Method for controlling drawing machine
By using an eccentric device to adjust the material's axis before drawing, the method addresses bending issues in conventional processes, achieving high straightness and efficient production of drawn materials.
Patent Information
- Application Number
- JP2023152052
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-09-20
- Publication Date
- 2025-04-02
AI Technical Summary
Conventional drawing processes result in bending of materials due to misalignment during drawing, necessitating multiple straightening stages, which complicates the production process.
Implementing an eccentric device to displace the material's axis before drawing, adjusting the eccentricity based on a correlation between eccentricity amount and post-processing curvature to minimize bending, allowing for efficient production without additional straightening steps.
The method ensures high straightness of drawn materials by suppressing post-processing curvature, potentially eliminating the need for straightening processes and simplifying production.
Smart Images
Figure 2025044475000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for controlling a drawing apparatus. [Background technology]
[0002] Conventionally, there are known drawing devices and drawing methods in which a long material (rod, wire, tube) is drawn through a forming hole in a die and the outer peripheral shape of the material is changed according to the shape of the forming hole (see, for example, Patent Documents 1 and 2). The drawing process includes multiple straightening steps. For example, FIG. 1 of Patent Document 1 describes that after the material is drawn, it is straightened through a three-stage straightening process including spinner straightening, straightening with centerless grinding, and two-roll straightening. For example, FIG. 2 of Patent Document 2 describes that after the material is drawn, it is straightened through two stages: spinner straightening and two-roll straightening. [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] T. Kuboki, K. Kawasaki, S. Kajikawa, H. Matsumura, T. Ono, H. Seimiya, “Analysis of spinner straightening utilizing the finite element method”, COMPLAS XV, 2019, Barcelona, pp. 21 - 30. [Non-Patent Document 2] Satoru Nishida, Souichiro Nishino, Masahiko Sekine, Yuuki Oka, Stefanus Harjo, Takuro Kawasaki, Hiroshi Suzuki, Yukio Morii, Yoshinobu Ishii, "Analysis of Residual Stress in Steel Bar Processed by Cold Drawing and Straightening", Materials Transactions, Vol. 62, No. 5 (2021) pp. 667 - 674 Summary of the Invention [Problem to be solved by the invention]
[0004] In the conventional drawing process using a die, the issue is to ensure the straightness of the material (drawn material) after drawing. That is, the occurrence of bending is inevitable in the drawn material after drawing because the material before drawing remains bent, and the reciprocating movement line of the chuck when drawing the material from the die does not necessarily coincide with the axis of the die. When the drawing direction and the axis of the die are different, the drawing is performed in a direction having an angle with the axis of the die, and as a result, the drawing is performed in a bent state, and a difference occurs in the contact length between the material and the die on the back side and the ventral side of these bends. For this reason, the material is stretched more on the side with the shorter contact length, and bending occurs in the drawn material after drawing. In addition, when the die itself is not completely symmetrical, bending of the drawn material is also a cause of bending. In order to remove this bending of the drawn material, a straightening process is carried out after the drawing process, but as mentioned above, the straightening process has multiple stages, so there is a need to develop a technology that can improve the straightness of the drawn material and reduce the number of steps required for straightening or make the straightening process unnecessary. In other words, if the bending after drawing can be suppressed, it is expected that it will be possible to simplify the adjustment of straightening conditions, simplify the straightening process, and even omit the straightening process altogether.
[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a method for controlling a drawing apparatus which performs drawing by passing a material through a forming hole in a die, which enables efficient production of drawn material by simplifying or eliminating the correction process for the drawn material. [Means for solving the problem]
[0006] As a result of extensive investigation into the above problems, the present applicant has discovered the following configuration. That is, the applicant installed an eccentric device that eccentricates the axis of the material from the pass line (conveyance reference line) on the entry side (upstream side) of the die in the conveying path of the drawing processing device, making it possible to eccentricate the material at the entry side of the die (to give a pseudo curvature), and performed various experiments using this configuration to confirm the curvature of the material after drawing (curvature after processing). As a result, it was confirmed that the post-processing curvature of the material changes at the exit side of the die by eccentricating the material at the entry side of the die using the eccentric device. In particular, in the case of a small curvature such as that possessed by the material before and after drawing, it was found that an approximately linear relationship (proportional relationship) holds between the displacement amount of the eccentric device (the eccentricity amount of the material) and the post-processing curvature of the material after drawing. Based on this relationship, the configuration of the present invention was arrived at.
[0007] In view of the above-mentioned findings, a first aspect of the present invention provides a control method for a drawing device that transports a material along a conveying path, inserts the material from the upstream side into a forming hole of a die on the conveying path, and draws the material downstream of the forming hole to form a specified outer peripheral shape, the drawing device being equipped with an eccentricity device upstream of the die on the conveying path that can displace an axis of the material with respect to a reference line that overlaps with a straight imaginary axis, the drawing device being operated to draw the material for each of a plurality of eccentricity amounts set by the eccentricity device, and the method comprising: a first step of measuring the post-machined curvature of the material after drawing for each of the multiple eccentricity amounts, a second step of determining a correlation between the amount of eccentricity and the post-machined curvature from the measurement result of the first step, and a third step of operating the eccentricity device to adjust the amount of eccentricity based on the correlation determined in the second step.
[0008] According to this configuration, in a drawing device that conveys long material such as rod, wire, or tube along a conveying path and draws the material while reducing its diameter using a die, the device is provided with an eccentric device that displaces the axial center of the material upstream of the die in the conveying path, and the amount of displacement of the eccentric device (amount of eccentricity of the material) is adjusted based on the correlation with the post-processed curvature of the material after drawing, thereby making it possible to suppress the occurrence of post-processed curvature based on the initial curvature of the material, etc. For example, since the initial curvature of the material is stable while the same lot of material is being processed, the occurrence of post-processed curvature can be effectively suppressed by adjusting the amount of eccentricity by the eccentric device once. In this way, by finding a correlation between the amount of eccentricity by the eccentricity device and the post-processing curvature of the material after drawing, such as at the beginning of operation of the drawing device, and adjusting the amount of eccentricity based on this correlation so that the post-processing curvature is minimized (feedback control), it is possible to easily converge the post-processing curvature of the material after drawing (drawn material), thereby obtaining a drawn material with high straightness. As a result, the straightening process of the drawn material can be simplified or omitted, and the drawn material can be produced efficiently.
[0009] A second aspect of the present invention provides a method for controlling a drawing apparatus according to the first aspect, comprising: a fourth step of operating the drawing apparatus to draw a material having an amount of eccentricity caused by the eccentricity device of 0 and an initial curvature of 0, and measuring a post-processing curvature of the material after the drawing; a fifth step of operating the drawing apparatus to draw a material having an amount of eccentricity caused by the eccentricity device of 0 and a specified initial curvature, and measuring the post-processing curvature of the material after the drawing; and a sixth step of subtracting the post-processing curvature measured in the fourth step from the post-processing curvature measured in the fifth step to determine a post-processing curvature due to the influence of the specified initial curvature, and calculating an amount of eccentricity for removing the post-processing curvature due to the influence of the initial curvature based on the correlation between this post-processing curvature and the second step, wherein the third step is performed in a state in which the amount of eccentricity calculated in the sixth step is generated in advance in the eccentricity device.
[0010] According to this configuration, by performing drawing processing on a material with zero eccentricity and zero initial curvature by the eccentric device, it is possible to confirm the post-processing curvature caused by factors other than the initial curvature (i.e., drawing angle). By performing drawing processing on a material with zero eccentricity and a specified initial curvature by the eccentric device, it is possible to confirm the post-processing curvature caused mainly by two factors (initial curvature and drawing angle). By subtracting the post-processing curvature caused by factors other than the initial curvature from the post-processing curvature caused by multiple factors, it is possible to obtain the post-processing curvature caused by the specified initial curvature. Based on this post-processing curvature and the correlation obtained in the second step, it is possible to calculate the amount of eccentricity for removing the post-processing curvature caused by the initial curvature. By generating the amount of eccentricity calculated in this way in advance in the eccentric device (feedforward control), it is possible to achieve a state in which the post-processing curvature caused by the initial curvature has been removed. By adjusting the amount of eccentricity by the eccentric device based on the post-processing curvature from this state, it is possible to efficiently obtain the amount of eccentricity for removing the post-processing curvature. Effect of the Invention
[0011] According to the present invention, in a control method for a drawing apparatus that performs drawing by passing a material through a forming hole in a die, it is possible to simplify or omit the correction process for the drawn material, thereby making it possible to efficiently produce drawn material. [Brief description of the drawings]
[0012] [Figure 1] FIG. 1 is a schematic explanatory diagram of a drawing device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view of an experimental device for the drawing apparatus. [Diagram 3] FIG. 2 is a cross-sectional view of the main body of the experimental device. [Figure 4] FIG. 4 is a view taken along line IV in FIG. 3, showing a guide device for the experimental device. [Diagram 5] FIG. 2 is an explanatory diagram showing how the material is inserted into a die in the above-mentioned experimental apparatus. [Figure 6A] FIG. 1 is a first explanatory diagram showing a state in which a material having an initial curvature is drawn. [Figure 6B]FIG. 6B is a second explanatory diagram showing the material after drawing in FIG. 6A. [Figure 7A] FIG. 11 is a third explanatory diagram showing the manner in which a material is drawn at a predetermined drawing angle. [Figure 7B] FIG. 7B is a fourth explanatory diagram showing the material after the drawing process of FIG. 7A. [Figure 8A] FIG. 5 is a fifth explanatory diagram showing how a material having an initial curvature is drawn at a predetermined drawing angle. [Figure 8B] FIG. 8B is a sixth explanatory diagram showing the material after the drawing process of FIG. 8A. [Figure 9A] FIG. 8B is a seventh explanatory diagram showing a state in which a drawing process is performed by giving an eccentricity to the material in comparison with FIG. 8A . [Figure 9B] FIG. 9B is an eighth explanatory diagram showing the material after drawing in FIG. 9A. [Figure 10] 1 is a graph showing the results of drawing a workpiece with a plurality of eccentricity amounts using the above-mentioned experimental device, in which the vertical axis shows the curvature of the workpiece after processing, and the horizontal axis shows the eccentricity amount. [Figure 11] This is a graph showing the results of drawing a workpiece with an initial curvature of 0 at a specified drawing angle using the above experimental device, where the vertical axis shows the curvature of the workpiece after processing and the horizontal axis shows the measurement position of the workpiece. [Figure 12] 1 is a graph showing the results of drawing a workpiece having a predetermined initial curvature at a predetermined drawing angle using the above-mentioned experimental device, in which the vertical axis shows the curvature of the workpiece after processing and the horizontal axis shows the measurement position of the workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] An embodiment of the present invention will be described below with reference to the drawings, but the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. The term "middle" used in this embodiment includes not only the center between both ends of an object, but also an inner part and a predetermined range between both ends of an object.
[0014] FIG. 1 is an explanatory diagram showing an outline of a drawing apparatus 1A according to an embodiment. The drawing apparatus 1A is used to manufacture drawn materials by reducing the outer diameter of a long material (workpiece) W such as a bar, wire, or tube to a specified outer diameter. The drawing apparatus 1A transports the long material W along a transport path 2 extending in the left-right direction in the figure. The left side of the transport path 2 in the figure is the upstream side, and the right side is the downstream side. Line T1 in the figure indicates a reference line that extends along the transport direction and overlaps with a virtual axis center when the material W is straight. In the figure, the Z axis indicates the transport direction that overlaps with the reference line T1, the Y axis indicates the direction perpendicular to the Z axis (the up-down direction on the figure), and the X axis indicates the direction perpendicular to the Y axis and the Z axis (the front-back direction perpendicular to the figure).
[0015] The conveying path 2 is provided with a material feeding device 3, a die 5, and a material pulling device 7 in this order from the upstream side to the downstream side. The material feed device 3 uses rollers or the like to feed the material W of a specified length, which has been subjected to a narrowing process at its upstream end, downstream in the conveying direction. The material feed device 3 of this embodiment is provided with an entry guide device (eccentric device) 11, which applies displacement in the X direction and Y direction perpendicular to the conveying direction, at the middle part in the longitudinal direction of the material W. The entry guide device 11 includes an eccentric mechanism that shifts the axis C1 of the material W in at least one of the X direction and Y direction relative to a reference straight line T1 to create an eccentric state.
[0016] The entry-side guide device 11 includes a guide member 12 that holds the material W by pinching it from at least both radial sides. The entry-side guide device 11 can move the guide member 12 holding the material W by operating an eccentric mechanism so that the axis C1 of the material W is displaced in at least one of the X direction and the Y direction or obliquely with respect to a reference straight line T1. The movement of the guide member 12 may be performed manually, for example, or automatically by a drive source and a control device (not shown).
[0017] The material feed device 3 is provided with an entry-side holding device 15 that holds the axis C1 of the material W on the reference line T1, located upstream of the entry-side guide device 11 in the conveying direction (the side away from the die 5). The entry-side holding device 15 is provided with a holding member 16 that holds the material W by pinching it from at least both radial sides. The holding member 16 may have the same configuration as the guide member 12 of the entry-side guide device 11, for example. The holding member 16 is immovable with respect to the conveying path 2, for example, and fixes the axis C1 of the material W on the reference line T1 at the installation position of the entry-side holding device 15. The holding member 16 may hold the material W with a gap. For example, the entry-side holding device 15 may be configured to hold the material W with a margin that allows at least a part of the material W to be positioned on the reference line T1 at the installation position. The entry-side holding device 15 contributes to stable bending and conveying of the material W, but it is also possible to eliminate the holding device 15.
[0018] The die 5 is made of a material such as metal or metal carbide that is harder than the material W to be processed. The die 5 is substantially cylindrical, and a forming hole 6 is formed in the center along the axis C2, through which the rod-shaped material W is inserted to reduce the diameter. The forming hole 6 has a tapered portion 6a formed on the upstream side of the die 5 in the conveying direction such that the inner diameter becomes wider toward the upstream side, and a small diameter portion 6b formed to have a constant inner diameter on the downstream side of the die 5 in the conveying direction.
[0019] The upstream end of the tapered portion 6a in the conveying direction forms an upstream opening with a larger diameter than the processing target portion Wb of the material W (excluding the narrowed portion Wa) on the side surface of the die 5 on the upstream side in the conveying direction. A small diameter portion 6b of the same diameter as this end is continuous with the downstream end of the tapered portion 6a in the conveying direction. The downstream end of the small diameter portion 6b in the conveying direction forms a downstream opening with a smaller diameter than the upstream opening on the side surface of the die 5 on the downstream side in the conveying direction. A chamfer 6c is applied to the periphery of the downstream opening. The boundary portion between the cylindrical inner surface of the small diameter portion 6b and the inner surface of the chamfer 6c is located at the die exit point O described later.
[0020] The inner diameter of the cylindrical inner peripheral surface of the small diameter portion 6b is smaller than the outer diameter of the processing target portion Wb of the raw material W. When the raw material W is inserted into this small diameter portion 6b via the tapered portion 6a and pulled out, the processing target portion Wb of the raw material W is ironed by the tapered portion 6a and plastically deformed so as to reduce in diameter, and the outer peripheral surface is smoothed and adjusted to a constant outer diameter by the small diameter portion 6b, so that a drawn material having a specified cross-sectional shape can be obtained.
[0021] The material pulling device 7 is equipped with a chuck 8 that grips the narrowed portion Wa protruding downstream in the conveying direction of the forming hole 6 of the die 5, and a drive mechanism (not shown) that reciprocates the chuck 8 along the conveying direction. At the beginning of the drawing process, the chuck 8 is located at the upstream end of the reciprocating range, and multiple holding claws bite and grip the narrowed mouth portion Wa of the material W that protrudes downstream in the conveying direction of the die 5. The chuck 8 holding the narrowed mouth portion Wa moves from the upstream end to the downstream end of the reciprocating range, and pulls the material W inserted into the forming hole 6 of the die 5 from the forming hole 6. When the chuck 8 reaches the downstream end of the reciprocating range in the conveying direction, it opens its holding claws and releases the narrowed mouth portion Wa, and in that state returns to the upstream end of the reciprocating range in the conveying direction and bites and grips the material W again. By repeating this process, it is possible to continuously pull out the long material W downstream in the conveying direction.
[0022] In the drawing apparatus 1A of the embodiment, an entry guide device 11 is provided upstream of the die 5 in the conveying direction. In the conveying direction, an entry holding device 15 is provided upstream of the entry guide device 11 in the conveying direction (opposite the die 5) at a distance Lb equivalent to the distance La between the die 5 and the entry guide device 11. In the conveying direction, the position of the entry holding device 15 on the reference line T1 is the entry holding point A, the position of the entry guide device 11 on the reference line T1 is the rolling point B, and the contact position on the reference line T1 between the die 5 and the material W is the die exit point O. The distance between the die exit point O and the rolling point B is La, and the distance between the rolling point B and the entry holding point A is Lb. The displacement (eccentricity) of the shaft center C1 at the position of the rolling point B is indicated by δ.
[0023] FIG. 2 shows an experimental apparatus 100 for confirming the effects of the drawing apparatus 1A of the embodiment. The experimental apparatus 100 utilizes a driving device 101 used for tensile tests of materials, etc. The driving device 101 connects the upper ends of left and right side walls 102 with an upper wall 103, and connects the lower parts of the left and right side walls 102 with a fixed table 104. Above the fixed table 104, a lifting table 105 is disposed, which is supported by the left and right side walls 102 so as to be able to move up and down.
[0024] 3, an apparatus main body 110 is installed across the fixed table 104 and the lift table 105. In the experimental apparatus 100, the pulling direction of the material W (and the reference line T1) is oriented vertically. The device main body 110 includes a fixed side assembly 111 fixed to a fixed frame, and a lifting side assembly 113 fixed to the lifting table 105 .
[0025] The fixed-side assembly 111 is provided with a chuck 8 that grips a narrowed-mouth portion Wa (the lower end portion in the drawing) of the material W. With the lower end portion of the material W gripped by the chuck 8, a portion to be processed Wb extends upward and is inserted into the lifting-side assembly 113. The lifting side assembly 113 is equipped with a die 5 and an inlet guide device 11, and by this lifting side assembly 113 moving upward (away from the chuck 8) together with the lifting table 105, a situation is reproduced in which the chuck 8 relatively pulls out the material W downward from the die 5.
[0026] The lifting assembly 113 includes a die case 114 that houses the die 5, and a guide case 116 that is supported above the die case 114 via bearings 116a and houses the entry guide device 11. The die case 114 is fixed to the lifting table 105 via a fixing flange 115. The guide case 116 includes a plurality of handles 117 that extend radially in a top view, and a screw mechanism 118 that enables the radial position of the guide member 12 of the entry guide device 11 to be moved.
[0027] 4, the guide member 12 of the experimental apparatus 100 is a rectangular parallelepiped block having an insertion hole 12a through which the material W is inserted. The guide member 12 faces its longitudinal direction in a horizontal direction (radial direction) perpendicular to a reference line T1 along the vertical direction, and is housed in a die case 114 so as to be displaceable in the longitudinal direction. Tips of adjustment screws 118a fastened from the outer periphery of a guide case 116 in a screw mechanism 118 abut on both longitudinal sides of the guide member 12. The radial position of the guide member 12 can be adjusted with respect to the reference line T1 by adjusting the amount of fastening of the adjustment screws 118a on both longitudinal sides.
[0028] 5, the relationship between the curvature of the material W upstream of the die 5 in the conveying direction and the offset amount (eccentricity amount δ) of the inlet guide device 11 is obtained, for example, in the following preliminary experiment. In the preliminary experiment, the material W is drawn twice in the order of diameter "10 mm → 9.7 mm → 9.4 mm" without the inlet guide device 11 (or with an eccentricity amount δ of 0). The curvature of the material W after drawing at this time (hereinafter referred to as the post-processing curvature) is set as a target value, and the offset amount (eccentricity amount δ) of the inlet guide device 11 in the following main experiment is set.
[0029] The preliminary experiment is performed using a material W with no initial bending (material W with an initial curvature of 0). When the material W is subjected to the above-mentioned two drawing processes, occurrence of bending of the material W due to factors other than the initial bending is confirmed. The bending of the material W at this time is set as the target value of the main experiment, and the correction effect by offsetting the entry side guide device 11 is confirmed. For example, a bending of the material W to the left in the figure with respect to the die axis C2 is defined as a positive curvature, and a bending of the material W to the right in the figure with respect to the die axis C2 is defined as a negative curvature.
[0030] In this embodiment, an eccentricity device (entrance guide device) 11 that eccentricates the axis C2 of the material W from the pass line (reference straight line) T1 is installed on the entry side (upstream side) of the die 5 in the conveying path 2 of the drawing apparatus 1A. The eccentricity device 11 displaces the material W from the pass line T1 on the entry side of the die 5, making it possible to impart a pseudo curvature to the material W.
[0031] FIG. 10 is a graph showing the results of drawing the material W for each of a plurality of eccentricity amounts δ, and measuring the post-processing curvature C of the material W for each eccentricity amount (displacement amount of the guide 12) δ of the material W. 10, by decentering the material W on the inlet side of the die 5 using the eccentricity device 11, the post-processing curvature C of the material W changes on the outlet side of the die 5. In particular, in the case of a small curvature C such as that of the material W before and after drawing, a nearly linear relationship (proportional relationship) is established between the amount of eccentricity δ of the material W and the post-processing curvature C of the material W after drawing.
[0032] Referring to FIG. 6A, in measuring the post-processing curvature C in the embodiment, first, a material W having a specified initial curvature C0 is drawn without eccentricity by a guide 12. The specified initial curvature C0 is a curvature measured in advance or a curvature imparted in a preliminary process. In this experiment, the drawing angle α on the die exit side is 0. In this experiment, as shown in FIG. 6B, a post-processing curvature Cli remains in the material W after the drawing process. Here, the relationship between the post-processing curvature Cli and the initial curvature C0 is assumed to be expressed by the following formula 1. Cli = ki C0 (proportionality coefficient ki is assumed to be known) Equation 1
[0033] Following the above experiment, multiple eccentricity amounts δ of the raw material W are set, drawing is performed for each of the multiple eccentricity amounts δ, and the post-processing curvature C of the raw material W after drawing is measured. As in this experiment, the first step is to operate the drawing device 1A, perform drawing of the raw material W for each of the multiple eccentricity amounts δ set by the eccentricity device 11, and measure the post-processing curvature C of the raw material W after drawing for each of the multiple eccentricity amounts δ.
[0034] In this experiment, as shown by line L1 in Fig. 10, the correlation line between the amount of eccentricity δ caused by the guide 12 and the post-machining curvature C of the material W after drawing is nearly linear, and it is found that a nearly linear relationship holds between the amount of eccentricity δ and the post-machining curvature C. The proportionality coefficient kg between the amount of eccentricity δ and the post-machining curvature C at this time is expressed by the following equation 2. kg=ΔC / Δδ≒C / δ Equation 2
[0035] As described above, the second step is a step of determining the correlation between the eccentricity δ of the material W and the post-machining curvature C from the measurement results of the first step. From the results of the above experiments, the amount of eccentricity δ of the raw material W required to remove the post-processing curvature C due to the initial curvature C0 can be determined from the post-processing curvature C of the raw material W after drawing, based on the degree of influence (coefficient kg) of the amount of eccentricity δ on the post-processing curvature C of the raw material W after drawing.
[0036] Regarding the post-processing curvature C after drawing of the raw material W having the initial curvature C0, the correlation between the eccentricity δ and the post-processing curvature C is found as in the above experiment at the beginning of operation of the drawing device 1A when producing a drawn material, and the eccentricity δ is feedback-controlled based on the coefficient kg obtained from this correlation. In this way, the process of adjusting the eccentricity δ by operating the eccentricity device 11 based on the correlation found in the second process is defined as the third process. As a result, as the operation of the drawing apparatus 1A progresses, it becomes possible to obtain a drawn material with such high straightness that a correction process is not required.
[0037] Referring to FIG. 7A, in an actual production line for drawn material, a drawing angle α is unavoidably present on the die outlet side. In the embodiment, a raw material W with an initial curvature of 0 is prepared, and drawing is performed without eccentricity by the guide 12 (or the amount of eccentricity δ is 0). In this experiment, for example, the position of the chuck 8 is shifted to reproduce the drawing angle α. In this experiment, as shown in FIG. 7B, a post-processing curvature Cld remains in the raw material W after drawing. This post-processing curvature Cld corresponds to the post-processing curvature C generated in the raw material W after drawing due to the drawing angle α. The post-processing curvature Cld of the raw material W after drawing at the drawing angle α was measured at multiple axial positions of the raw material W, and the results are shown in FIG. 11 by line L2.
[0038] Although not shown, an approximately linear relationship also holds between the drawing angle α and the post-machined curvature Cld of the material W after drawing. That is, when an experiment is conducted to remove the post-machined curvature C by changing the eccentricity δ of the material W for a material W with an initial curvature of 0, the correlation line between the eccentricity δ of the material W and the post-machined curvature C of the material W after drawing is approximately linear. The eccentricity δ for removing the post-machined curvature Cld after drawing at the drawing angle α can be obtained from the post-machined curvature Cld of the material W after drawing, based on the influence (coefficient kg) of the eccentricity δ on the post-machined curvature C of the material W after drawing.
[0039] Regarding the post-processing curvature Cld after drawing at the drawing angle α, the correlation between the eccentricity δ and the post-processing curvature C is calculated at the beginning of operation of the drawing apparatus 1A when producing a drawn material, and the eccentricity δ is feedback-controlled based on the coefficient kg obtained from this correlation. As a result, as the operation of the drawing apparatus 1A progresses, it becomes possible to obtain a drawn material with such high straightness that a correction process is not required.
[0040] 6B, 7B, 8A, and 8B, it is assumed that the actual post-processing curvature Cln of the material W after drawing, including the two factors of the initial curvature C0 and the drawing angle α, can be obtained by adding together the post-processing curvature Cli after drawing based on the initial curvature C0 of the material W and the post-processing curvature Cld after drawing based on the drawing angle α on the die exit side, with reference to the following equation 3. Cln=Cli+Cld...Equation 3
[0041] 9A and 9B, it is assumed that the eccentricity amount δm of the raw material W required to remove the post-machining curvature Cln of the raw material W after the actual drawing process (actually, to make the curvature Cln' more linear than the post-machining curvature Cln) is obtained by adding up the "eccentricity amount δ1 of the raw material W to remove the post-machining curvature Cli" and the "eccentricity amount δ2 of the raw material W to remove the post-machining curvature Cld." In other words, it is assumed that the following formula 4 holds true. δm = δ1 + δ2 Equation 4
[0042] In actual drawing, the material is affected by both the initial curvature C0 and the drawing angle α, but even in that case, the correlation between the eccentricity δ and the post-processing curvature C is calculated at the beginning of operation of the drawing apparatus 1A, and the eccentricity δ is feedback-controlled based on the coefficient kg obtained from this correlation. This makes it possible to obtain a drawn material with such high straightness that a correction process is not required as the operation of the drawing apparatus 1A progresses.
[0043] However, in order to converge the effects of the two factors, the initial curvature C0 and the drawing angle α, into a single variable, the eccentricity amount δ of the material W, it may take a long time to determine the optimal eccentricity amount δ.
[0044] In the embodiment, in addition to feedback control based on the post-machining curvature Cln of the material W after drawing, the post-machining curvature Cli after drawing is calculated based on the initial curvature C0 of the material W measured in advance, and the "eccentricity amount δ1 of the material W for removing the post-machining curvature Cli" is calculated in advance to displace the guide 12 (feedforward control).
[0045] The post-processing curvature Cli is calculated by the above formula 1. However, if the "coefficient ki" is not determined, the post-processing curvature Cld obtained from the drawing process using a material W with a drawing angle α and an initial curvature C0 of 0 (the post-processing curvature Cld of the material W after drawing due to the influence of the drawing angle α) and the post-processing curvature Cln actually measured from the material W after the actual drawing process are used to calculate back from the above formula 3 to obtain the post-processing curvature Cli.
[0046] The amount of eccentricity δ1 of the raw material W for removing the post-machining curvature Cli can be found from the post-machining curvature Cli based on the degree of influence (coefficient kg) of the amount of eccentricity δ on the post-machining curvature C of the raw material W.
[0047] As a result, the eccentricity δ1 of the raw material W is given in advance, and in a state in which the post-processed curvature Cli of the raw material W after drawing based on the initial curvature C0 is removed, the eccentricity δ2 of the raw material W for removing the post-processed curvature Cld of the raw material W after drawing based on the drawing angle α can be calculated, and finally the eccentricity δm of the raw material W in the actual drawing can be calculated (see formula 4 above).
[0048] As a result, the post-processing curvature Cln of the material W after drawing, which is based on the two factors of the initial curvature C0 and the drawing angle α, can be converged efficiently in a shorter operating time compared to the case where it is converged collectively using feedback control alone, and a drawn material (drawn material) with high straightness can be obtained.
[0049] Fig. 12 is a graph showing the measurement results of the post-processing curvature C when a blank W having a specified initial curvature C0 is drawn at a preset drawing angle α. First, the results of measuring the initial curvature C0 at multiple axial positions of the blank W are shown by line L3 in Fig. 12. The initial curvature C0 is in the positive region.
[0050] The result of drawing this blank W at a drawing angle α without eccentricity caused by the guide 12 is shown by line L4 in Figure 12. The curvature C of line L4 after processing is reduced to about half of the initial curvature C0 of line L3, but the curvature C still remains in the positive region.
[0051] On the other hand, when the blank W is drawn at a drawing angle α with a specified initial curvature C0 while being given an eccentricity δm determined based on the above-mentioned feedback control and feedforward control concepts, it has been confirmed that the curvature C after processing approaches (converges) to 0 overall, as shown by line L5 in FIG. 12.
[0052] As described above, the control method of the drawing apparatus in the above embodiment is a control method of the drawing apparatus 1A which conveys the raw material W along the conveying path 2, inserts the raw material W from the upstream side into the forming hole 6 of the die 5 on the conveying path 2, and draws the raw material W to the downstream side of the forming hole 6 to form a specified outer peripheral shape. The drawing apparatus 1A is provided with an eccentricity device 11 upstream of the die 5 on the conveying path 2 which can displace the axis C1 of the raw material W with respect to a reference line T1 overlapping with a straight imaginary axis center, and is provided with the following steps: a first step of operating the drawing apparatus 1A, drawing the raw material W for each of a plurality of eccentricity amounts δ set by the eccentricity device 11, and measuring the post-processed curvature C of the raw material W after drawing for each of the plurality of eccentricity amounts δ; a second step of determining the correlation between the eccentricity amount δ and the post-processed curvature C from the measurement result of the first step; and a third step of operating the eccentricity device 11 to adjust the eccentricity δ based on the correlation determined in the second step.
[0053] According to this configuration, in a drawing apparatus 1A in which a long material W such as a bar, wire, or tube is transported along a transport path 2 and drawn into a drawn material while being reduced in diameter using a die 5, an eccentric device 11 for displacing an axial center C1 of the material W is provided upstream of the die 5 on the transport path 2, and the amount of displacement (amount of eccentricity of the material W) δ of this eccentric device 11 is adjusted based on the correlation with the post-processed curvature C of the material W after the drawing process, thereby making it possible to suppress the occurrence of a post-processed curvature C based on an initial curvature C0 of the material W, etc. For example, since the initial curvature C0 of the material W is stable while the same lot of material W is being processed, the occurrence of a post-processed curvature C can be effectively suppressed by adjusting the amount of eccentricity δ by the eccentric device 11 once. In this way, by finding a correlation between the amount of eccentricity δ by the eccentricity device 11 and the post-processing curvature C of the material W after drawing, such as at the beginning of operation of the drawing apparatus 1A, and adjusting the amount of eccentricity δ based on this correlation so that the post-processing curvature C is minimized (feedback control), it is possible to easily converge the post-processing curvature C of the material W (drawn material) after drawing, and obtain a drawn material with high straightness. As a result, the straightening process of the drawn material can be simplified or omitted, and the drawn material can be produced efficiently.
[0054] The control method for the drawing apparatus includes a fourth step of operating the drawing apparatus 1A to perform drawing of a material W having an eccentricity δ of 0 by the eccentricity device 11 and an initial curvature C0 of 0, and measuring a post-processing curvature Cld of the material W after the drawing; a fifth step of operating the drawing apparatus 1A to perform drawing of a material W having an eccentricity δ of 0 by the eccentricity device 11 and a specified initial curvature C0, and measuring a post-processing curvature Cln of the material W after the drawing; and a sixth step of calculating an eccentricity δ1 for removing the post-processing curvature Cli due to the influence of the specified initial curvature C0 based on the post-processing curvature Cli and the correlation obtained in the second step, and performing the third step with the eccentricity δ1 calculated in the sixth step being generated in advance in the eccentricity device 11.
[0055] According to this configuration, by performing drawing processing of the material W with an eccentricity amount δ of 0 and an initial curvature C0 of 0 by the eccentric device 11, it is possible to confirm the post-processing curvature C caused by factors other than the initial curvature C0 (i.e., the drawing angle α). By performing drawing processing of the material W with an eccentricity amount δ of 0 and a specified initial curvature C0 by the eccentric device 11, it is possible to confirm the post-processing curvature C caused mainly by two factors (initial curvature C0 and drawing angle α). By subtracting the post-processing curvature C caused by factors other than the initial curvature C0 from the post-processing curvature C caused by multiple factors, it is possible to obtain the post-processing curvature C caused by the specified initial curvature C0. Based on this post-processing curvature C and the correlation obtained in the second step, it is possible to calculate the eccentricity amount δ for removing the post-processing curvature C caused by the initial curvature C0. By generating the eccentricity amount δ calculated in this way in advance in the eccentric device 11 (feedforward control), it is possible to obtain a state in which the post-processing curvature C caused by the initial curvature C0 is removed. From this state, by adjusting the amount of eccentricity δ by the eccentricity device 11 based on the post-processing curvature C, the amount of eccentricity δ for removing the post-processing curvature C can be obtained efficiently.
[0056] The present invention can be widely used in industry to manufacture components for precision instruments such as shafts and various parts of automobiles, paper feed shafts for printers, and medical instruments. The configurations in the above-described embodiments are merely examples of the present invention, and various modifications are possible without departing from the gist of the present invention, such as replacing the components of the embodiments with well-known components. [Explanation of symbols]
[0057] 1A drawing processing equipment 2. Transport Route 5 Dice 11 Inlet guide device (eccentric device) 12 Guide member (guide) C,Cli,Cld,Cln,Cln' Curvature after machining C0 initial curvature C1 axis center kg,ki coefficient T1 Reference Line W Material α Pulling angle δ,δ1,δ2 Eccentricity
Claims
1. A method for controlling a drawing device, which transports a material along a transport path, inserts the material from an upstream side into a forming hole of a die located on the transport path, and draws the material downstream of the forming hole to form a specified outer peripheral shape, comprising the steps of: the drawing device includes an eccentric device, located upstream of the die in the conveying path, that can displace an axis of the material with respect to a reference line that overlaps with a straight imaginary axis, a first step of operating the drawing device, drawing the material for each of a plurality of eccentricities set by the eccentricity device, and measuring a post-processing curvature of the material after the drawing for each of the plurality of eccentricities; a second step of determining a correlation between the amount of eccentricity and the post-machining curvature from the measurement result of the first step; and a third step of operating the eccentricity device to adjust the amount of eccentricity based on the correlation obtained in the second step.
2. a fourth step of operating the drawing device to draw the material having an eccentricity amount of 0 and an initial curvature of 0 by the eccentricity device, and measuring the post-processing curvature of the material after the drawing; a fifth step of operating the drawing device to draw the material having the specified initial curvature when the amount of eccentricity by the eccentricity device is zero, and measuring the post-processing curvature of the material after the drawing; a sixth step of setting a value obtained by subtracting the post-machining curvature measured in the fourth step from the post-machining curvature measured in the fifth step as the post-machining curvature due to the influence of the specified initial curvature, and calculating the amount of eccentricity for removing the post-machining curvature due to the influence of the initial curvature based on the post-machining curvature and the correlation obtained in the second step, 2. The method for controlling a drawing apparatus according to claim 1, wherein the third step is performed in a state in which the amount of eccentricity calculated in the sixth step is generated in the eccentricity device in advance.