JP3282435B2 - Injection press molding method and injection press molding apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention holds a mold with a predetermined gap opened, fills a mold cavity with a molten resin, closes the gap with a mold clamping device after the filling is completed, and compresses the mold. And an injection press molding apparatus.

[0002]

2. Description of the Related Art When performing injection press molding using an injection molding apparatus that performs mold clamping by a toggle mechanism, (1) mold clamping is completed in a state where the toggle mechanism is fully extended, and in this state, a predetermined amount is applied to a mold. Keep a gap. Then, after the molten resin is injected and filled into the mold, compression is performed by a hydraulic cylinder for compression or the like separately provided on the movable platen or the fixed platen. (2) In the toggle-type mold clamping mechanism, the crosshead position of the toggle mechanism and the displacement of the movable platen (the mold opening amount) are set so that a predetermined gap is secured in the mold while the toggle mechanism is not fully extended. After stopping the toggle mechanism by controlling based on the set value converted to the position of the crosshead using the geometrical relationship of the amount and the clamping force), and closing the mold, the molten resin is injected and filled into the mold cavity. Thereafter, the toggle mechanism is re-driven to make it in the fully extended state, thereby performing compression.

[0003]

The conventional injection compression molding has the following problems. First, in the method of (1) closing the mold with the toggle mechanism fully extended and injecting and filling the molten resin into the mold in this state, no special modification is required on the toggle mechanism side. In addition to the toggle mechanism, a dedicated hydraulic cylinder or the like for compression is required, resulting in increased complexity and cost of the molding machine. (2) In the method of controlling the mold clamping with a set value obtained by converting the mold opening amount and the mold clamping force into the crosshead position based on the geometric relationship of the toggle mechanism, the toggle mechanism as described in (1) above is used. Although a separate hydraulic cylinder for compression is not required, the geometric relationship between the crosshead position of the toggle mechanism and the displacement of the movable platen, in other words, the mold opening and mold clamping force, depends on the thickness of the mold to be mounted. The relational expression exists infinitely depending on the combination of the die thickness setting value and the die height adjustment value that increases or decreases the maximum generated mold clamping force at the completion of mold clamping according to the size of the mold. It must be calculated based on geometrical relationships, and the operability is extremely poor and impractical. If the geometrical relationship of the toggle mechanism is programmed and a means for automatic calculation processing is incorporated to obtain a desired result by the calculation processing of the number of combinations of various variables close to infinity, a software and hardware There is a problem that it is unavoidable to increase the complexity and size, which increases the cost and is not appropriate. (3) Further, in all of the conventional methods, the injection filling is performed after the mold is set at the mold opening position.
In addition, when the toggle mechanism is operated at a high speed, accurate position stop cannot be performed due to inertial force, resulting in low-speed operation.As a result, the molding cycle tends to be equal or longer than that of a normal molding method. Is low. The present invention has been made in view of the above problems, and an object of the present invention is to provide a simple control of only the injection pressure and the pressure of the mold clamping cylinder hydraulic pressure without significantly modifying the existing molding machine of the toggle mechanism. By controlling, high-precision injection press molding can be performed, and a non-defective product can be supplied stably in a shorter molding cycle.

[0004]

In order to solve the above-mentioned problems, in the method of the present invention, the amount of cooling, solidification and shrinkage of the resin is determined in advance by using an injection molding apparatus which performs mold clamping via a toggle mechanism. In the injection filling step, the injection pressure is controlled by an injection pressure capable of filling the mold cavity with the amount of resin obtained by adding the shrinkage amount during the injection filling step, and the mold opening amount corresponding to the shrinkage amount is previously determined during the mold clamping step. Is set by the stroke of the mold clamping cylinder connected to the toggle mechanism, and the procedure for setting the mold opening amount is such that the movable platen is once advanced and the molds are retracted from the state where both molds are touched to the mold opening amount. In the injection filling step, the resin is injected into the mold cavity during the retreating operation of the movable plate, and after the injection filling is completed, the movable plate is advanced to apply a mold clamping force. Further, in the second invention, the procedure for setting the mold opening amount is such that the state in which both molds are touched is detected via a mold clamping force detection unit incorporated in the tie bar, and the mold clamping cylinder coupled with the toggle mechanism is detected. After the stroke is set to the origin, the mold opening amount corresponding to the amount of resin solidification shrinkage is set by the stroke retreat amount of the mold clamping cylinder from the origin, and the operation of the mold clamping cylinder is performed so as to maintain the set retreat position. We decided to control the oil pressure. Further, the apparatus according to the third aspect of the present invention includes an injection filling amount setting unit and an injection pressure setting unit, and an injection control unit for performing injection filling based on the two setting units, and a mold corresponding to the amount of cooling, solidification and shrinkage of the resin. Mold opening amount setting means for setting the opening amount,
A mold opening detecting unit that detects the mold opening of the mold, a mold clamping cylinder stroke sensor that detects the stroke of the mold clamping cylinder, and a mold clamping force that incorporates detection of the mold touch point in the mold clamping process into a tie bar. A mold touch point setting unit for setting a stroke of a mold clamping cylinder to an origin based on a detection signal of the mold clamping force detection unit performed by a detection unit, and a setting value of the mold opening amount setting means and a value of the mold opening amount detection unit. A mold clamping control unit that compares a detection signal and a detection signal of a mold clamping cylinder stroke sensor to control a stroke of a mold clamping cylinder connected to a toggle mechanism to perform mold clamping, and the mold touch point setting unit; Has a function of generating a mold opening amount setting start signal to the mold clamping control unit after completion of the origin setting and generating an injection start signal to the injection control unit. A detection unit, and configured to have a comparison control unit for generating a mold clamping start signal to the clamping control unit based on a detection signal from the injection filling completion detecting unit.

[0005]

In the injection filling step, the filling is controlled so that the filling can be performed at a high speed in the early stage of filling because the flow resistance of the resin in the mold cavity is small, and the flow resistance of the resin increases in the later stage of filling. Since the speed is naturally reduced, an ideal natural filling flow (natural flow) which has a continuous speed gradient automatically during resin filling and does not generate pack pressure can be obtained. Also, by filling the amount of resin to which the amount of cooling solidification shrinkage of the resin is added, and by setting the mold opening amount corresponding to the amount of cooling solidification shrinkage of the resin, even at the time of completion of injection filling, the resin is almost completely filled into the mold. Since it is in a state of full filling (just pack), the switching of the mold clamping start is not affected at all by the occurrence of defects such as flow marks due to the discontinuity of the resin flow velocity in the mold. Therefore, complicated and sophisticated timing control of the mold clamping start conventionally performed becomes unnecessary. In addition, since the mold clamping force is detected by the mold clamping force detector built into the tie bar, highly accurate mold clamping force can be directly detected without being affected by mold thickness setting and die height adjustment. The touch state of the mold as a reference when setting the mold opening amount can be stably detected with high accuracy and the mold opening amount can be set very easily. In addition, by performing the injection filling process in parallel with the mold opening setting operation, high-speed operation is possible up to the touching state of the mold for most of the mold clamping operation time, thus shortening the molding cycle. As a result, productivity is significantly improved.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 relate to an embodiment of the present invention, FIG. 1 is an overall configuration diagram of an injection molding machine, and FIG. 2 is a state explanatory diagram of an injection press molding method. The upper half of the injection molding machine in FIG. 1 shows a state at the time of setting the mold opening amount before the compression step, and the lower half shows a state of completion of mold clamping during the compression step.

As shown in FIG. 1, an injection molding machine 100 for performing an injection molding press is roughly composed of a mold clamping device 20, an injection device 40, and a control unit 60.
Are the link housing 1, fixed plate 2, movable plate 3, mold clamping cylinder 8, toggle mechanism 6 (toggle link 6a, mid link 6b, crosshead link 6c), crosshead 7, piston rod 9, guide rod 10, gold It comprises a mold 4 (movable mold 4a, fixed mold 4b), cavity 5, tie bar 11, and the like.

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 controller 63, hydraulic control valve 64, pressure sensor 6
5. Hydraulic control valve 67, hydraulic supply sources 68a, 68b, injection filling completion detecting section 69, timer 70, time setting section 71, comparison control section 72, mold clamping control section 73, mold clamping cylinder stroke sensor 74, mold opening amount Detector 75, mold opening amount setting means 7
6, a mold clamping force detecting unit 77, a mold touch point setting unit 78, and the like. 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). The operating oil pressure in the injection cylinder 46 is detected by a pressure sensor 65 and sent to a mold clamping control unit 73 via an injection filling completion detecting unit 69, a timer 70, and a comparison control unit 72. The position information detected by 74, the mold opening information detected by the mold opening detecting unit 75, and the mold clamping force information detected by the mold clamping force detecting unit 77 incorporated in the tie bar 11 are respectively set to the mold opening amount. Sent to the means,
An operation signal is transmitted to the mold clamping control unit, and an operation command is given to a hydraulic control valve 67 that controls the mold clamping cylinder 8. Note that the mold clamping force detection unit 77 is incorporated in the tie bar 11, and for example, a load meter or the like is used. The mold opening amount detection unit 75 employs an encoder or a linear scale, and measures the position at the movable platen. The mold clamping cylinder stroke sensor 74 is attached to the piston rod 9 of the mold clamping cylinder 8, and employs an encoder and a linear scale.
Also, a line is provided so that touch information in the mold touch point setting unit 78 is immediately sent to the mold clamping control unit 73 and the injection control unit 63.

The operation procedure of the injection press molding method in the injection molding machine 100 configured as described above will be described below. First, the injection filling amount setting means 61 sets the resin amount obtained by adding the cooling solidification shrinkage amount of the resin calculated according to the resin physical properties to the volume of the cavity 5 defined by the fixed mold 4b and the movable mold 4a as a measured value. At the same time, the injection pressure setting means 62 sets the injection pressure condition with the highest injection efficiency from the injection filling pressure range in which the cavity 5 can be filled and does not generate burrs. At the same time, based on the set measurement value and injection pressure value, the volume of the cavity 5 and the projected area of the cavity, a mold opening amount corresponding to the amount of cooling, solidification and shrinkage of the resin is set by the mold opening amount setting means 76 when the injection filling is completed.

That is, a state in which the molten resin is almost completely filled in the mold 4 when the injection filling is completed (just pack) is defined as an appropriate mold opening amount. By doing so, when transitioning from the completion of injection filling to the compression step, there is no occurrence of defects such as flow marks due to no change in resin flow, and it is not necessary to link the injection step and the compression step. Absent.
In addition, when the mold opening amount is set to be larger than the appropriate mold opening amount, a large gap is generated between the filled resin and the cavity at the time of completion of the injection filling, so that the flow speed of the resin becomes discontinuous when moving to the compression process, Defects such as flow marks occur. In this case, a molding method that is extremely difficult to control, such as linking the injection step and the compression step, is required.
Conversely, if the opening amount of the mold is extremely small, the flow resistance of the resin in the cavity becomes large, and molding defects such as short shots are likely to occur.

After completing the above-described initialization, the molding operation is started. The molding operation is performed according to the following procedure, as shown in FIG. (1) The mold clamping control unit 73 controls the operation of the mold clamping cylinder 8 to perform mold clamping based on the set value of the appropriate mold opening set by the mold opening setting means 76. (2) First, the origin is set at the time of setting the mold opening amount (the mold touch state). The detection of the mold touch state during the mold clamping operation (that is, the detection of the mold clamping force) is performed by the mold clamping force detecting unit 77 incorporated in the tie bar 11. The advantages are as follows. Tie bar 1 which is the principle of generation of mold clamping force of toggle mechanism 6
Since the elongation (stress) behavior of No. 1 is directly measured, the measurement accuracy is the highest. There is no disadvantage in the conventional method of calculating based on the geometric relationship of the toggle mechanism 6 (accumulation of operation programs close to infinity, low accuracy due to operation estimation). Extremely good handling because it is independent of the mold mounting area.

(3) The stroke of the mold closing cylinder in the state of touching the mold is reset to zero and the origin is set. Next, while detecting the amount of movement of the mold 4 by the mold opening detection unit 75, the mold 4 is retracted to the position of the appropriate mold opening. In this embodiment, the detection of the moving amount of the mold 4 is performed by the movable platen 3 for the following reason.
Was measured. Since no mold clamping force is generated, there is almost no deformation of each member, and the amount of movement between the mold 4 and the movable platen 3 is one-to-one. Very easy to handle because it is independent of the mold mounting area. (4) The stroke of the mold clamping cylinder 8 when the mold 4 is retracted to the position of the proper mold opening is detected by the mold clamping cylinder stroke sensor 74, and thereafter, the control of the mold opening is performed by using the detected signal value. Do. That is, the hydraulic pressure of the mold clamping cylinder is controlled so as to keep the detection signal value (clamp cylinder position holding control). Here, the characteristics of the toggle mechanism 6 (the position fluctuation of the movable platen 3 is 1 / several tens mm or less even if the mold clamping cylinder stroke fluctuates by about 1 mm (the relationship between S and t in FIG. 1). The accuracy of setting the amount is extremely high, and the actual mold clamping cylinder stroke can be held with an accuracy of 1 mm to 1/10 mm.

(5) The above (2) to (4) may be set once before the molding operation unless the mold and the set value of the mold clamping force in the compression step (by adjusting the die height) are changed. . In the actual molding operation, the mold is touched at the high speed until the mold touch state (origin) and the stroke position of the mold clamping cylinder corresponding to the appropriate mold opening amount are reached. Thereafter, the mold is retreated at a low speed to the mold opening position, and the injection filling operation is performed in parallel. The mold opening setting operation needs to be completed before the injection filling is completed. (6) After the mold touch state, the mold touch point setting unit 78 sends a mold opening amount setting start signal to the mold clamping control unit 73 and sends an injection start signal to the injection control unit 63. Here, the injection filling operation is performed by the injection control section 63 based on the resin metering value set by the injection filling amount setting means 61 and the injection pressure setting means 62 and the injection filling pressure based on the set value of the injection filling pressure. Perform filling. That is, in the early stage of injection, the flow resistance in the cavity 5 is small, so that high-speed filling is performed. In the late stage of injection, the filling speed is naturally reduced with an increase in the flow resistance in the cavity 5, resulting in a continuous speed gradient. And
In addition, an ideal natural filling flow (natural flow) that does not generate a pack pressure is obtained. Further, in the present embodiment, during the injection filling step, the injection control is performed such that the screw 42 is cut off without leaving a so-called cushion amount until the screw 42 reaches the forward limit by pressure control of the injection cylinder 46. By doing so, the detection for confirming the completion of injection filling described later is extremely easy and accurate, and the weighing and injection filling control are also simplified.

(7) After the injection filling is completed (at this point, the mold opening setting operation has already been completed and the proper mold opening amount is kept), the compression step is performed on the mold clamping side. Here, since the molten resin in the mold is in a just-packed state after the completion of the injection filling, if compression (mold clamping) is started following the completion of the filling, no defect such as a flow mark is generated. In addition,
If the operating oil pressure in the injection cylinder 46 is increased with compression (the injection cylinder 46 does not move forward), the nozzle 4
Since the resin is filled in the passage from inside 4 to cavity 5, the backflow of the resin in the mold can be completely prevented. (8) The detection of the completion of the injection filling is obtained by a change in the operating oil pressure value in the injection cylinder 46 or a change in the forward movement (injection speed) of the injection piston 48 in the above-described cutoff state. That is, since the working oil pressure value in the injection cylinder 46 is controlled to be constant along with the forward movement of the screw 42 so that the injection filling pressure is constant from the start of the injection filling to just before the injection is completed, When the screw 42 reaches the forward limit, the forward movement of the screw 42 stops, and the operating oil pressure value in the injection cylinder 46 temporarily and rapidly rises. Therefore, 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 injection piston 48 is stopped, the completion of the injection filling may be detected. Furthermore, it is also possible to use a method for confirming and detecting the completion of injection filling as described above in combination.

(9) When the injection / fill completion detecting section 69 detects the completion of the injection / filling operation, a signal of the mold closing start is generated to the mold closing control section 73 and the timer 70 is started to control the compression process. Here, the measurement start time and the holding pressure cooling time are input to the time setting unit 71 in advance. The start of metering is set on the basis of the gate sealing time, and in a molding machine incorporating a shut-off valve, the shut-off valve closing operation completion time is set as a reference. The holding pressure cooling time is calculated as the compression solidification time of the resin based on the resin temperature, the mold cooling capacity, the shape of the molded product, and the like, and set as the compression completion time. (10) Timeout signal of timer 70 and time setting section 7
The set value of 1 is compared by the comparison control unit 72, and when it is found that each set value has been reached, a measurement start signal is output to the injection control unit 63, and a compression completion signal is output to the mold clamping control unit 73. After the product is removed following the mold opening, the next molding operation is started. (11) The value of the mold clamping force in the compression step is added for the purpose of improving the transferability of the molded product, and is combined with the reduction of the mold clamping force which is one of the advantages of injection press molding. Within the maximum mold clamping pressure range, for example, the transferability of the molded article after molding is evaluated, and the necessary minimum mold clamping force value is set in advance.

[0017]

As is apparent from the above description, in the present invention, the injection filling step and the compression step need only be performed by a simple control method of controlling the injection pressure and the mold cylinder pressure, so that the operability is improved. It becomes very easy. 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, making control operability extremely easy. is there. 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. Injection filling control is injection pressure control and filling is performed without leaving a cushion amount, so that injection filling completion detection can be detected easily and accurately, and mold clamping start control can be simplified. The control of the compression process and the start of weighing can be performed by simple control using a timer, and a high-quality molded product can be obtained by an extremely easy operation. Since the mold clamping force is detected directly at the tie bar, which is the principle of the mold clamping force of the toggle mold clamping mechanism, the measurement accuracy is extremely high, and the mold clamping force can be set under any conditions. Because it can be handled, the operability and accuracy of the control are extremely good. Since the injection filling step is performed in parallel with the mold opening setting operation and the mold clamping operation up to the touch state of the mold is performed at a high speed, the molding cycle is shortened, and the productivity is remarkably improved.

[Brief description of the drawings]

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

FIG. 2 is a state explanatory view of an injection press molding method according to an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Link housing 2 Fixed board 3 Movable board 4 Mold 4a Movable mold 4b Fixed mold 5 Cavity 6 Toggle mechanism 7 Crosshead 8 Mold clamping cylinder 9 Piston rod 10 Guide rod 11 Tie bar 20 Mold clamping device 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 unit 62 Injection pressure setting unit 63 Injection control unit 64 Hydraulic control valve 65 Pressure sensor 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 73 Mold clamping control unit 74 Mold clamping cylinder stroke sensor 75 Mold opening detection unit 76 Mold opening setting means 77 Mold clamping force detection unit 78 Mold touch point Setting unit 100 Injection molding machine

Claims (3)

(57) [Claims] An injection molding apparatus for clamping a mold via a toggle mechanism is used to calculate the amount of shrinkage of the resin in the cooling and solidifying process in advance. The injection pressure is controlled by the injection pressure that can be filled in the mold, and the mold opening amount corresponding to the contraction amount is set in advance by the stroke of the mold clamping cylinder connected to the toggle mechanism during the mold clamping step. In the opening amount setting procedure, the movable platen is once advanced to retract the mold from the state in which both molds are touched to the mold opening amount. In the injection filling step, the resin is molded during the retreat operation of the movable platen. An injection press molding method, characterized in that the cavity is injected and filled, and after the injection and filling is completed, the movable plate is advanced to apply a mold clamping force. 2. A procedure for setting a mold opening amount includes detecting a state in which both molds are touched via a mold clamping force detecting unit incorporated in a tie bar, and determining a stroke of a mold clamping cylinder connected to a toggle mechanism as an origin. After the setting, the mold opening amount corresponding to the amount of resin solidification shrinkage is set by the stroke retreat amount of the mold clamping cylinder from the origin, and the operating oil pressure of the mold clamping cylinder is controlled so as to maintain the set retreat position. The injection press molding method according to claim 1, wherein 3. An injection control unit which includes an injection filling amount setting unit and an injection pressure setting unit, and performs injection filling based on the two setting units, and sets a mold opening amount corresponding to an amount of cooling, solidification, and contraction of the resin. Mold opening amount setting means, a mold opening amount detecting unit for detecting a mold opening amount of a mold, a mold clamping cylinder stroke sensor for detecting a stroke of a mold clamping cylinder, and a tie bar for detecting a mold touch point in the mold clamping process. A mold touch point setting unit which performs a clamping force detecting unit incorporated in the mold and sets the origin of a stroke of a clamping cylinder based on a detection signal of the clamping force detecting unit, and a set value of the mold opening amount setting means. A mold clamping control unit that performs mold clamping by controlling the stroke of the mold clamping cylinder connected to the toggle mechanism by comparing the detection signal of the mold opening amount detection unit and the detection signal of the mold clamping cylinder stroke sensor, The gold The mold touch point setting unit has a function of generating a mold opening amount setting start signal to the mold clamping control unit after completion of the origin setting and generating an injection start signal to the injection control unit, and generating an injection filling completion signal. An injection press molding apparatus, comprising: a filling completion detection unit; and a comparison control unit that generates a mold clamping start signal to the mold clamping control unit based on a detection signal from the injection filling completion detection unit.