JP2015150573A - Preliminary forming method and preliminary forming device of material to be processed used in press forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preliminary forming method and device which decrease a plate thickness of a central part of material to be processed used in press forming and, at the same time, form a shape.SOLUTION: A preliminary forming method includes a process (c) in which pressing rollers 11, 14, extension rollers 12, 15 and shaping rollers 13 are moved in the substantial plate thickness direction of material W to be processed and at least a part is formed and a process (d) in which the pressing roller 11 is fastened and applies tension to the material W to be processed, the pressing roller 11, the extension rollers 12, 15 and the shaping roller 13 maintain the relative positional relation, at the same time, are moved in substantially parallel to the material W to be processed and form the residue shape and, at the same time, the extension roller 12 comes into pressing contact with the material W to be processed from one side, bends and extends the material W to be processed and the shaping roller 13 comes into contact with the bent material W to be processed from the other side and unbends the bent material W to be processed into a substantially flat plane shape. According to the preliminary forming method, material yield is improved and the contribution to reduction of material expense is permitted.

Description

  The present invention relates to a preforming method and a preforming apparatus suitable for preforming a plate-like workpiece used for press molding.

  A press molding method is usually used for molding a relatively large metal plate material, for example, a sheet metal part constituting a body of an automobile or the like. Press molding requires manufacturing time and cost because it is necessary to manufacture a large mold, but manufacturing efficiency is good because a wide range of products can be molded at once. However, in press molding, the length of the work material is large and the thickness is locally thin on the vertical wall (product side surface) around the work material gripping part, and the shape of the door inner panel and rear floor panel is particularly complicated. In some cases or when the aperture is deep, cracks and wrinkles may occur. For this reason, the depth of the product is limited, and the degree of freedom in design is reduced. It is necessary to consider the appropriate amount of material inflow by adjusting the position and length of the squeeze bead. As a result, since the material for the outside of the product is allowed to flow, the yield of the material is deteriorated.

  In order to improve the material yield by ordinary drawing press forming, it is general to devise a wrinkle holding method. For example, Patent Document 1 discloses a method and an apparatus for preventing cracks and wrinkles while improving the material yield by carrying out wrinkle pressing in two stages by ordinary deep drawing using a press. However, even though the amount of elongation of the product side surface can be adjusted by this method, the portion that occupies the majority of the entire product area, that is, the central portion of the plate cannot be stretched on average, so the effect is limited. is there.

  If rolling is used, the entire plate can be stretched uniformly, but if the product shape is pressed using the rolled plate, the plate on the side of the product that has already been thinned will be stretched further. As a result, the amount of drawing after rolling is less than that before rolling. In addition, since it is necessary to generate a very large force for rolling, the equipment becomes large. Moreover, a three-dimensional shape cannot be simultaneously formed by rolling.

  Patent Document 2 describes a method and apparatus for forming a metal plate material into a three-dimensional shape using roll forming instead of press forming. By changing the relative positions of the plurality of molding rolls during molding, cross-sectional shapes having various curvatures can be molded. Local molding is repeated using a relatively small molding roll, which is effective for relatively small products with complex three-dimensional shapes, but it takes a very long time to complete the overall shape of a large product. Take it. Therefore, it is not suitable for pre-forming of press molding that requires a large area shape to be formed in a short time.

JP 2009-160591 A JP 2010-240712 A

  In this way, with the conventional drawing press molding technology, there is no means other than adjusting the amount of elongation of the product side surface and the material inflow from the outside of the product, and the overall product cannot be stretched on average, so the yield improvement margin is small. Even if other molding techniques are used, it is difficult to average the plate-like workpiece central portion used for press molding and at the same time perform the preliminary molding in a short time.

  The present invention has been made in view of the above problems, and in order to improve the material yield in press molding, a preforming method and apparatus for reducing the thickness of the central part of the workpiece and simultaneously molding the shape. The purpose is to provide.

  As a result of extensive research and trial and error, the present inventor has conducted bending and stretching with two bar-shaped rolls while applying tension to the plate-shaped workpiece, and further bending the workpiece. It is considered that the center part of the workpiece can be extended on the average by reducing the thickness, and the plate thickness can be reduced, and this idea has been embodied and developed to complete the present invention described below.

  The preforming method for press molding according to the present invention is at least one for forming a workpiece and applying tension to the workpiece, which is in contact with one or both sides of a plate-like workpiece used for press molding. A bar-shaped presser roll, at least one bar-shaped spreading roll that is press-contacted to the workpiece, and is bent and stretched, and is bent back into a substantially flat shape in contact with the bent workpiece. At least one rod-shaped shaping roll that is initially arranged in parallel to each other, and the presser roll, the spreading roll, and the shaping roll move in a substantially plate thickness direction of the workpiece to form at least a part of the shape The presser roll is fixed and tension is applied to the workpiece, and the stretch roll and the shaping roll move in a direction substantially parallel to the workpiece while maintaining a relative positional relationship. The remaining shape is molded at the same time as the expansion While the tool is moved in advance, the workpiece is pressed against the workpiece from one side to bend and extend, and the shaping roll is subsequently moved and brought into contact with the bent workpiece from the other side. And a step of bending back to a substantially planar shape.

  According to the preforming method according to the present invention, for example, when a box-shaped shape is formed using three rolls, the three rolls are maintained in a substantially vertical direction with respect to the workpiece while maintaining the relative positional relationship. The workpiece is moved to a predetermined position to deform the workpiece, and a part of the box shape is formed. Thereafter, the presser roll is fixed in place and applies tension to the workpiece. The remaining spreading roll and shaping roll move to a predetermined position in a direction substantially parallel to the workpiece before deformation while maintaining a relative positional relationship, and form a box-shaped hollow bottom. At that time, the preceding spreading roll is pressed in the thickness direction of the workpiece, the workpiece is bent along the outer peripheral surface of the spreading roll to reduce the thickness, and the subsequent shaping roll is bent. Then, contact is made from the opposite side of the workpiece and bent back into a substantially flat shape for shaping. In this way, a box shape having a predetermined depth can be formed, and at the same time, the plate thickness at the center of the workpiece can be reduced.

  By using the work material formed into a box shape by such a preforming method, the amount of material inflow can be reduced compared to the conventional drawing press forming technology, and therefore, when forming by conventional drawing press forming In the case of forming a shape having the same depth, the material yield is improved, and in the case of the same material yield as that of the conventional drawing press forming, the forming depth can be increased. Further, compared with sequential molding in which local molding is repeated as described in Patent Document 2, the amount of movement of the roll is small, and molding is completed in a short time. Furthermore, there is an advantage that the plate thickness of the side surface portion of the product is not reduced as compared with the conventional drawing press molding.

It is the front view which showed the structure of the preforming apparatus. It is the side view which showed the structure of the preforming apparatus. It is the front view which showed the structure of the roll holding tool. It is sectional drawing which showed the holding structure of a roll holding tool and a roll. It is explanatory drawing which showed the preforming process. It is a plane photograph of the workpiece after forming. It is a graph which shows the shaping | molding shape and board thickness distribution in one cross section of the workpiece after shaping | molding.

≪Roll≫
The roll according to the present invention has four different functions. The first function is a function of forming a plate-like workpiece into a predetermined shape. The second function is a function of pressing the workpiece, bending and stretching the workpiece along the outer peripheral surface of the roll, and reducing the plate thickness. The roll having this function is the stretch roll. The third function is a function of contacting and bending back from the opposite side the workpiece that has been plastically deformed and bent by the extension roll, and shaping it into a substantially flat shape. The roll having this function is a shaping roll. . The fourth function is a function of applying tension to the work material in order to effectively perform bending and stretching and bending back of the work material. A roll having this function is a presser roll. It is. That is, in order to achieve the object according to the present invention, at least three rolls having these four functions are required.

  Here, with regard to the arrangement and movement path of the three required rolls, the minimum required number of rolls will be described in the case where the workpieces are arranged horizontally and the box-shaped recess shape is formed on the upper side. As the initial position, presser roll, shaping roll, and spreading roll are arranged in parallel in the order from the side closer to the workpiece one side end, the holding roll and spreading roll are under the workpiece, and the shaping roll is Arranged parallel to the workpiece on the upper side. As the first step, all three rolls start to move substantially upward in the plate thickness direction of the workpiece, and move until a part of the box shape with a predetermined depth is formed. The stretch roll and the shaping roll are preferably moved in the same direction while maintaining a close relative positional relationship, but the presser roll may be moved at an arbitrary angle different from them.

  As the next step, the stretch roll and shaping roll move in the horizontal direction while maintaining the relative positional relationship to form a box-shaped hollow bottom, and at the same time reduce the plate thickness by bending and stretching back with the roll. . On the other hand, the position of the presser roll is fixed in place, and tension is applied to the workpiece in the direction opposite to the moving direction of the spreading roll and the shaping roll. The entire forming process is completed when the spreading roll and the shaping roll are moved to predetermined positions to complete the box shape.

  In order to effectively perform the bending and stretching and bending back processes, a presser roll may be further added. As the number of rolls increases, the tension applied to the workpiece increases, so the effect of reducing the plate thickness also improves. For example, by placing a presser roll in front of the above-described stretch roll in the moving direction, tension can be applied to the workpiece from both sides, and bending and stretching and bending back between two presser rolls are performed. The effect can be enhanced. Further, the number of spreading rolls and shaping rolls can be increased as appropriate. The plate thickness of the workpiece can be reduced stepwise by a plurality of bending and bending operations. That is, the number of rolls according to the present invention can be appropriately changed in consideration of the material of the workpiece, the desired plate thickness reduction rate, the forming accuracy of preforming, the size of equipment, and the like. Also, dimensions such as the outer diameter and length of each roll can be appropriately changed in consideration of the outer dimensions of the workpiece or product, the size of the equipment, and the like. For example, a large outer diameter roll is used as the presser roll, and tension is stably applied to the workpiece, while a small outer diameter roll may be used as the spreading roll and the shaping roll. When there are a plurality of rolls and shaping rolls, the outer diameter of each roll can be appropriately changed according to the change in the plate thickness of the workpiece.

  The roll according to the present invention is gripped by a mechanism capable of free rotation in order to reduce the frictional force with the workpiece. In addition, since the workpiece according to the present invention is gripped on the outer periphery by a workpiece gripping tool described later, stress is concentrated at both ends of the roll when the roll is pressed against the workpiece and the shape is formed. Thus, it is a place where abrupt shape deformation or breakage is likely to occur. Therefore, it is desirable that both end portions of the roll are hemispherical having a smooth curvature with the outer diameter gradually reduced. However, since the circumferential length is different between the roll center portion and both end portions having different outer diameters, the frictional force at both end portions is increased. In order to solve this problem, the rotation speed can be changed for each part by dividing the central portion and both end portions. The greater the number of divisions at the roll end, the lower the frictional force.

≪Roll drive means≫
The roll driving means according to the present invention is means for moving the roll in the vertical direction (workpiece plate thickness direction) and the horizontal direction (workpiece parallel direction), a power source for generating power such as a motor, And a drive shaft that moves the roll by transmitting the power generated by the power source in the linear direction. The power source and the drive shaft are required in at least the vertical direction and the horizontal direction, respectively. Moreover, when each roll moves differently, a power source and a drive shaft can be suitably added as needed.

≪Roll gripper≫
The roll gripping tool according to the present invention is connected to the end of the drive shaft, efficiently transmits a force for forming a workpiece from the drive shaft to the roll, and grips the roll so as to be freely rotatable. The position where the roll is gripped is a position where the force is evenly transmitted to the inner side of the roll and the entire roll so as not to impair the effect of the hemispherical shape having the smooth curvature at the end of the roll. It is desirable to be. When a part of the roll gripper comes into contact with the workpiece, it is desirable for the contact surface to be freely rotatable in order to suppress frictional resistance. For example, it is preferable to interpose a bearing on the sliding surface between the freely rotating roll and the non-rotating roll gripper. In addition, a frictional resistance can be reduced by forming a thin plate made of a material capable of withstanding pressure contact on the surface where the roll gripper comes into contact with the workpiece and sandwiching it between the contact surfaces in a configuration allowing free rotation.

≪Workpiece gripper≫
The workpiece gripping portion according to the present invention grips the outer periphery so that the workpiece does not flow. By firmly restraining the workpiece, tension can be applied to the workpiece, and the thickness reduction effect is enhanced.

≪Others≫
The preforming apparatus according to the present invention includes a control unit that moves a roll along a predetermined movement path in order to form a shape. Numerical data such as position coordinates and time required for control are set in the control unit in advance. The control unit may be incorporated in the main body of the preforming apparatus, or may be provided alone so that it can be remotely operated from a location away from the apparatus. In addition, by applying a lubricant to the contact surface between the roll and the workpiece, or by sandwiching a thin elastic sheet such as polyurethane resin or synthetic rubber, the movement trace of the roll attached to the workpiece can be made inconspicuous. .

  Embodiments according to the present invention will be described in detail. The present embodiment is an example of a preforming apparatus used when a box shape is formed as a preform before press molding of an automobile door inner panel.

≪Preliminary molding equipment≫
First, the overall configuration of the preforming apparatus will be described. FIG. 1 is a front view showing a configuration of a preforming apparatus according to the present invention, and FIG. 2 is a side view thereof. For convenience, the rotation axis direction of the roll 1 is the X axis, the horizontal direction perpendicular to the X axis is the Y axis, and the vertical direction is the Z axis. The preforming apparatus S performs a total of 10 sets of Z-axis movement, including a main body frame F, a workpiece gripping pallet P, five rolls 1, and five roll gripping tools 2 connected to each roll 1. A set of Z-axis motor 4 and Z-axis screw 3 to enable, a set of Y-axis motor 6 and Y-axis screw 5 to enable a total of 10 sets of Y-axis movement, and a control for controlling the movement path of each roll, etc. Part C is provided. Each roll is provided with two sets of a Z-axis motor 4 and a set of Z-axis screws 3, and two sets of a Y-axis motor 6 and a set of Y-axis screws 5. 1 and 2, a part of the Y-axis motor and the Y-axis screw are omitted. Information such as time and coordinates necessary for controlling the movement of each tool can be input to the control unit C, and these are defined in a table format.

  The main body frame F is provided with all the components except the control unit C, and forms a skeleton that supports a load when the workpiece is molded. A workpiece gripping pallet P having a workpiece gripping tool is disposed at the center of the preforming device S, and has a mechanism that can slide in the Y-axis direction so that the workpiece can be easily replaced. To replace the workpiece, pull the workpiece gripping pallet P from the main body frame F, attach the workpiece, grip the outer periphery of the workpiece with the workpiece gripper, and then grip the workpiece again. The pallet P is fried inside the main body frame F and fixed. Two rolls 1 are arranged above the workpiece gripping pallet P, and three rolls 1 are arranged parallel to the X axis below the workpiece gripping pallet P. Is arranged in. A Z-axis motor 4 that generates power for moving the roll 1 in the Z-axis direction and a Z-axis screw 3 that transmits the power in the Z-axis direction are provided in each roll 1 and connected via a roll gripper 2. In addition, two sets of Y-axis motor 4 for generating power for moving roll 1 in the Y-axis direction and Z-axis screws 3 for transmitting power in the Y-axis direction are provided above and below workpiece gripping pallet P, respectively. .

≪Roll gripper≫
Next, the configuration of the roll gripper 2 will be described in detail. FIG. 3 is a front view illustrating the configuration of the roll 1 and the roll gripper 2. The roll gripping tool 2 grips the roll 1 at two locations. FIG. 4 is a cross-sectional view showing the configuration of the gripping portion at one place. The roll 1 is composed of three parts, ie, a roll 1b at the center, a roll 1a at both ends, and a roll 1c, each of which can independently rotate freely. The roll 1b has a cylindrical shape with the same outer diameter, while the roll 1a and the roll 1c have a hemispherical shape having a smooth curvature with the roll outer diameter gradually reduced. As shown in FIG. 4, the inside of the roll 1 has a concave shape hollowed out in a cylindrical shape concentric with the roll rotation center, and the roll gripping tool 2 has a cylindrical convex shape. By combining the concave shape portion of the roll 1 and the convex shape portion of the roll gripping tool 2 via the bearing B, the roll gripping tool 2 grips the roll 1 so as to be freely rotatable. Further, a frictional resistance is reduced by sandwiching a freely rotatable annular steel belt SB between the contact surfaces of the roll gripping tool 2 and the workpiece W.

≪Molding process≫
Next, the molding process will be described in detail. FIG. 5 is a diagram illustrating the molding process. (a) shows the initial arrangement | positioning of the roll before a shaping | molding process start. (b) shows a state in which only the spreading roll 12 is pressed in the thickness direction (Z-axis positive direction) of the workpiece W. Thereafter, in the step (c), all the rolls are moved to an arbitrary position while maintaining the relative positional relationship in the positive direction of the Z axis, and a part of the box-shaped indented portion is formed. In the step (d), the remaining portion of the box shape is formed and at the same time the plate thickness is reduced. Here, the movement and function of each roll will be described. First, the presser roll 11 stays at the position moved in the step (c), and applies tension to the workpiece W. The remaining roll is moved to an arbitrary position while maintaining the relative positional relationship in the positive direction of the Y-axis, and the plate thickness of the workpiece W is bent and stretched and bent back while forming the box-shaped hollow bottom. To do. Specifically, the presser roll 14 further applies tension while forming the box-shaped hollow bottom surface of the workpiece W at the foremost position in the movement direction. The spreading roll 12 is always pressed in the vertical direction of the workpiece W, and the workpiece W is locally bent and plastically deformed to stretch. The subsequent shaping roll 13 is bent back in contact with the workpiece W bent by the spreading roll 12 from the opposite side, and shaped into a substantially flat shape. In order to enhance the bending effect of the extension roll 12, the extension roll 15 supplementarily bends the workpiece W so as to follow the outer peripheral surface of the extension roll 12. In this way, all the steps of forming the box shape and reducing the thickness of the central portion of the workpiece W are completed.

≪Evaluation≫
The workpiece used for press molding was preformed using the preforming apparatus of this example, and a workpiece after preforming as shown in FIG. 6 was obtained. As can be seen from the graph of FIG. 7, the workpiece was formed into a box shape, and the workpiece that was 0.4 mm before processing was 0.36 mm at the thinnest part, The rate of decrease has approached 10% over a wide area in the center. Moreover, the plate | board thickness of the side part which was the subject in the conventional drawing press molding is thicker than the center part. Thus, it was confirmed that the plate thickness at the central portion of the workpiece can be reduced substantially uniformly by simultaneously forming the workpiece used for press molding into a box shape by the preforming method and apparatus according to the present invention. In addition, since the work material is preformed, the work material can be gripped more strongly during the drawing press forming that is the final forming, and the amount of material fed can be reduced. Therefore, the material yield of the final product manufactured from the drawing press forming after the preforming is improved by 3.6% as compared with the manufacturing by the conventional drawing press forming alone. As a result, it is possible to use a workpiece that is slightly smaller in size, which contributes to a reduction in material costs.

1 Roll 11, 14 Presser roll 12, 15 Expanding roll 13 Shaping roll W Work material

Claims (4)

In contact with one or both sides of a plate-like workpiece used for press molding,
At least one bar-shaped presser roll that forms the workpiece and applies tension to the workpiece;
At least one rod-shaped spreading roll that is bent and stretched in pressure contact with the workpiece;
And at least one rod-shaped shaping roll that is bent back into a substantially planar shape and is shaped in contact with the bent workpiece, and is initially arranged in parallel with each other.
A step of forming at least a part of the shape by moving the presser roll, the spreading roll, and the shaping roll in a substantially plate thickness direction of the workpiece;
The presser roll is fixed and tension is applied to the workpiece, and the spreading roll and the shaping roll move in a direction substantially parallel to the workpiece while maintaining the relative positional relationship to form the remaining shape. At the same time, the work roll bent and stretched by pressing the work roll from the one side while bending and extending the work roll, and the shaping roll being subsequently moved and bent. A process of contacting from the other side and bending back to a substantially planar shape;
A preforming method for press molding, comprising: In contact with one or both sides of a plate-like workpiece used for press molding,
At least one bar-shaped presser roll that forms the workpiece and applies tension to the workpiece;
At least one rod-shaped spreading roll that is bent and stretched in pressure contact with the workpiece;
At least one rod-shaped shaping roll which is in contact with the bent workpiece and is bent back into a substantially planar shape for shaping;
Roll driving means for moving the presser roll, the spreading roll and the shaping roll;
A roll gripping tool connected to the roll driving means and gripping the presser roll, the spreading roll and the shaping roll so as to be freely rotatable;
A workpiece gripping tool for gripping the outer periphery of the workpiece,
A pre-forming apparatus for press molding, characterized in that the presser roll, the spreading roll, and the shaping roll are initially arranged in parallel with each other and can be moved in a predetermined manner.   The presser roll, the spreading roll, and the shaping roll are composed of at least three parts that can independently rotate freely, the central part is a columnar or cylindrical shape with a constant outer diameter, and both end parts are end parts. The preforming apparatus according to claim 2, wherein the outer diameter of the preform is gradually reduced to a hemispherical shape having a smooth curvature.   The preform forming apparatus according to claim 3, wherein the roll gripping tool grips the presser roll, the extension roll, and the shaping roll on an inner side from a diameter reduction start position.