JP2006136926A - Calculation method of friction coefficient between work and die, detection method of bending angle, and bending machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for detection of bending angle of a work by detecting strain in a die. <P>SOLUTION: The method for bending a platy work W comprises the steps of: measuring of a strain pattern in the die 5 using strain sensors S1-S4 arranged on the die 5; deciding a estimation formula of the strain pattern by comparing the measured strain pattern with a plurality of strain patterns stored beforehand in a database 15; obtaining the friction coefficient based on the decided estimation formula; and calculating the bending angle of the work based on the detected value of the strain sensor, using a bending angle estimation formula corresponding to the pattern estimation formula. The strain sensors to detect the strain in the die during bending of the work are provided at a plurality of positions. The control means 9 comprises a database 15, a estimation formula decision means 17 to decide the pattern estimation formula by comparing the detected strain pattern in the die 5 with strain patterns stored in the database 15, and a calculation means 21 to obtain the friction coefficient using the pattern estimation formula. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and a folding method for calculating a friction coefficient between a workpiece and a die when a plate-shaped workpiece is bent by a bending machine such as a press brake having a punch and a die. The present invention relates to a bending angle detection method and a bending machine.

  Conventionally, various bending angle detection devices have been developed and proposed for detecting the bending angle of a workpiece when a plate-shaped workpiece is bent by a bending machine such as a press brake. . The conventional bending angle detection device is configured to calculate the bending angle of a workpiece by detecting the entry position of the workpiece into the V groove in the die electrically, optically or mechanically, and the horizontal position of the workpiece on the die. In general, the bending angle of the workpiece is detected by optically or mechanically detecting the inclination angle caused by the upward jump from the state.

In recent years, it has been proposed to embed a plurality of strain sensors in a die and obtain a work bending angle by calculation based on the strain of the die detected by each of the strain sensors (Non-Continued) Patent Document 1).
"Measurement of bending process using a sensor system with a built-in mold" 54th Plastic Processing Joint Lecture Meeting (2003.11.6-8 Kagawacho) 247-248

  The non-patent document 1 has the following description corresponding to the description of FIG.

Positions S ₁ (X ₁ , Y ₁ ), S ₂ (X ₂ , Y ₂ ), S ₃ (X ₃ , Y ₃ ), S ₄ ( X ₄ , Y ₄ ) is S _i (X _i , Y _i ), the position of the force F acting on the shoulder of the mold body is F (X, Y), and The radius is R, the angle between the upper surface of the mold body and the work W is θ, and each position S of each strain sensor is determined from the vertical line passing through the position F (X, Y) and the position F (X, Y). _{If the} angles θ ₁ to θ ₄ formed with the lines connecting _{1 to} S ₄ are θ _i , the relational equation of force and strain distribution according to the distance is given by the following equation.

σ = − (2F · Cos 2θ _i ) / (πr) (1)
Here, r is the distance away from the force and the element. The point of action of force F is on the shoulder arc, and is given by:

(X−X ₀ ) ² + (Y−Y ₀ ) ² = R ₀ ² (2)
An angular relational equation between the contact point and each sensor is given by the following equation.

θ ₁ = tan ⁻¹ [(X−X ₀ ) / (Y−Y ₀ )] (3)
θ _i = tan ⁻¹ [(X−X _i ) / (Y−Y _i )] (4)
The relational equation between the strain value (Ex, Ey) obtained from the sensor and the output voltage is given by the following equation.

V = C · (Ex−Ey) (5)
Here, V is an output voltage, and C is a gauge coefficient.

  If the above equations are solved simultaneously, the information of the action point F (X, Y) of the force F can be obtained. However, when considering the influence of frictional force, two or more sensors are required.

  That is, according to the above description, if there are two or more strain sensors, the information on the force F can be grasped more accurately in consideration of the influence of the frictional force, and the relationship between the strain distribution and the bending angle of the workpiece can be further improved. It will be able to grasp accurately.

  Therefore, the present invention seeks to provide a method and a bending machine capable of obtaining a friction coefficient by detecting strain of a die having a plurality of strain sensors and detecting a bending angle of a workpiece. is there.

  In view of the above, the present invention provides a method for bending a plate-shaped workpiece by a bending machine equipped with a punch and a die. A strain pattern is measured, and an initial pattern of a plurality of pattern estimation formulas stored in advance in a database is compared with the measured strain pattern to determine a pattern estimation formula, and the workpiece and die are determined by the determined pattern estimation formula. The coefficient of friction between the two is obtained.

  Further, in the present invention, when a plate-shaped workpiece is bent by a bending machine equipped with a punch and a die, the strain pattern of the die at the initial stage of the bending process is obtained by a strain sensor provided in the die. Measure and compare the initial pattern of a plurality of strain patterns stored in advance in the database with the measured strain pattern to determine the pattern estimation formula, and use the bending angle estimation formula corresponding to the determined pattern estimation formula The bending angle of the workpiece is calculated based on the detection value of the strain sensor.

  Further, the present invention is a bending machine comprising a punch and a die for bending a plate-shaped workpiece, and the die detects distortion of the die when the workpiece is bent. The control means for controlling the bending machine is a plurality of pattern estimation formulas showing the relationship between the work bending time and the amount of distortion of the die. An estimation formula for determining a pattern estimation formula by comparing a strain pattern of the die at the initial stage of bending processing detected by each strain sensor with an initial pattern of a pattern estimation formula stored in the database Characterized by comprising: a determining means; and a calculating means for obtaining a friction coefficient between the workpiece and the die by a pattern estimation expression determined by the estimation expression determining means. Than it is.

  Further, the present invention is a bending machine comprising a punch and a die for bending a plate-shaped workpiece, and the die detects distortion of the die when the workpiece is bent. The control means for controlling the bending machine has a plurality of strain patterns indicating the relationship between the bending time of the workpiece and the strain amount of the die. Estimating formula determining means for determining a pattern estimating formula by comparing a stored database with a strain pattern of the die detected by each strain sensor at an initial stage of bending and an initial pattern of the strain pattern stored in the database And a calculation means for calculating the bending angle of the workpiece based on the pattern estimation formula determined by the estimation formula determination means and the detection value of each strain sensor. It is intended to.

  According to the present invention, a coefficient of friction between a work and a die can be obtained, and an expression indicating a relationship between a die distortion and a work bending angle can be obtained. Then, the bending angle of the workpiece can be detected by substituting the detected die distortion into the above equation.

  FIG. 1 conceptually and schematically shows a press brake as a bending machine according to an embodiment of the present invention. The bending machine 1 includes a punch 3 and a die 5 for bending a plate-like workpiece W. Further, the bending machine 1 is provided with a driving means 7 for operating the punch 3 so as to be relatively close to and away from the die 5 and an NC for controlling the driving means 7. A control means 9 is provided for each device.

  A sensor unit 11 provided with a plurality of strain sensors S1, S2, S3, S4 at appropriate intervals is embedded in the die 5 in the vicinity of the inclined surface 5F of the V groove 5V. Since the sensor unit 11 has the same configuration as the sensor unit described in Non-Patent Document 1, a detailed description of the sensor unit 11 is omitted.

  In the above configuration, various data such as material, plate thickness, and V width of the V groove 5V necessary for bending the workpiece W are input from the input unit 13, and the driving unit 7 is controlled by the control device 9. When bending of the workpiece W on the die 5 is started, the workpiece W is pressurized between the die 5 and the punch 3, so that the distortion of the die 5 is detected by the sensor unit 11 embedded in the die 5. It is something that can be done.

  In the above configuration, when the punch 3 is moved close to (lowered) the die 5 at a constant speed under the control of the control device 9 and the workpiece W is bent (simulated), the tip of the punch 3 is moved. The relationship between the time after contact with the workpiece W and the detected values of the strain sensors S1 to S4 is the strain patterns P1 to P4 as shown in FIG. As is apparent from the measurement result shown in FIG. 3, it can be understood that the change in the detected value of the strain amount by the strain sensor S1 disposed in the vicinity of the V groove 5 in the die 5 is large (strain pattern P1).

  Further, as shown in FIG. 3, the strain patterns detected by the strain sensors S1 to S4 are strains of the strain sensors S2 to S4 when a predetermined time T has elapsed since the bending of the workpiece W was disclosed. You can see that the direction changes. The strain direction is switched because the workpiece W is bent from the state in which the workpiece W is in contact with the upper surface of the die 5, and the contact position between the workpiece W and the die 5 is a minute arc of the die 5. After passing through the shoulder portion of the die 5 and moving to the inclined surface 5F of the V groove 5V of the die 5, the contact position between the die 5 and the work W changes, and the pressing direction of the work W against the die 5 at the contact position is changed. Is presumed to change.

  That is, as a characteristic when the work W is bent, there is a portion where the strain direction of the die 5 is switched at the initial stage of the bending process.

  By the way, although the distortion measurement of the die 5 is shown in the relationship between the detection values of the respective strain sensors S1 to S4 and the time, the workpiece W is bent by keeping the lowering speed of the punch 3 constant. The elapsed time after the punch 3 comes into contact with W, that is, the lowered position of the punch 3 can be converted. In other words, it is possible to show the relationship between the lowered position after the punch 3 contacts the workpiece W and the amount of distortion of the die 5. That is, the relationship between the lowered position of the punch 3 and the distortion amount of the die 5 can be expressed by an empirical formula or the like.

  Further, since it can be expressed by the relationship between the lowered position of the punch 3 and the amount of distortion of the die 5, the amount of distortion of the die 5 can be calculated by converting the lowered position of the punch 3 into the bending angle of the workpiece W. It can be expressed in relation to the bending angle of W. In other words, the bending angle of the workpiece W can be calculated by detecting the amount of distortion of the die 5. Therefore, by knowing in advance the relationship between the distortion amount of the die 5 and the bending angle of the workpiece W, the bending angle of the workpiece W can be known by detecting the distortion amount of the die 5. It is.

  Next, in order to confirm whether the strain pattern changes depending on the magnitude of friction between the die 5 and the workpiece W, only the friction coefficient (μ1 to μ5) between the die 5 and the workpiece W is determined. FIG. 4 shows changes in the detected value of the strain sensor S2 when the workpiece W is bent (simulated) under the same conditions. As is apparent from the results of FIG. 4, as the friction coefficient is larger (μ5) as compared with the case where the friction coefficient is smaller (μ1), the amount of strain, that is, the change in the detected value of the strain sensor S2 is larger, and The replacement appears more clearly. That is, when the friction coefficient is different, the strain pattern of the die 5 is different. Therefore, if the distortion pattern of the die 5 is known during bending of the workpiece W, the friction coefficient of the workpiece W can be known from this distortion pattern. By the way, when the detection patterns of the respective strain sensors S1 to S4 in the case where the friction coefficients (μ1 to μ5) are variously different are also displayed, it is as shown in FIG.

  By the way, as described above, the detection values of the respective strain sensors S1 to S4 can be converted into the bending angle of the workpiece W. Therefore, in order to relate the detected values of the strain sensors S1 to S4 and the bending angle of the workpiece W, the time axis is made the same as the time axis of the strain sensors S1 to S4, and the relationship with the bending angle of the workpiece W is determined. When the single estimation formula shown is created, the result is as shown in FIG. In this case, the single estimation formula does not indicate the relationship between the bending angle and the elapsed time in inverse proportion.

Therefore, when the analysis is performed so that the relationship between the bending angle of the workpiece W and the elapsed time shows an approximately inversely proportional relationship, the analysis value is as shown in FIG. Therefore, in order to reduce the error in calculating the bending angle of the workpiece W by substituting the detection values of the strain sensors S1 to S4 into the estimation formula, the estimation formula is divided into a plurality of mode areas and is estimated for each mode area. As shown in FIG. In the estimation formula in each mode, (y) indicates an angle, and (X _{1 to} X ₄ ) indicate detection values of the strain sensors S1 to S4.

  The plurality of mode areas are divided into four areas from time zero to time T1 corresponding to time T, time T1 to T2, time T2 to T3, and time T3 to final time in the time axis direction. It is. These four regions correspond to four regions of 180 ° to about 165 °, about 165 ° to about 140 °, about 140 ° to about 99 °, and about 99 ° to the final angle in the bending angle direction. Note that the plurality of mode regions are not uniquely determined, and differ depending on conditions such as the shape and dimensions of the mold, such as the width of the V groove in the die 5 and the radius of the shoulder.

  With the above configuration, when the workpiece W is bent, the strain amount of the die 5 is detected by the strain sensors S1 to S4, and the detected values of the strain sensors S1 to S4 are substituted into the estimation formulas for each mode of modes 1 to 4. Thus, the bending angle of the workpiece W can be detected.

  By the way, when the workpiece W is bent by the punch 3 and the die 5, knowing the friction coefficient of the workpiece W is, for example, a position where the punch 3 projects into the V groove 5 V of the die 5 (from the bottom of the V groove 5 V 3 is important in calculating the size up to the tip of 3 and the d value) again and calculating the springback.

  Therefore, in order to obtain the friction coefficient of the workpiece W, the control means 9 for controlling the press brake 1 is provided with a database 15 as shown in FIG. The database 15 stores patterns of detection values of the strain sensors S1 to S4 when the workpiece W having various friction coefficients is bent. That is, the database 15 stores the data of each distortion pattern shown in FIG. Further, the database 15 stores estimation formulas corresponding to the modes 1, 2, 3, and 4 corresponding to the respective strain patterns due to the difference in the friction coefficient of the workpiece W.

  The control means 9 is further provided with a pattern comparison means 17. This pattern comparison means 17 is stored in the database 15 with an initial strain pattern (mode 1 strain pattern) of the die 5 detected by an appropriate number of strain sensors S1 to S4 among the strain sensors S1 to S4. Compared with the initial pattern (pattern in mode 1 before time T) of strain patterns at various friction coefficients, the same or approximate strain pattern is selected. That is, the pattern comparison unit 17 serves as an estimation formula determination unit for determining an estimation formula in each mode region by selecting a distortion pattern.

  When the strain pattern stored in the database 15 is selected by the pattern comparing means 17, the friction coefficient can be known from the selected strain pattern. That is, when a strain pattern is selected by the pattern comparing means 17, the friction coefficient of the workpiece W is calculated by the friction coefficient calculating means 19 provided in the control means 9.

  Further, as described above, since the distortion pattern to be applied to the workpiece W being bent is selected by the pattern comparison unit 17 and the estimation formula in each mode region is determined, the determined estimation formula and the distortion are determined. Based on the detected values of the strain amounts detected by the sensors S1 to S4, the bending angle of the workpiece W can be calculated by the angle calculation means 21 provided in the control device 9. In other words, the bending angle of the workpiece W can be known by detecting the amount of distortion of the die 5.

  Then, the bending angle of the workpiece W calculated by the angle calculating means 21 and the set value preset by the bending angle setting means 23 are compared by the comparison means 25 provided in the control means 9, and the comparison result is obtained. Based on the above, by performing feedback control of the drive means 7 by the drive shaft control means 27 provided in the control means 9, the workpiece W can be accurately bent at a desired bending angle.

  In the said structure, the bending angle of the workpiece | work W can be known by detecting the distortion amount of the die | dye 5 by distortion sensor S1-S4 embed | buried under the die | dye 5. FIG. Therefore, there is no need to provide a bending angle detector near or outside the die, and even if it is difficult to detect the bending angle of the workpiece from the outside of the die due to the shape and dimensions of the workpiece, The bending angle can be detected.

  Further, since the bending angle of the workpiece is detected by detecting the distortion of the die in a manner that takes into account the friction coefficient of the workpiece, the bending angle of the workpiece is also detected in consideration of the opening manner of the V groove 5V in the die 5. As a result, a more accurate bending angle can be detected, and the workpiece can be bent more accurately.

  By the way, since the distortion of the die can be directly detected, the allowable distortion amount of the die is set in advance, and the allowable distortion amount is compared with the detected distortion amount, thereby preventing the damage of the die. It is something that can be done.

It is action explanatory drawing which showed notionally the bending machine which concerns on embodiment of this invention. It is a block diagram which shows the structure of a control means. It is explanatory drawing of the distortion pattern which shows the detection aspect of the distortion sensor embed | buried under die | dye. It is explanatory drawing of the distortion pattern in case the friction coefficients of a workpiece | work differ. It is explanatory drawing which shows the distortion pattern by the detection of the some distortion sensor in case the friction coefficients of a workpiece | work differ. It is explanatory drawing of the single estimation formula which shows the relationship between an angle and elapsed time. It is explanatory drawing which shows the estimation formula in each mode area | region. It is explanatory drawing of the prior art which embeds several distortion sensors in die | dye and detects the bending angle of a workpiece | work.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bending machine 3 ... Punch 5 ... Die 5V ... V groove 5F ... Inclined surface 9 ... Control means 11 ... Sensor unit 15 ... Database 17 ... Pattern comparison means (estimation formula determination means)
19: Friction coefficient calculation means 21 ... Angle calculation means 23 ... Bending angle setting means 25 ... Comparison means 27 ... Drive shaft control means

Claims (4)

  When a plate-like workpiece is bent by a bending machine equipped with a punch and a die, the strain pattern of the die at the initial stage of bending is measured by a strain sensor provided on the die, and stored in a database in advance. A pattern estimation formula is determined by comparing the stored initial pattern of a plurality of strain patterns with the measured strain pattern, and a friction coefficient between the workpiece and the die is determined by the determined pattern estimation formula. A characteristic friction coefficient calculation method.   When a plate-like workpiece is bent by a bending machine equipped with a punch and a die, the strain pattern of the die at the initial stage of bending is measured by a strain sensor provided on the die, and stored in a database in advance. A pattern estimation formula is determined by comparing the stored initial pattern of the plurality of strain patterns with the measured strain pattern, and using the bending angle estimation formula corresponding to the determined pattern estimation formula, the strain sensor A bending angle detection method comprising calculating a bending angle of the workpiece based on a detection value.   A bending machine comprising a punch and a die for bending a plate-like workpiece, wherein the die includes a plurality of strain sensors for detecting distortion of the die when the workpiece is bent. A control means for controlling the bending machine, a database storing a plurality of strain patterns indicating a relationship between a workpiece folding time and a strain amount of the die; Estimating formula determining means for determining a pattern estimating formula by comparing the strain pattern of the die detected by each strain sensor at the initial stage of the bending process with the initial pattern of the strain pattern stored in the database, and determining the estimating formula And a calculating means for obtaining a friction coefficient between the workpiece and the die by a pattern estimation formula determined by the means. A bending machine comprising a punch and a die for bending a plate-like workpiece, wherein the die includes a plurality of strain sensors for detecting distortion of the die when the workpiece is bent. A control means for controlling the bending machine, a database storing a plurality of strain patterns indicating a relationship between a workpiece folding time and a strain amount of the die; Estimating formula determining means for determining a pattern estimating formula by comparing the strain pattern of the die detected by each strain sensor at the initial stage of bending with the initial pattern of the strain pattern stored in the database, and determining the estimating formula A bending process comprising: a pattern estimation formula determined by the means and a calculation means for calculating a bending angle of the workpiece based on a detection value of each of the strain sensors. .

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