JP5636800B2 - Injection molding method and injection molding apparatus - Google Patents

Description

  The present invention relates to an injection molding method and an injection molding apparatus for filling a mold cavity having a plurality of valve gates with a molten resin.

  For example, in a large resin product such as a bumper of an automobile, the product is thinned from the viewpoint of weight reduction and cost reduction. In this case, when the cavity is narrowed, the flow resistance of the molten resin flowing in the cavity is increased, and there is a tendency that product molding defects are likely to occur. As a countermeasure against this, a method is known in which a plurality of valve gates are arranged for one cavity, and injection control of molten resin is performed by controlling a gate pin provided in each valve gate.

Several methods for controlling injection of molten resin by controlling the gate pin are known.
The first method is a method of controlling the opening and closing of the valve gate and controlling the injection of the molten resin by moving the gate pin to the fully open position or the fully closed position based on the position information of the injection screw ( Patent Document 1).

  The second method includes a pressure sensor that detects the pressure value of the molten resin in the valve gate, and controls the opening degree of the valve gate by moving the gate pin so that the pressure in the valve gate approaches the target value. (See Patent Document 2).

Special Table 2000-515450 Special table 2003-522654 gazette

By the way, both the first and second methods have the following problems.
In the first method, the opening and closing of the valve gate is controlled to be fully opened or fully closed, and the opening degree of the valve gate cannot be adjusted. Therefore, the discharge amount of the molten resin discharged from the valve gate into the cavity is either zero or maximum by opening and closing the valve gate.
Here, in a mold provided with a plurality of valve gates, the molten resin is distributed to each valve gate by branching one flow path into a plurality of paths. Therefore, if the flow rate of the molten resin distributed to each valve gate changes as described above due to the opening and closing of the related valve gate, the discharge amount of the molten resin discharged from each valve gate is affected. Interaction between gates occurs.

Therefore, in the first method, each valve gate discharges into the cavity due to the influence of the opening / closing control for fully opening or closing the valve gate and the interaction between the gates generated by opening / closing the related valve gate. A large change occurs in the discharge amount of the molten resin.
As a result, non-uniform pressure, poor flow of the molten resin, and the like occur in the cavity, and defects in shape and appearance such as surface distortion, burrs, and flow marks of the molded product occur.

In the second method, the change in the discharge amount of the molten resin discharged into the cavity is greatly improved by controlling the pressure in the valve gate as compared with the first method. However, it cannot be said that the control accuracy is high and the influence of the inter-gate interaction cannot be eliminated. Therefore, when high molding quality is required, a molding defect similar to the first method occurs. There is a case.
In the second method, since the pressure sensor needs to be provided in the valve gate, the structure of the mold becomes complicated, and the pressure sensor is required to have heat resistance and durability. For this reason, the cost for the mold and the pressure sensor becomes high, and the maintainability also deteriorates.
Therefore, there is a strong demand for an injection molding method and an injection molding apparatus that can stabilize the discharge amount and pressure of the molten resin discharged into the cavity and prevent the occurrence of molding defects without causing these problems. .

  The present invention has been made in view of such problems, and by optimizing the discharge amount and pressure of the molten resin discharged into the cavity, the occurrence of molding defects can be prevented and high-quality molded products can be stabilized. It is an object of the present invention to provide an injection molding method and an injection molding apparatus that can be produced in this manner.

The first invention is an injection molding method in which a molten resin injected from an injection screw is branched into a plurality of paths and injected into one or a plurality of cavities via a plurality of valve gates.
In the valve gate, a gate pin that adjusts the opening degree of the valve gate by moving forward and backward is provided, and the discharge amount of the molten resin discharged from the valve gate is controlled by the forward and backward position of the gate pin,
The inflow amount of the molten resin injected from the injection screw and flowing into the valve gate is grasped by the advance position of the injection screw, and the advance position of the injection screw when injecting the molten resin by the advance movement of the injection screw is determined. Detect as screw position information,
Considering gate interaction between the molten resin from the valve gate to flow respectively into said cavity, relative to the forward position of the injection screw, the condition map respective predetermined optimal forward and backward positions in the respective gate pin Using, the target advance / retreat position which is the optimum advance / retreat position of each gate pin with respect to the screw position information is obtained,
In the injection molding method, the position of the advance / retreat position of each gate pin is controlled so as to always approach the target advance / retreat position.

The second invention is an injection molding apparatus in which a molten resin injected from an injection screw is branched into a plurality of paths, and injected into one or a plurality of cavities via a valve gate provided for each path.
The injection molding apparatus includes a gate pin that adjusts an opening degree of the valve gate by moving back and forth in the valve gate;
A gate pin drive unit for controlling the forward / backward position of the gate pin;
A screw position sensor that detects a forward position of the injection screw when the molten resin is injected by forward movement of the injection screw, and outputs it as screw position information;
Considering gate interaction between the molten resin from the valve gate to flow respectively into said cavity, relative to the forward position of the injection screw, the condition map respective predetermined optimal forward and backward positions in the respective gate pin And a controller that outputs a target advance / retreat position that is an optimum advance / retreat position of each gate pin with respect to the screw position information using the condition map,
The amount of molten resin discharged from the valve gate is controlled by the advance / retreat position of the gate pin, and the amount of molten resin injected from the injection screw and flowing into the valve gate is determined by the advance position of the injection screw. ,
In the injection molding apparatus, the gate pin driving unit is configured to control the position of the advance / retreat position of each gate pin so as to always approach the target advance / retreat position.

Next, the function and effect of the first and second inventions will be described.
In the injection molding method according to the first aspect of the invention, the target advance / retreat position of each gate pin with respect to the screw position information is obtained using a condition map that defines the optimum advance / retreat position of each gate pin with respect to the advance position of the injection screw. The position of the gate pin is controlled so as to approach the target advance / retreat position.

  The total amount of molten resin injected by the injection screw and supplied to each valve gate is determined by the forward movement amount of the injection screw. Here, in the case of having the plurality of valve gates, it is possible to control the discharge amount to the optimum by adjusting the opening of each valve gate according to the integrated amount of the molten resin injected by the injection screw. It leads to quality improvement.

  In the injection molding method of the present invention, the optimum advance / retreat position of each gate pin is determined with respect to the advance position of the injection screw. That is, the total amount of molten resin injected by the injection screw and supplied to each valve gate is grasped by replacing the advance position of the injection screw, and the molten resin discharged from the valve gate to the cavity is grasped. The discharge amount is controlled by replacing it with the forward / backward position of the gate pin that directly relates to the opening degree of the valve gate. By adopting position control in this way, control accuracy can be significantly improved compared to direct pressure and flow control, and the amount of molten resin discharged from the valve gate into the cavity can be easily optimized. Can be.

  In the injection molding method of the present invention, the advance / retreat position of each gate pin is predetermined in the condition map with respect to the advance position of the injection screw. Therefore, when creating the condition map, it is possible to anticipate the influence of the inter-gate interaction and to determine the optimum forward / backward position of the gate pin so as to eliminate the influence. Thereby, in the said injection molding method using the said condition map which defined the optimal advance / retreat position of the said gate pin, the influence of the said interaction between gates can be reduced.

  The injection molding apparatus of the second invention includes at least the gate pin, the gate pin driving unit, the screw position sensor, and the controller storing the condition map. Thereby, said outstanding injection molding method can be implemented reliably.

  According to the first and second inventions described above, by optimizing the discharge amount and pressure of the molten resin discharged from each valve gate into the cavity, it is possible to prevent the occurrence of molding defects and to produce a high-quality molded product. An injection molding method and an injection molding apparatus that can be stably produced can be provided.

The front view which showed the structure of the injection molding apparatus in Example 1 in the partial cross section. Sectional drawing of the metal mold | die unit in Example 1. FIG. 2 is a longitudinal sectional view of a valve gate in Embodiment 1. FIG. FIG. 3 is an enlarged cross-sectional view of a main part of the gate pin in the first embodiment. FIG. 3 is a cross-sectional view of a gate pin driving unit in the first embodiment. The diagram which shows the position of each gate pin defined with respect to the advance / retreat position of the injection screw described in the condition map in Example 1. FIG.

  In the first and second inventions, the distal end side of the valve gate and the gate pin refers to the discharge port side disposed in the valve gate, and the opposite side is referred to as the proximal end side of the valve gate and the gate pin. The tip side of the screw refers to the cavity side, and the opposite side is referred to as the base end side of the screw.

In the first invention, it is preferable that the advance / retreat position of each gate pin is detected as pin position information, and the position control is performed by feedback control using the pin position information and the target advance / retreat position. 2).
In this case, the pin position information is compared with the target advance / retreat position, and control for correcting the advance / retreat position of the gate pin to the target advance / retreat position is continuously performed. Therefore, the advance / retreat position of the gate pin can be brought closer to the target advance / retreat position more accurately.

In a second aspect of the invention, the injection molding apparatus further includes a pin position sensor that detects an advance / retreat position of each gate pin and outputs the position as pin position information, and the position control is performed using the pin position information and the target advance / retreat. It is preferable to perform the feedback control using the position (Claim 4).
In this case, in addition to the structure of 2nd invention, the said pin position sensor is provided. Thereby, the said injection molding method using the said feedback control can be implemented reliably.

In the second invention, when the discharge port side of the valve gate is the front end side and the opposite side is the base end side, the pin position sensor is a branch runner that forms a flow path for supplying molten resin to the valve gate. It is arrange | positioned in the position of a base end side rather than arrangement | positioning position.
Therefore, the pin position sensor can be disposed at a position exposed to the outside of the mold having the cavity. Therefore, the mold structure is not complicated compared to the case where the pin position sensor is disposed inside the mold.

  Further, since the pin position sensor does not come into contact with the molten resin, it is not necessary to consider heat resistance and durability. Therefore, the cost for the mold and the pin position sensor can be reduced. The pin position sensor can be exposed to the outside of the mold. Therefore, assembly and maintenance can be performed without disassembling the mold, and maintainability can be improved.

  Further, in the case of a large and thin molded product such as the automobile bumper of the present example, the conventional injection molding method causes surface distortion of the design surface or cracking of the fixed mold 40 and the movable mold 41. There is a tendency that defects such as burrs are likely to occur in the part. In other words, this is because the control accuracy of the discharge amount and pressure of the molten resin discharged from the valve gate into the cavity is low, and the average internal pressure in the cavity is not uniform.

Below, the Example which shape | molded the bumper for motor vehicles by the injection molding apparatus and injection molding method of this invention is described using FIGS.
Example 1
As shown in FIGS. 1 to 3, the injection molding apparatus 1 of this example branches the molten resin injected from the injection screw 21 into a plurality of paths, and 1 through the valve gates 32 and 33 provided for each path. The two cavities 31 are configured to be injection filled.

As shown in FIG. 2, the injection molding apparatus 1 includes gate pins 34 and 35 that adjust the opening degree of the valve gates 32 and 33 by advancing and retracting the valve gates 32 and 33, and the forward and backward positions of the gate pins 34 and 35. And a gate pin driving unit 38 for controlling the above. As shown in FIG. 1, the injection molding machine 1 detects a forward position of the injection screw 21 when the molten resin is injected by forward movement of the injection screw 21 and outputs a screw position sensor 22 as screw position information. The condition map 6 in which the optimum advance / retreat positions of the gate pins 34, 35 are predetermined with respect to the advance position of the injection screw 21 is stored, and the optimum advance / retreat position of the gate pins 34, 35 with respect to the screw position information is stored using the condition map 6. And a controller 5 for outputting a target advance / retreat position.
The gate pin drive unit 38 is configured to control the position of the advance / retreat positions of the gate pins 34, 35 so as to always approach the target advance / retreat position.

The details will be described below.
As shown in FIG. 1, the injection molding apparatus 1 has an injection unit 2 for injecting a molten resin, a mold unit 3 for filling the molten resin, input of conditions relating to molding, and control of the injection unit 2 and the mold unit 3. And a controller 5 for performing.

As shown in FIG. 1, the injection unit 2 includes a hopper 23 into which a pellet-shaped resin material is charged, and a cylinder 24 coupled to the hopper 23. The cylinder 24 is provided with a nozzle 26 that discharges molten resin to the mold unit 3. A screw position sensor 22 that detects the forward position of the injection screw 21 and a band heater 27 that heats the cylinder 24 are provided outside the cylinder 24.
The cylinder 24 is provided with an injection screw 21 for injecting molten resin by a forward movement, and a screw drive section 25 for rotating the injection screw 21 and moving forward and backward is provided at the base end of the injection screw 21. It is arranged.

As shown in FIG. 2, the mold unit 3 includes a fixed mold 40 and a movable mold 41. A cavity 31 formed by contacting both of the fixed mold 40 and the movable mold 41 is provided on the facing surface of the fixed mold 40 and the movable mold 41.
In this example, one cavity is provided in one mold, but a plurality of cavities can be provided in the mold, and a plurality of molded products can be obtained by one molding. In addition, the plurality of cavities may have different shapes.

  The fixed mold 40 is provided with a main runner 42 into which the molten resin injected from the injection unit 2 flows, and two branch runners 43 and 44 that connect between the main runner 42 and the cavity 31. Yes. The branch runners 43 and 44 are provided with valve gates 32 and 33, respectively, and gate pins 34 and 35 are provided inside the valve gates 32 and 33.

As shown in FIG. 3, a gate pin drive unit 38 made up of a hydraulic actuator is provided at the base end of the gate pins 34 and 35. A hydraulic pressure unit (not shown) and a servo valve unit (not shown) for driving and controlling the gate pin drive unit 38 are connected. A piston 381 is provided inside the gate pin driving unit 38, and a distal end portion of the piston 381 and a proximal end portion of the gate pins 34 and 35 are coupled to each other.
In this example, a hydraulic actuator is used for the gate pin drive unit, but a pneumatic actuator, an electric actuator, or the like can also be used.

In addition, a pin position sensor 36 for detecting the advancing / retreating positions of the gate pins 34 and 35 is disposed at the base end portion of the gate pin driving unit 38. The pin position sensor 36 is a non-contact sensor using an eddy current, and detects the position information of the gate pins 34 and 35 with a column 382 disposed on the base end side of the piston 381 as a detection target.
In this example, a non-contact sensor using an eddy current is used as the pin position sensor, but it can be changed to one having a position detection function such as various position sensors and an image recognition device.

  As shown in FIGS. 3 and 4, stepped portions 341 and 351 are provided at positions on the base end side of the gate pins 34 and 35, and pin tapered portions 342 and 352 are formed. On the other hand, gate taper portions 321 and 331 parallel to the pin taper portions 342 and 352 are provided on the inner side surfaces of the valve gates 32 and 33. The amount of molten resin discharged from the valve gates 32 and 33 is controlled by moving the gate pins 34 and 35 forward and backward and adjusting the distance between the pin taper portions 342 and 352 and the gate taper portions 321 and 331.

The controller 5 has a touch panel for inputting conditions related to molding, and a computer for controlling the injection unit 2 and the mold unit 3. Based on the condition map 6 input using the touch panel, the computer calculates the target advance / retreat position and controls the injection unit 2 and the mold unit 3.
Although a touch panel is used in this example, it can be changed to one having an input function such as a keyboard.

Next, an injection molding method using the injection molding machine 1 will be described.
The resin material introduced into the hopper 23 is supplied to the cylinder 24 by the rotating injection screw 21. And it heats with the frictional heat which generate | occur | produces with the shear force at the time of the injection screw 21 rotating, and the heat | fever which the band heater 27 arrange | positioned on the outer periphery of the cylinder 24 turns into molten resin.

  When a certain amount of molten resin is stored at the tip of the injection screw 21, the injection screw 21 starts moving forward, and the molten resin stored at the tip is injected into the mold unit 3. At this time, the screw position sensor 22 detects the forward position of the injection screw 21 as screw position information and outputs the detected position to the controller 5.

  The molten resin injected from the injection unit 2 flows from the main runner 42 provided in the mold unit 3 through the branch runners 43 and 44 to the valve gates 32 and 33. The gate pins 34, 35 provided inside the valve gates 32, 33 are moved according to the condition map 6 to adjust the opening of the valve gates 32, 33 by moving the advance and retreat positions, and melted to be discharged into the cavity 31. The amount of resin discharged is controlled. In this example, as indicated by a broken line in FIG. 4, when the valve gates 32 and 33 are fully closed, the pin taper portions 342 and 352 abut against the valve gate taper portions 321 and 331. This state is the last retracted position of the gate pins 34 and 35.

  Table 1 shows a condition map 6 in this example. FIG. 6 is a graph showing the condition map 6. The advance position of the injection screw 21 and the advance and retreat positions of the gate pins 34 and 35 relative thereto are determined. The condition map 6 specifies optimal molding conditions by simulation such as CAE analysis or trial production actually performed by using an injection molding apparatus, and relates to the forward position of the injection screw 21 and the forward and backward positions of the gate pins 34 and 35 at that time. Create based on information.

Next, operations of the injection screw 21 and the gate pins 34 and 35 when performing injection control based on the condition map 6 will be described.
In this example, the advance position of the injection screw 21 decreases as the injection screw 21 advances. In addition, the value of the advance / retreat position of the gate pins 34, 35 decreases as the gate pins 34, 35 move forward. The gate pins 34 and 35 are in the last retracted position when the advance / retreat position is 20.00 mm, and the valve gates 32 and 33 are fully closed. As the gate pins 34 and 35 move forward and approach 0, the opening degree of the valve gates 32 and 33 increases and the discharge amount of the molten resin increases.

Until the injection control is started, the gate pins 34 and 35 are in the last retracted position, and the valve gates 32 and 33 are in the fully closed state.
When the injection screw 21 starts moving forward and moves to the forward moving position 210 mm, position control of the gate pins 34 and 35 is started. At this time, the gate pin 34 starts to move and linearly moves to the advance / retreat position 11.30 mm while the injection screw 21 advances to the advance position 110 mm, and gradually increases the amount of molten resin discharged from the valve gate 32. Let On the other hand, the gate pin 35 advances instantaneously to the advance / retreat position 10.6 mm, and starts discharging molten resin from the valve gate 33.
Next, when the injection screw 21 moves to the advance position 110 mm, the gate pin 34 reaches the advance / retreat position 11.3 mm and maintains the advance / retreat position.

Next, when the injection screw 21 reaches the advance position 103 mm, the gate pin 35 starts to move, and while the injection screw 21 moves to the advance position 74 mm, it moves linearly to the advance / retreat position 6 mm. The amount of molten resin discharged is gradually increased.
Next, when the injection screw 21 moves to the advance position 74 mm, the gate pin 34 starts to move, and while the injection screw 21 moves to the advance position 30 mm, it moves linearly to the advance / retreat position 9.2 mm. The discharge amount of the molten resin 32 is gradually increased. On the other hand, the gate pin 34 reaches the advance / retreat position 6 mm and maintains the advance / retreat position.

Thereafter, when the injection screw 21 moves to the forward position 30 mm, the molding is completed, and the injection screw 21 and the gate pins 34 and 35 return to the origin position.
As described above, any of the step control that instantaneously moves to the target advance / retreat position and the slope control that gradually moves to the target advance / retreat position can be used to control the advance / retreat positions of the gate pins 34, 35. .

  During the injection control based on the condition map 6 described above, the screw position sensor 22 and the pin position sensor 36 detect the position information of the injection screw 21 and the gate pins 32 and 33, respectively, and output them to the controller 5. The controller 5 compares the calculated target advance / retreat position with the advance / retreat position information detected by the pin position sensor 36, and performs feedback control continuously so that the advance / retreat position approaches the target advance / retreat position.

In this example, the optimal advance / retreat position of the gate pins 34, 35 is determined with respect to the advance position of the injection screw 21. That is, the inflow amount of the molten resin injected from the injection screw 21 and flowing into the valve gates 33 and 34 is grasped by replacing the advance position of the injection screw 21, and the discharge amount of the molten resin discharged from the valve gates 32 and 33 is Control is performed by replacing the forward and backward positions of the gate pins 34 and 35 directly related to the opening of the valve gates 32 and 33.
As a result, the control accuracy can be significantly improved as compared with the case where the pressure and flow rate are directly controlled, and the molten resin supplied to the valve gates 32 and 33 is discharged from the valve gates 32 and 33 into the cavity 31. The amount of molten resin discharged can be easily optimized.

In the condition map 6, the advance / retreat positions of the gate pins 34, 35 are determined in advance with respect to the advance position of the injection screw 21.
Therefore, when the condition map 6 is created, it is possible to determine the optimum advance / retreat position of the gate pins 34 and 35 so as to anticipate the influence of the inter-gate interaction and eliminate the influence. Thereby, in the injection molding method of the present example using the condition map 6 in which the optimal advance / retreat positions of the gate pins 34 and 35 are determined, the influence of the inter-gate interaction can be eliminated.

The advance / retreat positions of the gate pins 34, 35 are detected as pin position information, and the position control is performed by feedback control using the pin position information and the target advance / retreat position.
For this reason, the pin position information is compared with the target advance / retreat position, and control for correcting the advance / retreat positions of the gate pins 34, 35 to the target advance / retreat position is continuously performed. Therefore, the advance / retreat position of the gate pins 34, 35 can be brought closer to the target advance / retreat position more accurately.

Further, when the discharge port side of the valve gates 32 and 33 is the front end side and the opposite side is the base end side, the pin position sensor 36 is a branch that forms a flow path for supplying molten resin to the valve gates 32 and 33. It is arrange | positioned in the position of the base end side rather than the arrangement position of the runners 43 and 44.
Therefore, the pin position sensor 36 can be disposed at a position exposed to the outside of the mold unit 2. Therefore, compared with the case where the pin position sensor 36 is disposed inside the mold unit 3, the mold structure is not complicated.

  Moreover, since the pin position sensor 36 does not contact the molten resin, it is not necessary to consider heat resistance and durability. Therefore, the cost for the mold unit 3 and the pin position sensor 36 can be reduced. Further, the pin position sensor 36 can be exposed to the outside of the mold unit 3. Therefore, assembly and maintenance can be performed without disassembling the mold unit 3, and the maintainability can be improved.

  Further, in the case of a large and thin molded product such as the automobile bumper of the present example, the conventional injection molding method causes surface distortion of the design surface or cracking of the fixed mold 40 and the movable mold 41. There is a tendency that defects such as burrs are likely to occur in the part. In other words, this is because the control accuracy of the discharge amount and pressure of the molten resin discharged from the valve gate into the cavity is low, and the average internal pressure in the cavity is not uniform.

In this example, the amount of molten resin discharged from the valve gate into the cavity 31 can be easily optimized with respect to the amount of molten resin supplied from the injection unit to the valve gate. Therefore, the average internal pressure in the cavity becomes uniform, and a molded product with high quality without the above-described problems can be obtained.
In addition, in this example, although it showed about shaping | molding of the bumper for motor vehicles, the same effect is acquired by using the injection molding apparatus and injection molding method of this example also in various molded articles other than the bumper for motor vehicles. Can do.

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Injection unit 21 Injection screw 22 Screw position sensor 3 Mold unit 31 Cavity 32, 33 Valve gate 321, 331 Gate taper part 34, 35 Gate pin 341, 351 Step part 342, 352 Pin taper part 36 Pin position sensor 40 Fixed Mold 41 Movable mold 5 Controller 6 Condition map

Claims (5)

In an injection molding method in which molten resin injected from an injection screw is branched into a plurality of paths and injected into one or a plurality of cavities via a plurality of valve gates,
In the valve gate, a gate pin that adjusts the opening degree of the valve gate by moving forward and backward is provided, and the discharge amount of the molten resin discharged from the valve gate is controlled by the forward and backward position of the gate pin,
The inflow amount of the molten resin injected from the injection screw and flowing into the valve gate is grasped by the advance position of the injection screw, and the advance position of the injection screw when injecting the molten resin by the advance movement of the injection screw is determined. Detect as screw position information,
Considering gate interaction between the molten resin from the valve gate to flow respectively into said cavity, relative to the forward position of the injection screw, the condition map respective predetermined optimal forward and backward positions in the respective gate pin Using, the target advance / retreat position which is the optimum advance / retreat position of each gate pin with respect to the screw position information is obtained,
An injection molding method characterized in that position control is performed so that the advance / retreat position of each gate pin always approaches the target advance / retreat position.   2. The injection molding method according to claim 1, further comprising detecting the advance / retreat position of each gate pin as pin position information, and performing the position control by feedback control using the pin position information and the target advance / retreat position. . In an injection molding apparatus that branches a molten resin injected from an injection screw into a plurality of paths, and injects and fills one or a plurality of cavities through a valve gate provided for each path.
The injection molding apparatus includes a gate pin that adjusts an opening degree of the valve gate by moving back and forth in the valve gate;
A gate pin drive unit for controlling the forward / backward position of the gate pin;
A screw position sensor that detects a forward position of the injection screw when the molten resin is injected by forward movement of the injection screw, and outputs it as screw position information;
Considering gate interaction between the molten resin from the valve gate to flow respectively into said cavity, relative to the forward position of the injection screw, the condition map respective predetermined optimal forward and backward positions in the respective gate pin And a controller that outputs a target advance / retreat position that is an optimum advance / retreat position of each gate pin with respect to the screw position information using the condition map,
The amount of molten resin discharged from the valve gate is controlled by the advance / retreat position of the gate pin, and the amount of molten resin injected from the injection screw and flowing into the valve gate is determined by the advance position of the injection screw. ,
The injection molding apparatus, wherein the gate pin drive unit is configured to control the position of the advance / retreat position of each gate pin so as to always approach the target advance / retreat position.   4. The injection molding apparatus according to claim 3, further comprising a pin position sensor that detects an advance / retreat position of each gate pin and outputs the position as pin position information, and the position control includes the pin position information and the target advance / retreat position. An injection molding apparatus characterized by being configured to perform feedback control using.   5. The branch according to claim 3 or 4, wherein the pin position sensor forms a flow path for supplying molten resin to the valve gate when the discharge port side of the valve gate is the front end side and the opposite side is the base end side. An injection molding apparatus, wherein the injection molding apparatus is disposed at a position closer to the base end side than a position where the runner is disposed.

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