Method for automatically controlling the trigger for sharpening the cutting blade of a cutting machine

Abstract

The present invention relates to a method for automatically controlling the trigger for sharpening the sharp edge of a cutting blade of a cutting machine, comprising: determining (S02) a component of a mechanical action torso at a guiding point of the cutting blade at the blade reference; determining (S03) from at least one of the components of the mechanical action torso a tolerance threshold value of a variable set based on the geometric parameters of the cutting blade and on the thickness and material properties of the mattress to be cut; during the cutting of the material, monitoring the variation of the amplitude of the variable selected for determining the threshold value, and automatically triggering an alarm requesting a sharpening cycle of the sharp edge of the cutting blade as soon as the amplitude of the variable selected for determining the threshold value reaches said threshold value.

Description

[Technical field]

[0001] The invention relates to the general field of automatic cutting, by means of a vibrating blade, of mattresses of flexible material in the form of a ply or a stack of plies, which are placed on a cutting table.

[0002] More specifically, the present invention relates to automatic control of a trigger for sharpening the sharp cutting edge of a cutting blade attached to such a cutting machine. [Background technology]

[0003] One field of application of the invention is the automated cutting of pieces from woven or non-woven flexible materials (such as leather), in particular in the clothing, furniture or automotive upholstery industries.

[0004] A known method for automatically cutting pieces from flexible material consists of introducing the material, in the form of a single ply or a stack of plies forming a mattress, onto a fixed or movable cutting support of a cutting table and cutting the pieces by means of a cutting head moving above the cutting support of the table according to a predefined layout program.

[0005] Typically, the cutting blade of such machines is made of a steel blade that is oscillated vertically along the direction of its sharp cutting edge to cut the material. A rotating blade guide acts as a slide for the blade and ensures the rotation of the blade.

[0006] It is also known that cutting blades lose their cutting power as cutting operations are performed and therefore require periodic sharpening to maintain their sharpness.

[0007] For this purpose, the cutting head can be equipped with an automatic sharpening system consisting of two or three abrasive belts. When the sharpening operation is triggered, the blade rises and the abrasive belts of the sharpening system sharpen both sides of the sharp cutting edge of the blade to give it a neat cutting edge.

[0008] These sharpening operations are generally performed cyclically and are timed linearly throughout the life of the blade, regardless of the actual condition of the sharpness of the cutting edge.

[0009] The number of sharpening passes is often determined empirically, taking into account, among other things, the nature of the cutting material and the wear of the blade caused by the sharpening operations. The latter corresponds to the loss of material and is determined experimentally by wear laws that depend on the number of sharpening passes, the dimensions of the blade and the type of abrasive belt used. The position of the sharp edge is calculated based on the number of sharpening passes.

[0010] This empirical method for determining the frequency of sharpening the cutting blades is not optimal. In fact, it does not take into account the variation of the abrasive forces over the life of the sharpening belt. The initial abrasive forces of the belt and the hardness and shape of the cutting blades are not the same for each cutting blade or even for each set of belts. Due to the variety of materials to be cut, the empirical method requires numerous tests to be performed to determine the optimal parameter set for each material / belt / cutting blade triplet, or to limit the options by maintaining a single parameter set for several materials, thus limiting the inputs of the optimal parameterization. Summary of the Invention

[0011] SUMMARY OF THE PRESENT EMBODIMENT The main object of the present invention is therefore to propose a method for automatically controlling the trigger for sharpening the cutting edge of a cutting blade. [Means for solving the problem]

[0012] According to the invention, the object is to provide a method for automatically controlling a trigger for sharpening the sharp edges of cutting blades of a machine for cutting mattresses of flexible material, the method comprising the steps of: - determining the components of the mechanical action torsion at the guiding point of the cutting blade at the blade reference, said components including the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment and the yawing moment of said cutting blade; - determining from at least one of the components of the mechanical action torso the geometric parameters of the cutting blade and the tolerance thresholds of the variables that are set based on the thickness and material properties of the mattress to be cut; - monitoring, during cutting of the material, the variation in amplitude of the selected variable for determining the threshold value; - automatically triggering an alarm requesting a sharpening cycle of the cutting blade sharpening edge as soon as the amplitude of the variable selected to determine the threshold value reaches said threshold value; This is achieved by means of a method comprising:

[0013] The method according to the invention is remarkable in that it allows the triggering of the sharpening action to be automatically controlled from the components of the mechanical action torso at the guide point of the cutting blade. The inventors have noticed that there is a relationship between the overall nature of the mechanical action torso at the guide point of the blade and the condition of the blade. The mechanical action torso specifies the forces to which the blade is subjected in three directions. This is determined from measurements from a dynamometer installed in the pressure foot of the cutting head, the contents of which are described in patent application FR 3,108,542.

[0014] In this way, the method according to the invention makes it possible to trigger the sharpening of the cutting edge only when the state of the cutting edge requires it and immediately, thus increasing productivity and simplifying the parameterization of the sharpening cycle for the operator, taking into account the variability (hardness, shape, composition, manufacture, etc.) of the knives and sharpening belts or of the machine parts in the environment of these consumables.

[0015] According to one embodiment, the variable selected to determine the threshold value corresponds to a normal force component of the cutting blade.

[0016] In this embodiment, the change in amplitude of the normal force of the cutting blade during cutting of the material is advantageously given by the following formula:

[0017]

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[0018] According to one embodiment, the variable selected to determine the threshold value corresponds to the inclination of the central axis of the cutting blade relative to the vertical axis, and the variation of the inclination of the central axis of the cutting blade relative to the vertical axis is calculated from all values ​​of the components of the mechanical action torso.

[0019] In this other embodiment, the variation in the inclination of the central axis of the cutting blade with respect to the vertical axis is expressed as the coordinate Pt xi ,Pt yi ,Pt zi For each point P with

number

[0020] Advantageously, the method further comprises comparing the amplitude of the variable selected to determine the threshold value before and after a sharpening cycle of the sharpening edge of the cutting blade, in order to determine whether or not the sharpening belt of the sharpening tool needs to be replaced. In fact, the inventors have also pointed out that the ability of the sharpening belt to regenerate the sharpening edge decreases as a function of the number of sharpening operations carried out, so that the value of the variable used after sharpening approaches the threshold value. This additional step of the method makes it possible to determine the moment when the sharpening belt must be replaced in order to maintain a cutting force that complies with the quality requirements and not to significantly increase the frequency of sharpening operations that would reduce the productivity of the cutting machine.

[0021] In this case, the method may further comprise automatically triggering an alert to request a change of the sharpening belt of the sharpening tool as soon as the difference between the amplitude of the variable selected for determining the threshold after the sharpening cycle and the amplitude of the variable selected for determining the threshold before the sharpening operation falls below a predetermined threshold.

[0022] Preferably, the sharpening cycle advantageously consists of an abrasion stage on each side of the cutting blade by an abrasive belt, in particular to reduce the radius of the sharp cutting edge and to increase its roughness. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a flow chart illustrating the different steps of the method according to the invention.

[0024] [Figure 2A] FIG. 2A shows the curves of the change in the normal force component for various cutting blades. [Figure 2B] FIG. 2B shows the curves of the change in the normal force component for various cutting blades. [Figure 2C] FIG. 2C shows the curves of the change in the normal force component for various cutting blades.

[0025] [Diagram 3] FIG. 3 is a curve showing the change in the inclination of the central axis of the cutting blade relative to the vertical axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The invention applies to the automatic cutting of pieces from a mattress-like flexible material.

[0027] Such cutting operations are typically performed by a cutting machine having a horizontal cutting support on which the flexible material to be cut rests.

[0028] The cutting heads, equipped with oscillating cutting blades, are mounted on a crossbar along which they move in unison to follow different cutting trajectories calculated by the cutting software.

[0029] A pressure foot is usually attached to the lower part of the cutting head for pressing the flexible material against the cutting support with a controlled force during cutting, the position of which can be adapted depending on the height of the mattress laid on the cutting support, so that the cutting blade can be guided as close as possible to the mattress.

[0030] The present invention proposes a method for automatically controlling a trigger for sharpening the cutting edge of the cutting blade of such a cutting machine.

[0031] In general, the method according to the invention provides the following steps: - determining the components of the mechanical action torso at the guiding point of the cutting blade, said components consisting of the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment and the yawing moment of the cutting blade. - Determining tolerance thresholds of variables from at least one of the components of the mechanical action torso, which are set based on the geometric parameters of the cutting blade and the thickness and material properties of the mattress to be cut. - monitoring, during cutting of the material, the variation in amplitude of the selected variable to determine the threshold value. - automatically triggering an alarm to request a sharpening cycle of the cutting blade sharpening edge as soon as the amplitude of the variable selected to determine the threshold value reaches said threshold value.

[0032] The variable selected to determine the threshold value may correspond to either the normal force component of the cutting blade or the inclination of the central axis of the cutting blade relative to the normal axis.

[0033] In practice, the method according to the invention is an algorithm executed by software means, for example equipped in a computer workstation, the main steps of which are illustrated in FIG.

[0034] The algorithm receives input parameters entered by the operator (step S01), including the characteristics of the cutting blade (i.e. its shape and the material it is made of), the characteristics of the material to be cut (i.e. thickness and material), and the maximum allowable tilt of the central axis of the cutting blade in its new state.

[0035] During step S02, it is also planned to determine five components of the mechanical action torso at the guiding point of the cutting blade, namely the front force Fx, the lateral force Fz, the rolling moment Mx, the pitching moment My and the yawing moment Mz of the cutting blade.

[0036] During the vertical vibration and when cutting the material, the cutting blade is subjected to a number of forces. The frontal force Fx is the force that the cutting blade is subjected to when it contacts the material during the cutting operation. The lateral force Fz is the force that one side of the cutting blade is subjected to when it contacts the material during the cutting operation. As for the vertical forces, they are the forces that the blade is subjected to in an oscillatory motion along a vertical axis.

[0037] This mechanical torsor can be determined by the method described in patent application FR 3,108,542.

[0038] In brief, the method described herein provides for the use of a five-component dynamometer positioned on the presser foot, enabling the real-time determination of the three-dimensional forces experienced by the cutting blade during the cutting operation from an algorithm based on establishing a calibration matrix of the dynamometer.

[0039] More specifically, the dynamometer may consist of three 3-axis piezoelectric sensors distributed around the longitudinal axis of the blade and attached to the presser foot, or three bonded strain gauge bridges distributed around the longitudinal axis of the blade and attached to the branches of the presser foot to form at least three complete bridges, or five unbonded strain gauge bridges attached to the presser foot.

[0040] From the data derived from steps S01 and S02, the method provides for determining the threshold value tolerated by the cutting blade (step S03). This threshold value corresponds to the maximum value tolerated either by the normal 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 selected to control the trigger of the sharpening). This parameterization is for example determined from a given chart and / or by setting the maximum value of the tangent of the curve constructed between the initial value of the inclination and the upper plateau, this value being adapted based on an integrated safety factor (close to zero: no safety margin, close to the initial tangent: with a large safety margin).

[0041] Next, the cutting parameters (i.e., conditions and strategies for cutting the pieces, and wear of the sharp edge of the cutting blade due to sharpening action) are determined from the tolerance thresholds by the cutting blade (step S04).

[0042] As previously indicated, the method according to the invention provides two approaches: the first is to measure the normal force component F of the cutting blade. Z and secondly, by continuous and real-time monitoring of the inclination of the central axis of the cutting blade relative to the vertical axis.

[0043] In a first approach, the method according to the invention comprises, during step S05, determining the normal force component F of the cutting blade from the mechanical torsor determined in step S02. Z A method for determining the amplitude variation of a signal from a signal having a frequency of 10 Hz to a signal having a frequency of 10 Hz is provided.

[0044] In practice, the change in amplitude of the normal force of the cutting blade during cutting of the material is given by the following formula:

[0045]

number

[0046] In this way, the amplitude of the blade normal force component Fz over time can be easily calculated and compared with the blade tolerance threshold determined in step S03 (see step S06).

[0047] As soon as the amplitude of the normal force component Fz reaches a tolerable threshold, the algorithm according to the invention automatically triggers a warning requesting a sharpening cycle of the cutting blade sharpening edge.

[0048] Upon receiving this warning, the operator therefore programs the sharpening of the cutting blade's sharp edge at the end of the cutting cycle (step S07). Thus, when the sharpening operation is triggered, the blade is raised and the abrasive belt of the sharpening system sharpens both sides of the blade's sharp edge to reshape the cutting edge.

[0049] 2A to 2C show different examples of curves of normal force component variation for different cutting blades.

[0050] The curves depicted in FIG. 2A were obtained with the following cutting blade and cutting parameters characteristics: -Cutting blade material: high speed steel according to European standard HS 6-5-2. -Material to be cut: denim (i.e. cotton twill used in the manufacture of "jeans") - The thickness of the mattress to be cut is 40mm (i.e. 40 layers of 1mm each).

[0051] In FIG. 2A, the horizontal axis corresponds to the cutting length Lc (unit: m), and the vertical axis corresponds to the amplitude FZ of the normal force of the cutting blade (unit: N).

[0052] The different curves C1-C5 in FIG. 2A correspond to different configurations in terms of cutting speed, cutting blade vibration frequency and cutting angle, and are listed in the table below.

[0053] [Table 1]

[0054] This FIG. 2A highlights that for curves C1 to C4, the tolerance threshold of the amplitude FZ of the normal force of the cutting blade is located in the vicinity of 380N, while for curves C4 and C5, this tolerance threshold is lower, in the vicinity of 330N.

[0055] These levels vary depending on the characteristics of the cutting blade and the cutting parameters, but are indicative of wear of the sharp cutting edge of the cutting blade.

[0056] Also, as soon as the amplitude Fz of the normal force of the cutting blade relative to the input parameters reaches this tolerance threshold, the algorithm automatically triggers an alarm to program an action to sharpen the sharp edge of the cutting blade.

[0057] 2B and 2C are evolution curves obtained from other input characteristics, namely the following characteristics: -Cutting blade material: High speed steel as specified in European standard HS 4-3-8 -Cutting material: Denim -The thickness of the mattress to be cut is 40mm (i.e. 40 plies of 1mm each)

[0058] The different curves C6-C10 in Figures 2B and 2C correspond to the configurations listed in the table below.

[0059] [Table 2]

[0060] From Figures 2B and 2C, it can be emphasized that for curves C6 to C8, the tolerance threshold of the amplitude Fz of the normal force of the cutting blade is located in the vicinity of 380 N, while for curves C9 and C10, this tolerance threshold is lower, in the vicinity of 330 N.

[0061] In a second approach, a method according to the invention is provided for determining, during step S05', continuously and in real time, the variations in the amplitude of the inclination of the central axis of the cutting blade relative to the vertical axis.

[0062] In fact, it has been demonstrated that the introduction of the central axis of the cutting blade makes it possible to synthesize all components of the mechanical action torso into an entity that is characteristic of the state of the blade during cutting. In particular, it has been shown that the tilt of the central axis during a complete revolution of the cutting blade reflects the blade's ability to perform a cut that meets the specifications. In fact, the use of the central axis in conjunction with a criterion that characterizes the change in the central axis makes it possible to qualify the blade's ability to cut flexible materials.

[0063] The amplitude of the inclination of the central axis of the cutting blade relative to the vertical axis is calculated from all the values ​​of the components of the mechanical action torso, i.e., the front force Fx, lateral force Fz, rolling moment Mx, pitching moment My, and yawing moment Mz of the cutting blade obtained in step S02, and the vertical force Fz obtained in step S05.

[0064] The mechanical action components evolve according to the wear of the cutting blade and the decrease of the cutting forces. The evolution of the cutting forces and moments leads to the evolution of the slider (direction of the central axis) of the mechanical action torso. The central axis then follows the direction of the result of the forces. Since the evolution of the normal force Fz is more important than the other components of the torso (Fx and FY), it is interesting to study the evolution of the direction of the central axis relative to the vertical measurement axes.

[0065] The variation in the inclination of the central axis of the cutting blade with respect to the vertical axis is expressed as the coordinate Pt xi ,Pt yi ,Pt zi For each point P, the following formula is used:

[0066]

number

[0067] In this way, the amplitude of the tilt of the central axis of the cutting blade over time can be easily calculated and compared with the threshold value that the cutting blade is allowed to tolerate determined in step S03 (see step S06).

[0068] As soon as the amplitude of the component of the tilt of the central axis of the cutting blade reaches a tolerance threshold, the algorithm according to the invention automatically triggers a warning requesting a sharpening cycle of the cutting edge of the cutting blade.

[0069] FIG. 3 shows different examples of curves of change in central axis inclination for the same cutting blade operating with different cutting parameters.

[0070] The curves shown in FIG. 3 were obtained with the following cutting parameters: -Cutting material: Denim - Mattress thickness to be cut: 40mm

[0071] The different curves C11 to C16 correspond to different configurations in terms of cutting speed, cutting blade vibration frequency and cutting angle and are listed in the table below.

[0072] [Table 3]

[0073] This figure highlights that the tolerance threshold for the inclination of the blade axis is located around 15°, regardless of the cutting parameters and blade characteristics. This level indicates wear of the sharp cutting edge of the blade.

[0074] Also, as soon as the inclination of the blade's central axis relative to the input parameters reaches this tolerance threshold, the algorithm automatically triggers a warning and programs an action to sharpen the blade's sharp edge.

[0075] According to one advantageous arrangement of the invention (applicable to the two approaches described above), it may be provided to compare the amplitude of a variable selected to determine a threshold value before and after a sharpening cycle of the sharpening edge of the cutting blade in order to determine whether the sharpening belt of the sharpening tool needs to be replaced.

[0076] In fact, it was found that the ability of the sharpening belt to regenerate a sharp cutting edge decreases as a function of the number of sharpening operations performed, with the result that the value of the normal force Fz or the inclination of the central axis of the cutting blade after each sharpening operation becomes increasingly closer to the tolerance threshold value previously determined.

[0077] This advantageous arrangement therefore provides for automatically triggering an alarm to request a change of the sharpening belt of the sharpening tool as soon as the difference between the amplitude of the variable selected for determining the threshold after a sharpening cycle and the amplitude of the variable selected for determining the threshold before a sharpening operation falls below a predetermined threshold.

[0078] This advantageous arrangement makes it possible to determine the moment when the sharpening belt must be replaced in order to maintain a cutting force that complies with the quality requirements and not to significantly increase the frequency of sharpening operations, which would reduce the productivity of the cutting machine.

Claims

1. 1. A method for automatically controlling a trigger for sharpening a cutting blade of a machine for cutting a mattress of flexible material, comprising: - determining the components of the mechanical action torsion at the guiding point of the cutting blade at the blade reference (S02), said components including the frontal force, the lateral force, the vertical force, the rolling moment, the pitching moment and the yawing moment of said cutting blade; - determining (S03) from at least one of the components of the mechanical action torso the geometric parameters of the cutting blade and the tolerance thresholds of the variables that are set based on the thickness and material properties of the mattress to be cut; - monitoring the variation in amplitude of a selected variable during cutting of the material to determine a threshold value; - automatically triggering an alarm requesting a sharpening cycle of the cutting blade sharpening edge as soon as the amplitude of the variable selected to determine the threshold value reaches said threshold value (S07); A method comprising:

2. The variables selected to determine the threshold were the normal force component of the cutting blade (F Ｚ 2. The method of claim 1 , which corresponds to

3. 3. The method of claim 2, wherein the variation in amplitude of the normal force of the cutting blade during cutting of the material is given by the following formula: [0050] Here, F Ｚ is the amplitude of the force perpendicular to the cutting edge, M Ｙ is the amplitude of the pitching moment of the cutting blade, F Ｘ is the amplitude of the force in the front direction of the cutting blade, F Ｙ is the amplitude of the lateral force on the cutting blade, and L is the thickness of the mattress being cut.

4. 2. The method according to claim 1, wherein the variable selected to determine the threshold value corresponds to an inclination of the central axis of the cutting blade relative to a vertical axis, and the variation of the inclination of the central axis of the cutting blade relative to the vertical axis is calculated from all values ​​of the components of the mechanical action torso.

5. The variation in the inclination of the central axis of the cutting blade relative to the vertical axis is expressed as the coordinate Pt ｘｉ , Pt ｙｉ , Pt ｚｉ 5. The method of claim 4, wherein for each point P having [006] Here, m represents the number of points acquired per measurement.

6. 6. The method of claim 1, further comprising comparing the amplitude of the variable selected to determine the threshold value before and after a sharpening cycle of the cutting blade sharpening edge to determine whether the sharpening belt of the sharpening tool needs to be replaced.

7. 7. The method of claim 6, further comprising automatically triggering an alarm to request a change of the sharpening belt of the sharpening tool as soon as the difference between the amplitude of the variable selected to determine the threshold after a sharpening cycle and the amplitude of the variable selected to determine the threshold before a sharpening operation falls below a predetermined threshold.

8. A method according to any one of claims 1 to 7, wherein the sharpening cycle comprises a stage of abrasion of each flank of the cutting blade by means of an abrasive belt, in particular to reduce the radius of the sharp edge and to increase its roughness.

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