Methods of material forming and/or cutting

Abstract

A method for material forming and/or cutting by means of a tool and a drive unit. The method includes moving the drive unit to provide kinetic energy to the tool, for the tool to strike a work material, so as to form and/or cut the work material when the tool is operatively disassociated from the drive unit before the tool strikes the work material.

Claims

1. A method for material forming and/or cutting, by means of a tool and a plunger, wherein the plunger is arranged to be driven by a hydraulic system comprising a first chamber for hydraulically biasing the plunger towards a work material, the method comprising: arranging the tool so as to be stationary; moving hydraulic fluid to the first chamber to accelerate the plunger; striking the stationary tool with the accelerated plunger to provide kinetic energy to the tool; decelerating the plunger before the tool strikes the work material, wherein the tool separates from the plunger, (i) by reducing the transport of hydraulic fluid towards the first chamber while avoiding cavitation of the hydraulic fluid, and/or (ii) by making a part of the plunger entering a braking chamber, thereby allowing hydraulic fluid to be trapped in the braking chamber, whereby an increased pressure in the trapped fluid decelerates the plunger; and subsequently striking the work material using the kinetic energy of the tool, whereby the work material is formed and/or cut.

2. The method according to claim 1, comprising guiding the tool towards the work material, after the tool has separated from the plunger.

3. The method according to claim 1, wherein the plunger is decelerated so that the tool does not come into contact with the plunger again, until after the tool has stricken the work material.

4. The method according to claim 1, comprising, before providing kinetic energy to the tool by the acceleration of the plunger, positioning the tool at a distance of at least 3 mm from the work material.

5. A non-transitory computer readable medium carrying a computer program for performing the steps of claim 1 when said computer program is run on a computer.

6. A control unit configured to perform the steps of the method according to claim 1.

7. A method for material forming and/or cutting, by means of a tool and a plunger, wherein the plunger is arranged to be driven by a hydraulic system comprising a first chamber for hydraulically biasing the plunger towards a work material, the method comprising: moving hydraulic fluid to the first chamber to accelerate the plunger; wherein the tool is in contact with the plunger during at least a part of the acceleration of the plunger to provide kinetic energy to the tool; decelerating the plunger before the tool strikes the work material, wherein the tool separates from the plunger, (i) by reducing the transport of hydraulic fluid towards the first chamber while avoiding cavitation of the hydraulic fluid and/or (ii) by making a part of the plunger entering a braking chamber, thereby allowing hydraulic fluid to be trapped in the braking chamber, whereby an increased pressure in the trapped fluid decelerates the plunger, and subsequently striking the work material using the kinetic energy of the tool, whereby the work material is formed and/or cut.

8. The method according to claim 7, comprising guiding the tool towards the work material, after the tool has separated from the plunger.

9. The method according to claim 7, wherein the plunger is decelerated so that the tool does not come into contact with the plunger again, until after the tool has stricken the work material.

10. The method according to claim 7, comprising, before providing kinetic energy to the tool by the acceleration of the plunger, positioning the tool at a distance of at least 3 mm from the work material.

11. A non-transitory computer-readable medium carrying a computer program for performing the steps of claim 7 when the said computer program is run on a computer.

12. A control unit configured to perform the steps of the method according to claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, embodiments of the invention will be described with reference to the drawings, in which:

(2) FIG. 1 shows an apparatus for high velocity material forming and/or cutting according to an embodiment of the invention,

(3) FIG. 2 is a flow diagram, depicting steps in a striking process of the apparatus in FIG. 1

(4) FIG. 3 shows an apparatus for high velocity material forming and/or cutting according to another embodiment of the invention, and

(5) FIG. 4 shows an apparatus for high velocity material forming and/or cutting according to yet another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) FIG. 1 shows an apparatus for high velocity material forming and/or cutting according to an embodiment of the invention. The apparatus comprises a frame 7. The frame is supported by a plurality of support devices 10. An anvil 6 is fixed to the frame. In this embodiment, the anvil 6 is fixed at the top of the frame 7.

(7) A tool, herein referred to as a fixed tool 5, is mounted to the anvil. The fixed tool 5 is mounted to a lower side of the anvil 6. A movable tool 4, described closer below, is located below the fixed tool 5. The tools 4, 5 present complementary surfaces facing each other. A workpiece W is removably mounted to the fixed tool 5. The workpiece W may be mounted to the fixed tool 5 in any suitable manner, e.g. by clamping, or with vacuum. The workpiece W could be of a variety of types, for example a piece of sheet metal. The movable tool 4 is herein also referred to as a first tool. The fixed tool 5 is herein also referred to as a second tool. It should be noted that in some embodiments, also the second tool 5 could be movable.

(8) In the embodiment shown in FIG. 1, a drive assembly comprising a cylinder housing 2 is mounted to the frame 7. Further, the drive assembly comprises a drive unit, hereinafter called plunger 1 that is arranged in the cylinder housing 2. The plunger 1 is elongated, and has, as understood from the description below, a varying width along its longitudinal axis. Preferably, any cross-section of the plunger is circular. The plunger 1 is arranged to move towards and away from the fixed tool 5, as described closer below.

(9) Before providing kinetic energy to the tool 4 by moving or accelerating the drive unit to accelerate the tool, the tool may be positioned at a distance of at least 5 mm from the work material W. Preferably the tool is at a distance of at least 8 mm from the work material W. Most preferably the tool is at a distance of at least 12 mm from the work material W.

(10) The plunger 1 is arranged to be driven by a hydraulic system. The hydraulic system comprises a first chamber 17 for biasing the plunger towards the workpiece, and a second chamber 18 for biasing the plunger away from the workpiece. The first and second chambers are formed by the cylinder housing 2 and the plunger 1. In this example, the workpiece is above the plunger. Thus, in this example, the first chamber 17 is located below the second chamber 18.

(11) The hydraulic system comprises a hydraulic pump 16, for increasing the pressure of a hydraulic fluid in the system, to what is herein referred to as a system pressure pS. The hydraulic system further comprises a non-return valve 161 downstream of the hydraulic pump 16. The second chamber 18 is permanently connected to the system pressure pS. A hydraulic accumulator 13 is arranged to store hydraulic fluid at the system pressure. As understood from the description below, the accumulator 13 is provided to achieve a rapid pressure increase in the first chamber at a plunger acceleration.

(12) The hydraulic system further comprises a valve arrangement. The valve arrangement comprises a first valve 11, and a second valve 12. The first valve 11 is connected to the first chamber 17 as well as to the second chamber 18. Also, the second valve 12 is connected to the first chamber 17 as well as to the second chamber 18. The valve arrangement is controllable by an electronic control unit CU. The valves 11, 12 are arranged to assume positions, so as to provide the steps described below. It is noted here that the valve arrangement 11, 12 can assume a position in which there is no communication between the first and second chambers 17, 18. The valves may be provided with draining devices for end bushing leaks.

(13) At opposite ends, the cylinder housing and the plunger form axial slide bearings 21, 22. Thereby one of said bearings 21 delimits the first chamber 17, and is herein referred to as a first chamber bearing 21. The other of said bearings 22 delimits the second chamber 18, and is herein referred to as a second chamber bearing 22. At each of the first and second bearings 21, 22, draining conduits 9 are provided. An intermediate axial slide bearing 23 is formed, by the cylinder housing and the plunger, between the first and second chambers 17, 18. The bearings 21, 22, 23 allow an axial movement of the plunger 1 in relation to the cylinder housing 2.

(14) The three bearings 21, 22, 23 are circular, as seen in a direction which is parallel to the movement direction of the plunger. Also, the bearings have mutually different diameters. More generally, the bearings have mutually different areas. In other words, circles formed by the circular shape of the bearings have mutually different areas. As a result, the effective areas of the plunger 1 in the first and second chambers differ. In this example, the area A23 of the intermediate bearing 23 is larger than the area A22 of the second bearing 22. In turn, the area A22 of the second bearing 22 is larger than the area A21 of the first bearing 21. Thereby, for balancing the plunger 1 in a static position, with the system pressure pS in the second chamber and an adjusted pressure pA in the first chamber, the adjusted pressure pA has to be such that

(15) $p{A}^{}\left(A23-A21\right)=p{S}^{}\left(A23-A22\right)+{\mathrm{mp}}^{}g$ where mp is the mass of the plunger and g is the acceleration of gravity.

(16) Reference is made also to FIG. 2, depicting steps in a striking process of the apparatus in FIG. 1, involving a strike by the movable tool 4 against the workpiece W and the fixed tool 5.

(17) Before the strike, the movable tool 4 rests S1 on top of the plunger 1. In addition, before the strike, the movable tool 4 is at a distance from the fixed tool 5. Thereby, the plunger 1 and the movable tool 4 are S1 in, what is herein referred to as, respective starting positions.

(18) The first valve 11 is in this example, a 4 way, 3 position valve. Before the strike, the first valve 11 is closed. Also, before the strike, the second chamber 18 is subjected to the system pressure pS. Simultaneously, the second valve 12 is used to control the adjusted pressure pA in the first chamber 17, so as to keep the plunger 1 is a fixed position, as detailed above. The second valve 12 is preferably a proportional valve. It is understood that, to keep the plunger 1 stationary, the adjusted pressure pA of the first chamber 17 may be lower than the system pressure pS. Thereby, the plunger may be kept in its starting position.

(19) The acceleration of the plunger 1 is affected by adjusting the starting position of the plunger 1 and the system pressure pS.

(20) Before the strike by the movable tool 4 is effected, the workpiece W is fixed S2 at the fixed tool 5. It is understood that in the starting position, the movable tool 4 is at a distance from the workpiece W.

(21) When the strike is to commence, the first valve 11 and the second valve 12 are moved to a respective position, in which the respective ports P, with the system pressure pS, is connected with respective ports A, connected to the first chamber 17. Also, in the first valve 11, in said position, port B, with the system pressure pS, is connected to port T, connected to the first chamber 17. As a result, the plunger 1 will accelerate S3, with the movable tool 4, towards the workpiece W. Thereby, hydraulic fluid will flow to the first chamber 17, from the second chamber 18, and from the accumulator 13. Meanwhile, the second chamber 18 is provided with the system pressure pS. A force F moving the plunger can be expressed as

(22) $F=p{S}^{}\left(A22-A21\right)-{\mathrm{mp}}^{}g$ where A21 and A22 are the areas of the first and second bearings 21, 22, respectively, as explained above.

(23) During the acceleration, the movable tool 4 remains resting on the plunger 1. Thereby, the plunger and the movable tool are accelerated with the same, simultaneous acceleration.

(24) Subsequently, the plunger 1 is decelerated S4, or braked. The plunger deceleration is commenced before the movable tool 4 has reached the workpiece W. For the plunger deceleration the first valve 11 is moved to a closed position. Further, for the plunger deceleration, the second valve 12 is controlled so that the transport of hydraulic fluid towards the first chamber 17 is reduced. Thereby, the second valve 12 is controlled so that the transport of hydraulic fluid towards the first chamber 17 is relatively low. However, said control of the second valve 12 is such that transport of hydraulic fluid towards the first chamber 17 is high enough to avoid cavitation of the hydraulic fluid.

(25) During the deceleration, the second chamber 18 remains connected to the system pressure pS. The plunger 1 is provided with a waist 14, which is arranged to enter a braking chamber 15 at an end of the second chamber 18. In this example, the braking chamber 15 is formed at the upper end of the second chamber 18. Thereby, for the plunger deceleration, the waist 14 enters to braking chamber 15. This will trap hydraulic fluid in the braking chamber, and the increased pressure in the trapped fluid will serve to brake the plunger 1. Thereby, the plunger velocity may be reduced to zero.

(26) When the plunger deceleration commences, the movable tool 4 is separated S5 from the plunger 1. The movable tool continues S5, by its inertia, towards the workpiece W. In embodiments of the invention, the velocity of the movable tool 4 at this stage may be for example between 1-20 m/s. The velocity of the movable tool 4 at this stage may for example be above 10 m/s, or even above 12 m/s. The velocity of the movable tool 4 may be selected. The velocity of the movable tool 4 may be selected to optimize the striking process.

(27) The path of the movable tool 4 is controlled S5 by a guiding arrangement 3. In this example, the guiding arrangement comprises a plurality of pins, which are fixed to the movable tool 4. The pins extend from the movable tool and through respective opening in the frame 7.

(28) Subsequently, the movable tool hits S6 the workpiece, and the kinetic energy of the movable tool 4 shapes the workpiece W between the movable tool 4 and the fixed tool 5.

(29) When the shaping of the workpiece is finished, the movable tool 4 will bounce back. It is understood that when the shaping of the workpiece is finished, the movable tool 4 will fall S7 towards the plunger 1. Thereby, the movable tool will be guided by the guiding arrangement 3.

(30) To brake the return movement of the movable tool 4, as it approaches the plunger 1, a damping arrangement 8 is provided. In this example, the damping arrangement comprises a damper mounted to the plunger 1. The damper is mounted at the top end of the plunger. The damper may be of any suitable kind, e.g. hydraulic or pneumatic. Alternatively, or in addition, the damper may comprise an elastic element, such as a plate spring. In some embodiments, the damping arrangement may comprise a damper mounted to the movable tool. In further embodiments, the damping arrangement may comprise a damper mounted to the frame 7. The damping arrangement will effectively brake S8 the return movement of the movable tool. The damping arrangement may also prevent bouncing of the movable tool at the end of its return movement. Thereby, the movable tool 4 may be brought back to rest on the plunger in a controlled manner.

(31) When the plunger 1 has been stopped, the first valve 11 is closed. Thereby, the second chamber is still subjected to the system pressure pS. Simultaneously, the second valve 12 is used to control the adjusted pressure pA in the first chamber 17, so as to move S9 the plunger 1 back to its starting position, from which a subsequent plunger acceleration can be initiated.

(32) In some embodiments, the tool contacts the plunger, after the shaping of the workpiece, and before the plunger is moved S9 back towards its starting position. However, in other embodiments, the plunger 1 may be moved S9 back to its starting position, before the tool contacts the plunger after the shaping of the workpiece. In further embodiments, the plunger 1 may be moved a part of the way towards its starting position, before the tool contacts the plunger after the shaping of the workpiece.

(33) The control unit CU is arranged to receive signals from one or more sensors (not shown). Thereby, the signals received by the control unit CU may be indicative of one or more of the plunger position, the plunger velocity, the plunger acceleration, the movable tool position, the movable tool velocity, the movable tool acceleration, the adjusted pressure pA, the response time(s) of the valve arrangement 11, 12, and the ambient temperature.

(34) The control unit CU is arranged to register and/or process the signals received during at least one striking process, preferably the signals received during a plurality of striking processes, more preferably the signals received during every striking process. The processed, or un-processed signals are stored to form historic striking process data.

(35) The control unit CU is also arranged to adjust for, or during, a striking process, the control of the valve arrangement 11, 12, based on the historic data, and current sensor signals. Thereby the timing of valve actuations during the striking process may be accurate, in view of circumstances such as the temperature and the aging of the apparatus.

(36) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

(37) FIG. 3 shows an apparatus for high velocity material forming and/or cutting according to another embodiment of the invention. The same reference numerals are used for the corresponding features as shown and described with reference to FIG. 1.

(38) A tool, herein referred to as a fixed tool (not shown), can be mounted to the anvil 6. The fixed tool can be mounted to a lower side of the anvil 6. A movable tool 4, described closer below, is located below the fixed tool. The tools present complementary surfaces facing each other. A workpiece W is removably mounted to the fixed tool. The workpiece W may be mounted to the fixed tool in any suitable manner, e.g. by clamping, or with vacuum. The workpiece W could be of a variety of types, for example a piece of sheet metal. The movable tool 4 is herein also referred to as a first tool. The fixed tool is herein also referred to as a second tool. It should be noted that in some embodiments, also the second tool could be movable.

(39) A drive assembly comprising a cylinder housing 2 is mounted to a frame (not shown). Further, the drive assembly comprises a drive unit, hereinafter called plunger 1, that is arranged in the cylinder housing 2. The plunger 1 is elongated, and has, as understood from the description below, a varying width along its longitudinal axis. Preferably, any cross-section of the plunger is circular. The plunger 1 is arranged to move towards and away from the fixed tool, as described closer below.

(40) Before providing kinetic energy to the tool 4 by moving or accelerating the drive unit to strike the tool, the tool may be positioned at a distance of at least 3 mm from the work material W. Preferably the tool is at a distance of at least 5 mm from the work material W. Most preferably the tool is at a distance of at least 8 mm from the work material W.

(41) The plunger 1 is arranged to be driven by a hydraulic system. Similarly to the embodiment described with reference to FIG. 1, the hydraulic system comprises a first chamber for biasing the plunger towards the workpiece, and a second chamber for biasing the plunger away from the workpiece. The first and second chambers are formed by the cylinder housing 2 and the plunger 1.

(42) The hydraulic system as described above with reference to the embodiment shown in FIG. 1 may be applied for the drive unit shown in FIG. 3.

(43) As the movable plunger is driven towards the workpiece W, the plunger strikes the tool 4.

(44) Similarly to the embodiment in FIG. 1, during the deceleration, the second chamber remains connected to the system pressure. The plunger 1 is provided with a waist 14, which is arranged to enter a braking chamber 15 at an end of the second chamber. Thereby, for the plunger deceleration, the waist 14 enters to braking chamber 15. This will trap hydraulic fluid in the braking chamber, and the increased pressure in the trapped fluid will serve to brake the plunger 1. Thereby, the plunger velocity may be reduced to zero.

(45) The tool 4 may be separated from the plunger 1, when the latter strikes the former. The strike may serve to decelerate the plunger 1. When the plunger deceleration commences, the movable tool 4 is separated from the plunger 1. The movable tool continues, by its inertia, towards the workpiece W.

(46) Similarly to the embodiment in FIG. 1, the path of the movable tool 4 is controlled by a guiding arrangement. The guiding arrangement may comprise a plurality of pins, which are fixed to the movable tool 4. The pins extend from the movable tool and through respective opening in the frame.

(47) The guiding arrangement for controlling the path of the movable tool 4 is not shown in the embodiment shown in FIG. 3. In the embodiment shown in FIG. 3, the tool 4 is arranged stationary, preferably controlled by the mentioned guiding arrangement, before providing kinetic energy to the tool 4 by the movement of the drive unit 1. The apparatus is arranged to move the drive unit 1 to provide kinetic energy to the tool 4 by striking the stationary tool 4 with the drive unit 1.

(48) FIG. 4 shows an apparatus for high velocity material forming and/or cutting according to yet another embodiment of the invention. The same reference numerals are used for the corresponding features as shown and described with reference to FIGS. 1 and 3.

(49) A tool, herein referred to as a fixed tool (not shown), can be mounted to the anvil 6. The fixed tool can be mounted to a lower side of the anvil 6. A movable tool 4, described closer below, is located below the fixed tool. The tools present complementary surfaces facing each other. A workpiece W is removably mounted to the fixed tool. The workpiece W may be mounted to the fixed tool in any suitable manner, e.g. by clamping, or with vacuum. The workpiece W could be of a variety of types, for example a piece of sheet metal. The movable tool 4 is herein also referred to as a first tool. The fixed tool is herein also referred to as a second tool. It should be noted that in some embodiments, also the second tool could be movable.

(50) In the embodiment in FIG. 4, the drive unit is a rotating unit 1 comprising a protrusion 101 fixed to a rotor 102. The protrusion 101 is rotated by rotation of the rotor to provide kinetic energy to the tool 4. In this way the protrusion will strike the tool 4 repeatedly, for each revolution.

(51) A guiding arrangement for controlling the path of the movable tool 4 is not shown in the embodiment shown in FIG. 4, but a similar guiding arrangement as in FIG. 1 can be used. In the embodiment shown in FIG. 4, the tool 4 is arranged stationary, preferably controlled by the mentioned guiding arrangement, before providing kinetic energy to the tool 4 by the movement of the rotating unit 1. The apparatus is arranged to move the rotating unit 1 to provide kinetic energy to the tool 4 by striking the tool 4 with the protrusion projecting from the periphery of the rotating unit 1. When the rotating unit, comprising the protrusion fixed to the rotor, continues its rotation, the movable tool 4 is separated from the protrusion of the rotor. The movable tool 4 continues, by its inertia, towards the workpiece W. Hence, the tool 4 will be operatively disassociated from the rotating unit 1 before the tool 4 strikes the work material W. The tool 4 is brought back to the fixed position, preferably controlled by the mentioned guiding arrangement, when the protrusion is in the position ready to strike the tool again for the next revolution of the rotor. The protrusion will strike the tool 4 repeatedly, for each revolution, until the rotating unit is stopped in a controlled manner.