Measuring system for process monitoring and / or tool monitoring

Abstract

The present invention relates to a measuring system for process monitoring and / or tool monitoring, the measuring system comprising a groove formed in a machine tool and at least one measuring device force-lockingly retained in the groove. In order to be able to perform deformation measurements on the machine tool directly during a machining process, while the measuring system used for this purpose can be easily maintained and is nevertheless easy to use and provides reproducible measurement results, without negatively affecting the process of the machine tool, the present invention proposes a measuring system of the type in question in which the measuring device comprises a deformation element having two retaining blocks, which are opposite one another in a longitudinal orientation of the groove, and having at least one deformation body, which eccentrically connects the retaining blocks and can be brought into contact with a flank of the groove by means of a preload; a preloading device by means of which the retaining blocks can be or are loaded relative to one another; and at least one strain and / or force and / or displacement sensor attached to the at least one deformation body.

Description

[0001] Measuring system for process and / or machine monitoring

[0002] The present invention relates to a measuring system for process and / or machine monitoring, which has a groove formed in a processing machine and at least one measuring device held force-fittingly in the groove.

[0003] Process and machine monitoring on a processing machine is particularly effective when elastic deformations on the processing machine can be measured directly during a process. Although measurement systems and methods for this purpose are already known in principle, they are unsuitable for industrial application due to their low mechanical robustness, their influence on the machine characteristics, sometimes low sensitivity, and / or the use of immature sensor technology.

[0004] The publication WO 2015 / 149190 A1 describes a pretensioning device of a force measuring device that can be placed in a recess between machine parts. The pretensioning device has two arms arranged opposite one another and connected on one side by a tension / compression plate. A receiving pocket for accommodating a force sensor is formed between the arms. The arms each have a force introduction plate that is placed on an inner wall of the recess and an elastically bendable section that extends from the respective force introduction plate toward the receiving pocket. The elastically bendable section has a plurality of lamellae that are spaced from one another by elongated holes. A tool can act on the tension / compression plate with a tensile force, by means of which tool the elastically bendable section can be bent such that the two arms move toward one another, thereby allowing the pretensioning device to be inserted into the recess.By releasing the tensile force, the pre-tensioning device is clamped in the recess.

[0005] The document US 2005 / 0257392 A1 describes a force measuring device that can be inserted into a gap in a machine. The force measuring device has a centrally extending base with opposing connecting beams that are connected by a spring bent away from the base. The connecting beams can be brought into contact with an inner wall of the gap. A cap is applied to the center of this bent spring, which can be brought into contact with another inner wall of the gap. The base also has a centrally arranged tension beam, which is connected to the connecting beams at its opposite ends via two springs. A cavity is provided in the tension beam, in which a tension sensor is arranged that is connected to the springs of the base and is used to detect an axial tension.When a force is applied to the cap, the bent spring bends toward the base, causing the spring ends to exert a tensile force on the base via the connecting beams. This stretches the base's springs, and the tensile force is detected by the tension sensor.

[0006] From the publication WO 2020 / 120761 A1, a measuring system of the type specified at the beginning is known, which is used to record elastic deformations on processing machines, such as forming machines, inline. The measuring system has a measuring arrangement that is inserted into a T-slot of a processing machine. In a first variant, the measuring arrangement has two wedge elements that can be displaced against each other by means of a screw in a narrow area of ​​the T-slot, wherein the outer of these wedge elements is pressed against the inner flanks of the T-slot when the screw is pretensioned. The outer of the wedge elements has a pressure, force, or strain sensor. Another pressure, force, or strain sensor of this measuring arrangement is located on a pressure piece that is pressed against an undercut in the T-slot by means of the screw.In a second variant of the measuring arrangement, the shaft of a screw guided through a pressure piece of the measuring arrangement rests on the bottom of the T-slot, while the pressure piece is pressed against the undercut of the T-slot. Pressure, force, or strain sensors are provided on the pressure piece.

[0007] The measurement data acquired by the respective sensors is transmitted to an electronic evaluation unit. With the help of the electronic evaluation unit, measures can be initiated to compensate for deformations that occur during the machining process directly on the machine. The well-known measuring system has the advantage that its components are easily accessible from the outside and can therefore be easily replaced or repaired.

[0008] The known measuring system consists of a number of individual components, which makes its handling cumbersome and impairs the reproducibility of the measurements.

[0009] It is therefore the object of the present invention to provide a measuring system for process and / or machine monitoring that allows deformation measurements during a machining process directly on a machining machine, is easy to maintain and yet simple to handle and provides reproducible measurement results without negatively influencing the process of the machining machine.

[0010] The object is achieved by a measuring system for process and / or machine monitoring, which has a groove formed in a processing machine and at least one measuring device held in the groove in a force-fitting manner, wherein the measuring device has a deformation body which has two holding blocks lying opposite one another in a longitudinal alignment of the groove and at least one deformation body which connects the holding blocks eccentrically and can be brought into contact with a flank of the groove by a prestress, a prestressing device with which the holding blocks can be or are prestressed relative to one another, and at least one strain and / or force and / or displacement sensor which is attached to the at least one deformation body and / or to the prestressing device.

[0011] The two holding blocks hold the at least one deformation body at two spaced-apart locations on the deformation body. For example, the at least one deformation body can be designed as a beam convexly curved toward a groove flank or as a plate convexly curved toward a groove flank, which rests with its widest protrusion against the respective groove flank or can be brought into contact with the respective groove flank by the pretensioning device. In this case, the respective deformation body engages the two holding blocks in a decentralized manner.

[0012] The groove is positioned on the processing machine in such a way that during a process carried out on the processing machine, mechanical forces and / or deformations or displacements of components of the processing machine taking place during a process on the processing machine are effective on the groove in the form of an elastic deformation of at least one of the flanks of the groove.

[0013] The at least one deformation body is designed such that it is elastically deformable under the action of an external force. Accordingly, the at least one deformation body deforms elastically when the flank of the groove against which it rests also deforms elastically. If the at least one strain and / or force and / or displacement sensor is located on the deformation body, this elastic deformation can be detected by the at least one strain and / or force and / or displacement sensor, from which the magnitude and direction of the load and / or deformation acting on the groove and the corresponding machine part of the processing machine in which the groove is located can be determined.

[0014] Any body that deforms in response to a mechanical force and is easily clamped can be used as a deformation body. Depending on its shape and structure, the deformation body used can also be referred to as a force-transforming device, flexural joint, spring, or bending beam.

[0015] The pretensioning device allows the holding blocks to be clamped or tensioned relative to one another. Thus, when the holding blocks are clamped relative to one another, the at least one deformation body is also tensioned by the pretensioning device. This means that if at least one of the holding blocks is moved towards the other holding block by the pretensioning device, the at least one deformation body connecting the two holding blocks deforms or bends and presses against the flank of the groove against which it rests. This initially ensures that the measuring device can be clamped between the flanks of the groove. Furthermore, the pretensioning device can influence the intensity with which deformations of the flank of the groove are transmitted to the deformation body resting against it.Accordingly, the sensitivity of the at least one strain and / or force and / or displacement sensor attached to this deformation body can also be influenced by the pretensioning device.

[0016] The measuring system according to the invention has the advantage that it can also be easily retrofitted to existing processing machines. A groove can be selected that is located close to mechanically relevant machine components, thus enabling particularly advantageous process monitoring.

[0017] The measuring device of the measuring system according to the invention has a compact design and is easy to handle. For example, a variable preload can be easily applied to the at least one deformation body using the preload device to achieve reliable and easily analyzable measurement results.

[0018] In the measuring system according to the invention, all of its components are easily accessible from the outside and can therefore be easily maintained and replaced.

[0019] In the measuring system according to the invention, it is advantageous if at least one additional strain and / or force and / or displacement sensor is arranged on the pretensioning device. The additional strain and / or force and / or displacement sensor can be used to determine a pretensioning force applied to the at least one deformation body by the pretensioning device. This pretensioning force can then be related to the strain and / or force and / or displacement detected on the at least one deformation body, whereupon, for example, adjustments to the pretensioning device can be made.

[0020] If the preload device comprises a clamping screw, for example, the at least one further strain and / or force and / or displacement sensor can be arranged, for example, between a nut screwed onto the clamping screw and a stop on a first of the holding blocks. There, the at least one further strain and / or force and / or displacement sensor can detect the preload applied to the first holding block by the clamping screw. Preferably, the shaft of the clamping screw is guided through the first holding block. This provides guidance for the shaft of the clamping screw, making the measuring device mechanically stable.

[0021] In a preferred embodiment of the measuring system according to the invention, the measuring device has two deformation bodies connecting the holding blocks eccentrically, wherein the two deformation bodies are opposite one another, a hollow area is formed between the holding blocks and the deformation bodies and the clamping screw is guided through the hollow area.

[0022] This design has the advantage that it can be designed symmetrically with respect to the groove flanks, thus allowing measurement results to be recorded on both flanks of the groove. The clamping screw presses both deformation bodies against the respective flanks of the groove simultaneously by means of a preloading process.

[0023] It has proven particularly advantageous if the hollow area is oval in a top view of both deformation bodies. This means that in this embodiment, the two deformation bodies are each convexly curved outward toward the flanks of the groove, and the clamping screw runs centrally in the hollow area, between the two deformation bodies, and can thus advantageously be supported against the second retaining block without hindering deformation of the deformation bodies.

[0024] Alternatively, the deformation body can comprise only a single deformation body, which engages eccentrically with the opposing retaining blocks and extends, for example, in an arcuate or wave-like manner between the retaining blocks. The deformation body is in contact with one flank of the groove. In this embodiment, the retaining blocks each rest against the other flank of the groove.

[0025] In a preferred embodiment of the measuring system according to the invention, the at least one strain and / or force and / or displacement sensor attached to the at least one deformation body has at least one strain gauge, and the at least one further strain and / or force and / or displacement sensor arranged on the pretensioning device has at least one piezoelectric sensor. This means that in this embodiment of the invention, at least one strain gauge is attached to the at least one deformation body, and at least one piezoelectric sensor is arranged on the pretensioning device. The at least one strain gauge changes its electrical resistance when the respective deformation body bends. A particularly large measuring range can be detected by the at least one strain gauge.The at least one additional piezoelectric sensor arranged on the preloading device has the advantage of being highly sensitive. Thus, this embodiment of the invention can detect large strains and perform very sensitive measurements.

[0026] However, other sensors for strain, force, and / or displacement measurement, as well as other sensor combinations, may also be advantageous in the measuring system according to the invention. For example, strain gauges or other resistive sensors can be attached to both the at least one deformation body and the preloading device. Furthermore, a combination of at least one resistive sensor and at least one capacitive sensor for strain, force, and / or displacement measurement is possible. Furthermore, at least one piezoelectric sensor in combination with at least one inductive sensor for strain, force, and / or displacement measurement can be used in the measuring device.

[0027] A particularly large measuring range can be detected if the at least one strain gauge is mounted centrally on a side of the at least one deformation body facing the prestressing device.

[0028] Preferably, the at least one piezoelectric sensor is arranged in a recess of the first of the retaining blocks around the shaft of the clamping screw, wherein the at least one piezoelectric sensor is held in a clampable manner between a stop in the recess and a nut screwed onto the clamping screw. The nut can thus press against the at least one piezoelectric sensor, thereby preloading it.

[0029] In an advantageous variant of the measuring system according to the invention, at least one adjusting screw, oriented perpendicular to the longitudinal orientation of the pretensioning device, is guided through each of the holding blocks. The at least one adjusting screw can serve as a foot that can be supported on a bottom of the groove and with the aid of which the height of the measuring device in the groove can be adjusted. The at least one adjusting screw thus forms at least one height-adjustable support element.

[0030] It is advantageous if at least one positioning aid is arranged on each of the holding blocks, adjacent to opposite flanks of the groove. For example, an elastic element, such as an O-ring, can be used as a positioning aid around each of the holding blocks, adjacent to opposite flanks of the groove. This element can be made of plastic or rubber, for example, and does not affect the elastic deformation behavior of the measuring system or the T-slot.

[0031] In a further advantageous embodiment of the invention, a cover is applied to the measuring device. This cover comprises a cover plate covering the hollow area and clamping elements extending from the cover plate, into which the clamping screw is clamped. The cover plate can prevent dirt from entering the measuring device. The cover plate can be easily clamped onto the measuring device using the clamping elements. Alternatively, the cover can also be screwed, glued, or magnetically closed.

[0032] The measuring system is particularly easy to handle if the deformation body is monolithic. This means that in this embodiment of the invention, the holding blocks and the at least one deformation body are formed from a single block, thus not having to be constructed from multiple elements that can be moved relative to one another, as is the case, for example, with the wedge arrangement described in WO 2020 / 120761 A1.

[0033] It has proven particularly advantageous if at least one deformation body is curved toward a flank of the groove even without preload. This allows the measuring device to be clamped between the flanks of the groove without preload.

[0034] Advantageous embodiments of the present invention are explained in more detail below with reference to figures, wherein Figure 1 schematically shows an embodiment of the measuring system according to the invention in a plan view;

[0035] Figure 2 schematically shows an embodiment of the measuring system according to the invention in a front view; and

[0036] Figure 3 schematically shows a cover of a measuring device of an embodiment of the measuring system according to the invention in a perspective view.

[0037] Figure 1 schematically shows a top view of a measuring system 1 designed according to the present invention. The measuring system 1 has a measuring device 3, which is inserted into a groove 2 of a processing machine. In the embodiment shown, the groove 2 is a T-slot, such as a T-slot for clamping a tool of the processing machine. The groove 2 has a straight longitudinal orientation L, which is delimited laterally by a flank 21, 22. In the embodiment shown, the measuring device 3 is located in the narrower region of the groove 2.

[0038] As can be seen in Figure 2, in which the measuring system 1 is shown schematically in a front view, the flanks 21, 22 of the groove 2 do not necessarily have to run straight to a bottom 23 of the groove 2, but can have different distances from one another both in the depth direction T of the groove 2 and in the width direction B of the groove 2.

[0039] The measuring device 3 comprises a deformation body. In the embodiment shown, the deformation body comprises two holding blocks 4, 5 located opposite one another in the longitudinal direction L of the groove 2, and two deformation bodies 61, 62 connecting these holding blocks 4, 5 in the longitudinal direction L of the groove 2. In other embodiments of the invention not shown, the holding blocks can also be connected by only one deformation body.

[0040] In the embodiment shown, the deformation body is monolithic.

[0041] In other embodiments of the present invention not shown, the deformation body can also be formed in several parts, wherein, for example, the holding blocks are formed separately and are connected to at least one deformation body, for example by a screw or rivet connection.

[0042] In the embodiment shown, the deformation body is made of stainless steel, but can also be made of other materials.

[0043] In the embodiment shown, the deformation bodies 61, 62 are designed as convexly curved plates in the direction of the flanks 21 and 22, respectively. They connect the support blocks 4, 5 off-center. Therefore, in the embodiment shown, an oval hollow area 9 is formed between the deformation bodies 61, 62 in the plan view shown in Figure 1.

[0044] A clamping screw 7, which acts as a pretensioning device, is passed through this hollow area 9 in the longitudinal direction L of the groove 2. In the embodiment shown, a shaft 72 of the clamping screw 7 runs centrally through the hollow area 9. The clamping screw 7, on the one hand, has its shaft 72 passed through the first of the holding blocks 4, and on the other hand, its screw head abuts the second of the holding blocks 5. By appropriately tightening the nut 71 screwed onto the shaft 72, the two holding blocks 4, 5 are moved towards one another. As a result, the two deformation bodies 61, 62 bend further outwards in the direction of the flanks 21, 22 of the groove 2 until they rest against them. The measuring device 3 is thus clamped between the flanks 21, 22 of the groove 2.

[0045] In a recess 41 of the first of the holding blocks 4, one or more piezoelectric sensors 82 are arranged around the shaft 72 of the clamping screw 7. A lower one of the piezoelectric sensors 82 is adjacent to a stop 42 in the recess 41.

[0046] The piezoelectric sensors 82 are preloaded by means of the nut 71. A cover or a washer, for example, can be provided between the nut 71 and the piezoelectric sensors 82. In the embodiment shown, the piezoelectric sensors 82 are annular piezo elements. In other embodiments of the present invention (not shown), piezo foils can also be used as piezoelectric sensors 82.

[0047] Furthermore, in the embodiment shown, a strain gauge 83 is located on the shaft 72 of the clamping screw.

[0048] Both the piezoelectric sensors 82 and the strain gauge 83 can measure the preload force applied by the preload device to the deformation bodies 61, 62. This measurement is useful because the preload force exerted by the preload device on the deformation bodies 61, 62 can change during a longer measurement. If a change in the preload force is detected during the measurement, the preload device can be adjusted.

[0049] In other embodiments of the present invention not shown, other or further sensors may also be provided on the pretensioning device.

[0050] In the embodiment shown, a strain gauge 81 is arranged centrally on each of the deformation bodies 61, 62. However, the respective strain gauge 81 can also be arranged at a different location on the deformation bodies 61, 62. The respective strain gauge 81 can be used to detect the deflection of the deformation bodies 61, 62.

[0051] The bending of the deformation bodies 61, 62 can change as a result of vibrations or deformations on the processing machine and thus of vibrations or deformations on the groove 2 located therein and can be detected directly inline by the respective strain gauge 81.

[0052] In the embodiment shown, the longitudinal direction of the strain gauges 81 is identical to the longitudinal direction of the deformation bodies 61, 62. In other, not shown, embodiments of the present invention, at least one further strain gauge can be attached to at least one of the deformation bodies 61, 62, orthogonal to the strain gauges 81 shown. In the embodiment shown, the strain gauges 81, 83 used are semiconductor-based, but other strain gauges, such as standard wire strain gauges, can also be used instead.

[0053] Furthermore, in the embodiment shown, the strain gauges 81, 83 are each glued on.

[0054] Furthermore, in the embodiment shown, the strain gauges 81 are each located on the side of the deformation bodies 61, 62 pointing inwards, i.e. in the direction of the clamping screw 7.

[0055] In the embodiment shown, a positioning aid 14, which here is designed in the form of elastic rubber elements, is arranged around each of the holding blocks 4, 5. However, other positioning aids, such as strips or other spacers, are also possible; furthermore, the positioning aids can also be omitted.

[0056] In the embodiment shown in Figure 2, the measuring device 3 is supported relative to a base 23 of the groove 2 by means of an adjustment system, which in the embodiment shown is designed in the form of adjusting screws 10. The adjusting screws 10 run perpendicular to a longitudinal alignment I of the clamping screw 7. The adjusting screws 10 are screwed into bores 16 in the holding blocks 4, 5. The height of the measuring device 3 in the groove can be adjusted using the adjusting screws 10.

[0057] Figure 3 schematically shows a cover 11 for the measuring device 3, which can optionally be used in the measuring system 1 according to the invention. The cover 11 has a cover plate 12, which serves to cover the hollow area 9. Clamping elements 13 extend from the cover plate 12 and are clamped onto the clamping screw 7. However, the cover plate 12 can also be screwed tight.

[0058] Below the deformation body is a measuring electronics unit of the measuring system 1 (not shown in the figures). The measuring electronics typically comprise at least one AD converter. The measuring electronics unit is preferably formed on a circuit board. Each of the sensors 81, 82, 83 of the measuring system 1 can be individually calibrated via the measuring electronics unit.

[0059] A signal cable 15 connected to the measuring electronics protrudes from the first of the holding blocks 4. Instead of the signal cable 15, a socket can also be provided via which the measured measurement signals can be forwarded as a protocol.

[0060] Furthermore, in an embodiment of the invention, which is not shown here, the signal can also be transmitted in another way, for example by means of radio signal transmission or by means of structure-borne sound transmission.

Claims

Patent claims 1. Measuring system (1) for process and / or machine monitoring, which has a groove (2) formed in a processing machine and at least one measuring device (3) held in the groove (2) in a force-locking manner, characterized in that the measuring device (3) - a deformation body which has two holding blocks (4, 5) opposite one another in a longitudinal orientation (L) of the groove (2) and at least one deformation body (61, 62) which connects the holding blocks (4, 5) off-center and can be brought into contact with a flank (21, 22) of the groove (2) by a prestress; - a pre-tensioning device with which the holding blocks (4, 5) can be or are tensioned relative to one another; and - has at least one strain and / or force and / or displacement sensor which is attached to the at least one deformation body (61, 62).

2. Measuring system according to claim 1, characterized in that at least one further strain and / or force and / or displacement sensor is arranged on the pretensioning device.

3. Measuring system according to one of the preceding claims, characterized in that the pretensioning device has a clamping screw (7) onto which a nut (71) is screwed, which presses directly or indirectly against a first of the holding blocks (4), wherein a screw head of the clamping screw (7) presses against a second of the holding blocks (5).

4. Measuring system according to claim 3, characterized in that the shaft (72) of the clamping screw (7) is passed through the first of the holding blocks (4).

5. Measuring system according to claim 3 or 4, characterized in that the measuring device (3) has two of the deformation bodies (61, 62) connecting the holding blocks (4, 5) eccentrically, wherein the two deformation bodies (61, 62) lie opposite one another, a hollow area (9) is formed between the holding blocks (4, 5) and the deformation bodies (61, 62), and the clamping screw (7) is guided through the hollow area (9).

6. Measuring system according to claim 5, characterized in that the hollow region (9) is oval in a plan view of both of the deformation bodies (61, 62).

7. Measuring system according to claim 1, characterized in that the deformation body has only a single deformation body which engages off-center on the opposing holding blocks (4, 5) and is in contact with a flank (21) of the groove (2), the holding blocks (4, 5) each resting on the other flank (22) of the groove (2).

8. Measuring system according to claim 2, characterized in that the at least one strain and / or force and / or displacement sensor attached to the at least one deformation body (61, 62) has at least one strain gauge (81) and the at least one further strain and / or force and / or displacement sensor (82) arranged on the pretensioning device has at least one piezoelectric sensor (82).

9. Measuring system according to claim 8, characterized in that the at least one strain gauge is attached to the at least one of the deformation bodies (61, 62) on a side facing the pretensioning device (7) in the center of the at least one of the deformation bodies (61, 62).

10. Measuring system according to claims 3 or 4 and claim 8 or 9, characterized in that the at least one piezoelectric sensor (83) is arranged in a recess (41) of the first of the holding blocks (4) around the shaft (72) of the clamping screw (7), wherein the at least one piezoelectric sensor (83) is held clampably between a stop (42) in the recess (41) and a nut (71).

11. Measuring system according to one of the preceding claims, characterized in that at least one adjusting screw (10) aligned perpendicular to a longitudinal orientation (I) of the pretensioning device (7) is guided through each of the holding blocks (4, 5).

12. Measuring system according to claim 5, characterized in that a cover (11) is applied to the measuring device (3), which cover has a cover plate (12) covering the hollow area (9) and clamping elements (13) extending from the cover plate (12) into which the clamping screw (7) is clamped.

12. Measuring system according to one of the preceding claims, characterized in that at least one positioning aid (14) is arranged on each of the holding blocks (4, 5), each adjacent to opposite flanks (21, 22) of the groove (2).

13. Measuring system according to one of the preceding claims, characterized in that the deformation body is monolithic.

14. Measuring system according to one of the preceding claims, characterized in that the at least one deformation body (61, 62) is curved in the direction of a flank (21, 22) of the groove (2) even without prestressing.

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