Machine for measuring the geometric characteristics of a hardness indenter
An automated machine and method using interferometric techniques allow for efficient and rapid measurement of Rockwell and Vickers hardness indenter geometry by aligning and analyzing interference figures, eliminating the need for operator presence during the measurement process.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- LTF SPA
- Filing Date
- 2024-12-20
- Publication Date
- 2026-06-18
Smart Images
Figure IB2024063021_18062026_PF_FP_ABST
Abstract
Description
DESCRIPTION"MACHINE FOR MEASURING THE GEOMETRIC CHARACTERISTICS OF A HARDNESS INDENTER"
[0001] The present invention is in the technical field of machines for measuring the geometric characteristics of hardness indenters to be used in hardnes s tests ; in particular, the present invention relates to an automated machine for measuring the geometric characteristics of a hardness indenter of the Rockwell or Vickers type .
[0002] It is known to a person skilled in the art that the Rockwell hardness test is regulated by the EN ISO 6508 standard, with particular reference to Part 3 (EN ISO 6508-3 ) with regards to the calibration of a Rockwell hardness indenter .
[0003] The Rockwell-type hardness indenter is cone-shaped with a spherical tip made of diamond . In order to avoid abrupt discontinuities , the lateral surface of the cone and the surface of the spherical tip are tangentially connected therebetween in a uniform manner . The cone has an angle of 120 ° , and the axis of the cone defines a hardness indenter axis . The angle of the cone is measured by sectioning the cone using a hardness indenter cross- sectional plane containing the hardness indenter axis . Furthermore, the radius of the spherical tip is 0 . 2 mm .
[0004] It is clear that measuring the geometriccharacteristics of a Rockwell hardness indenter implies determining the angle of the cone and the radius of the spherical tip .
[0005] Conversely, the Vickers hardness test is regulated by the EN ISO 6507 standard, with particular reference to Part 3 (EN ISO 6507-3 ) with regards to the calibration of a Vickers hardness indenter .
[0006] The Vickers hardness indenter is pyramid-shaped with a square base and therefore takes the form of four lateral faces which, with respect to the apex of the pyramid, are paired opposite therebetween . The pyramid is made of diamond and the axis connecting the center of the square base to the apex of the pyramid defines a hardness indenter axis . The lateral faces that are opposing therebetween with respect to the apex of the pyramid form an angle of 136 ° . Furthermore, according to the geometric definition of a square, each of the four corners of the square base has an amplitude of 90 ° with a tolerance of ± 0 . 2 ° .
[0007] Measuring the geometric characteristics of a Vickers hardness indenter implies determining both the angle between the lateral faces that are opposing with respect to the apex of the pyramid and the amplitude of the corners of the square base .
[0008] According to the prior art , measurement of thegeometry of the hardness indenter is possible using"contact" or "optical" machines .
[0009] For example, an option for measuring the radius of the spherical tip of a Rockwell hardness indenter involves the use of a "contact"-type machine comprising a pneumostatic table and a contact probe to be arranged upon the spherical tip .
[0010] On the other hand, "optical" machines may be profile projectors or interferometric machines .
[0011] In particular, interferometric machines make use of interferometry, a measurement method based upon interference between waves , such as two light waves . Such interferometric machines are configured as applications of the Michelson interferometer, which exploits the waved nature of light . Essentially, with the Michelson interferometer, a beam of light strikes a half-silvered (or semi-reflective ) mirror which divides the beam of light into a reflected beam and a transmitted beam that passes through the half-silvered mirror .
[0012] The reflected beam strikes a sample (e . g . , the hardness indenter) which in turn reflects the reflected beam toward a detector (e . g . , camera) . On the other hand, the transmitted beam strikes a reference mirror which reflects it towards the detector . At the detector when the two beams are recombined ( reflected and transmitted)— an interference figure is obtained : if the waves are in phase they are added ( constructive interference ) ; otherwise, if the waves are out of phase they are subtracted (destructive interference ) . Within the interference figure generated by the recombination of the two beams , interference fringes (also known simply as fringes ) are observed which are formed by light bands alternating with dark bands . Finally, from the interference figure it is possible to obtain a light intensity profile .
[0013] The use of interferometric machines to measure the geometric characteristics of hardness indenters is for example described in the following publications wherein the content thereof is well known to a person skilled in the art :
[0014] - Affri R, Desogus S, Germak AL, Mazzoleni F, Perteghella D . Optical measuring system for hardness indenters . InProc . XVI IMEKO World Congress , Vienna 2000 Sep 25 (pp . 295-299 ) ;
[0015] - Affri R, Perteghella D, Barbato G, Desogus S, Germak AL, Origlia C . Metrological characterization of optical measuring system for hardness indenters . VDI BERICHTE . 2002 ; 1685 : 43-50 .
[0016] Disadvantageously, machines for measuring the geometric characteristics of hardness indenters — be they"contact" or "optical" — require the active presence of an operator not only during the machine setting step, but also during the hardness indenter measurement step .
[0017] The object of the present invention is to propose a machine, a method for measuring the geometric characteristics of a hardness indenter, a method for measuring the radius of a spherical tip of a Rockwell hardness indenter, and a method for measuring the angles of a square base of a Vickers hardness indenter that are capable of at least partially obviating the drawbacks mentioned above .
[0018] In particular, the object of the present invention is to propose an automated machine and methods that do not require the presence of an operator, with the exception of the step of inserting / setting up the hardness indenter on said machine .
[0019] Said object is achieved using a machine according to claim 1 , using a method for measuring the geometric characteristics of a hardness indenter according to claim 10 , using a method for measuring the radius of a spherical tip of a Rockwell hardness indenter according to claim 12 , and using a method for verifying that a Vickers-type hardness indenter comprises a square base with right angles according to claim 13 . The dependent claims describe preferred embodiments of the invention .
[0020] The features and advantages of the machine and of the method according to the invention shall be made readily apparent from the following description of preferred exemplary embodiments thereof , provided purely by way of non-limiting example , with reference to the accompanying figures , wherein :
[0021] - Figure 1 is a front view of a machine for measuring the geometric characteristics of a hardness indenter according to the present invention;
[0022] - Figure 2 is a perspective view of a hardness indenter movement apparatus ;
[0023] - Figure 2a is a perspective view in separate components of the hardness indenter movement apparatus of Figure 2 ;
[0024] - Figure 3 is a perspective view in separate components of an interferometric objective support apparatus ;
[0025] - Figure 4 is an example of an interference figure of a spherical tip of a Rockwell-type hardness indenter;
[0026] - Figure 4a is a further example of an interference figure of a spherical tip of a Rockwell hardness indenter;
[0027] - Figure 4b is an example of an interference figure of a lateral surface of a Rockwell hardness indenter, when said lateral surface is arranged tangentially to ahorizontal reference plane ;
[0028] - Figure 5 shows a luminous intensity profile and a normalized luminous intensity profile associated with the interference figure of Figure 4a;
[0029] - Figure 5a shows a luminous intensity profile and a normalized luminous intensity profile associated with the interference figure of Figure 4b;
[0030] - Figures 6-6a show, respectively, the reconstruction of the spherical tip profile and the lateral surface of a Rockwell hardnes s indenter ;
[0031] - Figure 7 is an example of an interference figure of a lateral face of a Vickers hardness indenter .
[0032] In the following description, elements common to the various embodiments represented in the drawings are indicated with the same reference numerals .
[0033] In said drawings , the reference numeral 1 is used to indicate, in the entirety thereof , a machine according to the invention .
[0034] The machine 1 for measuring the geometric characteristics of a Rockwell or Vickers type hardness indenter 2 comprises : a hardness indenter movement apparatus 3 , a microscope 4 , an interferometric obj ective support apparatus 5 , a camera 6, and a control unit .
[0035] The machine 1 is preferably automated, i . e . , capable of determining the geometric characteristics of thehardness indenter 2 without the direct intervention of an operator .
[0036] The microscope 4 is preferably an optical microscope and is provided with at least one interferometric objective 40 . Such interferometric objective 40 exploits interferometry in order to obtain a plurality of interference figures . In such case, the interferometric objective 40 comprises interferometric lenses .
[0037] The interferometric objective support apparatus 5 supports the microscope 4 . Furthermore, such interferometric objective support apparatus 5 also allows for movement of the microscope 4 .
[0038] The camera 6 is configured to detect the plurality of interference figures .
[0039] The camera 6 is preferably equipped with an observation screen (or plane ) whereupon the interference figures are observed . In particular, such observation screen is parallel to a horizontal reference plane 0. For the purposes of the present discussion, the terms "horizontal" , "vertical" , and the relative derivatives thereof are intended to refer to the machine 1 under conditions of use .
[0040] It should be noted that such horizontal reference plane 0 is arranged horizontally and the tip of the hardness indenter 2 lies upon said horizontal referenceplane 0.
[0041] The control unit is configured to examine the plurality of interference figures , obtain a light intensity profile from each interference figure of the plurality of interference figures , and calculate the geometric characteristics of the hardness indenter 2 .
[0042] It is well known to a person skilled in the art that the "light intensity profile" is a graph showing the light intensity of the fringes of the interference figure .
[0043] The hardness indenter movement apparatus 3 comprises a first actuator 311 , a first angular position transducer 312 and a hardness indenter housing 313 suitable for accommodating the hardness indenter 2 to be measured .
[0044] The hardness indenter housing 313 is rotatable about a rotation axis S by means of the first actuator 311 .
[0045] The first angular position transducer 312 measures the rotation of the hardness indenter housing 313 . Therefore, by measuring the rotation of the hardness indenter housing 313 , the sexagesimal degrees of rotation of said hardness indenter 2 are obtained .
[0046] In particular, when the hardness indenter 2 is inserted into the hardness indenter housing 313 , the rotation axis S is suitable for coinciding with a hardness indenter axis P . In the case of a Rockwellhardness indenter, the hardness indenter axis P is the axis of the cone ; in the case of a Vickers hardness indenter, however, the hardness indenter axis P is that axis that connects the center of the square base to the apex of the pyramid .
[0047] For example, the first actuator 311 is an electric motor and preferably a stepper motor .
[0048] The first angular position transducer 312 is an encoder and preferably an incremental encoder .
[0049] The hardness indenter movement apparatus 3 also comprises a second actuator 321 , a second angular position transducer 322 , and an arm 323 operatively connected to the hardness indenter housing 313 .
[0050] Said arm 323 is rotatable about a rolling axis R in such a way that the rotation of the arm 323 is transferable to the hardness indenter housing 313 .
[0051] The second angular position transducer 322 measures the rotation of the arm 323 about the rolling axis R .
[0052] Preferably, the rolling axis R is orthogonal to the rotation axis S .
[0053] In particular, the rotation of the arm 323 also results in rotation of the hardness indenter housing 313 (and therefore of the hardness indenter 2 housed therein) about the rolling axis R; therefore, from the measurement of the rotation of the arm 323 it is also possible toobtain the measurement of the rotation of the hardness indenter housing 313 about the rolling axis R.
[0054] Preferably, the arm 323 is "C"-shaped .
[0055] For example, the second angular position transducer 322 is an encoder and preferably an absolute encoder .
[0056] The machine 1 also comprises a first positioning actuator 11 , a second positioning actuator 12 , and a third positioning actuator 13 .
[0057] The first positioning actuator 11 controls the movement of the hardness indenter movement apparatus 3 or the interferometric objective support apparatus 5 along a first horizontal positioning axis X .
[0058] The second positioning actuator 12 controls the movement of the hardness indenter movement apparatus 3 or the interferometric objective support apparatus 5 along a second horizontal positioning axis Y .
[0059] The third positioning actuator 13 controls the movement of the hardness indenter movement apparatus 3 or the movement of the interferometric objective support apparatus 5 along a vertical positioning axis Z .
[0060] In an embodiment according to the accompanying Figure 3 , the interferometric objective support apparatus 5 comprises the third positioning actuator 13 .
[0061] Such third positioning actuator 13 moves the interferometric objective 40 to achieve focusing of thehardness indenter 2 and thereby produce a first interference figure .
[0062] In such case, the hardness indenter 2 is provided with a tip (a spherical tip in the case of a Rockwell hardness indenter or an apex of the pyramid in the case of a Vickers hardness indenter) and, by moving the interferometric objective 40 , it is possible to focus on such tip . In other words , the interferometric ob jective 40 focuses on the tip of the hardness indenter 2 in such a way as to arrange it at the optical center of the microscope 4 .
[0063] Once the tip of the hardness indenter 2 has been arranged at the optical center, the interferometric objective 40 generates a first interference figure that is detected by the camera 6 .
[0064] For example, in the case of a Rockwell hardness indenter, the first interference figure shows concentric rings of an approximately circular shape, similar to "Newton rings" (Figure 4-4a) .
[0065] In accordance with the embodiment according to the accompanying figure 2a, the hardness indenter movement apparatus 3 comprises the first positioning actuator 11 and the second positioning actuator 12 .
[0066] Such first 11 and second positioning actuators 12 move the hardness indenter housing 313 along the first Xand second horizontal positioning axes Y for aligning the hardness indenter housing 313 with the interferometric objective 40 .
[0067] With the hardness indenter 2 inserted into the respective housing 313 , said hardness indenter 2 is aligned with the interferometric objective 40 . In particular, the rotation axis S is collinear to the optical axis of the interferometric objective 40 and it is thus possible to obtain a plurality of interference figures .
[0068] According to the embodiment shown in Figure 2a, the hardness indenter movement apparatus 3 comprises friction reduction means 33 , for example a pair of bearings, which allow the arm 323 to rotate about the rolling axis R .
[0069] Such hardness indenter movement apparatus 3 further comprises misalignment correction means 34 , for example a pair of spheres , which allow any deviations of the rolling axis R to be corrected such that the rolling axis R remains orthogonal to a hardness indenter cross- sectional plane C containing the rotation axis S .
[0070] According to the embodiment shown in Figure 2a, the hardness indenter movement apparatus 3 comprises a worm gear 35 and a gear wheel 36 .
[0071] The gear wheel 36 is integrally coupled to the hardness indenter housing 313 .
[0072] The worm gear 35 is operatively connected to the first actuator 311 .
[0073] The worm gear 35 and the gear wheel 36 are engaged with each other . In particular, the gear wheel 36 engages with the worm gear 35 .
[0074] The gear wheel 36 is preferably coaxial to the hardness indenter housing 313 .
[0075] According to the embodiment shown in the accompanying Figures 2 and 2a, the machine 1 also comprises a first movement table 111 translatable along the first horizontal positioning axis X and a second movement table 122 translatable along the second horizontal positioning axis Y .
[0076] The first positioning actuator 11 is operatively connected to the first movement table 111 , and the second positioning actuator 12 is operatively connected to the second movement table 122 .
[0077] Preferably, the first 111 and the second movement table 122 translate along respective straight guides 113 , 123 .
[0078] According to the embodiment of Figure 3 , the interferometric objective support apparatus 5 comprises an objective support element 50 which is translatable along the vertical positioning axis Z .
[0079] Such objective support element 50 is operativelyconnected to the third positioning actuator 13 by means of motion return means 131 , for example a belt .
[0080] According to the embodiment shown in Figure 3 , the interferometric objective support apparatus 5 comprises a third movement table 53 rigidly connected to the objective support element 50 .
[0081] For example, the third movement table 53 is translatable upon straight tracks 153 .
[0082] Preferably, the objective support element 50 has a seat 51 where the at least one interferometric ob jective 40 is housed .
[0083] According to the present invention, also proposed is a method for measuring the geometric characteristics of a Rockwell or Vickers type hardness indenter 2 . Such method for measuring the geometric characteristics of the hardness indenter comprises the following steps . It should be noted that the steps of the method are not necessarily in chronological order of execution .
[0084] The method is completely automated insofar as the machine 1 is automated, i . e . , capable of determining the geometric characteristics of the hardnes s indenter 2 without the direct intervention of the operator .
[0085] i ) -ii ) The machine 1 and a hardness indenter 2 , of the Rockwell or Vickers type, extending along a hardness indenter axis P , are provided .
[0086] iii ) The hardness indenter 2 is arranged within the hardness indenter housing 313 .
[0087] iv) The hardness indenter 2 is aligned with the interferometric objective 40 . Such alignment is achieved by means of the first 11 and the second positioning actuators 12 which, by moving the hardness indenter housing 313 , make the rotation axis S collinear to the optical axis of the interferometric objective 40 .
[0088] v) The interferometric objective 40 is arranged in such a way as to focus on the hardness indenter 2 . In other words , the interferometric objective 40 focuses on the tip of the hardness indenter 2 . In such case the focusing is achieved by virtue of the third positioning actuator 13 which moves the interferometric objective 40 along the vertical positioning axis Z so as to arrange the tip of the hardness indenter 2 at the optical center of the microscope 4 .
[0089] vi ) A first interference figure of the tip of the hardness indenter 2 is generated and said first interference figure is detected using the camera 6 .
[0090] In the case of a Rockwell hardness indenter, the first interference figure shows concentric rings of an approximately circular shape, similar to "Newton rings" . On the other hand, in the case of a Vickers hardness indenter, the first interference figure is substantiallypunct if orm .
[0091] vii ) A first rotation of the arm 323 is performed in order to transfer such first rotation to the hardness indenter 2 . The hardness indenter axis P remains lying within a hardness indenter cross-sectional plane C and the hardness indenter 2 rotates until it is arranged tangent to a horizontal reference plane 0.
[0092] The first rotation of the arm 323 , and thus the first rotation of the hardness indenter 2 , is measured about the rolling axis R using the second angular position transducer 322 .
[0093] viii ) A second interference figure of a lateral surface (Figure 4b) or of a first lateral face (Figure 7 ) of the hardness indenter 2 is generated, and said second interference figure is detected using the camera 6 .
[0094] With the Rockwell hardness indenter, it being cone- shaped, it is preferable to speak of a "lateral surface" of the cone, which is arranged tangentially to the horizontal reference plane 0 in order to obtain the second interference figure .
[0095] On the other hand, the Vickers hardness indenter is pyramid-shaped with a square base and therefore takes the form of four lateral faces which, with respect to the apex of the pyramid, are paired opposite therebetween . Therefore, in the case of a Vickers hardness indenter, itis preferable to speak of a "first ( second, third, or fourth) lateral face" which is arranged tangentially to the horizontal reference plane 0 to obtain the corresponding interference figure . In particular, the first and second lateral faces are opposite therebetween with respect to the apex of the pyramid . The third and fourth lateral faces of the Vickers hardness indenter are orthogonal to the first and second lateral faces and are opposite therebetween with respect to the apex of the pyramid .
[0096] ix) A second rotation of the arm 323 is performed in the opposite direction from the first rotation until the hardness indenter 2 is arranged tangent to the horizontal reference plane 0. The hardness indenter axis P remains lying within the hardness indenter cross-sectional plane C .
[0097] The second rotation of the arm 323 , and thus the second rotation of the hardness indenter 2 , about the rolling axis R is measured using the second angular position transducer 322 .
[0098] x) A third interference figure of the lateral surface or of a second lateral face of the hardness indenter 2 is generated, and said third interference figure is detected using the camera 6 .
[0099] As already explained, the Rockwell hardness indenteris cone-shaped, and the lateral surface that is arranged tangentially to the horizontal reference plane 0 to obtain the third interference figure is therefore opposite to that used to obtain the second interference figure .
[0100] On the other hand, in the case of a Vickers hardness indenter, the second lateral face is opposite (with respect to the apex of the pyramid) the first lateral face . Such second lateral face is arranged tangentially to the horizontal reference plane 0 to obtain the third interference figure .
[0101] In order to calculate the angle of the cone ( 120 ° in the case of a Rockwell hardness indenter) or the angle between the lateral faces that are opposing with respect to the apex of the pyramid ( 136 ° in the case of a Vickers hardnes s indenter) , the first and second rotations of the arm 323 about the rolling axis R, measured using the second angular position transducer 322 , are algebraically added .
[0102] xi ) The geometry of the hardness indenter 2 is reconstructed by means of the control unit , which obtains a light intensity profile associated with each of the first , second, and third interference figures . By examining each light intensity profile, the control unit determines the geometry of the hardness indenter .
[0103] The reconstruction of the geometry of the hardness indenter 2 therefore takes place by means of examining the first , second, and third interference figures , wherefrom the control unit obtains corresponding light intensity profiles which allow the geometry of the hardness indenter 2 , within the hardness indenter cross- sectional plane C, to be determined (Figure 6-6a) . With the geometry of the hardness indenter known it is then possible to calculate the angle of the cone ( 120 ° in the case of a Rockwell hardness indenter) or the angle between the lateral faces that are opposing with respect to the apex of the pyramid ( 136 ° in the case of a Vickers hardness indenter) .
[0104] Specifically, the control unit obtains a light intensity profile for each ( first , second, third, etc . ) interference figure . The control unit subsequently obtains a normalized light intensity profile from each intensity profile ( see Figures 5 and 5a ) . Finally, the profile ( shape ) of the hardness indenter is reconstructed using the following formula :where y = profile function of the hardness indenter; f = normalized light intensity function;X wavelength of the light used by the interferometricobjective to illuminate the hardness indenter; n_f = number of interference fringes considered.
[0105] In one embodiment of the method for measuring the geometric characteristics of the hardness indenter, such method also comprises the step wherein the hardness indenter 2 is rotated about the hardness indenter axis P in order to then repeat steps iv-xi . Accordingly, once each rotation about the hardness indenter axis P has been completed, the execution of steps iv-xi is repeated.
[0106] For example, in the case of a Rockwell hardness indenter, rotations of 22.5° are made until a rotation about the hardness indenter axis P of 157.5° is reached. In particular, the eight rotations are: 0°, 22.5°, 45°, 67.5°, 90°, 112.5°, 135°, and 157.5°.
[0107] On the other hand, in the case of a Vickers hardness indenter, four rotations of a multiple of 90° are made about the hardness indenter axis P. In particular, the four rotations are: 0°, 90°, 180°, and 270°; in this way it is possible to observe all four lateral faces of the Vickers hardness indenter using the interferometric objective 40.
[0108] According to the present invention, also proposed is a method for measuring the radius of a spherical tip of a Rockwell-type hardness indenter 2. Such method comprises the following steps.
[0109] The machine 1 and the Rockwell type hardness indenter 2 are arranged extending along a hardness indenter axis P .
[0110] iii ) The hardness indenter 2 is arranged within the hardness indenter housing 313 .
[0111] iv) The hardness indenter 2 is aligned with the interferometric objective 40 . Such alignment is achieved by means of the first 11 and the second positioning actuators 12 , which, by moving the hardness indenter housing 313 , make the rotation axis S collinear to the optical axis of the interferometric objective 40 .
[0112] v) The interferometric objective 40 is arranged so as to focus on the hardness indenter 2 , in particular the tip of the hardness indenter 2 . In such case the focusing is achieved by virtue of the third positioning actuator 13 , which moves the interferometric objective 40 along the vertical positioning axis Z so as to arrange the tip of the hardness indenter 2 at the optical center of the microscope 4 .
[0113] vi ) A first interference figure of the tip of the hardness indenter 2 is generated, and said first interference figure is detected using the camera 6 .
[0114] In the case of a Rockwell hardness indenter, the first interference figure shows concentric rings of an approximately circular shape, similar to "Newtonrings" .
[0115] vii ) A plurality of progressive rotations of the arm 323 is made both clockwise and in the opposite direction . The hardness indenter axis P lies within a hardness indenter cross-sectional plane C, and the spherical tip of the hardness indenter 2 always faces the interferometric objective 40 .
[0116] Preferably, each rotation of said plurality of progressive rotations of the arm 323 has an amplitude of 5 ° .
[0117] In particular, such progressive rotations of the arm 323 are transferred to the hardness indenter 2 and are measured by means of the second angular position transducer 322 .
[0118] Locally, considering that such rotations are 5 ° about the rolling axis R, the interferometric objective 40 is always found to be facing a spherical surface of the tip of the hardness indenter 2 .
[0119] viii ) An interference figure is generated at each rotation of said plurality of progressive rotations , and said interference figure is detected using the camera 6 .
[0120] ix) The geometry of the tip of the hardness indenter 2 is reconstructed by means of examining each interference figure generated at each rotation . Thecontrol unit obtains a light intensity profile associated with each interference figure so as to determine the geometry of the tip of the hardness indenter 2 . In particular, from each interference figure the control unit obtains corresponding profiles of light intensity which make it possible to determine the geometry of the tip of the hardness indenter 2 .
[0121] x) The radius of the tip of the hardness indenter 2 is calculated once the shape of the spherical tip within the hardness indenter cross-sectional plane C is reconstructed .
[0122] xi ) The hardness indenter 2 is rotated about the hardness indenter axis P by a predefined angle and the steps iv-x are repeated so as to reconstruct the shape of the tip within a further hardness indenter cross-sectional plane .
[0123] Each time the hardness indenter 2 is rotated about the hardnes s indenter axis P by a predefined angle, an additional hardness indenter cross-sectional plane is identified that is orthogonal to the rolling axis R and contains the rotation axis S . The reconstruction of the geometry of the spherical tip of the hardness indenter 2 occurs within the further hardness indenter cross- sectional plane .
[0124] For the purposes of such discussion, it isspecified that the terms "reconstruct the shape" and"reconstruct the geometry" are substantially equivalent , unless otherwise specified .
[0125] The present invention also pertains to a method for verifying that the square base of the Vickers-type hardness indenter 2 comprises right angles . The method comprises the following steps .
[0126] i ) -ii ) The machine 1 and the Vickers type hardness indenter 2 , which extends along the hardness indenter axis P , are both provided .
[0127] iii ) The hardness indenter 2 is arranged within the hardness indenter housing 313 .
[0128] iv) The hardness indenter 2 is aligned with the interferometric objective 40 .
[0129] v) A first rotation of the arm 323 is performed so as to arrange a first lateral face of the hardness indenter 2 parallel to a horizontal reference plane 0. The hardness indenter axis P remains lying within a hardness indenter cross-sectional plane C .
[0130] The first rotation of the arm 323 about the rolling axis R is preferably substantially 90 ° .
[0131] It will appear obvious to a person skilled in the art that the first ( second, third, or fourth) lateral face is in focus so that the interferometric objective 40 may generate the interference fringes .
[0132] vi ) A first interference figure of the first lateral face of the hardness indenter 2 is generated, and such first interference figure is detected using the camera 6 .
[0133] vii ) Steps v-vi are repeated for each of the four lateral faces of the Vickers hardness indenter 2 so as to generate four interference figures associated respectively with the four lateral faces of the hardness indenter 2 . It should be noted that , in order to perform the steps v-vi for each of the four lateral faces , it may be necessary to rotate the hardness indenter 2 about the hardness indenter axis P by a multiple of 90 ° .
[0134] It is recalled that the Vickers-type hardness indenter 2 is pyramid-shaped with a square base and therefore comprises four lateral faces , where the first and second lateral faces are opposite therebetween with respect to the apex of the pyramid . The third and fourth lateral faces of the Vickers hardness indenter are orthogonal to the first and second lateral faces and are opposite therebetween with respect to the apex of the pyramid .
[0135] viii ) The angles of the square base are calculated by means of examining the four interference figures .
[0136] In particular, within each of the fourinterference figures the interference fringes are substantially parallel to a respective side of the square base of the Vickers hardness indenter . The interference fringes produced by observing the first and second lateral faces are therefore substantially parallel therebetween . On the other hand, the interference fringes produced by observing the third and fourth lateral faces are substantially parallel therebetween and orthogonal to the fringes of the first and second lateral faces .
[0137] Thus , by calculating the angles between the interference fringes , it is possible to measure the angles of the square base and verify whether or not they are straight .
[0138] Specifically, in order to generate the four interference figures , the following procedure is performed :
[0139] - a second lateral face of the hardness indenter 2 is arranged parallel to the horizontal reference plane 0 so that the hardness indenter axis P remains lying within a second hardness indenter cross- sectional plane . A second interference figure of the second lateral face of the hardness indenter is generated, and said second interference figure is detected using the camera 6 .
[0140] - A third lateral face of the hardness indenteris arranged parallel to the horizontal reference plane 0 so that the hardness indenter axis P remains lying within a third hardness indenter cross-sectional plane . A third interference figure of the third lateral face of the hardness indenter is generated, and said third interference figure is detected using the camera 6 .
[0141] - Finally, a fourth lateral face of the hardness indenter is arranged parallel to the horizontal reference plane 0 so that the hardness indenter axis P remains lying within a fourth hardness indenter cross- sectional plane . A fourth interference figure of the fourth lateral face of the hardness indenter is generated, and said fourth interference figure is detected using the camera 6 .
[0142] The calculation of the angles of the square base is obtained by measuring the angle between the interference fringes obtained from the observation of adjacent lateral faces . Thus , in order to calculate the amplitudes of the angles of the square base, the interference fringes of the first interference figure are subsequently compared with those of the third and fourth interference figures . Similarly, the interference fringes of the second interference figure are compared with those of the third and fourth interference figures .
[0143] In particular, all of the analysis andcalculation operations of the angles of the base of the hardness indenter are performed by the control unit .
[0144] Innovatively, the machine and the methods of the present invention fully achieve the intended object thereof .
[0145] Advantageously, the machine of the present invention allows for the geometric characteristics of the hardness indenter to be measured more rapidly with respect to the solutions currently contemplated by the state of the art .
[0146] Advantageously, moreover, the method for measuring the geometric characteristics of a Rockwell- or Vickers-type hardness indenter according to the present invention is faster and quicker than other currently known measurement methodologies .
[0147] A further advantage of the machine of the present invention is that it is completely automated . The operator is only in fact responsible for inserting the hardness indenter into the machine and removing it from the machine once the geometric characteristics thereof have been fully determined . The hardness indenter measurements are therefore performed by the machine completely independently only under the supervision of the operator, but without the direct involvement thereof .
[0148] According to an advantageous aspect , the methodfor measuring the geometric characteristics of the hardness indenter is more economical than that contemplated by the state of the art insofar as the use of a completely automated machine allows the measurement process to be optimized, thereby saving on man-hours .
[0149] To the embodiment s of the machine and execution of the methods , a person skilled in the art , in order to meet specific requirements , may make changes or replace elements with other functionally equivalent ones . These variants are also contained within the scope of protection as defined by the following claims . Furthermore, each of the variants described as belonging to one possible embodiment may be obtained independently in the other described embodiments .
Claims
CLAIMS1. A machine (1) for measuring geometric features of an indenter (2) of the Rockwell or Vickers type, said machine (1) comprising:- an indenter movement apparatus (3) ;- a microscope (4) , preferably an optical microscope, provided with at least one interferometric objective (40) , said interferometric objective (40) utilizing interferometry to obtain a plurality of interference figures ;- an interferometric objective support apparatus (5) for supporting said microscope (4) ;- a camera (6) for detecting the plurality of interference figures;- a control unit configured to examine the plurality of interference figures, derive a light intensity profile from each interference figure of said plurality of interference figures, and calculate the geometric features of the indenter (2) , wherein the indenter movement apparatus (3) comprises a first actuator (311) , a first angular position transducer (312) , and an indenter housing (313) suitable for accommodating the indenter (2) to be measured, said indenter housing (313) being rotatable about a rotationaxis (S) by means of the first actuator (311) , the first angular position transducer (312) measuring the rotation of the indenter housing (313) , wherein the indenter movement apparatus (3) also comprises a second actuator (321) , a second angular position transducer (322) , and an arm (323) operatively connected to the indenter housing (313) , said arm (323) being rotatable about a roll axis (R) so that the rotation of the arm (323) is transferable to the indenter housing (313) , the second angular position transducer (322) measuring the rotation of the arm (323) about the roll axis (R) , wherein the machine (1) also comprises:(i) a first positioning actuator (11) for moving the indenter movement apparatus (3) or the interferometric objective support apparatus (5) along a first horizontal positioning axis (X) ; ii) a second positioning actuator (12) for moving the indenter movement apparatus (3) or the interferometric objective support apparatus (5) along a second horizontal positioning axis (Y) ; iii) a third positioning actuator (13) for moving the indenter movement apparatus (3) or the interferometric objective support apparatus (5) along a vertical positioning axis (Z) .
2. Machine according to the preceding claim, wherein the interferometric objective support apparatus (5) comprises the third positioning actuator (13) , said third positioning actuator (13) moving the interferometric objective (40) to achieve the focusing of the indenter (2) and produce a first interference figure.
3. Machine according to any one of the preceding claims, wherein the indenter movement apparatus (3) comprises the first positioning actuator (11) and the second positioning actuator (12) , said first (11) and second (12) positioning actuators moving the indenter housing (313) along the first (X) and second (Y) horizontal positioning axes to align the indenter housing (313) with the interferometric objective (40) .
4. Machine according to any one of the preceding claims, wherein the indenter movement apparatus (3) comprises friction reduction means (33) , for example a pair of bearings, which allow the rotation of the arm (323) about the roll axis (R) , said indenter movement apparatus (3) further comprising offset correction means (34) , for example a pair of balls, which allow correcting any deviations of the roll axis by ensuring that said roll axis (R) remains orthogonal to an indenter section plane (C) containing the rotation axis (S) .
5. Machine according to any one of the precedingclaims, wherein the indenter movement apparatus (3) comprises a worm screw (35) and a toothed wheel (36) , the toothed wheel (36) being integrally coupled to the indenter housing (313) , the worm screw (35) being operatively connected to the first actuator (311) , the worm screw (35) and the toothed wheel (36) engaging each other .
6. Machine according to any one of the preceding claims in combination with claim 3, further comprising a first movement table (111) translatable along the first horizontal positioning axis (X) and a second movement table (122) translatable along the second horizontal positioning axis (Y) , wherein the first positioning actuator (11) is operatively connected to said first movement table (111) and the second positioning actuator (12) is operatively connected to said second movement table (122) .
7. Machine according to any one of the preceding claims in combination with claim 2, wherein the interferometric objective support apparatus (5) comprises an objective support element (50) translatable along the vertical positioning axis (Z) , said objective support element (50) being operatively connected to the third positioning actuator (13) by motion transmission means (131) , for example a belt .
8. Machine according to the preceding claim, wherein the interferometric objective support apparatus (5) comprises a third movement table (53) rigidly connected to the objective support element (50) .
9. Machine according to claim 7 or 8, wherein the objective support element (50) has a seat (51) where to house the at least one interferometric objective (40) .
10. A method for measuring geometric features of an indenter (2) of the Rockwell or Vickers type, comprising the following steps :(i) providing a machine (1) according to any one of the preceding claims;(ii) providing an indenter (2) of the Rockwell or Vickers type, extending along an indenter axis (P) ;(iii) placing the indenter (2) in the indenter housing (313) ;(iv) aligning the indenter (2) with the interferometric objective (40) ;(v) arranging the interferometric objective (40) so as to focus the indenter (2) ; vi) generating a first interference figure of the tip of the indenter (2) and detecting said first interference figure with the camera (6) ; vii) performing a first rotation of the arm (323) so as to transfer such a first rotation to the indenter (2) ,the indenter axis (P) remaining lying in an indenter section plane (C) and the indenter (2) rotating until it is arranged tangent to a horizontal reference plane (0) ;(viii) generating a second interference figure of a side surface or of a first side face of the indenter (2) and detecting said second interference figure with the camera (6) ; ix) performing a second rotation of the arm (323) in the opposite direction with respect to the first rotation until the indenter (2) is arranged tangent to the horizontal reference plane (0) , the indenter axis (P) remaining lying in the indenter section plane (C) ; x) generating a third interference figure of the side surface or of a second side face of the indenter (2) and detecting said third interference figure with the camera (6) ; xi) reconstructing the geometry of the indenter (2) , the control unit derives a light intensity profile associated with each of the first, second and third interference figures, by examining each light intensity profile the control unit determines the geometry of the indenter.
11. Method according to the preceding claim, further comprising the step of rotating the indenter (2) about the indenter axis (P) and then repeating steps iv-xi .
12. A method for measuring the radius of a spherical tipof an indenter (2) of the Rockwell type, said method comprising the following steps:(i) providing a machine (1) according to any one of claims 1 to 9; ii) providing the indenter (2) of the Rockwell type extending along an indenter axis (P) ;(iii) placing the indenter (2) in the indenter housing (313) ;(iv) aligning the indenter (2) with the interferometric objective (40) ;(v) arranging the interferometric objective (40) so as to focus the indenter (2) , in particular the tip of the indenter (2) ; vi) generating a first interference figure of the tip of the indenter (2) and detecting said first interference figure with the camera (6) ; vii) performing a plurality of progressive rotations of the arm (323) both clockwise and in the opposite direction, the indenter axis (P) remaining lying in an indenter section plane (C) and the spherical tip of the indenter (2) facing the interferometric objective (40) ;(viii) generating an interference figure at each rotation of said plurality of progressive rotations and detecting said interference figure with the camera (6) ; ix) reconstructing the geometry of the tip of theindenter (2) by examining each interference figure generated at each rotation, the control unit deriving a light intensity profile associated with each interference figure, so as to determine the geometry of the tip of the indenter (2) ; x) calculating the radius of the tip of the indenter (2) once the shape of the spherical tip has been reconstructed on the indenter section plane (C) ; xi) rotating the indenter (2) about the indenter axis (P) by a predefined angle and repeating steps iv-x, so as to reconstruct the shape of the tip in a further indenter section plane.
13. A method for verifying that an indenter (2) of the Vickers type comprises a square base with right angles, said method comprising the following steps :(i) providing a machine (1) according to any one of claims 1 to 9; ii) providing the indenter (2) of the Vickers type extending along an indenter axis (P) ;(iii) placing the indenter (2) in the indenter housing (313) ;(iv) aligning the indenter (2) with the interferometric objective (40) ; v) performing a first rotation of the arm (323) so as to arrange a first side face of the indenter (2) parallel toa horizontal reference plane (0) , the indenter axis (P) remaining lying in an indenter section plane (C) ; vi) generating a first interference figure of the first side face of the indenter (2) and detecting said first interference figure with the camera (6) ; vii) repeating steps v-vi for each of the four side faces of the Vickers indenter (2) , so as to generate four interference figures associated with the four side faces of the indenter (2) , respectively; (viii) calculating the angles of the square base by examining the four interference figures.