JP4490222B2 - Gate balance setting method and injection molding apparatus - Google Patents

Description

  The present invention relates to a resin injection molding technique, and more particularly to a so-called multi-point gate injection molding technique.

  As a method for producing a resin molded product, injection molding is widely used in which a molten resin is filled in a cavity formed in a mold and foamed to produce a resin molded product. Methods for foaming the molten resin in the cavity include chemical foaming in which a foaming agent is mixed with the molten resin and supercritical gas foaming in which carbon dioxide or nitrogen gas in a supercritical state is dissolved in the molten resin and foamed. Proposed. Supercritical gas foaming is more suitable for fine foaming than chemical foaming, and is excellent in reducing weight, sinking, and warping of members that require strength. In addition, since the fluidity of the molten resin is improved and low-pressure molding is possible, it is possible to perform batch molding of a plurality of parts, thin parts, and downsizing of a molding machine. Furthermore, the cooling time by the endothermic absorption of the supercritical gas can shorten the time for cooling the molten resin, and the molding cycle can be shortened.

  Here, when injecting molten resin into a single cavity, a so-called multi-point gate type injection molding in which molten resin is injected from a plurality of injection gates has been proposed (for example, Patent Document 1). Compared to a single injection gate, multi-point gate injection molding can effectively flow the molten resin over the entire area of the cavity. It is used for the manufacture of resin molded products.

Japanese Patent Laid-Open No. 11-348078

  In the multi-point gate type injection molding, the balance of the injection amount of each injection gate, that is, the gate balance is important in ensuring the quality of the resin molded product. Therefore, when changing the injection molding conditions, for example, when changing the weight of the resin molded product, the foaming rate of the bubble cell, the injection speed from the injection gate, the thickness of the resin molded product, etc., the new injection molding conditions If the gate balance is not set again, there is a risk that defective products such as unfilled products of resin will occur. Conventionally, when resetting the gate balance, almost the same method as when setting a new gate balance was adopted, and the conditions of gate balance were determined by performing tests, etc. There is a problem that costs such as material costs are required.

  Therefore, an object of the present invention is to more easily reset the gate balance that can ensure the quality of the molded product.

According to the present invention, there is provided a gate balance setting method in injection molding in which a molten resin injected into a single cavity is distributed and injected from a plurality of injection gates, and the cavity is filled. At least when changing the filling amount of the molten resin, when changing the injection speed from the injection gate, and when changing the volume of the cavity to change the thickness of the resin molded product to be molded by the cavity in the case of one, the injection amount of each of the injection gate, the ratio between the total injection amount of all of the injection gate, the exit of each of the injection gate to be constant before and after the pre-Symbol change A gate balance setting method characterized by setting an amount is provided.

The present invention resets the gate balance by effectively utilizing the already optimized gate balance. That is, when changing the filling amount of the molten resin filled in the cavity, when changing the injection speed from the injection gate, the volume of the cavity is changed in order to change the thickness of the resin molded product formed by the cavity. By changing the gate balance so that the ratio between the injection amount of each injection gate and the total injection amount is constant before and after the injection molding condition change, such as when changing the Since the balance does not collapse before the change, it is possible to prevent the resin molded product from being thinned or the foaming degree from changing after the gate balance is reset. In addition, when resetting the gate balance, there is no need for a test for setting conditions. Therefore, the gate balance that can ensure the quality of the molded product can be reset more easily.

  In the present invention, the molten resin may be a molten resin in which an inert gas in a supercritical state is dissolved. In the case of supercritical gas foaming, finer foaming is possible and a wide range of foaming rate can be obtained, and the fluidity of the molten resin can be improved, which is easily affected by the balance of the amount of resin injected. In the present invention, the foaming state and the flow state are likely to change before and after the change of the injection molding conditions. In the present invention, the balance of the amount of resin injected before and after the change of the conditions is not lost. Particularly suitable for foaming.

  In the present invention, the molten resin may be a molten resin containing reinforcing fibers. When reinforcing fibers such as glass fiber and carbon fiber are included in the molten resin to be injected, the fiber orientation is easily affected by the balance of the amount of resin to be injected, and before and after changing the injection molding conditions, the fiber In the present invention, since the balance of the amount of resin injected before and after the change of the conditions is not lost, the present invention is particularly suitable for injection molding of a molten resin containing reinforcing fibers.

Further, according to the present invention, in an injection molding apparatus that distributes and injects molten resin injected into the cavity from a plurality of injection gates to a single cavity , the injection amount of each of the injection gates is adjusted. Adjustment means, and control means for controlling the adjustment means, the control means when changing the filling amount of the molten resin to be filled in the cavity, when changing the injection speed from the injection gate, And in at least one of the cases where the volume of the cavity is changed in order to change the thickness of the resin molded product molded by the cavity, the injection amount of each of the injection gates and all the injection gates the ratio between the total injection amount of the injection molding apparatus is provided, wherein the controller controls the adjustment means to be constant before and after the pre-Symbol changes.

The present invention resets the gate balance by effectively utilizing the already optimized gate balance. That is, when changing the filling amount of the molten resin filled in the cavity, when changing the injection speed from the injection gate, the volume of the cavity is changed in order to change the thickness of the resin molded product formed by the cavity. By changing the gate balance so that the ratio between the injection amount of each injection gate and the total injection amount is constant before and after the injection molding condition change, such as when changing the Since the balance does not collapse before the change, it is possible to prevent the resin molded product from being thinned or the foaming degree from changing after the gate balance is reset. In addition, when resetting the gate balance, there is no need for a test for setting conditions. Therefore, the gate balance that can ensure the quality of the molded product can be reset more easily.

  As described above, according to the present invention, the gate balance that can ensure the quality of the molded product can be reset more easily.

<Device configuration>
FIG. 1A is a system diagram of a resin molded product manufacturing apparatus A according to an embodiment of the present invention. The manufacturing apparatus A is an injection molding apparatus that employs supercritical gas foaming, but the present invention is also applicable to an injection molding apparatus that employs chemical foaming. The manufacturing apparatus A includes an injection apparatus 100, a mold clamping apparatus 200, and a supercritical gas generation apparatus 300. The injection device 100 includes a hopper 101 into which a resin material that is a raw material of a resin molded product is charged, a screw cylinder 102 that performs transfer, compression, kneading, melting, measurement, and the like of the resin material charged into the hopper 101, and a screw cylinder 102 And a nozzle 103 for injecting the molten resin in the screw cylinder 102 into the mold in the mold clamping device 200. Such a configuration of the injection device 100 may be the same as that of a known injection device.

  The supercritical gas generator 300 is a device that changes a gas such as carbon dioxide gas or nitrogen gas filled in the cylinder 301 to an inert gas in a supercritical state. The supercritical gas generated by the supercritical gas generator 300 is introduced into the screw cylinder 102 via the injection device 302 and is dissolved in the molten resin in the screw cylinder 102. The molten resin in which the supercritical gas is melted is injected into a mold described later in the mold clamping device 200.

  Next, the structure around the mold housed in the mold clamping device 200 will be described. FIG. 1B is a schematic diagram of the configuration around the mold of the manufacturing apparatus A. The mold clamping device 200 includes a fixed mold 10 and a movable mold 11. The movable mold 11 is configured to be movable as a whole by an actuator (not shown), and the mold 10 is clamped or divided.

  A cavity 12 is formed in the molds 10 and 11. The mold 10 is provided with a plurality (two in the example in the figure) injection gates G1 and G2 for injecting the molten resin injected from the nozzle 103 into the cavity 12 and filling it. That is, the manufacturing apparatus A is a multi-point gate type injection molding apparatus that injects molten resin from a plurality of injection gates G 1 and G 2 into a single cavity 12. In the present embodiment, it is assumed that a plate-like member partially different in thickness as a resin molded product by the manufacturing apparatus A (in the example in the figure, the upper part is thick and the lower part is thin) is formed. Forms a three-dimensional filling space corresponding to this.

  Next, a flow control valve 13 having a plurality of valve mechanisms for distributing the molten resin injected from the nozzle 103 to the injection gates G1 and G2 and controlling the respective flow rates is provided in the mold 10. That is, the flow rate control valve 13 functions as an adjusting unit that adjusts the injection amount of the injection gates G1 and G2 with respect to the cavity 12. In this embodiment, the flow control valve 13 is an electromagnetic control valve, electronically controlled by the control device 14, and the injection amount of each injection gate G <b> 1 and G <b> 2 is adjusted by a command from the control device 14.

  The control device 14 includes a CPU 141 that controls the entire control device 14. The CPU 141 functions as a control unit that controls the flow rate control valve 13, and executes a gate balance setting change process described later. The ROM 142 is a memory for storing fixed data and programs. The RAM 143 functions as a work area for the CPU 141 and is a memory that stores variable data and the like. The HDD (hard disk drive) 144 is a storage device that stores a gate balance setting change processing program and gate balance ratio data, which will be described later. These ROM 142, RAM 143, and HDD 144 may use other storage means.

  An I / F (interface) 145 is an interface between the flow rate control valve 13 and the CPU 141, and the CPU 141 controls the flow rate control valve 13 through the I / F 145 to control the opening degree of the valves corresponding to the gates G 1 and G 2. Output instructions. The input device 147 is an input device such as a keyboard and a mouse for an operator to input various data. An I / F (interface) 146 is an interface between the input device 147 and the CPU 141, and data input from the input device 147 is acquired by the CPU 141 via the I / F 146. The display 149 is a display device that displays various types of information, and the display controller 148 performs display control of the display 149 in accordance with instructions from the CPU 141.

  Next, processing at the time of resetting the gate balance in the manufacturing apparatus A will be described. The gate balance is reset when changing the injection molding conditions. Examples of changing the injection molding conditions include, for example, changing the weight of the resin molded product (foaming rate of the bubble cell), the injection speed from the injection gate, the thickness of the resin molded product, and the like.

  The case where the weight of the resin molded product is changed is the case where the amount of molten resin filled in the cavity 12 is changed, and the case where the resin molded product is further solidified (when the foaming rate of the bubble cell is lowered). The filling amount is increased (the weight of the resin molded product is increased). Conversely, when the resin molded product is made into a foam (when increasing the foaming rate of the cell), the filling amount is reduced (the weight of the resin molded product is reduced). In such a case, if the injection time of the molten resin is not changed, it is necessary to change the injection amount of the molten resin injected from the gates G1 and G2, and the gate balance needs to be reset.

  When changing the injection speed from the injection gate, it partially overlaps with changing the weight of the resin molded product, but when changing the injection time without changing the filling amount of the molten resin in the cavity 12, This is a case of changing the filling amount of the molten resin without changing the injection time, or a case of changing both the injection time and the filling amount of the molten resin. Even in such a case, it is necessary to change the injection amount of the molten resin injected from the gates G1 and G2, and it is necessary to reset the gate balance.

  The case where the thickness of the resin molded product is changed is, for example, a case where the thickness of the resin molded product is changed by increasing the volume of the cavity 12 by the thickness d as shown in FIG. In this case, since the volume of the cavity 12 increases, it is necessary to increase the filling amount of the molten resin, and it becomes necessary to change the injection amount of the molten resin injected from the gates G1 and G2, and the gate balance needs to be reset. Become.

  In this embodiment, when resetting the gate balance, the ratio between the injection amount of each injection gate and the total injection amount of all the injection gates (hereinafter, the value is referred to as ratio data) is the injection molding condition. The injection amount of each injection gate is set to be constant before and after the change. That is, the gate balance is reset by effectively utilizing the gate balance that has already been optimized and before changing the injection molding conditions.

Specifically, in the case of the example of FIG. 1B, the injection amount of each of the injection gates G1 and G2 (assuming that the injection amount is constant during the injection time, here it is the injection amount per unit time. The same applies hereinafter). Is V1 and V2, the total injection amount V0 of all injection gates G1 and G2 is V1 + V2. Therefore, the ratio data K1 of the injection gate G1 is
K1 = V1 / (V1 + V2),
The ratio data K2 of the injection gate G2 is
K2 = V2 / (V1 + V2)
It can be.

Then, when changing the injection molding conditions to set the total injection amount V0 to V0 ′, the injection amounts V1 ′ and V2 ′ of the injection gates G1 and G2 are respectively
V1 ′ = K1 × V0 ′,
V2 ′ = K2 × V0 ′
The gate balance can be reset as

For example, when the injection molding condition is changed so that the injection amount V1 of the injection gate G1 is set to V1 ′, the injection amount V2 ′ of the injection gate G2 is
V2 ′ = K2 / K1 × V1 ′
The gate balance can be reset as

  FIG. 2 is a flowchart of the gate balance setting change process executed by the CPU 141, which is a process at the time of resetting the gate balance. In S <b> 1, the operator inputs conditions to be changed from the input device 147. That is, in accordance with the change of the injection molding conditions, the operator inputs the value V0 'after the change of the total injection amount V0 or the value V1' or V2 'after the change of the injection amount V1 or V2.

  In S2, ratio data (K1, K2) is read. The ratio data is stored in the HDD 144. In S3, the injection amount (at least one of V1 ′ and V2 ′) of each injection gate (G1, G2) based on the condition input in S1 and the ratio data (K1, K2) read out in S2. Is calculated. In S4, the injection amount (V1 ', V2') of each injection gate (G1, G2) calculated in S3 is set as a new injection amount. In S5, the flow control valve 13 is controlled based on the new injection amount set in S4, and the opening degree of the valve corresponding to each injection gate G1, G2 is adjusted. Thus, the gate balance is reset.

  Thus, in this embodiment, before and after the change of the injection molding conditions, injection is performed by resetting the gate balance so that the ratio of the injection amount of each injection gate to the total injection amount becomes constant. The balance of the resin amount is not lost before the change, and it is possible to prevent the resin molded product from being thin or changing the degree of foaming after resetting the gate balance. In addition, when resetting the gate balance, there is no need for a test for setting conditions. Therefore, the gate balance that can ensure the quality of the molded product can be reset more easily.

  Further, in this embodiment, it is assumed that a molten resin in which supercritical gas is dissolved is injected, but when adopting the resetting of the gate balance of this embodiment, such supercritical gas foaming is adopted. It is particularly effective for injection molding. In the case of supercritical gas foaming, finer foaming is possible and a wide range of foaming rate can be obtained, and the fluidity of the molten resin can be improved, which is easily affected by the balance of the amount of resin injected. In the present embodiment, the balance of the amount of resin injected before and after the change of the injection molding condition is not lost because the foaming state and the flow state are likely to change before and after the change of the injection molding condition. is there.

  Moreover, when the resetting of the gate balance of this embodiment is adopted, it is also effective for injection molding of a molten resin containing reinforcing fibers. When reinforcing fibers such as glass fiber and carbon fiber are included in the molten resin to be injected, the fiber orientation is easily affected by the balance of the amount of resin to be injected, and before and after changing the injection molding conditions, the fiber This is because the disorder of orientation and variations are likely to occur, and in this embodiment, the balance of the amount of resin injected before and after the change of the injection molding conditions is not lost.

<Other embodiments>
In the above embodiment, the flow rate control valve 13 is used to adjust the injection amount of each of the injection gates G1 and G2. However, the present invention is not limited to this, and other means may be used as long as the injection amount can be adjusted. Further, the injection amount of each injection gate G1 and G2 may be adjusted by changing the mold 10 and changing the cross-sectional area of the injection gate.

In the above-described embodiment, an example in which two injection gates are used is illustrated, but three or more injection gates can also be applied. FIG. 3B is a diagram showing a case where three injection gates (G1, G2, G3) are provided. In this case, the ratio data K1 to K3 of each of the injection gates G1 to G3 are as follows. The injection amounts of the injection gates G1 to G3 are V1 to V3, respectively.
K1 = V1 / (V1 + V2 + V3),
K2 = V2 / (V1 + V2 + V3),
K3 = V3 / (V1 + V2 + V3)
It becomes. The same applies when four or more injection gates are provided, and the ratio data corresponding to each injection gate may be the numerator as the injection amount of the injection gate and the denominator as the total injection amount of all the injection gates.

FIG. 2A is a system diagram of a resin molded product manufacturing apparatus A according to an embodiment of the present invention, and FIG. It is a flowchart which shows a gate balance setting process. (A) is a figure which shows the example which increases the volume of the cavity 12 only by thickness d, and changes the thickness of a resin molded product, (b) is a figure which shows the example which provided three injection gates.

Explanation of symbols

A Resin molded product manufacturing apparatus G Injection gate 10, 11 Mold 12 Cavity 13, 13 'Flow control valve (adjusting means)
14 control device 141 CPU (control means)

Claims (4)

A method for setting a gate balance in injection molding in which a molten resin injected into the cavity is distributed and injected from a plurality of injection gates with respect to a single cavity,
The volume of the cavity in order to change the filling amount of the molten resin to be filled in the cavity, to change the injection speed from the injection gate, and to change the thickness of the resin molded product to be molded by the cavity in the case of at least one of when to change, respectively so that the injection amount of each of the injection gate, the ratio between the total injection amount of all of the injection gate, becomes constant before and after the pre-Symbol change A gate balance setting method comprising: setting an injection amount of the injection gate.   The gate balance setting method according to claim 1, wherein the molten resin is a molten resin in which an inert gas in a supercritical state is dissolved.   The gate balance setting method according to claim 1, wherein the molten resin is a molten resin containing reinforcing fibers. In an injection molding apparatus that dispenses and injects molten resin injected into the cavity from a plurality of injection gates with respect to a single cavity,
Adjusting means for adjusting the injection amount of each of the injection gates;
Control means for controlling the adjusting means;
With
The control means includes
The volume of the cavity in order to change the filling amount of the molten resin to be filled in the cavity, to change the injection speed from the injection gate, and to change the thickness of the resin molded product to be molded by the cavity in the case of at least one of when to change the injection quantity of each of the injection gate, the ratio between the total injection amount of all of the injection gate, said to be constant before and after the pre-Symbol change An injection molding apparatus characterized by controlling the adjusting means.

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