JPS58134722A - Supersonic-applied injection molding method - Google Patents

Abstract

PURPOSE:To improve the accuracy of the shape of a plastic part to be obtained by injection molding by such an arrangement wherein a cavity for forming the shape of the plastic part is composed by a horn to be vibrated by supersonic wave. CONSTITUTION:Molten forming material is injected into a cavity 21 which is maintained at a fixed low temperature of 30-80 deg.C through a runner 15 and a gate 16. Simultaneously with the injection of molten molding material, a supersonic oscillator 4 is caused to oscillate and supersonic is conveyed to a horn 1. Thermal energy is supplied to the interface between a solidifying layer 22 and a molten layer 23 of the forming material in the cavity 21, and it prevents the gradient of temperature of the molding material in the cavity 21 from becoming abrupt, even if the horn 1 is maintained at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for injection molding plastic parts using polymeric materials, and is particularly directed to high-precision molding techniques for plastic parts.

In recent years, advances in control technology for pressure, injection speed, temperature, etc. of injection molding equipment have led to the application of injection molded plastic parts to high-precision parts. However, in the conventional injection molding method, the temperature of the molding material injected into the cavity and the temperature of the mold are preconditioned to be 200-10 Y; - There is an unavoidable drawback that temperature non-uniformity similar to the previous temperature difference occurs in the cooling layer 1i. For this reason, the internal composition of the molding material inevitably contains uneven distribution of physical properties such as orientation, crystallinity, density, shrinkage rate, etc.
Strict resemblance to the cavity shape is inhibited. Therefore, conventional injection molding methods have the disadvantage that they cannot achieve the same high precision as parts that are cut and polished.

In order to improve the drawbacks of the prior art, the present invention significantly reduces the temperature non-uniformity inside the molding material during the injection and cooling process in the cavity compared to the conventional method, thereby improving the quality of plastic parts obtained by injection molding. An object of the present invention is to provide an injection molding device that can significantly improve shape accuracy.

The cavity is constructed with an ultrasonic horn with cooling holes, and the molding material is injected into the cavity which is being ultrasonically vibrated while being cooled. The vibration energy transmitted from the horn to the molding material is converted into thermal energy at the interface between the solid phase and the molten phase of the molding material, so that thermal energy can be supplied to the interface between the same phase and the molten phase of the molding material. By controlling the oscillation conditions, the injection and cooling process can be performed while significantly reducing the temperature gradient temperature distribution inside the molding material during the injection and cooling process in the cavity compared to conventional methods. This is the principle of the invention.

The figure is an overall view of an injection molding apparatus according to the present invention.

In the figure, 1 is a horn for ultrasonic vibration that also serves as a cavity surface according to the present invention. 2 is corn.

6 is a converter, 4 is an ultrasonic oscillator, and 5 is a control device that automatically changes oscillation conditions (frequency, amplitude).

6 is electric fishing, 7 is horn 1. Cone 2. A mounting base 8 supporting the conversion 85 is a hydraulic cylinder that sets the horn 1 in a predetermined position against the molding pressure applied to the cavity surface. Reference numeral 9 denotes a cooling hole provided in the horn 1, through which a coolant at a constant temperature circulates. 10 is a fixed 11J, 11c is a fixed 1M#, 12c is a mounting plate A, 16 is a mounting plate B, 14 is a heater, 15 is a runner, which is a hot runner by the heater 14, and melts heat at a constant high temperature (250 to 5tsov). Filled with plastic molding material. 16 is a gate. 1
0 to 16 form the fixed side of the mold and are attached to the injection molding material fixed side die plate 17. 18 is movable type, 19
is a movable mounting plate, and +8i9 is attached to the injection molding material movable side die plate 20. 21 is a cavity that shapes the shape of the plastic part, and horn 1. Fixed type A10.
It is formed by a movable [1B]. The ultrasonic excavation device consisting of the horn 1 to the hydraulic cylinder 8 is located in the cavity 21.
There are two sets each on the front and back sides.

Next, the operation of the device of the present invention will be explained. The molten molding material at a constant high temperature is injected from the molding material through the runner 15. gate 16
and is injected into the mold cavity 21, which is maintained at a constant low temperature within the range of 50-80°C. Simultaneously with the injection of the molten molding material, the ultrasonic oscillation machine 4 is oscillated and the ultrasonic waves are transmitted to the horn 1.

Since the temperature of the horn 1 is maintained at a low temperature, the layer of the molten molding material that advances into the cavity 21 from the gate 16 and contacts the surface of the cavity 210 is instantaneously solidified by the force t that forms the assimilated layer 22. , it is heated because ultrasonic vibrations are transmitted from the horn 1. Under such an environment, the molding material fills the cavity 21. Ultrasonic vibration is in cavity 21
The injected molding material is rapidly attenuated at the interface between the solidified layer 22 and the molten phase 25, and is converted into thermal energy. jru.

Solidified layer 22 and molten phase 25 of molding material in cavity 21
Since thermal energy is supplied to the interface of .

Even though the temperature of the horn 1 is maintained at a low temperature, the temperature gradient of the molding material in the cavity 21 can be prevented from becoming steep, and the temperature of the molding material can be made uniform.

Upon completion of the injection, the ultrasonic oscillation conditions are gradually changed by the control device 5 according to a preset program, thereby gradually decreasing the thermal energy supplied into the cavity 21. In this way, the temperature gradient of the molding material inside the cavity 21,
The injection and cooling process can be carried out while maintaining the temperature non-uniformity to a much smaller value than in conventional methods. The step of removing the molded product from the mold after cooling is completely the same as in the conventional method and will therefore be omitted.

As described above, in the present invention, the temperature non-uniformity of the molding material from the time it is injected into the cavity 21 until it is cooled and solidified and released from the mold is much improved compared to the conventional method. Since the injection and cooling process is carried out in the same state, physical nonuniformity in orientation, crystallinity, density, and shrinkage rate of the internal composition of the plastic part is greatly reduced. In this way, it is possible to achieve a uniform internal composition of plastic parts, which cannot be avoided using conventional methods. Warpage and sink marks are significantly reduced, a shape that closely resembles the shape of the cavity 21 is realized, and dimensional accuracy is greatly improved. As a result, it has become possible to supply plastic parts by injection molding with almost the same precision as if they had been cut and polished with high precision. Moreover, since the temperature of the mold itself is the same as in the conventional method, the molding cycle is not much longer than in the conventional method (and mass productivity is also good).

[Brief explanation of drawings]

The figure is an overall view of an apparatus showing an embodiment of the present invention. 1...horn, 2...cone. 3...Converter, 4...Ultrasonic oscillator. 5... Development condition control device. 8... Hydraulic cylinder, 9... Cooling hole. 10...Fixed ffi, 4. 14... Heater. 15...Hot runner-118...Movable type. 21... Cavity, 22... Assimilation layer. 23... Molten layer. Representative Patent Attorney Susuki 1) Toshiyuki

Claims (1)

[Claims] t. An injection molding method using ultrasonic waves, characterized in that, in an injection mold for injection molding using a polymeric material, a cavity for forming the shape of a plastic part is configured with a horn for ultrasonic vibration.