EP2344289B1 - Method for producing a molded part provided with a through-hole and device for carrying out the method - Google Patents

Abstract

In order to produce a molded part provided with a through-hole, a rod-shaped blank (R) is pushed forward coaxially through a guide (1) by a defined length into a cavity (2) and then fixed in place. Then the end region of the blank (R) is axially compressed using a swage (3) and reshaped into a disk (S) delimited by the die (2). Thereafter, in a penetration step, a disk core (K_S) having the same cross-sectional shape as the blank (R) is ejected out of the disk (S) using a punch (31) and pushed into the guide (1) and moved back together with the unshaped part of the blank. Then, the penetrated disk (S) is severed from the disk core (K_S) and the molded part is removed from the cavity (2). During the penetration step, the disk (S) present in the cavity (2) is subjected to an axial pressure (F_NH) in the disk core ejection direction and the blank (R) is subjected to an axial counter-force (F_G) opposite to the disk core ejection direction. In this way, the tensile or shearing stresses occurring in the disk are compensated by the superposition of compressive stress, and the formation of fractures, burrs or other deformations on the inner contour of the molded part are prevented.

Description

The invention relates to a method for producing a molding provided with a through hole according to the preamble of claim 1 and to an apparatus for carrying out the method according to the preamble of independent claim 12.

Such a method is for example from the DE 31 47 897 A1 known. According to this document, the serial production of identical annular metal parts starting from a metallic, rod-shaped blank by compression and thereby causing deformation of an end portion of the blank into a disc and then axial puncture of the disc by means of a stamp of the same cross-sectional shape as the (uncompressed) blank and separating takes place of the disc punctured disc core from the disc. The integral with the uncompressed blank section blank core together with the latter forms the starting point for another cycle of the process until the remaining blank remnant is no longer sufficient for the formation of other moldings and is lost as waste.

When piercing the disk core is formed at the peripheral edge of the generated through hole in the disc due to the acting shear or tensile stresses an undesirable fracture surface with cracks and at most burrs that may require reworking of the moldings. In the DE 31 47 897 A1 Although it is mentioned that in order to achieve a smoother surface of the molding during the shearing process by a lower punch a counterforce of sufficient strength should be applied to the blank. For details, however, is not executed.

In the JP 58 070935 A and the JP 62 084849 A Further similar methods and devices for producing annular shaped parts are described. In this case, in each case a blank is clamped in a guide designed as an openable and closable clamping device, and a guide protruding from the guide into a die End piece of the blank is axially compressed by means of a die and deformed into the die into a disk. Subsequently, a core is ejected from the disk. The die comprises a punch and a sleeve enclosing this, the outer dimensions of which are adapted to the shape of the die, so that the die can be moved into the die. The relative to the sleeve relatively movable punch is used to eject the disc core. The problem of shear or tension-induced deformations, burrs or other artifacts is not addressed in these documents.

The invention has for its object to improve a method of the type mentioned in such a way that the moldings produced therewith require no or at least a much lower post-processing. In particular, the molded parts in the region of their generated through hole should have no significant fracture phenomena, burrs or other deformations.

This object is achieved by the method according to the invention and the device according to the invention, as defined in independent claim 1 and independent claim 12, respectively. Particularly advantageous developments and refinements of the invention will become apparent from the respective dependent claims.

In the present context, "bar material" is understood as meaning any material form having pronounced longitudinal extent and any cross-section which is constant over the longitudinal extent. In particular, bars, bars and wires of any dimensions fall under this definition. Circular cross sections are the rule, but the invention is not limited thereto. The term "bar-shaped" is to be understood analogously. "Disc" in the present context is understood to mean any body shape widened in relation to the blank in the cross-sectional dimensions. Flat discs with a particular circular outer contour are the rule, but the invention is not limited thereto.

The essence of the invention consists in the following: In a method for producing a molded part provided with a through hole, in a feed step, a rod-shaped blank is moved in its longitudinal direction through a Guide the same cross-sectional shape as the blank by a defined length in a die whose inner peripheral wall defines the outer circumference of the molded part to be produced, advanced and then held. In at least one forming step, the end region of the blank located outside the guide on the die side is axially compressed by means of a die and thereby formed into a disk limited in the circumference by the die. In an enforcing step, the disk located in the die is penetrated by means of a coaxial stamp for the same cross-sectional shape as the guide, while a piece integral with the undeformed part of the blank disk core of the same cross-sectional shape pushed out of the disk, pushed into the guide and together with in the Guide located undeformed part of the blank moved back against the feed direction of the blank. In a separation step, the pierced disc is separated from the disc core and finally in a removal step, the finished molding is removed from the die. According to the invention, the disc located in the die is acted upon by a sleeve-shaped, holding the punch movable, relative to the punch movable hold-down organ of the die with an axial compressive force in Scheibenkernausstossrichtung and the blank with an axial counterforce against the Scheibenkernausstossrichtung, the outer contour of the hold-down organ in the Substantially corresponds to the inner contour of the die.

Due to the axial compressive force and the axial opposing force of a suitable design of the same a stress state is generated, which prevents substantial breakage, burrs or other deformations on the peripheral edge of the piercing generated through hole in the disc.

Preferably, during the separating step, ie when the disc core which is ejected from the disc located in the matrix is separated from the disc, an axial compressive force in the disc core ejection direction is exerted on the disc located in the female part.

Preferably, the blank is retained during the forming step, the piercing step and the separating step by means of a clamping arrangement acting on its circumference.

The counterforce is preferably introduced into the blank with the aid of the clamping arrangement acting on the outer circumference of the blank. The counterforce can either be applied to the clamping arrangement and transmitted from there to the blank, or the counterforce is generated by the frictional force acting on the blank by the clamping arrangement

The axial compressive force and the opposing force acting against it are preferably dimensioned so that a stress state is achieved in the disc by superposition of compressive stress, which at least compensates for the shear and tensile stresses acting in the disc during penetration. As a result, fractures, burrs or other deformations are optimally avoided at the peripheral edge of the generated through hole.

According to a particularly advantageous embodiment of the method according to the invention, the pane core is not ejected completely from the pane, but preferably only up to about 98-99% of its height or the thickness of the pane. Subsequently, the blank with the integral with him disc core while retaining the said axial pressure force on the disc located in the die axially withdrawn or axially moved away from the disc located in the die until the disc core is separated from the remaining disc ring. Also by this measure, the formation of undesirable deformations on the inner edge of the molded part is avoided and also prevents the punch strikes the inner edge of the die. According to an equally advantageous alternative embodiment, the blank is held and moves the die with the disc located in it from the blank.

In the cited in the DE 31 47 897 A1 described method, the blank is held between two dies, which cause the advance of the blank and the compression of the same. This is the length of the blank and thus the Number of limited producible with a blank moldings and the unusable residual pieces of blanks are lost as waste. According to a further advantageous embodiment of the method according to the invention, this problem is avoided by using a clamping arrangement which acts on the circumference of the blank to support the blank and fix it in position during the forming step and preferably also during the piercing step and during the separating step. This clamping arrangement can be arranged, for example, in the feed direction shortly before the guide. In this way, the length of the blanks is not limited by a second die, so that even long rods or quasi-endless blank material, which is for example wound on coils, can be processed and accordingly virtually no appreciable waste arises

According to a further advantageous embodiment of the method according to the invention, the blank is produced in a reduction step by cross-sectional tapering of a rod material of larger cross-sectional dimensions. This means that the starting material used is a rod material which has larger cross-sectional dimensions than the blank required for the production of the shaped parts, and this rod material is tapered to the cross-sectional dimensions required for the blank or the molded parts to be produced therefrom. The taper can e.g. in a conventional manner by means of a superior Reduziermatrize done by which the bar material during the advance of the blank in the feed step or in an upstream forming step is pressed and / or pulled. In this way, the dimensions of the rod material do not have to match those of the blank and mold parts of different dimensions can be produced with one and the same rod material. This simplifies u.a. the procurement and storage of the bar material considerably.

A suitable device for carrying out the inventive method comprises a guide for a blank, a die, a movable die with a punch for axial compression and deformation of an end portion of the blank, feed means for the blank and retaining means for the blank. According to the invention the die comprises a sleeve-shaped holding-down member which surrounds the punch and is movable relative to the punch, by means of which an axial pressure force can be applied to a disk located in the die, the outer contour of the hold-down member substantially corresponding to the inner contour of the die, and the retaining means comprise one on the periphery of the blank engaging clamping assembly, which is formed separately from the guide and the die and for introducing an axial counterforce in the blank. By the clamping arrangement also the processing of comparatively very long or quasi-endless bar material is possible.

According to an advantageous embodiment, the clamping arrangement is adjustable in the longitudinal direction of the blank.

According to a further advantageous embodiment, the device has a Querschnittsreduzieranordnung for forming the blank of a bar material of larger cross-sectional dimensions. This allows the production of differently sized moldings from a limited set of different bar materials.

The method according to the invention and the device according to the invention can be used in cold to hot forming over the entire temperature range.

Fig. 1-6 -

die wesentlichen Teile eines ersten Ausführungsbeispiels der erfindungsgemässen Vorrichtung in sechs typischen Verfahrensphasen;

Fig. 4a -

ein Detail A aus Fig. 4 in vergrösserter Darstellung;

Fig. 7-12 -

die wesentlichen Teile eines zweiten Ausführungsbeispiels der erfindungsgemässen Vorrichtung in sechs typischen Verfahrensphasen und

Fig. 10a -

ein Detail B aus Fig. 10 in vergrösserter Darstellung.

In the following, the method according to the invention and the device according to the invention will be described in more detail with reference to the attached drawings with reference to two exemplary embodiments. Show it:

Fig. 1-6 -

the essential parts of a first embodiment of the inventive device in six typical stages of the process;

Fig. 4a -

a detail A off Fig. 4 in an enlarged view;

Fig. 7-12 -

the essential parts of a second embodiment of the inventive device in six typical stages of the process and

Fig. 10a -

a detail B off Fig. 10 in an enlarged view.

The following explanations purely describe, for example, the production of flat, annular shaped parts using bar stock or blanks having a circular cross section.

The Figures 1-6 illustrate a first embodiment of the invention, wherein only the essential parts for understanding the invention of the device are shown. It can be seen a guide 1, a die arranged above 2, a die 3 and a clamping arrangement 4 and only symbolized by an arrow feed means 5 and 50 for a rod-shaped blank R with a circular cross-section, for the clamping arrangement 4 and for the die 3. Die Guide 1, the die 2, the die 3 and the clamping assembly 4 are aligned coaxially with each other. The die 3 comprises a punch 31 and a substantially sleeve-shaped or ring-shaped hold-down member 32 enclosing it. The guide 1 and the die 2 are stationary while the die 3 and the clamping assembly 4 are arranged to be axially movable. The guide 1, the die 2, the die 3, the clamping arrangement 4 and the Feeding means 5, 50 are parts of a forming machine, which in a conventional manner drive means for the realization of the movements of the mentioned device parts to be described as well as for the generation of the required forces. The expert requires no further explanation.

The stationary guide 1 has a continuous, in this example cylindrical guide opening 11 with substantially the same cross-sectional shape as the blank R used. The likewise stationary die 2 has a cylindrical inner space 21 whose diameter is greater than the diameter of the blank R or The punch 31 of the die 3 is formed cylindrically and has substantially the same cross-sectional shape as the blank R. The hold-down member 32 of the die 3 has the shape of a cylindrical tube, wherein its outer diameter substantially corresponds to the inner diameter of the die 2. The punch 31 and the hold-down member 32 here have planar end faces 31a and 32a. The clamping arrangement 4 has, for example, two opposing clamping jaws 41 and 42, which are adapted to the outer shape of the blank R.

The method according to the invention runs in a repetitive cycle. In a feed step, the blank R is advanced by means of the provided with a feed means 5 clamping assembly 4 through the guide 1 and the die 2 in its longitudinal direction until the required volume of material for the conversion is available. Then, the punch 31 is advanced until its end surface 31 a in Fig. 1 shown position of Umformbeginns achieved. The portion of the blank extending from the guide 1 to the die 3 is referred to below as the end region.

In the subsequent reshaping step, the clamping arrangement 4 acted upon by a clamping force F _{K is} held stationary and the blank R is fixed axially. Subsequently, the die 3 as a whole is pressed axially against the end region of the blank R, wherein the punch 31 and the hold-down member 32 with a punch force F _st and a hold-down force F _{NH are} applied. By the advancing movement of the die 3, the end portion of the blank is compressed and - in the die into - transformed, initially a bead-like deformation W is formed, which in particular does not yet fill the corner regions of the die 2 ( Fig. 2 ). By further axial advancement of the die 3, the bead-like deformation W is formed into a disc S, which fills the die 2 and has the definite external shape of the molded part to be produced ( Fig. 3 ).

The outer shape of the molded part to be produced is already reached after these two process steps. Now follows an enforcing step, in which the central ring opening of the molded part to be produced is generated. For this purpose, (only) the punch 31 of the die 3 is pressed axially by the application of an axial punching force F _st through the slice S. In this case, the blank R still held in the clamping arrangement 4 is moved away from the guide 1 together with it, counter to a defined counterforce F _G acting axially on the clamping arrangement 4. In this way, a one-piece with the blank disc nucleus K _s is forced out of the disc S and moved to the guide 1 by the punch 31 ( Fig. 4 ). During this step, the hold down member 32 holds the disc S in the die 2 and urges it with an axial pressing force F _NH . At the same time, the described counterforce F _G acts axially on the blank and the disc S. The axial compressive force F _NH and the axial counterforce F _G generate a compressive stress in the disc S, which superimposed on the shear and tensile stresses occurring when passing through the disc and compensated or even overcompensated. The described penetration process is terminated before the disk core K _{s is} completely pushed through. In practice, this means that the disk core K _{s is} pushed through to about 98-99% or is within the disk S with about 1-2% of its height, which corresponds to the thickness of the disk S. The enlarged detail of the Fig. 4a clarifies this.

Next is a separation step. Also during this step, the hold-down member 32 holds the disc S in the die 2 and urges it with an axial pressing force F _NH . The still held in the clamping arrangement 4 blank R is in this step together with the clamping assembly 4 under the action of a release force F _L against the feed direction of the blank by a short distance from the stationary guide 1 and the stationary die 2 moved away in the Fig. 5 So down. The integral with the blank disk core K _s is thereby separated from the disc S, whereby the disc S now has a continuous central hole and thus finished molded part has the desired shape. By acting on the held in the die disc S with the axial compressive force F _NH on the hold-down member 32 are suitable dimensioning of the axial compressive force F _NH and the counter force F _G occurring during the penetration of the disc and the separation of the disc core K _s shear and Tensile stresses compensated or overcompensated by superposition of compressive stress and thereby prevents the formation of fractures, burrs or other deformations on the peripheral edge of the generated through hole in the disc.

The opposing force F _G acting on the blank can also be generated by friction according to an alternative method variant. The clamping assembly 4 is kept stationary and the clamping force F _{K set} slightly lower so that the blank R can move against the frictional resistance generated by the clamping action by the clamping arrangement 4. The frictional resistance corresponds to the said counterforce.

According to a further variant of the method, the separating step can also be carried out so that the blank is not moved away from the die but the blank R is held in the clamping arrangement 4 and the die 2 with the slice S located in it, possibly together with the guide 1 , is moved away from the blank. The required for this, acting on the die 2 and the guide 1 release force is in Fig. 5 symbolized by the arrow F _La .

The finished molded part located after these process steps in the die 2 is designated FT and is now removed in a removal step from the device, wherein this is preferably done by ejecting the molding FT with an ejector not shown here. For this purpose, the die 3 in the in Fig. 6 shown position while at the same time retracted the punch 31 in the hold-down member 32 until their faces are again in a plane. A gripping device 6 symbolized only by an arrow grips the finished molded part FT and leads it eg to a collection container, not shown, or to another processing station. Finally, the die 3 and the clamping arrangement 4 are again in their in Fig. 1 shown starting positions, and another cycle of the process can begin.

The Figures 7-12 illustrate a second embodiment of the invention, which differs from the embodiment according to the Figures 1-6 essentially only differs in that in the feed direction of the blank R before the clamping arrangement 4 is arranged coaxially to this a Querschnittsreduzieranordnung in the form of a Reduziermatrize 7. The Reduziermatrize 7 is arranged at a fixed distance to the clamping arrangement and mitbewegbar with the latter.

In this process variant, a rod material R _{A is} used as the starting material, which has larger cross-sectional dimensions than the actual blank R required for the production of the moldings, and the actual blank R is formed from this thicker rod material R _A in a Reduzierschritt. In other words, the cross-sectional dimensions of the blank R are reduced to the desired or required dimension before reaching the clamping arrangement 4 or the guide 1. This cross-sectional or thickness tapering is advantageously carried out in the context of the advancing step of the method, but can also take place in an upstream step. Due to the cross-sectional taper in the course of the rest of the procedure, the dimensions of the rod material do not have to match those of the blank and it can be made with one and the same rod material moldings of different dimensions.

All other parts of the in the Figures 7-12 shown device fully correspond to the device of Figures 1-6 , wherein like parts are designated by like reference numerals. With the exception of the additional reduction or tapering step, all method steps and sequences of movement are the same as in the exemplary embodiment of FIG Figures 1-6 , so that a more detailed explanation is unnecessary. Furthermore, those explained in connection with the first embodiment apply Method variants, mutatis mutandis, for the embodiment according to the Figures 7-12 ,

Claims (15)

1. Method for producing a moulded part (FT) provided with a through-hole, wherein in an advancing step a rod-shaped blank (R) is advanced by a defined length in its longitudinal direction through a guide (1) having the same cross-sectional shape as the blank (R) into a die (2), the inner peripheral wall whereof establishes the outer periphery of the moulded part (FT) to be produced, and is then held fast, in at least one reshaping step the end region of the blank (R) located outside the guide (1) on the die side is axially compressed by means of a swage (3) and thereby reshaped to form a disc (S) limited at the periphery by the die (2), in a penetration step the disc (S) located in the die (2) is penetrated by means of a punch (31) coaxial with the guide (1) and having the same cross-sectional shape as the guide (1) and a disc core (K_S) in one piece with the undeformed part of the blank (R) and having the same cross-sectional shape is ejected from the disc (S), pushed into the guide (1) and, together with the undeformed part of the blank (R) located in the guide (1), moved back opposite to the advancing direction of the blank (R) and against an axial counter-force (F_G) introduced into the blank (R), in a severing step the punctured disc (S) is severed from the disc core (K_S), and in a removal step the finished moulded part (FT) is removed from the die (2), characterised in that during the penetration step the disc (S) located in the die (2) is subjected, by a sleeve-shaped hold-down element (32) of the swage (3) that is mobile relative to the punch (31) and surrounding the punch (31), to an axial pressing force (F_NH) in the disc core ejection direction.
2. Method according to claim 1, characterised in that during the severing step the blank (S) located in the die (2) is subjected to an axial pressing force (F_NH) in the disc core ejection direction.
3. Method according to claim 1 or 2, characterised in that the axial pressing force (F_NH) and the axial counter-force (F_G) are selected with a magnitude such that there is generated in the disc (S) a stress state which at least compensates for the tensile and shearing stresses occurring.
4. Method according to any one of the preceding claims, characterised in that in the penetration step the disc core (K_S) is not completely ejected from the disc (S), but preferably only up to 98-99% of its thickness.
5. Method according to any one of the preceding claims, characterised in that in the severing step the remainder of the blank (R) together with the disc core (K_S) in one piece with the latter is moved away axially from the disc (S) held stationary in the die (2), so that the disc core (K_S) is severed from the disc (S).
6. Method according to any one of claims 1-4, characterised in that in the severing step the die (2) with the disc (S) located therein is moved away axially from the remainder of the blank (R) held stationary and the disc core (K_S) in one piece with the latter, so that the disc core (K_S) is severed from the disc (S).
7. Method according to any one of the preceding claims, characterised in that the blank (R) is held fast during the reshaping step, the penetration step and the severing step by means of a clamping arrangement (4) engaging at its periphery.
8. Method according to claim 7, characterised in that the axial counter-force (F_G) acts on the clamping arrangement (4) and is introduced via the latter into the blank (R) or that the axial counter-force (F_G) is generated by a frictional force exerted by the clamping arrangement (4) on the blank.
9. Method according to any one of the preceding claims, characterised in that the blank (R) is produced in a reducing step by cross-sectional narrowing from a rod material (RA) having larger cross-sectional dimensions.
10. Method according to claim 9, characterised in that the reducing step takes place during the advancing step.
11. Method according to any one of the preceding claims, characterised in that the hold-down element (32) has the shape of a cylindrical pipe, wherein the outer diameter of the hold-down element (32) essentially corresponds to the inner diameter of die (2).
12. Device for carrying out the method according to claim 1 with a guide (1) for a blank (R), a die (2), a mobile swage (3) with a punch (31) for the axial compression and reshaping of an end region of the blank, advancing means (5) for the blank and holding means (4) for the blank, characterised in that the swage (3) comprises a sleeve-shaped hold-down element (32) mobile relative to the punch (31) and surrounding the punch (31), by means of which hold-down element a disc (S) located in the die (2) can be subjected to an axial pressing force (F_NH), wherein the holding means comprise a clamping arrangement (4) engaging at the periphery of the blank (R), said clamping arrangement being designed separate from the guide (1) and the die (2) and for introducing an axial counter-force (F_G) into the blank (R).
13. Device according to claim 12, characterised in that the clamping arrangement (4) can be adjusted in the longitudinal direction of the blank (R) against an axial counter-force (F_G).
14. Device according to claim 12 or 13, characterised in that it comprises a cross-section reducing arrangement (7) for forming the blank (R) from a rod material (R_A) having larger cross-sectional dimensions.
15. Device according to any one of claims 12 to 14, characterised in that the hold-down element (32) has the shape of a cylindrical pipe, wherein the outer diameter of the hold-down element (32) essentially corresponds to the inner diameter of die (2).

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