JP4865489B2 - Molding speed determination method - Google Patents

Description

  The present invention relates to a method for determining a forming speed of a press working apparatus. Specifically, the present invention relates to a method for determining a forming speed in accordance with a strain distribution of a press-formed product.

Conventionally, it is known that the molding speed has a great influence on the quality of a molded product in press working. For this reason, in order to prevent cracks, wrinkles, dimensional accuracy defects and the like that occur in a molded product, a pressing method and a pressing apparatus that control a molding speed have been proposed (for example, see Patent Document 1). According to the pressing method and the pressing apparatus disclosed in Patent Document 1, the molding speed is controlled so that the ratio between the amount of movement of the upper mold and the amount of inflow of the material falls within a preset appropriate range. .
JP 2005-125355 A

  Incidentally, a molded product having a complicated shape such as a fuel tank of a motorcycle has a portion to be drawn and a portion to be stretched. These two moldings have different optimum molding speeds. Specifically, since the inflow of material increases when the molding speed is increased, it is preferable to press-mold the portion to be drawn at a higher molding speed. On the other hand, since the elongation of the material increases when the molding speed is slowed, it is preferable that the part to be stretch-molded is press-molded at a slow molding speed.

  That is, in press molding, it is necessary to appropriately adjust the molding speed depending on which of the draw molding and the stretch molding is dominant. However, the molding speed determination method as disclosed in Patent Document 1 cannot determine the molding speed for properly forming a molded product having such a complicated shape. Therefore, in such a case, the molding speed is often determined by the experience of the operator, and therefore it may take time to determine the molding speed.

  An object of the present invention is to provide a forming speed determination method capable of appropriately and quickly determining a forming speed of a press working apparatus.

  The forming speed determining method according to the present invention is a forming speed determining method for determining a forming speed of a press working apparatus, wherein a plurality of measurement points are provided on a plate material, and the plate material is pressed at a predetermined forming speed by the press working device. A strain distribution diagram plot for creating a strain distribution diagram by plotting a test press molding step for forming and a strain state at each measurement point of the press-formed plate material on a forming limit diagram including a forming limit line of the plate material When the specific measurement point is the one closest to the forming limit line among the points plotted in the process and the strain distribution diagram, and the specific measurement point is located in the overhang region, the forming speed is set to the predetermined forming point. And a molding speed determining step for making the molding speed faster than the predetermined molding speed when the specific measurement point is located in the throttle region.

Here, the overhang region is a region to be stretch-formed, and specifically, is a region where the maximum principal strain is positive and the minimum principal strain is also positive.
The drawn region is a region to be drawn, and specifically, a region where the maximum principal strain is positive and the minimum principal strain is negative.
According to the present invention, among the strain states at each measurement point of the press-formed plate material, the one closest to the forming limit line of this plate material is set as the specific measurement point, and when the specific measurement point belongs to the overhang region, Since the stretch molding is dominant in the molded product, the molding speed is decreased. Further, when the specific measurement point belongs to the drawing region, the forming speed is increased because the drawing is dominant in the formed product. That is, the molding speed is decreased or increased depending on whether the specific measurement point belongs to the overhang region or the narrowed region.
Therefore, compared with the case where the molding speed is determined based on the operator's intuition and experience as in the past, the molding speed of the press working device is appropriately set according to the material of the plate material and the shape of the molded product, and Decide quickly.

According to the present invention, among the strain states at each measurement point of the press-formed plate material, the one closest to the forming limit line of this plate material is set as the specific measurement point, and when the specific measurement point belongs to the overhang region, Since the stretch molding is dominant in the molded product, the molding speed is decreased. Further, when the specific measurement point belongs to the drawing region, the forming speed is increased because the drawing is dominant in the formed product. That is, the molding speed is decreased or increased depending on whether the specific measurement point belongs to the overhang region or the narrowed region.
Therefore, compared with the case where the molding speed is determined based on the operator's intuition and experience as in the past, the molding speed of the press working device is appropriately set according to the material of the plate material and the shape of the molded product, and Decide quickly.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing a configuration of a press working apparatus 10 according to an embodiment of the present invention.
The press working apparatus 10 includes a lower mold mechanism 20 having a lower mold 52 disposed on the lower side of the steel plate 12, an upper mold mechanism 18 that moves the upper mold 38 toward and away from the lower mold 52, and these lower mold mechanisms. 20 and a control unit 16 for controlling the upper mold mechanism 18.

  The upper mold mechanism 18 is supported by a servo motor 24, a rotating plate 28 that is rotationally driven by the servo motor 24 via a reduction gear (not shown), and an upper end of the rotating plate 28 that is pivotally supported on the side surface of the rotating plate 28. Connecting rod 30.

  The servo motor 24 is, for example, an AC type, and has high responsiveness and small torque unevenness. The shaft rotation position of the servo motor 24 is detected by an encoder (not shown), and the servo motor is feedback-controlled based on the detected shaft rotation position.

  The upper die mechanism 18 further detects a position of the slider 32 supported by the lower end of the connecting rod 30, a guide (not shown) for guiding the slider 32 in the vertical direction, and a signal to the control unit 16. A first linear sensor 36 to be supplied and an upper die 38 provided on the lower surface of the slider 32 are provided.

  The upper mold 38 is press-molded with the lower mold 52 sandwiching the steel plate 12, and a mold surface 38 a for contacting the upper surface of the steel plate 12 is provided on the lower surface thereof. Also. An annular holder 40 slightly protrudes around the upper mold 38. Therefore, the holder 40 comes into contact with the steel plate 12 ahead of the mold surface 38a. The front end surface of the holder 40 is set to a horizontal plane.

  The lower mold mechanism 20 includes a fixed base 50 that serves as a base, a lower mold 52 provided on the upper part of the fixed base 50, an annular blank holder 54 that supports the periphery of the steel plate 12, and the blank holder 54 that moves up and down. A die cushion mechanism 56.

  The lower die 52 is press-formed with the steel plate 12 sandwiched with the upper die 38, and a die surface 52a for contacting the lower surface of the steel plate 12 is provided on the upper surface thereof. The mold surface 52 a is formed in a shape corresponding to the mold surface 38 a of the upper mold 38.

  The blank holder 54 is provided at a position facing the holder 40 and sandwiches the end portion of the steel plate 12 together with the holder 40 in order to prevent wrinkles and displacement when the steel plate 12 is pressed.

  The die cushion mechanism 56 includes a holder support portion (not shown) that supports the blank holder 54 and a hydraulic lift mechanism (not shown) that raises and lowers the holder support portion. The die cushion mechanism 56 further includes a servo motor (not shown) that drives the lifting mechanism and a second linear sensor (not shown) that detects the position of the holder support and supplies a signal to the controller 16. The servo motor of the die cushion mechanism 56 is connected to the control unit 16, thereby pressing the peripheral part of the steel plate 12 with an appropriate pressure by the blank holder 54 together with the holder 40 while performing predetermined pressure control. And can be used to suppress wrinkles.

  The control unit 16 slides the slider 32 up and down by driving the servo motor 24 while referring to signals supplied from the encoder connected to the servo motor 24 and the first linear sensor 36. Further, the control unit 16 raises and lowers the blank holder 54 by driving a servo motor of the die cushion mechanism 56 while referring to a signal supplied from the second linear sensor of the die cushion mechanism 56.

  Next, a method of processing the steel plate 12 as a workpiece using the press working apparatus 10 configured as described above will be described with reference to the flowchart of FIG.

First, in step S1, initial setting is performed. That is, the blank holder 54 is raised to a predetermined position, and the blank steel plate 12 is supported by the blank holder 54. The slider 32 is the top dead center (see, for example, the displacement x ₁ of FIG. 9) allowed to rise up.

  In step S2, under the action of the control unit 16, the servo motor 24 is rotationally driven to lower the slider 32.

When is a certain downward, the holder 40 contacts the upper surface of the steel plate 12, the steel plate 12 is held between the holder 40 and the blank holder 54 (see, for example, the displacement x ₂ in Figure 9). From this point, the control unit 16 lowers the slider 32 together with the blank holder 54 at a molding speed set in advance by a molding speed determination method described in detail later (step S3).

Here, the control unit 16 performs pressure control so that the blank holder 54 moves downward while generating an appropriate force so that the lower surface of the steel plate 12 is pressed and holds the steel plate 12 securely. That is, the blank holder 54 is pressed through the steel plate 12 by the holder 40 and is pressed down while applying an appropriate pressure to the steel plate 12.
As a result, the steel plate 12 is lowered at the set forming speed while the peripheral portion is held by the holder 40 and the blank holder 54, and is gradually pressed into the product shape by the upper die 38 and the lower die 52.

In step S4, the control unit 16, the position of the first with reference to a signal of the linear sensor 36 the slider 32 checks whether it has reached the bottom dead center (for example, see the displacement x ₃ in FIG. 9). When the slider 32 reaches the bottom dead center, the process proceeds to step S5, and when it does not reach, the descent continues.

In step S <b> 5, the servo motor 24 is rotationally driven under the action of the control unit 16 to raise the slider 32.
In step S6, the blank holder 54 is raised to the panel transport position under the action of the control unit 16.

  In step S7, the pressed steel plate 12 placed on the blank holder 54 is transported to a next process station by a predetermined transport means.

  In step S8, the control unit 16 raises the blank holder 54 again, causes the blank holder 54 to reach the processing standby position, and places the unprocessed steel plate 12 at a predetermined position. During this time, the slider 32 continues to rise.

In step S9, the control unit 16, the position of the first with reference to a signal of the linear sensor 36 the slider 32 checks whether it has reached the top dead center (see, for example, the displacement x ₁ of FIG. 9). When the slider 32 has not reached the top dead center, the ascent is continued. When the slider 32 has reached the top dead center, the processing of the steel plate 12 is finished.

  In the press working apparatus 10 as described above, when a steel plate (plate material) is press-formed, the strain state of the steel plate varies depending on the measurement point. Therefore, a strain distribution diagram showing the strain state at each measurement point of the steel sheet as a point on the forming limit diagram of the steel sheet is used.

FIG. 3 is a strain distribution diagram showing the deformation state of the molded product in the forming limit diagram of the steel sheet. Specifically, in FIG. 3, the horizontal axis is the maximum principal strain ε ₁ (≧ 0) in the in-plane direction of the steel sheet, the vertical axis is the minimum principal strain ε ₂ in the in-plane direction of the steel sheet, and this ε ₁ −ε It is the figure which plotted the distortion state (deformation state) in each measurement point of a press-molded product on ₂ coordinates.

In the strain distribution diagram of FIG. 3, a line (ε ₂ = ε ₁ ) extending from the origin O to the upper right represents equal biaxial tension. By this equal biaxial tension (ε ₂ = ε ₁ ), the steel sheet is stretched to a shape substantially similar to that before forming. This equibiaxial tension corresponds to, for example, the deformation state of the bottom of the deep-drawn container.

A line (ε ₂ = 0) extending rightward from the origin O represents plane strain tension. By this plane strain tension (ε ₂ = 0), the steel sheet is stretched along the height direction (direction along ε ₁ ) without changing the dimension along the width direction (direction along ε ₂ ). It becomes. This plane strain tension corresponds to, for example, a bent portion of a wide steel plate or a deformed state near the shoulder-side wall boundary of a deep drawn container.

A line extending from the origin O to the lower right (ε ₂ = −0.5ε ₁ ) represents uniaxial tension. By this uniaxial tension (ε ₂ = −0.5ε ₁ ), the steel sheet is squeezed along the width direction (direction along ε ₂ ) and stretched along the height direction (direction along ε ₁ ). Will be. That is, uniaxial tension corresponds to a deformed state pulled in a uniaxial direction.

Further, a forming limit line FL of the steel plate is indicated by a broken line in FIG. This forming limit line FL is obtained by measuring the breaking strain by changing the strain ratio ε ₂ / ε ₁ in the plate surface and plotting it on the ε ₁ -ε ₂ coordinates. Depends on etc. That is, the forming limit line FL indicates how the forming limit varies depending on the forming method of the steel sheet.
Further, here, in the ε ₁ -ε ₂ coordinates, the region of ε ₂ > 0 indicates a stretched region where the steel sheet is stretched, and the region of ε ₂ ≦ 0 indicates the stretched region of the stretch formed. Show.

Next, the relationship between the molding method and the molding speed in the press working apparatus 10 as described above will be described with reference to FIGS.
FIG. 4 is a graph showing the relationship between the forming speed of the press working apparatus 10 and the elongation of the press-formed steel sheet.
As shown in FIG. 4, the elongation of the steel sheet decreases as the forming speed increases. In other words, in the case of stretch forming in which the elongation of the steel plate has a great influence on the forming limit, the reduction rate of the thickness of the formed portion decreases as the forming speed decreases, so that the forming speed of the press working apparatus 10 is slower. preferable.

FIG. 5 is a graph showing the relationship between the forming speed of the press working device 10 and the coefficient of friction between the steel plate and the mold, and FIG. 6 shows the relationship between the forming speed of the press working device 10 and the inflow amount of the steel plate. It is a graph.
As shown in FIG. 5, the coefficient of friction between the steel plate and the die of the press working apparatus 10 decreases as the molding speed of the press working apparatus 10 increases. As a result, as shown in FIG. 6, the inflow amount of the steel plate increases as the forming speed increases. That is, in the case of draw forming in which the inflow amount of the steel plate greatly affects the forming limit, the plate thickness reduction rate of the formed portion decreases as the forming speed increases, so the forming speed of the press working apparatus 10 is the faster one. Is preferred.
Further, since the influence of friction increases as the surface pressure increases, as shown in FIG. 6, the inflow amount of the steel sheet increases more remarkably when the surface pressure is large than when the surface pressure is small. .

In the press working apparatus 10 as described above, the procedure for determining the molding speed will be described with reference to FIGS.
FIG. 7 is a perspective view showing the steel plate 80 before press forming. FIG. 8 is a perspective view showing a fuel tank 90 of a motorcycle formed by press-forming the steel plate 80 with the press working apparatus 10. FIG. 9 is a diagram illustrating the displacement of the slider 32 in one cycle of the press working apparatus 10. Hereinafter, a method for determining the molding speed of the press working apparatus 10 will be described by taking as an example the case of press molding a fuel tank 90 of a motorcycle as shown in FIG.

  The molding speed determination method for determining the molding speed of the press working apparatus 10 includes three processes: a test press molding process, a strain distribution diagram plotting process, and a molding speed determination process.

In the test press forming step, press forming is performed on the steel plate 80 provided with the measurement points by the press processing apparatus 10 at a predetermined forming speed.
Specifically, first, as shown in FIG. 7, a plurality of mesh-like measurement points P _{1 to} P _N are provided on the steel plate 80, and this is a test piece for determining the forming speed of the press working apparatus 10. And Next, this steel plate 80 is press-formed by the above-described press working apparatus 10 to form a fuel tank 90 for a motorcycle as shown in FIG. The fuel tank 90 formed in this way is substantially box-shaped as shown in FIG. 8, and includes both an overhang-formed portion 91 and a draw-formed portion 92.

Here, in this test press molding process, the slider 32, for example, performing press molding is controlled at such a rate as indicated by the solid line D ₀ in FIG. That is, the above-mentioned predetermined molding speed, 9, slider 32 reaches the displacement x _{3 (bottom} dead center) from the displacement x _{2 (position} the mold surface 38a of the upper die 38 comes into contact with the steel plate 12) This is the speed of the slider 32 in the section up to this, and this is the test molding speed.

In the strain distribution diagram plotting step, the strain at the measurement points P _{1 to} P _N of the steel plate 80 press-formed in the test press forming step is measured, and this is plotted on the forming limit diagram of the steel plate 80 to obtain a strain distribution diagram. Create
Specifically, the strain state at each of the measurement points P _{1 to} P _N of the fuel tank 90, that is, ε ₁ and ε ₂ is measured, and these strain states are further determined as the forming limit provided with the forming limit line FL of the steel plate 80. Plot on a diagram to create a strain distribution diagram as shown in FIG. Here, points Q _{1 to} Q _N in FIG. 3 indicate strain states at the measurement points P _{1 to} P _N of the steel plate 80, respectively.

In the forming speed determining step, the forming speed is determined by adjusting the test forming speed set in the test press forming step based on the strain distribution diagram created in the strain distribution diagram plotting step.
Specifically, first, among the points Q _{1 to} Q _{N in} the strain distribution diagram, the _one belonging to the overhang region (ε ₂ > 0) and closest to the forming limit line FL is specified. Next, among the points Q _{1 to} Q _{N in} the strain distribution diagram, the _one belonging to the drawing region (ε ₂ ≦ 0) and closest to the forming limit line FL is specified. According to the example of the strain distribution diagram shown in FIG. 3, the point Q _A and the point Q _B are specified as being closest to the forming limit line FL. Further, here, the points Q _A and Q _B in the strain distribution diagram respectively correspond to the strain states at the measurement points P _A and P _B in the fuel tank 90 of FIG.

Next, among these points Q _A and Q _B , the one closest to the forming limit line FL is set as a specific measurement point. According to the example of the strain distribution chart shown in FIG. 3, the point Q _A, is close to the forming limit line FL of the point Q _B, the point Q _A is the specific measurement point.
Here, since the point Q _{A set} as the specific measurement point is closest to the forming limit line FL of the steel plate 80, the measurement point P _A corresponding to this point Q _A in the formed fuel tank 90 is the molded product. It can be said that the most attention must be paid to improve quality.

That is, in the example shown in FIG. 3, since such a measurement point A belongs to the overhang region (ε ₂ > 0) in the strain distribution diagram, it can be said that the overhang forming is dominant in the fuel tank 90. That is, in the fuel tank 90 where the overhang forming is dominant, it is desired to adjust the forming speed so that the overhang forming is performed smoothly.

Next, in the strain distribution diagram, when the specific measurement point is located in the overhang region (ε ₂ > 0), the molding speed of the press working apparatus 10 is made slower than the test molding speed. In addition, when the specific measurement point is located in the drawing region (ε ₂ ≦ 0), the molding speed of the press working apparatus 10 is set higher than the test molding speed.

Specifically, when the specific measurement point is located in the overhang region (ε ₂ > 0), as shown in the broken line D ₁ in FIG. The molding speed of the press working apparatus 10 is set slower than the test molding speed.
Further, when located in the throttle region specific measurement point (ε ₂ ≦ 0), for performing smooth a dominant-drawn in the fuel tank 90, as indicated by the broken line D ₂ in Figure 9, pressing The molding speed of the apparatus 10 is set faster than the test molding speed.

According to the example of the strain distribution diagram shown in FIG. 3, since the measurement point A (specific measurement point) is located in the overhang region (ε ₂ > 0), the forming speed is as shown by a broken line D ₁ in FIG. And slower than the test molding speed (solid line D ₀ ).

According to the present embodiment, there are the following effects.
Among the strain states Q _{1 to} Q _{N at} the measurement points P _{1 to} P _N of the press-formed steel plate 80, the one closest to the forming limit line FL of the steel plate 80 is set as a specific measurement point, and this specific measurement point is projected. In the case of belonging to the region (ε ₂ > 0), it is assumed that the overhang molding is dominant in the molded product (fuel tank 90), and the molding speed is reduced. Further, when the specific measurement point belongs to the drawing region (ε ₂ ≦ 0), the drawing speed is increased on the assumption that the drawing is dominant in the formed product. That is, the molding speed is decreased or increased depending on whether the specific measurement point belongs to the overhang region or the narrowed region.
Therefore, compared with the case where the forming speed is determined based on the operator's intuition and experience as in the prior art, the forming speed of the press working apparatus 10 is appropriately set according to the material of the steel plate 80 and the shape of the formed product, And it can be determined quickly.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

It is a schematic diagram which shows the structure of the press work apparatus which concerns on this Embodiment. It is a flowchart which shows the procedure of the press work method by a press work apparatus. It is the distortion distribution figure which showed the distortion state of the molded article in the forming limit diagram of a steel plate. It is a graph which shows the relationship between the shaping | molding speed of a press work apparatus, and the elongation of a steel plate. It is a graph which shows the relationship between the shaping | molding speed of a press work apparatus, and the friction coefficient between a steel plate and a metal mold | die. It is a graph which shows the relationship between the shaping | molding speed of a press work apparatus, and the inflow of a steel plate. It is a perspective view which shows the steel plate before press molding. 1 is a perspective view showing a fuel tank of a motorcycle formed by press forming a steel plate. It is a graph which shows the displacement of the slider in 1 cycle of a press work apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Press processing apparatus 12 ... Steel plate 18 ... Upper die mechanism 32 ... Slider 38 ... Upper die 20 ... Lower die mechanism 52 ... Lower die 56 ... Die cushion mechanism 80 ... Steel plate 90 ... Fuel tank 91 ... Overhang molded part 92 ... Draw molded part

Claims (1)

A molding speed determination method for determining a molding speed of a press working apparatus,
A test press molding process in which a plurality of measurement points are provided on the plate material, and the plate material is press-molded at a predetermined molding speed by the press processing device,
The line obtained by plotting the fracture strain points for each ratio of the maximum principal strain and the minimum principal strain on the two-dimensional coordinates based on the maximum principal strain and the minimum principal strain is defined as the forming limit line, and the two-dimensional coordinates The one provided with the molding limit line of the plate material used in the test press molding process is defined as a molding limit diagram, and the maximum principal strain and the minimum principal strain at each measurement point of the press-molded plate material are measured. and strain distribution plot step of creating a strain distribution diagram by plotting the maximum principal strain and the minimum principal strain at each measuring point on the forming limit diagram,
Of the points plotted in the strain distribution diagram, the one closest to the molding limit line is defined as a specific measurement point, and when the minimum principal strain at the specific measurement point is positive, the molding speed is set to the predetermined molding speed. And a molding speed determining step for making the molding speed faster than the predetermined molding speed when the minimum principal strain at the specific measurement point is 0 or negative. Molding speed determination method.

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