Device for stabilizing a workpiece in a machine tool

Abstract

The invention relates to a device for stabilizing a workpiece in a machine tool. The invention relates to a device for stabilizing a workpiece, in particular a thin-walled workpiece mounted in a machine tool, comprising at least one base; and a plurality of stabilizing elements. The stabilizing elements project away from one surface of the base, wherein the stabilizing elements comprise a cylinder and a rod arranged therein, and the rod can be driven hydraulically to move in the axial direction of the stabilizing element, so that the rods of at least two of the stabilizing elements can be brought into contact with one surface of the workpiece.

Description

TECHNICAL FIELD

[0001] The present invention relates to an apparatus for stabilizing a workpiece mounted in a machine tool. Further, the present invention relates to a machine tool comprising an apparatus for stabilizing a workpiece to be machined by the machine tool. BACKGROUND

[0002] Machine tools are of importance for reliable and precise cutting, in particular when cutting high-performance alloys for aerospace components. However, machining thin-walled components for aerospace applications can be challenging, as during machining, the milling cutting forces can cause deflection of the workpiece. Another problem is vibrations in the machining. If the component, such as a turbine blade, is thin and has an elongated shape, the deflection and vibrations can significantly reduce the quality of the machined component. Deflection can lead to dimensional surface errors, and vibrations can even cause damage to the machined part.

[0003] In some applications, the workpiece has a hollow or at least partially hollow body. Thus, the risk of damaging the workpiece due to deflection and vibrations during machining is even higher. If the workpiece to be machined is not optimally supported, the surface quality of such a blade deteriorates dramatically.

[0004] EP 2618961 discloses an apparatus for machining an elongated workpiece. The apparatus comprises a first clamping point for clamping a first end of the workpiece and a second clamping point for clamping a second end of the workpiece. In addition, a stationary center rest is provided to support the workpiece, and the stationary center rest is movable along a longitudinal axis of the workpiece.

[0005] However, the workpiece is not supported over the entire area, and it can not be possible to suppress the deflection occurring on the workpiece due to the cutting forces. SUMMARY

[0006] It is an object of the present invention to provide an apparatus for stabilizing a workpiece mounted in a machine tool and to be machined thereby. It is a further object of the present invention to provide an apparatus for supporting a thin-walled workpiece machined by a machine tool having a damping function.

[0007] According to the invention, these objects are achieved by the features of the independent claims. Further advantageous embodiments result from the dependent claims and the description.

[0008] According to the invention, an apparatus for stabilizing a workpiece, in particular a thin-walled workpiece mounted in a machine tool, comprises a base and a plurality of stabilizing elements projecting away from a surface of the base. In a variant, at least ten stabilizing elements, preferably at least 20 stabilizing elements, are provided distributed in at least two rows. The stabilizing elements comprise a cylinder and a rod arranged therein, and the rod can be hydraulically driven to move in the axial direction of the stabilizing element, so that the rods of at least two stabilizing elements can be brought into contact with a surface of the workpiece. The base is made of a material providing high mechanical stability, for example AIMgSi1MN. The base has an elongated body. The length of the body is preferably greater than the height of the body.

[0009] Obtaining, for example, a turbine blade by machining a thin-walled part requires roughing and finishing. To mill the workpiece, it is clamped in a machine tool in the horizontal direction at each end, while a milling cutter is mounted in the spindle of the machine tool to remove material. After roughing, most of the material has been removed, and the workpiece usually has an elongated body with very thin walls. During finishing, the desired profile surface can be obtained. In this phase, the workpiece must be clamped stably in the machine tool. However, the workpiece is usually clamped in the machine tool only at the two ends. If the workpiece is very thin, high cutting forces acting on the workpiece can cause the workpiece to deflect locally. To avoid possible deflection, ideally, the entire surface of the workpiece should be supported.

[0010] Therefore, the apparatus for stabilizing a workpiece can be placed, for example, under the workpiece and close to one surface of the workpiece to avoid large distances between the workpiece and the apparatus. The apparatus is also clamped at both ends by clamping means for clamping the workpiece or by different clamping means. The stabilizing elements are arranged substantially vertically on the surface of the base so as to be movable in the axial direction of the stabilizing elements to reach the surface of the workpiece. The stabilizing elements are not locked in one position during machining. The movement of the stabilizing elements in the axial direction can dampen local vibrations by the friction of the flow of oil.

[0011] In one embodiment, when the workpiece and the apparatus are mounted in a machine tool, the stabilizing elements are hydraulically driven and controlled so that all the stabilizing elements are in contact with the surface of the workpiece. When a fluid, for example oil, is supplied to each stabilizing element, the rod is pushed by the fluid to extend out of the cylinder.

[0012] In a preferred embodiment, the stabilizing elements can be pneumatically driven to move in the axial direction of the stabilizing elements. This function enables the rod to be pushed back to an initial position located at the bottom of the cylinder. For example, to mount and / or dismount the apparatus and the workpiece to / from a machine tool, it is more convenient to handle the rod at this initial position.

[0013] If the workpiece is supported from both sides, the best stability can be achieved, since a suction force acting on the workpiece can occur during the milling process. In order to benefit from this advantage, in this preferred embodiment the apparatus comprises two bases, namely a first base and a second base. A first set of the plurality of stabilizing elements is arranged on the first base and a second set of the plurality of stabilizing elements is arranged on the second base.

[0014] When the apparatus is clamped in a machine tool, the workpiece is positioned between the two bases and the two sets of stabilizing elements. The stabilizing elements are hydraulically driven and controlled such that the first set of stabilizing elements can be in contact with a first surface of the workpiece and the second set of stabilizing elements can be in contact with a second surface of the workpiece. In particular, the second surface of the workpiece is on the opposite side of the first surface of the workpiece. Furthermore, the first set of stabilizing elements and the second set of stabilizing elements are hydraulically connected together. Thus, hydraulic fluid supplied into the first set of stabilizing elements can flow into the second set of stabilizing elements and vice versa to stabilize the workpiece from both sides.

[0015] If the stabilizing elements are symmetrically distributed over the surface of the base. The workpiece can be supported evenly over the entire surface. However, the stabilizing elements can also be arranged in an irregular manner to provide optimal support. For example, depending on the shape and weight variations at different locations, certain areas of the workpiece require stronger support than other areas of the workpiece.

[0016] The stabilizing elements comprise a cylinder and a piston arranged therein, which is hydraulically driven to reciprocate in the cylinder.

[0017] Further, a rod is mounted in the piston and the rod can be moved into a position in which its one end protrudes out of the cylinder. Preferably, the rod and the piston are formed in one piece.

[0018] In order to ensure damping and to avoid high pressure at one point of the workpiece, a rod head is mounted on the top of the rod and the rod head is made of an elastic material, in particular the cap has a spherical shape.

[0019] The interior of the cylinder is divided into an upper chamber and a lower chamber by the piston. For hydraulic driving, fluid is supplied to each stabilizing element, in particular from the bottom of the cylinder, through an inlet provided on the cylinder, which is connected to the lower chamber. This arrangement has the advantage of a simple construction. However, fluid can also be supplied into the cylinder through an inlet on the side surface of the cylinder, but below the piston. When said fluid is supplied into the lower chamber of the cylinder, the piston and the rod connected thereto are pushed upwards by said liquid to move in the axial direction. Said inlet is designed to throttle the hydraulic fluid flowing out of the cylinder when the stabilizing elements are brought into contact with the surface of the workpiece, in particular, said inlet has a funnel shape. The side of said inlet in the lower chamber of the cylinder has a smaller diameter than the side of said inlet supplying said fluid. However, said fluid can flow between the stabilizing elements to adjust the position of the rods of the stabilizing elements to compensate for the deflection of the workpiece.

[0020] A ventilation device is operatively connected to the upper chamber of the cylinder to force the piston to move to the initial position. When said ventilation device is activated, air can be supplied from said ventilation device to said upper chamber to force the piston to move to the bottom of the cylinder.

[0021] For certain applications, in particular machining thin-walled workpieces, it is advantageous to design the base with a curved shape, in particular with a top surface having a similar shape as the surface of the workpiece. In a preferred variant, said base has an elongated body.

[0022] To reduce the overall weight of the device without compromising the mechanical stability of the device, a recess is formed in the interior of the base. In addition, said recess provides space for accommodating all fluid and air supply circuits to obtain a compact design.

[0023] In one variant, all stabilizing elements have the same dimensions, such as the length of the rods, the diameter of the cylinder. In another variant, stabilizing elements with different dimensions are installed to adapt to the shape of the workpiece and the forces acting on the workpiece at different locations.

[0024] Automatic clamping elements are attached on the surface of the base opposite to the surface on which the stabilizing elements are provided, for example to automatically install and / or remove the device into / from the machine tool by a robot.

[0025] The device further comprises two slave clamping devices attached to the two distal ends of the base for installing the device into the machine tool. Said slave clamping devices are pneumatic clamping systems, preferably zero-point clamping systems.

[0026] The present invention relates to a machine tool comprising a master clamping device to clamp the device in the machine tool. A first fluid channel for supplying hydraulic fluid and a second fluid channel for supplying air are embedded in said master clamping device and said master clamping device can be coupled to slave clamping devices of said device.

[0027] On each base, two slave clamping devices are provided on both ends of the base for clamping the device into a machine tool. Main inlets for supplying hydraulic and pneumatic fluids are embedded in the slave clamping devices.

[0028] In a variant, the slave clamping devices and the base are formed in one piece.

[0029] Fluid channels for supplying hydraulic and pneumatic fluids are embedded in the main clamping device. The device is clamped to the main clamping device by means of a 0-point clamping connector. By mounting the device into a machine tool, the fluid channels in the main clamping device are directly coupled to the main inlets embedded in the slave clamping devices by means of the slave clamping devices and the main clamping device.

[0030] Further, the hydraulic fluid supplied into the first set of stabilizing elements can flow into the second set of stabilizing elements or vice versa, as the main inlets for the first and second base can be connected by means of the fluid channels in the main clamping device. BRIEF DESCRIPTION OF DRAWINGS

[0031] In the following a more particular description of the principles briefly described above will be provided by reference to specific embodiments thereof illustrated in the drawings. These drawings illustrate exemplary embodiments of the present disclosure and, therefore, are not to be considered limiting in their scope. The principles of the present disclosure are described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0032] Figure 1 illustrating a device for supporting a workpiece;

[0033] Figure 2 illustrating a front view of a stabilizing element;

[0034] Figure 3 illustrating a cross-sectional view of a stabilizing element;

[0035] Figure 4 illustrating one embodiment of a device; and

[0036] Figure 5 illustrating a device mounted in a machine tool. DETAILED DESCRIPTION

[0037] Figure 1An apparatus 1 for stabilizing a workpiece, which is in particular a thin-walled workpiece mounted in a machine tool, is illustrated. For machining the thin-walled workpiece, it has to be clamped stably in the machine tool. The apparatus comprises a base 10 and a plurality of stabilizing elements 10 fixedly mounted on the top surface of the base. In this embodiment, the base has an elongated body and a curved top surface to shape it to the workpiece. In this way, a support force perpendicular to the surface of the workpiece can be exerted by the stabilizing elements. On the top surface of the base, a plurality of holes 4 are provided, and each hole receives one stabilizing element. To accommodate the components for supplying hydraulic and pneumatic fluid into the stabilizing elements, the base is designed to be at least partially hollow.

[0038] In this embodiment, the stabilizing elements are provided in three rows. On each row, more than four stabilizing elements are provided in order to be able to stabilize a workpiece having a relatively large surface. Figure 1 An example is shown in which all stabilizing elements have the same size.

[0039] In Figure 2 and Figure 3 the structure of the stabilizing elements is shown in detail. Figure 3 is a cross-sectional view along the line A-A. Each stabilizing element comprises a cylinder 11 and a piston 12. The cylinder has a tubular shape and two parts formed in one piece. The lower part is a cylinder base 11a for stably mounting the cylinder on the base of the apparatus by means of a fixing device. The upper part 11b is a cylinder body to accommodate the piston therein and to stand upright on the base 30. The piston 12 and the rod 13, which are formed in one integrated piece, are arranged in the hollow space inside the cylinder body so as to be able to move in the axial direction of the cylinder. The piston and the rod are formed in one single piece but have different diameters. The diameter of the piston is designed to correspond to the inner diameter of the cylinder. A piston guide ring 17 and a piston sealing device 16 are provided on the piston. The piston guide ring serves to avoid mechanical contact between the piston and the inner surface of the cylinder and to reduce lateral forces. On the upper part inside the cylinder, a cylinder cover 20 is fixedly mounted on the inner surface of the cylinder to form a closed inner space in the cylinder. The rod protrudes from a through hole in the middle of the cylinder cover. A rod guide ring 22 and a rod sealing device 21 are arranged in a recess formed on the inner surface of the cylinder cover. A rod head 14 having a spherical shape is mounted on the top of the rod so as to be in direct contact with the workpiece being machined. The rod head can be made of a resilient material. An inlet opening 15 is provided on the cylinder base for supplying hydraulic fluid into the interior of the cylinder to enable the piston to reciprocate in the axial direction of the cylinder. The interior of the cylinder is divided by the piston into a lower chamber 25 and an upper chamber 24. The rod is arranged in the upper chamber. The hydraulic fluid is received in the lower chamber and pushes the piston to move in the direction of the workpiece.

[0040] Before machining, a ventilation device (e.g., a nozzle) is activated to force the piston to its initial position, meaning the piston moves to the bottom of the lower chamber on one side of the cylinder base under air pressure. The ventilation device includes an air chamber 28 communicatively connected to the upper chamber 24 of the cylinder and separated from both the lower and upper chambers by a separating device 26 (e.g., a wall). The air chamber is closed by a sealing device. The device is mounted in a machine tool by holding the pistons of all stabilizing elements in their initial positions. After mounting the device in the machine tool and placing a workpiece above it, the ventilation device is deactivated, and the lower chambers of all cylinders are supplied with hydraulic fluid to push the pistons in the direction of the workpiece. The pistons are pushed axially by the hydraulic fluid to bring the rod head into contact with the surface of the workpiece. When at least a portion of the rod head contacts the workpiece, the valve supplying the fluid is closed. During machining, at least a portion of the piston may be movable to accommodate changes in the workpiece's shape due to forces generated thereon by the machining tool. After machining, the pistons are forced back to their initial positions by activating the ventilation device to remove the device from the machine tool.

[0041] Figure 4 An embodiment is illustrated where the workpiece is stabilized from both sides, namely from the top and bottom sides of the workpiece. The device has a first base 30a and a second base 30b. Automatic clamping elements 5 are provided on the bottom of the bases, i.e., on the opposite sides where the stabilizing elements are arranged. The automatic clamping elements are used for loading the device by a robot. In this configuration, the first set of stabilizing elements 10a is driven downwards to stabilize the workpiece from the top, while the second set of stabilizing elements 10b is driven upwards to stabilize the workpiece from the bottom. On each base, two secondary clamping devices 31a, 32a, 31b, and 32b are provided at the ends of the base for clamping the device into a machine tool. Main inlets for supplying hydraulic and pneumatic fluids are embedded in the secondary clamping devices.

[0042] Figure 5 This shows the state in which the equipment is clamped in the main clamping devices 50 and 51 of the machine tool. Fluid channels for supplying hydraulic and pneumatic fluids are embedded in the main clamping devices, but... Figure 5 The device is not visible in the machine tool. It is clamped to the main clamping device via a zero-point clamping connector. By installing the device into the machine tool, the fluid passage in the main clamping device is directly connected to the main inlet embedded in the slave clamping device via the slave clamping device and the main clamping device.

[0043] Furthermore, the hydraulic fluid supplied to the first set of stabilizing elements can flow into the second set of stabilizing elements, or vice versa, because the main inlets for the first and second bases can be connected through the fluid channels in the main clamping device.

[0044] In this embodiment, the hydraulic fluid is supplied to the fluid passage in the main clamping device and then distributed to the first set of stabilizing elements through a first main inlet in the first slave device, and to the second set of stabilizing elements through a second main inlet in the second slave device. If, during machining, the force exerted by the workpiece on one or more of the stabilizing elements in the first set increases, the hydraulic fluid flows out from the lower chamber of the cylinder of these stabilizing elements in the first set and further flows into the second set of stabilizing elements to adjust the position of the pistons in the second set of stabilizing elements.

[0045] List of reference numerals in the attached diagram:

[0046] 1 Equipment

[0047] 3. Workpiece

[0048] 4 holes

[0049] 5 Automatic clamping elements

[0050] 10 Stabilizing Components

[0051] 10a First group of stabilizing elements

[0052] 10b Second group of stabilizing elements

[0053] 11 cylinders

[0054] 11a Cylinder base

[0055] 11b cylinder body

[0056] 12 Pistons

[0057] 13 strokes

[0058] 14 clubheads

[0059] 15. Inlet for fluid

[0060] 16 Piston Seals

[0061] 17 Guide ring for piston

[0062] 20 Cylinder Head

[0063] 21 rod seals

[0064] 22 Guide ring for rod

[0065] 24 Upper Room

[0066] 25 lower room

[0067] 26 Separation device

[0068] 28 Air Chamber

[0069] 30 base

[0070] 30a First base

[0071] 30b Second base

[0072] 31a, 32a First clamping device

[0073] 31b, 32b Second clamping device

[0074] 50, 51 Main clamping device.

Claims

1. An apparatus (1) for stabilizing a workpiece mounted in a machine tool, comprising: a. at least one base (30); and b. a plurality of stabilizing elements (10) projecting from a surface of said base, wherein said stabilizing elements comprise a cylinder and a rod arranged therein, and said rod is hydraulically drivable to move in an axial direction of said stabilizing element, such that the rods of at least two of said stabilizing elements can be brought into contact with a surface of said workpiece, wherein said stabilizing elements are configured to be movable while maintaining contact with said workpiece during machining of said workpiece, so as to adapt said stabilizing elements to shape changes of said workpiece due to forces generated on said workpiece by a machining tool.

2. The apparatus according to claim 1, wherein said stabilizing elements are pneumatically drivable to move in said axial direction of said stabilizing element.

3. The apparatus according to claim 1 or 2, wherein said apparatus comprises a first base (30a) and a second base (30b) and a first set of said plurality of stabilizing elements (10a) arranged on said first base (30a) and a second set of said plurality of stabilizing elements (10b) arranged on said second base (30b).

4. The apparatus according to claim 3, wherein when said apparatus is mounted in said machine tool, said stabilizing elements are hydraulically driven and controlled such that said first set of stabilizing elements can be brought into contact with a first surface of said workpiece and said second set of stabilizing elements can be brought into contact with a second surface of said workpiece, said second surface of said workpiece being an opposite surface of said first surface of said workpiece.

5. The apparatus according to claim 1 or 2, wherein on each base, said stabilizing elements are distributed on said surface of said base at equal distances from each other.

6. The apparatus according to claim 1 or 2, wherein said stabilizing elements comprise a piston (12) arranged inside said cylinder, and said rod is mounted on said piston to follow movements of said piston.

7. The apparatus according to claim 6, wherein said piston is hydraulically pushable to a position in which one end of said rod protrudes from said cylinder.

8. The apparatus according to claim 6, wherein an opening (15) is formed on a wall of said cylinder for supplying hydraulic fluid into said cylinder to exert an axial force on said piston.

9. The apparatus according to claim 8, wherein said opening is configured to throttle said hydraulic fluid out of said cylinder when said stabilizing elements are brought into contact with said surface of said workpiece.

10. The apparatus according to claim 6, wherein an interior of said cylinder is divided by said piston into an upper chamber and a lower chamber, and a venting device is operatively connected to said upper chamber, and when said venting device is activated, air can be supplied from said venting device to said upper chamber to force said piston to move to a bottom of said cylinder.

11. The apparatus according to claim 1 or 2, wherein a top surface of said base is configured to have a similar shape as a surface of said workpiece. ​ 12. The device according to claim 1 or 2, wherein a clamping device is provided on at least one end of the base for clamping the device into the machine tool.

13. The device according to claim 1 or 2, wherein an automatic clamping element is arranged on the surface of the base opposite to the surface on which the stabilizing elements are provided.

14. The device according to claim 1, wherein the workpiece is a thin-walled workpiece (4).

15. The apparatus of claim 7, wherein, A head (14) is provided on the top of the stem and can be in direct contact with one surface of the workpiece.

16. The device according to claim 8, wherein the opening (15) is formed on the bottom of the cylinder.

17. The apparatus of claim 8, wherein, The hydraulic fluid is oil.

18. The apparatus of claim 9, wherein, The opening has a funnel shape.

19. The apparatus of claim 11, wherein, The top surface of the base has a curved shape.

20. A machine tool comprising a main clamping device (50) for clamping the device according to any one of claims 1 to 19 into the machine tool, wherein a first fluid channel for supplying hydraulic fluid and a second fluid channel for supplying air are embedded in the main clamping device.

21. The machine tool according to claim 20, wherein a main inlet for supplying the hydraulic fluid into the stabilizing elements is integrated in each slave clamping device, and the first fluid channel in the main clamping device is directly coupled to the main inlet in the slave clamping devices by mounting the device into the machine tool.

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