BE1025471B1 - Process for the preparation of an active element and corresponding active element - Google Patents

Abstract

Shown and described is method for producing an active element (1) with an internal thread (2), wherein a tool blank (3) is machined in at least one forming step, and wherein the tool blank (3) in at least one thread forming step with an internal thread (2) becomes. By the method, the production time is thereby reduced, so that the productivity can be increased, in particular in the machining of active elements that the internal thread (2) in the thread-forming step as a section thread (4) with threaded portions (5) is formed, wherein the internal thread (2 ) has no fully rotating turns (6).

Description

Method for producing an active element and corresponding active element

The invention relates to a method for producing an active element with an internal thread, wherein a tool blank is machined in at least one forming step and the tool blank is equipped with an internal thread in at least one thread production step. In addition, the invention relates to an active element for producing a semifinished product or end product from a metal sheet, with a shaped section for shaping the semifinished product or end product and with a fastening section, the fastening section having at least one internal thread.

Active elements have been known for many years in different design variants and for different applications, for example in forming, stamping or embossing processes. In general, plastic materials (metals and thermoplastics) are deliberately brought into a different shape without removing material from the raw parts. The material maintains its mass and cohesion. In contrast, when separating, such as in punching processes, or when joining, the mass and the cohesion are reduced or increased. Forming, cutting and joining are particularly important in the metal industry, especially in the sheet metal processing industry (e.g. in body construction) and in casting technology, in plastics processing (e.g. in injection molding) and in some areas of the craft (e.g. in forging). Active elements play a central role in many areas of the manufacturing and processing industry. Only with the help of these active elements, which are installed in the corresponding machines, is it possible to machine a raw material in such a way that it meets the desired requirements.

For this reason, special demands are made on active elements or on the production of active elements. As a rule, high-quality steels are used for this, so that a sufficiently good surface quality, especially at the cutting edges, can be achieved. For this purpose, a tool blank made of metal or a sintered ceramic material is used for further processing.

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EP 1 321 202 B1 shows, for example, a method for producing a forming tool. First of all, a component blank is introduced between the tool parts of an internal high-pressure forming tool. The internal high-pressure forming tool is closed and the component blank is formed into a forming tool using a pressure medium. In a next step, a through opening is then punched out in a wall of the forming tool. Then, in a third step, an internal thread is produced in the through opening.

The internal thread is usually used to attach the newly formed forming tool to a machine element. It can thus be screwed onto the machine element in a simple manner. The internal thread is incorporated in the state of the art by further tools.

EP 1 540 207 B1 discloses a method for producing a spindle nut of a ball screw drive. A punching tool with a punch is used. The punching tool additionally comprises a thread dome, the punch being arranged radially displaceably in the thread dome. The punch can be moved radially outward from the thread dome. Different process steps can thus be carried out in succession in order to produce the spindle nut.

For the production of active elements, methods are known from the prior art in which at least three process steps are required. The starting point is a prefabricated base plate, which consists of a hardened, heat-treated metal, in particular steel, and from which the basic shape of the active element is cut out by means of shaping. The workpiece is then spun around so that a hole can be made in the workpiece in a second manufacturing step. In a subsequent third production step, a thread is then cut into the bore, for which purpose at least a new tool change is required.

A disadvantage of the methods known from the prior art is that many different steps are necessary to produce the corresponding component. As a result, the production process is time-consuming and the production of an active element is therefore relatively expensive.

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The present invention is therefore based on the object of specifying a method for producing an active element, by means of which the production time is reduced, so that productivity can be increased, in particular in the mechanical production of active elements.

This object is achieved in the method mentioned at the outset according to claim 1 in that the internal thread is formed in the thread production step as a section thread with thread sections, so that the internal thread has no fully revolving turns. In the context of the present invention, a section thread is understood to be a thread in which the course of the turns is partially interrupted. The thread partially has recesses, or the thread profile is partially interrupted in some other way. The recesses or interruptions extend in the tangential direction.

The method according to the invention is initially characterized in that, by forming a section thread, it is not necessary to form or cut the thread in a previously formed bore. The section thread can thus also be formed independently of rotating tools such as thread formers, thread cutting tools or tools that are used, for example, when drilling or milling.

In a preferred embodiment of the method according to the invention it is therefore provided that the forming step and the thread production step are carried out in a common work step. Since the formation of the section thread is not limited to conventional thread forming or thread cutting, it is also not necessary for the tool blank to be reclamped for the drilling of an opening and the subsequent formation of the internal thread. In this way, the active element can be shaped and provided with an internal thread without the production process having to be interrupted. In a preferred embodiment of the method it is therefore provided that the shaping and the formation of the internal thread are implemented in a program sequence of a production machine without the process having to be interrupted by reclamping the tool blank.

An advantage of this configuration is therefore that significant time savings are achieved compared to methods known from the prior art

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BE2017 / 5558 will. Previously, three steps were necessary to produce an active element with an internal thread. To do this, the contour of the active element had to be formed first. After reclamping the tool blank, a hole had to be drilled and a thread subsequently formed. In the method claimed here, the last steps can be omitted and the entire contour of the active element, including the section thread, can be manufactured in one work step. Another advantage is that not only the overall manufacturing time but also the throughput time is significantly improved. The fact that only one work step is required for production eliminates waiting times for other equipment such as B- on a milling machine.

In a further embodiment of the method, it is advantageously provided that the shaping step is carried out by means of spark erosion. Spark erosion is a thermal, ablative manufacturing process for conductive materials that is based on electrical discharge processes (sparks) between an electrode (tool) and a conductive workpiece. The electrode tool is brought to the workpiece in such a narrow gap (for example 0.004-0.5 mm) until a spark strikes, which melts and evaporates the material in a punctiform manner. Depending on the intensity, frequency, duration, length, gap width and polarity of the discharges, the different removal results arise. Even complex geometric shapes can be produced using spark erosion. There are different variants that come into question for the claimed method. A distinction is made between EDM drilling (EDM drilling), EDM cutting (wire EDM), in which a wire forms the electrode, and EDM sinking (EDM sinking), in which the electrode is moved into the workpiece as a negative form with the help of an EDM machine.

To simplify the method, a further advantageous embodiment of the method provides that the thread production step is also carried out by means of spark erosion. In this way it is possible for both steps, that is to say the forming step and the thread production step, to be carried out using the same method. This further simplifies the sequence of the method, since two different machining steps are not carried out on a clamped tool blank. By spark eroding as a common step

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BE2017 / 5558 the forming step and the threading step can be carried out one after the other.

In order to simplify the procedure, a further preferred embodiment of the method provides for spark eroding to be carried out using the wire eroding method. Sparks are generated in a sequence of electrical voltage pulses, which transfer the material from the tool blank (anode) to a continuous thin wire (cathode) and into the separating medium, the dielectric. The eroding wire is wound on a spool and is guided from there via deflection rollers and the brake roller to the upper wire guide. Two opposite drive rollers pull the wire through the workpiece and through the lower wire guide at a defined wire tension and speed and then dispose of it. Usual wire tensions are in the range from 5 to 25 Newtons and usual wire speeds in the range up to 25 m / min. The wire guides above and below the workpiece guide and support the wire and serve to suppress vibrations. The wire guides also serve to have a defined deflection point. Wire EDM has the advantage that it can be carried out automatically. A tool blank therefore only has to be clamped once in the machine and can then be removed as a finished active element.

Because the internal thread is designed as a section thread in the thread production step, the internal thread has no fully revolving turns. The radius of these arcs therefore does not necessarily have to be less than half the thickness of the active element, as is absolutely the case with a fully rotating thread. Each threaded section can describe an arc of a circle, the radius of which is larger or even significantly larger than half the thickness of the active element. The internal thread thus produced then has a diameter that is greater than the thickness of the active element. As usual for threads, the section thread has a thread pitch, that is to say the distance, measured parallel to the axis, of two adjacent, rectified thread flanks of the same thread. The thread pitch indicates how many millimeters a screw is inserted into the section thread when it is tightened by one turn. In the method, the production of the thread pitch of the section thread is freely adjustable. When wire EDM

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BE2017 / 5558, this can be adjusted accordingly, for example, by crossing the axes.

The above-mentioned object is achieved in the case of an active element described at the outset with a shaped section and with a fastening section with the features of patent claim 7 in that the internal thread is designed as a section thread with threaded sections, so that the internal thread does not have any all-round turns. A section thread is also to be understood here that the course of the turns is partially interrupted in the circumferential direction.

The active element is preferably produced by the previously described method. In order to be able to manufacture the active element more quickly and easily, it is provided in a preferred embodiment that the individual turns or turn sections of the threaded sections each describe an arc, and that the radius R of the circular arcs is greater than half the thickness of the active element. Since the internal thread does not have all-round turns, the turn sections of the threaded sections are not connected to one another, so that a recess is formed between the threaded sections. The recess extends in the axial direction, so that the threaded sections extend in the axial direction without being connected to one another. Due to the resulting gaps in the internal thread, each threaded section can describe an arc of a circle, the radius of which is significantly larger than half the thickness of the active element. The radius of the threaded sections and thus also the diameter of the internal thread is therefore largely independent of the thickness of the active element.

In a further embodiment of the active element, it is preferably provided that the internal thread has two threaded sections which are arranged opposite one another. This ensures in a simple manner that a screw can be screwed into the machine to secure the active element. In practice, the active element can be inserted into a recess on the tool side of the corresponding machine and fixed on the other side by a screw which can be screwed into the internal thread through the recess on the other side. The fact that only two mutually opposite, non-interconnected threaded sections are provided expands the

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Thread sections when screwing in a screw in the radial direction. In this way, the active element is additionally secured in the machine, since the active element is connected to the machine even more by the spreading. The two leg-like threaded sections are pressed against the wall of the recess by the screw used.

In order to be able to better screw a screw to the internal thread, it is preferably provided that the overlap angle between a screw to be screwed in and a threaded section describing a circular arc is between 45 ° and 90 °, preferably between 60 ° and 80 °, particularly preferably between 70 ° and 75 ° lies. In this way, the angle is small enough that the production of the active element can be carried out easily by the method described above. The angle is also large enough so that a screw screwed into the thread is held securely in the active element. In order to increase the load-bearing component of a screw screwed into the section thread and thus also the pull-out forces, it can also be provided in this connection that the core diameter of the section thread, that is to say the distance between two opposite turns of the thread sections, is reduced by about 0.1 mm in each case is. Despite this measure, the function of the screw is unrestricted.

In order to further simplify the manufacture of the active element, it is provided in a further embodiment of the invention that the threaded sections are flat in the tangential direction, so that the radius R of the circular arc described is substantially greater than half the thickness of the active element. The threaded sections can be designed so that the radius of the arcs goes towards infinity. The production of the active element is simplified in that only very slightly curved or even no curved surfaces have to be produced.

In particular, there are several options for designing and developing the method according to the invention and the active element according to the invention. For this purpose, reference is made both to the claims subordinate to claims 1 and 7 and to the following description of a preferred embodiment in conjunction with the drawing. Show in the drawing

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Fig. 1 2 shows a plan view of an exemplary embodiment of an active element, Fig. 2 1 from the front (from the direction II in Fig. 1), Fig. 3 another embodiment of an active element from the front (from the direction II in Fig. 1), Fig. 4 a perspective view of the active element during manufacture and Fig. 5 a longitudinal section through an embodiment of an active element fastened in a machine. 1 shows a top view of an active element 1 using the example of a bending punch. The active element 1 with the internal thread 2 is produced from a tool blank 3 (FIG. 4) by means of wire EDM. It is

Internal thread 2 is designed as a section thread 4, so that the introduction of a hole and a subsequent thread forming or cutting are not necessary. The section thread 4 has a plurality of turns 6, which, however, are not designed to run all the way round. The section thread 4 is divided in this embodiment into two separate thread sections 5.

Overall, the active element 1 can be divided into a shaped section 7 and a fastening section 8. The internal thread 2 is arranged on the fastening section 8 so that the active element 1 can be fastened to a machine by means of a screw. The shaped section 7 has a straight edge surface 9, which serves as a support for the active element 1 designed as a bending punch on a workpiece to be machined. In a bending process, for example in the mechanical folding of metal parts, the active element 1 is fastened to the fastening section 8 on the machine, whereas the shaped section 7 is oriented in the direction of the workpiece that is to be machined.

The active element 1 is made from a prefabricated base plate or eroding plate. Therefore, the basic shape of the active element 1 shown is largely cuboid with rounded edges. In the longitudinal extent of this cuboid shape, the internal thread 2 is on the opposite side

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BE2017 / 5558 introduced the straight edge surface 9 in the active element 1. The two threaded sections 5 are arranged opposite one another, so that the threaded sections 5 are arranged on two side surfaces of the active element 1 and a recess 10 is formed between the threaded sections 5, so that the active element 1 has a U-shape overall. The shaped section 7 is to be regarded as a U-back, whereas the U-legs are formed by the threaded sections 5.

FIG. 2 shows the active element 1 according to FIG. 1 from the front, from the direction marked II in FIG. 1. The view of the fastening section 8 or into the section thread 4 is shown. The two thread sections 5 formed as U-legs and the windings 6 of the section thread 4 can be seen. The thread is designed so flat that the windings 6 or the thread sections 5 form a straight line and do not describe an arc. In other words, the dimension of the radius of the arcs described by the threaded sections 5 (normally) goes towards infinity.

FIG. 3 shows a further exemplary embodiment of an active element 1 from the front, from the direction marked II in FIG. 1. The view of the fastening section 8 or into the section thread 4 is shown. The active element 1 shown here is produced by means of die sinking, a form of spark eroding. 3 also shows that the radius R of the arcs described by the threaded sections 5 is greater than half the thickness of the active element 1. The radius R of the threaded sections 5 is consequently largely independent of the thickness D of the active element 1. The active element 1 can be fastened in this way by means of a much larger screw than would be possible with a bore with a full circumferential thread, which was produced with a conventional thread former or thread cutter. In this way, even relatively small active elements 1 can be attached to a machine with a screw with a standardized diameter without a special selection of fastening means having to be available.

FIG. 4 shows a perspective view of the active element 1 during the manufacture by means of wire EDM. The contour of the active element 1 is shown with an internal thread 2, which is produced from a tool blank 3 by means of wire EDM. The tool blank 3 is used

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BE2017 / 5558 as an anode, whereas the thin wire 11 forms the cathode. The wire 11 is pulled through the tool blank 3 by two opposite drive rollers 12, 13 with a defined wire tension and a predetermined speed. The contour of the active element 1, including the internal thread 2, can be produced very precisely by wire EDM in one step. The wire EDM is automated so that a previously created 3D drawing of the desired active element 1 can be read into the device for wire EDM. This automatically travels the coordinates of the contour to be created, so that no additional person is required for the actual manufacturing process. In this way, the active element 1 can be produced in a very time-saving and therefore inexpensive manner, in comparison to known methods in which several steps, including reclamping of the tool blank, are necessary.

FIG. 5 shows a sectional illustration of an active element 1 in the form of a bending punch according to FIGS. 1 and 2, which is fastened with a screw 14 to a partly shown machine 15. The active element 1 with the fastening section 8 is arranged in a continuous recess 16 in the machine 15. The recess 16 tapers suddenly at one point, so that a stop 17 is formed. As a result, the active element 1 can only be introduced into the recess 16 with the fastening section 8 until it abuts the stop 17. The screw 14 is inserted from the other side of the continuous recess 16. In this way, the screw 14 can be screwed into the section thread 4 of the active element 1 and ultimately strikes the stop 17 when it is completely screwed into the section thread 4.

The two threaded sections 5 of the active element 1, which form the U-legs of the U-shaped active element 1, are pressed slightly outwards by the screw 14 against the wall of the recess 16. As a result of this spreading action, the active element 1 is fastened to the machine 15 not only by the positive connection with the screw 14, but also by a force or frictional connection between the threaded sections 5 of the active element 1 and the wall of the recess 16 the active element 1 is securely connected to the machine 15. The screw 14 has a round cross-section with fully revolving windings, since the section thread 4 of the active element 1 does not completely

- 11 BE2017 / 5558 running turns, there is also no complete overlap between the internal thread 2 of the active element 1 and the external thread of the screw 14. The overlap angle between the turns 6 of the two threaded sections 5 and the external thread of the screw 14 5 is slightly more in each case than 70 °, so that the overlap angle between the internal thread 2 of the active element 1 and the external thread of the screw 14 is approximately 140 ° to 150 ° in the exemplary embodiment. This is sufficient to ensure that the active element 1 is securely attached to the machine 15 by the screw 14.

io

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reference numeral

active element

inner thread

tool blank

4 section threads

threaded portion

turns

mold section

Fastening section io 9 edge surface

recess

wire

capstan

capstan

14 screw

machine

recess

attack

Claims (12)

claims 1. A method for producing an active element (1) with an internal thread (2), wherein a tool blank (3) is machined in at least one forming step and the tool blank (3) is equipped with an internal thread (2) in at least one thread production step, characterized in that the internal thread (2) is formed in the thread production step as a section thread (4) with thread sections (5), so that the internal thread (2) does not have any fully circumferential turns (6). 2. The method according to claim 1, characterized in that the forming step and the threading step are carried out in a common working step. 3. The method according to claim 1 or 2, characterized in that the forming step is carried out by means of spark erosion. 4. The method according to any one of claims 1 to 3, characterized in that the threading step is carried out by means of spark erosion. 5. The method according to claim 3 or 4, characterized in that the spark erosion is carried out according to the wire EDM method. 6. The method according to claim 4, characterized in that in the thread production step, the threaded sections (5) are formed such that a circular arc is described by the individual threaded sections (5), and that the radius R of the circular arc described is greater than half the thickness of the active element (1). 7. active element (1) for producing a semifinished product or end product from a metal sheet, with a shaped section (7) for shaping the semifinished product or end product and with a fastening section (8), the fastening section (8) having at least one internal thread (2), characterized, 2017/5558 BE2017 / 5558 that the internal thread (2) is designed as a section thread (4) with threaded sections (5), so that the internal thread (2) has no fully circumferential turns (6). 8. active element (1) according to claim 7, characterized in that the 5 active element (1) is produced by a method according to one of the claims 1 to 6. 9. active element (1) according to claim 7 or 8, characterized in that the individual threaded sections (5) each describe a circular arc, and that the radius R of the circular arc described is greater than half the thickness of the active element (1). 10. Active element (1) according to one of claims 7 to 9, characterized in that the internal thread (2) has two threaded sections (5) which are arranged opposite one another. 11. Active element (1) according to claim 10, characterized in that the 15 threaded sections (5) are flat in the tangential direction, so that the radius R of the circular arc described is substantially greater than half the thickness of the active element (1).