JP3154379B2 - 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 injection compression molding in which a mold cavity 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. The present invention relates to a method and an injection compression molding apparatus.

[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 a mold (movable mold) when the mold is slightly opened by injection-filled resin pressure. (2) The amount of mold opening movement of the mold is detected, and the mold clamping pressure and the injection speed of the mold clamping device are controlled so as to achieve the set mold opening amount and mold opening speed. (3) In the step of compressing the mold, precision molding and complicated shapes are performed by changing the mold clamping pressure such that the mold clamping operation proceeds at the set moving speed from the set mold opening amount. It is intended to mold a molded article or a thin-walled molded article. As described above, in the injection compression molding, the mold opening movement amount of the mold during molding is constantly detected, and based on the detection signal, the mold clamping mechanism and the injection mechanism are controlled so as to attain the set mold opening amount and the set mold opening speed. The feedback control which sends a command simultaneously to is implemented.

[0003]

However, the injection compression molding method and apparatus described above have the following problems. (1) Both control hardware and software have become complicated in recent years, and advanced control technology is required, and accordingly, operability has become extremely difficult. (2) It is difficult to select the optimal set values of the set mold opening amount and the set mold opening speed, and the flexibility to the fluctuation of the molding conditions such as the resin temperature during molding is controlled based on the set values. It is difficult to prevent variations. (3) It is difficult to control the timing of interlocking the mold clamping side and the injection side for controlling the mold opening amount and the mold opening speed according to the set values, and it is necessary to drive both at the same time. This leads to an increase in the size of the equipment and an increase in initial cost. In the present invention, such a problem is solved, unnecessary increase in size of the equipment is avoided, and the molding conditions are varied during molding by simple control of only the injection pressure and the mold clamping force pressure from the beginning of the production molding operation. It is intended to stably supply non-defective products that are not easily affected by the problem.

[0004]

Means for Solving the Problems To solve the above problems, in the present invention, in a method of injection compression molding of a resin, the amount of cooling, solidification, and shrinkage of the resin is grasped in advance during a test molding operation, and the amount of shrinkage is determined. The added resin amount is filled into the mold cavity, and the injection pressure is set to a pressure at which the resin amount can be filled into the mold cavity, and the mold opening when the injection amount is completed with the resin amount is completed. The mold clamping force of the mold clamping device is set so that the amount corresponds to the mold opening movement amount corresponding to the cooling, solidification shrinkage amount of the resin, and during the production molding operation, the injection pressure and the mold clamping set during the test molding operation are set. Injection filling was performed only by pressure control of force. Further, in the second invention, the injection compression molding apparatus includes an injection filling amount setting means for calculating a cooling solidification shrinkage amount of the resin and setting a resin amount obtained by adding the calculated cooling solidification shrinkage amount, and filling the resin amount. setting the injection pressure setting means and both said means for setting the injection pressure can be
An injection control unit that performs injection filling based on the set value, and a mold opening amount detection unit that detects a mold opening amount and a movable mold that moves up to a mold opening movement amount corresponding to the cooling, solidification, and shrinkage amount of the resin by injection filling. A mold clamping force setting unit that sets a mold clamping force that allows the mold to be opened, and a mold clamping control unit that performs mold clamping based on a set value set in the mold clamping force setting unit. Configuration.

[0005]

In the injection filling step, the injection pressure at which the amount of resin obtained by adding the amount of cooling, solidification, and shrinkage can be filled into the mold cavity is set. As the filling progresses, the resin flow resistance gradually increases and the filling speed is spontaneously reduced. As a result, a continuous speed gradient according to the mold cavity shape is automatically generated and no pack pressure is generated. An ideal natural filling flow is formed.
In addition, by setting a mold clamping force in the mold clamping device that allows the amount of resin that is expected to cool and solidify to shrink to the mold opening amount corresponding to the amount of cooling and solidifying shrinkage, the resin is filled when injection filling is completed. Since the mold cavity is almost completely filled (just-packed state), there is no occurrence of defects such as flow marks due to discontinuity of resin flow, and the quality of a dense and good molded product is ensured. Further, when the injection and filling are performed at the above-described set injection pressure and the set mold clamping force, the accuracy of reproducibility of the mold opening amount by the injection filling pressure is extremely high, and stable operation with high reliability is achieved. Therefore, by knowing the setting of injection pressure and mold clamping force through the test molding operation prior to the production molding operation, in the subsequent production molding operation, only the pressure control for the set injection pressure and mold clamping force can be easily performed. With good control, a good product of stable and uniform quality can be obtained from the beginning of operation.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 7 relate to an embodiment of the present invention, FIG. 1 is an overall configuration diagram of an injection compression molding apparatus, FIG. 2 is an injection pressure condition setting process diagram in an injection compression molding method, and FIG. Tightening force setting process diagram, Fig. 4
Is a graph showing the correlation between the mold clamping pressure and the mold opening amount, FIG. 5 is a working process diagram in the injection compression molding method, FIG. 6 is a data diagram showing the reproducibility of the mold opening amount, and FIG. It is a change transition diagram of each control condition.

As shown in FIG. 1, the injection compression molding apparatus 100 includes a mold clamping device 1, an injection device 40, and a control unit 60. The mold clamping device 1 includes a moving cylinder 2, a mold clamping cylinder 3, a tie bar 7, a fixed plate 10, a screw engagement adjusting device 11, a movable plate 20, a half nut 22, a tie bar locking device 26, a fixed mold 30a, and a movable metal. It is composed of a mold 30b, a connecting plate 50, and the like. A central convex portion of the movable mold 30b is fitted in a central concave portion of the fixed mold 30a, so that the movable mold 30b can move forward and backward slidably. Reference numeral 5a denotes a piston rod chamber, 8 denotes a screw portion (or groove portion), and 28 denotes a mold cavity.

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.
, So that the screw 42 rotates forward and backward.

Next, the control unit 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, a mold opening amount sensor 70, and a mold opening amount detecting unit 72. The injection filling amount setting means 61 and the injection pressure setting means 62 are connected to the injection control section 63, and the injection control section 63 controls the operation of the hydraulic control valve 64 for controlling the operation of the injection cylinder 46 and the operation of the forward / reverse rotation motor 47. Connected to control devices (not shown). Further, the mold opening amount detection unit 72 that receives a detection signal from the mold opening amount sensor 70 attached to the fixed mold 30a includes a mold clamping force setting unit 6.
5, the clamping force setting means 65 is also connected to a clamping control unit 66, and the clamping control unit 66 is connected to a hydraulic control valve 67 for controlling the operation of the clamping cylinder 3.
Here, 68a and 68b are simplified hydraulic supply sources.
In addition to the methods described above, the mold opening amount detection means detects the position of the movable platen, detects the stroke of the mold clamping cylinder when the mold clamping mechanism is hydraulically driven, and detects the degree of reverse rotation of the electric motor when the electric clamping mechanism is used. It is also possible to detect the elongation of the tie bar.

In the present embodiment, the mold opening amount is detected only during the test molding operation, and in order to avoid significant modification of the molding apparatus, to increase the detection accuracy, etc. It is to be detected at a close position, and the fixed mold 3
0a employs a position sensor 70a and a mold opening sensor 70 comprising a target 70b attached to the movable mold 30b.
In consideration of detection accuracy, handling, and versatility, for example, a commercially available position sensor 70a of a magnet detachable type was used.

The operation of the injection compression molding apparatus 100 configured as described above will be described. First, a test molding operation is performed after confirming a mold clamping operation and an injection operation which are usually performed before starting the production molding operation. In this test molding operation, a test ejection, which is usually called "discarding ejection", is performed, and conditions are set by grasping appropriate values of the injection filling amount, the injection pressure, and the mold clamping pressure. Specifically, as shown in FIG. 2, appropriate injection pressure conditions are set by the following procedure. The movable platen 20 is advanced to the fixed platen 10 side by the movable cylinder (mold opening / closing cylinder) 2, and the movable mold 30b is moved.
And stop at the position where the fixed mold 30a touches (the stop position is detected by an increase in the hydraulic pressure of the mold opening / closing cylinder stroke). The tie bar 7 is locked by being driven by the half nut 22 and engaging with the groove of the tie bar 7 (the optimal engagement position has already been set). The mold is clamped between the movable mold 30b and the fixed mold 30a by being driven by the mold clamping cylinder 3. The mold clamping force at this time is tentatively set, is roughly determined from the resin physical properties and the projected area of the cavity, and is set slightly higher in anticipation of the injection pressure range to be changed when the injection pressure setting conditions are determined (injection). It is a necessary condition that the resin does not leak when the movable mold 30b is backed by the pressure). After completion of the mold clamping, the position of the movable mold 30b is detected and set as a reference point (detecting the mold opening amount for preventing the movable mold 30b from being significantly backed by injection filling and generating burrs in advance. For). At the time of injection filling, the injection filling amount setting means 61 sets a resin amount obtained by adding a cooling solidification shrinkage amount of the resin calculated in advance based on a mold cavity volume and resin physical properties as a measured value. In addition, injection filling is performed by injection pressure control capable of filling and shot-off control without leaving a cushion amount, so that injection filling completion detection can be accurately performed by monitoring the injection cylinder drive oil pressure and the injection speed.
That is, since the driving oil pressure of the injection cylinder is controlled to a constant value in accordance with the forward movement of the screw shaft so that the injection filling pressure becomes constant, the forward movement of the screw shaft is stopped when the injection filling is completed. The driving oil pressure of the injection cylinder, which has been continued, rises suddenly temporarily. Therefore, the injection filling is completed when the injection cylinder driving oil rapidly rises or when the injection speed becomes zero. Similarly, regarding the injection filling pressure, an approximate injection filling pressure is determined from the mold cavity volume and the resin properties, and is set as a temporary set value in the injection pressure setting means. At this time, it is set low in anticipation of occurrence of burrs and the like. Injection filling is performed based on the set value, the injection pressure set value is increased and corrected until filling becomes possible, and the above operation is repeated. When the movable mold 30b is largely retracted by injection filling (when burrs are expected), an operation of increasing the mold clamping force is performed, and the above injection pressure setting step is repeated. If filling is possible, the injection pressure value at that time is input to the injection pressure setting means as the injection pressure set value S, and the injection pressure setting adjustment is completed. Thus, the desired injection pressure set value S is determined.

Next, an appropriate setting of the mold clamping force condition will be described. FIG. 3 shows an operation procedure of the mold clamping force setting step, and the mold clamping force condition is set according to the following procedure. After setting the proper injection pressure condition, the mold clamping force is changed under the injection condition of the set injection pressure set value S, and an appropriate mold clamping force value is obtained from the mold clamping force at that time, the mold opening amount, and the quality of the molded product. Next, the movable mold 30b is advanced, and then the mold is touched to lock the tie bar. The mold clamping cylinder 3 is driven to perform mold clamping. After the completion of the mold clamping, the position of the movable mold 30b is detected to set a reference point (to detect the amount of mold opening when the injection filling is completed). The injection filling is performed by pressure control of the injection filling amount already set by the injection filling amount setting means 61 and the injection pressure set value S obtained in the appropriate injection pressure condition setting step. The mold opening amount at the time of completion of the injection filling is detected, and the quality of the molded product is determined. The above operation is repeated by changing the mold clamping force to obtain the relationship between the mold clamping force and the mold opening amount as shown in FIG. In the case of ( ¹ ), a box of 250 L × 300 W × 50 H × 2 t (projection area: 750 cm ² ) is obtained as a molded product, and the cavity 28 is relatively flat and has a vertical rib on the side of the box. The case where a case or a document case is formed is shown. , The cavity 28
This figure shows a case where a molded product such as a lens or a disk, which is flat and not a rib structure but a very flat material such as a thin material, is formed. In the case of, the surface of the cavity 28 has a complex shape,
For example, a case where a molded article such as an instrument panel or a bumper is formed is shown. That is, when the injection filling amount and the injection pressure value are set to a constant condition, the mold opening amount becomes smaller as the mold clamping pressure value is increased from a low pressure to a high pressure, and the left and right parallel movements of FIG. The inflection points at which the rate of decrease in the mold opening suddenly decreases in the process of increasing the mold clamping pressure (A, A ′,
A ″) appears. As a representative, in the region B where the mold clamping pressure value is smaller than the inflection point A, the movable mold 3 is moved by the kinetic energy of the resin flow during injection filling.
0b is larger than the fixed mold 30a, so that a large gap is formed 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 the process proceeds from the completion of the injection filling to the compression step, and 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 the region C where the mold clamping pressure value is larger than the inflection point A, the movable mold 30b can absorb the kinetic energy of the resin flow during the injection filling without moving relative to the fixed mold 30a. When the injection and filling are completed, the resin is completely filled into the cavity 28 (just pack). Further, in the above-mentioned C region, there is no occurrence of defects such as a flow mark because the resin does not reflow even when shifting to the compression step, and it is unnecessary to control the injection step and the compression step in conjunction with each other. Becomes

Based on the above results, the mold clamping pressure setting range was selected in the C region. That is, the region where the mold clamping pressure value is large also in the region C is consequently the cavity 2
8, the resin pressure in the cavity 28, which is one of the advantages in the injection compression molding, cannot be reduced. Therefore, the cavity 28 determined to be appropriate from the shape of the molded product and the physical properties of the resin. The maximum value (upper limit value) of the mold clamping pressure value is defined from the allowable maximum value of the resin pressure within the range. The mold clamping pressure value was used. By determining such a relationship between the mold clamping pressure and the mold opening amount, a mold clamping force set value K that allows the mold to be opened up to the mold opening amount corresponding to the solidification shrinkage amount of the resin by injection filling is accurately found. Then, it is input to the mold clamping force setting means to complete the mold clamping force setting adjustment. In setting the appropriate mold clamping pressure value,
As shown in FIG. 4, the inflection point A is determined by determining the presence / absence of a defect such as a flow mark by quality inspection of a molded product after molding, although the definition is made based on the mold opening amount.

After the proper injection pressure set value S and the mold clamping force set value K are set by the test molding operation as described above,
In the production molding operation process, as shown in FIG. 5, production molding is performed only by controlling the injection pressure and the mold clamping force. The procedure and results are described below in detail. Move the movable mold 30b forward and touch both molds,
After that, tie-bar lock is performed. The mold is clamped with the mold clamping force set value K. After the completion of the mold clamping, the amount of resin measured by the injection filling amount setting means 61 is subjected to injection filling with the injection pressure set value S. With the injection filling, the movable mold 30b shows the mold opening behavior, and when the filling is completed, the just-packed state is obtained with the mold opening amount corresponding to the amount of solidification shrinkage of the resin. Here, with only the pressure control of the mold clamping force set value K and the injection pressure set value S, the reproducibility and the variation of the setting of the mold opening amount were examined in the actual molding test of 30 shots under the above-mentioned conditions (in FIG. 4). As a result, the result is as shown in FIG. 6 correspond to those in FIG. 4 and FIG.
The symbol ● in FIG. 4 corresponds to that in FIG. 4, and the symbol ▲ in FIG. 6 corresponds to that in FIG. As is clear from FIG. 6, very good reproducibility and variation were obtained. That is, under all the conditions, the variation of the mold opening amount in 30 shots is controlled with extremely high accuracy of about 10 to 20 μm with respect to each set mold opening amount, and the appropriate mold clamping force range obtained in FIG. The allowable range of the mold opening corresponding to (D region), that is, the allowable range of quality is 100 to 150 μm for each condition, and it is confirmed that the variation of the mold opening only by the pressure control is small enough to cause no problem. Was done. Therefore, the mold opening amount can be controlled with extremely high accuracy only by controlling the injection pressure set value S and the mold clamping force set value K. As a result, a high-quality molded product can be supplied stably. Was. After the injection is completed, the compression process is controlled based on the above-described detection signal of the injection filling completion detection. These states will be described with reference to FIG. That is, mold clamping is performed with the mold clamping force set value K (mold clamping step-up section). After the mold clamping, the injection filling is performed under the injection pressure control of the injection pressure set value S (injection filling section). At this time, since the injection filling is in the cutoff state, the completion of the injection filling can be accurately detected by detecting the driving oil pressure or the injection speed of the injection cylinder. By detecting the completion of injection filling,
Start weighing (time-out gate closing time or shut-off valve closing operation completion time), hold pressure / cooling time (compression completion time), start mold clamping pressure increase (when mold clamping multi-stage pressure control is required) , The same as when starting weighing).

[0015]

As described above, the method and apparatus of the present invention have the following excellent effects. (1) Since the injection pressure and mold clamping force are set during the test molding operation before the production molding operation, high quality is achieved only by simple control of the injection pressure and mold clamping force pressure set from the beginning of the subsequent production molding operation. Stable molded products can be supplied stably. (2) The mold opening can be controlled with high accuracy only by the set injection pressure and mold clamping force pressure control, eliminating the need for advanced control techniques such as feedback control of detection signals, resulting in significant cost reduction of the molding machine. Production up. (3) In addition, by setting the injection pressure to be capable of injection filling, an ideal injection filling that has a continuous speed gradient according to the product shape, does not generate pack pressure, and can be filled in a short time. Since the control can be automatically set very easily, the operability of the control is extremely easy. (4) Even when the injection filling is completed, since the molten resin is in the just-packed state, there is no defect such as a flow mark due to the discontinuity of the resin flow, and as a result, when switching from the injection filling step to the compression step, Since extremely sophisticated timing control is not required, the operability of the control can be further simplified.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an injection compression molding apparatus according to an embodiment of the present invention.

FIG. 2 is an injection pressure condition setting process chart in the injection compression molding method according to the embodiment of the present invention.

FIG. 3 is a process chart for setting a clamping force condition in the injection compression molding method according to the embodiment of the present invention.

FIG. 4 is a graph showing a correlation between a mold clamping pressure and a mold opening amount in the injection compression molding method according to the embodiment of the present invention.

FIG. 5 is an operation process diagram in the injection compression molding method according to the embodiment of the present invention.

FIG. 6 is a data diagram showing reproducibility of a mold opening amount in an injection compression molding method according to an example of the present invention.

FIG. 7 is a change transition diagram of each control condition in the injection compression molding method according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold clamping device 2 Moving cylinder 3 Mold clamping cylinder 7 Tie bar 8 Screw part (groove part) 10 Fixed platen (fixed platen) 20 Movable platen (movable platen) 22 Half nut (half nut) 26 Tie bar locking device 28 Mold cavity 30a Fixed mold 30b Movable mold 40 Injection device 41 Barrel 42 Screw 43 Hopper 44 Nozzle 46 Injection cylinder 47 Forward / reverse rotation motor 48 Piston 60 Control unit 61 Injection filling amount setting means 62 Injection pressure setting means 63 Injection control unit 64 Hydraulic control Valve 65 Clamping force setting means 66 Clamping control unit 67 Hydraulic control valve 68a Hydraulic supply source 68b Hydraulic supply source 70 Mold opening sensor 70a Position sensor 70b Target 72 Mold opening detecting unit 100 Injection compression molding device K Mold clamping force setting Value S Injection pressure set value

Claims (2)

(57) [Claims] In a method of injection compression molding of a resin, the amount of resin which is cooled, solidified and shrunk in a test molding operation is determined in advance, and the amount of resin obtained by adding the amount of shrinkage is filled in a mold cavity. The amount of resin is set to a pressure that can be filled into the mold cavity, and the amount of mold opening when filling the amount of resin with the injection pressure is equal to the amount of mold opening movement corresponding to the amount of cooling, solidification, and shrinkage of the resin. Injection-compression molding, wherein the mold-clamping force of the mold-clamping device is set so as to perform injection-filling only during production molding operation by controlling the injection pressure and the pressure of the mold-clamping force set during the test molding operation. Method. 2. An injection filling amount setting means for calculating a cooling solidification shrinkage amount of a resin and adding the calculated cooling solidification shrinkage amount, and an injection pressure setting an injection pressure at which the resin amount can be filled. A setting unit and an injection control unit for performing injection filling based on set values set in the both units, a mold opening amount detection unit for detecting a mold opening amount, and the cooling, solidification and shrinkage of the resin by injection filling. Mold clamping force setting means for setting a mold clamping force that allows the movable mold to open the mold up to the mold opening movement amount corresponding to the amount, and mold clamping based on the set value set in the mold clamping force setting means. Injection compression molding equipment with a mold clamping control unit.