JPS6021839B2 - Press machine control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for controlling a press machine that can control the pressing force itself.

[Description of related technology] Conventionally, in the control method of a press machine, for example, a drawing start point and an end point are set for each die used, and the punch is operated by numerical control based on these points.

However, the numerical control methods that have been proposed so far only concern the position and speed of the punch.
The point of simultaneously controlling the pressurizing force in accordance with this has not been taken into account, and therefore, in order to control the pressurizing force, for example, it is necessary to detect the oil supply pressure and perform special control using this detected pressure (Hakama). (See Sekisho 57-52598). However, when a pressure detector is separately provided in this way, a separate control means must be provided, which has the disadvantage of complicating the configuration of the control system.

[Object of the Invention] In view of the current state of numerical control of conventional press machines as described above, the present invention provides a method for controlling a press machine that can control not only the position and speed of the punch but also the pressing force. The purpose is to

[Structure of the Invention] In order to achieve the above object, the present invention uses a cylinder mechanism in which a predetermined amount of liquid flows in and out of the punch drive source of a press machine according to a command value of the movement amount, and The fluctuation in the internal pressure that occurs when a predetermined amount of liquid is accumulated in the internal cylinder of the mechanism is determined in advance as a function of the position of the punch, and the fluctuation in the internal pressure that occurs when a predetermined amount of liquid is accumulated in the internal cylinder of the mechanism is determined in advance as a function of the position of the punch. The amount of liquid accumulated in the cylinder is detected, the detected amount of liquid is substituted into the function to obtain the internal pressure of the cylinder, and this internal pressure is multiplied by the piston area of the cylinder mechanism to calculate the amount of liquid accumulated in the punch. The pressurizing force is determined, and by making the obtained pressurizing force a predetermined value, the pressurizing force of the punch is controlled to a predetermined value.

Therefore, since the pressurizing force of the punch is detected with the above configuration, this pressurizing force can be used for observation and display, or for feeding back the pressurizing force to the pressurizing command signal of the cylinder mechanism. This can be an extremely useful control method for press machines that require precise control of pressurizing force. [Description of Embodiments] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a control system diagram of a press machine for applying the method of the present invention.

Reference numeral 1 denotes a hydraulic servo cylinder device used as a drive source for a press machine, in which a pulse motor la is operated by a pulse signal, and a unit volume of liquid is supplied to the cylinder per unit pulse under the control of the motor la. The piston rod 2 is reciprocated by a control mechanism mainly composed of an integrated servo valve mechanism (for example, a plunger type).

3 is a punch provided at the tip of the rod 2, and 4 is a die provided in correspondence with the reciprocating punch 3. 1 to 4 above constitute a hydraulic press machine controlled by the method of the present invention.

The method of the present invention is carried out by adding a control system as described below to the press machine.

First, the pulse motor la is supplied with a pulse signal corresponding to the amount of movement of the punch 3 together with a rotation direction command signal for the motor la, so that the pulse motor la is rotated forward and backward to move the punch 3 up and down. , a discriminator 6 is connected to a command device 5. 5a is a command value setting section, and 5b is a set value output section.

The command value setting unit 5a can set a command value for the punch position, a command value for its speed, or a pressure force applied to the tip of the punch. The set value output section outputs a drive signal for driving the pulse motor la based on the value set by the setting section. Here, the position and speed of the punch 3 are as follows:
Under certain conditions, it is determined by the number of pulse signals supplied to the motor la or, as appropriate, the number of pulse signals per unit time. However, in actual press work, the pressure required differs depending on the thickness and material of the workpiece, and even for workpieces made of the same material, the required processing pressure differs depending on the type of press work, and the above positions and It is important to obtain the required pressing force according to the speed.

Therefore, in the present invention, a pulse counter 7 is provided to count the pulse signals supplied to the pulse motor la during press operation, and the command speed is determined by making the output of the counter correspond to the time pulse supplied from the oscillator 8 as appropriate. While the speed counter 9 is used for counting, in this embodiment, the frame is provided in contact with the piston rod 2.

The distance pulse supplied from the length device 10 is sent to the distance counter 11.
At the same time, the count value of the counter 7 is subtracted from the count value counted by the distance counter 11, and the difference between the movement amount command value and the actual movement amount is counted by the difference counter 12. The detection section 13 includes a speed detection section 13a, a pressure detection section 13b, and a difference detection section 13c.

The speed detection unit 13a receives a speed signal from the speed counter 9, correlates this signal with the signal from the distance counter 11 to correspond to the punch position, and displays the command speed.
Outputs speed signals for semi-closed feedback. The difference signal detection unit 13c receives the difference signal from the difference counter 12, correlates this difference with the distance signal obtained from the distance counter 11, displays the difference signal corresponding to the punch position, and performs full-closed feedback. Output or output a difference signal for use. Pressure force detection section 13b
receives a difference signal from the difference counter via the difference signal detection section 13c, converts the difference signal into a pressing force, and makes the converted pressing force correspond to the distance signal from the distance counter 11 to correspond to the punch position. Displays the applied force and outputs a signal for feedback of the applied force. By the above chain formation, it becomes possible to detect the pressurizing force of the punch in any press operation in correspondence with the position of the punch.

Examples of detection results are shown in FIGS. 2 to 4.

FIG. 2 is an explanatory diagram of a display of the command speed created based on the detection signal from the speed detection section 13a. The vertical axis shows the commanded speed Vp with the punch position S on the machine axis. As shown in the figure, it is initially accelerated to a high speed value V, and is decelerated to a speed V2 before the aperture start point S, and is then decelerated to a speed V2 before the aperture end point S2.
It is displayed that the machine operates while being further decelerated in the vicinity, and returns to the origin at a speed of V3 after finishing the drawing process.

FIG. 4 shows the state of the deviation (difference) ΔS between the movement command value and the actual movement amount under the same machining as shown in FIG. 2.

The machine axis shows the punch position S, and the vertical axis shows the difference ΔS. As is clear from the comparison with Fig. 2, the difference △S is almost zero in the no-load state, rapidly increases to △S at the aperture start point S, and gradually increases towards the aperture end point S2. 4・
Then, before the throttle end point S2, it suddenly increases again to △S2, and when the throttle pressurization ends, it temporarily reverses in the opposite direction due to the sudden pressure drop in the cylinder, and then immediately becomes zero. .

FIG. 3 displays the detection results of the pressing force of the pressing force detection section 13b created based on the difference ΔS explained in FIG. 4.

First, the cylinder mechanism shown in FIG. 1 has a predetermined rigidity, and therefore its volume is also fixed.

Therefore, the deviation (difference) between the punch movement command value and the actual movement amount
is accumulated in the cylinder of this cylinder mechanism, and this accumulation causes fluctuations in the pressurizing force. Therefore, once the piston position inside the cylinder (not shown) is determined, the difference △
By the value of S. The pressing force will also be determined. and,
The relationship between this difference ΔS and the pressing force can be determined as a characteristic value of the cylinder mechanism, and can also be determined experimentally. As shown in FIG. 3, the pressurizing force is, of course, zero when there is no load, but it rises rapidly at the starting point of throttling, and the pressurizing force becomes F.

After that, it breaks down and remains in a sliding state for a while, and drawing processing is performed. Then, as soon as it approaches the end point S2 of the drawing process, it suddenly rises and the pressing force is F.
It is detected as follows. The pressure F3 is, for example, a pressure value indicative of a dangerous area determined as being likely to damage the workpiece. An additional example of feedback control of the pressing force using the pressing force detected by the detection section 13b is as follows. Now move the punch 3 from the minimum stroke position to the starting point S.
,, Next, when moving toward the aperture end point, the pressurizing force is irrelevant (always zero) for movement from the minimum stroke position to the vicinity of the aperture starting point S, so the pressurizing force does not necessarily depend on this section. No feedback required.

Therefore, regarding this section, normal position or speed feedback may be performed, or open loop operation may be performed by simply specifying a predetermined speed. however,
For example, in press work such as drawing, a predetermined pressure control is required during the process.

Therefore, feedback control of the pressing force is performed from near the drawing start point S. In the above embodiment, since the pressurizing force is currently detected by the pressurizing force detection section 13b, feedback control can be performed using this detected value in a normal feedback control method. In addition, during work, there may be other objects in the workpiece,
If the materials and thicknesses are significantly different, this will result in a change in the pressing force and will be detected and displayed on the detection unit 13, so that defective products can be detected during processing, and Since it can be detected automatically, it is also possible to streamline processing inspection and prevent damage to the machine. It will also be understood that the final drawing pressure in the drawing process can also be optimally controlled. [Effects of the Invention] As can be understood from the description of the above embodiments, the present invention makes it possible to detect the slide pressing force in a hydraulic press machine without using a pressure measuring device. It can be easily configured, and the detected value can be displayed, used for feedback, and various other purposes, and is extremely useful as a control method for press machines that require precise control of pressing force.

[Brief explanation of drawings]

FIG. 1 is a control system diagram showing an example of a press machine using the method of the present invention. FIG. 2, FIG. 3, and FIG. 4 are explanatory diagrams of display examples of detected values. 1...Hydraulic servo cylinder device, la...
...Pulse motor, 2...Piston rod, 3...Punch, 4...Dice, 5...Command device,
7... Pulse counter, 8... Oscillator, 9...
...Speed counter, 10...Leakage length adjuster, 11
... Distance counter, 12 ... Difference counter, 13 ... Detection section. Figure 1 Figure 2 8 fins Figure 4

Claims (1)

[Claims] 1. Using a cylinder mechanism in which a predetermined amount of liquid flows in and out of the punch drive source of a press machine according to a movement amount command value, the internal pressure that occurs when a predetermined amount of liquid is accumulated in the internal cylinder of the cylinder mechanism. Fluctuations in pressure are determined in advance as a function of the position of the punch, and the amount of liquid accumulated in the cylinder is detected from the difference between the command value of the movement amount and the actual movement amount of the punch. Substituting the liquid volume into the function to find the internal pressure of the cylinder,
The pressing force of the punch is determined by multiplying this internal pressure by the piston area of the cylinder mechanism, and by making the determined pressing force a predetermined value, the pressing force of the punch is controlled to a predetermined value. A method for controlling a press machine, characterized in that: