EP0131770B1 - Method of fine-cutting work pieces, and fine-cutting tool for carrying out the method - Google Patents

Description

The invention relates to a method for fineblanking workpieces, according to the preambles of patent claims 1 and 2, and to fineblanking tools intended for the exercise thereof, according to the preambles of patent claims 3 and 4.

Fine blanking (sometimes also called "fine blanking") differs from conventional punching technology essentially in that the workpiece is firmly clamped before and during the cutting process and guided with tight tolerances. For this purpose, the material - usually steel strip with a thickness of 0.3 mm to about 15 mm - is clamped in the tool between a guide or press plate and a cutting plate. The guide plate and / or the cutting plate carry an annular tooth adapted to the workpiece outline, which is pressed into the material. The ring spike prevents the material from flowing away to the side. The cutting process is carried out by means of a cutting punch guided in the guide plate with a tight tolerance and an ejector also closely tolerated in the cutting plate, which presses against the cutting punch with a counterforce of about 10 to 20% of the cutting force, so that the two punches start cutting out Guide the material and later the workpiece between them. Within the cutting punch and the ejector, a number of internal shaping punches and, in turn, corresponding ejectors can be used for the purpose of shaping or perforating the workpiece. The publication VDI 3345 "Feinschneid", May 1980, of the "VDI guidelines" gives an overview of the fineblanking technology. For the general state of the art, reference is made to this document.

Since, in the fineblanking technology, the cutting punches usually cannot dip into the recess of the cutting plate due to the narrow tolerances, a thin cutting burr remains on the circumferential edge of the workpiece facing the cutting punch, and the cutting punch and the ejector basically have essentially the same circumferential configuration as the guide openings are analog in the guide plate and in the cutting plate.

Reference is made to EP-A1-0 043 359 regarding the prior art of fineblanking, from which the invention is based. The workpiece and the method according to this document differ from the generally customary fineblanking technique explained in the introduction in that the conventional ring serrations are omitted and instead the material to be finely cut is supported on its lateral surface outside the cutting line by supporting members arranged on the side of the cutting die. This should enable tear-free cut surfaces, even with thicker materials.

DE-B1-27 27 445 discloses a multi-stage process with an associated device for cutting and / or punching workpieces from metallic sheets. In a first process step, the sheet is cut, but the workpiece is not yet cut. In the second work station, the workpiece, which was initially only cut, is counter-cut in the opposite direction with a second punch. Finally, in a third work step and a third work station with a further cutting punch, the workpiece is cut out in the effective direction of the cutting punch of the first work step. Counter-cutting is to achieve workpieces with absolutely burr-free cutting surfaces.

Neither the means of EP-A1-0 043 389 nor DE-B1-27 27 445 make it possible to obtain workpieces with smooth, but oblique or conical cut surfaces.

The invention is therefore based on the object of specifying methods for fineblanking workpieces which allow the manufacture of finely cut workpieces which are conical or wedge-shaped at least in parts of their outer cut surfaces in a simple manner. Such a problem arises, for example, in the case of spur gears, the tooth flanks of which should be at a certain inclination to one another. Another of many conceivable applications would be a gear wheel, the head and tooth space surfaces of which are to be arranged at a certain inclination relative to the axis of rotation.

A first method according to the invention, which achieves the underlying task, is that the workpiece is pressed into a recess of the cutting plate that tapers or conically narrows at least on partial circumferential areas during the cutting out and that the cut-out conical workpiece against the cutting direction is ejected again by means of the ejector the cutting plate is ejected. In other words, this means that the actual cutting process is overlaid in time and place by an embossing process that takes place within the recess of the cutting plate. During the cutting process, the proportion of material that is brought into flow and cut and corresponds to the workpiece not only experiences an axial feed in the resulting direction of movement of the cutting punch, but also, at the same time, an at least partial compression towards the cutting punch axis in accordance with the inclination or conicity.

A fine blanking tool for practicing this method according to claim 3 according to the invention is that the inner surface of the Breakthrough in the cutting plate, forming flat surfaces, is arranged at least on parts of its circumference and on a section in the axial direction of the ejector, starting in the support plane of the material, inclined to the ejector axis and that the cut conical workpiece against the cutting direction by means of the ejector from the Cutting plate can be ejected.

Deviating from the previously used fineblanking tools, the inner surface surface lines of the workpiece contour in the cutting plate are not completely parallel to the ejector axis, but are inclined at a distance approximately corresponding to the workpiece thickness from the support plane of the workpiece away according to the desired conicity or the desired inclination of the workpiece inclined surfaces. The end section of the cutting plate facing the material or workpiece thus forms a circumferential embossing shape with inward-facing embossing surfaces located in this section.

Accordingly, according to a further feature of the invention, the section having the embossing surfaces measured in the axial direction of the ejector is slightly larger than the material thickness of the material. Because of the tapering of the cross section of the embossing recess in the cutting plate, the material displaced here flows in the direction of the ejector axis.

The particular advantage of the described method for producing a workpiece with an at least partially conical or inclined cutting surface is that it does not require any further work stages, in particular also no machining. The device required to carry out the method is also of simple configuration and hardly more complex than a conventional fineblanking tool which only cuts.

Now there can be particularly problematic workpieces, for example those in which essentially thin-walled and small cross-sectional rings have to be cut, which are not inherently stable in themselves and in which the single-stage "combined cutting / embossing process" could therefore lead to complications. For these cases, the invention proposes a two-stage process, which is characterized in that in a first step the workpiece is cut in a manner known per se in the manner of enforcement from the material and in a second step the cutting process is completed and the workpiece is pressed into a tapered or conically narrowing recess of an embossing plate, at least on partial circumferential areas, and that the embossed conical workpiece is removed from the embossing plate against the embossing direction by means of the ejector.

The two steps can of course be carried out in a machine in a follow-up tool. The first step practically does not differ from a fineblanking process to produce a so-called "enforcement" (see VDI guidelines, p. 7, "3.6. Forming processes", example 6 from above). The difference is essentially only that the "asserted material" in the process according to the invention essentially already corresponds to the finished workpiece in the outer outline. This is then embossed in the second work step in a second tool step on the outer cut surfaces and at the same time finished cut.

A fineblanking tool for carrying out this two-stage process is characterized according to claim 4, characterized in that the tool of the first stage is designed in a manner known per se to form an enforcement and that in the tool of the second stage the inner surface of the opening in the embossing plate, forming embossing surfaces, at least is arranged on parts of its circumference and on a section in the axial direction of the ejector, starting in the plane of the embossing plate, inclined to the ejector axis and that the embossed conical workpiece can be removed from the embossing plate by means of the ejector.

Here too, as in the case of the aforementioned tool, the section having the embossing surfaces measured in the axial direction of the ejector is at least slightly larger than the material thickness of the material.

In principle, the tool of the second working stage does not differ from the individual tool performing the first method. Here only the cutting plate is essentially converted into an embossing plate.

• Fig. 1 ein "einstufiges" Feinschneidwerkzeug zur Ausübung des einstufigen Verfahrens,
• Fig. 2 eine Ansicht eines damit erzeugten Werkstücks,
• Fig. 3 und 5 die beiden Arbeitsstufen eines "zweistufigen" Werkzeugs zur Ausübung des zweistufigen Herstellungsverfahrens,
• Fig. 4 und 6 das jeweils nach Beendigung der Verfahrensschritte gemäß den Fig. 3 und 5 erhaltene Erzeugnis,
• Fig. 7 eine Aufsicht auf einen außenverzahnten Ring als beispielshaftes Werkstück und
• Fig. 8 eine Aufsicht auf einen Zahnausschnitt des Werkstücks nach Fig. 7.

The invention is also understood from the following description of the two methods and tools, as shown in the schematic drawings. Another drawing shows an example of a workpiece obtained with the method and the tools. The drawings show:

• 1 is a "one-step" fineblanking tool for performing the one-step process,
• 2 is a view of a workpiece produced with it,
• 3 and 5, the two working stages of a "two-stage" tool for practicing the two-stage manufacturing process,
• 4 and 6, the product obtained after completion of the process steps according to FIGS. 3 and 5,
• Fig. 7 is a plan view of an externally toothed ring as an exemplary workpiece and
• 8 is a plan view of a tooth cutout of the workpiece according to FIG. 7.

The tool according to FIG. 1 comprises - in an initially conventional design - a cutting plate 10 with an opening 11 corresponding to the workpiece contour, in which a complementarily contoured counter-holder (ejector) 12 is arranged displaceably in the direction of its longitudinal axis 13. Above this half of the tool is a guide or press plate 14 with a contoured recess 15 for the correspondingly contoured punch 16, which is arranged coaxially with the counter-holder (ejector) 12. Just for the sake of completeness, it should be mentioned that for workpieces that have additional internal shapes, at least one internal shape stamp and accordingly at least one ejector must be arranged within the counter-holder (ejector) 12 and accordingly within the cutting stamp 16, for example of the type described under "2.1. Working principle" described on page 2 of the VDI guidelines 3345.

On the side facing the material 17 (sheet metal strip), the guide or press plate 14 has an annular spike 18 which is wedge-shaped in cross section and penetrates the material 17 and prevents it from flowing out.

The opening 11 in the cutting plate 10 now has the peculiarity that it, starting from the material support plane 19 over a section 20 measured in the direction of the axis 13, which is slightly larger than the material thickness 21, on its inwardly facing peripheral surface 22 is at least partially inclined or conical, in such a way that - as can be clearly seen in FIG. 1 - the cross section of the recess 11 towards the counter-holder (ejector) 12 decreases at the corresponding points. Cutting punch 16 and counter-holder (ejector) 12 therefore have different cross sections Q, q and diameter. In the example shown, the inclination 23 can be approximately 3 ° -4 °, but also more. The corresponding angle of inclination is indicated at 24.

If, as an example, it is assumed that the surface 22 over the section 20 is formed circumferentially in the opening 11, the cut-out workpiece 25 shown in FIG. 2 results in the form of a truncated cone with a uniformly conical outer cutting surface 26 all around.

In the method carried out with the tool according to FIG. 1, at the same time the cutting punch 16 advances, the material 27 which has been brought into flow is pushed downward against the counterforce of the ejector 12 with respect to FIG. 1 and thus simultaneously into the "embossing shape limited by the peripheral surface 22 "pressed within the cutting plate 10. Fig. 1 shows the final cutting state, in the connection of which the tool halves open again.

The tool parts are actuated in the manner and sequence customary for fineblanking in that the cutting plate 10 and guide plate 14 are first moved against one another when the material is not deformed until they grasp the material between them. At the same time, cutting punches 16 and counterholders (ejectors) 12 run towards each other until they clamp material 17 between them.

The cutting punch 16 then moves downward with respect to FIG. 2, while the counter-holder (ejector) 12 follows this movement while exerting a counter pressure until the situation shown in FIG. 1 is reached.

3 shows the first stage of a two-stage tool for carrying out the two-stage method. This tool is constructed from a cutting plate 110, a counter-holder (ejector) 112, a guide or pressing plate 114 with ring serration 118 and a cutting punch 116 guided in the plate 114. This tool and its function correspond to a conventional fineblanking tool with which enforcements are generated . The "enforced" blank is identified by 127 and is shown separately once again adhering to the material 117 in FIG. 4. The pre-cut blank 127 is still connected to the material 117 via a relatively strong material bridge 128. 4, the material 117 with the partially cut blank 127 is fed to the second tool stage shown in FIG. 5. The individual parts of this tool level are each provided with reference numbers increased by 100. One difference is that plate 210 is an "embossing plate". Analogously to the cutting plate designated by 10 in FIG. 1, it has a section 220 with an at least partially conical or inclined embossing surface 222. Accordingly, the finished workpiece 225, like the workpiece 25 in FIG. 2, has the shape of a truncated cone with an all-round cone with an analogous geometry Outer cut surface 226. Also in the two-stage process, an embossing process takes place, this time starting from a precut or cut workpiece.

FIG. 7 schematically shows a typical workpiece, the methods and tools according to the invention are particularly suitable for producing. It is an annular spur gear 30 with teeth 31. As FIG. 8 shows, the tooth flanks 32 and 33 have a taper at an angle 35 with respect to the axis of rotation 34 of the toothed ring 30. The tooth bases 36 and the tooth heads 37, however, can have surfaces whose surface lines run parallel to the axis 34. This workpiece 30 thus shows a typical example of the fact that and how only parts of the outer cut surfaces of a finely cut workpiece can be produced in a simple manner conically or obliquely.

Claims (5)

1. Method for the precision blanking of workpieces (25), in which the material (17) is clamped between a guide plate (14) (pressure plate) and a blanking die plate (10) and the workpiece (27) is cut out by means of a blanking punch (16) and a pressure pad (ejector) (12), which counters the effect of the latter and is quided in a recess in the blanking die plate (10), and, if required, is also finished by means of internal forming punches, characterised in that,. during the cutting-out operation, the workpiece (27) is pushed into a recess in the blanking die plate (10) which tapers or narrows in a conical manner at least at partial circumferential areas (22), and that the conical workpiece (25) which has been cut out is ejected from the blanking die plate (10) against the cutting direction by means of the ejector (12).

2. Method for the precision blanking of workpieces (225), in which the material (117) is clamped between a guide plate (114,214) and a blanking die plate (110) and the workpiece (127, 227) is cut out by means of a blanking punch (116, 216) and a pressure pad (ejector) (112, 212), which counters the effect of the latter and is guided in a recess in the blanking die plate, and, if required, is also finished by means of internal forming punches, characterised in that the workpiece (127) is cut out of the material (117) as a pushed-through part in a manner which is known per se in a first stage of operation (Fig. 3), that the cutting process is completed and the workpiece (227) is pushed into a recess in a stamping die plate (210) which tapers or narrows in a conical manner at least at partial circumferential areas (222) in a second stage of operation (Fig. 5), and that the stamped conical workpiece (225) is removed from the stamping die plate (210) against the stamping direction by means of the ejector (212).

3. Precision blanking tool for carrying out the method according to claim 1, comprising a blanking die plate (10) with an opening (11), in which an appropriately shaped ejector (12) is arranged so as to be displaceable in the direction of its longitudinal axis (13), and a guide or pressure plate (14), which is provided above the blanking die plate (10) and comprises a recess (15) for an appropriately shaped blanking punch (16) guided coaxially with the ejector (12) (pressure pad), characterised in that the internal surface (22) of the opening in the blanking die plate (10) extends from the bearing plane (19) of the material (17) towards the ejector axis (13) in an inclined manner so as to form stamping surfaces, at least at parts of its circumference and at a section (20) in the axial direction (13) of the ejector (12), and that the conical workpiece (25) which has been cut out can be ejected from the blanking die plate (10) against the cutting direction by means of the ejector (12).

4. Precision blanking tool for carrying out the method according to claim 2, comprising a blanking die plate (110) with an opening (111), an ejector (112,) (pressure pad), which is guided in the latter, a guide or pressure plate (114) and a blanking punch (116), which is guided in the latter, in a first stage of operation, and a stamping die plate (210) with a peripheral stamping surface (222), an ejector (212) (pressure pad), which is guided in the stamping die plate (210), and a guide plate (214), which is arranged above the latter, with a stamping punch (216) in the second stage of operation, characterised in that the tool of the first stage of operation (Fig. 3) is formed in a manner which is known per se in order to form a pushed-through part (Fig.4), and that in the tool of the second stage of operation (Fig. 5) the internal surface (222) of the opening in the stamping die plate (210) extends from the plane (219) of the stamping die plate (210) towards the ejector axis (213) in an inclined manner so as to form stamping surfaces, at least at parts of its circumference and at a section (220) in the axial direction (213) of the ejector (212), and that the stamped conical workpiece (225) can be removed from the stamping die plate (210) against the stamping direction by means of the ejector (212).

5. Precision blanking tool according to claim 3 or 4, characterised in that the section (20; 220), which is measured in the axial direction (13; 213) of the ejector (12; 212) and comprises the stamping surfaces (22; 222), is slightly larger than the thickness (21; 221) of the material (17: 217).

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