JPH03216300A - Plastic working method - Google Patents

Abstract

PURPOSE:To enable high accuracy plastic working by controlling the forwarding speed of a punch so that the rate of strain of a blank is materially uniform nearly all over the plastically worked area of the blank. CONSTITUTION:The deflection of a die 11 in time of plastic working is produced by the stress generated in the blank 12 based on the forming pressure given from the punch 9 to the blank 12. Accordingly, when the forwarding speed of the punch 9 is controlled so that the stress generated by the forming pressure is materially uniform nearly all over the plastically worked area, the deflection of the die 11 in time of plastic working is uniformized. As a result, when a fixed amount of deformation is given to the die 11 as a previously expected allowance of deformation, a high accuracy formed part can be obtained by plastic working only without finish working by post treatment.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a plastic working method using a press machine. In particular, the present invention relates to a plastic working method that prevents deterioration of product precision due to die deformation during plastic working.

[Conventional technology]

Generally, in plastic working using press equipment,
For the blank set in the guide. A force that can cause plastic deformation caused by crank motion or link motion is applied via a punch. Obtain a product with the desired shape.

[Problems to be solved by the invention]

however. In the case of such conventional plastic working, especially cold forging which applies enormous pressure, sufficient forming accuracy cannot be obtained by plastic working alone for the following reasons. Currently, in the case of products that require a high degree of forming precision, the product must be finished by post-processing after plastic working. The first thing to consider is... This is the deformation of the die during plastic working. During plastic working. The force applied from the punch to the blank is also transmitted to the die as stress6. Therefore, since it is impossible for the die to have rigidity in an absolute sense, deformation of the die will not occur during plastic working. This is difficult to avoid, and especially in the case of equipment that applies enormous pressure, such as a cold forging press, the deformation of the die is also large. If the deformation of the die that occurs during processing occurs uniformly over the entire area of plastic processing. It is possible to provide a die with a deformation allowance to account for the deformation of the shape, but in the conventionally known general plastic working, the amount of deformation of the die during processing fluctuates unpredictably from moment to moment. ．． Even if a deformation allowance is provided, improvement in machining accuracy cannot be expected. What can be considered is the impact when a single punch collides with the blank. In other words, in the case of a crank press or a link press, the punch has a large descending speed when it comes into contact with the blank. Instantly, a huge impact is applied to the blank. This impact causes the shape of the goo to become thick and deformed, deteriorating machining accuracy. There are two more things I can think of. This is Dai's spring bar knock at the time of knockout. In other words, enormous forming pressure is applied to the die during plastic working. This molding pressure is transmitted and the die is also deformed. and. During knockout, the molding pressure is released as the punch separates, so the die returns to its initial shape due to its own elasticity. Damage is added to the product that is non-quoted.

[Means to solve the problem]

The present invention was made in view of these problems, and
The purpose of the present invention is to provide a plastic working method with improved processing accuracy so that sufficient product accuracy can be obtained without post-processing. To summarize, the plastic working method of the present invention includes: a punch that can be raised and lowered and a die to which nine blanks are attached. A plastic processing method is assumed in which the shape is deformed by applying pressure that causes plastic deformation to the blank attached to the die through the punch using a plastic processing device that can control the movement speed of the punch in the work area. 2. Fundamentally, the advancement speed of the punch is such that the strain rate of the blank due to the pressure applied through the punch is substantially uniform throughout the plastic working of the blank. The present invention is characterized in that the blank is plastically worked while controlling. or. Desirably, the plastic working method of the present invention includes: lowering the punch at a slow speed until its tip comes into contact with the blank, and with the punch in contact with the blank, plastic deformation occurs in the blank through the punch. It is characterized in that the plastic working is performed by applying the above-mentioned forming pressure after applying a pressure of no limit.Furthermore, preferably, the plastic working direction of the present invention is: After processing, the blank is non-knocked out from the die while applying forming pressure.

[Effect]

Die deflection during plastic working is caused by the stress generated within the blank due to the forming pressure applied to the blank from the punch. Therefore. If the forward speed of the punch is controlled so that the stress generated by the forming pressure is substantially uniform over the entire area of plastic working, the deflection of the die during plastic working will be uniform. If the stress generated in the blank is defined as σ and the amount of strain in the blank is defined as ε, then (Equation 1) generally holds true between the strain rate i and the stress σ. σ=kru @ (Formula 1) where: k is a constant and strain rate sensitivity index i = dε/dL In this (Formula 1), the only real variable is the strain rate. If the pressurization rate is controlled so that the strain rate is constant, the stress σ becomes constant, and the deflection of the die can be made uniform over the entire plastic working area. or. When a punch that is descending at high speed collides with the blank. The die is also significantly deformed due to the momentary large impact applied to the blank. Also, even if pressure is suddenly applied from the punch to the blank while the punch is in contact with the blank and stopped. It is difficult to quickly increase the pressurization speed to the ideal speed. However, like the present invention. If the punch is lowered slowly until it contacts the blank, deformation of the die due to the impact at the time of collision is prevented. In addition, if plastic pressure is applied to the blank through the punch in this contact state to a limit that does not cause plastic deformation, the pressing speed can be increased more quickly to the ideal speed. Fluctuations in the amount of die deformation can be suppressed. Furthermore. If, as in the present invention, the blank is knocked out from the gou with forming pressure applied after plastic working, the springback of the die will not occur until the product escapes from the goo. Damage to molded products due to springback can also be avoided.

【Example】

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a cold forging press device 1 according to an embodiment of the present invention.
and a block diagram of its control system. A besoto 3 and a cylinder fixing plate 4 are fixed in parallel to the frame 2 of the cold forging press equipment l, and a main cylinder 5 is fixed to the cylinder fixing plate 4. A slide 7 is fixed to the lower end surface of the piston 6 of the main cylinder 5. The slide 7 is moved up and down by the piston 6. A punch 9 is attached to the lower end surface of the slide 7 via a fixing member 8. A die l1 is attached to the upper end surface of the besoto 3 via a fixing member 10 directly below the bunch 9,
A blank 12 to be processed is attached to this die 1l. Further, a bank up cylinder l3 that supports the slide 7 is fixed to the upper end surface of the besoto 3, and the piston 14 of the bank up cylinder 13 has a stroke that can reach the lower end surface of the slide 7. Furthermore. A knockout cylinder l5 is fixed to the lower end surface of the bed 3, and the piston of the knockout cylinder l5 is made of a plastically worked blank 12.
It is a counter punch of 16 to non-kout. Next, 20 is a main cpυ21 that performs overall control, sub CPU2223 and 24 that control each control target,
Data CPtJ25 that controls memory data input/output
It is a distributed processing type control device with 26 and 27 are input/output interfaces. 28 is an external output device such as a CTR, and 29 is an external input device such as a keyboard or external memory. In this embodiment, the main cylinder 5 includes a flow control valve 31 that controls the amount of oil flowing into the main cylinder 5.
Pressure control valve 32 that controls the pressure inside the main cylinder 5 by w1m
, a pressure sensor 33 that detects the pressure inside the main cylinder 5
is established. The flow rate control valve 31 and the pressure control valve 32 are controlled by the mm device 20 via drivers 34 and 35, respectively. or. The detection output of the pressure sensor 33 is input to the control device 20 via the amplifier 36. or. The banok-up cylinder l3 is provided with a three-state directional switching valve 37 with high-speed response for switching the direction of oil. The directional control valve 37 is controlled by the control device 20 via a driver 38. or. 39 is a position sensor that detects the vertical position of the slide 7 using photoelectric pulses, and 40 is the position! This is a speed converter that differentiates the output of the sensor 39 and converts it into the operating speed of the slide 7, and is similar to the position sensor 39 and speed converter 4.
The output of 0 is input to the control device 20 via the counter 4l. Further, the knockout cylinder 15 is provided with a pressure control valve 42 for controlling the pressure inside the knockout cylinder 15, and a pressure sensor 43 for detecting the pressure inside the knockout cylinder 15. The pressure control valve 42 is controlled by the controller 20 via a driver 44. Further, the detection output of the pressure sensor 43 is input to the control device 20 via the amplifier 45. Furthermore, 46 is a position sensor that detects the vertical position of the counter punch 1G by photoelectric pulse, and 47 is a position sensor 46.
This is a speed converter that differentiates the output of the counter bunch 16 and transforms it into the operating speed of the counter bunch 16, and the position sensor 46 and speed converter 4
The output of 7 is input to the control device 20 via the counter 48. Next, refer to the characteristic curve in Figure 2 and the flowchart in Figure 3. The operation when upsetting is performed using the device shown in Figure 1 will be explained. The upsetting amount within a minute time is Δh. When the height of the punch 9 after upsetting in a minute time is h, and the height of the punch before upsetting in a minute time is tlo(h(+=h+Δh)), by the upsetting operation of Δh in a minute time, The logarithmic strain 6 generated in the blank 12 is shown by (Equation 2), and its strain rate i is shown by (Equation 3). dt Substituting (Equation 2) into this (Equation 3) and expanding it. (Equation 4) is derived. dt di hh. Here, dho/dt is the amount of change in the height of the lower end surface of the punch 9, that is, the descending (processing) speed of the punch 9. If this is replaced with V, the bunch The descending speed V of 9 is (formula 5)
It is shown as. v=kh−h, (25) Therefore. In the upsetting process, the descending speed V of the punch 9 is set to the height h of the lower end surface of the punch 9. If it is controlled linearly, the strain rate can be kept constant. for example. As shown in curve a in Figure 2, the ideal strain continuity 1
When the curve b in Fig. 2 is set to 6 sec-' (the ideal strain rate 1 varies depending on the material and processing details),
As shown. When the height of the lower end surface of the punch 9 is 50 m, the descending speed of the punch 9 is 300 mm/s.
If the descending speed of the punch 9 is controlled to be 150 mm/s when the height of the lower end surface of the bunch 9 is 251, the ideal strain rate j (
Plastic working can be performed in i-6sec-'). First, prior to the actual processing operation, various data (for example, the position of the slide 7 when the lower end surface of the punch 9 contacts the blank 12, the pressing force at the yield point of the blank 12, the pressure of the slide 7 during the forming process) (pressurization speed, etc.) corresponding to the position is input from the external input device 29. Sennoted by data CPU 2 5. For example, a signal indicating that the blank paper has been completed is sent from a transport device (not shown) to the input interface 2.
When input via 6. The control device 2o is a driver 34
The flow control valve 31 is controlled via the main cylinder 5 to supply oil to the main cylinder 5, and the slide 7 is lowered. At this time, the control device 20 inputs the output of the position sensor 39 via the counter 41 and monitors the descending position of the slide 7. Blank 12 with the lower end surface of punch 9 attached to die 11
When the slide 7 descends until it touches the. Control device 20
controls the directional control valve 37 via the driver 38 to supply oil to the back-up cylinder 13, raise the piston 14, and cause the slide 7 to be supported by the back-up cylinder 13. Slide 7 is the bank up cylinder l
3, the control device 20 confirms that the position of the slide 7 does not change due to the output of the position sensor 39. The pressure in the main cylinder 5 and the bank assop cylinder 13 is increased while controlling the flow rate control valve 3l, pressure control valve 32, and direction switching valve 37. When we know from the output of the pressure sensor 33 that the pressure applied to the blank 12 has increased to just before reaching the yield point of the raw material. The control device 20 controls the directional switching valve 37 to open the backup cylinder l3, and also controls the flow rate control valve 31 to lower the slide 7. The blank 12 is plastically deformed by the punch 9. In addition, in the molding process at this time. The control device 20 has a slide position and speed converter 4 which is the output of the position sensor 39.
Flow control valve 31 while monitoring the pressurization speed which is the output of 0.
By controlling the position of the slide 7, the pressurizing speed V is controlled as shown in curve b in FIG. control so that the desired value is obtained. As a result of this pressurizing operation, the slide 7 naturally descends. Regulation? When the il'J position 20 learns that the slide 7 has reached a predetermined braking point based on the output of the position sensor 39, it controls the directional control valve 37 to operate the bathokamp cylinder 13 to lower the slide 7. Add braking. Thereafter, the slide 7 is lowered to the bottom dead center while controlling the on/off of the directional control valve 37. When it is determined by the output of the position sensor 39 that the slide 7 has reached the predetermined bottom dead center position. The control device 20 is . While monitoring the output of the pressure sensor 43 via the amplifier 45.
The pressure control valve 42 is controlled to increase the pressure in the knockout cylinder 15 until it becomes equal to the pressure in the main cylinder 5. and. When the pressure in the knockout cylinder 15 reaches the pressure in the main cylinder 5 due to the output of the pressure sensor 43, the control device 2o controls the pressure control valve 32 while monitoring the output of the pressure sensor 33 to reduce the pressure in the main cylinder 5. ．． Therefore, the counter punch 16 rises, and the formed blank 12 is eventually punched out from the die l1, but at this time the blank 12 is pressurized between the counter bunch 16 and the bunch 9. The spring bank of the die 11 does not occur until the blank 12 escapes from the die l1. The product will not be damaged by the springback of the 1L die. After the non-knockout is performed in this manner, the control device 20 controls the flow rate control valve 31, the direction switching valve 37, and the pressure control valve 42, respectively. One molding operation is completed by operating the main cylinder 5 to the upper limit position, and operating the banokanop cylinder 13 and non-kout cylinder 15 to the lower limit position. still. The above explanation deals with the case of upsetting forming, but in the case of forward extrusion forming and backward extrusion forming, distortion occurs in the blank only when it passes through a point where the cross-sectional shape of the die is inflected, so the whole forming area is The strain rate can be kept constant if the pressurization rate is kept constant. Furthermore, the above example shows an example in which the present invention is applied to plastic working using a cold forging press, but this is because the present invention essentially improves product accuracy by uniformly controlling the amount of deformation of the die. This is intended to improve the quality of the products. Since die deformation is particularly significant in cold forging presses, only cold forging presses are shown as an example, and the present invention can be broadly applied to plastic working in general.

【effect】

As explained above, according to the present invention. As a result of the fact that the strain rate on the blank remains essentially constant throughout the entire forming process, the stress on the die also remains constant. Therefore, the deformation of the die during molding is also maintained constant. Therefore, if the die is provided with a deformation allowance that allows for this certain amount of deformation in advance, a highly accurate molded product can be obtained only by plastic working without the need for post-processing finishing. or. As in the present invention, if the slide is slowly lowered until the punch contacts the blank, deformation of the die due to the impact at the time of contact is prevented, and deterioration of product precision due to die deformation due to impact is also prevented. Prevented. or. Like the present invention. If you apply pressure just before the yield point determined by the material of the blank while the punch is in contact with the blank, you can quickly increase the pressurizing speed to the desired speed when moving to the forming operation. I can do it. Furthermore, like the present invention. If the knockout operation is performed while maintaining the pressure applied to the blank, the spring bank of the die will not occur until the blank is non-knocked out, so the product will not be damaged by the spring bank of the die, and the accuracy of the molded product will be improved. can contribute.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a cold forging press apparatus and its control system according to an embodiment of the present invention, and Fig. 2 is a characteristic diagram showing the relationship between slide position, strain rate, and pressurization rate. Figure 3 is a flowchart of control operation. 5...Main cylinder
7...Slide 9...Punch If...
・Gui 12...Blank l3...Hasoku Asop cylinder l5...Knockout cylinder

Claims (4)

[Claims] (1) A plastic working device having a punch that can be raised and lowered and a die to which a blank is attached, and in which the movement speed of the punch in a working area can be controlled, is used to move the punch to the blank attached to the die. In a plastic working method in which a shape is deformed by applying pressure that causes plastic deformation through the punch, the strain rate of the blank due to the pressure applied through the punch is substantially constant throughout the plastic working of the blank. A plastic working method characterized in that the blank is plastic worked while controlling the advancing speed of the punch so that the blank is uniformly shaped. (2) A plastic working device having a punch that can be raised and lowered and a die to which a blank is attached, and in which the movement speed of the punch in a working area can be controlled, is used to apply the punch to the blank attached to the die. In a plastic working method in which a shape is deformed by applying pressure that causes plastic deformation through Applying a limit pressure that does not cause plastic deformation to the blank through the blank, and moving the punch forward from the state where the limit pressure that does not cause plastic deformation is applied to the blank, and applying the pressure applied via the punch to the blank. The blank is plastic-worked while controlling the forward speed of the punch so that the resulting strain rate of the blank is substantially uniform throughout the plastic working of the blank. Plastic processing method. (3) A plastic working device having a punch that can be raised and lowered and a die to which a blank is attached, and in which the moving speed of the punch in a working area can be controlled, is used to apply the punch to the blank attached to the die. In a plastic working method in which a shape is deformed by applying pressure that causes plastic deformation through the punch, the strain rate of the blank due to the pressure applied through the punch is substantially constant throughout the plastic working of the blank. The blank is plastic-worked while controlling the forward speed of the punch so that it is uniform, and after the blank is plastic-worked, the blank is knocked out from the die with forming pressure applied. plastic working method. (4) A plastic working device having a punch that can be raised and lowered and a die to which a blank is attached, and in which the moving speed of the punch in a working area can be controlled, is used to apply the punch to the blank attached to the die. In a plastic working method in which a shape is deformed by applying pressure that causes plastic deformation through Applying a limit pressure that does not cause plastic deformation to the blank through the blank, and moving the punch forward from the state where the limit pressure that does not cause plastic deformation is applied to the blank, and applying the pressure applied via the punch to the blank. plastically working the blank while controlling the forward speed of the punch so that the resulting strain rate of the blank is substantially uniform throughout the plastic working of the blank, and after the blank is plastically worked; A plastic working method characterized in that the blank is knocked out from the die while a forming pressure is applied.