EP2203264B1 - Method and device for forming a bar stock, bar stock - Google Patents

Abstract

The invention relates to a method and device for forming a bar stock (1), wherein the bar stock (1) with a first diameter (3) is supplied first to a forming tool (2) circulating in the circumferential direction of the bar stock (1). There, the bar stock is reduced to a smaller second diameter (11) by the circulating forming tool (2) and then bent by a deflection device (4) disposed downstream of the forming tool (2), the bar stock (1) being bent in the region of an influence zone (5) of the forming tool (2).

Description

The present invention relates to a method and a device for forming a rod material and a rod material, on the one hand, a reduction of the cross-section takes place and additionally a bending of the rod material is performed.

To bend a rod material, it has hitherto been necessary to introduce the bending moment into the profile by means of corresponding transverse forces with a bending device or machine. This creates a corresponding stress distribution in the cross section, which causes the material of the profile to flow and thus produces a curvature. Since in this process, in particular in the case of thin-walled tubes, the cross section tends to deform, the inner cross section is often supported by a mandrel or a filling. Common methods known for this purpose are three-roll bending and classical tube bending or round bending.

The tube bending processes known today are generally associated with high tooling costs, since the bending tools have to be adapted to the respective workpiece and in particular have to be specially adjusted to the respective pipe diameter. The radii or contours to be bent are each imaged by the tool.

Furthermore, in the known methods, a springback of the bent workpiece must be taken into account in order to compensate for this. This is also very difficult as a result of batch fluctuations of the starting material.

EP 0 148 514 relates to a method and an apparatus for producing pipes and the resulting product. The invention enables the production of bent tubes by cold drawing a hollow tube in one operation with reduction of the outer diameter and the wall thickness by means of a Ausformwerkzeugs and a dome.

US 3,013,652 discloses a method of sliding tubes over a loose plug combined with a mandrel, and bending the tube around a drum.

FR 2 467 644 describes a method for reducing a pipe diameter and a subsequent expansion of the pipe behind a punch by means of a Ausformwerkzeugs.

The object of the invention is therefore to at least partially solve the problems described with reference to the prior art and, in particular, to provide a method and a device by which in particular thin-walled bar materials, such as e.g. Tubes, as well as rod materials with new high-strength materials are simple, accurate and inexpensive formable.

These objects are achieved with a method according to the features of patent claim 1 and with a device according to the features of patent claim 8 and with a rod material according to claim 13. Further advantageous embodiments of the method and the device are specified in the dependent formulated claims. In addition, the features specified in the claims are specified and explained in more detail in the description, wherein further preferred embodiments of the invention are shown.

1. a) Zuführen des Stangenmaterials mit einem ersten Durchmesser zu einem in Umfangsrichtung um das Stangenmaterial umlaufenden Umformwerkzeug,
2. b) Reduzieren des ersten Durchmessers des Stangenmaterials durch das umlaufende Umformwerkzeug hin zu einem kleineren zweiten Durchmesser,
3. c) Biegen des Stangenmaterials durch eine, dem Umformwerkzeug nachgeordnete Ablenkvorrichtung,

wobei das Biegen des Stangenmaterials im Bereich einer Einflusszone des Umformwerkzeugs erfolgt.In the present case, the object is achieved by a method for forming a rod material, comprising at least the following steps:

1. a) feeding the rod material with a first diameter to a circumferentially around the rod material circulating forming tool,
2. b) reducing the first diameter of the rod material by the rotating forming tool to a smaller second diameter,
3. c) bending the bar material through a deflection device arranged downstream of the forming tool,

wherein the bending of the bar material takes place in the region of an influence zone of the forming tool.

By the method claimed here, a bar material can be bent flat (simple) or spatially (complex) with the possibility of simultaneously changing the diameter or thickness of the workpiece along its longitudinal axis during bending. The bar material is secured against twisting during the forming process in particular.

In particular, metallic rod materials are suitable for the method according to the invention, e.g. elongated, closed or open profiles or round bodies, hollow profiles or tubes. Usually, the rod material has a length which is significantly greater than the diameter, in particular with wire-like rod material may possibly also be spoken by an endless profile.

The rod material is fed in a step a) with its first diameter (initial diameter or comparable extent specification) to a forming tool, wherein the forming tool rotates in the circumferential direction around the rod material and in particular unrolls on the outer circumference of the profile. In other words, this also means, for example, that the forming tool exerts forces on a portion of the peripheral surface of the rod material which enable a (uniform) diameter reduction.

In this case, the rod material, in its state still unprocessed by the method, has a first (middle) diameter, which is predetermined by its respective outer contour, which is reduced by the encircling forming tool in a step b).

In principle, a plurality of forming tools can also be arranged one behind the other, in particular coaxially, so that a first diameter of the bar material can be reduced several times, but a single-stage reduction of the diameter is preferred in view of a simple and inexpensive construction of the device.

Optionally, in hollow bodies in addition to the diameter at the same time the wall thickness is changed by the forming tool.

Subordinate to the circulating forming tool (forming process) is a deflection device which allows bending of the bar material (bending process). In this case, the deflection device may be formed as a die, through which the rod material extends. The deflection device can also be used as a pen, as an angle or the like. It is preferred that the bending be carried out with a constant degree of bending during the method proposed here.

The bending of the rod material in step c) takes place in the region of an influence zone of the forming tool, which is characterized by the local plastic deformation of the material of the rod material by the forming tool. As a result of the deformation with concomitant reduction of the diameter or the wall thickness of the rod material by the forming tool, the material of the rod material is locally plastically deformed. Due to the stress state introduced thereby, simultaneous bending is favored, so that in particular only small bending forces are to be used by the deflection device. In other words, the zone of influence characterizes the region of the rod material which is plastically deformed locally at a certain point in time, in which the material thus flows, so that further deformation of the material is possible, for example, by bending with little effort.

Depending on the type of reduction of the diameter, the influence area can be maintained differently in time behind the forming tool, so that the influence range (ie the distance from the plastic deformation to the solidification) can be adjusted by the feed rate and the force of the forming tool.

By the proposed method, a defined solidification can be further introduced into the material of the rod material. By a defined change in the rotational speed of the forming tool to the rod material at a constant feed rate (feed) of the rod material to the forming tool, a different solidification can be introduced at the relevant point in the axial extension of the rod material. The rod material then has at this point without significant geometric changes, in particular without geometric changes, over an increased strength. By means of this embodiment of the method, defined failure zones, for example, can be introduced into a component. This can be important, for example, in the crash behavior of a vehicle.

In a development of the invention, it is proposed that an inner cross-section of a hollow rod material is supported by a mandrel in at least one subregion of the zone of influence of the forming tool. In this case, the (free) inner cross section of the rod material is supported in at least a portion of its inner circumferential surface, so that in a partial region of the influence zone, the hollow rod material is reduced in its inner diameter only so far by the forming tool that it rests on the mandrel at least in a partial region. The mandrel does not extend into the portion of the zone of influence of the forming tool, in which the hollow bar material is already deformed by a bend, so that there is no unwanted overlap between mandrel and bar material as a result of the bend. The mandrel can in particular also be used in several successive forming steps, so that it extends in particular through all these forming steps, which produce an ever further reduced inner diameter of the bar material or obtain a constant inner diameter and reduce only the outer diameter or reduce the wall thickness. Due to the mandrel shape and the axial positioning of the mandrel, the influence of the forming tool on the material can be controlled. Thus, e.g. produced at a position of the mandrel directly under the forming components of the forming tool almost pure compressive stresses and thus a wall thickness reduction can be effected. At a position of the mandrel in front of the forming components of the forming tool, an in-line bending stress can be achieved within the tube wall so that the solidification introduced into the material of the hollow bar stock is reduced.

According to a particularly advantageous development of the method, a bending radius is set in step c) which deviates at most 5%, in particular at most 3%, from a radius of curvature of the bent rod material. In this case, bending radius refers to the radius which is set in method step c), for example by a system operator. In contrast, the mentioned radius of curvature denotes the radius of the bent bar material, the End product can be measured or generated. The radius of curvature is thus greater in particular by the amount of springback than the set bending radius.

The method is also characterized by the fact that this springback due to the bending during the plastic deformation of the material by the forming tool is very low. As a result, a precise bending or an accurate setting of the bending radius is possible, so that it is in particular identical to the final radius of curvature generated. In this case, it is possible to produce radii of curvature which deviate in particular less than 2% and also less than 1% from the bending radius. This error in the estimation of the spring compensation can be avoided and particularly accurate bending processes can be realized.

According to a further expedient embodiment of the method, the forming tool has a rotational speed around the rod material of 50 to 3000 1 / min [revolutions per minute], on. The rotational speed is preferably to be selected in the upper specified range in order to carry out an economic process with acceptable centrifugal forces. In this case, the entire forming tool and / or its (individual) rollers can move at this rotational speed relative to the rod material around.

A particularly fast circumscribing forming tool transfers the material in the zone of influence of the forming tool into a state of stress, in which the material of the bar material is already partly or completely made to flow, so that no high forces are required for the actual bending process and the springback is additionally reduced ,

According to a further embodiment, it is provided that the ratio of bending radius (R _B ) to a second diameter (D ₂ ) lies in a range of 1 to 5 (5 ≥ R _B / D ₂ ≥ 1), preferably in a range of 1 to 3, and more preferably in a range of 1 to 2. This ratio of set bending radius R _B to a second diameter D ₂ , the outer diameter after forming the Bar material is a parameter for the achievable degree of deformation of the bending of the rod material.

Furthermore, it is advantageous that rod material is in particular also machined from high-strength material, e.g. made of heat-resistant steel, TRIP (Transformation Induced Plasticity), dual-phase steel, titanium alloys or aluminum alloys.

According to a further advantageous embodiment, the step b) is performed with varying rotational speed of the forming tool, wherein in particular locally limited portions of the rod material are influenced in terms of material properties, in particular solidified. The rotational speed is significantly varied, in particular by more than 10%, preferably by more than 25% and especially by more than 50% of the present rotational speed. It is preferred that the rotational speed is increased at least once and once lowered, in particular again to an initial value. The change can in particular be made abruptly in order to produce the desired material properties with high selectivity in the individual locally limited subregions. The other parameters, such as delivery of the forming tool in the radial direction, feed of the rod material, etc., can advantageously support this effect and be adjusted accordingly, or varied. For example, failure points of the component can be generated in a targeted and defined manner.

• wenigstens ein in Umfangsrichtung um das Stangenmaterial umlaufendes Umformwerkzeug zur Reduzierung eines ersten Durchmessers des Stangenmaterials hin zu einem kleineren zweiten Durchmesser,
• eine Vorschubeinheit zum Erzeugen eines Vorschubs des Stangenmaterials gegenüber dem umlaufenden Umformwerkzeug und
• eine relativ zum Umformwerkzeug bewegbare Ablenkvorrichtung zum Biegen des Stangenmaterials.

The device according to the invention, to which the invention further relates, is characterized in that it is suitable for forming a bar material comprising

• at least one forming tool circulating circumferentially about the rod material for reducing a first diameter of the rod material to a smaller second diameter,
• a feed unit for generating a feed of the rod material relative to the peripheral forming tool and
• a deflecting device movable relative to the forming tool for bending the bar stock.

The device described here is particularly suitable for carrying out the method also described here according to the invention. Also, therefore, to explain the function or operation of the device to the explanations to the described forming method can be used.

By "device" here on the one hand meant a purpose built for this purpose facility, as well as a tool set, the z. B. can build on turning devices.

For performing a combined forming-bending process, the apparatus comprises a feed unit which either pushes bar stock through the forming tool or pulls it through the forming tool. A combination of these two characteristics is also possible. In addition, the device has (at least one) circumferential forming tool. This forming tool may rotate completely or partially (e.g., individual rolling bodies in contact with the bar stock) around the bar stock. The rotational axis of the forming tool is preferably substantially parallel to the feed direction of the rod material in the region of the forming tool, so that a forming force can act tangentially and radially on the cross section thereof. The deflector, which is downstream of the forming tool in the feed direction, bends the bar stock and for this purpose has an adapted receptacle or guide for the bar stock. It should be pointed out here that if necessary at least two of the units mentioned here (forming tool, feed unit, deflection device) can be combined or integrated with one another.

According to a particularly advantageous embodiment of the device, this has a control which is in particular programmable or makes a direct intervention possible and by which in particular all components of the device can be controlled automatically.

In particular, the deflection device can be positioned by the controller. In this case, "positioning" means in particular a displacement in the three-dimensional space behind the forming tool, as well as a rotation of the deflection device about all three spatial axes. In particular, the position of the deflection device can be controlled and changed during the forming process. Thus, a guide of the still unbent but already formed rod material after the forming tool is possible, so that an additional guidance of the rod material to the deflection is not mandatory.

The control is furthermore particularly suitable for performing at least one of the following functions: to control, regulate or position the feed, the rotational speed of the forming tool and the positioning of the mandrel for supporting an inner cross section.

According to a further advantageous embodiment, the at least one forming tool is a rotating flow-forming tool. In a particularly preferred embodiment, this flow-forming tool has a base body with a recess through which the rod material is passed during the process. Further, a plurality of rollers are arranged on this body, which are rotatable about its own axis, and are in contact with the bar material and thus effect the deformation of the bar material. In this case, at least two but also more (for example 4, 5, 6, 8, 10) rollers can be arranged around the rod material on the base body of the flow-forming tool. The rollers are preferably cylindrical, but this is not mandatory.

The rollers are also regularly driven by themselves. The axes of the rollers are arranged in particular parallel to the axis of rotation of the forming tool.

According to a particularly advantageous embodiment of the flow-forming tool, the rotating flow-forming tool has radially deliverable rollers and the apparatus in particular a controller, in particular for the automated feed of the rollers. The rollers arranged on the main body of the rotating flow-forming tool are radially on the base body of the flow-forming tool deliverable bar stock, or even removable, so that different outer contours and / or degrees of plastic deformation of the rod material can be generated. In particular, the speed of delivery is coupled with the speed of the feed, so that transitions such. B. radii or conicities can be adjusted as desired.

Furthermore, the rolls may have different shapes. They may be conically shaped, cylindrical or spherical and in particular have any other shapes.

According to a further advantageous embodiment of the device, this has a mandrel which at least partially supports an inner cross section of the rod material in at least one subregion of an influence zone of the at least one forming tool. The mandrel is regularly relative to the position of the forming tool relatively movable and can in particular partially immerse in the forming tool.

The rod material according to the invention is produced by the method according to the invention and has at least one failure zone. This failure zone is defined by at least one locally deviating material property of the rod material, which is introduced into the rod material in particular by coordinated process variants. These locally deviating material properties may in particular be present over the entire circumference bounded in the axial direction of extension of the rod material, whereby deviating material properties are present over the entire cross section of the rod material (in comparison to other axial regions). In this case, partial regions of the circumference of an axial bar material section or partial regions of the cross section of the bar material may also have locally differing material properties. In particular, the rod material is made particularly brittle in these areas, so that a failure point is defined by this material property. A material property is, in particular, a mechanical property, possibly at least one of the group: strength, hardness, ductility, microstructure, solidification, degree of deformation, etc.

Fig. 1:

eine Vorrichtung während des Prozesses in perspektivischer Ansicht,

Fig. 2:

eine weitere Vorrichtung während des Prozesses in perspektivischer Ansicht,

Fig. 3:

eine Vorrichtung während des Prozesses in einer Aufsicht,

Fig. 4:

eine weitere Vorrichtung während des Prozesses in einer Aufsicht Und

Fig. 5:

einen Querschnitt durch die Seitenansicht einer Vorrichtung.

The invention and the technical environment will be explained in more detail with reference to FIGS. It should be noted that the figures show, but are not limited to, particularly preferred embodiments of the invention. They show schematically:

Fig. 1:

a device during the process in perspective view,

Fig. 2:

another device during the process in perspective view,

3:

a device during the process in a supervision,

4:

another device during the process in a supervision And

Fig. 5:

a cross-section through the side view of a device.

Fig. 1 shows here the device 13 for combined spin forming and bending of a rod material 1 by a rotating flow-forming tool 16, which is used here as a forming tool 2, with three rollers 17 which are arranged rotatably around the, carried out by the forming tool 2, bar material 1 around. The rod material 1 in this case has a first diameter 3 in front of the forming tool 2 and is pressed by a feed device 14 with a feed 15 through the forming tool 2 therethrough. In this case, the diameter 3 of the rod material 1 is reduced as a result of the forming process by the forming tool 2 to a second diameter 11 after the forming tool 2. As a result of the forming by the rollers 17, the material of the bar material 1 in the zone of influence 5 of the forming tool 2 is partially plastically deformed (outside), so that the bending of the bar material 1 is possible with lower forces.

The deflecting device 4 arranged downstream of the forming tool 2 is set in such a way, optionally by a controller 18, that a bending radius 9 is generated. In this case, this bending radius 9 is entered in the controller 18 or set on the device 13, wherein as a result of the springback of the rod material 1 after bending a radius of curvature 10 occurs in the final product of the rod material 1 produced.

The controller 18 is particularly suitable for a common control of at least feed unit 14, rotational and delivery speed or feed path of the rollers 17, rotational speed of the forming tool 2 and positioning of the deflection device 4. This is in Fig. 1 represented by the dashed connecting lines between the control unit 18 and the individual device components.

Fig. 2 shows a further device 13 in a perspective view, wherein the back of the forming tool 2 is shown with the Walzenachsenaufnahmen 23 in the base body 19. The deflection device 4 is designed as a die, through which the rod material 1 extends. By the forming tool 2, the first diameter 3 of the rod material is reduced to the second diameter 11.

Fig. 3 schematically shows a plan view of the flow-forming die 16, which consists essentially of a base body 19 and, in this case, of three rotatably arranged on the base body 19 rolls 17. Here, the flow-forming tool 16 rotates with its base body 19 and the rollers 17 to the rod material 1, which has a first diameter 3 in the area in front of the forming and in the deformed state after the forming a second diameter 11. The rollers 17 are in this embodiment in a shown conical embodiment whose smaller diameter comes into engagement with the first diameter 3 of the rod material 1 and whose larger diameter generates the deformed second diameter 11 of the rod material 1.

Fig. 4 schematically shows a plan view of a further device 13, with a rolling tool 16, consisting essentially of a base body 19 and arranged on rollers 17, which can perform a feed movement 20 by feed units. During the process, the main body 19 rotate in a first rotational direction 21 about the rod material 1 and the rollers in a second direction of rotation 22, wherein the rollers 17 roll on the circumference of the rod material 1.

Fig. 5 schematically shows a cross section through the device 13, wherein here a hollow bar material 1 is shown, with a first diameter 3 in front of the forming tool 2 and an inner cross section 6 and a corresponding wall thickness 12. The bar material 1 is in the region of the influence zone 5 of the forming tool 2 of the first diameter 3 is reduced to the second diameter 11, wherein a mandrel 7 is inserted at least in a portion 8 of the influence zone 5 of the forming tool 2, so that in this area the bar material 1 is supported with its inner cross section 6 on the mandrel 7. In an axially limited portion of the rod material 1, a failure zone 24 is generated by corresponding change of one or more process parameters.

The present invention is not limited to the illustrated embodiments. Rather, numerous modifications of the invention within the scope of the claims are possible.

reference numeral

1

bar material

2

forming tool

3

First diameter (D ₁ )

4

deflector

5

affected zone

6

Internal cross-section

7

mandrel

8th

subregion

9

Bending radius (R _B )

10

Radius of curvature (R _K )

11

Second diameter (D ₂ )

12

Wall thickness

13

contraption

14

feed unit

15

feed

16

Flow-forming tool

17

roll

18

control

19

body

20

infeed

21

First direction of rotation

22

Second direction of rotation

23

Roll axis recording

24

failure zone

Claims (13)

1. Method for forming a bar stock (1), comprising at least the following steps:

   a) feeding the bar stock (1) having a first diameter (3) to a forming tool (2) rotating in the circumferential direction of the bar stock (1),

   b) reducing the first diameter (3) of the bar stock (1) by means of the rotating forming tool (2) to a smaller, second diameter (11),

   c) bending the bar stock (1) by means of a deflection device (4) disposed downstream of the forming tool (2),

   said bar stock (1) being bent in the region of an influence zone (5) of the forming tool (2).
2. Method according to claim 1, wherein an internal cross-section (6) of a hollow bar stock (1) is supported by a mandrel (7) in at least a partial region (8) of the influence zone (5) of the forming tool (2).
3. Method according to any one of the preceding claims, wherein in step c) a bending radius (9) is set that deviates from a radius of curvature (10) of the bent bar stock (1) by at most 5%, especially by at most 3%.
4. Method according to any one of the preceding claims, wherein the speed at which the forming tool (2) rotates about the bar stock (1) is from 50 to 3000 rpm.
5. Method according to any one of the preceding claims, wherein a ratio of bending radius (9) to a second diameter (11) is in the range from 1 to 5.
6. Method according to any one of the preceding claims, wherein a bar stock (1) is worked which is made of at least one material from the following group: heat-resistant steel, TRIP steel, dual-phase steel, titanium alloys, aluminium alloys.
7. Method according to any one of the preceding claims, wherein step b) is performed at a varying rotational speed of the forming tool (2).
8. Device (13) for forming a bar stock (1), comprising

   - at least one forming tool (2) rotating in the circumferential direction of the bar stock (1), for reducing a first diameter (3) of the bar stock (1),

   - a feed unit (14) for producing a feed (15) of the bar stock (1) towards the rotating forming tool (2), and

   - a deflection device (4) movable relative to the forming tool (2), for bending the bar stock (1).
9. Device (13) according to claim 8, comprising a control (18), especially for automatic positioning of the deflection device (4).
10. Device (13) according to any one of claims 8 and 9, wherein the at least one forming tool (2) is a rotating metal-spinning tool (16).
11. Device (13) according to claim 10, wherein the rotating metal-spinning tool (16) comprises radially advancable rollers (17) and the device (13) comprises, in particular, a control (18), particularly for automatically advancing the rollers (17).
12. Device (13) according to any one of claims 8 to 11, comprising a mandrel (7) which is suitable for, at least partially, supporting an internal cross-section (6) of a hollow bar stock (1) in at least a partial region (8) of an influence zone (5) of the at least one forming tool (2).
13. Bar stock (1), produced by a method according to any one of claims 1 to 7, wherein at least one failure zone (24) is provided which has been produced deliberately and in a defined manner and which is at least one locally deviating material property of the bar stock.

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