JP3293415B2 - How to set the optimal filling resin amount for injection compression molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting an optimum filling resin amount for injection compression molding in which a molten resin is injected and filled in a mold, and then compression is performed on the mold clamping side.

[0002]

2. Description of the Related Art Heretofore, a method of setting a filling resin amount has been performed according to the following procedure. (1) In order to protect the mold and prevent an overload on the molding machine, molding is performed by sequentially increasing the measured value from the short shot measured value. (2) The approximate measurement value range is narrowed by visual inspection of the molded product. (In this case, the shot is not a short shot and is within a range in which burrs do not occur). (3) Measure the weight, thickness, etc. of the molded product and select a weighed value that falls within the quality response range.

[0003]

However, when the injection compression molding is performed by the conventional method of setting the optimum filling resin amount,
There were the following problems. Measuring the weight and thickness of a molded product is a manual operation by an operator, which is inefficient. When selecting the optimal weighing value by comparing the measurement result of the molded product with the allowable quality value, there are many factors that depend on the operator's experience and perception, and the judgment result is greatly affected by the skill of the operator, so that a stable high quality It is difficult to supply molded products.

In normal injection molding in which the holding pressure is maintained on the injection side, if the measured value is excessive, a large cushion stroke will remain, so that an appropriate measured value can be obtained using the cushion stroke as a criterion. . In contrast, in injection compression molding, in which compression is performed on the mold clamping side, the entire amount of the molten resin corresponding to the amount of cooling, solidification, and shrinkage of the resin is filled in the mold, and the mold on the mold clamping side in accordance with the cooling, solidification behavior of the resin. Since a compressive force will be applied, the weighing conditions directly affect the quality of the molded article. That is, even if the quality of the molded product is within the allowable range, in the case of the injection measurement under the excessively large weighing condition, the molded product has a large bottom thickness and a large residual strain, and conversely, the excessively small weighing condition. In this case, the thickness of the bottom surface of the molded product is reduced, and the transferability of the molded product is reduced. In any case, it causes deformation and warpage of the molded product, and it is not possible to obtain a molded product utilizing the characteristics of injection compression molding.

[0005] Therefore, there is a need for a method of setting the amount of the filled resin suitable for injection compression molding. The conventional setting method is a method used in a normal molding method in which a closed mold is filled with a molten resin and a pressure is maintained at an injection side. In the case of performing the filling molding, it is difficult to stably supply a high-quality molded product. Further, even if a mold is designed to reduce the thickness of a molded product, if excessive measurement value conditions are adopted at the molding site, the effect of reducing the resin material cost due to the intended reduction in thickness cannot be achieved.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to make it possible to perform an injection of an optimum filling resin amount with high precision without depending on the skill of an operator. It is an object of the present invention to provide a method for setting an optimum filling resin amount for compression molding.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for performing injection compression molding using an injection molding apparatus which drives a hydraulic mold clamping cylinder to perform mold clamping via a toggle mechanism. When setting the filling resin amount, the injection filling measurement value is sequentially increased from the short shot measurement value and molding is performed, and when the detection signal of the mold clamping force sensor incorporated in the tie bar changes at the completion of the compression process, The weighed value was adjusted to the optimum amount of the filled resin.

[0008]

[Function] The injection filling measurement value is sequentially increased from the short shot measurement value to perform molding, and when the compression process is completed, the measurement value when the detection signal of the mold clamping force sensor incorporated in the tie bar appears changes is optimally filled. By setting the amount of resin, the amount of resin to be filled can be set when the compression process closest to the product shape is completed. Filling resin amount that takes into account minute changes in the amount of filling resin (short shot filling resin that causes deformation and distortion, overpack filling resin that causes residual distortion) that affect the quality of molded products even within the quality tolerance range Can be set. Regardless of the skill level of the operator, accurate setting of the filling resin amount can be easily and quickly performed. As described above, it is possible to set a highly accurate optimal filling resin amount in a short time, and as a result, it is possible to increase productivity and stably supply a high-quality molded product.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for setting an optimum filling resin amount for injection compression molding according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual diagram of control of an injection molding machine according to the present invention, FIG. 2 is a flow chart showing a procedure for setting a filling resin amount, and FIG.
FIG. 3 is a diagram showing the relationship between the mold clamping force and the amount of the filled resin.

The injection molding apparatus 100 according to the present embodiment
Toggle type mold clamping device 20, injection device 40, and control unit 60
It is composed of

FIG. 1 shows an injection molding apparatus 100 provided with a toggle-type mold clamping device 20. The upper half of the center line shows a low-pressure mold clamping state before injection filling, and the lower half of the center line after completion of the compression step. In the high pressure mold clamping state. 1 includes a link housing 1, a fixed platen (fixed platen) 2, a movable platen (movable platen) 3, and a mold 4.
(Fixed mold 4b and movable mold 4a), cavity 5,
It comprises a toggle mechanism 6, a crosshead 7, a mold clamping cylinder (die lock cylinder) 8, a piston rod 9, and a guide rod 10.

In an injection molding apparatus 100 provided with a double toggle type mold clamping device 20, three toggle links 6a are provided between the movable platen 3 and the link housing 1, as shown in FIG.
A pair of upper and lower toggle mechanisms 6b and 6c are provided, and a mold clamping cylinder (die-lock cylinder) 8 is mounted substantially at the center of the outer end surface of the link housing 1, and the tip of the piston rod 9 of the mold clamping cylinder 8 is crossed. A guide rod 10 connected to the head 7 and having the crosshead 7
And the toggle mechanism 6 is operated via the crosshead 7 to move the movable platen (movable platen) 3 with respect to the fixed platen 2 to perform a mold clamping operation. . Reference numeral 11 denotes a tie bar.

Next, the injection device 40 will be described. In this embodiment, the injection device 40 includes a screw 4 in a barrel 41.
2 is provided, and the resin material in the hopper 43 is supplied to the supply zone,
It is configured to be heated and compressed in a compression zone, melt metered in a metering zone, and injected into a nozzle 44 via an injection zone.

A heater for externally heating the resin material is provided on the outer peripheral surface of the barrel 41, and the resin material is fed 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 unit 60 will be described. Mold clamping control section 61, mold clamping force sensor 62, injection control section 63, mold opening amount setting section 64, mold opening amount sensor 65, mold clamping force setting section 66, filling resin amount setting section 67, hydraulic control valves 68, 69. And hydraulic supply sources 70a and 70b.

The injection control unit 63 includes a hydraulic control valve 68 for controlling the operation of the injection cylinder 46 and a charged resin amount setting unit 67.
Connected to each other.

The mold clamping force sensor 62 incorporated at the end of the tie bar 11 is connected to a mold clamping force setting section 66. In addition, a mold opening sensor 65 for detecting the mold opening of both dies 4 a and 4 b is connected to the mold opening setting unit 64.

The mold clamping control section 61 is connected to a hydraulic control valve 69 for controlling the operation of the mold clamping cylinder 8, and the mold clamping control section 61 is connected to the mold clamping force setting section 66 and the mold opening amount setting section 64, respectively. It is connected.

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

The procedure for setting the amount of resin to be charged into the mold cavity 5 will be described with reference to FIG. Here, the injection compression molding in which compression is performed on the mold clamping side is roughly classified into two molding methods depending on the position of the mold 4 before injection filling of the molten resin.

That is, the closed molds 4a and 4b are filled with the molten resin, the mold opening behavior (in the case of the toggle mechanism 6, the tie bar 11 is extended) by the filled resin pressure, and then the mold clamping side. in compression molding, and sets the initial clamping force setting value P ₁ at mold clamping force setting unit 66 in the case of a so-called injection compression molding method, on the basis of the detection signal of the mold clamping force sensor 62 and the set value P ₁ The mold clamping controller 61 performs an initial mold clamping operation (step (A) in FIG. 2). However, the toggle mechanism 6 is held in a state before being fully extended.

In the case of a so-called injection press molding method in which molten resin is filled in the unclosed molds 4a and 4b and thereafter compression is performed on the mold clamping side, the mold opening amount set value S is set to the mold opening amount. The mold clamping control section 61 performs an initial mold clamping operation based on the detection signal of the mold opening amount sensor 65 and the set value S while being set by the setting section 64 (step (B) in FIG. 2). However, the toggle mechanism 6 is held in a state before being fully extended.

The mold clamping force (die height setting value P ₂ ) during the mold compression step (the toggle mechanism 6 is in a linear state) is set in advance (die height setting).

After completion of the initial mold clamping operation, the injection device 40 injects and fills the molten resin into the cavity 5. In this case, starting from the measured value of the short shot in order to protect the mold and prevent an overload on the molding machine. After the injection filling is completed or at any time during the filling, the toggle mechanism 6 is driven in the extending direction to perform the compression process, and the detection signal of the mold clamping force sensor 62 at the time of the completion of the compression is monitored.

If the monitor value is greater than or equal to the die height set value P _{2, the} weighing value is sequentially increased and repeated for each shot until so-called monitor value ≧ P ₂ .

This operation will be described in detail with reference to FIG. When molding is performed while the weighing value is sequentially increased, a point at which the detection signal of the mold clamping force sensor 62 at the time of completion of compression suddenly rises appears. The so-called detection signal ≧ P ₂ is the optimum filling resin amount (Z) of the measuring stroke value in the injection compression molding, and is stored in the filling resin amount setting section 67. That is, weighing stroke <
In the area of Z (the measured value of the short shot), when the compression is completed, the volume of the mold cavity is greater than the volume of the molded product due to the cooling and solidification shrinkage of the resin in the mold. (The mold and the resin have a minute gap). As a result, the detection signal of the mold clamping force sensor 62 does not change at all (detection signal = P ₂ ).

Conversely, in the area where the measuring stroke is greater than Z (the measured value of the overpack), when the compression is completed, the volume of the mold cavity is smaller than the volume of the molded product. As a result, the load concentrates on the tie bar 11 and the detection signal of the mold clamping force sensor 62 increases (detection signal> P ₂ ). The thickness of the molded product at the time of completion of compression increases, and as a result, the total mold thickness increases, which is the same as the change in the die height setting value, and the detection signal of the mold clamping force sensor 62 becomes Shows an increasing trend.

Here, ΔZ is the set value of the amount of the filled resin according to the conventional method, and thus the amount of the filled resin varies considerably depending on the skill of the operator. In injection compression molding, even if the quality of the molded product is within the allowable range, the amount of the filled resin varies very little due to the filling of the entire amount of the resin according to the cooling, solidification and shrinkage of the resin and the load of the compressive force on the mold clamping side. Directly affect (deformation due to short shot, warpage, or residual strain due to overpacking). As a result, it was not possible to stably supply a high-quality molded product.

On the other hand, in the setting method according to the present invention, the measured value at the time of reaching the inflection point H in FIG. 3 is defined as the optimum filling resin amount (Z) in the injection compression molding. There is no variation at all. Further, when setting the filling resin amount, it is only necessary to monitor the detection signal of the mold clamping sensor when the compression is completed, and the setting of the optimum filling resin amount (Z) is very easy since the mold clamping force sensor 62 changes. , And accurately.

In the present embodiment, the mold clamping force is used as the detection signal of the mold clamping force sensor. However, the extension of the tie bar 11, which is the principle of generating the mold clamping force of the toggle mechanism 6, may be used as the detection signal. .

[0033]

As is apparent from the above description, in the present invention, when performing injection compression molding using an injection molding apparatus that drives a hydraulic mold clamping cylinder to perform mold clamping via a toggle mechanism. When setting the filling resin amount, the injection filling measurement value is sequentially increased from the short shot measurement value, molding is performed, and measurement is performed when a change appears in the detection signal of the mold clamping force sensor incorporated in the tie bar when the compression process is completed. By setting the value to be the optimum filling resin amount, (1) it is possible to set the optimum filling resin amount with high precision in a short time and at the time of performing the injection compression molding without depending on the skill of the operator. Since it can be easily performed, productivity is greatly increased, and a high-quality molded product can be stably supplied. (2) By using the mold clamping force sensor used for mold clamping control in injection compression molding, operability can be improved by simplifying the control system so that cost reduction can be achieved by sharing the sensor.

[Brief description of the drawings]

FIG. 1 is a control conceptual diagram of an injection molding machine according to the present invention.

FIG. 2 is a flowchart showing a procedure for setting a filling resin amount according to the present invention.

FIG. 3 is a diagram showing a relationship between a mold clamping force and a filling resin amount according to 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 40 Injection device 41 Barrel 42 Screw 43 Hopper 44 Nozzle 46 Injection cylinder 47 Forward / reverse rotation motor 48 Injection piston 50 Toggle mold clamping device 60 Control unit 61 Mold clamping unit 62 Mold clamping force sensor 63 Injection control unit 64 Mold opening setting unit 65 Mold opening sensor 66 Mold clamping force Setting section 67 Filling resin amount setting section

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-227717 (JP, A) JP-A-1-221217 (JP, A) JP-A-4-161306 (JP, A) JP-A-6-227 31429 (JP, A) JP-A-7-68610 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claims] 1. An injection filling metering value is set to a short shot when setting a filling resin amount at the time of performing injection compression molding using an injection molding apparatus that drives a hydraulic mold clamping cylinder to perform mold clamping via a toggle mechanism. The molding is performed by sequentially increasing the measured value from the measured value, and the measured value when the detection signal of the mold clamping force sensor incorporated in the tie bar changes at the completion of the compression process is set as the optimum filling resin amount. Method for setting the optimal filling resin amount for injection compression molding.