JPH02131910A - Injection molding process and its device - Google Patents

Abstract

PURPOSE:To obtain the molded object with very small shrinkage of dimension by a method in which not only ultrasonic wave vibration is applied to a mold, but also the mold is resonated, thereby improving the fluidity of material, and further the stress effect of ultrasonic wave in which the molding material brought into contact with the resonator of ultrasonic wave is drawn to the node, is used. CONSTITUTION:The nozzle 4 of a molding machine is brought into pressure- contact with the sprue 3a of the mold 3 of stationary side, and while molding is achieved by injection molding material into a cavity 2a through the sprue 3a, the mold 1 is resonated in (n)-wavelength by generating a vibrator 10 ultrasonic wave vibration by an ultrasonic wave generator 12. In order to act very effectively ultrasonic wave on the material in molding, the frequency of 10 kHz-100kHz is used. In the resonance of (n) wavelengths, (n) is m/2 (m is positive integer), but in order to cause the node of resonance to coincide with the contact part of the stationary mold or the nozzle, the number of the node is as small as possible, and (n) is preferably less that three. Further, even in the case of n<3, the mold is resonated so that the loop of resonance coincide with the cavity 3a, and the vibrator effect of ultrasonic wave is used most effectively.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides an injection molding method that enables molding of a molded product with high physical properties and good appearance when injection molding a molding material t1 such as a polymeric material. This article relates to a molding method and its device.

[Prior Art] Conventionally, injection molding methods have been widely used for molding products made of thermoplastic resins or materials whose main composition is thermoplastic resins, as they have the great advantage of high productivity. There is.

However, in recent years, with the progress of research on the physical properties of thermoplastic and plastic resins, it has been found that the rigidity, If}l thermal properties, and I6I chemical properties of molded products are greatly influenced by the molecular weight of the material < , s or plastic resin). This is becoming known. However, the molecular weight of thermoplastic resins that can be molded using conventional injection molding methods is not that large, and the molecular weight is generally smaller than that of those commercialized as film grades. Therefore, there have been cases where molded products have poor physical properties such as rigidity, heat resistance, and chemical resistance. Therefore, from the perspective of improving physical properties, a method of molding that attempts to increase the molecular weight of the resin that makes up the molded product by improving the fluidity of the resin during injection molding has begun to be considered.
Several proposals have been made so far. For example, the method of applying ultrasonic vibration to the gate part of a mold proposed in Japanese Patent Publication No. 57-2088, or the method proposed in Japanese Patent Publication No. 61-4
There is a method of inductively heating the mold surface using high frequency waves, as proposed in No. 4616. On the other hand, when a polymeric material is used for injection molding, the polymeric material is heated and filled into a mold.

For this reason, the molded product thermally expands when heated and contracts when cooled in the mold, resulting in only a molded product smaller than the cavity size of the mold.

Therefore, several proposals have been made to reduce the shrinkage of the material filled in one mold with the aim of improving the dimensional accuracy of molded products. For example, a method of molding by lowering the temperature of the material by significantly increasing the injection pressure and similarly increasing the mold clamping force, or
1:14722, the cavity is configured as a horn for ultrasonic vibration, and the material is injected into the cavity and the non-uniformity of the material temperature during the cooling process is greatly reduced. There are ways to do this. [Problems to be solved] However, the conventional forming method described above had the following problems. That is, Special Publication No. 57-2088. JP-A-58-1
The technology proposed in No. 34722 has the problem that the structure of the mold is very complicated, that the ultrasonic vibrations adversely affect the mold itself and other parts of the equipment, and that the material and horn are in direct contact with each other. Due to the vi contact structure, a large load was placed on the horn and the vibration generating part, which caused the problem of not being able to sufficiently apply ultrasonic vibration to the material. Further, as a result of experiments, it was revealed that the technology proposed in JP-A-61-44615 does not improve the fluidity of the resin as much as expected even when the mold surface is heated. Roughly speaking, there is a method of molding by lowering the mold clamping temperature of the material by increasing the injection pressure by two times and increasing the mold clamping force as well.
There was a problem that ↑ appeared on the molded product and it did not deform when used as a product. 7 (The invention was made in view of the above problems, and the first invention does not simply apply tII hill wave vibration to the mold, but rather improves the fluidity of the material by making the mold resonate. The aim is to provide a dramatically improved injection molding method, and furthermore, the stress effect of ultrasonic waves is that the molding material that comes into contact with the ultrasonic resonator is attracted to the nodes (resonant nodes).
The purpose of the present invention is to provide an injection molding method that makes it possible to obtain a molded product with extremely small dimensional shrinkage compared to when molding material is pressed into a cavity using only injection pressure.

Furthermore, the second invention allows the above method to be carried out smoothly, and also provides an apparatus configuration i-. [Means for solving the problem] In order to achieve the object h, the injection molding method of the first invention has the following features:
In a method of injection molding a molding material, there is a method in which molding is performed while causing a mold to resonate at n wavelength (n-m/2m; positive integer) using ultrasonic waves. In a preferred embodiment, in order to use the ultrasonic vibration effect to most efficiently reduce the contact resistance between the injected material and the mold wall surface, the resonance position of the ultrasonic waves should match the position of the mold gap. In order to resonate and/or prevent ultrasonic vibrations from being transmitted to the outside of the mold, the nodes of ultrasonic resonance are aligned with the positions of the fixed mold holder and the movable mold holder. There is a way to make it resonate so that it does. In addition, in another preferred embodiment, in order to suppress the dimensional shrinkage of the molded product and improve the dimensional accuracy by using the stress effect of the a-D wave (resonant node), the resonance node due to the super-1'f wave can be suppressed. The fixed mold holder and the movable mold holder are designed to resonate so as to match the position of the mold cavity, and/or to prevent TFL sonic vibrations from being transmitted to the outside of the mold. There is a method of making the ultrasonic waves resonate so that each position matches the resonance of the ultrasonic waves.

Furthermore, in the injection molding apparatus of the second invention, the molding material from the molding machine is supplied to the cavity of the mold through the sublue of the fixed mold, and in the apparatus for performing injection molding, the fixed mold and the movable mold are is held by a fixed jig, and a supermultiplexer is coupled to the mold surface opposite to the cavity side of the movable side mold. Preferably, the fixed side mold and the movable side mold are held together by a fixed jig. The mold is held in a holding structure using line contact. [Example] A specific example of the above solution will be described below. First, a specific example of an injection molding apparatus will be explained based on FIG. In the figure, a mold 1 is divided into a +'lf moving side mold 2 and a stationary side mold 3. And the movable side metal 52
A cavity 2a is provided on the contact surface with the stationary side mold 3, and a sprue 33 is provided at a position of the stationary side mold 3 corresponding to the cavity 2a. The mold l can be made of metal, ceramics, graphite, etc., or it can be made of a material that has low transmission loss of ultrasonic waves and is less fatigued even when the amplitude of ultrasonic vibrations is increased, such as titanium alloy. It is preferable to use duralumin or the like. Furthermore, the surface of the mold 1 may be subjected to treatments such as plating or graining. Furthermore, the mold l is divided into three or more pieces, 13
In this case, it is preferable that the dividing surface be located as close as possible to the resonance region of the ultrasonic waves in order to improve the transmission of the ultrasonic vibrations.

In addition, regarding mold temperature control and molded product ejection methods, please refer to
Although known methods can be used, it is preferable that the joint attached to the mold for introducing or discharging the mold warming medium into the mold is installed near the joint. In addition, if the ejector bottle is used as part of the mold,
The clearance between the protruding bottle and the hole for removing it is adjusted to the state before ejecting. ! 4 is a nozzle of a molding machine (not shown), and it is preferable that the position of the part in
The molding material is injected and supplied to the cavity 2a through the. The contact surface of the sprue 3a with the nozzle 4 is located at approximately the location (described later) of the ultrasonic vibration (displacement waveform) in the stationary mold 3. Reference numeral 5 denotes a first holding member (mold clamping member), which is supported by a cylinder 6 so as to be movable forward and backward, and a fixing plate 7 serving as a fixing jig is attached to the tip thereof. This fixed plate 7 holds the outer periphery of the movable mold 2 at approximately the center thereof. The movable mold 2 is held by the fixed plate 7 by grooves 2b on the outer periphery of the movable mold 2.
This is done by providing a groove 2b and bringing the tapered end 7a of the fixing plate 7 into contact with this groove 2b. Therefore, in this case, the movable mold 2 is held by the fixed plate 7 through line contact, and the contact area between the movable mold 2 and the fixed plate 7 becomes extremely small. This makes it possible to minimize the external leakage of mold vibrations. A second holding member 8 is fixed to the outside of the cylinder 6, and a fixing plate 9 serving as a fixing jig is attached to the tip thereof. This fixed plate 9 is a fixed side metal. ! ! ! 3, and in this case, the movable mold 2
In order to suppress the vibrations of the stationary die 3 from flowing out, the groove 3b of the stationary die 3 and the tapered tip 9a of the stationary plate 9 are held in a line contact state.

As a method of holding the mold l, it is preferable to use a holding member having a small contact area to hold the nodes of ultrasonic resonance as in this embodiment.

Reference numeral 10 denotes a vibrator, the tip of which is connected to the mold surface of the moving side mold 2 on the side opposite to the cavity 2a, and is connected by a mounting member 11 such as a screw. l2 is a super single-wave oscillator, which generates Jj3tf wave vibration in the vibrator 10, and
(Movable mold 2, fixed mold 3) are excited and resonated. This resonant frequency is designed and manufactured to a frequency that can be tracked by the ultrasonic oscillator, so the nozzle 4 of the molding machine
is pressed against the sprue 3'a, and the molding material is applied to the sprue 33.
When supplying power to the cavity 2a via the resonant frequency, changes in the resonant frequency due to momentary load fluctuations are constantly tracked, and the required power is also adjusted according to the momentary changes.
It is set to supply a high output (fi output or less). Next, a specific example of the first invention of the injection molding method carried out using the injection molding apparatus described in 1 and 2 will be described.

The nozzle 4 of a molding machine (not shown) is pressed against the sprue 33 of the stationary mold 3, and the cavity 2 is inserted through this sprue 38.
A is injected with a molding material, and the ultrasonic oscillator 12 causes the vibrator 10 to generate llfl sonic vibrations, thereby causing the mold 1 to resonate at n wavelengths. The timing for generating ultrasonic vibrations can be selected depending on the desired effect.

The vibration frequencies at this time are IKII7 to IOMII. In order to make the ultrasonic wave act extremely effectively on the material during binding and molding, 1. OK Kl+. ~l O O Kll,l
Let the frequency be . jfl The larger the amplitude of the K-wave vibration, the more effective it will be, but it is preferable to set it in accordance with the fatigue level of the material of the mold 1.

Also, n in n-wavelength resonance is . m/2 (m is a positive integer a
) (Figure 2), in order to match the resonance t part (the point where the displacement waveforms intersect and are not vibrating) with the mold fixing part and the contact part of the nozzle, it is necessary to It is preferable that n<3, which is a small number.

Furthermore, even in the case of n<3, the resonance fr! Part a (
The farthest part of the displacement waveform (the point that vibrates most strongly) coincides with the vibration vibration 2a, and the vibration effect of the super 1゛f wave is made to be used as effectively as possible. This will improve the flow of the molding material.

Next, a specific example of the injection molding method according to claim 3 will be explained.

This injection molding method differs from the injection molding method described above in that the cavity 2 is aligned with the node of resonance caused by the ag wave. If this is done, the dimensional shrinkage of the molded product will decrease by Z due to the stress effect of the ultrasonic waves.

Molding materials that can be molded by the above-mentioned injection molding method and apparatus include organic materials for plastic hats, inorganic polymers, ceramics, metals, etc. Examples include materials that have good fluidity during molding, such as inorganic materials such as glass, other foodstuffs, and mixed materials thereof.

In addition, the injection molding method in the present invention includes a multicolor molding method, an injection compression molding method, etc. Furthermore, the molding material 4 in a fluid state or rubber-like state is press-fitted into a mold and formed into a predetermined shape. This category includes all molding methods that involve taking out the molded product after shaping it.

[Experimental Example] Hereinafter, the results of an experiment conducted using the injection molding method and apparatus of the present invention will be explained while comparing with a comparative example.

Experimental Example 1 Injection Molding Neck Equipment shown in Figure 1 Molding material: Polyethylene (Idemitsu Petrochemical Co., Ltd. 6400F) SONOPET 12001{) Injection molding was performed under the conditions listed in L while making the mold resonate, and the flow at that time was I asked for the length.

The flow length was evaluated by determining the length of the resin flowing into a groove-shaped cavity with a wall thickness of 0.5 mm by determining Δ1l1 and equalizing the resin 10 times.

The results are shown in Table 1. Comparative Example 1 An experiment was conducted under the same conditions as Experimental Example 1, except that the mold was not caused to resonate by ultrasonic waves. Comparative Example 2 An experiment was conducted under the same conditions as Comparative Example 1 by heating the mold to 200°C using an external wire heater. This example:
This method is considered to be equivalent to the conventional method in which molding is performed by raising the mold surface temperature using a high-frequency induction heating device. Comparative Example 3 As shown in FIG. 6, an experiment was conducted under the same rotating conditions as in Experimental Example 1, except that the vibrator IO was positioned at the contact area between the movable mold 2 and the stationary mold 3. At this time, the mold was not in a resonant state. The results of Comparative Examples 1 to 3 are shown in Table 1. Table 1 1) The values in parentheses are the standard deviations.Result 2According to the present invention, the deviation is much greater than when ultrasonic waves are not applied, as well as when ultrasonic waves are simply applied or when the mold is heated. It was found that the fIt dynamics of the molding material improved.

Experimental Example 2 Injection molding equipment: The equipment is the same as that shown in Figure 1, except that the fixed mold and movable mold are slightly longer. An experiment was conducted under the same rotating conditions as in Experimental Example 2, except that the mold was not caused to resonate by ultrasonic waves. The experiment was conducted under the same conditions as in Experimental Example 2, except that the oscillator lO was placed in the contact area between the movable mold 2 and the fixed mold 3 (see Figure 6). Table 2 shows the results of Comparative Examples 4 and 5. Table 2 Under the above conditions, injection molding was performed while the mold was made to resonate, and the diameter of the molded product at that time was determined to be 3III.

Evaluation was performed using the average value of 10 molded products.

The results are shown in Table 2. As a result, according to the present invention, ultra-RF waves are applied. It has been demonstrated that it is possible to obtain a molded product with significantly smaller dimensional shrinkage than when ultra-B waves are applied during the process, as well as when it is not used.

Experimental Example 3 The load current of the ultrasonic oscillator was measured when the molds were held in line contact and the molding of Experimental Example 1 was carried out.

The results are shown in Table 3.

Wataru Noshiki: The shape of the grooves in the movable mold and the fixed mold hold the mold. Dimensions and turning shape. The experiment was conducted under the same conditions as Experimental Example 3, except that a fixing plate with the same dimensions was used.
In this case, the fixed plate is in surface contact with the mold. The results are shown in Table 3. Table 3 Load? I! In Comparative Example 6 (contact), where the flow was high, it was clear that the flow was due to vibration or through the fixed plate. As a result, it was found that holding the mold by &a contact is very effective.

[Effects of the Invention] As described above, according to the injection molding method of the first invention, vibrations can be efficiently transmitted by causing the mold to resonate with ultrasonic vibrations. Furthermore, by maximizing the vibration effect of ultrasonic waves, it is possible to improve the fluidity of molding materials, which is difficult to do with conventional molding techniques, such as composite materials in which large amounts of high-molecular-weight plastics and fillers are incorporated. Easy to mold.

Furthermore, by making the mold resonate with a-sonic vibrations, vibrations can be transmitted efficiently and the stress effect of ultra-11 waves can be utilized, so the molded product can be made more easily than when simply applying TFL@ waves to the mold.・T-method shrinkage can be significantly reduced. According to the injection molding equipment of the second invention, it is possible to improve the fluidity of the molding material, mold products with excellent physical properties and dimensional accuracy, and minimize the outflow of mold vibrations. This has the effect of not adversely affecting other parts of the device.

[Brief explanation of the drawing]

FIG. 1 shows the main parts of an example of the injection molding apparatus of the present invention.
r side view, Figures 2 and 3 are explanatory diagrams of the displacement waveform and wavelength during mold resonance in the first invention, Figure 4 is an explanatory diagram of the cavity used in the molding experiment of the first invention, and Figure 5 is the experiment. Explanatory diagram of resonance conditions in the molding experiment of Example 1, No. 6I2
l is a schematic diagram of an example of a device other than the present invention using an ultrasonic transducer;
Figure 7 is an explanatory diagram of the cavity used in the molding experiment of Experimental Example 2, and Figure 8 is a diagram illustrating the resonance conditions in the molding experiment of Experimental Example 2. 1 Metal 5 2 Movable side mold 3: Fixed side mold 2a. Cavity 2b, 3b: Groove 3a, Sprue 7, 9, Fixing Jig 10: @Movement Figure 2 n Knees Figure 3 n

Claims (6)

[Claims] (1) An injection molding method for injection molding a molding material, characterized in that molding is performed while causing a mold to resonate at n wavelengths (n=m/2m; positive integer) using ultrasonic waves. (2) The injection molding method according to claim 1, characterized in that the molding is performed while resonating so that the resonance region of the ultrasonic waves coincides with the position of the cavity of the mold. (3) The injection molding method according to claim 1, characterized in that the molding is performed while resonating so that the node of resonance caused by the ultrasonic waves coincides with the position of the cavity of the mold. (4) The first aspect of the present invention is characterized in that molding is performed while resonating so that the nodes of resonance caused by ultrasonic waves coincide with the positions of the stationary mold holder and the movable mold holder.
The injection molding method according to item 2 or 3. (5) In a device that performs injection molding by supplying molding material from a molding machine to a mold cavity through a sprue of a fixed mold, the fixed mold and movable mold are held by a fixing jig. An injection molding apparatus characterized in that an ultrasonic vibrator is coupled to the mold surface of the movable mold on the side opposite to the cavity side. (6) The injection molding apparatus according to claim 5, wherein the fixed mold and the movable mold are held by the fixing jig through line contact.