EP1710028A1 - Process for manufacturing a bolt shaped high precision body, bolt shaped body and manufacturing apparatus thereof - Google Patents

Abstract

The method is a heat deformation process using a swaging machine by which a stamp (6) with a high stamping speed of around 6000 mm per second is moved against a metal pin (12) situated in and shaped by a bottom die (8). In the reshaping head area the metal pin is heated exclusively for this purpose to a temperature of between 600 to 900[deg] C. A drop hammer (20) is used to produce the stamping speed using gravitational acceleration. A working deformation results which transmits kinetic energy using the stamp onto the metal pin, corresponding to the necessary energy for the deformation process.

Description

The invention relates to a method for producing a highly precise bolt-shaped element with a shank and a hot-formed head and such a bolt-shaped element and a device for producing such a bolt-shaped element. The bolt-shaped element is in particular an ejector pin, a cutting punch, a pre-upsetter, an extrusion punch, a punch or a pinion shaft.

Ejector pin and also cutting punches usually have a cylindrical shaft with an end-side head. The shaft may be formed as a sleeve or solid material. The head is designed, for example, as a cylindrical disk or as a countersunk head. Ejector pins are used in molding tools, such as injection molding tools, to eject the molded component from the mold after the molding operation. When cutting punches the end of the shaft facing away from the head is usually sharp-edged. The cutting punches are used, for example, for punching through sheets. The cutting punches and the ejector pins are made of suitable steels. These are, for example, alloyed cold work steels (WS), hot work steels (WAS) or powder metallurgy produced high speed steels, high alloy cold work steels (HWS), high speed high speed steels (HSS) etc. Especially in the cutting dies, the head serves as an attack element for a restoring force to the punch from the punched hole to withdraw back to the starting position. The same applies to ejector pin, pre-sampler, extrusion punches and punches, which experience an alternating tensile and compressive load on the head during use and pass this on at the transition to the shaft. While with pinion shafts, the torque is transmitted from the gear to the shaft and therefore the transition is to be described as particularly stressed.

The head or the transition between the head and shaft is therefore exposed to high loads. Overall, these elements are high-precision parts whose outer dimensions and material properties may vary only within narrow tolerance limits. The specifications for the cutting punch result, for example, from DIN 9861, ISO 8020, DIN 9844, DIN 9840 and for square / rectangular or profile punch according to DIN 9846. The specifications for ejector pins are determined, for example, according to DIN ISO 6751, DIN ISO 8694, DIN 1530, DIN ISO 8693, DIN ISO 8405 and DIN IOS 6751.

The head of these elements is usually formed by a hot forming process. For this purpose, the shaft is heated to a temperature of about 850 ° to 1300 °, depending on the type of steel in a portion of the head to be formed on forging. Subsequently, with the aid of a die and an associated punch, which is pressed against the heated shaft part, the head is formed by forming. The stamp is driven by a hydraulic cylinder or by an eccentric device. Here, the punch is pressed to a defined end position against the shaft with a substantially constant forming speed, which are in a hydraulic press at about 200 to 500 mm per second and at an eccentric or crank press at 400 to 600 mm per second. As a rule, dimensional inaccuracies, in particular a thickening in the shaft area under the head, which are remedied by post-processing steps, result in these forming methods. In addition, a deterioration of the material properties often occurs. A particular advantage of the hot deformation of the head is the fact that due to the hot forming a "fiber", ie orientations forms in the microstructure, which essentially follows the head geometry. In contrast, in the case of pencils that are produced by a machining operation, such as, for example, piercing or whistling, the fiber progressions are interrupted by the material removal below the head. Overall, this results in an increased risk of breakage and demolition of the head. A disadvantage of hot forming compared to machining is the fact that due to the heat treatment, the material structure in the head area changed is, and thus in the head area other material properties, such as hardness, are present as in the shaft area.

From the DE 16 27 688 is a method for hot deformation of head profiled elements refer. Here, the element is heated by means of an electric heating coil and then formed by pressing into a die by means of a printing unit. From the DE 41 09 407 C2 a device for precision forging can be seen, in which the forming forces are generated by means of a hydraulic piston. Another method for forming a head at the end of a wire pin is from the DE 35 05 251 A1 refer to. In this method, the metal pin is repeatedly compressed by the action of a hammer to form the pin head. Before each upsetting process, the partial area to be reshaped is briefly heated by means of laser irradiation. Between each upsetting operation, a die holding the wire pin through which the wire pin passes is opened and then closed again. Finally, in the US 4,023,225 a method for cold forming a head-profiled element of a high-strength titanium alloy described. During cold forming, forming speeds of between 0.1 and 20 m / sec and more are used.

The present invention has for its object to provide a cost-effective and simple production of such a bolt-shaped element with good mechanical and material properties.

The object is achieved according to the invention by a method for producing a high-precision bolt-shaped element with the features of claim 1. Thereafter, a hot or warm forging is provided for the production of in particular an ejector pin or a punch, pre-plunger, Fließpresstempels, stamp or a pinion shaft at a punch is moved against a metal pin heated in a region to be formed at a high punch speed greater than approximately 3000 mm per second. In particular, the stamp speed with which the stamp at the beginning the forming process is moved against the metal pin, about 5000 to 8000 mm per second.

With the help of the punch, therefore, kinetic energy is transferred to the metal pin. The amount of this kinetic energy depends not only on the speed but also on the size of the accelerated mass. In general, this method sets a speed that is as high as possible under the technical conditions. Depending on the achievable punch speed, the accelerated mass is chosen such that a sufficient kinetic energy is provided for the deformation of the metal pin or steel rod.

It has surprisingly been found that with this very high speed, which is about ten times the achievable in hydraulic or eccentric speeds, significantly improved properties of the manufactured ejector pin or cutting punch can be achieved. In particular, owing to the high forming speed in the region of the head to be formed, there is no or only a slight transformation of the microstructure, so that the hot-formed region has an essentially identical microstructure as the untreated shank region. That the material properties are largely constant over the entire element, similar to an element produced by machining. At the same time, however, the advantage of hot forming, namely the fiber geometry adapted to the head geometry, remains. The special production method described here, namely hot forming with a very high forming speed, therefore advantageously combines the advantages of hot forming with those of machining. Due to this particularly fast forming, very high dimensional accuracy and complex geometries, such as multi-teeth or pinion shafts, can be produced while protecting the material.

In order to allow the simplest possible device design, is to produce the high speed and the necessary force for forming a monkey with a particular variable mass under utilization the gravitational acceleration provided. There are therefore no hydraulic or other drive units used for the movement of the punch. Due to the particular stepless adjustment of the drop height of the drop hammer and preferably stepless adjustability of the mass of the drop hammer, the choice of the punch shape, the female mold, etc., the desired working conditions, such as punch speed when hitting the metal pin, impulse of the impinging punch, kinetic energy, etc ., easily adjusted to the respective application. The settings depend on the selected material of the element to be reshaped, the diameter of the shaft, etc. The speed of 3000 mm per second can be achieved with a monkey already at a drop height of about 0.5 m according to the relationship v = (2gh) ^1/2 . Here h is the height of fall and g is the gravitational acceleration.

In order to allow the most flexible adjustment of the mass of the drop hammer, individual weight plates are combined, which are selected depending on the desired total weight.

Preferably, it is further provided that the head portion of the metal pin is heated to about 600 ° to 900 ° C before the forming process. In contrast to the conventional hot forming processes by means of hydraulic presses or eccentric or crank presses, a temperature well below the otherwise required, material-dependent forging temperature is sufficient. A particular advantage of these low temperatures is the fact that a locally very limited area of the metal pin is subjected to the heat treatment.

According to an expedient development, the heat treatment of the metal pin in the head area to be formed until the beginning of the forming process maintained. By this measure, the metal pin does not need to be "overheated", so that overall a comparatively low temperature is sufficient. Because of the low temperature and the short forming time immediately after the heat input results in almost no forging typical scale layer, which makes the part unsightly, thereby polluting the die and disturbs the forming process. The low temperature is probably decisive for the good microstructural properties even in the heat-treated area. The low temperatures can be realized in particular due to the high forming speed and the resulting high energy input.

According to an expedient development, the high-precision bolt-shaped element already has the finished final state after the hot forming and is not subjected to further aftertreatment. It has surprisingly been found that with the parameters described above, a very high dimensional accuracy is achieved already after the forming process.

The object is also achieved in accordance with the invention by a bolt-shaped element, in particular an ejector pin or a punch, whose material filaments substantially coincide in the hot-formed head region and in the untreated shank region. The material structure in both areas has a substantially equal grain size distribution. Substantially identical material structure or substantially equal grain size distribution is understood here to mean that the structure or the grain size distribution in the shaft area and in the head area coincide within a tolerance range or differ only slightly from one another. For example, the particle size distributions have a deviation <5% and in particular <3%. The same applies advantageously for other material properties, such as hardness. The tolerance range is determined on the one hand by measuring tolerances and on the other hand by manufacturing tolerances.

The object is further achieved according to the invention by an apparatus for producing the high-precision bolt-shaped elements having the features of claim 8. To produce the punch speed, a drop hammer is provided which accelerates the stamp on the high speed by utilizing the acceleration of gravity.

With the monkey, the punch is moved against a die. The device generally comprises a heating element arranged above the matrix for heating the head region of the metal pin to be formed.

Conveniently, the heating element is designed as a fixed annular element whose free interior is dimensioned such that the punch is movable without contact through the free space to the metal pin. The design as a fixed element, the heat treatment can be easily maintained until immediately at the beginning of the forming process. So the heating element does not need to be moved to release the way for the stamp. This also allows high clock rates obtained. Preferably, a high-frequency induction coil is used as the heating element.

Fig. 1

eine teilweise Schnittansicht einer nach Art einer Hammermaschine ausgebildeten Umformvorrichtung mit einem Fallhammer,

Fig. 2

einen Auswerferstift oder Schneidstempel in schematisierter Darstellung,

Fig. 3

eine teilweise Schnittansicht einer alternativen, horizontal ausgerichteten Umformvorrichtung bei der der Stempel mit Hilfe eines schlagartig expandierenden Gases beschleunigt wird und

Fig. 4

eine teilweise Schnittansicht einer weiteren Umformvorrichtung, bei der der Stempel mit Hilfe eines speziellen elektromotorischen Antriebs beschleunigt wird.

An embodiment of the invention will be explained in more detail below with reference to the drawing. In each case, in schematic and greatly simplified representations:

Fig. 1

a partial sectional view of a trained like a hammer machine forming device with a monkey,

Fig. 2

an ejector pin or punch in a schematic representation,

Fig. 3

a partial sectional view of an alternative, horizontally oriented forming device in which the stamp is accelerated by means of a sudden expanding gas and

Fig. 4

a partial sectional view of another forming device in which the stamp is accelerated by means of a special electric motor drive.

In the figures, like-acting parts are provided with the same reference numerals.

The forming devices shown in Figures 1, 2 and 3 each have a guide plate 2, which in the embodiments slidingly on two guide rods 4 very precise, d. H. largely free of play and also possible frictionless. The punch 6 is connected via a punch holder 7 with the guide plate 2 and secured thereto

Opposite to the guide plate 2, a die 8 is provided with a receptacle 10 for a metal pin 12 to be formed. After the forming process, for example, this has the geometry shown in FIG. 2 of a finished ejector pin or cutting punch 14. This comprises a head 14A and a shaft 14B and is usually designed as about its longitudinal axis rotationally symmetrical body with circular cross-sectional area. The receptacle 10 of the die 8 essentially has the geometry of the head 14 A of the cutting punch 14 to be manufactured.

The die 8 is followed by a so-called swaging tower 15, which forms a cylindrical guide for the metal pin 12 and secures it against buckling during the forming process. Opposite to the Stauchturm 15, in turn, a so-called anvil 17 is arranged, which forms a stop for the metal pin 12 to be formed in the axial direction and absorbs the axial forces occurring during the Umformvor. The anvil 17 is expediently adjustable in the axial direction to exactly position the axial length or the axial position of the cutting punch 14 during the forming process.

The forming device further comprises a heating element 16, which is arranged above the receptacle 10. It has a free inner space 18, which is dimensioned such that both the metal pin 12 and the punch 6 can be passed.

In the manufacturing process, the metal pin 12 is first inserted into the receptacle 10. In this case, the pin 12 protrudes beyond the die 8 with a partial region in which the head is formed. For this purpose, for example, a spring bearing, not shown here is provided. With the aid of the heating element 16, which is designed in particular as a high-frequency induction coil, the upper portion of the metal pin 12 is heated in a few seconds to the necessary forming temperature, in particular in the range between 600 ° and 900 ° C. Subsequently, the punch 6 is accelerated to the highest possible punch speed at the beginning of the forming process. Taking into account the stamp speed, the accelerated mass acting on the metal pin 12 is selected such that the kinetic energy transferred to the metal pin 12 corresponds as exactly as possible to the energy required for forming and forming the head region. This necessary energy consists on the one hand of the necessary energy for the plastic deformation as well as the internal energy, d. H. the heat generated in the metal pin 12, together. Over 90% of the kinetic energy used can be converted into heat energy. By the force exerted by the punch 6, the metal pin 12 is first pressed against the anvil 17. Subsequently, the deformation begins to form the head 14A. Thereafter, the formed cutting punch 14 is ejected.

The different forming devices according to FIGS. 2, 3 and 4 differ essentially by the type of acceleration of the punch 6. The preferred embodiment is in this case the according to FIG. 2, in which the forming device is designed in the manner of a hammer machine. In this embodiment can be achieved by a low design effort in a simple manner high punch speeds, which can also be set very accurately. By a precise adjustment of the mass therefore a very precise adjustment of the kinetic energy is possible.

In this embodiment variant, the guide plate 2 forms a base plate 20A of a drop hammer 20, which in the exemplary embodiment has, in addition to the base plate 20A, an additional weight plate 20B. After the heating process, a detent not shown here of the drop hammer 20 is released and the punch 6 is accelerated by the weight of the drop hammer 20 over a drop height h away towards the punch 6 and reached at the height of the die 8 its highest punch speed before the forming process starts.

In the embodiment according to FIG. 3, the forming device as a whole and thus the guide rods 4 are aligned horizontally. The acceleration takes place pneumatically. For this purpose, a pressure cylinder 24 is provided, in which a pneumatic punch 26 is guided displaceably. The pneumatic punch 26 acts on the guide plate 2. The pressure cylinder 24 has an expansion space 28, in which, if necessary in a manner not shown here, a previously compressed gas is introduced for relaxation. The gas is compressed for this purpose, for example, in an accumulator not shown here to a very high pressure and from this pressure accumulator on the need to open a valve in the expansion chamber 28 in this way the pneumatic plunger 26 is accelerated abruptly, so that the total of the punch 6 on the desired high punch speed is accelerated.

In the embodiment according to FIG. 4, the acceleration takes place with the aid of a special electromotive drive 30. This comprises a sliding in the direction of the double arrow and designed in the manner of a drive knob Drive element 32. About the linearly displaceable drive element 32, the guide plate 2 is accelerated.

Both the pneumatic temple 26 and the drive element 32 in this case only touch the guide plate 2 and are not firmly connected thereto. After a predetermined acceleration path, the guide plate 2 is released. By this measure, it is ensured that no longer acts on the guide plate 2 at the latest at the beginning of the forming process of the pneumatic temple 26 and the drive member 32. This ensures, on the one hand, that it is a work-related mode of operation, that is, only the kinetic energy is used for forming, and not the force exerted directly by the electromotive drive 30 or by the pressure cylinder 24 is transmitted to the metal pin 12.

In particular, at high forming energies and this usually high momentum transfers from the punch 6 on the metal pin 12 and the anvil 17 is preferably provided to provide a counter-pulse on the anvil 17 via suitable measures, for example on pneumatic and electromotive path, as indicated by the arrow on Anvil 17 is indicated.

• Der Schneidstempel 14 weist sowohl im Schaft 14B als auch im Kopf 14A ein im Wesentlichen gleiches, homogenes Gefüge mit nahezu identischer Komgrößenverteilung auf. Das Gefüge nach der Wärmebehandlung entspricht daher dem des Ausgangsmaterials.
• Die Härte des Kopfes 14A entspricht im Wesentlichen der Härte des Schafts 14B.
• Es ist bereits eine geringe Umformtemperatur im Bereich zwischen 600° und 900°C ausreichend. Es wird also im Wesentlichen bei dem hier beschriebenen Massivumformen durch Stauchen ein Halbwarmumformverfahren durchgeführt. Dadurch ist die Belastung der Bauteile, also des Schneidstempels 14 sowie auch der Matrize 8, gering gehalten.
• Zwischen dem Aufwärmvorgang des Metallstifts 12 und dem Beginn des Umformvorgangs ist keine Wartezeit vorgesehen, so dass der Metallstift 12 vor Beginn des Umformvorgangs nicht abkühlt. Hierdurch ist kein "Überhitzen" erforderlich.
• Aufgrund der Warmumformung zeigt das Gefüge einen an die Geometrie des Schneidstempels 14 angepassten "Faserverlauf".
• Die aus der Umformvorrichtung ausgeworfenen fertigen Bauteile 14 weisen bereits eine hohe Maßgenauigkeit auf und benötigen keine Nachbehandlungsschritte mehr, es sind daher auch keine weiteren Nachbearbeitungsmaßnahmen vorgesehen.
• Aufgrund der hohen Stempelgeschwindigkeit erfolgt eine vergleichsweise rasche Umformung, so dass bis zur Beendigung des Umformvorgangs nur eine geringe Abkühlung des Metallstifts 12 auftritt. Ganz im Gegenteil wird bei der Umformung die gespeicherte Bewegungsenergie zu nahezu 97% in innere Energie (Temperaturerhöhung) umgewandelt. D. h. das Teil nimmt in der Bearbeitungszeit mehr Energie auf als es an seine Umgebung abgeben kann.
• Aufgrund der Ausgestaltung nach Art einer Hammermaschine erfolgt eine arbeitsgebundene Umformung, d.h. die Umformung ist beendet, sobald die kinetische Energie des Stempels 6 aufgebraucht ist. Im Unterschied zu weggebundenen Maschinen, wie beispielsweise einer Hydraulik- oder Exzenterpresse, bei der der Stempel bis zu einer definierten Endposition unabhängig von der aufzuwendenden Arbeit verstellt wird, wird insbesondere die Matrize 8, der Stauchturm 15, der Amboss 17 sowie die gesamte Maschine weniger beansprucht. Bei den weggebundenen Maschinen besteht nämlich die Gefahr, dass geringfügig überschüssiges Material mit hohem Druck gegen die Wandung der Aufnahme 10 gepresst wird und diese hierbei verformt.
• Aufgrund der niedrigeren Temperaturen, der kurzen Umformzeit und der damit verbundenen hohen Maßhaltigkeit tritt an der Kopfunterseite am Schaft 14B allenfalls eine geringe Schaftverdickung auf, die an sich unerwünscht ist.
• Durch die geringen Temperaturen ist insgesamt ein Material schonendes Herstellungsverfahren mit kurzer Taktzeit ermöglicht.
• Der Einsatz einer Hammermaschine ist eine denkbar einfache Ausführungsform, die kostengünstig, verschleißarm und zuverlässig betrieben werden kann.

The production method described here can in particular achieve the following advantages:

• The cutting punch 14 has a substantially identical, homogenous microstructure with almost identical grain size distribution both in the shank 14B and in the head 14A. The microstructure after the heat treatment therefore corresponds to that of the starting material.
• The hardness of the head 14A substantially corresponds to the hardness of the shaft 14B.
• It is already sufficient for a low forming temperature in the range between 600 ° and 900 ° C. Thus, essentially, in the case of massive forming by upsetting as described herein, it becomes a warm forging process carried out. As a result, the load on the components, so the cutting punch 14 and the die 8, kept low.
• Between the warm-up of the metal pin 12 and the beginning of the forming process no waiting time is provided, so that the metal pin 12 does not cool before the beginning of the forming process. As a result, no "overheating" is required.
• Due to the hot forming, the microstructure exhibits a "fiber course" adapted to the geometry of the cutting punch 14.
• The ejected from the forming finished components 14 already have a high dimensional accuracy and do not require any post-treatment steps more, so there are no further post-processing measures provided.
• Due to the high punch speed, a comparatively rapid transformation takes place, so that only a slight cooling of the metal pin 12 occurs until the completion of the forming process. On the contrary, during the transformation, the stored kinetic energy is converted into almost 97% internal energy (temperature increase). Ie. the part consumes more energy during processing than it can deliver to its environment.
• Due to the design in the manner of a hammer machine is a work-related deformation, ie the transformation is completed when the kinetic energy of the punch 6 is used up. In contrast to weggebundenen machines, such as a hydraulic or eccentric press, in which the stamp is adjusted to a defined end position regardless of the work to be expended, in particular the die 8, the stump 15, the anvil 17 and the entire machine is less stressed , In the case of the machines tied away, there is the risk that excess material will be pressed against the wall of the receptacle 10 at high pressure, thereby deforming it.
• Due to the lower temperatures, the short forming time and the associated high dimensional stability occurs at the top of the head on Shaft 14B at most a small shaft thickening, which is undesirable in itself.
• Due to the low temperatures, a material-friendly production process with a short cycle time is made possible overall.
• The use of a hammer machine is a very simple embodiment that can be operated cost-effectively, wear and reliable.

The method described here for hot and warm forging with the high punch speed and the particularly good metering of the force acting on the forming area by the punch, in particular with the low forming temperatures, can be used in particular for the production of ejector pins or Schneidstempein. In particular, this method also allows the production of such elements with a small diameter of, for example, only 0.5 mm easily and fully automatically with high dimensional accuracy. Due to the achievable with this method high dimensional accuracy combined with very good structural properties of this method is used in particular for the production of high-precision components, for example for medical technology and in particular for the production of gears or pinion shafts. In pinion shafts, the head 14A is formed in the manner of a gear or a pinion. Overall, high-precision forgings can be produced with the method described here.

Decisive in the present method is the high Stempeigeschwindigkeit. In the embodiment, a hammer machine is used to achieve the high punch speed. In principle, these high speeds can be achieved, for example, with pneumatic drives or electric actuators. With the use of very large masses for the impact hammer 20 and at high speeds, it is advantageous due to the then high pulse input, if a counter-pulse is generated in a suitable manner to compensate for the pulse input.

LIST OF REFERENCE NUMBERS

2

guide plate

4

guide rod

6

stamp

7

punch holder

8th

die

10

admission

12

metal pin

14

cutting punch

14A

head

14B

shaft

15

Stauch tower

16

heating element

17

anvil

18

free interior

20

monkeys

20A

baseplate

20B

weight plate

24

pressure cylinder

26

pneumatic rams

28

expansion space

30

electric motor drive

32

driving element

Claims (10)

Method for producing a high-precision bolt-shaped element (14) having a shank (14B) and a hot-formed head (14A), in which a metal pin (12) to be formed is inserted into a die (8), the metal pin (12) is heated in a region to be reshaped and in which the metal pin (12) is reshaped by means of a punch (6) and the die (8) to form the head (14A),
characterized,
that the punch (6) is moved against the metal pin (12) at the beginning of the forming process at a punch speed greater than approximately 3000 mm / s, in particular with a punch speed in the range of approximately 5000 to 8000 mm / s,
in that a drop hammer (20) is used to generate the punch speed using the gravitational acceleration, and
that a work-related deformation takes place and with the punch (6) on the metal pin (12) transmitted kinetic energy is adjusted so that it corresponds to the energy necessary for the forming process. Method according to Claim 1, in which the mass of the drop hammer (20) can be adjusted and for this purpose individual weight plates (20B) which can be combined with one another are used. Method according to one of the preceding claims, in which the area of the metal pin (12) to be reshaped is heated to approximately 600 ° to 900 ° C. Method according to one of the preceding claims, in which the heat treatment of the metal pin (12) in the head region is maintained until the beginning of the forming process. Method according to one of the preceding claims, in which the high-precision bolt-shaped element already has the finished final state after hot working and is not subjected to any further aftertreatment. A bolt-shaped member having a shank (14B) and a hot-formed head (14A) made according to any one of the preceding claims, the material texture of which substantially matches the hot-formed head portion and the untreated shank portion. Element according to claim 6, which has substantially the same hardness after hot forming in the head region as in the shaft region. Apparatus for carrying out the method according to one of claims 1 to 5, with at least one vertically oriented guide element (4) a drop hammer (20) mounted on the guide element (4) and on which a punch (6) is arranged, - A die (8) for receiving a reshaping metal pin (12), which is arranged at the lower end of the guide member with - A heating element (16) which is arranged above the die (8) for heating a reshaped head portion of the metal pin (12), wherein - A drop height (h) of the drop hammer (20) is set such that the punch is accelerated to a punch speed, which is greater than about 3000 mm / s at the beginning of the forming operation and in particular in the range of about 5000 to 8000 mm / s and - The mass of the drop hammer (20) is set such that a work-related deformation takes place and the kinetic energy corresponds to the energy required for the forming. Apparatus according to claim 8, wherein the mass and / or drop height (h) of the drop hammer (20) are variable. Apparatus according to claim 8 or 9, wherein the heating element (16) is designed as a fixed annular element whose free interior (18) is dimensioned such that the punch (6) contactlessly through the free inner space (18) to the metal pin (12). is movable.

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