Method and device for precision cutting of workpieces in a press

Abstract

A method for precision cutting of workpieces using a press which includes a press frame, in the press opening of which press frame a press ram, that works against a press table, is movably driven, wherein at least one of the press tools is formed as a cutting tool that includes a cutting punch, a downholder, a cutting die and a counter support. The cutting tool operates as a precision cutting tool. A lower tool part of the cutting tool includes a controlled retaining module that retains the counter support in a certain press ram position to enable ejecting the scrap.

Claims

1. A press for precision cutting of workpieces using a press frame, comprising: a press ram disposed in a press opening of the press frame, a press table movably driven to work against the press ram, press tools connected to the press ram and the press table, wherein at least one of said press tools comprises a precision cutting tool that comprises: an upper tool part and a lower tool part; a spring pack arranged in the upper tool part; a cutting punch for cutting a workpiece into a workpiece product and a scrap piece; a downholder connected to the spring pack and to the cutting punch to clamp the workpiece in place and position the cutting punch on the workpiece for cutting during use responsive to action of a biasing force of the spring pack; a cutting die secured to the lower tool part and on which the cutting punch acts when the workpiece is being cut on a cutting surface; a counter support arranged on the lower tool part disposed so as to receive the scrap and move downwardly within the lower tool part below and out of the plane of the cutting surface; an energy storage supporting the counter support and arranged in the lower tool part, the energy storage configured and operable to cause the counter support to move between a first position coincident with the cutting surface and a second position below and out of the plane of the cutting surface via a fluid; a pressure accumulator in fluid communication with the energy storage to pressurize the fluid in the energy storage to control the energy storage to move the counter support between the first and second positions; a check valve connected to the pressure accumulator to vary a compressive force on the energy storage causing the energy storage to move independently of a press stroke of the press ram; an enclosed energy store chamber; a pressure plate; a cylinder connected between the pressure plate and the counter support; a spring pack disposed in the enclosed energy store chamber and supporting the pressure plate; and a pressure chamber separated from the energy store chamber by the pressure plate, the pressure accumulator being in fluid communication with the pressure chamber, wherein the fluid runs into the pressure chamber from the pressure accumulator, wherein the press is configured such that on downward stroke of the press ram in a direction toward the press table, the spring pack is compressed, in the upper tool part, and fluid runs into the energy storage from the pressure accumulator at the same time, wherein on the up stroke of the press ram in a direction away from the press table, the counter support is driven upwards by the energy storage, and wherein the fluid stored in the pressure accumulator controls movement of the counter support in the upward stoke of the press ram.

2. The press according to claim 1, wherein the energy storage is formed as a plate spring pack.

3. The press according to claim 1, further comprising a piston-cylinder unit connected between the counter support and the energy storage to enable the counter support to act on the energy storage.

4. The press according to claim 1, wherein open and closed states of the check valve are controlled in dependence on a press stroke or the press ram position.

5. The press according to claim 1, wherein the cutting tool comprises: a hydraulic cylinder formed in the lower tool part, a hydraulic piston connected to a lower side of the counter support, a pressure plate connected to the hydraulic piston that engages into the hydraulic cylinder, a pressure chamber formed above the pressure plate, that is pressurized by the pressure of the pressure accumulator, wherein the check valve is connected to the pressure chamber in a fluid- or air-conducting manner to control the pressure in the pressure chamber.

6. A precision cutting tool which is suitable for mounting into a press frame, the press frame having a press opening, and a press ram, that works against a press table, being movably driven in the press opening, and which comprises: an upper tool part and a lower tool part; a spring pack arranged in the upper tool part; a cutting punch for cutting a workpiece into a workpiece product and a scrap piece; a downholder connected to the spring pack and to the cutting punch to clamp the workpiece in place and position the cutting punch on the workpiece for cutting during use responsive to action of a biasing force of the spring pack; a cutting die secured to the lower tool part and on which the cutting punch acts when the workpiece is being cut on a cutting surface; a counter support arranged on the lower tool part disposed so as to receive the scrap and move downwardly to move the scrap within the lower tool part below and out of a plane of the cutting surface; an energy storage supporting the counter support and arranged in the lower tool part, the energy storage configured and operable to cause the counter support to move between a first position coincident with the cutting surface and a second position below and out of the plane of the cutting surface via a fluid, a pressure accumulator in fluid communication with the energy storage to pressurize the fluid in the energy storage to control the energy storage to move the counter support between the first and second positions; and a check valve connected to the pressure accumulator to vary a compressive force on the energy storage causing the energy storage to move independently of a press stroke of the press ram; an enclosed energy store chamber; a pressure plate; a cylinder connected between the pressure plate and the counter support; a spring pack disposed in the enclosed energy store chamber and supporting the pressure plate; and a pressure chamber separated from the energy store chamber by the pressure plate, the pressure accumulator being in fluid communication with the pressure chamber, wherein the fluid runs into the pressure chamber from the pressure accumulator, wherein the press is configured such that on downward stroke of the press ram in a direction toward the press table, the spring pack is compressed, in the upper tool part, and the fluid runs into the energy storage from the pressure accumulator at the same time, wherein on the up stroke of the press ram in a direction away from the press table, the counter support is driven upwards by the energy storage, and wherein the fluid stored in the pressure accumulator controls movement of the counter support in the upward stoke of the press ram.

7. The precision cutting tool according to claim 6, wherein the energy storage is a spring pack.

8. The precision cutting tool according to claim 6, wherein the energy storage is a plate spring pack.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures:

(2) FIG. 1 shows a schematically illustrated press with a number of press tools;

(3) FIG. 2 shows the precision cutting tool according to FIG. 1 in an enlarged illustration;

(4) FIG. 3 shows the position 0 of the cutting tool;

(5) FIG. 4 shows the position 1 of the cutting tool;

(6) FIG. 5 shows the position 2 of the cutting tool;

(7) FIG. 6 shows the position 3 of the cutting tool;

(8) FIG. 7 shows the position 4 of the cutting tool;

(9) FIG. 8 shows the position 5 of the cutting tool; and

(10) FIG. 9 shows the position 6 of the cutting tool.

DETAILED DESCRIPTION

(11) FIG. 1 generally illustrates that a press 1 of any kind has a press frame 2, in the press opening 3 of which a press ram 4 is arranged to be movable via any drive elements 5 in the direction of the arrow 6.

(12) As an example, a number of press tools are arranged in the opening of the press frame 2; the press tools can be of any type or number. It is possible that only a single press tool is arranged in the opening 3 of the press frame 2, but it is also possible that a multiplicity of press tools is arranged therein.

(13) In the present case, it is shown as an example that the first press tool consists of an upper tool part 8 with an associated lower tool part 12.

(14) The lower tool part 12 is in each case fastened 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 FIG. 1, the transfer direction of the workpiece to be processed in the press 1 in sequential steps is illustrated. First, the workpiece is processed in tool 8, 12, is transferred with the next work cycle into the tool 9, 13 and with the third work cycle into the tool 10, 14.

(15) It is important for the invention that a precision cutting tool 17 according to the invention is arranged in the press frame 2 as a further tooleither alone or in combination with other tools. It consists of an upper tool part 11 and of a lower tool 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 processing chain, on the right side of the press frame 2.

(16) The invention is not limited thereto. The precision cutting tool 17 can be installed alone in a press 1 or can alternate in any order with the press tool 8, 12; 9, 13; 10, 14. It is also possible that more than one precision cutting tool 17 is arranged therein.

(17) It is essential for the invention that the lower tool part 15 of the precision cutting tool 17 operates actively, that is, it has an active retaining module 34 that is capable of retaining the counter support 24 (see FIG. 2) in a certain press position in order to enable ejecting of scrap 23.

(18) This is explained in greater detail by means of FIG. 2.

(19) FIG. 2 shows that one or more receptacles for a spring pack 18 are arranged in the upper tool part 11. The respective spring pack preferably comprises plate springs. Instead of such plate springs, other energy storages can also be used such as, for example, hydraulic elements, mechanical springs such as, for example, helical compression springs, spiral or coiled springs or the like.

(20) The spring packs 18 act via associated pressure elements onto the downholder 20. A cutting punch 19 is directly connected to the upper tool part 11.

(21) The cutting punch 19 acts with its cutting edges on a cutting die 22 that is secured on the lower tool part 15. Therebetween, a workpiece 21 is arranged that forms in the middle a piece of scrap that is to be removed in a controlled manner as scrap 23 from the pressing area after cutting out the workpiece 21 is completed.

(22) A counter support 24 is arranged in the lower tool part 15, which counter support carries on its lower side a hydraulic cylinder which engages by means of a pressure plate 29 into a hydraulic cylinder. Above the pressure plate 29 there is a pressure chamber 32 that is pressurized by the pressure of a pressure accumulator 28, wherein a controllable check valve 27 is connected to the pressure chamber 32 in a fluid- or air-conducting manner.

(23) Furthermore, the upper tool part and the lower tool part can switch their functions which would mean that cutting takes place upwards and ejection takes place downwards. Likewise, depending on the component formation, the scrap designated by 23 can represent the workpiece, and 21 can represent the scrap.

(24) The pressure plate 29 is supported on the lower side by an energy storage which, in the preferred exemplary embodiment, is designed as a plate spring pack 26. The invention is not limited thereto.

(25) Instead of a plate spring pack, any other hydraulic, pneumatic or mechanical energy storages can be used. However, use of a spring pack 26 is preferred, because no hydraulic drive elements, high pressure pumps or the like have to be used. This results in that the lower tool part 15 operates actively with the aid of the retaining module 34 formed from the pressure accumulator 28 and the check valve 27 and is not dependent on the press stroke of the press 1.

(26) In the FIGS. 3 to 9, a complete workflow during the operation of the precision cutting tool 17 is illustrated.

(27) FIG. 3 shows the position 0. The press ram 4 is in its TDC and the pressing area is open. The workpiece 21 lies freely on the lower tool part 15 and the retaining module 34 is closed, which means that the pressure accumulator 28 is filled and is pressurized, wherein the check valve 27 is closed. This is illustrated by the solid line with the closed state 30.

(28) In position 1 according to FIG. 4, the press ram travels downwards in the direction of the arrow 6 and closes the pressing area. As a result of this, the downholder 20 is placed onto the workpiece 21 and the cutting punch 19 rests on the upper side of the workpiece 21.

(29) In this position, the pressure accumulator in the retaining module 34 is closed. In the position 2, the press ram 4 according to FIG. 5 travels further downwards in the direction of the arrow 6, as a result of which the cutting punch 19 cuts through the workpiece 21 and forms a central piece of scrap 23. Thereby, the spring pack is preloaded. Under the action of the force of the spring packs 18, the downholder clamps the workpiece 21 before the cutting punch 19 performs the cutting operation on the workpiece 21.

(30) While the counter support 24 travels downwards, the hydraulic piston 25 with its pressure plate 29 travels at the same time into the hydraulic cylinder in the lower tool part 15 so that the pressure chamber 32 expands and thus suctions the pressure medium from the pressure accumulator 28 with the check valve 27 being automatically open in this closed state.

(31) In the position 3 according to FIG. 6, the cut state of the workpiece is illustrated. The scrap 23 lies on the counter support 24, and the bottom dead center of the press is therefore reached. In this state, the maximum filling level of the pressure chamber 32 is reached and the pressure accumulator is therefore maximally emptied. The check valve 27 goes into its closed state 30. This is contrary to the open state 31 illustrated in FIG. 5.

(32) When the press ram 4 travels back in the direction of the arrow 6, the check valve 27 remains in the closed state 30; the downholder 20 is released and the cutting punch 19 moves away from the scrap 23. This results in a released position 33 in the region of the workpiece 21 which is now cut out (FIG. 7).

(33) In position 5 (FIG. 8), the press ram 4 travels further upwards in the direction of the arrow 6, thereby increasing the pressing area. The downholder 20 is no longer in contact with the cut workpiece and the cut scrap 23. The check valve 27 remains in its closed position 30 and the finish-cut workpiece 21 is removed in the direction of the arrow 35.

(34) In the position 6 according to FIG. 9, the cut out scrap 23 remains on the upper side of the counter support 24, the press ram 4 has reached its top dead center (TDC), the check valve 27 returns into its open state 36 which is contrarily to the fluid flow according to FIG. 5; the pressure chamber is now slowly emptied by the spring force of the spring pack 26; thus, the oil flows in the open state 36 through the open check valve 27 back into the pressure accumulator 28.

(35) This results in that the counter support 24 travels upwards in its initial position to position 0 according to FIG. 3, and the scrap 23 lies above the cutting surface and can be removed without any problems.

(36) An advantage of the method according to the invention and the device carrying out the method is that the tool technology of the precision cutting tool can be accommodated in any press design without being acted on by or being dependent on the press drive elements themselves. The method according to the invention enables a smooth cut portion of more than 70% of the vertical cut surface, whereas with normal cutting, as is well known, a smooth cut portion of approximately 30% and a fractured surface of 70% in the cutting surface can be implemented.

(37) The illustrated construction of the precision cutting tool is more cost-effective compared to conventional, hydraulically driven precision cutting tools, and very high numbers of stroke with more than 80 strokes per minute can be achieved, which, when using hydraulically driven precision cutting tools, is possible only with significantly higher effort and significantly higher costs.

(38) Thus, the invention is characterized by a precision cutting tool which, in the region of its counter support, has a hydraulic piston that interacts with a hydraulic cylinder which on one of its sides has a pressure chamber for a pressure accumulator, and on its opposing side it has a preferably mechanical energy storage. This is an autonomous precision cutting tool which actively performs a retention movement for the counter support in a certain work cycle, without such a movement being dependent on the press elements themselves.

(39) The opening and closing movement of the check valve is controlled by the movement of the press ram 4. For this, any control elements can be used such as, for example, mechanical or electronic position measuring elements and associated control devices, as well as electronic coupling to the press controller which likewise evaluates the position of the press ram. Due to its small number of movable parts, the entire precision cutting tool is low-maintenance, in particular because hydraulically driven elements can be dispensed with.

(40) According to one embodiment more fully described above, a method for precision cutting of workpieces using a press (1) comprises a press frame (2), a press ram disposed in the press opening (3) of which press frame (4), a press table (7) against which the press ram works, the press ram being movably driven, a plurality of press tools, at least one of the press tools (8, 12; 9, 13; 10, 14; 11, 15; 17) is being formed as a cutting tool that comprises at least of a cutting punch (19), a downholder (20), a cutting die (22) and a counter support (24), wherein the cutting tool operates as a precision cutting tool (17), the lower tool part (15) comprises a controlled retaining module (34) that retains the counter support (24) in a certain press ram position to enable ejecting of the scrap (23). The method comprises providing an energy storage to support the counter support (24) arranged in the lower tool part (15) (25, 26, 29, 32), and varying compressive force of the energy storage using a pressure accumulator (28) and a check valve (27) that is connected to the pressure accumulator (28).

(41) According to one embodiment, the method further comprises performing a retaining movement using the precision cutting tool (17) for the counter support (24) in a certain work cycle, said movement being independent of the press tools or tool-external active devices (e.g. hydraulic aggregate) themselves.

(42) According to one embodiment, a mechanically acting plate spring pack or other mechanical energy storages (26) is used as an element supporting the counter holder (24), wherein the method further comprises varying force characteristics of said element by the pressure accumulator (28) and the check valve (27) interacting with the pressure accumulator (28) and by a position of the press ram.

(43) According to one embodiment, a press for precision cutting of workpieces using a press frame (2) is provided, comprising a press ram (4) disposed in a press opening of the press frame, a press table (7) movably driven to work against the press ram (4), and press tools (8, 12; 9, 13; 10, 14; 11, 15; 17) connected to the press ram and the press table. At least one of the press tools is formed as a cutting tool that comprises a cutting punch (19), a downholder (20), a cutting die (22) and a counter support (24). The cutting tool operates as a precision cutting tool (17) and comprises an energy storage (25, 26, 29, 32) supporting the counter support (24) arranged in a lower tool part (15), a pressure accumulator (28), and a check valve (27) connected to the pressure accumulator to vary a compressive force of the energy storage (25, 26, 29, 32).

(44) According to one embodiment, the energy storage is formed as a plate spring pack (26).

(45) According to one embodiment, the press further comprises a piston-cylinder unit (25, 29, 32) connected between the counter support (24) and the energy storage to enable the counter support (24) to act on the energy storage.

(46) According to one embodiment, open and closed states of the check valve (27) are controlled in dependence on a press stroke or the press ram position.

(47) According to one embodiment, the cutting tool comprises a hydraulic cylinder (26) formed in the lower tool part (15), a hydraulic piston (25) connected to a lower side of the counter support (24), a pressure plate (29) connected to the hydraulic piston (25) that engages into the hydraulic cylinder (26), and a pressure chamber (32) formed above the pressure plate (29), that is pressurized by the pressure of the pressure accumulator (28). The check valve (27) is connected to the pressure chamber (32) in a fluid- or air-conducting manner to control the pressure in the pressure chamber (32).

(48) According to one embodiment, a precision cutting tool (17) is provided which is suitable for mounting into a press frame (2), in the press opening (3) of which press frame a press ram (4), that works against a press table (7), is movably driven, and which comprises a cutting punch (19), a downholder (20), a cutting die (22) and a counter support (24), wherein the counter support (24) arranged in a lower tool part (15) is supported on an energy storage (25, 26, 29, 32), the compressive force of which can be varied by a pressure accumulator (28) and a check valve (27) connected to the pressure accumulator (28).

(49) According to one embodiment, in the precision cutting tool (17), the energy storage is a spring pack, in particular a plate spring pack.

REFERENCE LIST

(50) 1 Press 2 Press frame 3 Opening 4 Press ram 5 Drive element 6 Direction of arrow 6 7 Press table 8 Upper tool part 9 Upper tool part 10 Upper tool part 11 Upper tool part 12 Lower tool part 13 Lower tool part 14 Lower tool part 15 Lower tool part 16 Indication arrow 17 Precision cutting tool (active) 18 Spring pack 19 Cutting punch 20 Downholder 21 Workpiece 22 Cutting die 23 Scrap 24 Counter support 25 Hydraulic piston 26 Spring pack 27 Check valve 28 Pressure accumulator 29 Pressure plate 30 Closed state 31 Open state 32 Pressure chamber 33 Released position 34 Retaining module 35 Direction of arrow 36 Open state