JPH0671753B2 - Injection molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an injection molding apparatus.

(B) Conventional technology In order to manufacture a resin molded product having a predetermined shape and size by injection molding, it is necessary to design and manufacture a mold. In designing a mold, there is a part that uses empirical numerical values such as a mold deformation amount in which the mold is elastically deformed by a small amount in the mold opening / closing direction according to the pressure inside the mold during molding. Therefore, it is necessary to actually perform injection molding after manufacturing the mold and correct the mold so that the molded product has a desired shape and size.
In particular, because of the phenomenon as described above, it is important to adjust the cavity size (usually the thickness of the molded product) measured in the mold opening / closing direction. FIG. 3 shows an apparatus which has been conventionally used for such a mold correction work. The fixed side mold 52 is fixed to the fixed platen 50, and the movable platen is located at a position opposite to this.
54 is provided, to which the movable die 56 is fixed. A position sensor 58 is attached to the upper parts of both molds 52 and 56 in the figure, and a pressure sensor 62 capable of measuring the pressure in the cavity 60 is provided in the movable mold 56. Using such a device, perform the actual injection work,
The pressure in the mold and the amount of deformation of the mold during injection molding are measured synchronously, and the relationship between these and the wall thickness of the molded product measured in the mold opening / closing direction, for example, is checked to correct the mold 52/56. . As shown in FIGS. 4 (a) to 4 (d), the injection work is performed by the two molds 52.
56 is contacted, a constant mold clamping force F ₁ is applied thereto, and the molten resin is injected into the cavity 60 for a time t ₁ to t ₂ to be molded,
Further, during the time t _{2 to} t _4, a holding pressure for compensating the solidification shrinkage is applied to the molded product to cool it. The mold clamping force F ₁ is set to be larger than the product of the projected area of the molded product and the expected mold pressure P ₃ . Now, assuming that the position in the mold opening and closing direction where both molds 52 and 56 are in contact with each other without applying the mold clamping force is 0, the mold clamping force shown in Fig. 4 (a) is from 0 to a predetermined value F _1. Fixed mold as it gets bigger
52 and the movable-side die 56 are elastically deformed from the position of l ₀ to the dimension l _{1 in the} mold clamping direction, as shown in FIG. Next, as shown in FIG. (B) as the resin is filled into the cavity 60, reached a maximum value P ₃ increases mold pressure gradually from the time t ₁ to time t _3, the filling of the resin After that, the pressure inside the mold gradually decreases as the molten resin in the mold cools and solidifies, and reaches the pressure P ₄ at time t ₄ . The amount of deformation of the molds 52 and 56 also fluctuates as shown in FIG. 6C according to the fluctuation of the mold pressure. That is, the amount of mold deformation that was dimension l ₁ without resin pressure being applied to the molds 52 and 56 changes in the mold opening direction to dimension l ₃ at time t _{3 as the} resin pressure increases, and the molten resin It changes from the dimension l ₃ to the dimension l _{1 as the} mold pressure decreases due to cooling. With the completion of the holding pressure and cooling process, the amount of mold deformation rapidly returns to around l ₀ , and the mold opening process is started. Further, accordingly, the dimension h of the cavity 60 shown in FIG. 3, that is, the wall thickness dimension of the molded product changes as shown in FIG. 4 (d), and finally the dimension h ₄ close to the design value h _1. Becomes

(C) Problems to be Solved by the Invention However, if the temperature of the molded product changes even after the molded product is taken out, the dimensions of the molded product will change. It's not really easy to correct exactly. In addition to this, since the injection amount for each shot varies within a certain range, the wall thickness dimension h ₄ of the molded product also varies accordingly, and it is not possible to keep the wall thickness dimension of the molded product within the predetermined range. It was quite troublesome. It should be noted that in Japanese Patent Laid-Open No. 54-162757, the displacement detecting means arranged on the contact surface of one plate of the mold, the first storage means for storing the signal output from the displacement detecting means, and the output detecting means. From the displacement detecting means and the signal output from the displacement detecting means, first calculating means, second storing means for storing a signal to be output at the time of completion of mold clamping, and second storing means. There is shown a control factor detection means of the injection molding machine having a second calculation means for calculating the difference between the output signal and the signal output from the first storage means.
However, in such a configuration, there is a problem that a plurality of storage means and a plurality of calculation means are required, respectively, and the dimension adjustment work of the mold becomes complicated accordingly.

The present invention aims to solve such problems.

(D) Means for Solving the Problems The present invention solves the above problems by simplifying the storage means and the arithmetic means. That is, the injection molding apparatus of the present invention includes a mold (4, 8), a mold clamping cylinder (10) for opening and closing the mold, a fixed mold (4) and a movable mold (8) during mold closing. A position sensor (12) for measuring the relative position to
Which is provided with a servo valve (14) capable of adjusting the pressure of hydraulic oil supplied to the hydraulic circuit of the mold clamping cylinder (10), and the mold (4.8) Position sensor (1
The memory device (24) that stores the mold clamping completion relative position signal detected by 2) is compared with the mold clamping completion relative position signal and the mold relative position signal from the position sensor (12) during molding. And a controller (26) for outputting a command signal to the servo valve (14) so as to match with each other.

An initial mold clamping force setting device (28) that can set a predetermined initial mold clamping force and outputs an initial mold clamping force signal to the controller (26) may be provided. The reference numerals in parentheses indicate the corresponding members in the embodiments described later.

(E) Action The movable mold is moved from the mold open position to the mold closed position by the mold clamping cylinder. Then, the fluid pressure set in advance in the servo valve in response to a command from the controller is applied to the mold clamping cylinder. As a result, the mold is clamped with a predetermined initial mold clamping force corresponding to the fluid pressure, and the mold is elastically deformed by a minute dimension in the mold closing direction. The relative position of completion of mold clamping is detected by the position sensor and stored. Next, when the molten resin is injected into the cavity and the mold internal pressure increases, the mold elastically deforms in the mold opening direction by an amount corresponding to this. The relative position of the mold is detected by the position sensor, and the controller outputs a command signal to the servo valve so that the deformation amount of the mold from the mold clamping completion relative position of the mold is always 0. Adjusts the hydraulic pressure supplied to the mold clamping cylinder. As a result, the magnitude of the mold clamping force that acts on the mold from the mold clamping cylinder changes, and the mold clamping cylinder forces the mold to always be positioned at the mold clamping completion relative position. By doing so, even if the injection amount varies from shot to shot, the mold is always held at the relative position for completion of mold clamping during the molding process, and the wall thickness of the molded product taken out after mold opening is kept constant. Can be one. In this case, even if the injection quantity varies within a certain range, the density of the molded product will also vary within the range, and the external dimension of the molded product, especially the wall thickness measured in the mold opening / closing direction, will be constant. Can be

(F) Embodiment An embodiment of the present invention is shown in FIG. The fixed side mold 4 is fixed to the fixed platen 2. The fixed platen 2 is fixed to a bed of an injection molding machine (not shown). A movable plate 6 is arranged at a left position in the figure facing the fixed plate 2, and a movable mold 8 is fixed to the movable plate 6. The movable platen 6 is connected to a piston rod of the mold clamping cylinder 10 and is driven by the movable platen 6 to move on a bed of an injection molding machine (not shown). As a result, it is possible to move the movable side mold 8 between the illustrated mold closed position in which the movable side mold 4 is in contact with the fixed side mold 4 and the mold open position on the left side in the figure separated from the fixed side mold 4. . A cavity A is formed by the fixed mold 4 and the movable mold 8. The thickness dimension h ₁ of the cavity A measured in the mold opening / closing direction when the initial mold clamping force, which will be described later, is applied is the designed thickness dimension when the temperature change of the molded product is not taken into consideration. Molten resin can be injected into the cavity A from an injection device (not shown) through the resin passage of the stationary platen 2. A position sensor 12 is attached to the upper ends of the fixed mold 4 and the movable mold 8 in the figure. The position sensor 12 can output a signal of the relative position of the fixed-side mold 4 and the movable-side mold 8 in the mold opening / closing direction to a mold deformation amount amplifier 22, which will be described later. Each fluid port of the mold clamping cylinder 10 passes through each fluid port of the servo valve 14, and then the discharge port of the hydraulic pump 18 and the tank 19
It is connected to the. The servo valve 14 is controlled by a controller 26, which will be described later, via a servo amplifier 16, and the discharge side of the hydraulic pump 18 is connected to one of the mold clamping side pipeline 10a and the mold opening side pipeline 10b of the mold clamping cylinder 10. While switching the pipeline,
The discharge pressure from the hydraulic pump 18 is adjusted to a desired value and supplied to the mold clamping cylinder 10. The maximum discharge pressure of the hydraulic pump 18 is set by the relief valve 20.
The initial mold clamping force setting device 28 can set the initial mold clamping force to this, and can output this set value to the controller 26. This makes it possible to determine the discharge pressure of the servo valve 14 supplied to the mold clamping cylinder 10 for initial mold clamping. That is, the movable mold 8 is pressed with a predetermined mold clamping force.
It is possible to apply an initial mold clamping force that clamps the fixed mold 4 to the mold clamping cylinder 10. Mold deformation amount amplifier
22 has an amplification function of amplifying the analog signal from the position sensor 12 and an analog / digital conversion function of converting the amplified analog signal into a digital signal. Of the relative position signals input to the mold deformation amount amplifier 22, the fixed side mold 4 and the movable side mold 8 when the mold is clamped with the initial mold clamping force.
The signal of the relative position of completion of mold clamping is input to the storage device 24 and is stored therein. The signals of the other relative positions are input to the controller 26 through the mold deformation amount amplifier 22. It is like this. A signal of the mold clamping completion relative position from the memory 24 is also input to the controller 26. That is, the controller 26 passes through the signal from the memory device 24, the signal from the initial mold clamping force setting device 28, and the mold deformation amount amplifier 22 to move the movable side mold 8 and the fixed side mold 4 from moment to moment. The relative position signal of is input. The controller 26 can control the servo valve 14 via the servo amplifier 16 using each of the above signals to adjust the pressure acting on the mold clamping cylinder 10, whereby the fixed mold 4 and the movable mold 4 can be moved. It is possible to adjust the mold clamping force acting on the side mold 8.

Next, the operation of this embodiment will be described with reference to FIGS. Servo valve 1 is now installed in the mold clamping side conduit 10a of mold clamping cylinder 10.
Hydraulic oil is supplied from the hydraulic pump 18 via 4,
It is assumed that the movable platen 6 has moved to the mold closing position shown in FIG.
The mold clamping cylinder 10 is instructed by a command from the controller 26 based on the set value signal set in the initial mold clamping force setting device 28 in advance.
The initial setting mold clamping force F ₁ is applied to the mold clamping side pipe line 10a (Fig.
The hydraulic fluid is set to a pressure corresponding to (see). As a result, the fixed-side mold 4 and the movable-side mold 8 are elastically deformed, and as shown in FIG. 2C, the mold closing completion relative position displaced from the mold closing position l _{0 in the} mold closing direction by a minute distance l _1. Located in. The relative position of completion of mold clamping is detected by the position sensor 12, passes through the mold deformation amount amplifier 22, and is stored in the memory 24 as a relative position signal of completion of mold clamping. Further, this mold clamping completion relative position signal is input from the memory 24 to the controller 26. Next, molten resin is injected into the cavity A from an injection device (not shown), but the wall thickness of the molded product measured in the mold opening / closing direction is the dimension h _{1 as} shown in FIG. There is. As the resin filling progresses, the pressure inside the mold gradually increases as shown in the figure (b), and the predetermined maximum value P ₃
Reach up to. In response to this, the fixed side mold 4 and the movable side mold 8 also try to elastically deform in the mold opening direction, but this minute deformation amount is detected by the position sensor 12, and as shown in FIG. The pressure of the hydraulic oil supplied to the mold clamping cylinder 10 is adjusted by the servo valve 14 so that the amount of mold deformation is always a minute distance l ₁ . That is, the same figure (d)
As shown in, the thickness of the molded product is maintained at the dimension h ₁ .
This state is also maintained in the pressure holding / cooling process following the injection process. That is, as shown in (c) of the figure, as the mold internal pressure gradually decreases from the maximum value P ₃ to the pressure P ₄ from time t ₃ to time t ₄ , the mold shown in FIG. The clamping force is reduced from force F ₃ to F ₄ . As a result, the amount of mold deformation continues to be maintained at the position of the minute distance l ₁ , and the thickness of the molded product is also maintained at the dimension h ₁ . After cooling, movable mold 8
Is opened and the molded product is taken out. As a result, the molded product can be dimensioned as designed. In this case, even if the injection quantity varies within a certain range, the mold clamping force is adjusted so that the wall thickness dimension of the molded product will be constant, so the density of the molded product will vary within the corresponding range. As a result, the wall thickness dimension of the molded product measured in the mold opening / closing direction can be made constant.

(G) Effect of the Invention As described above, according to the present invention, the mold clamping force is adjusted so that the mold is always located at the mold clamping completion relative position during molding. Although the apparatus has such a structure, it is possible to simplify the work of adjusting the size of the mold and make the size of the manufactured molded product constant.

[Brief description of drawings]

FIG. 1 is a block diagram of an injection molding apparatus according to an embodiment of the present invention, and FIG.
(A) to (D) are diagrams for explaining the molten resin injection-cooling state according to the present invention, FIG. 3 is a diagram showing an example of an apparatus used for conventional mold adjustment work, and FIG. 4 ( (A) to (D) are diagrams for explaining a molten resin injection-cooling state by a conventional injection molding apparatus. 2 ... Fixed board, 4 ... Fixed side mold, 6 ... Movable board, 8 ...
… Movable mold, 10 …… Clamping cylinder, 12 …… Position sensor, 14 …… Servo valve, 24 …… Memory device, 26 …… Controller, 28
…… Initial mold clamping force setting device.

Claims (2)

[Claims] 1. A mold (4, 8), a mold clamping cylinder (10) for opening and closing the mold, and a relative position of the fixed mold (4) and the movable mold (8) during mold closing. A position sensor (12) to measure
In the injection molding apparatus having the, a servo valve (14) capable of adjusting the pressure of hydraulic oil supplied to the hydraulic circuit of the mold clamping cylinder (10) is provided, and the mold (4, 8) is A memory (24) for storing the mold clamping completion relative position signal detected by the position sensor (12) when the mold is clamped with a predetermined initial mold clamping force, and the mold clamping completion relative position signal and the position sensor during molding. A controller (26) for comparing the relative position signal of the mold from (12) and outputting a command signal to the servo valve (14) so that both signals coincide with each other. Injection molding equipment. 2. The injection according to claim 1, further comprising an initial mold clamping force setting device (28) capable of setting a predetermined initial mold clamping force and outputting an initial mold clamping force signal to the controller (26). Molding equipment.