阅读说明：本技术 用于监测标准件的系统 (System for monitoring standard parts ) 是由 S·舒尔茨 D·西托维奇 M·阿伦斯潘 斯特凡·诺布斯 于 2020-10-09 设计创作，主要内容包括：一种用于测量在压制设备(1)中的工具(2)的未对准的系统,该工具(2)至少包括第一部分(3)和第二部分(4),第一部分和第二部分可以通过引导装置以被引导的方式相对于彼此移动,该引导装置包括设置在第一部分(3)中的至少一个导柱(10),所述至少一个导柱在设置在第二部分(4)中的导套(12)中被引导,其中该系统包括设置为检测工具(2)的未对准的测量装置(20)。根据本发明,该测量装置(20)被直接安装在引导装置处。(A system for measuring misalignment of a tool (2) in a pressing apparatus (1), the tool (2) comprising at least a first part (3) and a second part (4), which parts can be moved in a guided manner relative to each other by means of a guide arrangement, which guide arrangement comprises at least one guide post (10) arranged in the first part (3), which guide post is guided in a guide sleeve (12) arranged in the second part (4), wherein the system comprises a measuring arrangement (20) arranged to detect misalignment of the tool (2). According to the invention, the measuring device (20) is mounted directly on the guide device.)

1. A system for measuring misalignment of a tool (2) in a pressing apparatus (1), the tool (2) comprising at least a first part (3) and a second part (4), the first part (3) and the second part (4) being movable in a guided manner relative to each other by means of a guide arrangement, the guide arrangement comprising at least one guide post (10) provided in the first part (3), the at least one guide post being guided in a guide sleeve (12) provided in the second part (4), the system comprising a measuring arrangement (20) arranged to detect misalignment of the tool (2), characterized in that the measuring arrangement (20) is mounted directly at the guide arrangement.

2. System according to claim 1, wherein the measuring device (20) is mounted at the at least one guide post (10).

3. System according to claim 1 or 2, wherein the measuring device (20) is mounted in a longitudinal bore (14), the longitudinal bore (14) being provided in the at least one guide post (10).

4. A system according to claim 3, wherein the measuring device (20) is firmly fixed in the longitudinal bore (14) by means of a holding element (26).

5. The system according to any one of claims 1 to 4, wherein the measurement device (20) is configured as a strain gauge sensor (24) comprising a cylindrical structure (22) and at least one strain gauge (26) attached thereto.

6. The system of claim 5, wherein a pair of strain gauges (24) are attached on opposite sides of the cylindrical structure (22).

7. The system according to any one of claims 1 to 4, wherein the measurement device (20) is configured as a capacitive sensor (30) comprising a first cylinder (32) having a first capacitive plate (36) and a second cylinder (34) having a second capacitive plate (38), the first capacitive plate (36) and the second capacitive plate (38) being separated from each other by a distance (d).

8. The system according to any one of claims 1 to 4, wherein the measuring device (20) is configured as a fiber optic sensor (40).

9. The system according to claim 8, wherein the fiber sensor (40) is configured as an interferometric sensor, in particular a low coherence interferometric sensor.

10. System according to any one of claims 1 to 9, wherein the measuring device (20) is adapted to determine a deflection and/or deviation of the squareness of the at least one guide post (10) with respect to the first part (3) of the tool (2), in particular the magnitude of the deviation and the direction of the deviation.

11. The system according to any one of claims 1 to 10, wherein the measuring device (20) is configured to determine a deviation during setup of the tool (2).

12. The system according to any one of claims 1 to 11, wherein the measuring device (20) is adapted to be connected to a processing unit for transmitting signals via wireless transmission.

13. The system according to any one of claims 1 to 12, wherein the measuring device (20) is configured to determine a temperature of the at least one guide pillar (10) to which the measuring device (20) is attached.

Technical Field

The invention relates to a system for monitoring standard parts, in particular for measuring the misalignment of tools in press devices for moulding and/or moulding, wherein the deformation, deflection and/or strain of a guide is measured.

Background

Press tools (press tools) are used in hydraulic, pneumatic and/or mechanical presses (presses) to produce parts, in particular mass-produced sheet metal parts, by blanking, punching, bending, forming, stamping, etc. Processing equipment for film pressing, pressing or molding includes a film pressing tool, a pressing tool, an injection molding tool or a die-casting tool. Typically, the tool comprises a plurality of plates (also known as tool halves) which are movable relative to each other and which are composed of at least a first part and a second part, in particular a punching die or a blanking die or a mold (mold). In the machining stroke, the movement of the first part and the second part is guided by guide means from a closed position, in which the respective separating surfaces of the two parts are pressed against each other, to an open position and vice versa. The guiding means comprise a plurality of guide posts (guide pilars) which are, for example, mounted in the first part and are guided into corresponding guides, in particular guide sleeves (guide bush) provided in the second part. The guide post and guide sleeve form a guide means which is used to precisely guide and align at least two parts of the tool so that they can be precisely centered in the closed position. Thus, the surface pairs (surface pair) of the tool and the die set (in particular of the first part and of the second part) and the parallelism of the support surface are monitored to verify that the first part and the second part are (or are not) superimposed (identical) and/or consistently positioned with respect to each other. Furthermore, the squareness (squareness) of the guide device can be ensured.

It is known to form the guide post as a cylinder protruding from the first part. The guide sleeve arranged in the second part can be formed by a cage with rolling bodies, wherein the rolling bodies can be balls or rollers, in particular balls or rollers inserted in a row. It is important that the guiding means are configured without gaps of guiding studs in the respective guide sleeves of the second part for stamping or moulding tools with high quality requirements on the workpiece.

To further ensure that the first and second parts of the tool are accurately aligned with each other during the closing and opening operations, additional centering devices may be provided. However, the forces acting on the parts of the tool during pressing can lead not only to a deformation of the tool itself, but also to a deformation of the guide means.

EP1980339A relates to a press-forming apparatus and method which measures the strain of the tool generated by the press film force generated by the press during press working, the reaction force generated by the material to be worked, and the resulting (deforming) deformation reaction which leads to elastic deformation of the tool. It is known from this document that strain measuring cells are provided in components of the press to be controlled, in particular the punch (punch) and/or die (die) of the press, in order to determine the strain amplitude (strain) of the aforementioned components that occurs during press forming. The strain measuring unit may be provided as a piezoelectric sensor or a strain gauge, or as an FBG sensor (Faber Bragg Grating sensor) using an optical fiber, and may be configured to measure strain generated by one of a punch and/or a die of the press mold. However, deviations (deviations) of the parallelism of the surface pairs and/or the squareness of the guide means relative to the mould may also occur, for example when the tool is mounted in a press, and these deviations cannot be detected by the disclosed method.

EP3042756A describes a method for detecting and determining the inclination of the cushion pad (cushionpad) of a press machine (press machine). Information of a plurality of corresponding height positions in the vertical direction, which are detected by the height position detectors at a plurality of different horizontal positions, can be used to calculate the inclination of the cushion pad of the die cushion apparatus (die cushion device).

DE4415577A describes an apparatus for compensating or adjusting the deflection in a press to achieve uniformity (evenness) of the tool holder. The device comprises a path or bending sensor, in particular a path or bending sensor which is locally mounted in a position of maximum elastic deformation.

In summary, it is well known in the prior art to provide detection means in the lamination tool and/or in the frame of the pressing apparatus to detect deformations occurring during operation of the pressing apparatus. However, detection devices associated with guiding devices, such as guide posts and guide sleeves of a pressing apparatus, are hardly known. Errors or misalignment of the tool when it is installed in the press apparatus and during operation can lead to inaccuracies in the dimensions of the press formed article (article) and to damage or destruction of the forming or pressing tool, or at least to increased wear of the forming or pressing tool and ultimately to higher costs due to the need to replace the tool. In particular, deviations of the parallelism of the surface pairs and/or the support surfaces and deviations of the squareness of the guide posts can cause serious problems in terms of the precision of the shaped article.

Disclosure of Invention

It is therefore an object of the present invention to provide a system for measuring tool misalignment in a press apparatus during set-up (set-up) and operation. In the following, the term pressing apparatus also relates to a press, a moulding machine (molding machine) or the like. In particular, the system has sufficient robustness (robust) to withstand oily atmospheres and detergents, and can be used to operate forming or pressing tools at high accelerations and speeds, as well as high stroke frequencies. It is a further object of the invention to provide a system which not only can determine the deformation of the guiding means with high accuracy, but also can detect the direction of the deformation.

These problems are solved by a system for measuring misalignment of a tool in a press apparatus, wherein the tool comprises at least a first part and a second part, the first part and the second part being movable in a guided manner relative to each other by means of a guide arrangement, the guide arrangement comprising at least one guide post provided in the first part, the at least one guide post being guided in a guide sleeve provided in the second part, the system comprising a measuring arrangement arranged to detect misalignment of the tool, the measuring arrangement being mounted directly at the guide arrangement.

According to the present invention, these problems are solved by a system for measuring the misalignment of standard parts used in a press. In the following, the term standard part denotes guiding means, such as guide posts and guide sleeves, for guiding tools in a pressing apparatus, for example a punching tool or an injection mould. These guiding means not only perform guiding within the tool, but also exert a considerable influence on the dynamic behavior of the tool, in particular a tool configured as a die and/or matrix. Problems such as die tilting (where the axis of the die and the axis of the die of the pressing apparatus are no longer aligned) may have different causes. For example, multiple tools, and particularly portions of the tools, are not mounted in superimposition with one another, resulting in stress and deflection of the guidepost. Furthermore, problems may also arise during operation of the tool, such as problems with backlash or deviations from folding due to thermal effects, and problems due to uneven punching forces along the length of the punching tool or due to tilting of one of the parts of the tool. Since the die press or the mold press (mold press) can exhibit a certain amount of guide play as a result of aging, the tool halves no longer overlap one another, which can lead to bending of the guide posts during operation. The system according to the invention is configured to measure and monitor misalignments such as deflections, deformations and/or deviations, for example with respect to the squareness directly at the guiding means, in particular at guide columns and/or guide sleeves in the pressing apparatus. Furthermore, the system is also suitable for measuring the surface temperature of the guide pillar and the direction of deflection, deformation and/or deflection. Thus, the measuring device is mounted at the guiding means, in particular at the guide post, wherein the measuring device may be mounted in a fixed manner or in an alternative embodiment be releasable.

Several types of measuring devices are known, which comprise various types of sensors embedded or attached to the structure in order to detect and monitor deformations, deflections or misalignments (preferably at an early stage), so that timely interventions can be made to avoid further damages. Known devices for these purposes are strain gauge sensors, piezoelectric sensors and optical fiber sensors.

The system for measuring misalignment of tools in a press apparatus according to the invention comprises measuring means to monitor deflection, deformation and/or deflection, and stress and/or temperature, which are mounted directly at the guiding means, in particular at the guide posts. According to one embodiment of the invention, a longitudinal bore is provided from the free end of at least one guide post, which is preferably configured as a blind or through bore coaxial with the longitudinal axis of the guide post. The longitudinal bore is configured to receive a measuring device, wherein the diameter d1 of the longitudinal bore is smaller compared to the diameter of the guide post. In particular, the diameter d1 of the longitudinal bore is in the range of 0.1mm to 10.0 mm.

One suitable measurement device is a strain gauge with a surface stress sensing element. Generally, a strain gauge includes a thin metal pattern or semiconductor, and resistance, capacitance, and the like may significantly change when it is deformed. Deformation is generally considered a measure of strain and therefore also a measure of the force applied to the structure to which the strain gauge is attached. Strain gauge sensors are provided on a structure to perform accurate and reproducible measurements of stress variations and are known for measuring, for example, acceleration, pressure, tension and force. Different types of strain gauges are known, such as semiconductor strain gauges, nanoparticle strain gauges and/or capacitive strain gauges, and fiber optic sensing (fiber optic sensing) that measures strain along an optical fiber.

According to one embodiment of the invention, the measuring device is configured as a strain gauge sensor, wherein at least one strain gauge is attached to a cylindrical base (pillar shaped substrate) to form the sensor, which cylindrical base can be received in a longitudinal bore of at least one guide pillar. The cylindrical base and the at least one strain gauge may be made in one piece using a suitable technique. However, they may be manufactured separately and then attached to each other by welding, gluing, or other known techniques. Further, the cylindrical base may be configured as a flexible cylinder (cylinder) and may be positioned in any suitable location in the longitudinal bore of the at least one guide post. Advantageously, the cylindrical base may be configured to have a lower stiffness than the guide pillar, in particular, approximately at least an order of magnitude lower. Thus, the deformation of the guide posts is transferred to the substrate without resistance (resistance) or loss. Preferably, the cylindrical base is configured as a cylinder extending from the top to the bottom of the longitudinal bore, in particular from the free end of the guide post to the end of the blind bore, or its bearing in the first and/or second part of the tool. The strain gauge sensor is fixedly mounted in the longitudinal bore of the guide post by a retaining means, in particular on the top or free end of the guide post and in particular on the opposite end of the bottom of the guide post. The retaining means may be provided as threads, clamping means, adhesive or the like.

The strain gauges may be designed as printed, deposited or laser-structured (laser-structured) strain gauges. In one embodiment of the strain gauge sensor, 3D printing technology (3D printing technology) for the conductive material is used to print the strain gauge sensor. By printing the sensor structure directly on the substrate material, a high degree of design freedom and flexibility can be achieved.

A suitable deposition method comprises applying a deposition mask on the substrate surface of the pillar-shaped structures of the sensor, and depositing a strain gauge material having a resistance varying with stress on at least a portion of the substrate surface exposed by the holes in the deposition mask. The deposition may be performed by chemical vapor deposition and/or physical vapor deposition. The deposition method may use a laser patterned mask, and vapor deposited layers of dielectric material and sputtered conductive film(s) to fabricate strain gauges of high sensitivity on substrate surfaces having different compositions.

The strain gauge may also be manufactured by laser material removal of a homogenous (homogenous) conductive film, wherein in a first step the conductive film is homogeneously deposited on the substrate surface, for example by vacuum deposition. In a next step, the conductive material is removed, so that the measurement structure is formed with an insulating material between them.

In order to accurately detect the change in resistance, it is known to connect four strain gauges in a bridge arrangement and measure the differential voltage between the center terminals (terminals). Preferably, at least two strain gauge sensors are attached to opposite sides of a cylindrical base, which is received in a longitudinal bore in at least one guide post subjected to a bending force, such that the opposing pair (opposite pairs) are in compression or tension, thereby providing a maximum differential voltage for a given strain. In some cases, it may be necessary to take into account the effect of temperature on the resistance of the metal conductor, for example as an error factor, or to provide a specific (certain) configuration for all strain gauges and/or strain gauge sensors.

The use of strain gauge sensors as measuring devices has some major advantages, for example, that these sensors and their applications are state of the art and can thus be built up in a simple manner, with no or only few size restrictions in mind, that these sensors are inexpensive to manufacture, and that they offer high flexibility in sensor design and the possibility of printing these sensing elements on almost any surface.

In another embodiment according to the invention, the measuring device inserted into the longitudinal bore in the at least one guide post is configured as a capacitive sensor. The capacitive sensor includes a first cylinder having a first end face and a second cylinder having a second end face, which are inserted into the longitudinal holes and fixed to the ends of the guide pillars, respectively, by holding means such that the first end face and the second end face are oriented parallel to each other at a predetermined distance. Preferably, the first end face and the second end face are produced by diagonally (diagonally) cutting the cylinder into the first cylinder and the second cylinder, which increases the area of the end faces and the capacity of the capacitive sensor. The first and second columns represent plates of a capacitor, in particular two conductive elements, e.g. metals or conductive polymers, which are separated from each other by a short distance by a dielectric, such as a liquid, a gas (e.g. air), or a solid. Due to the deformation of the at least one guide pillar equipped with the capacitive sensor due to an external force, the distance between the two conductive elements, in particular the distance between the first end face as one capacitive plate and the second end face as the other capacitive plate, changes. Alternatively, additional forms of capacitive plates may be provided, particularly for narrow apertures. For example, the vertical capacitive plates may form a structure (a two matching comb structure) with two combs and variations thereof. Due to deformation or positional deviation of the guiding means, the capacitive plates of the capacitive sensor will experience translation and rotation, which will affect the distance between the capacitive plates. The deformation that produces a change in distance can be detected by measuring a change in the resistance value of the capacitance and can be evaluated as a function of the magnitude of the displacement and preferably also as a function of the direction of the displacement or deflection.

The change in resistance value is determined by measuring the capacitance voltage-step response of the charging and discharging process relative to a known rectangular signal generated by an oscillator as the original signal at a predetermined or reference frequency. The change in capacitance value is directly related to the distance between the capacitive plates of the capacitive sensor. According to this embodiment, two basic RC-circuits are used for determining the charging and discharging behavior, each comprising a resistance with equal resistance values, but comprising a capacitance with different capacitance values, in particular a reference capacitance and a capacitance subject to deformation. Since the area of the capacitive plates and the resistance of the resistors they comprise are kept constant, a change in the distance between the capacitive plates will produce a change in the detected signal. These can be accurately measured with respect to the raw signal and the reference capacitor.

The advantage of using the so-called post-deformation difference between frequency and reference frequency is that all possible error sources are minimized. As is well known, the oscillation frequency of an oscillation circuit is a frequency according to impedance including, in addition to a resistance component (component) between electrodes, an inductance component and a capacitance component between the electrodes. Since the inductance component and the resistance component are constant, the oscillation frequency is affected only by the change in capacitance in the circuit. The difference between the frequency after deformation and the reference frequency substantially corresponds to the difference in the electrical capacitance (capacitance) only of the sensor unit before and after deformation and is therefore directly related to the distance between the plates of the capacitive sensor unit. Signal noise and external error sources can be minimized by using the difference as a measurement setting (measurement setup).

In another embodiment according to the invention, the measuring device accommodated in the longitudinal bore of the at least one guide post is configured as a fiber optic sensor. The fiber optic sensor is configured to measure strain along an optical fiber that may be embedded in a longitudinal bore disposed in at least one of the plurality of guide posts. Typically, optical sensor devices are based on detecting modifications (modulations) or modulations in certain characteristics of the light. Transmitted or reflected light may be modulated by changes in its amplitude, phase, frequency and/or polarization state (polarization state). Fiber optic sensors are immune to electromagnetic interference, are chemically inert (chemical insert), are high temperature resistant, and may be small and light, and exhibit excellent transmission capabilities, and may provide multiple measurement points along a single fiber that may be multiplexed to provide distributed measurements with high spatial resolution.

In general, fiber optic sensors include an integrated or separate transducer device (transducer device) having at least one measuring fiber, an optical connector, and a processing unit.

One design of fiber optic sensors for measuring the deformation of the guide posts is configured with a fiber, called a measurement fiber, which is in mechanical contact with the cylindrical structure itself. The measuring fibre is attached by its two ends and is preferably preloaded between its two ends. Alternatively, more than one measuring fibre may be provided. Due to the bending of the measuring device caused by the deformation of the cylindrical structure, one measuring fiber is elongated. The measurement fiber may be configured to provide a plurality of measurement points by performing a plurality of optical reflections along the length of the measurement fiber.

Another embodiment of the measuring device comprises another fibre, the so-called reference fibre, which is loosely placed in the same cylindrical structure, so that its length is not affected by deformation and/or bending. The measuring fiber and the reference fiber can be implemented in one measuring device, in particular in one and the same cylindrical structure. Advantageously, in this embodiment, the temperature-induced length change is equal for the measurement fiber and the reference fiber, respectively, so that no further temperature compensation has to be taken into account.

Alternatively, the measuring fibers are implemented in the measuring device, while the reference fibers can be arranged independently, so that the space requirement of the measuring device is small. Light from the light source is guided to the sensor and back to the processing unit by guiding elements, wherein the guiding elements are at least optical fibers and optical coupling means.

The processing unit of the measuring device may comprise an Interferometer, such as a Fabry-perot Interferometer (Fabry-perot-Interferometer), and may further comprise a converter unit for converting the optical signal from the measuring fiber into an electrical signal, and an electrical signal processor for further processing the received signal. According to one embodiment, a fabry-perot interferometer may be configured for use with one or several or a continuous distribution of wavelengths. This allows an absolute measurement of the elongation (elongations) of the measuring fibers, which is greater than the wavelength of the light used.

Another design is based on Fiber Bragg Grating Technology (Fiber Bragg Grating Technology) to measure strain and temperature, using a Fiber with a periodic refractive index perturbation pattern engraved (modulated) in the core (core) to diffract an optical signal in a mode guided at a specific wavelength into other modes. Other designs of fiber optic sensors have also been proposed to provide an interaction region between light and an object under test (measurand).

Another type of fiber optic sensor is the low-coherence interferometer (low-coherence interferometer), which is based on splitting the power of a low-coherence source into the measurement and reference fibers of the interferometer by a fiber coupler (fiber coupler). Light reflected by the reflectors in the structure is recollected (recollect) by the measurement fiber, light from both the measurement and reference fibers is coupled back into the fiber coupler, and a portion of the light is redirected to the detector. Due to the finite coherence length of the light source, optical interference is only observed when the optical path length of the light beam reflected by the structured reflector and the reference mirror is different from and less than the coherence length.

According to one embodiment of the invention, the measuring device is configured as a sensor unit modulating an electrical characteristic (e.g. resistance and/or capacitance), thus being provided passive. These sensors are powered by electrical energy and the signals generated are transmitted and processed, in particular by means of amplifiers and processing units. The connection of the sensor unit to the power supply and/or the processing unit can be provided by wired transmission or by wireless transmission.

According to a preferred embodiment of the invention, the measuring means of the system are adapted to determine the deformation, deflection and/or deviation of the squareness of at least one guide post with respect to the first part of the tool, in particular the magnitude of the deviation and the direction of the deviation. The deviation may be determined during the setting of the tool and during the operation of the pressing device.

Furthermore, the measuring device is adapted to be connected with the processing unit for transmitting signals via wireless transmission.

In another embodiment, the temperature can be measured by known measuring devices and measuring methods of the state of the art, in particular using platinum resistance thermometers. The temperature is detected independently of the measurement of the deformation of the guide pillar. Thus, a temperature correction can be applied directly to the signals from the strain gauge resistances, optical structures, wavelengths and/or capacitances by the evaluation unit or the processing unit.

According to the invention, the direction of deformation acting on the guide post can be calculated by the geometrical alignment of the measuring device within the guide post, and the magnitude of the deformation can be evaluated based on the longitudinal elongation and/or compression of the guide post. Furthermore, the orientation of the measuring device relative to the tool may be defined mechanically and/or may be determined by a calibration step to be performed. By aligning the detected deformation direction to the coordinate system of the tool, the base of the guide post can be accurately aligned to its socket.

Embodiments of a system for measuring misalignment of tools in a press apparatus according to the invention will be explained in more detail below with reference to the accompanying drawings:

drawings

Fig. 1 shows a longitudinal section through a pressing apparatus comprising a tool, in particular a first part and a second part, which can be moved in a guided manner relative to each other by means of a guide device;

fig. 2 is a perspective view of a longitudinal section of a sensor according to a first embodiment of the present invention.

Fig. 3 is a perspective view of a longitudinal section of a sensor according to a second embodiment of the invention.

Figure 4a is a schematic view of a guide post with sensor according to a third embodiment of the invention.

Fig. 4b is a schematic view of the guide post with sensor according to fig. 4a in a deflected position.

Detailed Description

Fig. 1 shows a die-set structure of a press apparatus 1, which includes a tool 2. Depending on the complexity of the tool 2, the tool 2 comprises a plurality of plates which are put together and which are composed of at least a first part 3 or first half-mould (mold half) and a second part 4 or second half-mould (half mould), in particular a blanking or stamping mould, or a die. In fig. 1, the die set structure includes a female die indicated by 8 and a die guide plate indicated by 9. The first part 3 and the second part 4 of the tool 2 can be moved in a guided manner relative to each other by means of the guide means from the closed position to the open position and vice versa. Generally, when high guiding accuracy is required, guiding devices are used in tool or injection mold construction and in mechanical devices and equipment structures.

In the tool 2, the first part 3, which can carry the guide post 10, can be separated from the second part 4, the second part 4 being provided with a corresponding guide, in particular a guide sleeve 12 for accommodating the guide post 10, in which guide sleeve 12 the guide post 10 is guided, for example by means of ball bearings in a housing.

If a modular structure is used for the moulding operation, a mould may be attached on the separate surfaces of the first part 3 and/or the second part 4, which mould is filled, in particular in a horizontal direction, with the material to be formed, such as a casting material that is pressed into the mould, in the closed position of the tool 2. After opening the mould, a so-called preform (preform) can be removed from the mould.

In addition, the die set structure can be used for blanking operation and/or stamping operation.

By providing the tool 2 in the pressing device 1, the parallelism of the surface pair and the support surface must be carefully maintained. Fig. 1 shows a tool 2, which further comprises a die (die)5, in particular a die tool or punch, guided in a die guide plate 9. As shown in this figure, deviations of the plates 3, 4 from the congruent (congruency), of the clearance of the guidance of the tool 2 or of the angle of the support of the guide means may result in an inclined die axis 6. Further, if the guiding means, in particular the guide posts 10, are deflected and/or deviated with respect to the squareness, further deviations and misalignments of the superposition of the first portion 3 and the second portion 4 with respect to each other may occur.

According to the present invention, a measuring device for measuring misalignment of a standard such as a guide post 10 is provided. Thus, a longitudinal bore 14 is provided extending from one end (e.g. the free end) of the guide post 10 and coaxial with the guide post axis 16, wherein the diameter of the longitudinal bore 14 is smaller than the diameter of the guide post 10. Inserted into the longitudinal bore 14 is a measuring device (not shown), as described below.

Fig. 2 shows a perspective view of a longitudinal section through a measuring device 20 according to a first embodiment of the invention. The measurement device 20 comprises a cylindrical structure 22 to which a surface sensing element in the form of a strain gauge 24 is attached, thereby forming a strain gauge sensor. The measuring device 20 is configured to be inserted into the longitudinal bore 14 of the guide post 10 and fixedly mounted to an end region of the guide post 10 by means of a holding element. Thus, an annular element 26 may be provided at the end region of the cylindrical structure 22, which annular element 26 abuts the end face 11 of the guide post 10 when the cylindrical structure 22 is pushed completely into the longitudinal bore 14 and may be fixedly mounted in place by means of a press fit or the like.

At least one strain gauge 24 is provided at the circumference of the cylindrical structure 22. Preferably, two strain gauges 24 are attached in pairs to opposite sides of the cylindrical structure 22, so that both can detect compression and tension depending on the deflection direction of the guide post 10.

Fig. 3 shows a measuring device 20 according to a second embodiment of the invention, in which elements similar to those in the first embodiment are characterized equivalently. The measurement device 20 is configured as a capacitive sensor 30 comprising a first cylinder 32 and a second cylinder 34, wherein a first surface of the first cylinder 32 provides a first capacitive plate 36, a second surface of the second cylinder 34 provides a second capacitive plate 38, the first capacitive plate 36 and the second capacitive plate 38 being separated from each other by a distance d. If the guide post 10 (with the capacitive sensor 30 embedded in the longitudinal bore 14 in any suitable manner) is deformed or deflected, the first capacitive plate 36 and/or the second capacitive plate 38 will undergo translation and/or rotation, which will affect the distance d and thus directly the determined capacitance value of the capacitive sensor 30.

Fig. 4a and 4b show a measuring device 20 according to a third embodiment of the invention. Fig. 4a and 4b schematically show the guide post 10 with the fiber optic sensor 40 embedded in the longitudinal bore 14 coaxially with the guide post axis 16. The optical sensor 40 is configured as a fiber optic sensor, in particular an interferometric sensor, comprising a processing unit 42 comprising, in particular, (inter alia) an interferometer such as a fabry-perot interferometer, a converter converting an optical signal into an electrical signal, and a processor. For example, light from a low coherence light source (not shown) is split into a measurement fiber 44 and a reference fiber 46 disposed inside the measurement device 20. The measuring fiber 44 is connected to the measuring device 20 such that the measuring fiber 44 is elongated when bent. Fig. 4a shows the guide post 10 in a straight (straight) position. Figure 4b shows the guide post 10 with a deflection that can be detected by the fiber optic sensor 40.

While the present disclosure has been described with reference to particular means, materials and embodiments, the essential features of the disclosure can be readily ascertained by one skilled in the art from the foregoing description, while numerous changes and modifications may be made to adapt to various usages and features as set forth in the following appended claims.