EP3700692B1 - Multistage press and method for producing a formed part - Google Patents

Description

The invention relates to a multi-stage press for massive forming of a wire section according to the preamble of claim 1. The invention also relates to a method for producing a formed part, in particular a screw, with a multi-stage press according to claim 7 the EP 0 215 338 A1 , CH 346 749 A , which forms the basis for the preamble of claim 1, JP 3 793953 B2 as well as the GB 707 092 A known. A straightened wire is fed from the coil into the machine, where a defined wire section is cut to length. The wire section is conveyed via a gripper of a transfer device to a first forming stage, formed from a die and a punch, where it is positioned in a receptacle of the punch. The wire section is then pushed into the die over the punch and deformed. After the deformation, the deformed piece of wire is positioned in a further gripper of the transport device by means of an ejector pin and transported via this to the next deformation stage. The punches of the forming tools arranged one behind the other are regularly arranged on a common horizontal cylinder, so that a wire section is deformed per advance of this cylinder in each of the forming stages. The wire section is formed into the finished workpiece via the forming steps arranged one behind the other. In the last forming stage, the finished part is ejected. Common multi-stage presses have six forming stages.

A wide variety of cold-formed parts such as screws or bolts can be produced by means of a multi-stage press of the aforementioned type. A high process speed can be achieved via the forming steps arranged one behind the other, since six wire sections can be formed with each advance of the cylinder. Forming is problematic with special materials, such as heat-resistant nickel-based alloys (e.g. NI 53 / FE19 / CR19 / NB / MO / TI). To manufacture screws from this material, it is necessary to remove the area of the screw head in front of it Heat forming up to 1000 ° C. It must be taken into account that the screw shank must remain cold, otherwise the quality of the thread to be subsequently introduced into the screw shank would be the result. To produce such special screws, blanks are first produced from wire sections, in which an end section is formed into a screw head with prior heating. These blanks are then fed piece by piece to a multi-stage press for producing the desired screw.

The disadvantage of the previously known manufacturing method for such special screws is that it is very complex. In addition, an individual adjustment of the screw length or dimension is only possible with great effort, since the corresponding blanks must first be created for this.

The invention aims to provide a remedy here. The invention is based on the object of providing a multi-stage press for the massive forming of a wire section, which also enables the production of special screws of the aforementioned type directly from wire coils. According to the invention, this object is achieved by a multi-stage press with the features of claim 1.

The invention provides a multi-stage press for the massive forming of a wire section, which also enables the production of special screws of the aforementioned type directly from a wire made of heat-resistant nickel alloy. The fact that means for partial heating of a wire section are arranged on the side of the cutting device opposite the wire feed means that a defined end-side wire section can be heated for the subsequent shaping of the screw head, with the wire being able to be cut to a desired length after the end-side wire section has been heated before it is transported to the first deformation stage via the transfer device. Because the wire feed, the forming stages (or the cylinder driving the stamps of the forming stages) and the cutting device can be controlled independently of one another A real-time deformation of a wire section heated at the end and then cut to length is enabled over all deformation stages while the next end section is heated at the same time.

In this case, the means for heating a wire section comprise an induction coil, the wire feed being set up for the temporary introduction of a wire section into the induction coil. This enables a defined temperature of an end wire section to be set. The temperature of the wire section results from the power output by the induction coil and the length of time the wire section remains in the induction coil.

The wire feed includes a servo drive for a defined forward and backward movement of a wire section. This enables the wire to be fed from the coil precisely and as required. The possibility of the defined forward and backward movement of the wire enables the end of the wire to be introduced into the induction coil as well as a subsequent return movement of the wire to determine the wire section to be cut to length.

In a further embodiment of the invention, the wire feed can be controlled via a control connected to it, in which a defined dwell time of a wire section in the induction coil and / or a target temperature can be stored. In this case, means for detecting the temperature of a wire section located in the induction coil are preferably arranged, which are connected to the controller, a control being integrated into the controller by which the wire feed can be controlled as a function of the temperature of the wire section. Alternatively, it is also possible to empirically determine dwell times to achieve the desired temperatures, which are stored in the control.

In a further development of the invention, the control is connected to the cutting device and set up in such a way that after partial heating has taken place at the end a wire section which is cut to length in a defined length.

As a result, the length of the screws to be produced can be individually adjusted.

The present invention is also based on the object of providing a method for producing a special screw of the aforementioned type with a multi-stage press directly from the coil. According to the invention, this object is achieved by a method having the features of claim 5.

The fact that a wire is first heated at the end, then a wire section is cut to length at a defined distance from the heated end and the partially heated wire section obtained in this way is successively fed to several forming stages via a transfer device, enables the length of the screw produced to be individually adjusted. The wire is fed from a coil via a wire feed to an induction coil, where it is heated to a defined temperature at the end.

The wire is fed to the induction coil via a servo drive, whereby the wire is fed into the induction coil according to the desired length of the end area to be heated and, after reaching the desired temperature or the required dwell time, is moved out of the induction coil again, after which a wire section is desired Length is cut to length. This enables precise process control for the production of screws of different lengths from a coil.

In an embodiment of the invention, the temperature of the end region of the wire is measured using a contactless temperature sensor, in particular a pyrometer or also using an infrared measuring device. This further improves the accuracy of the process control. Alternatively, the required dwell time to achieve the desired temperature inside the induction coil can also be determined empirically and stored in a controller connected to the servo drive. That way is the creation of a database with dwell times assigned to corresponding target temperatures in the manner of an expert system is also conceivable.

Figur 1

die schematische Teildarstellung einer Mehrstufenpresse mit angeordneter Induktionsspule zur endseitigen Drahterwärmung;

Figur 2

die schematische Darstellung der Anordnung von Drahtzuführung, Ablängvorrichtung und Induktionsspule zur Herstellung eines endseitig erwärmten Drahtabschnitts innerhalb der Mehrstufenpresse aus Figur 1 in den Betriebszuständen:

1. a) Vorschub des Drahts vom Coil;
2. b) Erwärmung des endseitigen Drahtabschnitts in der Induktionsspule;
3. c) Zurückbewegung des Drahtes mit Einstellung der gewünschten Länge und
4. d) Ablängen des Drahtabschnitts in der gewünschten Länge mit Übernahme durch die Transfereinrichtung.

Other developments and refinements of the invention are specified in the remaining subclaims. An embodiment of the invention is shown in the drawings and is described in detail below. Show it:

Figure 1

the schematic partial representation of a multi-stage press with arranged induction coil for end-side wire heating;

Figure 2

the schematic representation of the arrangement of wire feed, cutting device and induction coil for the production of a wire section heated at the end within the multi-stage press Figure 1 in the operating states:

1. a) feeding the wire from the coil;
2. b) heating the end-side wire section in the induction coil;
3. c) Moving the wire back with setting the desired length and
4. d) Cutting the wire section to the desired length and taking it over by the transfer device.

The horizontal multi-stage press 1 chosen as an exemplary embodiment is a horizontal multi-stage press, such as is used for the production of screws and similar small parts. The structure of such horizontal multistage presses is well known to the person skilled in the art and, for example, in US Pat EP 0 215 338 A1 described. The forming tools are arranged next to one another. A cross transfer device brings the workpieces from forming stage to forming stage. These presses usually work with a transverse transport slide, which has a number of transfer grippers corresponding to the number of forming stages, which protrude between the stamping tools and the dies. A detailed description of such a horizontal multi-stage press is therefore not provided at this point. The following Description focuses on the essential components of the multi-stage press according to the invention.

In Figure 1 a multi-stage press 1 according to the invention is shown in detail. The die block 11 can be seen with individual deformation stages 12, between which transfer grippers 71 of the transverse transfer device 7 are arranged. A wire feed, which is designed as a servo drive 2 in the exemplary embodiment, is arranged in front of the first forming stage 12. The wire feed 2 receives a wire 8 unwound from a coil (not shown). A separately controllable wire cutter 3 for cutting the wire 8 to length is arranged in front of the wire feed 2. Seen from the wire feed 2 behind the wire shears 3, the transfer grippers 71 of the transfer device 7 are positioned, which are set up to receive a wire section 81 cut to length by the wire shears 3. Again behind the transfer grippers 71, an induction coil 4 is arranged, which is positioned such that a wire picked up by the wire guide 2 can be pushed into the induction coil 4 via the servo drive 21. The wire feed 2, the wire cutters 3 and the induction coil 4 are connected to a control and regulating device 6, which in turn is connected to a pyrometer 5 arranged on the induction coil 4 for measuring the temperature of a wire end section 82 introduced into the induction coil 4. In addition, the control and regulating device 6 is also connected to the transverse transfer device 7 for controlling the transfer gripper 71. The control and regulating device 6 is part of the overall machine control - not shown - via which the control of the stamp block - not shown - carrying the individual forming stamps takes place.

In Figure 2 the process for the production of a high-temperature-resistant screw by forming a wire made of a nickel-based alloy is outlined. A wire 8 is advanced from the coil (not shown) via the wire feed 2 through the wire cutters to the induction coil 4 until a wire end section 82 of a defined length protrudes into the induction coil 4. The length of the wire end portion 82 to be heated as well as the desired For this purpose, the temperature is stored in the control and regulation device 6, which also controls the servo drive 21 of the wire feeder 2 ( Figure 2a ). The servo drive 21 is then stopped so that the wire end section 82 remains in the induction coil 4. The temperature of the wire end section 82 is measured continuously via the pyrometer 5. The measured values are reported to the control and regulating device 6, which compares them with the stored target temperature of the wire end section 82 ( Figure 2b ).

After the setpoint temperature of the wire end section 82 has been reached, the servo drive 21 of the wire feeder 2 is controlled in the opposite direction via the control and regulation devices 6, so that the wire 8 is withdrawn through the wire feeder 2 until the wire section 71 located behind the wire cutter 3 the has reached the length stored in the control and regulating device 6 ( Figure 2c ). The wire cutter 3 is now actuated via the control and regulating device 6, as a result of which the wire section 81 is cut to the stored length. The wire section 81 cut to length in this way is picked up by the gripper 71 of the transfer device 7 and transferred to the first forming stage 12 of the die block 11 of the multi-stage press 1. At the same time, the wire 8 is advanced again in the direction of the induction coil 4 until the wire end section 82 again protrudes into the induction coil 4 in the desired length. During the heating of this next wire end section 82, the further deformation of the wire section 81 takes place via the further deformation stages 12. The further deformation of the end-heated wire section 81 inserted in the first deformation stage 12 via the deformation steps 12 of the multi-stage press is known to the person skilled in the art and is required Do not provide any further explanation.

At this point it should be noted that the drive of the punch block (not shown), which receives the individual forming punches, is mechanically decoupled from the servo drive of the wire feed 2 and also from the drive of the transverse transfer device 7. It should also be mentioned that the multi-stage press according to the invention can be used both for the conventional production of formed parts by means of a continuous cold forming process. For this the wire 8 is immediately advanced so far that a wire section 81 of the desired length is arranged behind the wire cutters 3, after which this wire section 81 is immediately cut to length.

Claims (7)

1. Multistage press for massive forming of a wire section comprising a wire feed with an arranged cutting-to-length device as well as a transfer device having grippers for receiving a wire section cut to length and for transfer of this section to subsequent forming stages, wherein the wire feed (2), the forming stages (12) and the cutting-to-length device (3) can be controlled independently from one another, characterised in that on the side of the cutting-to-length device (3) opposite the wire feed (2) means for partial heating of a wire section (81) are arranged, wherein the means for partial heating of a wire section (81) comprise an induction coil (4), wherein the wire feed (2) is set up for the temporary introduction of a wire section (81) into the induction coil (4) and the wire feed (2) comprises a servo drive (21) for defined forward and backward movement of a wire section.
2. Multistage press according to claim 1, characterised in that the wire feed (2) can be controlled via a control (6) connected thereto, in which a defined dwell time of a wire end section (82) in the induction coil and/or a target temperature can be stored.
3. Multistage press according to claim 2, characterised in that means for detecting the temperature of a wire end section (82) situated in the induction coil (4) are arranged, which means are connected to the control (6), wherein a regulator is integrated into the control (6), by means of which the wire feed (2) can be controlled as a function of the temperature of the wire end section (82).
4. Multistage press according to claim 2 or 3, characterised in that the control (6) is connected to the cutting-to-length device (3) and is set up in such a manner that after partial heating of the end of a wire section (81) has taken place, this section is cut to a defined length.
5. Method for producing a formed part, in particular a screw, using a multistage press, wherein, first, a wire (8) is heated at the end, wherein the wire (8) is fed from a coil via a wire feed (2) to an induction coil (4), where it is heated to a defined temperature at the end side on a wire end section (82), wherein the wire (8) is fed to the induction coil (4) via a servo drive (21), wherein the wire (8) is moved into the induction coil (4) in accordance with the desired length of the wire end section (82) to be heated and, after the desired temperature is reached, i.e.after the dwell time required for this purpose, it is moved out of the induction coil (4) again, subsequently, a wire section (81) of the desired length is cut to length at a defined distance from the heated wire end section (82) and the partially heated wire section (81) thus achieved is successively fed to several forming stages (12) via a transfer device (7).
6. Method according to claim 5, characterised in that the temperature of the wire end section (82) is measured via a non-contact temperature sensor, in particular a pyrometer (5).
7. Method according to claim 5, characterised in that the dwell time required to achieve the desired temperature within the induction coil (4) is determined empirically and stored in a control (6) connected to the servo drive (21).

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