Separating device and method for detaching workpiece parts from an in particular flat workpiece

Abstract

The invention relates to a separating device (10) for detaching workpiece parts (24) from an in particular flat workpiece (16), comprising an in particular flat workpiece holder (12) and fastening means (18) for fastening the workpiece (16) to the workpiece holder (12), and a vibration generator (14) for causing the workpiece holder (12) to vibrate, and a support (22), in particular a device frame, on which the workpiece holder (12) is mounted via at least one spring element (20), wherein the spring element (20) has a progressive spring characteristic curve.

Description

[0001] Separating device and method for removing workpiece parts from a workpiece, in particular a plate-shaped workpiece

[0002] The invention relates to a separating device and a method for removing workpiece parts from a workpiece, in particular a plate-shaped workpiece.

[0003] When laser cutting sheet-shaped workpieces, it is crucial that the slag produced during cutting can escape freely downwards from the kerf. To ensure this, the workpiece support in laser cutting machines for sheet-shaped workpieces typically consists of several support strips inserted into a frame. These support strips have a serrated shape, resulting in only point contact with the workpiece. Depending on the size and position of a workpiece section on the support strips, the cutting gas pressure during the cutting process can cause the workpiece section to tilt. This can cause the workpiece section to wedge itself between the support strips and tilt, potentially leading to a collision between the laser processing head or the cutting gas nozzle and the workpiece section. Furthermore, the random positioning of the workpiece sections makes automated removal difficult or even impossible.Smaller workpiece parts can fall into the gaps between the support strips if they are in an unfavorable position, and thus onto the slag conveyor belt located under the workpiece support or into slag collection containers.

[0004] To solve this problem, it is known to fix the workpiece parts within the remaining workpiece using material bridges, so-called microjoints or nanojoints, i.e., connecting bridges remaining in the cutting gap between the workpiece part and the surrounding remaining workpiece, thus preventing tilting. However, this requires subsequently cutting through the material bridges and removing the workpiece parts from the (remaining) workpiece.

[0005] The object of the present invention is to provide a device with which workpiece parts connected by a material web can be reliably removed from a remaining workpiece.

[0006] This problem is solved according to the invention by a separating device for removing workpiece parts from a workpiece, in particular a plate-shaped workpiece, with a workpiece holder, in particular a plate-shaped workpiece holder and fastening means for fastening the workpiece to the workpiece holder, and a vibration generator to set the workpiece holder into vibration, as well as a support, in particular a device frame, on which the workpiece holder is mounted via at least one spring element, wherein the spring element has a progressive spring characteristic.

[0007] In particular, flat workpieces can have a thickness of approximately 1 to 30 mm. The workpieces can also have different dimensions. This results in the entire system of the separating device, including the workpiece, exhibiting different natural frequencies, since the natural frequency depends on the mass of the workpiece and the stiffness (spring stiffness) as well as the mounting / suspension of the excitation modules. Therefore, there is a risk that the vibration generator will excite the workpiece holder and the workpiece itself at a frequency that corresponds to the natural frequency of the separating device, i.e., the entire system comprising the workpiece holder, fasteners, vibration generator, spring element(s), and workpiece.The separating device according to the invention, in particular the bearing with a spring element having a progressive spring characteristic, ensures that the natural frequency of the separating device remains almost constant, especially within a predetermined range. The progressive spring characteristic causes the spring stiffness to be adjusted depending on the mass of the workpiece. This adjustment occurs automatically without the intervention of a control system or operator. When workpiece parts are separated from the remaining workpiece during the separation process, the mass of the remaining workpiece decreases. Because the workpiece holder is mounted on the support via a spring element with a progressive spring characteristic, the spring stiffness adjusts automatically with decreasing mass, so that the natural frequency remains almost unchanged. The support is preferably arranged in a stationary position.This could be, for example, a device frame or a floor, especially a hall floor.

[0008] By introducing vibrations into the workpiece holder, the workpiece is set into vibration. The workpiece components, which are only connected to the rest of the workpiece by a thin strip of material, are loosened by this vibration. The introduced vibrations can also be used to release parts that have become jammed in the rest of the workpiece due to (thermal) distortion. In particular, the spring element exhibits greater spring stiffness with a large workpiece mass (large deflection) than with a smaller mass (smaller deflection). The workpiece can be a sheet of metal.

[0009] It is understood that the workpiece has been processed before being placed in the separating device, for example by laser cutting or punching, in order to separate workpiece parts except for one or more material webs connecting the respective workpiece part to the rest of the workpiece. Alternatively or additionally, the workpiece may have completely separated workpiece parts that are only stuck in the rest of the workpiece due to distortion and that are to be removed in the separating device.

[0010] The workpiece holder can be designed as an impact plate. When this is set into vibration, the workpiece parts collide with the impact plate, thus breaking up material webs and separating the workpiece parts, which may be good parts or rejects, from the remaining workpiece.

[0011] Preferably, the workpiece can be attached to the underside of the workpiece holder. This allows the detached workpiece parts to simply fall out and be collected.

[0012] To enable the workpiece to be fastened and detached from the workpiece holder as quickly as possible, it is advantageous for the fastening means to include a clamping device. In particular, clamping jaws can be provided to secure the workpiece to the workpiece holder. The workpiece holder can have essentially the same surface area as the workpiece. However, it is also conceivable that the workpiece holder is dimensioned larger, so that workpieces of different sizes, especially those with a smaller surface area than the workpiece holder, can be attached to it, and workpiece parts can be removed from workpieces of different sizes.

[0013] The workpiece holder can be supported on the support by several, in particular at least two, preferably six spring elements. Several or all of the spring elements can have a progressive spring characteristic. If several spring elements are provided for support, each individual spring element can be smaller and therefore manufactured more cost-effectively than with a support using only a few spring elements.

[0014] At least one spring element can be designed as a rubber buffer, a helical spring with a variable coil diameter and / or wire diameter, a leaf spring, a leaf spring assembly, or a gas spring. Such spring elements are particularly easy to manufacture with a progressive characteristic curve. A helical spring with a variable diameter can be designed as a truncated cone, barrel, or waisted spring. A combination of variable coil diameter and variable wire diameter is also possible.

[0015] The vibration generator can be configured to vibrate the workpiece fixture at a frequency other than the natural frequency of the separating device. The separating device, or the system whose natural frequency is being considered, includes all components mounted on the spring element(s), i.e., the workpiece fixture, vibration generator, clamps, and the workpiece itself, including the spring elements. In particular, the excitation frequency Q at which the separating device is excited (by the vibration generator) can be several factors higher, for example, at least a factor of 2, than the natural frequency of the separating device. This allows the separating device to be operated in an isolation zone. This ensures that the transmission of vibrations to other machine components or, for example, a factory floor, and thus to adjacent machines, is prevented.The degree of isolation increases with the frequency ratio q = excitation frequency / natural frequency. This is referred to as the isolation range, which is reached at a frequency ratio of 2 or higher.

[0016] The vibration generator can also exhibit progressive behavior. It can be designed as an unbalanced motor. The rotational speed of the vibration generator can be varied to adjust the force amplitude and frequency applied to the workpiece fixture.

[0017] The spring elements can be selected in particular such that the overall system of the separating device has a natural frequency in the range of 2 to 4 Hz.

[0018] The invention also encompasses a method for removing workpiece parts from a workpiece, particularly a plate-shaped one. In this method, a workpiece comprising workpiece parts connected to the rest of the workpiece via at least one material web or clamped within the rest of the workpiece is attached to a workpiece holder, and the workpiece holder is set into vibration together with the workpiece. The workpiece holder is mounted on a support, particularly a stationary one, via at least one progressive spring element. Such a method allows workpiece parts to be removed from a workpiece without exciting the workpiece at resonance. Excitation at the resonance frequency should be avoided to prevent damage to a separating device used for removing workpiece parts.By using at least one progressive spring element, the natural frequency can be kept within a predetermined range, independent of the mass of the workpiece.

[0019] The workpiece can be clamped to the workpiece holder. Such clamping of the workpiece to the workpiece holder is particularly quick and easy.

[0020] The workpiece holder or separating device can be set into vibration, in particular by a vibration generator with a frequency higher than the natural frequency of the separating device. This prevents resonance in the operating range at nominal speed.

[0021] Operation in the supercritical range (i.e., a higher excitation frequency than the natural frequency) always results in the vibration generators passing through their resonance point during both startup and deceleration. However, this only occurs briefly and can be optimized through various control mechanisms (acceleration / deceleration ramps in the inverter).

[0022] The workpiece holder can be set into vibration at a frequency (excitation frequency) that is at least twice as high as the natural frequency of the separating device. In particular, the excitation frequency can be ten times higher than the natural frequency of the separating device.

[0023] A vibration generator that sets the workpiece holder into vibration can be operated within a predefined frequency range. This predefined frequency range could, for example, be 50 Hz to 60 Hz. However, significantly lower frequencies in the range of 25–30 Hz are also conceivable. By operating the vibration generator within a predefined frequency range and using a progressive spring element, it can be ensured that the excitation frequency of the vibration generator is always sufficiently far from the natural frequency, which can be kept almost constant by the progressive spring element. In this way, it can be ensured that the workpiece holder is not excited at its natural frequency, which could lead to undesirable behavior of a separating device.

[0024] Further features and advantages of the invention will become apparent from the following detailed description of exemplary embodiments of the invention with reference to the figures in the drawing, which show essential details of the invention, as well as from the claims. The features shown therein are not necessarily to scale and are depicted in such a way that the inventive features are clearly visible. The various features can be implemented individually or in any combination in variants of the invention.

[0025] The schematic drawing shows exemplary embodiments of the invention in various stages of use, which are explained in more detail in the following description.

[0026] They show:

[0027] Fig. 1 a side view of a separating device; Fig. 2 a perspective view from below of the separating device;

[0028] Fig. 3 shows a perspective view from above of the separating device.

[0029] Figure 1 shows a side view of a separating device 10. The separating device 10 has a workpiece holder 12 designed as an impact plate, on which at least one vibration generator 14 is arranged. In the illustrated embodiment, two vibration generators 14 are provided. The vibration generators 14 can be referred to as unbalance motors or exciters. A workpiece 16 is arranged on the underside of the workpiece holder 12. The workpiece 16 is attached to the workpiece holder 12 by means of fastening elements 18 designed as clamping elements. The workpiece holder 12 is mounted on a support 22 by means of spring elements 20 with a progressive spring characteristic. The support can be a fixture frame or a factory floor.

[0030] Workpieces 16 of different masses can be arranged on the workpiece holder 12. As the mass of a workpiece 16 increases, the spring elements 20 compress further. This increases the spring stiffness. Since the natural frequency is determined according to the formula f = , the natural frequency changes.

[0031]

[0032] The frequency f changes only slightly with increasing mass m and thus increasing spring stiffness c, and remains essentially constant.

[0033] The spring elements 20 shown in Figure 1 are designed as helical springs, with the diameter being smaller at the ends of the spring elements 20 than in a central region. This design of the spring elements 20 allows for a progressive spring characteristic. The excitation frequency at which the vibration generators 14 are excited is preferably significantly higher than the natural frequency f. In particular, the excitation frequency can be several times higher than the natural frequency. This ensures that the separation device 10 operates in a supercritical region or in an isolation region. The transmission of vibrations to adjacent machines or to a hall floor on which the separation device 10 is installed can thus be minimized.

[0034] Figure 2 shows a perspective view from below of the separating device 10. It is particularly evident that the workpiece 16 is attached to the underside of the workpiece holder 12, which is primarily plate-shaped, by several fasteners 18. The surface area of ​​the workpiece holder 12 is larger than the surface area of ​​the workpiece 16. In a previous process, workpiece parts 24 were largely cut out of the workpiece 16. The workpiece parts 24 are connected to the workpiece 16 only by one or more material tabs. By vibrating the workpiece holder 12 and thus the workpiece 16, the material tabs can be separated, allowing the workpiece parts 24 to fall out downwards. As more and more workpiece parts 24 are removed from the workpiece 16, the mass of the workpiece 16 decreases. As a result, the spring elements 20 compress less.The spring stiffness decreases. However, since both the spring stiffness and the mass decrease, the natural frequency remains essentially constant.

[0035] Figure 3 shows a perspective top view of the separating device 10. Here it can be clearly seen again that in the illustrated embodiment two vibration generators 14 are provided to set the workpiece holder 12 into vibration.

Claims

Patent claims 1. Separating device (10) for removing workpiece parts (24) from a workpiece (16), in particular a plate-shaped workpiece, comprising a workpiece holder (12), in particular a plate-shaped workpiece, and fastening means (18) for attaching the workpiece (16) to the workpiece holder (12), and a vibration generator (14) to set the workpiece holder (12) into vibration, as well as a support (22), in particular a device frame, on which the workpiece holder (12) is mounted via at least one spring element (20), wherein the spring element (20) has a progressive spring characteristic.

2. Separating device according to claim 1, characterized in that the workpiece holder (12) is designed as an impact plate.

3. Separating device according to one of the preceding claims, characterized in that the workpiece (16) can be attached to the underside of the workpiece holder.

4. Separating device according to one of the preceding claims, characterized in that the fastening means (18) comprise a clamping device.

5. Separating device according to one of the preceding claims, characterized in that the workpiece holder (12) is mounted on the support (22) via several, in particular at least two, spring elements (20), preferably six spring elements (20).

6. Separating device according to one of the preceding claims, characterized in that the at least one spring element (20) is designed as a rubber buffer, coil spring with non-constant diameter, leaf spring, leaf spring pack or gas spring.

7. Separating device according to one of the preceding claims, characterized in that the vibration generator (14) is configured to set the workpiece holder (12) into vibration at a frequency which is not equal to the natural frequency of the separating device (10).

8. Method for removing workpiece parts (24) from a workpiece (16), in particular a plate-shaped workpiece, in which a workpiece (16) which has workpiece parts (24) which are connected to the rest of the workpiece (16) via at least one material web or are clamped in the rest of the workpiece, is attached to a workpiece holder (12) and the workpiece holder (12) together with the workpiece (16) is set into vibration, wherein the workpiece holder (12) is mounted on a support (22) via at least one progressive spring element (20).

9. Method according to claim 8, characterized in that the workpiece (16) is clamped to the workpiece holder (12).

10. Method according to one of the preceding claims 8 or 9, characterized in that the workpiece holder (12) is set into vibration at a frequency which is greater than the natural frequency of the separating device.

11. Method according to one of the preceding claims, characterized in that the workpiece holder (12) is set into vibration at a frequency which is at least a factor of 2 greater than the natural frequency of the separating device.

12. Method according to one of the preceding claims 8 to 11, characterized in that a vibration generator (14) which sets the workpiece holder (12) into vibration is operated in a predetermined frequency range.

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