JP3265923B2 - Injection compression molding method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of filling a mold cavity of a low-pressure mold with a molten resin, slightly opening the mold by the filled resin pressure, and then increasing the mold pressure by a mold clamping mechanism. TECHNICAL FIELD The present invention relates to an injection compression molding method and an injection compression molding apparatus which are designed to compress.

[0002]

2. Description of the Related Art Injection molding using an injection molding apparatus of a mold clamping mechanism for clamping with a hydraulic mold clamping cylinder has been performed according to the following procedure. (1) A stopper or the like is provided in the mold clamping mechanism, and the mold is mechanically locked by the stopper at a predetermined mold opening position. Alternatively, the amount of retreat of the mold to be opened by injection filling is limited by a stopper. The mold compression process after injection filling is performed by releasing the mechanical lock by the stopper. Alternatively, the compression step is performed by using a separately provided compression-clamping cylinder or the like. (2) A unit dedicated to compression is mounted between the movable platen and the fixed platen of the mold clamping mechanism, and the unit is provided with a mold opening holding and compression process. (3) The position of the movable platen or movable mold is detected, and mold clamping is performed with a low mold clamping force so that the mold is easily opened by injection filling. In the injection filling step, the mold clamping pressure or the injection speed is controlled so that the set mold opening amount and the mold opening speed are obtained.

[0003]

However, when such injection molding is performed, there are various problems as described below. (1) Since it is difficult to cope with a change in molding conditions such as a resin temperature during molding, the quality of a molded product varies, and a good product cannot be supplied stably. In addition, since a time lag occurs during the transition from the injection filling to the compression process, the flow behavior of the resin in the mold becomes discontinuous, resulting in defects such as flow marks, and it is difficult to obtain a high-quality molded product. It is. Further, the addition of a mechanical locking mechanism or a mold-clamping cylinder dedicated to compression increases the complexity and size of the molding machine, resulting in a significant decrease in productivity.

[0004] (2) Although the molding machine body does not require any major remodeling, the installation of the compression-only unit reduces the effective dimension in which a mold can be mounted (specification of the molding machine is reduced). Therefore, the correspondence to a wide variety of molded products is limited. Further, the compression-only unit is a considerably heavy object, and when the unit is mounted, damage to the molding machine such as deformation of the molding machine, abnormal wear of the sliding portion, and increased load on the drive system is large. Further, it requires connection of a drive source of the unit, connection of a control signal for obtaining operation timing with the molding machine, and the like, and operability is extremely low.

(3) Since injection filling is performed in a state in which a mold clamping force is applied in advance, the mold opening behavior is not exhibited until the mold clamping force <resin pressure due to the injection filling. As a result, before and after the mold opening behavior As a result, the flow state of the resin in the mold cavity changes, and although not as large as in the case of (1), defects such as flow marks tend to occur. Therefore, a method of setting an extremely small mold clamping force to facilitate the mold opening behavior can be considered, but in this case, the mold clamping force or the injection speed is strictly controlled so that excessive mold opening behavior does not occur. As a result, extremely high control responsiveness and control accuracy are required, which leads to an increase in cost and operability due to the complexity and sophistication of the control system.

[0006]

Means for Solving the Problems To solve such problems, it is possible to avoid unnecessary reduction in productivity due to an increase in the size of a molding machine, and to achieve high quality by simple pressure control of mold clamping force and injection pressure. In order to stably supply molded articles, in the method of the present invention, the fixed platen and the movable platen and the connecting plate are arranged in the axial direction of the tie bar, and a half nut is mounted between the movable platen and the connecting plate.
Further, the tie bar is provided with a screw portion or a groove portion to be fitted with the half nut, and the fixed plate is fixedly provided with a moving cylinder and a mold clamping cylinder connected to the tie bar. When performing injection compression molding using a mold clamping mechanism that applies a mold clamping force by moving the movable platen toward the fixed platen with the mold clamping cylinder while moving the movable platen in the direction, the movable platen is moved by the moving cylinder to the fixed platen side. After the mold is touched and the two halves are touched, the half nut is engaged and fixed to the thread or groove on the tie bar, and then the resin amount obtained by adding the cooling, solidification and shrinkage of the resin is injected into the mold cavity. Injection filling process of injection pressure control capable of filling and a mold clamping process of applying a mold clamping force that allows the mold to be opened by injection filling to a mold opening amount corresponding to the amount of cooling, solidification and shrinkage of the resin in the mold clamping cylinder. The carried conjunction with simultaneously, after detecting the injection filling completion, it was decided to carry out the compression step by boosted the clamping force of the mold clamping cylinder.

In the apparatus of the second invention, the fixed platen, the movable platen and the connecting plate are arranged in the axial direction of the tie bar, and have a half nut mounted between the movable platen and the connecting plate.
In addition, the tie bar is provided with a screw portion or a groove portion to be fitted with the half nut, and the fixed plate is provided with a mold clamping mechanism connected to the moving cylinder and the tie bar and fixedly provided with a mold clamping cylinder. An injection control unit that performs injection filling based on the set values of the amount setting unit, the injection pressure setting unit, and the two setting units is provided, and the mold is opened by injection filling up to the mold opening amount corresponding to the amount of cooling, solidification, and shrinkage of the resin. A mold clamping force setting unit that sets a mold clamping force that allows the mold clamping force to be set, and a mold clamping control unit that performs mold clamping based on the set value of the mold clamping force setting unit. Alternatively, a half-nut fixing detector that detects engagement and fixing to the groove and an injection start signal is transmitted to the injection controller based on a detection signal of the half-nut fixing detector, and a mold is sent to the mold clamping controller. Comparison that sends a closing start signal Control section, an injection filling completion detecting section for detecting the completion of injection filling, a timer started based on a detection signal of the injection filling completion detecting section, a time setting section for setting a mold clamping pressure increasing start time in the compression step, and the time setting. And a time control unit for comparing the set value of the unit with a timeout signal of the timer and transmitting a mold clamping pressure increasing start signal to the mold clamping control unit.

[0008]

The present invention is constructed as described above. After the half nut is engaged with and fixed to the thread or groove on the tie bar, the injection filling step and the mold clamping step are simultaneously performed in conjunction with each other. For the half nut and movable plate, the thickness (die height value) of both molds is calculated from the pitch of the screw or groove so that the half nut can be driven smoothly.
It is still in a state that has a gap, in other words, the mold clamping force is not yet applied until the half nut and the movable plate abut, so the mold opening behavior by injection filling is from the initial stage of filling. It occurs easily and continuously, and as a result, the flow state of the resin in the mold cavity also shows a continuous spread.

Further, by filling a resin amount to which the amount of cooling solidification shrinkage is added and applying a mold clamping force that allows a mold opening amount corresponding to the amount of cooling solidification shrinkage, at the time of completion of injection filling, Since the mold is almost completely filled with resin (just pack), the mold is not affected at all by the occurrence of defects such as flow marks caused by discontinuous resin flow in the mold. As a result, a complicated and sophisticated control system of the mold clamping force and injection filling conventionally required is not required, and further, the mold clamping pressure can be increased after the completion of the injection filling is detected in the compression process. Therefore, it is not necessary to perform the timing control that makes it difficult to start increasing the mold clamping pressure. In addition, during the injection filling step, the filling pressure is controlled so that the resin flow resistance in the mold cavity is small at the initial stage of filling, so that high-speed filling is performed. Because it is naturally decelerated, it has a continuous speed gradient automatically during resin filling,
In addition, an ideal natural filling flow (natural flow) that does not generate a pack pressure is obtained. As a result, the operability of the injection filling control becomes extremely easy. Furthermore, by simultaneously performing the mold clamping operation and the injection filling operation, the molding cycle can be shortened, and the productivity is greatly improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 relate to the present invention, FIG. 1 is an overall configuration diagram of an injection compression molding apparatus, FIG. 2 is a process procedure diagram of a molding operation, and FIG. 3 is an explanatory diagram of an injection filling / clamping operation of an injection compression molding method. is there.

As shown in FIG. 1, the injection compression molding apparatus 100 includes a mold clamping device 1, an injection device 40, and a control device 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 device 60 will be described. The control device 60 includes an injection filling amount setting unit 61, an injection pressure setting unit 6,
2. Injection control unit 63, hydraulic control valve 64, mold clamping force setting unit 6
5, mold clamping control section 66, time control section 67, hydraulic control valve 6
8, hydraulic pressure supply sources 68a, 68b, injection filling completion detection unit 6
9, a timer 70, a time setting unit 71, a comparison control unit 72, a half nut fixing detection unit 73, and the like.

The injection control unit 63 includes an injection filling amount setting unit 61
And an injection pressure setting unit 62, and is connected to a control device (not shown) for controlling the operation of the forward / reverse rotation motor 47 via a hydraulic control valve 64.
6, the time control unit 67, and the comparison control unit 72.
On the other hand, the mold clamping control unit 66 is connected to the mold clamping force setting unit 65 and the injection filling completion detecting unit 69 of the injection cylinder 46.
And a control command is transmitted to the mold clamping cylinder 3 through a hydraulic control valve 68. The time control unit 67 is connected to the time setting unit 71 and performs time control in injection control and mold clamping control. The half nut fixing detector 73 is connected to the half nut opening / closing cylinder 26, detects opening and closing of the half nut 22, and detects the opening and closing of the half nut 22.
2 sends a detection signal.

The operation of the injection compression molding apparatus 100 configured as described above will be described. First, after confirming the normally performed mold clamping operation and unloading operation, a test molding operation is performed. This test molding operation usually involves several “throwing-out”
Is performed, and the appropriate values of the injection filling amount, the injection pressure and the mold clamping pressure according to the characteristics of the resin are grasped to obtain information on the condition setting. After setting conditions in test molding operation,
Perform production molding operation. Specifically, the operation is performed according to the following procedure according to the operation procedure as shown in FIG. (1) The movable platen 20 is moved forward by the movable cylinder 2 toward the fixed platen 10 side, and after the two dies 30a and 30b touch, the drive of the movable cylinder 2 is stopped. (2) The half nut opening / closing cylinder 26 is driven to completely mesh and fix the half nut 22 and the screw portion or groove portion of the tie bar 7. Here, in advance, both molds 30a,
Rotating a motor previously connected by a chain so that the half nut 22 and the screw or groove of the tie bar 7 are completely meshed with each other based on the mold thickness (die height value) of 30b and the pitch of the screw or groove. By
Rotate the sprocket to adjust the amount of forward / backward movement of the adjustment shaft. (3) After detecting whether the screw portion or groove portion of the half nut 22 and the tie bar 7 are completely engaged and fixed by the half nut fixing detecting portion 73, the comparison control portion 72 transmits the mold clamping control portion 66 to the mold clamping control portion 66. A start signal is transmitted to the injection control unit 63, and the mold clamping operation and the injection operation are simultaneously performed simultaneously. At this point, the half nut 22
Is engaged with and fixed to the screw portion or groove portion of the tie bar 7 so that the driving of the half nut 22 is facilitated.
Since the half nut 22 and the movable platen still have a gap calculated from the die height value and the pitch of the screw portion or the groove portion, the mold clamping operation in this case is engaged and fixed to the tie bar 7 and the tie bar 7. Fix the split nut 22 to the fixed platen 10
Slide forward so that it is pulled out to the side, and split the nut 2
After the 2 comes into contact with the movable platen 20, a mold clamping force is applied. Therefore, since no mold clamping force has been applied yet at the initial stage of injection filling, the mold opening behavior due to injection filling occurs extremely remarkably, and the mold opening behavior is continuous from the initial stage of filling. That is, since the resin in the mold cavity 28 is filled under a very low pressure state, a state in which the pressure deviation of the resin due to the filling is extremely small is obtained, and the effect of preventing deformation such as deformation and warpage is further promoted. Further, by simultaneously performing the mold opening operation and the injection operation, the molding cycle can be shortened.

(4) The injection filling step comprises measuring the resin amount obtained by adding the cooling solidification shrinkage amount of the resin calculated according to the resin properties to the volume of the mold cavity 28 set by the injection filling amount setting section 61; The injection pressure is set based on one injection pressure value of the injection pressure condition with the best injection efficiency from the injection filling pressure range that can be filled into the mold cavity 28 and does not generate burrs set by the injection pressure setting unit 62. As a result, in the early stage of the injection, the flow resistance in the mold cavity 28 is small, so that the filling is performed at a high speed. In the late stage of the injection, the filling speed is naturally reduced due to the increase in the flow resistance in the mold cavity 28. An ideal natural filling flow (natural flow) having a specific velocity gradient and generating no pack pressure is automatically obtained. (5) The mold clamping process is performed based on a mold clamping force value that allows the mold to be opened up to the mold opening amount corresponding to the resin cooling shrinkage amount set by the mold clamping force setting unit 65. Note that the set mold clamping force value is reached before the injection is completed, and the control is performed so that the set mold clamping force value is maintained until the injection is completed. By doing so, the injection filling control is performed based on the measured value of the resin amount to which the amount of cooling, solidification, and shrinkage of the resin is added, and when the injection filling is completed, the resin in the mold cavity 28 is almost fully filled (just pack). Therefore, there is no defect such as a flow mark caused by the discontinuity of the resin flow velocity in the mold cavity 28. As a result, after detecting the completion of injection filling, it is possible to shift to the compression step by increasing the clamping pressure,
Since advanced timing control of the start of mold clamping pressure increase, which has been conventionally required, is not required, operability becomes extremely easy by simplifying the control system.

(6) Further, during the injection filling step, the injection control is performed in a so-called shot-cut state without leaving a cushion amount until the screw 42 reaches the forward limit by the pressure control of the injection cylinder 46. This makes it possible to extremely easily and accurately detect the completion of injection filling. This state will be described with reference to FIG. (7) From the injection filling start point (mold clamping start point) A to the injection filling completion point (timer start point) E, the injection is performed in accordance with the forward movement (injection speed) of the screw 42 so that the injection filling pressure is constant. The working oil pressure in the cylinder 46 is controlled to be constant.
When the injection is completed (point E), that is, when the screw 42 reaches the forward limit, the forward movement of the screw 42 stops (injection speed = 0), so that the working oil pressure value in the injection cylinder 46 temporarily rises sharply. Therefore, the detection of the completion of injection filling can be accurately grasped by either detecting the operating oil pressure value in the injection cylinder 46 or detecting the forward movement (injection speed) of the screw or piston. .

(8) When the injection / fill completion detecting section 69 detects the injection / fill completion, the timer 70 is started, and the time control section 67 determines the time-out signal of the timer 70 and the set value of the time setting section 71. Control the compression process. The following setting values are input to the time setting unit 71 in advance. That is, in FIG. 3, the compression start time t ₁ is an elapsed time for starting the mold clamping pressure increase and performing the compression step,
Set within the range from immediately after the injection is completed to the time the gate is sealed (measurement start). The metering start time t ₂ is set based on the gate sealing time, and based on the shut-off valve closing operation completion time in a molding machine incorporating a shut-off valve. The compression completion time t ₃ is set as a pressure-holding cooling time (compression completion time) by calculating the cooling and solidifying time of the resin based on the resin temperature, the mold cooling capacity, the shape of the molded product, and the like.

(9) In response to the time-out signal of the compression start time t ₁ , the time control section 67 sends a mold clamping pressure increasing start signal to the mold clamping control section 66 to apply a high pressure mold clamping force with the mold clamping cylinder 3 ( Compression step). In this case, a slight time lag occurs from the completion of the injection filling to the start of the compression process,
When the injection filling is completed, the resin in the mold cavity 28 is in a just-packed state, and the initial mold clamping force is continuously applied according to the cooling, solidifying, and shrinking behavior of the resin. There is no outbreak at all. Even in the shot-cut state, since the molten resin is filled in the nozzle 44 and the passage to the mold cavity 28 in a state having a set pressure value, there is almost no resin backflow in the compression step. (10) by time-out signal of the measurement start time t ₂ Similarly, the time control unit 67 by transmitting a measurement start signal to the injection control unit 63 starts the measurement operation. Further, in response to the time-out signal of the compression completion time t ₃ , the time control unit 67 transmits a compression completion signal to the mold clamping control unit 66 to take out the product after the mold opening operation and to start the next molding operation.

[0020]

As described above, in the present invention,
The following excellent effects can be obtained. (1) After the half nut is engaged and fixed to the screw portion or groove portion of the tie bar, the injection filling step and the mold clamping step are performed simultaneously, so that the mold clamping force is not yet applied at the initial stage of the injection filling. Therefore, the mold opening behavior due to injection filling becomes remarkable, and as a result, the pressure deviation of the resin in the mold cavity becomes extremely small, and a high quality molded product with extremely small deformation, warpage and residual distortion can be obtained in a short molding cycle. Can be (2) Injection filling is performed by injection-filling the amount of resin to which the amount of cooling solidification shrinkage is added, and by setting a mold clamping force that allows the mold to open to a mold opening amount corresponding to the amount of cooling solidification shrinkage. When the injection is completed, the compression process can be started after the injection filling is completed, because the molten resin is in a just-packed state and the initial clamping force applies a compression action corresponding to the cooling, solidification and shrinkage behavior of the resin. it can. As a result, the compression process requires only simple control by a timer, and a high-quality molded product can be obtained by an extremely easy operation. (3) Ideal injection filling control that has a continuous speed gradient according to the shape of the molded product, does not generate pack pressure, and can be filled in a short time by injection filling of injection pressure control that can be filled. Can be automatically set very easily, so that control operability is extremely easy.

[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 a process flowchart of a molding operation in an injection compression molding method according to an embodiment of the present invention.

FIG. 3 is an explanatory view of an injection filling and mold clamping operation 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 (half nut) (Opening / closing cylinder) 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 device 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 time control unit 68 hydraulic control valve 68a hydraulic supply source 68b hydraulic supply source 69 injection filling completion detection unit 70 timer 71 time setting unit 72 comparison control Unit 73 Half nut fixing detection unit 100 Injection compression molding device

Claims (2)

(57) [Claims] 1. A fixed plate, a movable plate and a connecting plate are arranged in the axial direction of a tie bar, a half nut is mounted between the movable plate and the connecting plate, and the tie bar is fitted with the half nut. The fixed platen is fixedly provided with a moving cylinder and a mold clamping cylinder connected to the tie bar.The moving cylinder moves the movable plate toward and away from the fixed platen, and the movable platen moves with the mold clamping cylinder. When performing injection compression molding using a mold clamping mechanism that applies a mold clamping force by pressing the board toward the fixed board side, the movable cylinder is advanced to the fixed board side by the moving cylinder, and both molds are touched. After engaging and fixing the half nut to the screw portion or the groove portion on the tie bar, an injection filling step of an injection pressure control capable of injection filling a resin amount obtained by adding a cooling solidification shrinkage amount of the resin into a mold cavity; Mold clamp The mold filling process that applies the mold clamping force that allows the mold to open by injection filling up to the mold opening amount equivalent to the amount of resin cooling solidification shrinkage is performed simultaneously, and the completion of injection filling is detected. Thereafter, a compression step is performed by increasing the clamping force of the clamping cylinder to perform a compression step. 2. A fixed platen, a movable platen and a connecting plate are arranged in the axial direction of a tie bar, and have a half nut mounted between the movable platen and the connecting plate. The fixed platen is provided with a mold clamping mechanism which is connected to the moving cylinder and the tie bar and is fixed with the mold clamping cylinder. The injection filling amount setting section and the injection pressure setting section And an injection control unit that performs injection filling based on the set values of the two setting units, and a mold clamping force that allows the mold to be opened by injection filling up to a mold opening amount corresponding to the amount of cooling, solidification, and shrinkage of the resin. And a mold clamping control unit that performs mold clamping based on the set value of the mold clamping force setting unit, and the half-split nut meshes with the screw or groove on the tie bar.
A split nut fixing detector that detects that the nut has been fixed,
A comparison control unit for transmitting an injection start signal to the injection control unit and transmitting a mold clamping start signal to the mold clamping control unit based on a detection signal of the half nut fixed detection unit, and an injection filling unit for detecting completion of the injection filling A completion detection unit, a timer that starts based on a detection signal of the injection filling completion detection unit, a time setting unit that sets a mold clamping pressure increase start time in a compression process, and a setting value of the time setting unit and the timer. An injection compression molding apparatus, comprising: a time control unit that compares a time-out signal and transmits a mold clamping pressure increasing start signal to the mold clamping control unit.