preforming tool, for example the preforming punch and/or the preforming die base of the preforming tool. As already explained, the device therefore does not distribute the excess material over the entire base region of the preformed component as previously (for example in the form of one or more waves), but instead provides it in the transition region essentially between the base region and the frame region and optionally essentially by the shape of the transition region between the flange region and the frame region of the preformed component. Thus, the advantages of processes for the production of dimensionally accurate components can be combined with further reduced or even avoided surface defects in the base area.

According to one embodiment of the device, the preforming tool comprises a preforming punch, a preforming die, and a preforming die base that is movable relative to the preforming die. This allows the workpiece to be arranged between the preforming punch and the preforming die base and thereby and preform the workpiece through a relative movement between the workpiece with the preforming punch and the preforming die base on the one hand, and the preforming die on the other. Optionally, the preforming tool also features external hold-down devices or sheet holders, which can positively control the material flow, particularly with more complex component geometries, to ensure wrinkle-free forming. This design allows preforming to be realized with minimal process complexity, and the preforming tool can be integrated, in particular, into a press.

According to one embodiment of the device, the calibration tool comprises a calibration punch, a calibration die, and a calibration die base movable relative to the calibration die. This allows the preformed component to be arranged and preferably fixed between the calibration punch and the calibration die base. The preformed component can then be calibrated by a relative movement between the preformed component with the calibration punch and the calibration die base on the one hand, and the calibration die on the other. As already explained, by designing the calibration die and the calibration die base separately, the forces acting during calibration can be precisely controlled in terms of time and location. Furthermore, calibration can be implemented with minimal process engineering effort, and the calibration tool can be integrated, in particular, into a press.

According to an alternative design of the device, the movable calibration die base can be omitted. To guide the preformed component into the tool during the calibration process, spring-loaded preforms can be provided in the calibration punch, which press the component into the die in advance. The spring-loaded preforms are then displaced into the punch when the tool closes. This results in a simpler tool design.

According to one embodiment of the device, the calibration die comprises at least two separate calibration die frames that are movable relative to each other. The preformed The component can thus first be inserted into the calibration tool with the calibration die frames open, which can then be closed, which facilitates the insertion of highly resilient, pre-formed components.

With regard to further embodiments of the device, reference is made to the explanations of the method according to the invention.

Fig. 1a-c

eine schematische Darstellung eines Kalibrierens gemäß dem Stand der Technik;

Fig. 2a

eine schematische Darstellung eines vorgeformten Bauteils gemäß dem Stand der Technik;

Fig. 2b, c

schematische Darstellungen beispielhafter vorgeformter Bauteile aus Ausführungsbeispielen erfindungsgemäßer Verfahren;

Fig. 3a, b

schematische Darstellungen eines beispielhaften Vorform-Werkzeugs und eines beispielhaften Kalibrier-Werkzeugs gemäß einem Ausführungsbeispiel einer Vorrichtung; und

Fig. 4

eine schematische Darstellung eines Ablaufs eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens.

The invention will be explained in more detail below using an exemplary embodiment in conjunction with the drawing. The drawing shows

Fig. 1a-c

a schematic representation of a calibration according to the state of the art;

Fig. 2a

a schematic representation of a preformed component according to the prior art;

Fig. 2b, c

schematic representations of exemplary preformed components from embodiments of methods according to the invention;

Fig. 3a, b

schematic representations of an exemplary preforming tool and an exemplary calibration tool according to an embodiment of a device; and

Fig. 4

a schematic representation of a sequence of an embodiment of a method according to the invention.

Fig. 1a-c shows a schematic representation of a calibration process according to the prior art. The prior art provides for a material surplus for the calibration process in the form of one or more waves in the base area of a preformed component 1 and thus distributes it over the entire base area ( Fig. 1a ). However, when calibrating using an upsetting punch 2 and an upsetting die 4, each wave in the base area of the component 1 collapses into two or more smaller waves ( Fig. 1b ). Depending on the additional lengths produced by the excess material, these fail in turn into two even smaller waves of higher order ( Fig. 1c ). This effect can be repeated several times until the calibration stamp reaches its end position.

Fig. 2a shows a schematic representation of the preformed component 1 from Fig. 1 According to the state of the art. Component 1 has excess material, particularly in its base area, in the form of a bump extending across the entire base area. The dashed line 6 indicates the frame end level or length level aligned with the frame end. The dashed line 8 indicates the lower base level (zero level) of the preformed component 1.

The Fig. 2b, c now show schematic representations of exemplary preformed components 10a, 10b, which are manufactured within the scope of exemplary embodiments of the inventive method. In the components 10a, 10b, the excess material is provided by the shape of the transition region 16 between the base region 12 and the frame region 14 of the preformed component. The shape of the transition region 16 between the base region 12 and the frame region 14 of the preformed components 10a, 10b leads to a raised above the zero level ( Fig. 2b ) or lowered below the zero level 8 ( Fig. 2c ) Bottom area of the preformed component. The excess material is provided exclusively by the respective transition area 16 between the bottom area 12 and the frame area 14 of the preformed component 10, 10b. The bottom area 12 of the preformed component 10a, 10b is flat and thus essentially already has the intended flat geometry of the at least partially final formed base area. The additional length provided by the excess material in cross-section for the frame area and the base area is shown in the Figures 2a to 2c even.

In the following, an embodiment of a device according to the invention and an embodiment of a method according to the invention in connection with Fig. 3 and Fig. 4 be described. The Fig. 3a , b show schematic representations of an exemplary preforming tool 30 and an exemplary calibration tool 40 according to an embodiment of a device according to the invention, while Fig. 4 shows a schematic representation of a sequence of an embodiment of a method according to the invention.

The preforming tool 30 is designed to preform a workpiece 20 into a preformed component 20' with a base region 22 and a frame region 24, so that the preformed component 20' has a material surplus for the frame region 24 and/or the base region 22. The preforming tool 30 comprises a preforming punch 32, a preforming die 34 and a preforming die base 36 that is movable relative to the preforming die 34. The preforming tool 30 also comprises an optional hold-down device 38. The liftable preforming die base 36 is modified in its shape so that by means of the preforming tool, a shaping according to Fig. 2b (or alternatively according to 2c).

Alternatively, and not shown here, the production of the preformed component can be carried out in a first step by at least partially embossing the base area and in a second or further step by raising or bending the frame area.

The calibration tool 40 serves to calibrate the preformed component 20' to an at least partially final formed component 20" with a base region 22 and a frame region 24. The calibration tool 40 comprises a calibration stamp 42, a calibration die 44 and a calibration die base 46 movable relative to the calibration die 44. The calibration die base 46 can be moved at a distance from the calibration punch 42 using suitable means such as external fixed distances. The calibration die 44 comprises two separate calibration die frames 44a, 44b that are movable relative to one another and can be adjusted laterally. During the process, the calibration tool 40 can close, whereby the calibration punch 42 can displace the calibration die base 46 with the preformed component in between into the then closed calibration die frames 44a, 44b (see also Fig. 4g ), so that the raised base area 22 of the preformed component is leveled and the frame area 24 is compressed to the desired size (see also Fig. 4h ).

During the process, the movable preform die base 36 is first extended to the height of the die support surface of the preform die 34 or slightly above it. Subsequently, the workpiece 20 (blank) is inserted into the preform tool 30 ( Fig. 3a , 4a ) and optionally between the hold-down devices 38, which are fixedly spaced from the preform die 34, secured against displacement by guide pins and/or holes ( Fig. 4b For simply designed components (primarily U-shaped or hat-shaped components), the optionally spaced hold-down clamps 38 can be omitted and the so-called stamping with raised positions can be performed. Until the workpiece 20 is positively stamped between the preform punch 32 and the preform die base 36, only pins on edges or holes secure the workpiece 20.

The assembly of preform punch 32 and preform die base 36 then lowers into the lower end position ( Fig. 4c ). This leads to the formation of the frame areas 24 of the preformed component 20'. The preformed component 20' can then be removed from the preforming tool 30. In this case, springback occurs, particularly in the frame area 24 ( Fig. 4d, 4e ). The preformed component 20' is now inserted into the calibration tool 40.

The calibration die base 46 was already raised to a defined height before the insertion of the preformed component 20', which contacts the inserted base area 22 of the preformed component 20'. Then, the preformed component 20' is loaded, whereby the preformed component 20' should preferably be in a stable position between the two calibration die frames 44a, 44b and the calibration die base 46 at the start of the process ( Fig. 3b , Fig. 4f ).

Subsequently, the calibration punch 42 and the calibration die base 46 are closed at a distance from each other, whereby the base region 22 of the preformed component 20' is secured and essentially not clamped. This allows for a largely free flow of material in the base region 22 without inhibiting the subsequent calibration effect, but essentially prevents the formation of waves in the base region 22 due to the resulting compressive stress during calibration. After the calibration punch 42 has secured the base area 22 of the preformed component 20' between itself and the raised calibration die base 46 against rough slipping, the two calibration die frames 44a, 44b move against the calibration punch 42 until the precisely defined calibration gap is established between the calibration die frames 44a, 44b and the calibration punch 42 and the spring-backed frame area 24 of the preformed component 20' is aligned therein ( Fig. 4g ).

In the further course of the process, the calibration punch 42 is lowered to its final position. In doing so, it also displaces the raised calibration die base 46, which is guided at a distance from the calibration punch 42 and provided with a sufficient counterforce (to maintain the distance), downwards. Only in the last section of this path is the elevation of the base area 22 of the preformed component 20' eliminated, as the material flows mainly via the transition area 26 toward the frame area 24 ( Fig. 4h ). The counterforce of the calibration die base 46 should preferably be selected to be large enough so that the compression of the preformed component 20' can also affect the composite of the calibration punch 42 and the calibration die base 46, without at the same time causing the excess material to collapse into waves.

The flow of the material primarily in the transition area 26 has several advantages. Firstly, the base area 22 of the preformed component 20' essentially retains its shape. Furthermore, the material displacement into the frame area 24 can be selected to be so large that an extension of the frame area can be omitted if necessary. Ultimately, the material flow in the transition area 26 can be used to positively influence the angle of incidence of the frame area 24 to the base area 22.

At the bottom dead center, the 20" component is finally at least partially fully formed and fully calibrated. The upsetting process has thus taken place in a targeted manner and the residual waviness in the base is significantly reduced or even completely eliminated ( Fig. 4i, j ).

Claims (8)

1. A method of manufacturing a component from a steel material or aluminum, the method comprising:

   - preforming a workpiece (20) into a preformed component (10a, 10b 20') having a bottom portion (12, 22), a frame portion (14, 24) and a flange portion, so that the preformed component (10a, 10b 20') has an excess of material for the frame portion (14) and/or the bottom portion (12) and/or the flange portion; and

   - Calibrating the preformed component (10a, 10b 20') to form an at least partially end-formed component (20") with a base portion (22), a frame portion (24) and a flange portion;

   wherein the base portion (12, 22) of the preformed component (10a, 10b 20') essentially has the geometry and/or the local cross-sections of the base portion (22) of the at least partially end-formed component (20"), wherein the excess material is caused by the shape of the transition region (16, 26) between the base portion (12, 22) and the frame portion (14, 24) of the preformed component (10a, 10b 20') and/or by the shape of the transition region between the flange portion and the frame portion of the preformed component,

   characterized in that

   the preforming is carried out in a preforming tool (30) comprising a preforming punch (32), a preforming die (36) and a preforming die bottom (36) movable relative to the preforming die (34), wherein the workpiece (20) is arranged and fixed between the preform punch (32) and the preform die bottom (36) and wherein the workpiece (20) is preformed by a relative movement between the workpiece (20) with the preform punch (32) and the preform die bottom (36) on the one hand and the preform die (34) on the other hand, and that the calibrating is performed by a calibrating tool (40) comprising a calibrating punch (42), a calibration die (44) and a calibration die base (46) movable relative to the calibration die (44), wherein the preformed component (10a, 10b 20') is arranged between the calibration die (42) and the calibration die base (46), and wherein the preformed component (10a, 10b 20') is calibrated by a relative movement between the preformed component (10a, 10b 20') with the calibration die (42) and the calibration die base (46) on the one hand and the calibration die (44) on the other hand.
2. Method according to claim 1, characterized in that the shape of the transition region (16, 26) between the base portion (12, 22) and the frame portion (14, 24) of the preformed component (10a, 10b 20') results in a raised or lowered base portion (12) of the preformed component (10a, 10b 20').
3. Method according to claim 1 or 2, characterized in that the excess material is essentially provided by the transition region (16, 26) between the base portion (12, 22) and the frame portion (14, 24) of the preformed component (10a, 10b 20').
4. Method according to one of claims 1 to 3, characterized in that the shape of the transition region (16, 26) between the base portion (12, 22) and the frame portion (14, 24) of the preformed component (10a, 10b 20') provides an additional length for the base portion (12, 22) and/or the frame portion (14, 24) of the preformed component (10a, 10b 20') when viewed in cross-section.
5. The method according to any one of claims 1 to 4, characterized in that the preforming is performed by a thermoforming-like operation with or without a holddown device (38).
6. Method according to one of claims 1 to 4, characterized in that the preforming is carried out as a combination of at least partially embossing the base portion and raising the frame portion.
7. Method according to claim 1, characterized in that, for calibrating the preformed component (10a, 10b, 20'), calibration die frames (44a, 44b) of the calibration tool (40) defining the frame region (24) of the at least partially end-formed component (20") are moved towards one another.
8. Method according to claim 7, characterized in that the calibration die frames (44a, 44b) of the calibration tool (40) used for calibrating the preformed component (10a, 10b, 20') are designed in such a way that the calibration die frames can preferably be moved in the flange portion of the preformed component.