EP2848329B1 - Method and device for precision cutting of workpieces in a press - Google Patents

Description

The invention relates to a method and a precision cutting tool for the precision cutting of workpieces in a press according to the preamble of the independent claims 1 and 5.

With the DE 10 2005 045 454 B4 a press and a method for hard cutting has become known in which in a press tool at least one spacer element is provided which forms a fixed stop for the press movement. The press works with upper and lower tools, which are each driven by a hydraulic pressurization, which is associated with the disadvantage that the upper and lower tools must be supplied with separate oil circuits.

In another embodiment of this document, the force generator for generating the contact pressure of the upper and lower tools are formed from mechanical spring elements. An active press tool is thus not given. These press tools work only passively, according to the stroke between the press ram and the press table. The said spring elements are therefore passive, that is, they are uncontrolled and generate only a certain pressure without a control is shown as the pressure force is controlled to achieve a specific control or regulation of the press tools.

With the subject of DE 199 08 603 C1 Another press has become known which achieves cutting with a constant cutting depth.

When the lower tool counter punch is supported with a discharge spring. The lower punch has, moreover, an end stop in the lower tool; Accordingly, the workpiece is cut against a fixed stop of the counter-holder in the lower tool.

Because of the uncontrolled ejection spring, the spring characteristic is not influenced, there is the disadvantage that when you open the press, the ejection spring presses in the counter-holder in the direction of the hold in the upper die, and thus the punching waste into the originally punched board again.

Accordingly, there is no need for a controlled movement of the force unit biasing the anvil.

With the EP 0 131 770 A1 In general, the principle of fine blanking is shown with a ring point, which is impressed by the hold-down in the workpiece.

Although the used DD 293 752 A5 a spring assembly in the area of the tool lower part, but it is an uncontrolled force generator, which is not able to control the punching waste to remove from the work area of the press.

In summary, the cited prior art can be divided into presses that operate with hydraulic drive elements, which is associated with the disadvantage that with the leadership of the hydraulic circuits and the associated valves a great effort is associated with high costs.

The second part of the publications relates to purely mechanical presses, but in which the press tools are hydraulically driven. This is especially true of the DE 10 2005 045 454 B4 refer to.

The WO 87/02916 A1 discloses a method for precision cutting of workpieces with a press consisting of a press frame, in whose press opening a press ram is movably driven, which against a Press table works, wherein at least one of the press tool is formed as a cutting tool, which consists of at least a cutting punch, a hold-down, a cutting die and a counter-holder, the cutting tool works as a precision cutting tool, the lower tool part consists of a controlled retention module, the counter-holder in a certain Press ram position holds back to allow ejection of the waste, wherein the tool holder disposed in the lower part counterpart is supported on a hydraulic energy accumulator, the pressure force of which is variable by a hydraulic accumulator and a pressure accumulator connected to the check valve.

Similar methods operating with hydraulic elements are disclosed in WO 2009/002176 A1 or DE 15 52 049 A1 or US 3 211 034 A disclosed. The object of the invention is to develop a method and a device for precision cutting of workpieces in a press so that a more precise control of the restraint module is possible.

To achieve the object, the invention by a method and a precision cutting tool according to the objects of the independent claims 1 and 5 is characterized.

It is known that fine blanking is a production method for chipless cutting and, optionally, simultaneous metal forming. It allows the production of high-precision parts. In contrast to the normal punching, the raw material of the cutting contour is held in fine cutting by means of a so-called ring point. Only then does a stamp with the desired shape cut the metal. In conjunction with a significantly reduced cutting gap (about 0.5% of the sheet thickness) to reach a cylindrical section of up to 100% of the sheet thickness. Optionally, transformations or embossing on the metal can be carried out in further steps within the same operation. Therefore, more and more of fineblanking / forming is spoken.

The invention is not limited thereto. The invention allows a precision cutting tool with which a simple punching of material can be performed by means of a cutting die.

Likewise, other forming operations can be carried out with the precision cutting tool according to the invention, so that the term "precision cutting tool" according to the invention in general terms on a fine blanking / punching / forming refers. All three options are provided in combination with one another or in isolation with the precision cutting tool according to the invention.

By using a pressure accumulator, which acts only on the underside spring pack in the manner of a piston, there is the advantage that it is possible to dispense with hydraulic circuits, a hydraulic pump, hydraulic oil or elaborate control elements. Instead, it is a simple pressure accumulator, which does not necessarily work with a hydraulic oil. There are also pneumatic accumulator possible. As a result, can dispensed with a complex and repair-prone high-pressure pump, because only a pressure accumulator is present, which is alternately controlled filled or emptied according to the working cycles of the press, and then transferred due to the automatic recovery (relaxation) of the spring assembly in its original filling state.

The precision cutting tool according to the invention is therefore not dependent on the drive elements of the press. It works completely autonomously, which means that the press itself can work by any method. It may thus be a hydraulic or a mechanical or a servo-motor driven press or other drive kinematics of a press, which play no role in the present invention, because the drive elements of the press are completely independent of the drive elements of the precision cutting tool.

Accordingly, the features of the invention provide the first advantage that the precision cutting tool can be used in any presses with any drive principles, and does not depend on the type of press. Instead of a conventional tool in a press can therefore be used as another tool autonomous precision cutting tool according to the invention. It can be modularly installed with other tools in the press room, without relying on the kinematics and the drive of the press itself.

Important in the invention is therefore that the counter-holder of the lower tool is associated with a preferred mechanical disc spring package, which communicates with a restraint module via a pressure chamber. The retention module according to the invention consists of a rechargeable pressure accumulator in conjunction with a check valve arranged in the flow path, the opening and closing state of which is controlled as a function of the press stroke.

Such a retention module consisting of the pressure accumulator and the controllable check valve can be arranged in the press tool itself or at any distance from the precision cutting tool - even outside the press. The pressure accumulator is a pressure vessel, which is filled with a pressure medium, such as air, gas or a hydraulic medium (water or oil), and should control a pressure of about 100 to 250 bar.

Important in this printing module is that the pressure force of the stored there pressure medium is sufficient to counteract the spring force of the spring assembly to retain this in a certain process position of the precision cutting tool.

The subject of the present invention results not only from the subject matter of the individual claims, but also from the combination of the individual claims with each other.

In the following the invention will be explained in more detail with reference to drawings showing only one embodiment.

• Figur 1: schematisiert dargestellte Presse mit einer Anzahl von Pressenwerkzeugen
• Figur 2: das Präzisionsschneidwerkzeug nach Figur 1 in einer vergrößerten Darstellung
• Figur 3: die Stellung 0 des Schneidwerkzeuges
• Figur 4: die Stellung 1 des Schneidwerkzeuges
• Figur 5: die Stellung 2 des Schneidwerkzeuges
• Figur 6: die Stellung 3 des Schneidwerkzeuges
• Figur 7: die Stellung 4 des Schneidwerkzeuges
• Figur 8: die Stellung 5 des Schneidwerkzeuges
• Figur 9: die Stellung 6 des Schneidwerkzeuges

Show it:

• FIG. 1 : schematically illustrated press with a number of press tools
• FIG. 2 : the precision cutting tool after FIG. 1 in an enlarged view
• FIG. 3 : the position 0 of the cutting tool
• FIG. 4 : the position 1 of the cutting tool
• FIG. 5 : the position 2 of the cutting tool
• FIG. 6 : the position 3 of the cutting tool
• FIG. 7 : the position 4 of the cutting tool
• FIG. 8 : the position 5 of the cutting tool
• FIG. 9 : the position 6 of the cutting tool

In FIG. 1 is generally shown that a press 1 of any kind having a press frame 2, in the press opening 3, a press ram 4 is arranged movably on any drive elements 5 in the arrow directions 6.

By way of example, a number of press tools are arranged in the opening of the press frame 2; the type and number of press tools is arbitrary. It can be arranged in the opening 3 of the press frame 2 only a single press tool, but also a plurality of press tools.

As an example, it is indicated in the present case that the first press tool consists of a tool upper part 8 with an associated lower tool part 12.

The lower tool part 12 is fastened in each case on the upper side of the press table 7. The second press tool consists of the upper tool part 9 and the lower tool part 13, the third press tool consists of the upper tool part 10 and the lower tool part 14. In the drawing FIG. 1 the passage direction of the workpiece to be machined in the press 1 in subsequent steps is shown. It is first processed in the tool 8, 12, then passes with the next power stroke in the tool 9, 13 and with the third power stroke in the tool 10, 14th

Important in the invention is that as an additional tool - either alone or in combination with other tools - an inventive precision cutting tool 17 is arranged in the press frame 2. It consists of a tool upper part 11 and a tool lower part 15 arranged on the press table 7. In the exemplary embodiment shown, the precision cutting tool 17 is arranged at the end of the machining chain, on the right side of the press frame 2.

The invention is not limited thereto. The precision cutting tool 17 may be installed alone in a press 1 or in any order with the press tools 8, 12; 9, 13; 10, 14 alternate. Also, more than one precision cutting tool 17 may be arranged.

It is essential in the invention that the lower tool part 15 of the precision cutting tool 17 is active, that is, it has an active retaining module 34 capable of holding the anvil 24 (see FIG FIG. 2 ) in a certain press position to allow ejection of the waste 23.

This is based on the FIG. 2 explained in more detail.

FIG. 2 shows that in the tool upper part 11 one or more receptacles for a spring assembly 18 are arranged. The respective spring package is prefers disc springs. Instead of such disc springs and other power storage can be used, such as hydraulic elements, mechanical springs, such as helical compression springs, spiral or wedge springs or the like.

The spring assemblies 18 act via associated pressure elements on a hold-down 20. Directly with the upper tool 11 a cutting punch 19 is connected.

In between, a workpiece 21 is arranged, which forms a central waste piece, which is to be removed after the cutting out of the workpiece 21 controlled as waste 23 from the press room.

In the lower tool part 15, a counter-holder 24 is arranged, which carries a hydraulic piston 25 on its underside, which engages with a pressure plate 29 in a hydraulic cylinder. Above the pressure plate 29, a pressure chamber 32 is formed, which is under the pressure of a pressure accumulator 28, wherein a controllable check valve 27 is liquid or air conductively connected to the pressure chamber 32.

In addition, the upper and lower tool parts can also be exchanged in their function, which would mean cutting upwards with ejection downwards. Similarly, the waste designated at 23 may represent the workpiece and 21 the waste depending on the component design.

The pressure plate 29 is supported on the underside by a force accumulator, which is formed in the preferred embodiment as a disc spring assembly 26. The invention is not limited thereto.

Instead of a disc spring package, all other hydraulic, pneumatic or mechanical energy storage can be used. However, the use of a spring pack 26 is preferred because no hydraulic drive elements, high pressure pumps or the like must be used. As a result, the lower tool part 15 actively works with the aid of the restraint module 34 formed by the pressure accumulator 28 and the check valve 27 and does not depend on the press stroke of the press 1.

In the FIGS. 3 to 9 a complete workflow is shown in the operation of the precision cutting tool 17.

In the FIG. 3 the position 0 is shown. The press ram 4 is in its TDC and the press room is open. The workpiece 21 is exposed on the tool lower part 15, and the retaining module 34 is closed, which means that the pressure accumulator 28 is filled and under pressure, wherein the check valve 27 is closed. This is represented by the solid line with the closed state 30.

In position 1 after FIG. 4 moves the press ram 4 in the direction of arrow 6 down and closes the press room. As a result, the hold-down 20 sets on the workpiece 21, and the cutting punch 19 rests on the top of the workpiece 21.

In this position, the pressure accumulator in the restraint module 34 is closed. In position 2, the press ram 4 moves on FIG. 5 down in the direction of arrow 6, whereby the cutting punch 19, the workpiece 21 is severed and a central waste piece 23 is formed. The spring assembly 18 is thereby biased. The hold-down 20 clamped under the action of the spring assemblies 18, the workpiece 21 before the cutting punch 19 performs the cutting operation on the workpiece 21.

With the downwardly moving counter-holder 24, the hydraulic piston 25 is also driven with its pressure plate 29 in the hydraulic cylinder in the tool lower part 15, whereby the pressure chamber 32 expands, and thus sucks the pressure medium at automatically open in this closed state check valve 27 from the pressure accumulator 28.

In position 3 after FIG. 6 the cut state of the workpiece is shown. The waste 23 is on the anvil 24 and the bottom dead center of the press is reached. In this state, the maximum filling state of the pressure chamber 32 is reached, and thus the pressure accumulator 28 is maximally emptied. The check valve 27 is in its closed state 30. This is in contrast to the in FIG. 5 illustrated open state 31.

When returning the press ram 4 in the direction of arrow 6 ', the check valve 27 remains in the closed state 30; the hold-down 20 is relieved and the cutting punch 19 moves away from the waste 23. This creates an exemption 33 in the region of the now cut workpiece 21.

In position 5, the press ram 4 moves further in the direction of arrow 6 'upwards, whereby the press room is increased. The hold-down 20 has no contact with the cut workpiece and the cut-out waste 23. The check valve 27 remains closed in its closed state 30, and the finished cut workpiece 21 is removed in the direction of arrow 35.

In position 6 after FIG. 9 the cut-out waste 23 remains on the top of the counter-holder 24, the press ram 4 has reached its top dead center (TDC), the check valve 27 is in its open state 36, the opposite of the liquid flow after FIG. 5 is; the pressure chamber 32 is now slowly emptied by the spring force of the spring assembly 26; Consequently In the open state 36, the oil flows back through the open check valve 27 back into the pressure accumulator 28.

This has the consequence that the counter-holder 24 in its original position to position 0 according to FIG. 3 starts up, and the waste 23 is above the cutting surface and can be easily removed.

Advantage of the method according to the invention and the method practicing the method is that the tool technology of the precision cutting tool can be accommodated in any press design, without being acted upon or dependent on the press drive elements themselves. The method according to the invention allows a smooth cut portion of more than 70% of the vertical cut surface, while in normal cutting it is known that a smooth cut portion of about 30% and 70% break surface in the cut surface can be realized.

The illustrated design of the precision cutting tool is cheaper compared to the usual, hydraulically driven precision cutting tools, and it can very high stroke rates are achieved with over 80 strokes per minute, which is possible with hydraulically driven precision cutting tools only with much higher cost and significantly higher costs.

The invention is therefore distinguished by a precision cutting tool having a hydraulic piston in the region of its counter-holder, which cooperates with a hydraulic cylinder having on its one side a pressure chamber for a pressure accumulator, and on its opposite side has a preferably mechanical energy storage. This is a self-sufficient precision cutting tool, which actively performs a restraining movement for the counter-holder in a specific working cycle without such a movement being dependent on the press elements themselves.

The opening and closing movement of the check valve is controlled by the movement of the press ram 4. For this purpose, any controls may be used, such as mechanical or electronic Wegmesselemente and associated control devices and an electronic coupling with the press control, which also evaluates the position of the press ram. The entire precision cutting tool is due to its minority of moving parts low maintenance, especially because it can be dispensed with hydraulically driven elements.

drawing Legend

1

Press

2

press frame

3

opening

4

press ram

5

driving element

6

Arrow direction 6 '

7

press table

8th

Upper die

9

Upper die

10

Upper die

11

Upper die

12

Tool part

13

Tool part

14

Tool part

15

Tool part

16

Hinweispfeil

17

Precision cutting tool (active)

18

spring assembly

19

cutting punch

20

Stripper plate

21

workpiece

22

cutting die

23

waste

24

backstop

25

hydraulic pistons

26

spring assembly

27

check valve

28

accumulator

29

printing plate

30

closing state

31

open state

32

pressure chamber

33

exemption

34

Restraint module

35

arrow

36

open state

Claims (7)

1. Method for precision cutting of workpieces with a press (1) comprising a press frame (2) in the press opening (3) of which a press ram (4) which operates against a press table (7) is movably driven, wherein at least one of the press tools (8, 12; 9, 13; 10, 14; 11, 15; 17) is designed as a cutting tool which comprises at least a cutting punch (19), a hold-down device (20), a cutting die (22) and a counter holder (24), wherein the cutting tool operates as a precision cutting tool (17) the lower part (15) of which comprises a controlled retaining module (34) which retains the counter holder (24) in a given press ram position in order to enable ejection of the waste (23), wherein the counter holder (24) arranged in the lower part (15) of the tool carries on its lower side a hydraulic piston (25) which engages with a pressure plate (29) in a hydraulic cylinder, wherein the lower side of the pressure plate (29) is supported on an energy-storing device (26) the compressive force of which is variable by a pressure accumulator (28) containing a pressure medium and a non-return valve (27) connected to the pressure accumulator (28), characterised in that the energy-storing device is designed as a spring assembly (26) or as a pneumatic energy-storing device, wherein above the pressure plate (29) is formed a pressure chamber (32) which is under the pressure of the pressure accumulator (28) which is connected to the pressure chamber (32) in liquid-conducting or air-conducting relationship via the controllable non-return valve (27) in such a way that with the downwardly travelling press ram the counter holder (24) and at the same time the hydraulic piston (25) with its pressure plate (29) is moved into the hydraulic cylinder in the lower part (15) of the tool, whereby the pressure chamber (32) expands and hence draws the pressure medium out of the pressure accumulator (28) when the non-return valve (27) in this closed state (30) is automatically opened, and when the press ram (4) travels upwards the non-return valve (27) moves to its open state (36), wherein the pressure chamber (32) is now slowly emptied by the spring force of the spring assembly (26), and the pressure medium in the open state (36) flows back through the open non-return valve (27) into the pressure accumulator (28), wherein the counter holder (24) travels up to its original position.
2. Method according to claim 1, characterised in that the precision cutting tool (17) performs a retaining movement for the counter holder (24) in a given working stroke without such a movement being dependent on the press components or active devices external to the tool (e.g. hydraulic unit) themselves.
3. Method according to claim 1 or 2, characterised in that a mechanically operating plate spring assembly or other mechanical energy-storing device (26) is used as the element which supports the counter holder (24), the force characteristic of which is variable by the pressure accumulator (28) and the non-return valve (27) cooperating with the pressure accumulator (28) and the press ram position.
4. Method according to one of claims 1 to 3, characterised in that the precision cutting tool operates autonomously, and actively performs a retaining movement for the counter holder (24) in a given working stroke without such a movement being dependent on the press components themselves.
5. Precision cutting tool (17) suitable for installation in a press frame (2) in the press opening (3) of which a press ram (4) which operates against a press table (7) is movably driven, which comprises at least a cutting punch (19), a hold-down device (20), a cutting die (22) and a counter holder (24), wherein the counter holder (24) arranged in the lower part (15) of the tool carries on its lower side a hydraulic piston (25) which engages with a pressure plate (29) in a hydraulic cylinder, wherein the lower side of the pressure plate (29) is supported on an energy-storing device (26) the compressive force of which is variable by a pressure accumulator (28) and a non-return valve (27) connected to the pressure accumulator (28), characterised in that the energy-storing device is designed as a spring assembly (26) or as a pneumatic energy-storing device, wherein above the pressure plate (29) is formed a pressure chamber (32) which is under the pressure of the pressure accumulator (28) which is connected to the pressure chamber (32) in liquid-conducting or air-conducting relationship via the controllable non-return valve (27).
6. Press for precision cutting of workpieces having a precision cutting tool according to claim 5.
7. Press according to claim 6, characterised in that the open and closed states of the non-return valve (27) are controlled as a function of the press stroke or press ram position.

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