JP2005297384A - Injection molding apparatus, injection condition setting method, and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for reducing the pressure in a cavity of a mold.
An injection molding apparatus 10 includes a plurality of injection nozzles 20, 21, 22, and 23 that inject a molten molding material into a cavity 24 in a mold 12, and molding that is injected from each injection nozzle to each injection nozzle. Control means for commanding the injection rate of the material. The control means includes a storage device that stores an injection rate corresponding to the elapsed time from the start of injection for each of the injection nozzles 20, 21, 22, and 23, and the injection rate stored in the storage device. Is set so as to equalize the injection pressure of each injection nozzle.

[Selection] Figure 1

Description

  The present invention relates to an injection molding apparatus, an injection condition setting method, and an injection molding method. More specifically, the present invention relates to a technique for adjusting the pressure in a cavity of a mold filled with a molding material injected by an injection nozzle of an injection molding apparatus.

  2. Description of the Related Art An injection molding apparatus that injects a molten molding material from an injection nozzle into a mold cavity is known.

There may be a portion of the mold cavity that is difficult to be filled with the molding material injected from the injection nozzle depending on its shape. Such a part is, for example, a deep part far from the injection nozzle or a narrow part. If there is a region where the molding material is difficult to be filled, the pressure of the molding material injected by the injection nozzle (hereinafter referred to as “injection pressure”) must be increased in order to spread the molding material there. When the injection pressure of the injection nozzle is increased, the pressure in the cavity is also increased. When the pressure in the cavity increases, the molding material enters the mating surfaces of the molding dies to generate burrs, or the mold clamping force of the molding dies must be increased.
The present invention has been made to solve such a problem, and an object of the present invention is to provide a technique for reducing the pressure in the cavity of the mold.

An injection molding apparatus according to the present invention comprises a plurality of injection nozzles for injecting a molten molding material into a cavity in a molding die, and a control means for commanding the injection rate of the molding material injected from each injection nozzle to each injection nozzle. I have. The control means includes a storage device that stores an injection rate corresponding to the elapsed time from the start of injection for each injection nozzle, and the injection rate stored in the storage device is the injection rate of each injection nozzle. The pressure is set to be equal.
According to this injection molding apparatus, the injection rate stored in the storage device of the control means is set to have a relationship that equalizes the injection pressure of each injection nozzle. For this reason, when the control unit injects the molding material from each injection nozzle at an injection rate that equalizes the injection pressure of each injection nozzle stored in the storage device, the pressure in the cavity is averaged and lowered as a whole.
Here, the injection rate means an injection amount per unit time, and is not limited to the injection rate itself, but includes data for realizing the injection rate. Moreover, that the injection pressure of each injection nozzle is equal means that the injection pressure difference of each injection nozzle is close enough to cause no substantial flow in the molding material in the cavity.

In the above injection molding apparatus, the injection rate stored in the storage device equalizes the injection pressure of each injection nozzle and uniformly increases the common injection pressure corresponding to the elapsed time from the start of injection. It is preferable that it is set to.
In this way, when the common injection pressure of each injection nozzle is set so as to increase uniformly corresponding to the elapsed time from the start of injection, injection of the molding material corresponding to the elapsed time injected into the cavity Since the rate does not fluctuate greatly, a high-quality molded product can be obtained. Here, uniformly increasing means that the injection rate increases without lowering the previous injection rate.

In the above injection molding apparatus, it is preferable that the injection rate stored in the storage device is a value obtained by executing a program for analyzing and calculating the flow of the molding material at the time of injection.
By using such a program, the injection rate of each injection nozzle can be obtained efficiently.

The injection condition setting method of the present invention includes a plurality of injection nozzles that inject a molten molding material into a cavity in a mold, and a storage device that stores an injection rate corresponding to an elapsed time from the start of injection for each injection nozzle And the injection rate is stored in the storage unit of the injection molding apparatus provided with control means for commanding the injection rate stored in the storage unit to each injection nozzle. When the injection rate is input, the method executes a program that calculates the flow rate and pressure of the molding material filled in the cavity using data describing the cavity shape, molding material flow conditions, and molding material solidification conditions. And a step of searching for an injection rate of each injection nozzle that equalizes the injection pressure of each injection nozzle, and a step of storing the searched injection rate of each injection nozzle in the storage device.
In the above injection condition setting method, when the injection rate is input, the flow rate and pressure of the molding material filled in the cavity are calculated using data describing the cavity shape, molding material flow conditions, and molding material solidification conditions. Is executed to search for the injection rate of each injection nozzle that equalizes the injection pressure of each injection nozzle. By using such a program, it is possible to efficiently search for the injection rate of each injection nozzle. Further, since the searched injection rate of each injection nozzle is stored in the storage device, the control unit instructs each injection nozzle to set the injection rate of each injection nozzle that equalizes the injection pressure of each injection nozzle. Therefore, the pressure in the cavity can be averaged and lowered as a whole.

In the injection molding method of the present invention, injection molding is performed by an injection molding apparatus including a plurality of injection nozzles for injecting a molten molding material into a cavity in a mold. Then, from the start of injection to the completion of filling, filling is performed with an injection amount per unit time of each injection nozzle that makes the injection pressure of each injection nozzle equal.
As described above, when filling with the injection amount per unit time of each injection nozzle that equalizes the injection pressure of each injection nozzle from the start of injection to the completion of filling, the pressure in the cavity can be averaged and lowered as a whole. .

The main features of the embodiments described later will be described.
(1) The injection molding apparatus 10 includes a molding die 12, a first injection nozzle 20, a second injection nozzle 21, a third injection nozzle 22, a fourth injection nozzle 23, a screw drive unit 30, and a controller 31. And a hopper 32.
The screw 34 accommodated in the injection nozzles 20, 21, 22, and 23 is driven by the screw driving unit 30. The controller 31 controls the screw driving unit 30. The hopper 32 stores a powdery molding material.
(2) When the screw 34 is rotated at a high speed while the screw 34 is retracted, the molding material is taken into the cylinder 33 from the hopper 32, melted and stored in the space on the tip side of the cylinder 33. When the screw 34 moves forward, molten molding material is injected into the cavity 24 from the injection nozzles 20, 21, 22, and 23.
(3) In determining the injection rate of the injection nozzles 20, 21, 22, and 23, flow analysis is performed by CAE. In this case, a model 36 obtained by modeling the mold 12 is used. The model 36 includes a mold 37, a runner 38, and one injection nozzle 39. The runner 38 branches to the branch runner 38c on the downstream side. In the CAE analysis, the pressure of the outlet portion 38b of the branch runner 38c is set to be equal, and the flow rate of the molding material flowing through each branch runner 38c at that time is calculated.
(4) The flow rate of the molding material flowing through each branch runner 38c thus calculated corresponds to the injection rate when the injection pressures of the injection nozzles 20, 21, 22, and 23 are equal. When the molding material is injected at this injection rate, the injection pressures of the injection nozzles 20, 21, 22, and 23 become equal, and the pressure in the cavity 24 can be lowered.

An injection molding apparatus 10 according to the present invention will be described with reference to the drawings.
As shown in FIG. 6, the injection molding apparatus 10 includes a molding die 12, a first injection nozzle 20 (shown in FIG. 1), a second injection nozzle 21, a third injection nozzle 22, and a fourth injection nozzle 23. It has. Further, the injection molding apparatus 10 includes a screw driving unit 30, a controller 31, and a hopper 32 shown in FIG. The molding die 12 is composed of a first die 14, a second die 16, and a core 18 (shown in FIG. 1). The core 18 is fixed to the second mold 16. When the first mold 14 and the second mold 16 are in close contact and the mold 12 is closed, the cavity 24 is formed by the first mold 14, the second mold 16 and the core 18. When the mold 12 is opened, the first mold 14 and the second mold 16 are separated.
As shown in FIG. 1, the first injection nozzle 20 is fixed to the outer surface of the first mold 14. The first mold 14 is formed with a first molding material flow path 25 that communicates the first injection nozzle 20 and the cavity 24. The second injection nozzle 21, the third injection nozzle 22 and the fourth injection nozzle 23 are fixed to the outer surface of the second mold 16. The second mold 16 includes a second molding material channel 26 that communicates the second injection nozzle 21 and the cavity 24, a third molding material channel 27 that communicates the third injection nozzle 22 and the cavity 24, and a fourth injection. A fourth molding material flow path 28 that communicates the nozzle 23 and the cavity 24 is formed.

As shown in FIG. 2, the injection nozzles 20, 21, 22, and 23 have a cylinder 33 and a screw 34. The tip 33 a of the cylinder 33 is narrowed, and the tip 33 a is connected to the molds 14 and 16. The hopper 32 communicates with the inside of the cylinder 33 on the rear end side of the cylinder 33 and stores a molding material. The molding material is in powder form. For example, polypropylene is used as the molding material. The screw 34 is accommodated in the cylinder 33. A spiral is formed on the outer periphery of the screw 34. The screw 34 is driven by the screw drive unit 30 to rotate about the axis and advance and retreat in the axial direction. The controller 31 controls the screw drive unit 30 to individually adjust the movements of the screws 34 of the injection nozzles 20, 21, 22, and 23. For this reason, the storage device built in the controller 31 stores information related to the operation of the screw 34 of the injection nozzles 20, 21, 22, and 23.
When injection molding is performed, the screw 34 is rotated at a high speed while the screw 34 is moved backward (the state shown in FIG. 2). When the screw 34 rotates at a high speed, the molding material stored in the hopper 32 is taken into the cylinder 33. The molding material taken into the cylinder 33 is fed to the tip side of the cylinder 33 while being kneaded by the screw 34 spiral. The kneaded molding material generates heat and melts. Therefore, the molten molding material is stored in the space on the tip side of the cylinder 33. Subsequently, the screw 34 advances rapidly. When the screw 34 moves forward, molten molding material is injected from the injection nozzles 20, 21, 22, and 23. The molding material injected from the injection nozzles 20, 21, 22, 23 is filled into the cavity 24 through the molding material channels 25, 26, 27, 28. After the molding material filled in the cavity 24 is cooled and individualized, the molding die 12 is opened and the molded product is taken out.

A portion of the cavity 24 sandwiched between the second mold 16 and the core 18 is narrow (hereinafter, this portion is referred to as a “narrow portion 35”). Since the narrow portion 35 is narrow, it is difficult to fill the molding material. If the molding material is injected into the cavity 24 from one injection nozzle, the injection pressure of the injection nozzle must be increased in order to distribute the molding material to the narrow portion 35. When the injection pressure of the injection nozzle is increased, the pressure in the cavity 24 is increased. When the pressure in the cavity 24 increases, the molding material enters the mating surfaces of the first mold 14 and the second mold 16 and burrs are generated. Further, when the molding material is injected from one injection nozzle, the molding material is filled while flowing largely in the cavity 24, so that sink marks and surface cracking defects may occur.
When a plurality of injection nozzles are used as in the injection molding apparatus 10 of the present embodiment, the injection pressure of each injection nozzle can be made lower than when only one injection nozzle is provided. The injection pressure can be lowered when a plurality of injection nozzles are used, unlike the case where a single injection nozzle spreads the molding material over the entire cavity 24 including the narrow portion 35, and each injection nozzle has a cavity 24. This is because the filling of the molding material into each part is shared. Therefore, the pressure in the cavity 24 is lowered, and the generation of burrs is prevented. In addition, when a plurality of injection nozzles are used, the degree to which the molding material flows in the cavity 24 becomes smaller than when a single injection nozzle is used. For this reason, it is possible to prevent the occurrence of sink marks and surface tension defects.

Thus, when a plurality of injection nozzles are used, the pressure in the cavity can be lowered. In this case, the pressure in the cavity can be further reduced by adjusting the injection rate of the molding material injected by each injection nozzle. Here, the injection rate means the injection amount of the molding material per unit time corresponding to the elapsed time from the start of injection.
On the other hand, if the injection nozzles 20, 21, 22, and 23 inject the molding material at the same injection rate without adjusting the injection rate, the pressure of the narrow portion 35 becomes higher than that of other parts. The reason why the pressure of the narrow portion 35 is higher than other portions is that the narrow portion 35 is difficult to be filled with the molding material (the molding material is difficult to enter). When the pressure of the narrow portion 35 increases, the pressure propagates to other parts than the narrow portion 35, and the pressure in the cavity 24 increases as a whole.

On the other hand, if the controller 31 controls the forward speed of the screw drive unit 30 and adjusts the injection rate of the molding material injected by the injection nozzles 20, 21, 22, and 23, the pressure in the cavity 24 is made lower. Can do. In this case, the injection rate is adjusted so that the pressure (injection pressure) of the molding material injected by the injection nozzles 20, 21, 22, and 23 becomes equal.
In determining the injection rate of the injection nozzles 20, 21, 22, and 23, CAE (Computer Aided Engineering) is used. CAE calculates the flow rate, pressure, and the like of the molding material filled in the cavity 24. FIG. 3 schematically illustrates a model 36 of the mold 12 to be analyzed using CAE. The model 36 includes a mold 37, a runner 38, and one injection nozzle 39. The molding die 37 is a three-dimensional shell mesh model, in which a cavity and a molding material channel are modeled. The injection nozzle 39 is connected to the inlet portion 38 a of the runner 38. The runner 38 is branched into five branch runners 38 c on the downstream side of the inlet portion 38 a, and the outlet portion 38 b that is the downstream end thereof is connected to the molding material flow path of the molding die 37. The length of each branch runner 38c is set equal by bending.

In the model 36 described above, flow analysis is performed using CAE under the condition that the pressure at the outlet portion 38b of each branch runner 38c is equalized, and the flow rate of the molding material flowing through each branch runner 38c is calculated. Since the lengths of the branch runners 38c are equal, their pressure loss characteristics are also equal. The difference in pressure loss characteristics due to the difference in the bent shape of each branch runner 38c is negligible. When the pressure loss characteristics of each branch runner 38c are equal, the flow rate of the molding material flowing through each branch runner 38c depends on the pressure of the outlet portion 38b. Accordingly, the flow rate of the molding material flowing through each branch runner 38c calculated as the molding material is injected from one injection nozzle 39 corresponds to the injection rate when the injection nozzle is arranged at each outlet portion 38b. Therefore, the injection rate of each injection nozzle when the injection pressure of each injection nozzle becomes equal can be obtained.
For the CAE analysis, for example, flow analysis software such as Moldflow Plastic Insight of MOLDFLOW is used.
In addition, the site | part set when a pressure becomes equal in order to calculate the injection rate of an injection nozzle is not necessarily restricted to the exit part 38b of the branch runner 38c. For example, it may be in the middle of the molding material flow path of the molding die 37, or in a portion in the cavity where the molding material flow path opens into the cavity.

FIG. 4 illustrates the injection pressures of the injection nozzles 20, 21, 22, and 23 with respect to the passage of time calculated by the CAE analysis. The injection pressures of the injection nozzles 20, 21, 22, and 23 are the same, and are indicated by a single line. Thus, when the injection pressures of the injection nozzles 20, 21, 22, and "23" are matched, the boundary conditions of the CAE are operated. Injection of the molding material from the injection nozzles 20, 21, 22, and 23 is completed at the time “P” when the pressure peaks, and thereafter, the molding material is surely filled into the cavity 24. In addition, a holding pressure is applied to the cavity 24.
FIG. 5 shows the injection nozzles 20, 21, 22, calculated when the CAE analysis is performed so that the injection pressures of the injection nozzles 20, 21, 22, 23 are equal as shown in FIG. The injection rate of 23 is shown. FIG. 5 shows the process until the injection of the injection nozzles 20, 21, 22, 23 is completed (until the time point “P” in FIG. 4). A line 40 in FIG. 5 indicates the injection rate of the first injection nozzle 20. A line 41 indicates the injection rate of the second injection nozzle 21 and the fourth injection nozzle 23. A line 42 indicates the injection rate of the third injection nozzle 22. Since the third injection nozzle 22 fills the narrow portion 35 with the molding material, as indicated by the line 42, the injection rate is calculated to be the smallest. In other words, since the injection rate of the third injection nozzle 22 is small, the injection pressure of the third injection nozzle 22 is low and equal to the injection pressure of the injection nozzles 20, 21, and 23.
Therefore, when the screw drive unit 30 is controlled by the controller 31 to adjust the forward speed of the screw 34 of the injection nozzles 20, 21, 22, and 23 so that the injection rate shown in FIG. The pressure can be lowered. When the pressure of the cavity 24 is low, the generation of burrs can be prevented and the clamping force of the molds 14 and 16 can be reduced. Further, if the injection pressures of the injection nozzles 20, 21, 22, and 23 are equal, the pressure distribution in the cavity 24 does not become unbalanced, so that the molding material is prevented from flowing in the cavity 24 after filling. When the flow of the molding material in the cavity 24 is prevented, the occurrence of sink marks and surface defects is prevented.

  As shown in FIG. 1, the first molding material flow path 25 of the first mold 14 and the molding material flow paths 26, 27, and 28 of the second mold 16 have different lengths. Therefore, in the above-described CAE analysis, it is preferable to consider the difference in pressure loss due to the different lengths of the molding material channels 25, 26, 27, and 28. Considering the difference in pressure loss between the molding material channels 25, 26, 27, and 28, the accuracy of CAE analysis can be further increased.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The II sectional view taken on the line of FIG. The schematic block diagram of an injection nozzle, a controller, etc. The schematic diagram of a CAE analysis model. The graph which shows the injection pressure of an injection nozzle. The graph which shows the injection rate of an injection nozzle. The typical perspective view of an injection molding device.

Explanation of symbols

10: Injection molding device 12: Mold 14: First mold 16: Second mold 18: Core 20: First injection nozzle 21: Second injection nozzle 22: Third injection nozzle 23: Fourth injection nozzle 24: Cavity 25: 1st molding material channel 26: 2nd molding material channel 27: 3rd molding material channel 28: 4th molding material channel 30: Screw drive part 31: Controller 32: Hopper 33: Cylinder, 33a: Tip Part 34: Screw 35: Narrow part 36: Model 37: Mold 38: Runner, 38a: Inlet part, 38b: Outlet part, 38c: Branch runner 39: Injection nozzle 40: Line (injection rate of the first injection nozzle)
41: line (injection rate of the second injection nozzle and the fourth injection nozzle)
42: Line (injection rate of the third injection nozzle)

Claims (5)

A plurality of injection nozzles for injecting a molten molding material into a cavity in a mold; and
Control means for commanding the injection rate of the molding material injected from each injection nozzle to each injection nozzle,
The control means includes a storage device that stores an injection rate corresponding to an elapsed time from the start of injection for each injection nozzle,
An injection molding apparatus characterized in that the injection rate stored in the storage device is set so as to make the injection pressure of each injection nozzle equal.   The injection rate stored in the storage device is set such that the injection pressures of the injection nozzles are made equal and the common injection pressure is uniformly increased corresponding to the elapsed time from the start of injection. The injection molding apparatus according to claim 1.   3. The injection molding apparatus according to claim 1, wherein the injection rate stored in the storage device is a value obtained by executing a program for analyzing and calculating a flow of a molding material at the time of injection. A plurality of injection nozzles that inject a molten molding material into a cavity in a mold, a storage device that stores an injection rate corresponding to an elapsed time from the start of injection for each injection nozzle, and a storage device that stores the injection rate It is a method of storing the injection rate in the storage device of the injection molding apparatus provided with a control means for commanding the injection rate to each injection nozzle,
When the injection rate is entered, a program that calculates the flow rate and pressure of the molding material that fills the cavity is executed using data describing the cavity shape, molding material flow conditions, and molding material solidification conditions. Searching for the injection rate of each injection nozzle to equalize the injection pressure of the nozzle;
Storing the searched injection rate of each injection nozzle in the storage device;
An injection condition setting method comprising: It is a method of injection molding with an injection molding apparatus having a plurality of injection nozzles for injecting a molten molding material into a cavity in a molding die,
An injection molding method characterized in that filling is performed with an injection amount per unit time of each injection nozzle that equalizes the injection pressure of each injection nozzle from the start of injection to the completion of filling.

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