JP3188908B2 - Injection compression molding method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method in which a closed mold is filled with a molten resin, the mold is slightly opened by the pressure of the filled resin, and then compression is performed on the mold clamping side. And devices.

[0002]

2. Description of the Related Art In injection compression molding in an injection molding machine, (1) mechanically controlling the retreat limit of the movement of the mold when the mold is opened by injection-filled tree finger pressure. (2) Detecting the mold opening amount of the mold (the mold opening amount refers to the position of the mold held at the mold opening position in consideration of the moving amount of the mold moving backward or the compression amount due to the charged resin pressure). Then, the mold clamping pressure or the injection speed is controlled so as to achieve the set mold opening amount and mold opening speed. (3) In the compression step, the mold opening amount of the mold is detected, and the precision is changed by changing the mold clamping speed or the mold clamping pressure so as to achieve the set mold compression movement amount and mold compression movement speed. We perform molding and molding of complicated or thin-walled shapes.

[0003]

The conventional injection compression molding has the following problems. First, (1) In the method of mechanically limiting the retraction limit of a mold, it is difficult to cope with a change in molding conditions such as a resin temperature during molding, so that the quality of molded products varies. Since a time lag occurs during the transition to the compression process after filling is completed, the resin flow rate in the mold becomes discontinuous,
As a result, defects such as flow marks occur. Also, to prevent defects such as flow marks,
An interlocking operation for balancing the injection mechanism side and the mold clamping mechanism side is required, which complicates the software and hardware aspects of the control and reduces operability.

(2) According to the method of detecting the mold opening amount of the mold and controlling based on the detection signal, the defect such as the flow mark caused by the discontinuity of the flow velocity of the resin filled in the cavity of the mold can be eliminated. Although it can be solved quite a bit, on the contrary, both the software and hardware aspects are considerably complicated and the operability becomes extremely difficult.

On the contrary, since the mold opening or compression process can be controlled according to the set value, it is extremely difficult to select the optimum set value, and the flexibility for absorbing the fluctuation of the molding conditions during molding is reduced. Therefore, there is a possibility that the non-defective rate may be significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a simple control of only the injection pressure and the mold clamping pressure is not affected by fluctuations in molding conditions during molding, and a good product is stably obtained. It is intended to supply.

[0007]

In order to achieve the above object, according to a first aspect of the present invention, the amount of shrinkage due to cooling and solidification of resin is previously calculated on the injection mechanism side during the injection filling step, and the amount of shrinkage is calculated. The injection pressure is controlled by the injection pressure at which the amount of the resin added can be charged into the mold, and the mold clamping mechanism side corresponds to the amount of the resin that has been cooled, solidified and shrunk by the pressure of the resin charged into the mold cavity. A mold clamping force that allows the mold to open up to the mold opening amount is added to the mold in advance, and the mold clamping force is maintained until the resin is cooled and solidified even after the injection filling is completed. Injection pressure control to a constant filling pressure from the start of injection filling to the completion of injection filling
Filling without controlling the pressure control and leaving the amount of shrinkage.
According to the invention, the holding of the mold clamping force is continued until a time-out signal of a timer activated when the injection driving force of the injection mechanism indicating the completion of the injection filling starts to rapidly increase is reached.

Further, in the fourth invention, the holding of the mold clamping force is continued until a time-out signal of a timer which starts when the movement of the injection drive unit of the injection mechanism indicating the completion of the injection filling is stopped is reached. In the invention, the holding of the mold clamping force is continued until a time-out signal of a timer activated when the mold is returned to the mold closing position before the resin is injected and filled is reached.

According to a sixth aspect of the present invention, there is provided an injection control section for providing an injection filling amount setting means and an injection pressure setting means for performing injection filling based on the two setting means, and a cooling solidification shrinkage amount of the resin by the injection filling. A mold clamping force setting unit that sets a mold clamping force that allows the mold to be opened to a mold opening amount corresponding to a mold clamping amount, and a mold clamping control unit that performs mold clamping based on the mold clamping force setting unit. When the injection driving force of the injection mechanism suddenly starts increasing, or when the movement of the injection driving unit stops, an injection filling completion detection unit that generates an injection filling completion signal, and a detection signal from the injection filling completion detection unit. A timer that starts based on the time, a time setting unit that sets the pressure-holding / cooling time in the compression process, and compares the set value of the time setting unit with a timeout signal of the timer to the injection control unit and the mold clamping control unit. each It was configured to have a comparison control unit for generating a control signal.

[0010]

In the injection filling process, the filling is controlled so that the filling can be performed at a high speed in the initial stage of filling because the flow resistance of the resin in the mold cavity is small, and in the latter stage of the filling, the flow resistance of the resin increases so that the filling speed is increased. Is naturally decelerated, so that the resin has a continuous speed gradient automatically during resin filling, and can be an ideal natural filling flow (natural flow) that does not generate pack pressure.

[0011] Further, by filling the amount of resin to which the amount of cooling and solidifying shrinkage of the resin is added, and by setting the mold clamping force to allow a mold opening amount corresponding to the amount of cooling and solidifying shrinkage, the mold is filled when the injection filling is completed. Since the resin is almost fully filled (just pack), it is completely unaffected by the occurrence of defects such as flow marks due to the discontinuity of the resin flow velocity in the mold. Appropriate mold clamping force is applied to the mold during the injection filling and switching of the compression process, so that even if the molding conditions fluctuate during molding, the mold clamping force is an elastic action like a spring. Has the flexibility to work as

In the compression step, by holding the mold with the initial mold clamping force, unnecessary mold clamping force is not applied to the resin.
Since the compression action corresponds to the cooling, solidification, and shrinkage behavior of the resin, residual strain and deformation can be extremely reduced.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a control conceptual diagram of an embodiment according to the present invention,
2 is a plan view of the mold clamping device, FIG. 3 is a cross-sectional view of the screw engagement adjusting device, FIG. 4 is an explanatory diagram showing an operation state of the half nut, FIG.
FIG. 6 is a relationship diagram showing the relationship between the mold opening amount of the mold and the mold clamping pressure, and FIG.
FIG. 7 is an explanatory view showing a state of injection compression molding including an injection filling step and a compression step from the start of injection filling to the completion of injection filling of the injection device, and FIG. 7 is a control conceptual diagram showing another embodiment similar to the present invention. Shown respectively.

The injection compression molding apparatus in this embodiment comprises a mold clamping device 1, an injection device 40, and a control unit 60. First, the mold clamping device will be described with reference to FIGS. A mold clamping device 1 shown in FIG. 2 includes a moving cylinder 2, a mold clamping cylinder 3, a tie bar 7, a fixed platen 10, a screw engagement adjusting device 1.
1, movable board 20, nut box 21, half nut 2
2, tie bar locking device 26, fixed mold 30a, movable mold 3
0b and the connecting plate 50.

The fixed mold 30a is mounted on a fixed platen 10 fixed on one end of the machine base 1a, while the fixed platen 10a is mounted on the other end of the machine base 1a.
The movable mold 30b is attached to the movable platen 20 so as to be opposed to the movable mold 30b. The opposing surfaces of the fixed mold 30a and the movable mold 30b are configured to engage with unevenness, and define a cavity 28 between the fixed mold 30a and the movable mold 30b. Fixed board 1
The distal ends of the piston rods 6 of the movable cylinder 2 fixed to both side surfaces of the movable cylinder 0 are attached to the movable platen 20, and can slide on and off the machine base 1a with respect to the fixed platen 10. Reference numeral 4 denotes an internal piston, 4a denotes a piston rod chamber side, and 4b denotes a piston head chamber side.

The tie bars 7 penetrating the movable platen 20 are plural (four in the present invention) manufactured to have the same diameter over the entire length.
One end thereof is fixed to the internal piston 5 of the mold clamping cylinder 3, and the other end is penetrated in a direction substantially perpendicular to the connecting plate 50, and is then fixed by tightening with a nut or an end plate 51. The tie bar 7 and the connecting plate 50 are prevented from turning around by using a key or the like.

An internal piston 5 is provided in the mold clamping cylinder 3 so as to be slidable back and forth, and a packing for preventing oil leakage is provided on the outer periphery of the internal piston 5. A tie bar 7 is provided on the rod side of the internal piston 5. The ram 53 is fixed on the approximate center of the internal piston 5 and is provided on the head side in a convex shape. Further, the ram cylinder 52 engaged with the ram 53 is
Are provided so as to be slidable back and forth, and packing is provided on a sliding portion on the outer periphery of the ram 53 so that oil from the ram chamber 5c does not flow to the piston head chamber side 5b. Reference numeral 5a indicates the piston rod chamber side.

The outer diameter of the ram 53 is, for example, １ ／ or less of the outer diameter of the tie bar 7 or １ ／ of the outer diameter of the inner piston 5.
The length of the ram 53 is set to be equal to or less than １ ／, and the length of the ram 53 is such that the front end of the ram 53 abuts on the inner part of the ram cylinder 52 before both sides of the head end of the internal piston 5 abut on the end face of the ram cylinder 52 during mold clamping. It has such a configuration.

At a substantially middle position of the tie bar 7, when the movable mold 30b and the fixed mold 30a come into contact with each other during the mold closing operation, the movable plate 20 is engaged with the half nut 22 to be described later to lock the movable plate 20 to the tie bar 7. Screw portion or groove portion 8 is formed. One end is fixed to the movable platen 20, and the other end is screwed with the screw portion 12 of the adjusting shaft 13 of the screw engagement adjusting device 11, which will be described later. Here, the screw engagement adjusting device 11 includes a screw portion 12, an adjustment shaft 13, and a pressing member 1.
7, slide key 18, sprocket 19 and holding plate 2
5 and the like.

Next, the tie bar locking device 26 will be described with reference to FIG. The tie bar locking device 26 includes a half nut opening / closing cylinder 14, a piston 15, a piston rod 16, a half nut 22, a connecting rod 101, and stoppers 102 and 103.

The half nut 22 is provided adjacent to the movable platen 20, and has a set of half nuts 22 divided vertically into two for each tie bar 7. The half nut 22a is on the anti-meshing side of the half nut 22a. One end of the piston rod 16 is fixed to the end face. At the other end of the piston rod 16, a piston 15 which engages with the half nut opening / closing cylinder 14 and slides up and down is provided.
0 is fixed. A connecting rod 101 connected through the half nuts 22a and 22b is disposed on the left and right sides of the piston rod 16, one end of the connecting rod 101 is fixed to the adjusting plate 100, and the other end is connected to the half nut 22b. It is fixed.

As shown in FIG. 4A, a piston rod side chamber 15b of the half nut opening / closing cylinder 14 is provided.
, The piston 15 is pushed up and the half nut opening / closing cylinder 14 is pushed down, so that a pair of upper and lower half nuts 22 a and 22 b move while sliding on the nut box 21. The engagement between the half nut 22 and the tie bar 7 is released, and the stopper 10
It stops when it comes into contact with 2,103.

When the half nut 22 is to be engaged with the tie bar 7, pressure oil is supplied to the piston head chamber side 15a of the half nut opening / closing cylinder 14, as shown in FIG. The half nut opening / closing cylinder 14 is pushed upward while the piston 15 is pushed down, and the half nuts 22 a and 22 b move while sliding on the nut box 21 and finally come into contact with each other, and mesh with the tie bar 7. The configuration is such that the state is performed.

Further, the right and left 1
In the 80-degree direction, one end of the half nut 22 is turned around a sprocket portion 19 fixed to the end of the adjustment shaft 13 that is provided with the tie bar 7 inserted therethrough.
The end of the adjustment shaft 13 on the side is always in contact with the half nut 22 and slides.

At the other end of the half nut 22, several insertion chambers for the pressing member 17 are provided at a part of the movable platen 20 on the side opposite to the fixed platen 10 for each set of two half nuts 22. The half nut 22 is constantly pressed in the axial direction of the tie bar 7. When the adjusting shaft 13 moves toward the fixed platen 10, the spring of the pressing member 17 is compressed, and the anti-fixed plate 1
When moving to the 0 side, it is arranged to be extended.

A sprocket portion 19 is provided on the outer periphery of the adjustment shaft 13 near the end on the side opposite the half nut 22, and the rotation of the adjustment shaft 13 is prevented by using a slide key 18. The sprocket portion 19 is connected with a chain (not shown), and the chain is connected with a sprocket integral with the output shaft of a motor (not shown). The rotation of the motor drives the chain to move the adjustment shaft 13 back and forth in the axial direction of the tie bar 7. Thus, the position of the half nut 22 can be adjusted so that the half nut 22 that is in contact with the adjustment shaft 13 is engaged with the thread portion or the groove portion 8 on the tie bar 7.

As for the outer periphery of the shaft of the sprocket 19, one end is fixed to the nut box 21 and the other end is fixed to the nut box 21 to prevent the sprocket 19 from dropping off. The holding plate 25 is rotatably supported by the holding plate 25. Reference numeral 24 indicates an insertion hole.

In this embodiment, the above-described mold clamping device is used for the following reason. The mold clamping mechanism is compact and space can be saved. Since the amount of pressurized oil supplied to the small-capacity ram chamber 5c may be a small amount of oil, the mold opening and compression responsiveness during injection compression molding are high. The tilt correction (leveling control) of the movable platen 20 can be performed by adjusting the hydraulic pressure supplied to the plurality (four) of the mold clamping cylinders 3.

Next, the injection device 40 will be described. In the injection device 40 in this embodiment, a screw 42 is provided in a barrel 41, and a resin material in a hopper 43 is heated and compressed in a supply zone and a compression zone, melted and weighed in a measurement zone, and passed through an injection zone to a nozzle 44.
It is configured to be injected into the interior.

A heater for externally heating the resin material is provided on the outer peripheral surface of the barrel 41, and the resin material is sent forward by the rotation of the screw 42.

Reference numeral 46 denotes an injection cylinder, and 47 denotes a forward / reverse rotation motor which is directly connected to the screw 42 so as to rotate the screw 42 forward / reverse.

Next, the control section 60 will be described. The control unit 60 includes an injection filling amount setting unit 61 and an injection pressure setting unit 6
2. Injection control unit 63, hydraulic control valve 64, mold clamping force setting means 65, mold clamping control unit 66, hydraulic control valve 67, hydraulic supply source 6.
8a, 68b, injection filling completion detecting section 69, timer 70,
It comprises a time setting unit 71 and a comparison control unit 72.

The injection filling amount setting means 61 and the injection pressure setting means 62 are connected to an injection control section 63, and the injection control section 63 controls the operation of a hydraulic control valve 64 for controlling the operation of the injection cylinder 46 and the operation of the forward / reverse rotation motor 47. It is connected to a control device (not shown) for controlling and a mold clamping force setting means 65.

The mold clamping force setting means 65 is also connected to a mold clamping control section 66, and the mold clamping control section 66 is connected to a hydraulic control valve 67 for controlling the operation of the mold clamping cylinder 3. Note that 68
a and 68b are simplified hydraulic supply sources.

A pressure sensor or a speed sensor (both not shown) attached to the injection cylinder 46 is connected to an injection filling completion detecting section 69, and the injection filling completion detecting section 69 is connected to a timer 70. The time setting unit 71 and the timer 70 are connected via a comparison control unit 72, and the comparison control unit 72 is connected to the mold clamping control unit 66 and the injection control unit 63, respectively.

The operation of the injection compression molding apparatus configured as described above will be described.

First, the control unit 60 injects a resin amount as a measured value by adding a cooling solidification shrinkage amount of the resin calculated according to the resin physical properties to the volume of the cavity 28 defined by the fixed mold 30a and the movable mold 30b. The injection pressure setting means 62 sets the injection pressure condition having the best injection efficiency from the injection filling pressure range which can be filled into the cavity 28 and does not generate burrs, while being set by the filling amount setting means 61.

At the same time, the movable mold 30b is moved to the fixed mold 30a from the set measurement value and injection pressure value, the cavity 28 volume and the cavity projected area to the mold opening amount corresponding to the amount of cooling, solidification and shrinkage of the resin when the injection filling is completed. The mold clamping force setting means 65 sets a mold clamping force value that allows separation.

In this case, a state in which the molten resin is almost fully filled at the time of completion of the injection filling (just pack) is defined as an appropriate mold clamping force value. This state will be described in detail with reference to FIG.

FIG. 5 shows the amount of separation of the movable mold 30b from the fixed mold 30a when the mold clamping pressure value is changed when the injection filling is performed under the condition that the measured value and the injection pressure value are constant, that is, the mold opening. The relationship with the amount is shown.

FIG. 5 is a graph of the data obtained from the experiment or from the experiment, and the following findings were obtained from this data. That is, in the case of, a box having a size of 250 L × 300 W × 50 H × 2 t (projected area: 750 cm ² ) is obtained as a molded product, and the surface of the cavity 28 is relatively flat, and there is a vertical rib on the side of the box. For example, a case where a personal computer case or a document case is formed is shown.

In the case (3), the cavity 28 has a flat surface, not a rib structure, but a very flat molded product such as a lens or a disk.

In the case (3), the cavity 28 has a complicated shape, and a molded product such as an instrument panel or a bumper having a complicated shape, a large shape, or a thick shape as a whole is formed.

As described above, in FIG.
As the mold clamping pressure is increased from low pressure to high pressure, the mold opening decreases, and tends to move to the left and right with respect to the standard. The inflection points that decrease (A, A ′,
A ″) was found to appear.

As a representative example of such experimental results, in the region B where the mold clamping pressure value is smaller than the inflection point A,
Since the movable mold 30b is separated from the fixed mold 30a by the kinetic energy of the resin flow during the injection filling, a large gap is generated between the filled resin and the cavity 28 when the injection filling is completed.

In such a state, the flow speed of the resin becomes discontinuous when shifting from the completion of the injection filling to the compression step,
As a result, defects such as flow marks occur. In order to eliminate the cause of such defective products, a molding method that is extremely difficult to control, such as linking the injection step and the compression step, is required.

Conversely, in a region C where the mold clamping pressure value is larger than the inflection point A, the kinetic energy of the resin flow during injection filling is reduced without the movable mold 30b relatively moving with respect to the fixed mold 30a. Since the resin can be absorbed, the resin has been fully filled (just pack) into the cavity 28 at the time of completion of the injection filling.

Further, in the above-mentioned region C, there is no occurrence of a defect such as a flow mark because the resin does not re-flow even when shifting to the compression step, so that the injection step and the compression step are controlled in conjunction with each other. Becomes unnecessary.

Based on the above results, in the present embodiment, the region C was selected. That is, even in the region C, in the region where the mold clamping pressure value is large, the resin pressure in the cavity 28 becomes high as a result, and the resin pressure in the cavity 28 is reduced, which is one of the advantages in the injection compression molding. The maximum value (upper limit value) of the mold clamping pressure is defined from the allowable maximum value of the resin pressure in the cavity 28, which is determined to be appropriate from the shape of the molded product and the physical properties of the resin, and the lower limit value is the inflection point. Of the mold clamping pressure value corresponding to point A, ie, D
The region was set to an appropriate mold clamping pressure value.

When setting the appropriate mold clamping pressure value as described above, the mold opening amount is defined as shown in FIG. 5, but the quality inspection of the molded product after molding determines the presence or absence of defects such as flow marks. Then, the inflection point A can be obtained.

When the initial setting is completed as described above,
Next, the molding operation starts.

At the time of closing the mold, by supplying pressure oil to the piston rod chamber side 4a of the movable cylinder 2, the movable platen 20 and the nut box 21 fixed to the side surface of the movable platen 20 are supplied.
And the screw engagement adjusting device 11 and the like
Move together in the axial direction of. First, the screw portion or the groove portion 8 engraved substantially at the middle position of the tie bar 7 is smoothly inserted into the insertion hole 24 of the movable platen 20, and the movable platen 20 is further advanced. And fixed mold 30a
Of the moving cylinder 2 is stopped, whereby the supply of pressure oil to the piston rod chamber side 4a of the moving cylinder 2 is stopped.

Next, the half nut 22 starts to mesh with the thread or groove 8 on the tie bar 7. First, when pressure oil is supplied to the piston head chamber side 15a in the half nut opening / closing cylinder 14 through a pipe (not shown), the half nut 22
Moves forward in a direction substantially perpendicular to the tie bar 7. Here, in advance, when the movable mold 30b and the fixed mold 30a are in contact with each other, the mold thickness (die height) H of both molds is measured on a scale, and this is measured as the pitch of the screw portion or the groove portion 8 on the tie bar 7. When divided by P (H / P), here, if there is no fraction and no fraction below the decimal point, the two molds are in light contact with each other and the half nut opening / closing cylinder 14 is moved to the piston head chamber side 15a. When the pressurized oil is supplied, the half nut 22 completely meshes with the thread portion or the groove portion 8 on the tie bar 7.

However, contrary to the above, when H / P is not divisible and a fraction below the decimal point is generated, the pitch (or half) of the thread or groove 8 on the tie bar 7 is added to the fraction below the decimal point. The value obtained by multiplying the pitch P) of the screw of the split nut 22 is equal to the half nut 22 and the screw portion or groove portion 8 on the tie bar 7.
Is the moving distance A for fully meshing the.

That is, after the two dies are brought into light contact with each other, the motor connected by the chain is rotated by an amount corresponding to the moving distance A, thereby rotating the sprocket 19 and moving the adjustment shaft 13 forward and backward. However, the rotation of the motor is measured by a pulse, and can be converted into a moving distance before and after the adjustment shaft 13. Thus, the half nut 22 can be completely engaged with the threaded portion or the grooved portion 8 on the tie bar 7.

When the engagement is completed, the mold clamping of the movable mold 30b and the fixed mold 30a by the mold clamping cylinder 3 can be started. Thereafter, the hydraulic control valve 67 is driven based on the output signal of the mold clamping control unit 66 to supply the pressurized oil to the piston rod chamber side 5a of the mold clamping cylinder 3 fixed to the fixed platen 10 to thereby fix the fixed mold. 30a and movable mold 3
Strong clamping between 0b can be started. Here, the mold clamping force applied between the fixed mold 30a and the movable mold 30b is an appropriate mold clamping pressure value set previously. Whether or not the mold clamping has been completed can be confirmed by comparing a detection value of a pressure sensor disposed on the piston rod chamber side 5a with a set value.

Next, after the mold clamping is completed, the injection filling operation is started.

The hydraulic control valve 64 is actuated based on the output signal of the injection control unit 63 to operate the piston 4 of the injection cylinder 46.
8 is advanced, and the advance at this time is pressure-controlled based on the injection pressure value set previously.

That is, in the early stage of injection, high-speed filling is performed because the flow resistance in the cavity 28 is small, and in the late stage of injection, the filling speed naturally decreases with an increase in the flow resistance in the cavity 28. As a result, the continuous speed is increased. An ideal natural filling flow (natural flow) having a gradient and generating no pack pressure is obtained.

The weighing operation for the next shot has already been completed by the injection device 40 being performed in parallel with the compression process, and the forward / reverse rotation motor 47 is output based on the output signal of the injection control unit 63. While the molten resin is measured by the previously set measurement value.

Further, during the injection filling step, the injection cylinder 4
By the pressure control of No. 6, the shot-cut state in which the so-called cushion amount is not left until the screw 42 reaches the forward limit, that is, the injection control is performed without leaving the contraction amount.

In this manner, detection for confirming the completion of injection filling described later is extremely easy and accurate, and weighing and injection filling control are also simplified.

Even in the cut-off state, the molten resin is filled with the set injection pressure value in the nozzle 44 and the passage to the cavity 28, so that it does not flow backward.

It is also possible to perform injection filling while leaving the cushion amount, but in this case, it is necessary to prevent the movable mold 30b from moving after the filling pressure set value on the injection side is completed.

The movable mold 30b retreats (opens) in a direction away from the fixed mold 30a in response to the injection filling. When the injection filling is completed, the mold opening becomes the maximum, and the molten resin is almost completely filled in the cavity 28 (just pack).
The state of the mold and the fact that the mold clamping pressure value acts elastically like a spring, which always applies an elastic force. Therefore, even when switching from the injection process to the compression process, defects such as flow marks are observed. Since there is no need to worry about the occurrence, no special switching timing control is required.

Furthermore, even if molding conditions such as resin temperature fluctuate during molding due to the elastic action of the mold clamping, there is no variation in quality because it acts to absorb the fluctuation.

Next, after the injection filling is completed, a compression step is performed on the mold clamping mechanism side.

Whether the injection filling is completed or not is determined by the change of the working oil pressure value in the injection cylinder 46 or the change of the forward movement of the piston 48 in the above-mentioned cut-off state. These states will be described with reference to FIG.

In FIG. 6, the screw 4 is maintained so that the injection filling pressure is constant from the start of the injection filling to immediately before the completion of the injection.
The operating oil pressure value in the injection cylinder 46 is controlled to be constant in conjunction with the forward operation 2.

When the injection is completed, that is, when the screw 42 reaches the forward limit, the forward operation of the screw 42 is stopped, so that the working oil pressure value in the injection cylinder 46 temporarily increases rapidly. That is, by detecting the operating oil pressure value in the injection cylinder 46, the completion of the injection filling can be accurately detected. However, the present invention is not limited to this, and when the forward movement of the screw 42 or the forward movement of the piston 48 is stopped, it may be detected that the injection and filling are completed. Furthermore, it is also possible to use a method for confirming and detecting the completion of injection filling as described above in combination.

When the injection filling completion detecting section 69 detects the completion of the injection filling, the timer 70 is started to control the compression process.

Here, the holding pressure cooling time or the weighing start time is input in advance to the time setting section 71. When the holding pressure cooling time is input, the time depends on the resin temperature, the mold cooling capacity and the shape of the molded product. After calculating the cooling and solidification time of the resin, it is set as the holding pressure cooling time (compression completion time).

When inputting the weighing start time, the time when the gate is sealed is set as a reference, but in a molding machine having a shut-off valve incorporated, the time is set based on the shut-off valve closing operation completion time. You do it.

The time-out signal of the timer 70 is compared with the set value of the time setting unit 71 by the comparison control unit 72, and when it is found that each set value has been reached, the injection control unit 63 receives the measurement start signal and the mold start signal. After the compression completion signal is output to the tightening control unit 66 and the product is taken out following the mold opening, the next molding operation is started.

As described above, in the compression step, the compression operation corresponding to the cooling, solidification and shrinkage behavior of the resin can be realized by maintaining the appropriate mold clamping pressure value, and a high-quality molded product with extremely low distortion can be obtained. You can do it.

That is, the maximum value of the mold clamping force at the time of performing compression on the mold clamping side is the initial setting mold clamping force that defines the amount of mold opening during the injection filling process, and the mold clamping force during the compression process is the initial value. Test results have shown that the same level as the mold clamping force is sufficient.

Therefore, by maintaining the initial mold clamping force even in the compression step, the most appropriate compression action can be obtained for the resin, and also in the control, the timing control of the pressure increase of the mold clamping force and the optimum mold clamping force can be achieved. No complicated control such as setting is required.

Further, the cost of the molding machine can be reduced by eliminating the need for a pressure increasing line of the mold clamping force, and the advantages of the mold and the molding machine due to the unnecessary addition of the mold clamping force can be prevented.

Next, another control method similar to the embodiment according to the present invention will be described with reference to FIG. The description of the same elements described in FIG. 1 will be omitted, and different parts will be mainly described.

The holding of the mold clamping force during the compression step can be performed by detecting the front-back fluctuation state of the movable mold 30b.

That is, in this embodiment, a mold position detecting section 74 for detecting the current position of the movable mold 30b by receiving a detection signal from a displacement detector (not shown) such as an encoder attached to the movable platen 20; A reference point setting section 75 for setting the position of the movable mold 30b before the injection filling step clamped by the initial mold clamping force as a reference point, and an output signal from the mold position detection section 74 and setting of the reference point setting section 75. The control unit includes a comparison control unit 72 that compares the value with a value and outputs a timer 70 start signal. A similar result can be obtained even if a displacement detector is directly attached to the movable mold 30b or the mold clamping cylinder 3.

Next, the operation of the injection compression molding apparatus based on FIG. 7 will be described.

First, the position of the movable mold 30b in the clamped state before injection filling is detected by the mold position detecting section 74, and this detected value is set in the reference point setting section 75 as a reference point.

Since the operation up to the completion of the injection filling is the same as the control procedure described with reference to FIG. 1 as described above, the subsequent compression step will be described.

In the compression step, the comparison control unit 72 compares the output signal of the mold position detection unit 74 with the set value of the reference point setting unit 75.
Then, after confirming that the movable mold 30b has returned to the same state as before the injection filling, the timer 70 is started.

That is, when the injection filling is completed, the amount of the resin obtained by adding the amount of the cooling solidification shrinkage of the resin is fully filled (just pack) in the cavity 28. Further, in the compression step, the compression operation corresponding to the cooling solidification shrinkage of the resin is performed. Therefore, when the movable mold 30b returns to the same position as before the injection filling, it indicates that the cooling and solidification of the resin has been completed.

Here, if the setting of the timer 70 is set to zero, the mold is opened immediately and the product pick-up operation is started. After the product is taken out, if the molded product is exposed to the air in the atmosphere and air-cooled, and the deformation is expected, the timer 70 is used.
Can be prevented by increasing the set value of.

In the mold clamping device 1 according to the present embodiment,
The mold clamping is performed by the mold clamping cylinder 3 using the movable cylinder 2 to move the movable platen 20 back and forth. However, the present invention is not limited to this, and the mold clamping cylinder 3 may be provided behind the movable platen 20. Alternatively, an electric mold clamping mechanism may be used. Further, similar effects can be obtained even if the mold clamping device 1 itself is not a horizontal type as in this embodiment but a vertical type.

[0090]

As is apparent from the above description, in the present invention, the injection filling step and the compression step need only be a simple control method of controlling the injection pressure and the mold clamping pressure. It will be easier. Furthermore, because of the pressure control, a high-quality molded product can be stably supplied without being affected by fluctuations in molding conditions other than the pressure during molding. In addition, by using injection pressure control that allows injection filling,
The ideal injection filling control that has a continuous speed gradient according to the product shape, does not generate pack pressure, and enables short-time filling can be set very easily and automatically, so control operability is extremely easy. It is. Even when the injection filling is completed, the molten resin is in a just-packed state, so that there is no defect such as a flow mark caused by the discontinuity of the resin flow. Since the timing control is not required, the operability of the control can be further simplified. Also in the compression step, a compression action corresponding to the cooling, solidification, and shrinkage of the resin is provided, so that residual distortion and deformation can be extremely reduced, and a molded article of extremely high quality can be obtained. Since the holding pressure switching and the holding pressure control are not required from the injection filling control, the operability is simplified, and the completion of the injection filling can be easily and accurately detected, so that the control system is extremely simple. Since the compression action from the mold clamping side is added continuously and fluidly from the completion of injection filling to the switching of the compression process, the control of the compression process and the start of weighing after switching are simple control using a timer. As a result, the control system is extremely simple and the controllability of the molding is very easy. In addition, by controlling the mold clamping force in the compression process based on the point at which the mold position returns before injection filling, the cooling, solidification and shrinkage behavior of the resin can be grasped more accurately, so setting an appropriate cooling time Can further shorten the molding cycle and improve the quality of the molded product.

[Brief description of the drawings]

FIG. 1 is a control conceptual diagram of an embodiment according to the present invention.

FIG. 2 is a plan view of a mold clamping device.

FIG. 3 is a sectional view of the screw engagement adjusting device.

FIG. 4 is an explanatory view showing an operation state of a half nut.

FIG. 5 is a relationship diagram showing a relationship between a mold opening amount of a mold and a mold clamping pressure.

FIG. 6 is an explanatory diagram showing a state of injection compression molding including an injection filling step and a compression step from the start of injection filling to the completion of injection filling of the injection device.

FIG. 7 is a control conceptual diagram showing another embodiment similar to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold clamping device 2 moving cylinder 3 mold clamping cylinder 4, 5 internal piston 4 a, 5 a piston rod chamber side 4 b, 5 b piston head chamber side 5 c ram chamber 7 tie bar 8 screw portion or groove portion 10 fixing plate 11 screw mesh adjusting device 14 half Split nut opening / closing cylinder 17 Pressing member 20 Movable platen 22 (22a, 22b) Half nut 24 Insertion hole 26 Tie lock device 28 Cavity 30a Fixed mold 30b Movable mold 40 Injection device 41 Barrel 42 Screw 44 Nozzle 46 Injection cylinder 47 Forward / reverse rotation motor 48 Piston 50 Connecting plate 51 End plate 52 Ram cylinder 53 Ram 60 Control unit 61 Injection filling amount setting unit 62 Injection pressure setting unit 63 Injection control unit 64 Hydraulic control valve 65 Mold clamping force setting unit 66 Mold clamping control unit 67 Hydraulic control valve 68a, 68b Hydraulic Supply source 69 Injection and filling completion detection unit 70 Timer 71 Time setting unit 72 Comparison control unit 74 Mold position detection unit 75 Reference point setting unit 100 Adjustment plate 101 Connecting rod 102, 103 Stopper

Claims (6)

(57) [Claims] 1. An injection mechanism controls a cooling / solidification shrinkage amount of a resin in advance in an injection filling step, and controls an injection pressure with an injection pressure capable of filling a resin amount obtained by adding the shrinkage amount into a mold. On the mold clamping mechanism side, a mold clamping force that allows the mold to be opened to a mold opening amount corresponding to the amount of cooling, solidification, and shrinkage of the resin by the resin pressure filled in the mold cavity is added to the mold in advance. In addition, the injection compression molding method is characterized in that the mold clamping force is maintained until the resin is solidified by cooling even after the injection filling is completed. 2. The injection compression according to claim 1, wherein the injection pressure is controlled by controlling the injection pressure from the start to the completion of the injection filling to a constant pressure at which the injection can be performed so that the amount of shrinkage does not remain. Molding method. 3. The method according to claim 1, wherein the holding of the mold clamping force is continued until a time-out signal of a timer which starts when the injection driving force of the injection mechanism indicating the injection filling completion starts to increase sharply is reached. A characteristic injection compression molding method. 4. The method according to claim 1, wherein the holding of the mold clamping force is continued until a time-out signal of a timer that starts when the movement of the injection drive unit of the injection mechanism indicating the completion of injection filling is stopped is reached. Injection compression molding method. 5. The injection according to claim 1, wherein the holding of the mold clamping force is continued until a time-out signal of a timer activated when returning to a mold closing position before injection filling of the resin is reached. Compression molding method. 6. An injection control unit comprising an injection filling amount setting means and an injection pressure setting means for performing injection filling based on the two setting means, and a mold opening corresponding to a cooling solidification shrinkage amount of the resin by the injection filling. A mold clamping force setting unit that sets a mold clamping force that allows the mold to open to an amount, and a mold clamping control unit that performs mold clamping based on the mold clamping force setting unit,
When the injection driving force of the injection mechanism suddenly starts increasing, or when the movement of the injection driving unit stops, an injection filling completion detection unit that generates an injection filling completion signal, and a detection signal from the injection filling completion detection unit. A timer that starts based on a time setting unit that sets a pressure-holding / cooling time in the compression process;
An injection compression molding apparatus, comprising: a comparison control unit that compares a set value of the time setting unit with a timeout signal of the timer to generate control signals to the injection control unit and the mold clamping control unit, respectively.