JP2554938B2 - Injection molding apparatus and injection molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an injection molding apparatus and an injection molding method, and more particularly to an injection molding apparatus and an injection molding method capable of controlling a screw retreat speed during plasticization measurement.

(Prior Art) As a method of controlling a screw retreat speed of a screw type injection molding machine to prevent molding defects at the time of molding, for example, JP-A-61-121921 (hereinafter referred to as the former) and JP-A-63-121921 The technology described in Japanese Patent No. 170015 (hereinafter referred to as the latter) is well known.

The former prior art detects the screw retreat speed at the time of plasticization measurement during injection molding, compares the detected screw retreat speed with the target retreat speed, calculates the screw in a direction in which the deviation is eliminated. By controlling the rotation of the screw, the screw retreat speed is always controlled to be constant.

Further, the latter conventional technique detects a screw retreat speed at the time of plasticization measurement during injection molding, compares the detected screw retreat speed with a preset target value, and eliminates the difference between the two. By controlling the screw back pressure as described above, the thermal history of the molten resin and the molding cycle are always made to be the same.

In other words, by controlling the screw retreat speed to be constant, it is possible to eliminate fluctuations in the screw retreat speed due to subtle differences in conditions such as the particle size of the resin material and the production lot. Thus, when the weighing time is equal to or longer than the cooling time, it is possible to suppress a change in the entire molding cycle time due to a change in the weighing time.

Also, if the molding cycle fluctuates, the mold heating / cooling cycle also fluctuates, but by keeping this molding cycle constant, variations in mold temperature can be eliminated and more precise molding can be performed. Become.

(Problems to be Solved by the Invention) However, when the screw rotation speed and the back pressure are controlled and varied as in the above-described conventional example, the amount of heat generated by shearing in the compression measuring section of the screw varies, and the viscosity and the like increase. However, there is a problem that it is difficult to perform stable precision molding due to variations in physical properties of the material.

The present invention has been made to solve the above problems, and an object of the invention is to control the screw rotation speed and resin pressure of the material supply unit or the material supply amount to control the screw retreating speed during plasticization measurement. The object of the present invention is to provide an injection molding apparatus and an injection molding method capable of performing precise molding by stabilizing the molding cycle by stabilizing the molding cycle.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is an injection for carrying out molding by transporting a molding material melted by screw rotation to the front of the screw and injecting it into a mold under pressure. In the molding apparatus, the screw is at least two in the front part and the rear part.
It is characterized in that the screw rotation speed of each divided part can be set individually, and the rear part of the divided screw is arranged so that the screw can be slid in the axial direction, The resin pressure can be set independently of the screw back pressure.Furthermore, the supply screw is arranged slidably in the axial direction, and is formed in a taper shape along the axial direction, so that the material supply amount can be increased. It is characterized by making it variable.

Furthermore, the present invention is an injection molding method for detecting the actual screw retreat speed during plasticization measurement, and feeding back the detected speed so as to approach a preset target retreat speed of the screw. The screw is divided into at least a front part and a rear part, and the rotational speed of the rear part feed screw of the divided screws is variably controlled and molded, and the feed part screw is axially formed. It is characterized in that it is slidably disposed on the supply part, and the resin pressure of the supply part is variably controlled to form the resin. Furthermore, the supply part screw is disposed so as to be slidable in the axial direction, and is tapered along the axial direction. It is characterized in that the material is formed, and the material supply amount is variably controlled by sliding the screw of the supply section.

(Operation) With the above-mentioned configuration, the present invention focuses on the fact that the fluctuation of the screw retreat speed is caused by the change of the material supply amount due to the subtle difference in the particle diameter of the molding material such as resin and the manufacturing lot. , For example, the screw rotation speed can be set individually by dividing the screw into multiple parts such as the front part, middle part, rear part, etc., and among these divided screws, the screw rotation speed of the material supply part can be made variable, or Of the above-mentioned screws, the screw of the material supply unit can be slid in the axial direction to make the resin pressure variable, and further, the above-mentioned screw of the supply unit is formed in a taper shape along the axial direction, and this is slid to slide the material supply amount. The screw retraction speed is kept constant by making the screw variable.

Then, in the present invention, the actual screw retreat speed at the time of plasticizing measurement is detected by the sensor, the deviation between the detected actual screw retreat speed and the preset target speed is calculated, and this deviation is eliminated. In order to suppress the fluctuation of the supply amount due to the variation of the material by controlling the screw rotation speed of the material supply unit or the resin pressure or the material supply amount,
The screw retreat speed is kept constant.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an injection unit (plasticizing and measuring section) in an injection molding device.

In the figure, the screw cylinder 1 is a casing 13
The screw cylinder 1 is integrally connected to the injection cylinder 3 via a screw, and the screw 2 for transferring the molten molding material to the front side is inserted into the screw cylinder 1. The injection piston 4 in the injection cylinder 3 is arranged so as to be movable in the axial direction by hydraulic pressure, and is connected to the screw rotation drive motor 5. The screw rotation drive motor 5 is
It can rotate according to the hydraulic pressure supplied from a hydraulic pressure source (not shown) via a servo valve or the like.

At the time of molding, the resin melted by the rotation of the screw 2 is transferred to the front of the screw 2, and the screw 2 is retracted by the molten resin pressure accumulated in the front of the screw to perform injection molding.

Here, the present invention is characterized in that the screw 2 is divided into at least two parts, a front part and a rear part, and the screw rotation speed of each divided part can be set individually.

That is, in this embodiment, as shown in FIG. 1, the screw 2 compresses and measures the molten material.
Measuring unit screw 2a and feeding unit screw that supplies materials
It is divided into two with 2b. Compression / measurement section screw
2a, the front part is formed with a large diameter and the rear part is formed with a small diameter, the supply part screw 2b has a hollow cylindrical part 15 formed in the center part thereof, and the compression / measurement part screw 2a has this hollow cylindrical part.
It is connected to the injection piston 4 through 15. Further, in the rear part of the supply screw 2b and in the front part of the injection piston 4, there are a gear 16 and a gear whose rotation axis matches the screw shaft.
18 are formed respectively. The supply screw
The gear 16 on the 2b side is in mesh with the gear 18 on the injection piston 4 side via a rotation speed converter 14 and intermediate gears 17a, 17b arranged in the casing 13. Therefore, the compression / measurement unit screw 2a is directly driven by the screw rotation drive motor 5, and the supply unit screw 2b is the intermediate gear.
It is indirectly driven via 17a, 17b and the like. That is, the rotation speed of each screw 2a, 2b can be controlled independently.

From the above, for example, in the compression / measuring unit with a large amount of shearing heat generation in the screw cylinder 1, it is possible to set the rotation speed of the compression / measuring unit screw 2a small while setting the rotation speed of the supply unit screw 2b large. Therefore, various rotation speeds can be combined according to the properties of the molding material.

In addition, in the present embodiment, the case where the screw 2 is divided into the front part and the rear part is described, but the present invention is not limited to this. For example, the screw 2 is divided into a plurality of parts such as the front part, the middle part and the rear part, and It is also possible to individually set the number of rotations of.

Further, in the present invention, in the injection molding method for detecting the actual screw retreat speed at the time of plasticizing measurement, and feeding back the detected speed so as to approach the preset target retreat speed of the screw, Divide the screw into at least two parts, front and rear,
Among the divided screws, the rotation speed of the rear feeding screw is variably controlled to perform molding.

As shown in FIG. 2, the injection piston 4 includes:
A rack 6 that moves in the axial direction integrally with this is provided, and a pinion 7 is meshed with this rack 6 and a sensor 8 for detecting the retreat speed of the compression / measuring unit screw 2a is provided on the pinion 7. Has been.

The output of the sensor 8 is passed through an amplifier 9 to a comparator.
The target reverse speed of the compression / measuring unit screw 2a is preset in the screw reverse speed setting device 11, and the output from the screw reverse speed setting device 11 is also input to the comparison calculator 10. Is entered. The comparison calculator 10
Then, the actual reverse speed of the screw 2a and the target reverse speed are compared and calculated, and the rotational speed converter 14 is controlled via the transmission controller 12 based on a signal corresponding to the difference.
As a result, the rotation speed of the supply screw 2b is variably controlled via the intermediate gears 17a and 17b.

That is, if the output of the sensor 8 is smaller than the target set value as a result of the calculation in the comparison calculator 10, control is performed to increase the rotation speed of the supply section screw 2b, and conversely, the output of the sensor 8 is set to the target setting. If it is larger than the value, control is performed to reduce the rotation speed of the supply screw 2b. In this way, the deviation between the output of the sensor 8 and the target set value is eliminated.

According to this embodiment, the retreating speed of the compression / measurement section screw 2a is always kept constant even if the rotation speed of the supply section screw 2b varies depending on the properties of the resin material and the like. Therefore, the plasticization measuring time in each cycle is constant, the molding cycle is also constant, the molding conditions are stabilized, and highly accurate molding can be performed.

Next, in the present invention, the divided screws 2a, 2b
Of the rear part, the supply screw 2b is arranged slidably in the axial direction, and the resin pressure of the supply part can be set independently of the screw back pressure, and the resin pressure is variably controlled to perform molding. It is characterized by

The members that are the same as or correspond to those in the above-described embodiment,
The same reference numerals are given and the description thereof is omitted.

That is, in FIG. 3, in the present embodiment, the feeding section screw 2b is arranged so as to be slidable in the axial direction, and the screw 2 is the compression / measuring section screw 2a and the feeding section screw 2b, as in the above-mentioned embodiment. The compression / measurement section screw 2a is arranged so as to be axially movable by the injection piston 4 and rotatable by the screw rotation drive motor 5.

The supply screw 2b is provided with a gear 16 whose rotation axis coincides with that of the screw shaft at the rear portion, and further behind that, an injection piston 24 in an injection cylinder 23 formed in the casing 13 is integrally connected. Has been done. The gear 16
Is meshed with a gear 18 on the injection piston 4 side via a rotation speed converter 14 and intermediate gears 17a, 17b. For this reason, the screw 2b in the supply section is
It is movable in the axial direction by 24 and rotatable by the screw rotation drive motor 5.

According to the present embodiment, not only can the rotation speed of the supply screw 2b be variably controlled, but also axial sliding is possible regardless of the back pressure of the compression / measurement screw 2a. The resin pressure of the supply section can be variably controlled. Therefore, the material density and the like can be made uniform at the entrance of the compression / measurement unit screw 2a, and stable measurement can be performed.

 FIG. 4 shows the control block diagram.

That is, as a result of the comparison calculation in the comparison calculator 10, if the output of the sensor 8 is smaller than the set value set as the target value, the pressure applied by the supply section screw 2b is increased, and conversely, the sensor output is smaller than the set value. If it is larger, a signal for reducing the pressure applied by the supply screw 2b is sent to the rotation speed converter 14 via the converter controller 12. In this way, the deviation between the sensor output and the set value is eliminated.

Further, in the present invention, the supply screw 2b is arranged so as to be slidable in the axial direction, is formed in a taper shape along the axial direction, and the material supply amount is variably controlled by sliding the supply screw 2b. And then molded.

That is, in this embodiment, the supply section screw 2b in FIG. 3 described above is formed in a tapered shape along the axial direction.

In FIG. 5, the feed section screw 2b has a small diameter at the front end, and is formed in a taper shape having a larger diameter toward the rear end side. Therefore, by moving the supply section screw 2b in the axial direction, the groove depth of the screw itself varies depending on the feed position, and the material supply amount can be made variable. In addition, the compression ratio can be changed freely, and the compression ratio can be set to an optimum value according to the molding material.

FIG. 6 shows a control configuration block diagram of this embodiment.

In the figure, the result of the comparison calculation in the comparison calculator 10 is input to the servo valve controller 19, and the injection piston 24 is controlled to move via the servo valve 20 by a control signal from the controller 19.

That is, as shown in FIGS. 7 (a), (b) and (c), the screw retreat speed and the target value are equal to each other.
If the output of the sensor 8 is smaller than the set value set as the target value as a result of the comparison calculation from the state of FIG.
As shown in FIG. 7 (c), slide the supply screw 2b so that the deep part of the screw groove is located at the bottom of the hopper. Conversely, if the sensor output is larger than the set value, the
As shown in Figure (b), the feeding section screw 2b is slid so that the shallow portion of the screw groove comes under the hopper.
In this way, the deviation between the sensor output and the set value is eliminated.

(Effect of the invention) As described above, the present invention divides a screw into a plurality of parts such as a front part and a rear part so that the rotation speed of each screw can be freely changed, or by making it axially slidable,
In addition, the actual screw retreat speed during plasticization measurement is detected, the deviation between this detected speed and the target retreat speed is calculated, and the screw rotation speed, resin pressure or material By controlling the supply,
The metering time is constant, the molding cycle is stabilized, and more precise molding can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an injection unit in an injection molding apparatus, FIG. 2 is a block diagram showing a control configuration thereof, FIG. 3 is a diagram showing a schematic configuration of an injection unit in another embodiment, and FIG. Is a block diagram showing its control configuration, FIG. 5 is a diagram showing a schematic configuration of an injection unit in still another embodiment, FIG. 6 is a block diagram showing its control configuration, and FIGS. 7 (a) (b) ( FIG. 7C is a diagram showing an operating state of the supply section screw based on the control operation of FIG. 6. 2 …… Screw 2a …… Compression / measurement section screw 2b …… Supply section screw 3,23 …… Injection cylinder 4,24 …… Injection piston 5 …… Screw rotation drive motor 8 …… Sensor 10 …… Comparison unit 11 ...... Screw reverse speed setting device 12 ...... Transmission controller 14 …… Rotary speed converter 16,18 …… Gear, 17a, 17b …… Intermediate gear 19 …… Servo valve controller 20 …… Servo valve

Claims (6)

(57) [Claims] 1. An injection molding apparatus for transferring a molding material melted by screw rotation to the front of the screw and injecting it into a mold for molding, wherein the screw has at least two parts, a front part and a rear part. The injection molding apparatus is characterized in that the number of rotations of the divided screw can be individually set. 2. The apparatus according to claim 1, wherein among the divided screws, a rear supply screw is disposed slidably in the axial direction, and the resin pressure of the supply can be set independently of the screw back pressure. An injection molding device characterized in that 3. The apparatus according to claim 1, wherein the supply screw is arranged so as to be slidable in the axial direction, and is formed in a taper shape along the axial direction so that the material supply amount can be changed. Characteristic injection molding equipment. 4. An injection molding method in which an actual screw retreat speed during plasticization measurement is detected, and the detected speed is fed back to perform control so as to approach a preset target retreat speed of the screw. An injection molding method, characterized in that at least a front part and a rear part are divided into two parts, and among the divided screws, the rotational speed of a rear part feed screw is variably controlled and molding is performed. 5. The injection molding method according to claim 4, wherein the screw of the supply part is slidably arranged in the axial direction, and the resin pressure of the supply part is variably controlled to perform the molding. Method. 6. The injection molding method according to claim 4, wherein the feed screw is formed in a taper shape along the axial direction, and the feed screw is slid to control the material feed amount variably. An injection molding method, which comprises: