Method for automatically controlling the triggering of sharpening of the cutting edge of a cutting blade for a cutting machine
The method addresses the inefficiencies in empirical sharpening frequency determination by monitoring mechanical torque components and blade wear, optimizing sharpening cycles to maintain cutting power and reduce frequency, thus enhancing productivity.
Patent Information
- Application Number
- FR2022000700
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-01-27
- Publication Date
- 2025-07-04
- Estimated Expiration
- 2042-01-27
AI Technical Summary
Existing methods for determining the sharpening frequency of cutting blades in flexible material cutting machines are empirical and do not account for variability in abrasive power, hardness, and geometry, leading to inefficient sharpening cycles and reduced productivity.
A method for automatically controlling the sharpening of cutting blades by monitoring mechanical action torque components and determining a threshold value based on geometric and material characteristics, triggering sharpening when the torque amplitude reaches a predetermined value, and comparing pre- and post-sharpening amplitudes to assess sharpening strip replacement.
This method optimizes sharpening cycles by aligning them with blade wear, maintaining cutting power and reducing unnecessary sharpening frequency, thereby enhancing productivity and simplifying operator parameterization.
Smart Images
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Abstract
Description
Title of the invention: Method for automatically controlling the triggering of sharpening of the cutting edge of a cutting blade for a cutting machine Technical field
[0001] The present invention relates to the general field of automatic cutting by a vibrating blade of a mattress of flexible material placed on a cutting table and in the form of a single ply or a stack of plies.
[0002] It relates more specifically to the automatic control of triggering an operation of sharpening the cutting edge of the cutting blade equipping such cutting machines. Prior art
[0003] One field of application of the invention is that of the automatic cutting of parts in a flexible textile or non-textile material (such as leather), in particular in the clothing, furniture or automobile upholstery industry.
[0004] A known method for automatically cutting pieces from a flexible material consists of bringing the material onto a fixed or mobile cutting support of the cutting table, in the form of a single ply or a stack of plies forming a mattress, and cutting the pieces by means of a cutting head moving above the cutting support of the table according to a previously defined placement program.
[0005] Typically, the cutting head of such a machine is formed of a steel blade which is vibrated vertically in the direction of its cutting edge in order to cut the material. A rotating blade guide serves as a slide for the blade and ensures its rotation.
[0006] It is also known that the cutting blade loses its cutting power as the cutting operation proceeds, so that it is necessary to regularly carry out sharpening operations on its cutting edge.
[0007] For this purpose, the cutting head can be equipped with an automatic sharpening system composed of two or three abrasive belts. When a sharpening operation is triggered, the blade rises and the abrasive belts of the sharpening system sharpen the two faces of the cutting edge of the blade in order to reform the edge.
[0008] These sharpening operations are generally periodic and distributed linearly over time throughout the life of the blade, regardless of the actual condition of its cutting edge.
[0009] The sharpening frequency is most often determined empirically, taking into account in particular the nature of the material cut and the wear of the blade which is generated by a sharpening operation. The latter corresponds to a loss of material and is determined experimentally by an abrasion law depending on the number of sharpenings, the size of the blade and the type of abrasive belt used. The position of the cutting edge is calculated based on the number of sharpening cycles carried out.
[0010] This empirical method for determining the sharpening frequency of the cutting blade is not optimal. Indeed, this method does not allow for the variability of the abrasive power throughout the lifetime of the sharpening strips to be taken into account. Since the initial abrasive power of the strips and the hardness and geometry of the cutting blades are not identical from one blade to another or from one set of strips to another, the empirical method does not allow for these variabilities to be taken into account. Given the diversity of the materials cut, the empirical method requires numerous tests to be implemented in order to determine the best set of parameters for each material / strip / blade triplet or to limit the choices by keeping a single set of parameters for several materials, thereby limiting the contributions of an optimal parameter setting. Statement of the invention
[0011] The main aim of the present invention is therefore to propose a method for automatically controlling the triggering of sharpening of the cutting edge of a cutting blade.
[0012] According to the invention, this aim is achieved by means of a method for automatically controlling the triggering of sharpening of the cutting edge of a cutting blade for a machine for cutting a mattress of flexible material, comprising: - determining components of a torque of mechanical actions at the guide point of the cutting blade in the blade reference frame, the components comprising: the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment, and the yaw moment of the cutting blade; - the determination of an admissible threshold value for a variable established from at least one of the components of the mechanical action torque and as a function of geometric parameters of the cutting blade and characteristics of thickness and material of the mattress to be cut; - monitoring during cutting of the material of variations in the amplitude of the variable chosen to determine the threshold value; and - the automatic triggering of an alert to request a sharpening cycle of the cutting edge of the cutting blade as soon as the amplitude of the variable chosen to determine the threshold value reaches said threshold value.
[0013] The method according to the invention is remarkable in that from the components of the torque of mechanical actions at the guiding point of the cutting blade, it is possible to automatically control the triggering of sharpening operations. The inventors have in fact demonstrated the existence of a relationship between the overall nature of the mechanical action torque at the blade guidance point and the state of the latter. The mechanical action torque identifies the forces undergone by the blade in the three directions. It is determined from measurements coming from a dynamometer installed in the presser foot of the cutting head and as described in patent application FR 3,108,542, the content of which is incorporated here by reference.
[0014] The method according to the invention thus makes it possible to trigger sharpening of the cutting edge of the blade only and as soon as the state of the cutting edge requires it. This results in productivity gains, taking into account the variabilities (hardness, geometries, composition, manufacturing, etc.) of the blades and sharpening strips or even the mechanical components located in the environment of these consumables, a simplification of the parameterization of the sharpening cycles for the operators.
[0015] According to one embodiment, the variable chosen to determine the threshold value corresponds to the vertical force component of the cutting blade.
[0016] In this embodiment, the variation in amplitude of the vertical force of the cutting blade during the cutting of the material is advantageously given by the following equation:
[0017] [Math.l] F z = ^(4 x M y 2 ) / has 2 - (f x 2+ F Y 2 )
[0018] in which Fz is the amplitude of the vertical force of the cutting blade, My is the amplitude of the pitching moment of the cutting blade, Fx is the amplitude of the frontal force of the cutting blade, FY is the amplitude of the lateral force applied to the blade, and L is the thickness of the mat to be cut.
[0019] According to one embodiment, the variable chosen to determine the threshold value corresponds to an inclination of the central axis of the cutting blade relative to the vertical axis, the variations in inclination of the central axis of the cutting blade relative to the vertical axis being calculated from all the values of the components of the mechanical action torque.
[0020] In this other embodiment, the variations in inclination of the central axis of the cutting blade relative to the vertical axis are calculated, for each point P with coordinates Ptxi, Ptyi, Ptzi of the central axis, by the following equation:
[0021] [Math.2] y z = To jarctar^ )
[0022] with m representing the number of acquisition points per measurement.
[0023] Advantageously, the method further comprises comparing the amplitudes of the variable chosen to determine the threshold value before and after a sharpening cycle of the cutting edge of the cutting blade in order to determine whether the sharpening strips of the sharpening tool need to be replaced. Indeed, it has also been noted by the inventors that the regeneration capacity of the cutting edge by the sharpening strips decreases depending on the number of sharpening operations carried out, which results in a value of the variable used after sharpening which is less and less distant from the threshold value. This additional step of the method thus makes it possible to determine the moment when the sharpening strips will have to be changed in order to maintain a cutting power compatible with the quality requirements and not to significantly increase the frequency of sharpening which penalizes the productivity of the cutting machines.
[0024] In this case, the method may further comprise the automatic triggering of an alert to request the changing of the sharpening bands of the sharpening tool as soon as the difference between the amplitude of the variable chosen to determine the threshold value after a sharpening cycle and the amplitude of the variable chosen to determine the threshold value before the sharpening operation becomes lower than a predetermined threshold.
[0025] Preferably, a sharpening cycle advantageously comprises an abrasion phase on each side of the cutting blade by sharpening strips in order in particular to reduce the radius of the cutting edge and increase its roughness. Brief description of the drawings
[0026] [Fig.l] [Fig.l] is a flowchart showing the different steps of the method according to the invention.
[0027] [Fig.2A-2C] Figures 2A, 2B and 2C represent evolution curves of the vertical force component of different cutting blades.
[0028] [Fig.3] [Fig.3] represents curves of the evolution of the inclination of the central axis of the cutting blade relative to the vertical axis. Description of the embodiments
[0029] The invention applies to the automated cutting of parts in a flexible material in the form of a mattress.
[0030] Such a cutting operation is generally carried out by means of a cutting machine equipped with a horizontal cutting support onto which the flexible material to be cut is brought.
[0031] A cutting head carrying a vibrating blade is mounted on a gantry which is caused to move along the cutting support while the cutting head moves simultaneously along the gantry so as to be able to follow the different cutting trajectories calculated by cutting software.
[0032] Typically, a presser foot is mounted on the lower part of the cutting head in order to press the flexible material onto its cutting support with a controlled force during cutting, the position of this presser foot being adaptable according to the height of the mattress placed on the cutting support. Thus, the presser foot allows the cutting blade to be guided as close as possible to the mattress.
[0033] The invention proposes a method for automatically controlling the triggering of sharpening of the cutting edge of the cutting blade of such a cutting machine.
[0034] Generally, the method according to the invention provides the following steps: - determining components of a torque of mechanical actions at the guide point of the cutting blade, the components comprising: the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment, and the yaw moment of the cutting blade - the determination of an admissible threshold value for a variable established from at least one of the components of the mechanical action torque and as a function of geometric parameters of the cutting blade and of thickness and material characteristics of the mattress to be cut - monitoring during cutting of the material of variations in the amplitude of the variable chosen to determine the threshold value, and - the automatic triggering of an alert to request a sharpening cycle of the cutting edge of the cutting blade as soon as the amplitude of the variable chosen to determine the threshold value reaches said threshold value.
[0035] The variable chosen to determine the threshold value may correspond either to the vertical force component of the cutting blade, or to an inclination of the central axis of the cutting blade relative to the vertical axis.
[0036] In practice, the method according to the invention is an algorithm implemented by software means equipping for example a workstation and the main steps of which are illustrated in [Fig.l].
[0037] The algorithm is fed as input by input parameters (SOI step) entered by the operator. These include the characteristics of the cutting blade (namely its geometry and the materials that constitute it), the characteristics of the material to be cut (namely thickness and material), and the maximum admissible value of the inclination of the central axis of the cutting blade in its new state.
[0038] During a step S02, it is also planned to determine the five components of a mechanical action torque at the guide point of the cutting blade, namely: the frontal force Fx, the lateral force Fz, the rolling moment Mx, the pitching moment MY, and the yaw moment Mz of the cutting blade.
[0039] This mechanical torque can be determined by means of the method described in patent application FR 3,108,542, the content of which is incorporated here by way of reference.
[0040] Briefly, the method described in this document provides for the use of a five-component dynamometer positioned on the presser foot and making it possible, from an algorithm based on the establishment of a dynamometer calibration matrix, to determine in real time the three-dimensional forces undergone by the cutting blade during the cutting operation.
[0041] More specifically, the dynamometer may comprise three triaxial piezoelectric sensors which are mounted in the presser foot by being distributed around a longitudinal axis of the blade or three coupled strain gauge bridges which are mounted on branches of the presser foot distributed around a longitudinal axis of the blade in order to form at least three complete bridges, or even five decoupled strain gauge bridges which are mounted on the presser foot.
[0042] From the data from steps S01 and S02, the method provides for determining a threshold value admissible by the cutting blade (step S03). This threshold value corresponds to a maximum value admissible either by the vertical force component of the cutting blade, or by the inclination of the central axis of the cutting blade relative to the vertical axis (depending on the variable chosen for controlling the triggering of sharpening). This parameterization will for example be determined from a predetermined chart and / or by setting a maximum value of the tangent of the curve between the initial value of the slope and the upper plate, this value will be adapted according to the safety coefficient that one wishes to integrate (close to zero: without safety margin, close to the initial tangent: with a large safety margin).
[0043] The cutting parameters (namely the conditions and strategies for cutting the parts, as well as the wear of the cutting edge of the cutting blade by sharpening operation) are then determined from the threshold value admissible by the cutting blade (step S04).
[0044] As indicated previously, the method according to the invention provides two approaches: the first by continuously monitoring in real time the amplitude of the vertical force component Fz of the cutting blade, and the second by continuously monitoring in real time the inclination of the central axis of the cutting blade relative to the vertical axis.
[0045] In the first approach, the method according to the invention provides during a step S05 to determine continuously and in real time the variation in amplitude of the vertical force component Fz of the cutting blade from the mechanical torque determined in step S02.
[0046] In practice, the variation in amplitude of the vertical force of the cutting blade during the cutting of the material is given by the following equation:
[0047] [Math.3] Xj WK j / J i V xV J_ J
[0048] in which Fz is the amplitude of the vertical force of the cutting blade, My is the amplitude of the pitching moment of the cutting blade, Fx is the amplitude of the frontal force of the cutting blade, FY is the amplitude of the lateral force applied to the blade, and L is the thickness of the mat to be cut.
[0049] The amplitudes over time of the vertical force component Fz of the cutting blade can thus be easily calculated and compared to the threshold value admissible by the cutting blade determined in step S03 (see step S06).
[0050] As soon as the amplitude of the vertical force component Fz reaches the admissible threshold value, the algorithm according to the invention automatically triggers an alert to request a sharpening cycle of the cutting edge of the cutting blade.
[0051] Upon receipt of this alert, the operator will therefore program a sharpening operation of the cutting edge of the cutting blade at the end of the cutting cycle (step S07). To this end, when a sharpening operation is triggered, the blade rises and the abrasive belts of the sharpening system sharpen the two faces of the cutting edge of the blade in order to reform the edge.
[0052] Figures 2A to 2C represent different examples of curves of evolution of the vertical force component of different cutting blades.
[0053] The curves shown in Figure 2A were obtained with the following cutting blade characteristics and cutting parameters: - Cutting blade material: high-speed steel designated under European standard HS 6-5-2 - Material to be cut: denim (namely a cotton serge used for making “jeans”) - Thickness of the mattress to be cut: 40mm (i.e. 40 folds of 1mm each)
[0054] In Figure 2A, the abscissa corresponds to the cutting length Le (in m) and the ordinate to the amplitude Fz of the vertical force of the cutting blade (in N).
[0055] The different curves C1 to C5 in Figure 2A correspond to different configurations in terms of cutting speed, vibration frequency of the cutting blade and cutting angle which are listed in the table below.
[0056] [Tables 1] Curve Cl Curve C2 Curve C3 Curve C4 Curve C5 Speed 40m / min 60m / min 40m / min 40m / min 60m / min Frequency 50Hz 50Hz 100Hz 100Hz 100Hz Cutting angle 30° 30° 30° 25° 25°
[0057] This figure 2A makes it possible to highlight that, for curves C1 to C3, the admissible threshold value for the amplitude Fz of the vertical force of the cutting blade is located around 380 N. For curves C4 and C5, this admissible threshold value is lower and is located around 330 N.
[0058] These bearings which differ depending on the characteristics of the cutting blade and cutting parameters indicate wear of the cutting edge of the cutting blade.
[0059] Also, as soon as the amplitude Fz of the vertical force of the cutting blade for the input parameters reaches this admissible threshold value, the algorithm automatically triggers an alert to program a sharpening operation of the cutting edge of the cutting blade.
[0060] Figures 2B and 2C are evolution curves obtained from other input characteristics, namely: - Cutting blade material: high-speed steel designated under European standard HS 4-3-8) - Material to cut: denim - Thickness of the mattress to be cut: 40mm (i.e. 40 folds of 1mm each)
[0061] The different curves C6 to CIO in Figures 2B and 2C correspond to the configurations listed in the table below.
[0062] [Tables2] Curve C6 Curve C7 Curve C8 Curve C9 Curve CIO Speed 40m / min 60m / min 40m / min 40m / min 60m / min Frequency 50Hz 50Hz 100Hz 100Hz 100Hz Cutting angle 30° 30° 30° 25° 25°
[0063] These figures 2B and 2C make it possible to demonstrate that, for curves C6 to C8, the admissible threshold value for the amplitude Fz of the vertical force of the cutting blade is located around 380 N and, for curves C9 and C10, this threshold value admissible is lower and is around 330 N.
[0064] In the second approach, the method according to the invention provides during a step S05' to continuously and in real time determine the variation in amplitude of the inclination of the central axis of the cutting blade relative to the vertical axis.
[0065] Indeed, it has been demonstrated that the introduction of the central axis of the cutting blade makes it possible to synthesize all of the components of the torque of the mechanical actions into an entity characteristic of the state of the blade during cutting. In particular, it has been shown that the inclination of the central axis, during a complete revolution of the blade, reflects the ability of the blade to make cuts that meet the specifications. Indeed, the use of the central axis associated with criteria for characterizing its evolution makes it possible to qualify the ability of the blade to cut a flexible material.
[0066] The amplitude of the inclination of the central axis of the cutting blade relative to the vertical axis is obtained by calculation from all the values of the components of the mechanical action torsor, namely the frontal force Fx, the lateral force Fz, the rolling moment Mx, the pitching moment MY, and the yaw moment Mz of the cutting blade obtained in step S02, and the vertical force Fz obtained in step S05.
[0067] More precisely, the variations in inclination of the central axis of the cutting blade relative to the vertical axis are calculated, for each point P with coordinates Ptxi, PtYi, Pt zi of the central axis, by the following equation:
[0068] [Math.4] । . \ HE ~ my /
[0069] in which yz is the inclination of the central axis of the cutting blade relative to the vertical axis and m represents the number of acquisition points per measurement.
[0070] The amplitudes over time of the inclination of the central axis of the cutting blade can thus be easily calculated and compared to the threshold value admissible by the cutting blade determined in step S03 (see step S06).
[0071] As soon as the amplitude of the tilt component of the central axis of the cutting blade reaches the admissible threshold value, the algorithm according to the invention automatically triggers an alert to request a sharpening cycle of the cutting edge of the cutting blade.
[0072] [Fig.3] represents different examples of curves of evolution of the inclination of the central axis of the same cutting blade operating with different cutting parameters.
[0073] The curves shown in [Fig.3] were obtained with the following cutting parameters: - Material to cut: denim - Thickness of the mattress to be cut: 40mm
[0074] The different curves C11 to C16 correspond to different configurations in terms of cutting speed, cutting blade vibration frequency and cutting angle which are listed in the table below.
[0075] [Tables3] Cil Curve C12 Curve C13 Curve C14 Curve C15 Curve C16 High speed steel blade HS 4-3-8 HS 6-5-2 HS 4-3-8 HS 4-3-8 HS 6-5-2 HS 4-3-8 Speed 40m / min 40m / min 40m / min 60m / min 40m / min 60m / min Frequency 100Hz 100Hz 50Hz 100Hz 100Hz 100Hz Cutting angle 30° 30° 30° 30° 25° 25°
[0076] This [Fig.3] makes it possible to highlight that the admissible threshold value for the inclination of the central axis of the cutting blade is located around 15° whatever the cutting parameters and the characteristics of the blade. This level indicates wear of the cutting edge of the cutting blade.
[0077] Also, as soon as the inclination of the central axis of the cutting blade for the input parameters reaches this admissible threshold value, the algorithm automatically triggers an alert to program a sharpening operation of the cutting edge of the cutting blade.
[0078] According to an advantageous arrangement of the invention (applicable to the two approaches described previously), it may be provided to compare the amplitudes of the variable chosen to determine the threshold value before and after a sharpening cycle of the cutting edge of the cutting blade in order to determine whether the sharpening strips of the sharpening tool need to be replaced.
[0079] Indeed, it has been found that the capacity for regeneration of the cutting edge by the sharpening strips decreases as a function of the number of sharpening operations carried out, which results in a value for the vertical force Fz or for the inclination of the central axis of the cutting blade after a sharpening operation which is less and less far from the admissible threshold value previously determined.
[0080] This advantageous arrangement therefore provides for automatically triggering an alert to request the changing of the sharpening bands of the sharpening tool as soon as the difference between the amplitude of the variable chosen to determine the threshold value after a sharpening cycle and the amplitude of the variable chosen to determine the threshold value before the sharpening operation becomes lower than a predetermined threshold.
[0081] This advantageous arrangement thus makes it possible to determine the moment when the bands sharpening tools must be changed in order to maintain a cutting power compatible with quality requirements and not to significantly increase the frequency of sharpening which penalizes the productivity of cutting machines.
Claims
Claims
1. Method for automatically controlling the triggering of sharpening of the cutting edge of a vibrating cutting blade for a machine for cutting a mattress of flexible material, comprising: - the determination (S02) of components of a mechanical action torque at the guide point of the cutting blade in the blade reference frame, the components comprising: the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment, and the yaw moment of the cutting blade - the determination (S03) of an admissible threshold value for a variable established from at least one of the components of the mechanical action torque and as a function of geometric parameters of the cutting blade and of thickness and material characteristics of the mattress to be cut; - monitoring during cutting of the material of variations in the amplitude of the variable chosen to determine the threshold value; and - the automatic triggering (S07) of an alert to request a sharpening cycle of the cutting edge of the cutting blade as soon as the amplitude of the variable chosen to determine the threshold value reaches said threshold value.
2.
3. Method according to claim 1, in which the variable chosen to determine the threshold value corresponds to the vertical force component (Fz) of the cutting blade. A method according to claim 2, wherein the variation in amplitude of the vertical force of the cutting blade during cutting of the material is given by the following equation: [Math.5] in which Fz is the magnitude of the vertical force of the cutting blade, Mx is the magnitude of the pitching moment of the cutting blade, Fx is the magnitude of the frontal force of the cutting blade, FY is the magnitude of the lateral force applied to the blade, and L is the thickness of the mat to be cut.
4. Method according to claim 1, in which the variable chosen to determine the threshold value corresponds to an inclination of the central axis of the cutting blade relative to the vertical axis, the variations in inclination of the central axis of the cutting blade relative to the vertical axis being calculated from all the values of the components of the mechanical action torque.
5. Method according to claim 4, in which the variations in inclination of the central axis of the cutting blade relative to the vertical axis are calculated, for each point P of coordinates Ptxi, PtYi, PtZi of the central axis, by the following equation: [Math.6] K - ™ j in which m represents the number of acquisition points per measurement.
6. A method according to any one of claims 1 to 5, further comprising comparing the magnitudes of the variable selected to determine the threshold value before and after a sharpening cycle of the cutting edge of the cutting blade to determine whether the sharpening strips of the sharpening tool need to be replaced.
7. The method of claim 6, further comprising automatically triggering an alert to request the changing of the sharpening bands of the sharpening tool as soon as the difference between the amplitude of the variable chosen to determine the threshold value after a sharpening cycle and the amplitude of the variable chosen to determine the threshold value before the sharpening operation becomes less than a predetermined threshold.
8. Method according to any one of claims 1 to 7, in which a sharpening cycle comprises an abrasion phase on each side of the cutting blade by sharpening strips in order in particular to reduce the radius of the cutting edge and to increase its roughness.