JPH0246292B2 - ONKANATSUZOKINONTENHOHO - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of operating a warm heading machine.

Steel rod for prestressed concrete (hereinafter referred to as PC)
In many cases, a steel bar (called a steel bar) has a button head formed at one end and is used for locking during tensioning. Conventionally, a warm heading machine, the main part of which is shown in Figure 1, is used to form the button head. It is used. The warm heading machine includes a chuck mechanism 1, an induction heating coil C, and a heading punch 2, and its heading operation is as follows. The forging punch 2, which can move forward and backward in the direction of the arrow a←→b, is advanced in the direction a, and the end face of the tip 21 of the forging punch 2 is heated by the induction heating coil C.
The PC steel rod W shown by the dashed line inside is placed on standby as the position L for heating. PC steel bar W
shows the chuck mechanism 1 in the released state according to arrow d.
The end face of the forging punch 2 collides with the end face of the tip 21 of the forging punch 2, and the forward movement is stopped with the end inserted into the heating coil C as shown by the solid line. Being teased. Above PC
The collision of the steel bar W with the tip 21 of the forging punch is detected by a detection mechanism (not shown), and the chuck mechanism 1 is closed by the detection signal emitted by the detection mechanism and grips the PC steel bar W. do. Next, the forging punch 2 is moved back in the direction of arrow b to position the tip 21 outside the heating coil C as shown by the solid line, and then
A power source (not shown) is turned on and the induction heating coil C is energized for a predetermined period of time. After energization, the forging punch 2 is slowly advanced in the direction a, and the tip 21 of the end of the PC steel bar W is heated to a predetermined temperature, for example, 400 to 450°C.
While the end surface of the tip portion 21 reaches the most advanced position shown by the broken line, warm plastic working is performed to form the button head WH as shown by the broken line. The PC steel rod W with the button head WH formed thereon is carried out with the chuck mechanism 1 released.

By the way, the button head WH is forged by pressing the end face of the PC steel bar W heated to a predetermined temperature with the tip end face of the forging punch 2, so if it is pressed with the cold end 21 of the punch 2, the PC steel bar W is pressed. The temperature of the heated part of the rod is transferred to the tip of the forging punch 2 through the contact surface.
1 due to heat conduction, the end of the PC steel bar that has been heated to a predetermined temperature will drop in temperature, and for example, the shape will be similar to that when cold heading is performed as shown in Figure 2 a. Not only does it become a dumpling shape or an irregular shape as shown in Figure 2b, making the shape and function unsuitable for locking the PC steel bar under tension, but also the button head WH due to the work hardening phenomenon. However, it becomes abnormally hard and causes delayed fracture during use.

Therefore, when the conventional warm heading machine starts operating or is in operation, if the loading of the prestressed steel bar is temporarily interrupted and the heading sequence is continued after being interrupted for a while, the heading punch does not warm up. Until button heads WH are forged into the correct shape, those formed in incorrect shapes are discarded as trial shots, and the number of discarded buttons is 4 to 6, depending on the temperature and the temperature of the PC steel bar. This also sometimes extended to books, which was uneconomical. Furthermore, when restarting the forging sequence after an interruption, it is necessary to constantly monitor whether trial hammering is necessary or not, and which parts of the forging sequence are required to be discarded. Even if the head-forming machine was mechanically automated, complete labor savings could not be expected.

The present invention has been made in order to solve the above-mentioned problems existing in conventional warm heading machines. The present invention provides a method of operating a warm heading machine that is fully automated or does not require supervisory personnel.

The technical idea of the present invention can be summarized as follows. That is, (1) Conventionally, a heat source dedicated to preheating has been used to preheat general molds and dies, but in the present invention, the induction heating coil that heats the end of the PC steel bar, which is the workpiece, is used in the forging punch. Diverted to compensation heating.

(2) The above-mentioned compensation heating is performed by setting the above-mentioned constant temperature to the saturation temperature indicated by the tip of the forging punch during the continuous forging sequence so that the forging punch always maintains a constant temperature from the start of operation to the end of operation, and performs forging. If the temperature at the tip of the forging punch has fallen below the saturation temperature or the permissible temperature range, appropriate compensation heating is performed to bring the entire cross section to a substantially uniform saturation temperature.

(3) operating the warm heading machine by a control device including a central processing unit in order to perform appropriate compensatory heating corresponding to the degree of temperature drop at the tip of the heading punch;
Comparing the time difference between the preceding forging sequence and the following forging sequence, that is, the elapsed time, with a preset predetermined time required for the forging punch to naturally cool to the lower limit of the temperature at which a normally shaped button head can be formed; If the subsequent forging sequence is to be performed after a predetermined time has elapsed, prior to execution of the forging sequence, appropriate electricity is applied to the induction heating coil selected depending on the magnitude of the elapsed time exceeding the predetermined time. .

(4) In this case, the induction heating coil originally designed for heating the end of the PC steel bar will be used to heat the forging punch, so the heating conditions will be changed, and the predetermined time will be The temperature of the forging punch, which decreases in temperature differently depending on the elapsed time, is heated up to the saturation temperature, so the temperature of the forging punch is increased by an output that is unrelated to the power output when heating the end of the PC steel bar. The time required for the temperature to drop from the saturation temperature to almost normal temperature through natural cooling is divided into multiple time periods, and each time period is divided into multiple periods, each with a specific energization time that is repeated multiple times with a predetermined energization stop time in between. The temperature of the forging punch, which has been lowered due to this, is restored to the saturation temperature by setting in advance the energization cycle time that enables uniform heating of the entire cross section, and selecting the appropriate energization cycle time from among these multiple energization cycle times. The purpose is to carry out compensatory heating.

There are various ways in which compensation heating can be executed.
All of this is based on the above technical idea.

In making the present invention, the present inventor first used a conventional temperature heading machine and analyzed the temperature change at the tip of the heading punch when the machine was started and the heading cycle was performed continuously. Immediately before pressing the end of the heated PC steel bar, the temperature measurement operation of contacting the center of the end face of the tip of the forging punch with a contact type temperature measuring device was repeated sequentially from the start, and the temperature measurement value was plotted on the vertical axis. The temperature characteristic curve A shown in FIG. 3a was obtained by plotting the number of pressed button heads on the horizontal axis. The warm heading machine used was a 7.4mm PC.
It was of a type in which the button head was forged onto a steel rod. As shown in Figure 3a, the temperature of the forging punch rose sharply from the start of operation when the number of punches pressed was about 20 or more.
The temperature remained almost constant at around 230℃, confirming the saturation temperature of the forging punch. It was also confirmed that the temperature of the forging punch was 150°C or higher for the forged button head to have a normal shape.

The inventor of the present invention further measured the temperature of the forging punch after the above-mentioned warm heading machine was stopped due to natural cooling from its saturation temperature by using a contact temperature measuring device attached to the end face of the forging punch. A temperature characteristic curve B shown in FIG. 3b was obtained by plotting the measured temperature value on the vertical axis and the elapsed time on the horizontal axis. It was confirmed from FIG. 3b that after 60 seconds or more passed, the temperature of the forging punch decreased to 150° C. or lower due to natural cooling, at which point a button head with a normal shape could not be formed.

The inventor of the present invention recognized through the above analysis that the cooling rate of the forging punch is relatively rapid, and set the compensatory heating temperature of the forging punch in order to allow enough time for the introduction of the PC steel bar in the previous and subsequent forging cycles. The saturation temperature was set to be sufficiently higher than the temperature at which a normally shaped button head can be formed.

The saturation temperature is determined by the diameter of the forging punch, which varies depending on the diameter of the PC steel bar, or the length of the forging cycle time, and is not limited to the experimentally measured value.

Next, the present inventor discovered that the purpose of the present invention is to convert the induction heating coil originally used for heating the end of a PC steel bar to uniformly heat the tip of the forging punch to the saturation temperature over the entire cross section. A method for achieving proper heating by overcoming the differences in temperature, the difference in the distance between the induction heating coil and the object to be heated, and other different factors was set up as follows.

In other words, the power output that energizes the induction heating coil is
A predetermined output (for example, 50%) that is different from the output when heating the end of the PC steel bar is applied, and the energization is divided into multiple times, so that the surface layer of the forging punch that is heated during energization is transferred toward the center by heat conduction when the energization is stopped. The entire cross section is heated to a uniform temperature.

To determine how to set the bullet cycle time, which consists of multiple repetitions of energization and cessation of energization, the following calculation formula that expresses the temperature rise and cooling of the object in a macroscopic manner was used.

When temperature rises During cooling However, T _c = C _e /A・h; Time constant θ _n = θ/A・h; Temperature at t→∞ (℃) θ; Temperature difference with outside air (℃) θ ₀ ; Initial temperature difference (℃) C _e ; heat capacity of the object (J/℃) A; heat radiation area of the object (cm ² ) h; heat radiation coefficient (W/cm ²・℃) Q; amount of heat supplied (W) t : time (sec) By the way, time The constant T _c is an eigenvalue of the object including shape, material, surrounding conditions, etc., and θ _n is also an eigenvalue when the heating conditions (excluding time) are constant. Therefore, the cooling curve equation B' obtained by regression analysis of the temperature measurement data during cooling of the forging punch shown in Fig. 3b is Therefore, the time constant T _c becomes T _c =175, so for example, the energization cycle shown in Fig. 4
As shown in the time chart, thsec current heating, 5sec
In the case of energization pause ts cooling, thsec energization heating, 5sec energization pause ts cooling, and _thsec energization heating, the above formula (1) and By repeatedly calculating equation (2), it is possible to determine the temperature of the forging punch at the end of the energization cycle time represented by θ ₁ to θ ₃ .

For example, for the device used in the above temperature measurement experiment, θ _n
= 5000, T _c = 175, θ ₃ ≒ 230°C, the cooling curve of the forging punch, th in the energization cycle with 3 energization times of th time sandwiched by 2 5 sec energization stop times, and the end of the energization cycle. Figure 5 shows the temperature relationship at the time.

In Figure 5, the horizontal axis represents the forging operation pause time, the vertical axis represents the temperature of the forging punch, and the time for one energization th.
Curve B is 230 when the forging punch stops the forging operation.
℃ shows the state of natural cooling over time, curve C shows the change in the required energization time th depending on the temperature state of the forging punch, and curve D shows the state of cooling of the forging punch depending on the cooling state of the forging punch. The temperature of the forging punch obtained by the energization cycle time is shown.

From the relationship diagram shown in Figure 5, in this case, for example, if the forging cycle to be executed is 2 mm after the preceding forging cycle, the energization cycle time consisting of the energization time th of 2.1 sec is set before the forging cycle. The temperature of the forging punch is compensated by heating to the saturation temperature, and the energization time is 3.25 seconds when 10 mm or more has elapsed or when starting operation.
It can be seen that it is sufficient to carry out the forging cycle after implementing the energization cycle time consisting of th.

Based on the relationship diagram above, the inventor has determined that, for example, 60 seconds is the predetermined time, and the elapsed time exceeding the predetermined time is 30 seconds.
The power-on time is divided into multiple time periods.
The energizing time is calculated by sandwiching the predetermined energizing stop time with different th.
The energization cycle time consisting of the content of repeating th multiple times is set, and this is stored in the storage area of the central processing unit. A comparison is made to see if the elapsed time between cycles does not require compensation heating...for example, within a predetermined time, which is 60 seconds in this case, and if it is within a predetermined time, execution of the subsequent heading cycle is performed. If the specified time has been exceeded,
The current supply cycle time corresponding to the elapsed time exceeding the predetermined time stored in the storage area is configured to be executed prior to execution of the forging cycle.

This will be explained with reference to the flowchart and front view of the main parts of the apparatus shown in FIGS. 6a and 6b.

Before starting the operation of the warm heading machine, initial settings are first performed, and the clearing operation command of the warm heading machine is issued from the central processing unit...PC steel rod (hereinafter referred to as work W).
) discharge operation command is output to the control device,
Next, "selection of energization cycle time" for compensating and heating the forging punch is performed, and an execution command for "forging punch compensation heating operation" is output to the control device.
The above-mentioned "selection of energization cycle time" is set so that the energization cycle in which the energization time th in FIG. 5 is the maximum is obtained. By the above-mentioned "heading punch compensation heating operation" command, the forging punch 2, whose end surface of the tip 21 was set at the position for positioning the workpiece W shown as L in FIG. 6b, is moved to the compensation heating position H within the induction heating coil C. The tip 21 of the forging punch 2 is thereby heated uniformly over the entire cross section to the saturation temperature. Upon completion of the compensation heating program, the central processing unit performs a "TIMER-RESET" to complete the forging sequence and start counting the elapsed time until the expected arrival of the forging sequence start detection signal is input. Then, a "heading punch return operation" command is output to the control device, and the forging punch 2 returns to the workpiece positioning position L to wait for the arrival of the workpiece W.

When the warm heading machine is equipped with a loading/unloading mechanism 3 shown as 3 in FIG. 6b and consisting of, for example, a walking beam, the workpiece W that reaches the processing line P by the stepping motion of the walking beam 3 is By rotating the feed rollers 31, 31 in a predetermined direction, the chuck mechanism 1 of the warm heading machine is moved in accordance with the arrow d.
Carry-in begins in the direction. walking beam 3
A detection mechanism 32 is provided at a predetermined position along the workpiece movement line of the processing line P. For example, when the workpiece W starts moving forward to be carried into the warm heading machine, the detector 321 opens the contact 322. , and continues to maintain the open state during conveyance, and when the forging cycle is completed and returns to the processing line P of the walking beam 3 by rotating the feed rollers 31, 31 in the opposite direction, the contact 322 is opened. When the detection mechanism 3 is opened, the carry-in detection signal is output as a "work confirmation" judgment, and when the detection mechanism 3 is closed, the carry-out detection signal is output as a "TIMER-RESET" signal. Each is set to be input to the central processing unit.

Therefore, the operation of the warm heading machine is started, the compensatory heating of the heading punch is completed, and "TIMER-
When the carry-in detection signal is input to the central processing unit while the clock is in progress after the carry-in signal has been reset, the central processing unit determines that ``work confirmation'' is YES, and the elapsed time up to the time when the carry-in signal is input is stored in the memory. compared with the predetermined time. As a result, if it is determined that the elapsed time is within the predetermined time, the workpiece W is allowed to be carried into the apparatus, and a "forging operation" execution command is output to the control device. As a result, a normally shaped button head is formed at the end of the workpiece W according to a predetermined sequence.

The workpiece W on which the button head has been formed is moved to the roller 3.
1 and 31, the walking beam returns to the processing line P, but as a result, the detector 321 of the detection mechanism 3 closes the contact 322, so an unloading detection signal is output, and the central processing "TIMER-RESET" is performed in the device, and the arrival of the subsequent workpiece W carry-in detection signal is waited for. In this way, the warm heading machine continues processing the workpieces W that are successively brought in.

After the compensation heating is performed at the start of operation of the warm heading machine or during operation, for example, the walking beam 3
If the above-mentioned time measurement progresses due to a delay in the supply of the work W to the forging sequence, and the forging sequence start detection signal is input after a predetermined period of time has elapsed, the central processing unit issues an operation command to prevent execution of the forging sequence, that is, the walking beam 3 A "temporary stop of work loading" command is output to stop the rotation of the rollers 31, 31, and then a predetermined "compensation heating process" including the energization cycle time selected based on the clearing operation command and the elapsed time exceeding the predetermined period is output. The "execute" command is output to the control device, and the "temporary stop of work W carry-in" command is canceled upon completion of compensatory heating of the forging punch, and the forging sequence is executed.

When carrying the workpiece W into the warm heading machine manually, as shown in FIG.
A predetermined voltage is always applied to the end face of the tip portion 21, and the end face of the tip portion 21 is kept waiting at the position L for positioning the workpiece W, and the end face of the workpiece W inserted from the passage of the chuck mechanism 1 in the open state is placed at this position. For example, a detection mechanism consisting of an electromagnetic switch RY and a step-down transformer TR is provided to detect a collision and a ground fault, and the output of the detection mechanism is input to the central processing unit as a forging sequence start detection signal. The end of the sequence program is treated as the end of the forging sequence, and "TIMER-RESET" is performed. If the forging sequence start detection signal is input after a predetermined period of time and the operation command to prevent the execution of the forging sequence that is output to perform compensation heating of the forging punch is The chuck mechanism moves the workpiece W forward in one direction, and the workpiece W is ejected from the heating position by this action.

By implementing the present invention, there is no need to test a single warm heading machine, and there is no need to forge defective products, and homogenization of products is achieved, as well as true unmanned manufacturing lines. This will result in a reduction in the number of monitoring personnel, which will have a significant effect.

[Brief explanation of drawings]

Fig. 1 is a partially sectional front view showing the main parts of a conventional warm heading machine, Figs. 2 a and b are front views showing an example of an irregularly shaped button head forged by the conventional warm heading machine, and Figs. 3 a and b are respectively Figure 4 is a temperature characteristic curve diagram that analyzes the temperature rise due to the start of the continuous forging sequence of the forging punch performed using a conventional warm heading machine and the temperature decrease due to natural cooling after the forging sequence is stopped. FIG. 5 is a time chart showing an example of the energization cycle time when compensatingly heating a forging punch. Diagrams showing an example; FIGS. 6a and 6b are a flow chart and a partially sectional front view of an apparatus showing one embodiment of the present invention, respectively; FIG. 7 is a partially sectional front view showing another embodiment of the present invention. It is a diagram. 1...chuck mechanism, 2...heading punch, 21
... Tip of heading punch, 3 ... Loading/unloading mechanism, 3
2...Detection mechanism, C...Induction heating coil, W...
PC steel rod, WH... button head, L... PC steel bar heating position, th... energizing time, ts... energizing stop time, RY/TR... detection mechanism.

Claims (1)

[Claims] 1. A device comprising a chuck mechanism, an induction heating coil, and a forging punch, the end of a PC steel bar gripped by the chuck mechanism is heated to a predetermined temperature by the induction heating coil, and then pressed by the forging punch to form the end. In a method for operating a warm heading machine for forming a button head on a section, the elapsed time from the end of the preceding heading sequence to the start of the heading sequence is determined prior to the heading sequence to be executed. The forging sequence is compared with a preset predetermined time, and if the elapsed time is within the predetermined time, the forging sequence is executed immediately, and if the elapsed time exceeds the predetermined time, the tip of the forging punch is A method for operating a warm heading machine, characterized in that the forging sequence is executed after compensating heating is performed to the saturation temperature indicated by the forging punch during the continuous forging sequence using an induction heating coil. However, the preset predetermined time is the time required for the temperature of the forging punch to drop from the saturation temperature to the lower limit temperature at which a normally shaped button head can be formed by natural cooling. 2 Equipped with a chuck mechanism, an induction heating coil, and a forging punch, the end of the PC steel bar gripped by the chuck mechanism is heated to a predetermined temperature by the induction heating coil, and then pressed by the forging punch to form a button head at the end. In a method for operating a warm heading machine that is operated by a control device including a central processing unit, when starting the operation of the warm heading machine, turning on power to the power source of the induction heating coil in the initial setting is performed on the heading punch. A compensatory heating signal is input to the central processing unit, and the central processing unit outputs a compensatory heating execution command according to a preset program to the control unit, whereby the forging punch is placed at a predetermined position in the induction heating coil. is displaced and the power output is changed to a predetermined output, and then the induction heating coil is energized for a predetermined cycle to bring the tip of the forging punch up to the saturation temperature indicated by the forging punch during a continuous forging sequence. At the same time as compensatory heating, the system starts measuring the elapsed time until the forging sequence start detection signal is input, which is expected to arrive as an end detection signal to detect the end of the preceding forging sequence with the end of the compensatory heating program. A method of operating a warm heading machine characterized by: 3 Equipped with a chuck mechanism, an induction heating coil, and a forging punch, the end of the PC steel bar gripped by the chuck mechanism is heated to a predetermined temperature by the induction heating coil, and then pressed by the forging punch to form a button head at the end. In a method for operating a warm heading machine that is operated by a control device including a central processing unit, a detection mechanism is provided that detects the start and end of a forging sequence of the warm heading machine and outputs a detection signal; The detection signal of the mechanism is input to the central processing unit, and the central processing unit calculates the elapsed time from the time when the detection signal is input to detect the end of the preceding forging sequence to the time when the detection signal is input to detect the start of the next forging sequence. Comparing it with a predetermined time set and stored in advance, if the elapsed time is determined to be within the predetermined time, a forging sequence execution command is output to the control device, and the forging sequence is thereby executed. However, if it is determined that the elapsed time exceeds a predetermined time, it outputs an operation command to the control device to prevent execution of the forging sequence, and
Selecting an appropriate energization cycle time from among a plurality of different energization cycle times set and stored in advance according to the magnitude of the elapsed time exceeding the predetermined time,
Outputs an execution command to the control device to carry out compensatory heating of the forging punch according to a preset program, including energizing the induction heating coil according to the appropriate energization cycle time, thereby moving the punch to a predetermined position within the induction heating coil. The forging punch is displaced and the power output of the induction heating coil is changed to a predetermined output, and then the induction heating coil is energized according to the selected appropriate energization cycle time, and the tip of the forging punch is is compensated and heated to the saturation temperature indicated by the forging punch during the continuous forging sequence, and the end of the compensatory heating program is used as an end detection signal to detect the end of the preceding forging sequence, and the start of the forging sequence that is scheduled to arrive is detected. A method for operating a warm heading machine, characterized in that a clock is started to measure the elapsed time until a signal is input. 4. When the prestressed steel bar is carried in and out of the warm heading machine using a carry-in/out device, the forging sequence start detection signal and end detection signal shall be transmitted from the above-mentioned carry-in/discharge device for the prestressed steel bar to the warm heading machine. This is the output of the detection mechanism that detects the start of the loading/unloading operation to the machine and the end of loading/unloading from the warm heading machine to the loading/unloading device. When it is determined that the elapsed time until the start detection signal is input exceeds a predetermined time, the central processing unit outputs an operation command to the control device to prevent the execution of the forging sequence, and the loading operation stop command of the loading/unloading device is used. The method of operating a warm heading machine according to claim 3, wherein the carrying-in operation stop command is canceled upon completion of the compensation heating. 5 When loading and unloading the PC steel rod into the warm heading machine is carried out manually, a predetermined voltage is always applied to the forging punch, and the PC steel rod is placed on the tip end face of the forging punch that is waiting at the positioning position. The output of the detection mechanism that detects a ground fault due to collision of the tip end face of the forging sequence is used as the start detection signal of the forging sequence, and the end of the forging sequence program is used as the end of the forging sequence, and the end detection signal of the preceding forging sequence is input. An operation command to prevent the execution of the forging sequence that is output from the central processing unit to the control device when it is determined that the elapsed time from time to the time when the next forging sequence start detection signal is input exceeds a predetermined time.
4. The method of operating a warm heading machine according to claim 3, wherein the action of discharging the PC steel bar consists of advancing the heading punch at the positioning position toward the chuck mechanism.