JP2673491B2 - Amorphous molding material supply method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous molding material of a thermoplastic resin having irregular sizes such as flakes, small particles, powders, etc., such as a crushed material for PET bottles, or a mixed molding material thereof. Etc. to a molding machine equipped with a plasticizing screw in a cylinder, such as injection or extrusion.

[0002]

2. Description of the Related Art When a flaky or powdery molding material is supplied from a hopper to a molding machine by natural fall, a bridge is formed and the supply amount becomes unstable. Therefore, forced supply by a screw is adopted. A method of disposing a supply screw in a material supply unit of a molding machine such as injection or extrusion and forcibly supplying a molding material of a thermoplastic resin to the molding machine by controlling the rotation of the supply screw is disclosed in JP-A-60-11642.
No. 4 and Japanese Patent Application Laid-Open No. 5-318531.

The means described in JP-A-60-116424 described above detects the pressure of the resin raw material at the lower portion of the screw type forced feeder arranged in the extruder and the screw base portion in the extruder with a sensor, and the sensor is used. By controlling the rotation speed of the forced feeder screw so that the pressure of the resin raw material is always constant, the powder raw material, the mixed raw material of powder and pellets, and the flaky raw material can be stably supplied. There is.

Further, the means disclosed in Japanese Patent Laid-Open No. 5-318531 successively detects a reaction force that hinders the rotation of the injection screw and controls the increase / decrease in the feed speed of the pellet feeder corresponding to the increase / decrease in the reaction force. Is to control the supply of pellets.

[0005]

In the method of detecting the pressure of the resin raw material and controlling the rotation speed of the forced feeder screw, the force of feeding by the forced feeder screw is used to form flakes having a bulk density higher than that of powder. It is difficult to keep the pressure of the molding material constant, and the pressure easily fluctuates. For this reason, rotation control is frequently performed, and even if rotation control is performed by detecting the pressure of the resin raw material, it is not possible to stably supply the flaky molding material because of the problem of responsiveness. This also applies to the case where the reaction force that prevents the rotation of the injection screw is sequentially detected and the feed rate of the molding material is controlled to increase or decrease, and new means is required to achieve a stable supply of flaky, amorphous molding material. It is said that.

The present invention was conceived in order to solve the above-mentioned conventional problems, and its purpose is to grasp the trend of the rotational torque of the plasticizing screw corresponding to the rotational speed during the material supply of the supply screw. , Thereby setting the rotation of the supply screw so that the material can be supplied while maintaining a constant density, and not only flaky amorphous molding materials but also other amorphous molding materials Similarly, it is to provide a new method that enables stable supply.

[0007]

According to the features of the present invention according to the above object, a supply screw is arranged in a material supply portion of a molding machine having a plasticizing screw in a cylinder, such as injection or extrusion, and the supply screw is When forcibly supplying an indeterminate thermoplastic resin molding material whose shape and size are not uniform due to rotation into the cylinder, the rotation torque of the plasticizing screw corresponding to the rotation speed during the material supply of the above-mentioned screw is detected. Then, the material is supplied by setting the rotation speed of the supply screw based on the inflection point of the rotation torque.

In the above method according to the present invention, a hydraulic molding machine in which the drive source of the plasticizing screw is hydraulic and the drive source of the supply screw is an electric motor, and an electric motor in which both the drive sources of the plasticizing screw and the supply screw are electric motors It can be used in any of the molding machines.

In the case of a hydraulic molding machine, the difference in hydraulic pressure between the inlet and outlet of an oil motor that rotationally drives a plasticizing screw is
It is detected as the rotation torque of the plasticizing screw. In the case of an electric molding machine, the electric current value of the electric motor of the plasticizing screw is measured and the measured value is detected as the rotational torque.

[0010]

[Operation] When the rotation speed of the plasticizing screw is kept constant and the rotation speed of the supply screw during material supply is gradually increased to increase the material supply amount, the rotation torque of the plasticizing screw also corresponds to the rotation speed. However, when a certain number of rotations is reached, the rotation torque suddenly rises and changes. In the present invention, the changed portion is used as the inflection point of the rotational torque and is used as a guideline for setting the rotational speed of the supply screw. This makes it difficult for the plasticizing screw to rotate, and eventually stops.

However, in the material supply by the rotation speed in the range around the inflection point, the density of the molding material by the supply screw is maintained at an appropriate level, and there is no variation in the bite of the molding material by the rotation of the plasticizing screw. Even in the case of molding for a long time, a predetermined amount of molding material is constantly supplied to stabilize the plasticization, and the instability of the measuring time, which is a problem of the molding material having an irregular shape in the injection molding machine, is eliminated.

[0012]

The present invention will be described below by taking an injection molding machine as an example. In the figure, reference numeral 1 denotes a plasticizing screw, which is installed in a heating cylinder 2 provided with a band heater (not shown) around its outer periphery so as to be rotatable and movable back and forth. Further, a material supply port 3 is provided on the rear part of the heating cylinder 2, and a material hopper 5 having a supply screw 4 vertically provided at the inner center of the material supply port 3 is provided.
However, the tip of the cylinder formed at the bottom is connected to the material supply port 3
It is fitted and attached to. As a result, the supply screw 4
Is located near the plasticizing screw 1 with a required gap.

A motor 6 for the supply screw 4 is provided above the material hopper 5, and by the rotation of the supply screw 4 by the motor 6, the amorphous molding material 7 in the material hopper is supplied to the material supply port 3. It can be forcibly supplied.

Reference numeral 8 denotes a hydraulic motor for rotating the plasticizing screw 1, which is connected to the rear end of the injection cylinder 9 for moving the plasticizing screw 1 forward, and the hydraulic pressure at the inlet side and the outlet side of the hydraulic motor 8 is increased. Pressure gauges 10 and 11 are provided on the path.
In addition, 12 shows a hydraulic pump.

In the injection molding machine having the above-mentioned structure, an amorphous molding material 7 made of flaky recycled polyethylene terephthalate having different shapes and sizes is stored in the material hopper 5, and the number of revolutions of the plasticizing screw 1 is made constant. By rotating the supply screw 4, the molding material 7 is supplied to the material supply port 3
When the molding material 7 is forcibly supplied to the heating cylinder 2, the molding material 7 is sequentially taken into the heating cylinder 2 by the rotation of the plasticizing screw 1 and is transferred forward. Further, while being melted and kneaded (plasticized), it is pressure-fed to the tip portion of the screw, and the plasticized screw 1 is gradually retracted by the pressure of the molten material accumulated at the tip portion to perform measurement.

The amount of the molding material 7 supplied to the plasticizing screw 1 increases in proportion to the number of revolutions of the supplying screw 4, but the number of revolutions becomes excessive if the number of revolutions of the plasticizing screw 1 is taken into consideration. As a result, the material supply port 3 is strongly compressed, which exerts a large load on the rotation of the plasticizing screw 1, resulting in an unfavorable state.

Therefore, when the load of the material supply amount on the plasticizing screw 1 having a constant rotation speed was examined for each rotation speed of the supply screw 4, a rotation torque as shown in FIG. 3 was clarified. The rotation torque of the plasticizing screw 1 depends on the pressure difference between the pressure gauges 10 and 11 of the hydraulic motor 8.

The plasticizing screw 1 in the above embodiment,
The design values of the supply screw 4 are as follows.・ Plasticizing screw Screw diameter 36.0 mm Groove depth 5.0 mm (Feed zone) L / D 19.0 Rotation speed 150.0 rpm ・ Supply screw Screw diameter 32.0 mm Groove depth 6.0 mm P / D 0.6・ Supply amount per revolution speed Revolution speed (rpm) 20 30 40 50 Supply amount (g / Sec) 3.1 4.1 5.4 6.4 ・ Tip gap of supply screw to plasticizing screw
50mm ・ Molding material PET container crushed material (flakes)

As is clear from the results shown in FIG. 3, the rotation torque of the plasticizing screw 1 suddenly increased at the rotation speed of the supply screw 4 of 40 rpm, and stopped when the rotation speed exceeded 50 rpm. When the irregular molding material 7 was supplied with the rotational speed of the abruptly changing portion as an inflection point of the rotational torque, the molding material 7 bites at a rotational speed just around the rotational speed of the abruptly changing portion. The condition was good and smooth, there was no variation in the supply amount, and the weighing time each time was almost constant.

However, if the number of revolutions is small, the amount of supply is small as described above and it takes time to measure. Therefore, from the viewpoint of shortening the metering time, supply at low speed is not preferable. Further, in the case of supplying at a rotational speed of a portion where a rotational torque greatly exceeding the inflection point, the reason for this is not clear, but the measurement time becomes uneven, and the energy consumption increases.

The number of revolutions 40, which is an inflection point of the above-mentioned rotational torque.
In the material supply at rpm, the energy consumption does not increase so much, the material supply is stable with an appropriate supply amount, and the metering time is within the allowable range. In addition, at a rotation speed of 35 rpm, there is no difference from the rotation speed of 40 rpm except that the weighing time is slightly longer, and the rotation speed is 42 rp.
At m, the rotational torque increases, but there is no variation in the supply amount,
A stable weighing can be obtained.

Therefore, as long as the molding material 7 is forcibly supplied within the range before and after the number of revolutions which is the inflection point, even an irregular molding material that is easily affected by the bulk density. A stable supply is possible.

To detect the inflection point, the rotational torque of the plasticizing screw 1 for each rotational speed is recorded in a graph while changing the rotational speed of the supply screw 4, and the inflection point is determined from the graph to determine the inflection point in the motor 6. Basically, the number of revolutions is set, but as shown in Fig. 2, the differential pressure by the pressure gauges 10 and 11 is electrically calculated to read the rotational torque for each number of revolutions, and the value is graphed and changed. A control device 1 for determining a bending point and instructing the motor 6 to output the rotation speed of the portion.
By arranging 3, the rotation speed can be automatically set.

[0024]

As described above, the present invention detects the rotation torque of the plasticizing screw corresponding to the rotation speed during the material supply of the supply screw, and rotates the supply screw using the inflection point of the rotation torque as a guide. Since the material supply amount is set by setting the number, even if it is a flake-shaped reclaimed resin made of pulverized material, the supply amount tends to fluctuate due to poor feeding.
Material is supplied while maintaining appropriate density, and as a result,
Plasticization and weighing are stable, and good products can be molded. In addition, since it is only necessary to detect the inflection point and measure it at the number of rotations of that part, technically complicated operation is not required, and even if the molding material changes, the inflection point suitable for that molding material can be obtained. Since it is possible to easily detect and set the number of revolutions, it is possible to apply to a mixture of a plurality of molding materials having different shapes and the like to perform stable supply.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an injection molding machine that can carry out a method for supplying an amorphous molding material according to the present invention.

FIG. 2 is a schematic explanatory view of an injection molding machine of another embodiment.

FIG. 3 is a diagram showing a correlation between a rotation torque of a plasticizing screw and a rotation speed of a supply screw.

[Explanation of symbols]

 1 Plasticizing Screw 2 Heating Cylinder 3 Material Supply Port 4 Supply Screw 5 Hopper 6 Motor 7 Molding Material 8 Hydraulic Motor 9 Injection Cylinder 10 Pressure Gauge 11 Pressure Gauge 13 Controller

Claims (1)

(57) [Claims] 1. A supply screw is disposed in a material supply section of a molding machine such as an injection or extrusion machine having a plasticizing screw in a cylinder, and the shape and size of the supply screw are irregular due to rotation of the supply screw. When forcibly supplying the molding material of the thermoplastic resin into the cylinder, the rotation torque of the plasticizing screw corresponding to the rotation speed during the material supply of the above-mentioned screw is detected, and the inflection point of the rotation torque is supplied as a guide. A method for supplying an amorphous material, characterized in that the material is supplied by setting the number of revolutions of the screw.