EP0043389B1 - Tool and method for precision cutting - Google Patents

Abstract

A process for precision cutting of a hole near the edge of a thin workpiece. Clamping of the workpiece laterally adjacent the hole to minimize deformation of the workpiece is achieved prior to cutting the hole with a cutting punch.

Description

The invention relates to a tool for a fineblanking machine according to the preamble of claim 1 and a method for operating the same.

Tools and methods of fineblanking technology are known for. B. from the manual »Feinschneid«, publisher: Feintool AG, Lyss (Switzerland), 2nd edition 1977, z. B. Pages 66, 67, 81, 82. The fineblanking technique differs from normal punching in particular in that the workpiece is clamped between a cutting plate and a press plate, also called a cutting and holding plate, before the cutting process begins, and on the workpiece a counterholder acts on the opposite side. The holding plate and, if necessary, also the cutting plate each carry an annular tooth following the partial contour, which is pressed into the workpiece before the cutting process. With this technique, the bending that is inevitable with conventional punching is avoided, and tear-free smooth cuts are created, which guarantee a close tolerance of the workpieces and save additional reworking of the cut surfaces such as repassing, grinding, etc.

Fineblanked parts are used in a number of industrial sectors in thicknesses between 0.3 mm and 15 mm.

However, it has not yet been possible to use fineblanking technology in the manufacture of parts with holes whose diameter or web and edge widths are considerably smaller than the material thickness.

Such parts have so far only been able to be produced by machining processes, that is to say drilling or milling. These processes not only produce chips that are difficult to remove, they also require a subsequent deburring process. They are therefore uneconomical.

Conventional stamping is not suitable for the production of such parts. If the values D / S = 1 or A / S = 1 (with D = diameter of the hole, S = material thickness, A = web or edge width) are undershot or material thicknesses of 15 mm are exceeded, durability problems arise on the one hand Tools that cannot withstand the required pressure load and, on the other hand, deformation of the holes.

With a fineblanking technique of the known type, i.e. with ring serration and clamping force and counterforce, the limit values for normal punching can be improved somewhat, and there is also an improvement in the quality of the cut parts, but these values are still not sufficient for many practical cases.

US-A-1 995 446 describes a punching device for producing metal rakes, especially garden rakes. The stamp B punches recesses through the metal strip C into the form A with the form plate 10 and form slots 16, 17 into it by means of the punch tools 18, 19. In order to avoid deformations of the metal, in particular to secure the metal against lateral displacement and twisting, bolts 24 and 25 are provided in the mold plate 10 on opposite sides of the mold slot 16, which engage in the already punched recesses and thus secure the material to be punched. The bolts are under the action of the coil springs 27. A wiper plate 30 is also provided.

The known device is not a fineblanking tool since the counter holder is missing. It is also not a question of high-quality, tear-free smooth cuts and there is also no question that the limit values of fineblanking technology would be sought.

DE-C-511 609 describes a punching device in which the workpiece S is guided and cut by the stationary shear knife 3 by means of a movable jaw 2, whereupon the remaining part of the workpiece A is clamped between the movable jaw 2 and the stationary jaw 1 and punched by stamp 5.

Also in this known device the counter-holder is missing, it is not a fine blanking device.

Both known devices therefore do not provide any information for solving the problems mentioned above.

It is therefore the object of the invention to improve a known fine-cutting tool of the type specified at the outset and a method for operating the same in such a way that cut surfaces with a smooth cut, that is to say without tearing, can be produced up to limit values which are considerably lower than those achieved so far.

This object is achieved by the features specified in the claims.

herzustellen, in Stahl- und NE-Metallen, bei Dicken von 1 mm bis 20 mm, ja sogar bis 30 mm.The essence of the invention is to be seen in the fact that the material is laterally supported on its outer surface outside the cutting line at critical points by the support members. What is critical at first is always the part of the lateral surface that is closest to the cutting line and the distance between it, the web or edge width, is smaller than the material thickness. But even if this distance is greater than the material thickness, but the diameter of the hole to be cut is smaller than the material thickness, the invention has a surprisingly advantageous effect: Apparently the pressure distribution in the workpiece is influenced by the support so favorably that the cutting process is thereby considerably facilitated and thus the service life of the tool is increased sustainably. Especially in this case, however, the cutting punch should be surrounded on its entire circumference by one or more support members. With the invention, the values achievable in fineblanking with a ring spike are unforeseen improved to a degree. The invention makes it possible to design interior and exterior shapes up to the limit values D / S ≥2 / 3; A / S ≥

to manufacture, in steel and non-ferrous metals, with thicknesses from 1 mm to 20 mm, even up to 30 mm.

• Fig. 1 eine erste Ausführungsform der Erfindung zum Herstellen von Lochblechen, im Querschnitt,
• Fig. 2 die Ausführungsform nach Fig. 1 in Draufsicht,
• Fig. 3 den Querschnitt eines mit einer Ausführungsform nach Fig. 1 und 2 hergestellten Lochbleches,
• Fig. 4 die Draufsicht eines mit einer Ausführungsform nach Fig. 1 und 2 hergestellten Lochbleches mit einem ersten Lochbild,
• Fig. 5 eine Draufsicht wie in Fig. 4 mit einem zweiten Lochbild,
• Fig. 6 eine zweite Ausführungsform der Erfindung zum Herstellen eines Loches in einer vorgefertigten Außenform, im Querschnitt,
• Fig.7 die Ausführungsform nach Fig. 6 in Draufsicht,
• Fig. 8 den Querschnitt eines mit einer Ausführungsform nach Fig. 6 und 7 hergestellten Teiles,
• Fig. 9 das Teil nach Fig. 8 in perspektivischer Darstellung,
• Fig. 10 ...12 andere Arten von mit einer Ausführungsform nach Fig. 6 und 7 hergestellten Teilen,
• Fig. 13 eine dritte Ausführungsform der Erfindung zum Herstellen von Außenformen aus vorgefertigten Rohlingen, im Querschnitt,
• Fig. 14 die Ausführungsform nach Fig. 13 in Draufsicht, bei abgenommenem Halteglied,
• Fig. 15 das Stanzgitter im Querschnitt und das Stanzteil in Seitenansicht eines mit einer Ausführungsform wie in Fig. 13 und 14 bearbeiteten Materials,
• Fig. 16 die Draufsicht auf das Stanzteil aus Fig. 15,
• Fig. 17 das Stanzgitter im Querschnitt, und das als Zahnrad ausgebildete Stanzteil in teilweisem Querschnitt eines mit einer Ausführungsform wie in Fig. 13 und 14 bearbeiteten Materials, und
• Fig.18 die Draufsicht auf das Zahnrad aus Fig. 17.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the figures. It shows

• 1 shows a first embodiment of the invention for producing perforated sheets, in cross section,
• 2 shows the embodiment of FIG. 1 in plan view,
• 3 shows the cross section of a perforated plate produced with an embodiment according to FIGS. 1 and 2,
• 4 shows the top view of a perforated plate produced with an embodiment according to FIGS. 1 and 2 with a first hole pattern,
• 5 is a plan view as in FIG. 4 with a second hole pattern,
• 6 shows a second embodiment of the invention for producing a hole in a prefabricated outer shape, in cross section,
• 7 shows the embodiment according to FIG. 6 in plan view,
• 8 shows the cross section of a part produced with an embodiment according to FIGS. 6 and 7,
• 9 shows the part according to FIG. 8 in a perspective view,
• 10 ... 12 other types of parts produced with an embodiment according to FIGS. 6 and 7,
• 13 shows a third embodiment of the invention for producing external shapes from prefabricated blanks, in cross section,
• 14 shows the embodiment according to FIG. 13 in plan view, with the holding member removed,
• 15 shows the punched grid in cross section and the punched part in side view of a material processed with an embodiment as in FIGS. 13 and 14,
• 16 shows the top view of the stamped part from FIG. 15,
• 17 shows the punched grid in cross section, and the punched part designed as a gearwheel in partial cross section of a material processed with an embodiment as in FIGS. 13 and 14, and
• 18 shows the top view of the gearwheel from FIG. 17.

1 and 2, a cutting punch 1 designed as a punch is shown, which penetrates the material clamped and to be punched between the holding member 4, designed as a holding plate, and the cutting plate 2, down to the cutting plate 2. The punch 1 is moved forward with the cutting force F _s . The counterholder 8 counteracts it with the counterforce F _G. The punched part 7 cut out of the punched grid 6 is shown between the punch 1 and the counter holder 8. Here, the lead frame 6 is thus a perforated plate, the stamped part 7 is a waste slug. The holding force F _H is transmitted to the holding plate 4 by the pressure bolts 5.

In contrast to the prior art, however, the material to be cut is not held in place by means of an annular spike provided on the holding plate 4. Rather, the holding plate 4 has special holes 9 through which longitudinally movable support stamps 3 pass. These support the material to be punched on the lateral surfaces 11 of the holes adjacent to the cutting line 12. The holes 9 have a diameter of 1.02 to 1.06 the diameter of the support stamp 3, so that there is a game x, and any jamming is avoided. The punch 1 is surrounded on all sides by support stamps 3. The diameter of a support punch 3 is equal to the diameter D of the punch 1 or the hole to be cut, so that the holes adjacent to the cutting line of the material to be punched are supported on their entire circumferential surface.

The shortest distance A (see FIG. FIG. 3) between the punch 1 and an adjacent support punch 3 may be between _^1/3 and _{^2/3 of} the thickness S of the lying material to be cut, and the diameter D of the hole punch 1 is between _^2/3 and _^1/1 of the thickness S, and yet be obtained high quality cut surfaces without tearing. This is completely unattainable with known techniques, not even by fine cutting with a ring spike.

• Zunächst wird das zu lochende Material zwischen der Schneidplatte 2 und der Halteplatte 4 mit der Haltekraft F_H eingeklemmt. Die Stützstempel 3 sind mit der Steuerkraft F_c nach oben gezogen. Es wird sodann der Lochstempel 1 mit der Schnittkraft F_s durch das Material hindurchgedrückt. Entgegen wirkt der Gegenhalter 8 mit der Gegenkraft F_G. Durch diese Aktion wird der Abfallbutzen 7 aus dem Material ausgeschnitten, so daß das erwünschte Loch entsteht und das Stanzgitter bzw. Lochblech 6 zurückbleibt.

The device shown in FIGS. 1 and 2 is preferably suitable for producing perforated sheets as in FIGS. 4 and 5, such as screens or support plates, and is operated as follows:

• First, the material to be punched is clamped between the cutting plate 2 and the holding plate 4 with the holding force F _H. The support rams 3 are pulled upwards with the control force F _c . The punch 1 is then pressed through the material with the cutting force F _s . The counterhold 8 counteracts with the counterforce F _G. Through this action, the waste slug 7 is cut out of the material, so that the desired hole is created and the lead frame or perforated plate 6 remains.

This first punching process can still be carried out without the participation of the support stamp 3, since the area of the punching has not yet been weakened by surrounding holes.

The clamping of the material via the forces F _H and F _G prevents the material from bending, and the force F _H ensures that the punched grid 6 is stripped from the punch 1 after the punching process has been carried out when the punch is withdrawn.

After completion of the first punching process, the holding plate 4 then strips the lead frame or perforated plate 6 from the punch and the same is then moved until the first cut hole comes to rest under a support punch 3. The punched grid 6 can be moved into the new hole position by hand or via automatically driven coordination.

The support stamp 3 is then inserted into the cut hole, then the material clamped the holding plate 4, and finally cut the next hole by means of the punch 1 acting against the counter-holder 8. During this punching process, the support punch 3, which is retracted into the first hole, already has a lateral support.

These operations are repeated, with all support stamps 3 being retracted as soon as the corresponding number of holes has been cut.

The holding plate 4 carries the hole pattern to be cut into the material in shape and distance. As can be seen, the process consists of four bars, i. H. the device according to the invention has four functions.

In principle, the individual elements of the device can be driven mechanically or hydraulically. However, a hydraulic drive is advantageous because it enables the individual forces, speeds of the elements and the cutting path to be better controlled.

In Fig. 3, a perforated plate is shown in cross section, as can be produced in the manner described above. The cut surfaces of the holes are smooth and tear-free. The achievable limits are D / S> _^2/3; A / S> ¹ / _a .

The invention in the described embodiment can be used e.g. B. in the production of sieve sorting plates for seeds, sieve sorting plates for food processing, cutting plates for a meat grinder, cooling line support plates for reactors, etc.

• Hier soll nicht ein Lochblech in Art eines Siebes oder dergleichen hergestellt werden, sondern es sollen ein oder mehrere Löcher in eine bereits fertige Außenform geschnitten werden, wobei der Abstand des Randes des zu schneidenden Loches vom Außenrand des Materials ggfs. nur ¹/₃ der Materialdicke betragen kann.

FIGS. 7 and 7 show an embodiment of the invention which corresponds to that shown in FIGS. 1 and 2 except for the following special features:

• Here is not a perforated plate in the manner of a sieve or the like are produced, but it should be cut one or more holes in an already finished outer shape, whereby the distance of the edge to be cut hole from the outer edge of the material if necessary. Only ^{_one third} of the material thickness can be.

In this embodiment of the invention, the lateral support is now provided by a support member 3, which is designed as a support plate concentrically surrounding the cutting punch 1 and movable in its direction. With its inner recess, the support plate is brought into positive engagement with the outer shape to be punched. The support plate 3 thus supports the outer shape in its lateral surface 11 by positive locking. The positive connection is achieved in that the support plate 3 is designed according to the outer shape. The support plate 3 is moved vertically with the control force F _c . It must be stable enough that it can absorb the horizontal forces emanating from the lead frame 6 when cutting.

The device is operated in principle as described for FIGS. 1 and 2. That is, the outer shape is first clamped by means of the ring-shaped holding member 4 and supported laterally by means of the support plate 3, and then punched by means of a punch 1 and counter-holder 8.

The form-fitting lateral support of the shapes to be punched makes it possible to produce round or shaped holes with the smallest diameters and / or web and edge widths in relation to the material thickness. The result is highly smooth perforated walls with the highest degree of measurement accuracy, which cannot be achieved by a conventional drilling, milling or punching process, and at the same time with a long service life of the tool. Examples are shown in Fig. 8 ... 12.

• Das dargestellte Werkzeug dient zur Herstellung von Außenformen mit hochwertigen Schnittflächen aus vorgefertigten Rohlingen.

13 and 14 show a further embodiment of the invention which corresponds to the ones shown in FIGS. 1, 2 and 6, 7 except for the following special features:

• The tool shown is used to manufacture external shapes with high-quality cut surfaces from prefabricated blanks.

The support member 3 here consists of four clamping parts which can be positively and positively attached to the lateral surface 11 of the blank and which are moved with the control force F _c . The holding member 4 is designed as an annular extension of a pressure part connected to the pressure bolts 5.

The clamping parts or the control force F _c support the blank during cutting.

With this tool, parts can be produced as in Figs. 15 ... 18.

15, 16 round blanks 7 are cut out, which can be formed into sleeves, for example, in a subsequent extrusion processing. The lead frame 6, here in the form of a waste ring, has an extremely small edge width A in relation to the material thickness S, for example 30% of S. In this way, in spite of the high-quality cutting surface, substantial material savings are achieved.

17, 18, the stamped part 7 is a gear. The lead frame 6 shown above in FIG. 17 is a waste ring of edge width A with internal teeth. Here too, the edge width A can be made extremely small, so that, despite the excellent quality of the tooth cut surfaces, a remarkable material saving is achieved here.

• So ergibt sich z. B. für eine Kühlschlangenstützplatte aus 20 mm dickem Stahlblech St3 mit den Außenmaßen 2000 mm . 4000 mm und 6000 Löchern von 18 mm Durchmesser eine zu bohrende Länge von 120 m. Es wären für das Bohren 200 Arbeitsstunden erforderlich. Durch Anwendung der Erfindung werden jedoch nur 25 Stunden benötigt.

The invention not only achieves quality improvements and an increase in tool life, but also considerable cost savings in production:

• So there is z. B. for a cooling coil support plate made of 20 mm thick steel sheet St3 with the external dimensions 2000 mm. 4000 mm and 6000 holes of 18 mm diameter a length of 120 m to be drilled. It would take 200 hours to drill. However, using the invention only takes 25 hours.

For the machining of parts in which the web and edge width A is to be particularly small, it is important that the support members 3 are brought into supportive contact with all the parts of the lateral surface 11 of the part whose distance from the cutting line 12 is smaller as the Material thickness S.

When making particularly small holes, the part must be supported as far as possible over its entire circumference. This makes cutting easier and significantly increases the tool life.

Claims (10)

1. Tool for a precision stamping machine for the manufacture of internal and/or external shapes from metallic material, the hole diameter (D) or the land or edge width (A) in the stamping grid (6) being smaller than the material thickness (S), having a cutting plate (2) and a retaining element (4) for clamping the material, and a cutting punch (1) and a pressure pad (8) acting against it, characterised in that the tool does not have a knife-edged ring on either the cutting plate (2) or on the retaining element (4), but provided to the side of the cutting punch by means of a control force (F_c), which supporting element (3) is so designed with respect to its shape and its distance from the cutting punch (1) that, at least during one working stroke of the precision stamping machine, it can be brought into supporting contact outside the cutting line (12) at least with the part of the generated surface (11) of the material to be machined which is nearest totheo cutting line (12).

2. Tool according to claim 1, characterised in that the supporting element (3) can be brought into supporting contact with all parts of the generated surface (11) whose distance (a) from the cutting line (12) is smaller than the material thickness (S).

3. Tool according to claims 1 or 2, characterised in that the cutting punch (1) is surrounded over its complete periphery by one or more supporting elements (3).

4. Tool according to one of claims 1 to 3, for the manufacture of internal shapes from band or strip material, characterised in that the support elements (3) are designed as the supporting punches having the cutting contour of the cutting punch (1) and the retaining element (4) as the retaining plate with holes (9) for the supporting punch, and the supporting punches are movable in the direction of the cutting punch (1) through the holes (9) in the retaining plate as far as the cutting plate (2), and the supporting punches are located evenly distributed around the cutting punch (1), and the holes (9) in the retaining plate have a diameter of 1.02 to 1.06 times the diameter (D) of the penetrating support punch (3).

5. Tool according to one of claims 1 to 3, for the manufacture of internal shapes in prepared external shapes, characterised in that the support element (3) is designed as the support plate concentrically surrounding the cutting punch (1) and movable in its direction and the retaining element (4) is designed as a ring located between the cutting punch (1) and the supporting plate, and the internal recess of the support plate encompassing the cutting punch (1) is so designed that it can be brought into positive connection with the generated surface (11) of the external shape to be machined over the complete periphery.

6. Tool according to claim 4 or 5, characterised in that the shortest distance (A) between the surfaces of the cutting punch (1) and a support punch or the inner recess of the support plate and the surface of the cutting punch (1) lies between ¹/₃ and ²/₃ of the thickness (S) of the material (6) to be cut, and/or the diameter (D) of the cutting punch (1) lies between ²/₃ and ¹/₁ of the thickness (S) of the material (6) to be cut.

7. Tool according to one of claims 1 to 3, for the manufacture of external shapes from prepared blanks, characterised in that the support elements (3) are designed as clamping parts which can be applied positively and with force connection to all sides of the blank and the retaining element (4) is designed as the ring located between the cutting tool (1) and the clamping parts.

8. Method for operating a tool according to claim 4 or 6 for the purpose of manufacturing perforated sheets from metallic material, wherein the retaining plate is first pressed with a retaining force (F_H) onto the material to be machined and the cutting punch (1) is then pressed, with a cutting force (F_s) against the counterforce (F_c) of the pressure pad (8), through the material as far as the cutting plate (2) and is then withdrawn again, characterised in that the retaining plate is then released from the material and the latter displaced until the hole cut (10) comes to rest under a support punch, and the support punch is then driven into the hole cut (10) as far as the cutting plate (2), the material being subsequently clamped by means of the retaining plate and, finally, a new hole (10) is cut by means of the cutting punch (1) and the pressure pad (8).

9. Method for operating a tool according to claim 5 or 6 for the purpose of manufacturing a hole in a finished external shape of a metallic material, wherein the cutting punch (1) is pressed, with a cutting force (F_s) against the counterforce (F_G) of the pressure pad (8), as far as the cutting plate (2) through the material (6) to be cut and is then withdrawn, characterised in that before the cutting punch (1) takes effect, the external shape is clamped by means of the support plate using the positive connection of the support element (4), and the removal of the perforated external shape from the tool takes place after the release of the retaining element (4) and the support plate.

10. Method for operating a tool according to claim 7 for the purpose of manufacturing an external shape from a prepared blank in metallic material, wherein the cutting punch (1) is pressed, with a cutting force (F_s) against the counter-force (F_G) of the pressure pad (8), as far as the cutting plate (2) through the blank and is then withdrawn again, characterised in that the blank is clamped by means of the clamping parts using positive and force connection, and the retaining element (4) is clamped with a retaining force (F_H), and the removal of the punching grid (6) from the tool occurs after the release of the retaining elements (4) and the clamping parts.

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