Method for controlling gripping in upset forging and system thereof

Abstract

The present invention can optimally control the timing and the gripping force of a grip die for gripping a forging material in upset forging.　When a forging material W is set in the grip mold, an AC servo motor of a grip mechanism is activated, and a crank shaft is rotationally driven to cause a grip ram 31 to be lowered. A grip upper die that is integral with the grip ram 31 is lowered to grip and fix the forging material W between the grip upper die and a grip lower die. After the grip ram 31 is lowered, the forging material W is gripped and fixed at a pressure equal to or lower than a preset pressure by means of a hydraulic cylinder chamber 36.

Description

Grip control method and system for upset forging

[0001] The present invention relates to a grip control method and system for upset forging. More specifically, the present invention relates to a grip control method and system for upset forging that can optimize the control of the grip pressure and the control of the upset forging timing in an upset forging grip system having a die that grips the forging material in a half-split structure.

[0002] Upset forging is a known processing method in which a portion of a long workpiece is heated, compressed axially, and expanded diametrically. The upsetter used for upset forging is a double-action forging machine equipped with two mechanisms: one for clipping (gripping) the shaft of the long workpiece, and the other for axially pressurizing it. Some upsetters use a grip die with a split upper and lower half to grip the forging material, and then form the tip of the cold or heated forging material using a horizontal press. This type of upsetter offers advantages, such as easy loading and unloading of the forging material (workpiece), a smaller die size, and a short stroke between the upper and lower dies. However, during workpiece forging using a horizontal press, forging pressure is applied inside the grip die, creating a force that tends to expand the grip die consisting of the upper and lower dies.

[0003] If the clamping force (grip force) between the upper and lower dies is weak or the dies are not tightly connected, the split-section grip die will separate, resulting in forging burrs. Even if the grip drive mechanism is fine-tuned to ensure tight contact between the upper and lower grip dies, the optimal clamping force cannot be achieved due to the elongation of the frame, etc., which supports the load on the grip die. On the other hand, conventional upsetters typically combine a crank mechanism and a link mechanism to ensure the clamping force of the upper and lower grip dies that grip the forging material. While these drive mechanisms have advantages such as fast operation and easy synchronization, they are complex and often require experienced technicians for fine adjustment. Poor adjustment can result in overload, causing the link mechanism to break down. Therefore, a hydraulic cylinder mechanism has been proposed to drive the grip tool to ensure the grip force of the upper and lower grip dies at the desired pressure (see, for example, Patent Document 1).

[0004] Special Publication No. 49-6471

[0005] The hydraulic cylinder-driven grip die (die) described in the aforementioned Patent Document 1 has a function of activating a relief valve to protect the grip die in the event of an overload. However, it is difficult to link the mechanism driving the upper grip tool 14 of the grip die and the wedge mechanism driving the heading tool 5, and to adjust the timing to synchronize these mechanisms. An object of the present invention is to provide a grip control method and system for upset forging that can optimize the gripping force and timing of the grip die that grips the forging material. Another object of the present invention is to provide a grip control method and system for upset forging that can minimize malfunctions such as breakdowns of the grip die that grips the forging material. A further object of the present invention is to provide a grip control method and system for upset forging that can accurately control the stopping time, gripping operation time, and reverse rotation top point position of the grip die that moves to grip the forging material.

[0006] The grip control method for upset forging of present invention 1 is an upset forging system using an upsetter comprising: a press machine that performs upset forging; a grip die that grips a portion of the forging material when performing the upset forging, the grip die consisting of a split die consisting of a fixed die and a movable die; a crank mechanism that drives a grip ram that drives one of the movable dies of the grip die in a linear direction; a servo motor that rotates and drives the crank mechanism; a detector that detects the position of the movable die; and control means that controls the press machine and the grip die, wherein the control means operates the press machine to perform the upset forging based on a position signal from the detector.

[0007] The grip control method for upset forging of present invention 2 is characterized in that, in the grip control method for upset forging of present invention 1, in order to limit the gripping pressure of the gripping die, the gripping force with which the movable die presses the fixed die is limited to a set value or less via hydraulic pressure at the bottom dead center position of the movable die.

[0008] The grip control system for upset forging of present invention 1 is characterized by comprising: a press machine that performs upset forging; a grip die that grips a portion of the forging material, which is divided into a fixed die and a movable die, when performing the upset forging; a crank mechanism that drives a grip ram that drives one of the movable dies of the grip die in a linear direction; a servo motor that rotates and drives the crank mechanism; a detector that detects the position of the movable die; and a control device that detects the position of the movable die and operates the press machine to perform upset forging.

[0009] The upset forging grip control system of the present invention 2 is characterized in that, in the upset forging grip control system of the present invention 1, it comprises a hydraulic cylinder device that limits the gripping force with which the movable die presses the fixed die at the bottom dead center position of the movable die to a set value or less in order to limit the pressure for the pressurizing.

[0010] The upset forging grip control method and system of the present invention can accurately control the timing of upset forging, thereby achieving precise forging. Furthermore, the gap between the divided grip dies can be precisely and easily adjusted, suppressing the occurrence of burrs in the forged material and stabilizing the shape. Furthermore, delicate adjustment of the grip mechanism is no longer necessary, and wear and damage to drive parts due to overload is eliminated. Furthermore, poor gripping due to misalignment of the forged material can be detected, preventing forging defects and breakdowns.

[0011] Figure 1 is an external view showing the appearance of the upset forging system. Figure 2 is a cross-sectional view of the crank mechanism portion of the grip mechanism. Figure 3 is a cross-sectional view taken along line A-A in Figure 2. Figure 4 is a block diagram showing an overview of the control device of the upsetter forging system. Figure 5 is a time chart showing an example of upset forging operation by the upsetter forging system.

[0012] [Overview of Upset Forging System 1] A first embodiment of the upset forging grip control method and system of the present invention will be described below with reference to the drawings. Fig. 1 is an external view showing the overall appearance of an upset forging system (hereinafter also referred to as an "upsetter") 1. The upset forging system 1 generally comprises a horizontal press 2 for performing upset forging, a gripping mechanism 3 for gripping and fixing the forging material W during upset forging, and a workpiece loading / unloading robot 4 for loading and unloading the forging material W into and from the gripping mechanism 3. The horizontal press 2 is a well-known, general-purpose press machine for forging and pressing, comprising an electric motor, a flywheel, a crank mechanism (eccentric shaft, connecting rod, header ram), and a clutch / brake for turning the header ram on and off. The horizontal striking press 2 in this example is a forging press machine in which a header ram (not shown) is driven horizontally (sideways) and an upset die 10 mounted on this header ram is used to forge the tip of the forging material W into the desired shape.

[0013] FIG. 2 is a cross-sectional view of the crank mechanism portion of the gripping mechanism. FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 2. The gripping mechanism 3 is a mechanism for gripping and fixing the forging material W with a die consisting of an upper gripping die 32 and a lower gripping die 33. The gripping mechanism 3 grips and fixes the forging material W when forging it with the upset die 10 of the horizontal striking press 2 (see FIG. 1). The lower gripping die 33 is fixed to the gripping mechanism body 5. The upper gripping die 32 fixed to the gripping ram 31 descends (in the x-axis direction) when gripping the forging material W and ascends when not forging. The vertical drive mechanism for the upper gripping die 32 is a crank mechanism, as described below. The supply, transfer, and removal of the forging material W to the upset forging system 1 are performed by a workpiece loading / unloading robot 4 or the like.

[0014] FIG. 2 is a cross-sectional view of the crank mechanism portion of the gripping mechanism 3. FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 2. The gripping mechanism 3 grips and fixes the forging material W when upset forging is performed in the horizontal striking press 2. The tip of this forging material W is forged into a desired shape by the upset die 10 of the horizontal striking press 2. As shown in FIGS. 2 and 3, the gripping mechanism 3 includes a crank mechanism known as a Scotch yoke type, which converts rotational motion into linear motion. The crank mechanism drives a gripping ram 31, which has a rectangular cross-sectional shape, in a linear direction (the x-axis direction (up and down)) to press and grip the forging material W. An upper grip die 32 is detachably fixed to the lower end of the gripping ram 31 with a bolt. A lower grip die 33 is fixed to the gripping mechanism body 5, facing the upper grip die 32. The forging material W is gripped and fixed by gripping recesses 34 formed at the lower end of the grip upper die (movable die) 32 and the upper end of the grip lower die (fixed die) 33. In this example, two sets of gripping recesses 34 are provided, and after the forging material W is gripped by these gripping recesses 34, the head of the forging material W is subjected to the desired upset forging in two steps by the upset die 10 (see FIG. 1) of the horizontal striking press 2.

[0015] The grip ram 31, which has a rectangular cross-section, is inserted into a rectangular ram guide hole 35 formed in the grip mechanism main body 5 and is slidable in the vertical direction (x-axis direction). Forced lubrication is applied between the grip ram 31 and the ram guide hole 35, allowing the grip ram 31 to slide smoothly in the vertical direction (x-axis direction). A hydraulic cylinder chamber 36, which is a cylindrical hole, is formed at the upper end of the grip ram 31. A piston 40 is inserted into the hydraulic cylinder chamber 36 and is slidable in the vertical direction (x-axis direction). This piston 40 is hydraulically driven. Pressurized oil is introduced into the hydraulic cylinder chamber 36 to drive the grip ram 31 in the x-axis direction (downward). The lower end of a piston rod 41 is connected and fixed to the piston 40 so that they are integral with each other. The upper end of the piston rod 41 is fixed with bolts to a lower plate 51 of a rectangular metal case 50, which has a roughly box-shaped outer shape.

[0016] The square metal case 50 has an upper plate 52 parallel to a lower plate 51, and the lower plate 51 and upper plate 52 are connected and fixed by four bolts 53. A spacer 54, which is a tubular material, is interposed between the bolts 53 to maintain the distance between the lower plate 51 and the upper plate 52. A cubic (approximately regular hexahedron) space is thus formed between the lower plate 51 and the upper plate 52, and a rectangular parallelepiped square metal 60 is disposed in this cubic space. The square metal 60 can move (slide) only in the y-axis direction within the square metal case 50 (see FIG. 2). A circular through-hole 61 is bored in the center of the square metal 60. A crankshaft 62 is inserted into and supported in this circular hole 61 so as to be rotatable. As shown in FIG. 3, the crankshaft 62 has support shafts 63 integrally formed on both sides. The support shafts 63 on both sides of the crankshaft 62 are rotatably supported by bearings on the side plates 55 of the square metal case 50. The center line of the support shafts 63 and the center line of the crankshaft 62 do not coincide with each other and are eccentric (see FIG. 2).

[0017] A crank drive gear 65 is fixed coaxially to one of the support shafts 63. A pinion gear 66 meshes with the crank drive gear 65. The pinion gear 66 is fixed to the output shaft 67 of an AC servo motor 68 with a key or the like. Therefore, when the AC servo motor 68 is started to rotate the pinion gear 66, the support shaft 63 is rotated, and the crank shaft 62, which is eccentric with the support shaft 63, is also rotated. When the crank shaft 62 is rotated, the square metal 60, which is rotatably supported on the crank shaft 62 between the lower plate 51 and the upper plate 52 of the square metal case 50, drives the grip ram 31 up and down (x-axis direction), but only slides within the square metal case 50 left and right (y-axis direction) in FIG. 2 . In other words, the grip ram 31 is not driven up and down (FIG. 2 ). When forging a forging material W in the horizontal striking press 2, the grip ram 31 is driven downward (x-axis direction) to grip and fix the forging material W between the grip upper die 32 and the grip fixing die 33.

[0018] [Controller 70] FIG. 4 is a block diagram showing an overview of the upset forging system controller 70 for controlling the upset forging system 1. The controller 71 of the upset forging system controller 70 is a programmable logic controller (PLC), a known general-purpose control means for sequentially controlling various machines, including a central processing unit (CPU), RAM, ROM, auxiliary storage device, display means, input means, and various output means. A position signal is sent to the controller 71 from a grip ram position sensor 73 via an interface (I / F) 72. The grip ram position sensor 73 detects the positions of the grip ram 31 and the grip ram lower die 33 integrated therewith. In this example, the grip ram position sensor 73 is specifically a rotary encoder that detects the rotation of the AC servo motor 68. Note that this sensor may be a proximity sensor or the like that directly detects the position of the grip ram 31 or the grip ram lower die 33 integrated therewith, instead of a rotary encoder.

[0019] In addition, a header ram position signal is sent to the control device 71 from a header ram position sensor 74 via an interface (I / F) 72. The header ram position signal sensor 74 acquires the header ram position of the horizontal striking press 2. Specifically, it detects the rotation of the crank mechanism of the horizontal striking press 2 to detect the position of the header ram. The control device 71 controls the start and stop of the rotation of the AC servo motor 68 that drives the gripping mechanism 3 via an interface (I / F) 75 based on data from the above sensors. The control device 71 also controls the supply of pressurized oil to the hydraulic cylinder chamber 36 using a solenoid valve 76. Furthermore, the control device 71 controls the stopping, driving, and timing of the header ram (upset die 10) by turning on and off a clutch and brake 77 of the horizontal striking press 2.

[0020] [Overview of Operation of Upset Forging System 1] An overview of upset forging operation by the upset forging system control device 70 will now be described. The upper diagram in FIG. 5 is a diagram illustrating the stroke operation of the grip ram 31. The middle diagram in FIG. 5 is a time chart illustrating the timing of supplying hydraulic pressure to the hydraulic cylinder chamber 36 of the grip ram 31 via the solenoid valve 76. The lower diagram in FIG. 5 is a diagram illustrating the stroke operation of the header ram (upset die 10) of the horizontal striking press machine 2. The forging material W is set in the grip lower die 33 by the workpiece loading / unloading robot 4. Once the forging material W is set, the AC servo motor 68 of the grip mechanism 3 is activated to rotate the crankshaft 62 (180 degrees) and lower the grip ram 31. The grip upper die 32, which is integral with the grip ram 31, descends to grip and fix the forging material W between the grip lower die 33 (solid lines in the upper diagram in FIG. 5).

[0021] After the grip ram 31 begins to descend, the solenoid valve 76 for supplying hydraulic pressure to the hydraulic cylinder chamber 36 is opened. When the grip ram 31 reaches bottom dead center, the AC servo motor 68 is stopped. Before the grip ram 31 reaches bottom dead center, the solenoid valve 76 for supplying pressurized oil to the hydraulic cylinder chamber 36 is opened. After the grip ram 31 reaches bottom dead center, the pressurized oil in the hydraulic cylinder chamber 36 reaches a set pressure (middle part of Figure 5). As a result, the upper grip die 32 and the fixed grip die 33 grip the forging material W not directly via the crank mechanism but via pressurized oil. Therefore, if any trouble occurs and the pressurized oil exceeds the set value, a relief valve (not shown) is activated to prevent overload. This absorbs manufacturing errors, gripping errors, etc., of the upper grip die 32 and the lower grip die 33, allowing them to be tightly attached at the set pressure, thereby preventing damage to the dies.

[0022] Once the set pressure is reached, the clutch and brake 77 of the horizontal striking press 2 is turned on, driving the header ram in the y-axis direction to perform upset forging (lower part of Figure 5). After the crank mechanism of the horizontal striking press 2 rotates once (360 degrees), the clutch and brake 77 is turned off, stopping the header ram. After the header ram reaches bottom dead center, the solenoid valve 76 is opened to return the pressure oil. After this, the AC servo motor 68 is started, and the grip ram 31 is raised. In other words, the upper grip die 32 gripping the forging material W is raised and released from its grip on the forging material W, completing one forging process.

[0023] [Other Embodiments] The horizontal striking press 2 described above drives the head ram horizontally, but depending on the type of upset forging, it may be a press machine driven vertically. Furthermore, while the horizontal striking press 2 is a crank mechanism using a connecting rod that converts rotary motion into linear motion with a crank, it may also be a lever press or knuckle press, as long as it is a mechanism. Similarly, the grip mechanism 3 is a crank mechanism known as a Scotch yoke type, but it may also be a crank mechanism using a connecting rod, a lever press, or a knuckle press. Therefore, the crank mechanism referred to in the present invention is a concept that includes these mechanisms.

[0024] DESCRIPTION OF THE SYMBOLS W...Forging material 1...Upset forging system 2...Horizontal striking press 3...Gripping mechanism 4...Workpiece loading / unloading robot 5...Gripping mechanism body 10...Upset die 31...Grip ram 32...Upper grip die 33...Lower grip die 34...Gripping recess 35...Ram guide hole 36...Hydraulic cylinder chamber 40...Piston 41...Piston rod 50...Square metal case 51...Lower plate 52...Upper plate 53...Bolt 54...Spacer 55...Side plate 60...Square metal 61...Circular hole 62...Crankshaft 63...Support shaft 65...Crank drive gear 66...Pinion gear 67...Output shaft 68...AC servo motor 70...Upset forging system control device 71...Control device 72, 75...Interface (I / F) 73...Grip ram position detection sensor 74...Header ram position detection sensor 76...Solenoid valve 77...Clutch and brake for horizontal press

Claims

1. An upset forging system using an upsetter comprising: a press machine for performing upset forging; a grip die which grips a portion of the forging material when performing the upset forging, the grip die consisting of a fixed die and a movable die; a crank mechanism which drives a grip ram which drives one of the movable dies of the grip die in a linear direction; a servo motor which rotates and drives the crank mechanism; a detector which detects the position of the movable die; and control means which controls the press machine and the grip die, wherein the control means operates the press machine to perform the upset forging in response to a position signal from the detector.

2. A grip control method for upset forging as described in claim 1, characterized in that, in order to limit the gripping pressure of the gripping die, the gripping force with which the movable die presses the fixed die is limited to a set value or less via hydraulic pressure when the movable die is at its bottom dead center.

3. A grip control system for upset forging comprising: a press machine for performing upset forging; a grip die which grips a portion of the forging material, which is divided into a fixed die and a movable die, when performing the upset forging; a crank mechanism which drives a grip ram which drives one of the movable dies of the grip die in a linear direction; a servo motor which rotates and drives the crank mechanism; a detector which detects the position of the movable die; and a control device which detects the position of the movable die and operates the press machine to perform upset forging.

4. A grip control system for upset forging as described in claim 3, characterized in that it comprises a hydraulic cylinder device that limits the gripping force with which the movable die presses the fixed die to a set value or less when the movable die is at its bottom dead center, in order to limit the pressure applied during the press forming process.

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