EP4173752A1 - Bearbeitungsvorrichtung und -verfahren - Google Patents

Bearbeitungsvorrichtung und -verfahren Download PDF

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Publication number
EP4173752A1
EP4173752A1 EP22383033.2A EP22383033A EP4173752A1 EP 4173752 A1 EP4173752 A1 EP 4173752A1 EP 22383033 A EP22383033 A EP 22383033A EP 4173752 A1 EP4173752 A1 EP 4173752A1
Authority
EP
European Patent Office
Prior art keywords
machining
tool
inspection head
support
machining tool
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22383033.2A
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English (en)
French (fr)
Inventor
Jose Luis Lanzagorta Bengochea
Iratxe AIZPURUA MAESTRE
Paula RUIZ VAZQUEZ
David Barrenechea Azpeitia
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ideko S Coop
Original Assignee
Ideko S Coop
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ideko S Coop filed Critical Ideko S Coop
Publication of EP4173752A1 publication Critical patent/EP4173752A1/de
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/10—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation involving electrical means
    • B24B49/105—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation involving electrical means using eddy currents

Definitions

  • the object of the present invention relates to a machining device and method for machining parts, particularly applicable to the grinding of steel parts.
  • the machining device and method object of the present invention allow obtaining parts with mechanical properties adapted to the service parameters required for the part, minimizing machining errors, and therefore decreasing the number of parts that must be discarded and/or disposed of after machining due to the appearance of thermal damage comprising microstructural changes, burns, white layer, cracks, etc., on the part.
  • the machining device and method object of the present invention are applicable in the industry dedicated to the manufacture of high-precision metal parts.
  • a surface machining step is required for correcting the dimensions and the surface finish of the parts.
  • One of these machining operations is the grinding of parts.
  • a machine comprising a support configured for receiving a part to be machined and a rotary grinding wheel to apply grinding is used. Therefore, once the part to be ground is fixed on the support, a grinding wheel with an abrasive surface is applied to the surface of the part to be machined. The grinding wheel is rotated at a certain rotational speed and, in turn, the part to be machined can also be subjected to a rotational speed.
  • a technique known as "acid inspection” is often used for detecting grinding burn. This technique consists of the application of an acid on the surface of the machined part and subsequent surface examination. The technique allows “revealing” defects characteristic of the surface burn on the parts. This technique cannot be automated and depends on the subjectiveness and experience of the operator.
  • Another technique used for detecting grinding burn is surface analysis by means of eddy currents.
  • a variable magnetic field emitter usually using a "pencil” type probe
  • the passage of alternating current through the probe generates an alternating magnetic field which, in the vicinity of a conductive material, induces eddy currents in the material.
  • the presence of surface defects in the material causes a variation in the eddy current distribution in the material. This variation produces a signal in the eddy current equipment, in the probe itself, or in a receiving probe which in turn produces a signal in the equipment interpreted as a surface defect indicator.
  • metal part machining operations and more specifically grinding operations, constitute deeply experimental techniques that ultimately depend heavily on the degree of expertise of the operators handling the grinding machines. For this reason, it is difficult to predict the appearance of surface burn on machined parts, and it is therefore difficult to prevent the appearance of said burn, as well as to predict the number of parts that will end up being discarded as a result of the appearance of said surface burn.
  • the present invention relates to a machining device and method.
  • the machining device object of the present invention comprises a machining tool for grinding parts (for example, a grinding wheel), a support configured for receiving a part to be ground, and a control unit configured for controlling at least one operating parameter of the device.
  • a machining tool for grinding parts for example, a grinding wheel
  • a support configured for receiving a part to be ground
  • a control unit configured for controlling at least one operating parameter of the device.
  • the machining device object of the present invention comprises, in a novel manner, an inspection head with an eddy current sensor with at least one coil configured for producing eddy currents on the surface of the part during machining and for detecting a variation of the eddy current distribution obtained as a result of microstructural changes on the surface of the part.
  • the induction of eddy currents is controlled by the control unit of the device which will be in charge of causing the passage of an alternating current for inducing eddy currents on the surface of the part.
  • the inspection head is connected to the control unit of the device, with the control unit of the device being configured for acting on at least one operating parameter of the device in response to detecting a variation of the eddy current distribution greater than a predetermined threshold value.
  • the electronics for eddy current induction and detection and the electronics for changing the machining parameters of the device can be arranged together or independently.
  • the variation of the eddy current distribution exceeds the mentioned predetermined threshold value, it may be indicative of the beginning of the appearance of grinding burn in the part.
  • the device of the invention includes in one and the same device both a grinding machine and a burn detection device which allows said in-process inspection.
  • this detection allows the control unit of the machining device of the invention to act on at least one operating parameter of the machining device during the machining itself without having to stop the machine, in order to minimize and/or reverse the grinding burn effect that may be appearing.
  • said threshold value anticipates the appearance of burns in the part, modifying the parameters which change the operating conditions to prevent burn completely or to allow burn with values that do not affect the structural characteristics required for the use of the part. Therefore, said threshold value is considered a pre-burn safety factor which allows modifying the parameters to prevent said burn.
  • the inspection head comprises a sensor array (sensor with several coils) which allows covering a larger inspection area controlling a larger surface with a single sensor and reducing the inspection time.
  • a sensor array in one and the same assembly with several electronically controlled coils as a single unit. This is particularly applicable when machining is performed on a flat face of the part, given that the sensor array can cover a maximum area of the flat face of the part in order to detect possible irregularities indicative of a grinding burn.
  • the inspection head comprises a sensor array support end with a surface in correspondence with the geometry of the part.
  • This arrangement allows the sensor array to be able to adapt to the surface of the part, for example, to the curvature of the axis of the part, and to thereby cover points that may be inaccessible for inspection.
  • both machining and detection by means of the inspection head can also be applied on a curved (e.g., cylindrical) face instead of on a flat face of a part to be machined.
  • the machining device comprises control means for controlling the separation distance between the inspection head and the part. This is particularly useful given that the dimensions of the part (of its surface) gradually change during the machining operation.
  • control means for controlling the separation distance between the inspection head and the part may comprise a spring configured for ensuring a constant distance between the inspection head and the surface of the part.
  • the machining device may also comprise approaching means between the support for the part and the machining tool.
  • control unit of the device is configured for acting on at least one operating parameter of the device.
  • control unit is configured to completely stop the machining operation of the machining device in order to effect a change of parameters that cannot be performed during the process itself, such as the case of applying a diamond coating on the surface of the machining tool, in order to correct irregularities (e.g., flat faces on the surface of the tool or grinding wheel) which may negatively affect the part to be machined.
  • This change of process parameters could be carried out individually or together with the variation of at least one of the aforementioned parameters.
  • the approaching means for moving the inspection head closer to the part move in a guided manner on a machining guide corresponding to the machining guide of the machining device, for example, the guide of a grinding machine, such that the sensor is moved closer to the part in a manner perpendicular to the surface to be machined during machining inspection.
  • the part head guide itself is used, which ensures a micrometric positioning accuracy and a sensor-part parallelism tolerance of under a hundredth. In this way, both the geometric positioning and the adjustment of the distance of the head with the part, performed during startup, have a very high repeatability, favoring optimal operation of the head and measurement reliability.
  • said approaching means comprise positioning means which position the sensor in the plane perpendicular to the movement of the approaching means. They allow for greater precision during inspection.
  • the sensor of the inspection head is a sensor array covering a maximum area corresponding to an area such that, with the rotation of the part at each turn, the tool sweeps the entire surface to be machined, with the surface to be machined being a flat face of a part of revolution.
  • this maximum area corresponds to the area covered by the grinding wheel on the flat face of the part, i.e., in correspondence with the width of the surface between the outer diameter and the inner diameter of said flat face.
  • the present invention also relates to a machining method (e.g., a grinding method for grinding metal parts by means of a grinding wheel).
  • a machining method e.g., a grinding method for grinding metal parts by means of a grinding wheel.
  • the machining method object of the present invention comprises arranging a part on a support of a machining device, and machining a surface of the part by means of a machining tool of the device.
  • the machining method object of the present invention comprises in a novel manner:
  • This method allows an in-process inspection, i.e., at the same time as the grinding of the part, and with the advantage that by identifying the burn threshold value, it is possible to act immediately on the grinding parameters to prevent burn in the entire part. This therefore entails time and material savings since no defective parts are discarded.
  • the action performed by the control unit on at least one operating parameter of the machining device may comprise at least one of:
  • the method when it is detected that the variation of the eddy current distribution obtained as a result of microstructural changes on the surface of the part exceeds a predetermined threshold value, the method comprises:
  • the machining method uses a sensor array obtaining an eddy current distribution for the entire machining process of the part, with the eddy currents being processed to be shown in a single image (by means of C-Scan) representing the current distribution obtained for the entire surface to be machined swept along the maximum area covered by the sensor array as a function of time.
  • the data display obtained is therefore a color map based on the position of the coils of the sensor array over the course of the machining process, detecting when the variation of the eddy current distribution obtained exceeds the predetermined burn threshold value.
  • the C-scan image is intended to provide an uncomplicated visual representation of the process in order to provide the inspection result to the operator.
  • a color code has been defined and is shown in Figure 7 in gray scale to view the inspection result.
  • the light gray color represents the burn-free areas
  • the dark gray color represents the areas close to the threshold value
  • the black color represents the areas that have exceeded the threshold value.
  • the aforementioned representation allows knowing the location of the burn in the part, linking the coil number to its position in the part, which allows different process parameters to be adjusted in order to prevent the appearance of burn.
  • the present invention relates to a machining device (100) and method.
  • Figure 1 and Figure 2 schematically show the machining device (100).
  • the machining device (100) comprises a support (101) configured for receiving and fixing a part (200) to be machined.
  • the support (101) can be configured to rotate by means of a motor (102) and to imprint a rotation on the part (200) to be machined.
  • the device (100) comprises a machining tool (103) which, for the practical example shown in the figures, is a grinding machine with a grinding wheel (103).
  • the machining tool (103) is configured to rotate such that the part (200) is worn away by abrasion.
  • a control unit will be in charge of performing the machining according to initial machining parameters previously determined for the part (200) to be ground. This is the conventional method used in a grinding machine.
  • the device (100) comprises an inspection head (105) arranged close to the support (101).
  • the inspection head (105) comprises a fixing support or approaching means (104) for the fixing thereof to the machine and one or more magnetic field generators associated with one or more sensors.
  • the detection head (105) has several coils for generating eddy currents on the surface of the part (200). These coils can be arranged or grouped according to different configurations or alignments (or “arrays") for the purpose of producing a specific eddy current configuration on the part (200) to be inspected, such that the inspection is facilitated and the eddy current density is the most suitable for performing the inspection.
  • An inspection area (106) of the inspection head (105) is shown shaded in Figure 3 .
  • This inspection area (106) is the sensor array.
  • said shaded area corresponding to the sensor array (106) covers, with a plurality of coils, a maximum area which corresponds to the width of the surface machined by the tool or grinding wheel (103) between a maximum diameter and a minimum diameter of the flat face of the part (200).
  • the inspection head (105) is configured for generating, with the sensor array (106), a magnetic field directed towards a surface of the part (200) such that the control unit controls the electronics of the equipment to cause alternating current to pass through the sensor array (106) such that it generates an alternating magnetic field which, in the vicinity of the part (200), induces eddy currents on the surface of said part (200) as it is made of a conductive material.
  • the inspection head (105) When there are microstructural variations such as burns, cracks, pores, etc., they will be detected by the inspection head (105) when the sensor array (106) detects a variation in the eddy current distribution in the material producing a signal in the equipment.
  • the machining device (100) can be considered as the conjunction of a conventional machine with an inspection device, such that it is possible to inspect the part (200) to detect burns therein at the same time that the machining takes place (in-process).
  • control unit of the device (100) is configured for controlling one or more operating parameters related to the machining of the part (200).
  • Said parameters being those involved in grinding such as: a rotational speed of the machining tool (103), a rotational speed of the support (200) for the part (101), actuation of the approaching means, a speed of advancement of the tool (103) towards the part (200), and flow rate dosing of cooling fluid (e.g., coolant) on the surface of the part (200).
  • the inspection head (105) is connected to the control unit.
  • the control unit is configured for receiving and analyzing the signals coming from the inspection head (105).
  • control unit If the control unit detects that the signals coming from the inspection head (105) indicate a variation of the eddy current signal on the surface of the part (200) greater than a predetermined threshold, the control unit produces a first control action for controlling one or more operating parameters of the device (100).
  • This threshold is determined through specific tests forcing the excessive generation of burn in the part. Another system to establish this limit is to use standard parts with reference burns obtained by means of techniques other than grinding, such as laser, for example.
  • This threshold value takes into account a safety factor, whereby ensuring that the microstructure of the part is not damaged and that the generation of burn is anticipated.
  • the sensor is passed through the standard part and the maximum voltage is determined. Then, if said voltage or higher is obtained when inspecting the part once it is ground, the value obtained during the in-process inspection is considered the limit burn threshold.
  • the limit burn threshold value is thereby obtained, where other techniques of setting a threshold value that defines the limit of permissible microstructural variations so that the burn does not influence the mechanical characteristics of the part (200) can be used.
  • the control unit upon detecting that the signal coming from the inspection head (105) indicates a value greater than the predetermined threshold, the control unit acts during the machining process on one of the aforementioned grinding parameters without stopping the machine.
  • the eddy current distribution obtained by the sensor array (106) of the inspection head (105) for the entire machining process of the flat face of the part (200), to be processed and represented in a single image, known as a C-Scan.
  • This image represents a map of current distribution obtained for the entire surface to be machined swept along the maximum area covered by the sensor array (106) as a function of time, determining the time and position at which the pre-burn microstructural change defined by the predetermined threshold value occurs.
  • Figure 7 shows, in a gray scale representation, the representation of the grinding of the flat face of the part (200) up to the appearance of burn, with the horizontal axis representing the position as a function of the circumferential distance traveled by the sensor array (106) and the vertical axis representing the position of the values obtained between the inner diameter and the outer diameter of the flat face of the part.
  • the burn starts in the outer area of the part in the area shaded with a darker gray, such that, during the grinding process, when a threshold value is detected prior to the appearance of said burn, the control unit performs the corresponding changes of parameters.
  • the control unit may stop the machining operation completely. This may occur, for example, for the purpose of performing a parameter change operation which requires stopping the machine, such as applying a diamond coating on the machining tool (103), in order to improve and/or correct the surface characteristics of the machining tool (103) (e.g., to eliminate flat faces that may have appeared on the surface of the machining tool (103) and that could damage the surface of the part (200) during machining).
  • a parameter change operation which requires stopping the machine, such as applying a diamond coating on the machining tool (103), in order to improve and/or correct the surface characteristics of the machining tool (103) (e.g., to eliminate flat faces that may have appeared on the surface of the machining tool (103) and that could damage the surface of the part (200) during machining).
  • the inspection head (105) may comprise a support end (107) for the sensor array (106) with a surface configured for adapting to an axis of the part (200) to be machined, in this case a curved surface in correspondence with the axis of the part (200), such that the sensor covers the entire flat surface.
  • This flat surface corresponds to the maximum area of the width of the part (200) covered by the grinding wheel (103), such that the entire surface to be machined is swept at each turn.
  • the device (100) also comprises control means for controlling the separation distance between the inspection head (105) and the part (200).
  • control means for controlling the separation distance between the inspection head (105) and the part (200) may consist of a spring (not depicted) which allows maintaining a constant distance of the inspection head (105) with respect to the surface of the part (200), taking into account the dimensional variation (wear) that the surface of the part (200) sustains during machining/grinding operations.
  • the approaching means (104) serving as a support for the inspection head (105) comprising the sensor array (106) move in a guided manner on a guide (108) corresponding to the machining guide of the grinding machine.
  • This configuration allows a high precision in the approach positioning of the sensor array (106) in the direction perpendicular to the flat face to be machined of the part (200).
  • the approaching means comprise positioning means (109) preferably in the form of a contact tip with a micrometric head with knurling, which position the sensor array (106) in the plane perpendicular to the guided movement of the approaching means (104). It is envisaged that such a micrometric head with knurling will allow the position to be quantified to centesimal accuracy.
  • the machining method of the invention is exemplified, in which it can be schematically seen how the device (100) is made up of both a machining system and an inspection system.
  • machining parameters are used for performing the grinding process carried out by the process electronics of the control unit, and at the same time an in-process inspection is performed by means of the inspection electronics of the control unit. If the value obtained in the inspection exceeds the predetermined threshold value, the control unit will modify the operating parameters by establishing new parameters which prevent burns. If, on the contrary, the detected value is less than the threshold value predetermined as the burn limit, the grinding process continues.
  • this machining process successfully reduces production times and prevents the disposal of parts by preventing burns during the grinding process itself which could result in defective parts.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)
EP22383033.2A 2021-10-29 2022-10-26 Bearbeitungsvorrichtung und -verfahren Pending EP4173752A1 (de)

Applications Claiming Priority (1)

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ES202131021 2021-10-29

Publications (1)

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EP4173752A1 true EP4173752A1 (de) 2023-05-03

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EP22383033.2A Pending EP4173752A1 (de) 2021-10-29 2022-10-26 Bearbeitungsvorrichtung und -verfahren

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4495587A (en) * 1981-12-08 1985-01-22 Bethlehem Steel Corporation Automatic nondestructive roll defect inspection system
US4509295A (en) * 1981-04-01 1985-04-09 Estel Hoesch Werke Aktiengesellschaft Controlled grinding of rollers for elimination of cracks
US4514934A (en) * 1982-05-10 1985-05-07 Caterpillar Tractor Co. Method and apparatus for abrasively machining a workpiece

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4509295A (en) * 1981-04-01 1985-04-09 Estel Hoesch Werke Aktiengesellschaft Controlled grinding of rollers for elimination of cracks
US4495587A (en) * 1981-12-08 1985-01-22 Bethlehem Steel Corporation Automatic nondestructive roll defect inspection system
US4514934A (en) * 1982-05-10 1985-05-07 Caterpillar Tractor Co. Method and apparatus for abrasively machining a workpiece

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