JPH03213317A - Injection molding method and its device - Google Patents

Abstract

PURPOSE:To manufacture a molded product, the dimension shrinkage of which is extremely small compared with the shrinkage generated in the case of force feeding of a molding material into a cavity only by means of injection pressure by providing a resonance body resonating by the vibration of a mold and molding while resonating said body. CONSTITUTION:A supersonic oscillator 12 generates supersonic vibtation in a vibrator 10 and excites and resonates a movable side resonator 21 and a fixed side resonator 31. At that time, the resonators 21 and 31 are retained by using a fixed plate 7 with possible smallest contact area and retaining a node section of resonance by supersonic waves. A nozzle 4 of a molding machine is brought into contact with a sprue 3a of a fixed side mold 3, and a molding material is injected into a cavity 2a through said nozzle 3a to carry out molding, and a resonant section of the mold 1, a resonator, is resonated by wave length (n) by generating supersonic wave vibration (vertical vibration) in the vibrator 10 by means of the supersonic oscillator 12. Then, a loop section of resonance is conformed with the cavity 2a to carry out molding. The flow of the molding material in which supersonic vibration effect can be utilized to the maximum is made good.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to injection molding of molding materials such as polymeric materials.
The present invention relates to an injection molding method and apparatus that can mold a molded product with high physical properties and good appearance.

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

By the way, in recent years, with the progress of research on the physical properties of thermoplastic resins, the rigidity, heat resistance, and chemical resistance of molded products have been improved depending on the material (
It has become known that the molecular weight of the thermoplastic resin (thermoplastic resin) greatly affects the molecular weight.

However, the molecular weight of thermoplastic resins that can be molded using conventional injection molding methods is not so large, and is generally smaller than that of those commercialized as film grades. Therefore, there have been cases in which problems have arisen in that the physical properties of the molded product, such as rigidity, heat resistance, and chemical resistance, are inferior.

Therefore, from the perspective of improving physical properties, molding methods that improve the flow of resin during injection molding and enable the use of resins with high molecular weights constituting molded products have been considered, and several methods have been developed so far. For example,
The method of applying ultrasonic vibration to the gate part of the mold proposed in Japanese Patent Publication No. 57-2088, or the method proposed in Japanese Patent Publication No. 61
There is a method of inductively heating the mold surface using high frequency waves, as proposed in No. 44616.

On the other hand, when a polymeric material is used for injection molding, the polymeric material is filled into a mold in a heated state.

For this reason, it thermally expands when heated and contracts when cooled in the mold, so that only molded products smaller than the cavity size of the mold can be obtained.

Therefore, from the viewpoint of improving the dimensional accuracy of molded products, several proposals have been made to reduce the shrinkage of the material filled in the mold. For example, a method of molding by lowering the temperature of the material by significantly increasing the injection pressure and also increasing the mold clamping force, or JP-A-58-1
34722, a method in which the cavity is constructed with a horn for ultrasonic vibration, and the material is injected into the cavity and attempts to significantly reduce the non-uniformity of material temperature during the cooling process. etc.

[Problems to be Solved by the Invention] However, the conventional molding method described above has the following problems.

Namely, Special Publication No. 57-2088, #Kaikai No. 58-13
The technology proposed in No. 4722 has the problem that the structure of the mold is very complicated, that ultrasonic vibrations adversely affect the mold itself and other parts of the device, and that the material and horn are directly connected. Due to the contact structure, a large load is placed on the horn and vibration generating parts.1. There was a problem with not applying enough ultrasonic vibration to the material.

Further, as a result of experiments, it has been found that the fluidity of the resin does not improve as expected even when the surface of the mold is heated in the technique proposed in JP-A No. 61-44616.

Furthermore, the method of molding by lowering the mold clamping temperature of the material by significantly increasing the injection pressure and similarly high mold clamping force causes distortion in the molded product, causing it to deform when used as a product. There was a problem with how easy it was.

Therefore, the present inventors proposed in Japanese Patent Application No. 1-62196 a method and apparatus for injection molding while making the mold resonate, and showed that the above problems could be solved.

However, since the mold clamping part of the device proposed in Japanese Patent Application No. 1-62196 has a special structure, it is necessary to make major modifications to the injection molding machine when applying it to a conventional injection molding machine. there were.

The present invention has been made in view of the above circumstances, and allows the mold clamping part to be used as is without major modification even when applied to a conventional injection molding machine, and provides a molding method. The invention is an injection molding method that not only applies vibration to the mold, but also makes a part of the mold resonate to dramatically improve the fluidity of the material. By utilizing the stress effect of vibration where the molding material in contact with the resonator is attracted to the nodes (resonant nodes), dimensional shrinkage is reduced compared to when the molding material is injected into the cavity using only injection pressure. The purpose of this invention is to provide an injection molding method that allows extremely small molded products to be obtained.

Further, the invention of the molding apparatus aims to provide an injection molding apparatus that can smoothly carry out the above method, has a reasonable structure, and can be easily applied to a conventional injection molding machine.

[Means for Solving the Problems] In order to achieve the above object, the invention of an injection molding method provides a method for injection molding a molding material, in which a resonator that resonates by vibration is provided in the mold, and while making the resonator resonate. This is a method for performing molding.

In a preferred embodiment, in order to most efficiently reduce the contact resistance between the injected material and the mold wall surface using vibration effects, the resonance belly of the resonator is aligned with the position of the mold cavity. Pregnant women / l, 1. /l+
In order to prevent E'Anasu from being transmitted to the child's prison, the resonance node of the resonator is connected to the holding part of the resonating part of the stationary mold and the holding part of the resonating part of the movable mold. This is a method of resonating to match the respective positions.

In addition, as another preferred embodiment, in order to suppress dimensional shrinkage of the molded product and improve one-dimensional performance due to the stress effect of vibration (resonant nodes), the resonant nodes of the resonator are arranged in the mold. the resonant nodes of the resonator to make it resonate to match the position of the cavity and/or to prevent vibrations from being transmitted outside the mold.

This is a method of causing resonance to coincide with the positions of the holding part of the resonating part of the stationary mold and the holding part of the resonating part of the movable mold.

Further, in a preferred embodiment, the vibration in the above molding method is performed using ultrasonic waves.

On the other hand, in an invention of an apparatus for performing injection molding by supplying molding material from a molding machine to a cavity via a sprue of a mold, the mold is formed by a fixed mold and a movable mold, and A part of the stationary mold and the movable mold is provided with a part that resonates due to vibration, and this part is held by a fixing jig to the fixed mold and the movable mold, respectively.A preferable embodiment is as follows. The molding material from the molding machine is supplied to the cavity formed in the resonant part of the fixed mold through a sprue formed in the resonant part of the fixed mold, and preferably, the molding material is supplied to the cavity formed in the resonant part of the fixed mold. The configuration is such that a vibration generator is coupled to an arbitrary position of the resonator within the resonator, and more preferably, the resonant parts of the stationary mold and the movable mold are held by a fixing jig using a holding structure using line contact. It's Toshide.

[Example] Examples of the above solution will be described below.

First, a specific example of an injection molding apparatus will be described based on the first example.

In the figure, 1 is a mold, which is divided into a movable mold 2 and a fixed mold 3. A resonator (including a vibration direction converter) is provided inside the movable mold 2 and the fixed mold 3.
That is, a movable side resonator 21 and a fixed side resonator 31 are respectively provided.

Further, a cavity (sometimes referred to as a cavity including a runner) 2a is formed on the contact surface of the movable side resonator 21 with the fixed side resonator 31. Further, a sprue 3a is provided on the contact surface of the fixed side resonator 31 corresponding to the cavity 2a.

The resonator 21.31 is made of metal or ceramics.

Graphite or the like can be used, but it is preferable to use a material that causes less vibration transmission loss and is less fatigued even when the vibration amplitude is increased, such as titanium alloy, Monel, phosphor bronze, duralumin, or the like. Resonator 21.3
1 can also be provided with a mechanism such as an L-L converter, an L-R converter, an L-L-L converter, etc. for changing the vibration direction.

Furthermore, the surface of the mold l may be subjected to treatments such as plating and graining. Further, the mold 1 can be divided into three or more pieces, but in this case, it is preferable that the dividing plane be located as close to the resonance abdomen as possible in order to improve vibration transmission.

In addition, regarding mold temperature control and molded product ejection methods, please refer to
Known methods can be used. Regarding the temperature control of the mold, a hot runner system, which is a local heating method for the mold, and a high frequency induction heating method can also be used.

The joint attached to the mold for introducing or discharging the mold temperature control medium into the mold is preferably installed near the joint, and if an ejector pin is provided on the Venus, it should be installed near the ejector bottle. It is preferable that the clearance with the hole through which it is passed is set to a minimum value at the position of the knot in the state before protrusion.

4 is the nozzle of the molding machine (not shown), and the sprue 38
The molding material is injected and supplied to the cavity 2a through the. The contact surface between the sprue 38 and the nozzle 4 is the fixed side resonator 31 provided inside the fixed side mold 3! , : The vibration (displacement waveform) is located almost at the node (described later).

Reference numeral 5 denotes a movable side plate, which is connected to a movable side mold mounting board 51 that moves forward and backward through a cylinder 6. Further, reference numeral 8 denotes a stationary side plate, which is coupled to a stationary side mold mounting board 81.

The movable side resonator 21 is held in the movable mold 2 by a fixing plate 7 forming a fixing jig. That is, the movable resonator 21 is held by the fixed plate 7 by providing a groove 2b on the outer periphery of the movable resonator 21, and by bringing the tapered tip 7a of the fixed plate 7 into contact with this groove 2b. There is.

Therefore, in this case, the movable side resonator 2 due to the fixed plate 7
1 is held by line contact, and the contact area between the movable side resonator 21 and the fixed plate 7 becomes extremely small. This makes it possible to minimize the external leakage of the vibrations of the resonator 21.

Further, the fixed side resonator 31 is held in the same manner as described above by providing the groove 3b on the outer periphery of the fixed side resonator 31 and making the tip 9a of the fixed plate 9 tapered.

It is preferable to hold the resonator 21.31 using a holding member having a small contact area, such as a node of resonance caused by ultrasonic waves.

Is the vibration generated by a vibration generator?In this embodiment,
The vibrator 10 and the ultrasonic oscillator 12 constitute a vibration generator.

The vibrator IO is attached to the movable resonator 21 by a member 11. Note that an arbitrary number of the vibrators 10 can be attached to arbitrary positions of the movable side resonator 21 and/or the fixed side resonator 31 according to specifications.

The ultrasonic oscillator 12 causes the vibrator 10 to generate ultrasonic vibrations, and excites the movable side resonator 21 and the fixed side resonator 31 to resonate.

The resonance frequency is designed and manufactured to a frequency that can be tracked by the ultrasonic oscillator 12.The nozzle 4 of the molding machine is brought into pressure contact with the sprue 38, and the molding material is transferred to the sprue 3a.
When supplying power to the cavity 2a via the power source, the system constantly tracks changes in the resonant frequency due to momentary load fluctuations, and also adjusts the required amount of power (
maximum output).

Note that as the vibration, a vibration having a frequency of IOH, ~10 MH, can be used. Among these frequencies,
Ultrasonic waves of 10 KH to 100 KH are preferable because the vibration effect can be obtained in a short time and the excessive heat generation phenomenon of the molding material can be suppressed.

Further, the vibration generator has been described above. As an ultrasonic generator, an electrodynamic vibrator 1, a mechanical vibrator, etc. can be used.

Furthermore, the vibration modes include longitudinal vibration, which will be described later.
Known vibration modes such as transverse vibration, torsional vibration, radial vibration, and flexural vibration can be used.

Next, an example of an injection molding method performed using the above injection molding apparatus 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 molding material is injected into the cavity 2a through the sprue 33. 10 Ultrasonic vibration (longitudinal vibration)
By generating this, the resonant portion of the mold 1, that is, the resonator, is caused to resonate at n wavelengths. The timing for generating ultrasonic vibrations can be selected depending on the desired effect.

In the first embodiment of the injection molding method, molding is performed by aligning the resonance belly (the part of the displacement waveform farthest apart and the point vibrating most strongly) with the cavity 2a. In this way, the vibration effect of the ultrasonic waves can be utilized to the maximum extent possible, and the flow of the molding material can be improved.

Further, in the second embodiment, the molding is performed by aligning the resonance node (the point where the displacement waveforms intersect and are not vibrating) with the cavity 2a. In this way, the dimensional shrinkage of the molded product is significantly reduced due to the stress effect of the ultrasonic waves.

The vibration frequency when performing the above molding is l0 as described above.
It is preferable to set the frequency to KI (, ~100 Kl (, ). The larger the vibration amplitude, the more effective it will be, but it is preferable to set it in accordance with the fatigue strength of the material of the resonator.

In various vibration modes, the movable side resonator 21 and the fixed side resonator 31 are caused to resonate with n wavelengths in order to increase the vibration effect. In this n-wavelength resonance, n is m/2 (m is a positive integer), but in order to match the resonance nodes with the mold fixing part and the nozzle contact part, the number of nodes should be as small as possible. It is preferable that n<3.

In addition, even in the case of n<3, if the resonance abdomen is aligned with the cavity 2a and the vibration effect is made to resonate to the maximum extent possible, the flow of the molding material will be significantly improved as described above. .

When implementing the above-mentioned first and second embodiments, the position where the resonators 21 and 31 of the movable mold 2 and the fixed mold 3 are held in the movable mold and the fixed mold, respectively, and the vibration By aligning the resonance nodes and performing molding while resonating, transmission of vibration to the outside can be effectively prevented.

Molding materials that can be molded by the above-mentioned injection molding method and apparatus include organic materials such as plastics, rubber, and elastomers, inorganic materials such as inorganic polymers, ceramics, metal 1 glass, other foods, and mixed materials thereof. Examples include materials that have some fluidity during molding.

Here, examples of plastics include the following:

Thermosetting resins include α-olefin resins (polyethylene, polypropylene, polystyrene, syndiotactic polystyrene, vinyl chloride resin, polybutene, ultra-high molecular weight polyethylene, polymethylbenzone, ionomer, polybutylene, etc.), polyester resins (polyethylene terephthalate, polybutylene terephthalate, polyarylate, etc.) Polyether resins (polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyallylsulfone, polyoxybensylene, polyphenylene oxide, polycyanoallyl ether [
Polycarbonate resin Polyimide resin Polyamide resin Polyamideimide resin Methacrylic resin Fluorine resin MBS (Methacrylate Tutadiene Styrene) Resin AAS (Acrylate Acrylonitrile Styrene)
Resin AS (acrylonitrile styrene) Resin ACS (chlorinated acrylonitrile polyethylene styrene) Resin ABS (acrylonitrile butadiene styrene)
Resins Polyacetal resins Cellulose resins Polyvinylidene chloride Chlorinated polyethylene EVA (ethylene vinyl acetate) resins Polyurethane resins Silicone resins Allyl resins Furan resins Liquid crystalline polymers Epoxy resins Phenol resins Polybutadiene resins Silicone resins Unsaturated polyesters as thermosetting resins Amino resins, thermoplastic elastomers, styrene-butadiene elastomers, polyester elastomers, polyethylene elastomers, urethane elastomers, vinyl chloride elastomers, etc.

Injection molding in the present invention includes multicolor molding, insert molding, outsert molding, injection compression molding, injection foam molding, reaction injection molding, mixed color injection molding, etc.
This includes all molding methods in which a molding material in a fluid or rubber-like state is press-fitted into a mold, shaped into a predetermined shape, and then the molded product is taken out.

Injection molding in the present invention includes parts for home appliances,
Automotive parts 9 Communication equipment parts, information recording equipment parts 1
Daily necessities/miscellaneous goods 9 Parts for power generation equipment.

It can be used for molding optical parts, etc.

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

Experimental Example 1 Injection molding apparatus: The apparatus shown in FIG. 1 Under the above conditions, injection molding was performed while the resonator of the mold was made to resonate, and the flow length at that time (see FIG. 2) was determined.

The flow length was evaluated by measuring the length of the resin flowing into the cavity (including the runner) and using the average value of 10 measurements.

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 ultrasonic oscillation was stopped and the resonator of the mold was not caused to resonate.

Comparative Example 2 An experiment was conducted under the same conditions as Comparative Example 1 by heating the mold temperature to 200° C. using a far-infrared heater. This example is considered to be equivalent to the conventional example 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. 7, an experiment was conducted under the same conditions as in Experimental Example 1, except that the horn coupled with the vibrator IO was positioned on the sprue portion 3a. At this time, the mold was not in a resonant state.

Table 1 shows the results of Comparative Examples 1 to 3.

Table 1 Results 1 According to the present invention, the fluidity of the molding material is much higher than when ultrasonic waves are applied to a part of the sprue or when the mold is heated, as well as when no ultrasonic waves are applied. It turned out that things got better.

It has also been found that according to the present invention, carbon black is well dispersed in polyethylene.

Injection molding apparatus: This is the same as the apparatus shown in FIG. 1, except that the fixed mold and the movable mold are slightly longer.

Injection molding was performed under the above conditions while making the mold resonate, and the diameter of the molded product at that time was measured.

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

The results are shown in Table 2.

An experiment was conducted under the same conditions as Experimental Example 2, except that the resonator of the mold was not caused to resonate by ultrasonic waves.

An experiment was conducted under the same conditions as in Experimental Example 2, except that the horn to which the vibrator 10 was coupled was located in a part of the sprue (see FIG. 7).

The results of Comparative Examples 4 and 5 are shown in Table 2.

Table 2 As a result, according to the present invention, not only when no ultrasonic waves are applied, but also compared to when ultrasonic waves are simply applied.
It has been found that molded products with significantly small dimensional shrinkage can be obtained.

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

The results are shown in Table 3.

Experimental Example 4 The resonator was held using a fixing plate whose tip was not tapered. In this case, the fixed plate is in surface contact with the resonator.

The results are shown in Table 3.

Table 3 In Experimental Example 4 (surface contact) where the load current was high, it was clear that it was due to vibration or leakage through the fixed plate.

As a result, it was found that holding the resonator in the mold using line contact is very effective.

Experimental Example 5 Injection molding apparatus: The apparatus shown in FIG. 1. Molding was carried out under the above conditions while causing the resonator of the mold to resonate.

The weld part on the surface of the molded product has a dent (
xmm) was calculated.

The results are shown in Table 4.

Comparative Example 6 Molding was carried out under the same conditions as Experimental Example 5 except that the ultrasonic oscillation was stopped.

The results are shown in Table 4.

Experimental Example 6 Increase the number of ultrasonic transducers with an output of 200 W to two (Add one ultrasonic transducer to the lower surface of the L-L converter in Figure 1, that is, the surface opposite to the mounting position of the transducer 10) 1 oscillation The same experiment as in Experimental Example 4 was conducted by adjusting the timing.

The results are shown in Table 4.

Table 4 [Effects of the Invention] As described above, according to the invention of the injection molding method, vibrations can be efficiently transmitted by causing a part of the mold to resonate due to vibrations. It maximizes the vibration effect and improves the fluidity of the molding material, making it possible to mold composite materials containing large amounts of high-molecular weight plastics and fillers, which was difficult with conventional molding techniques, or in low-temperature ranges. This makes molding easier and reduces welt marks that occur on molded products.

In addition, by making a part of the mold resonate through vibration, the vibration can be transmitted efficiently and the stress effect of ultrasonic waves can be utilized, so the dimensions of the molded product can be improved compared to simply applying vibration to the mold. Shrinkage can be significantly reduced.

According to the invention of the injection molding device, 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 vibrations from resonant parts. This has the effect of not adversely affecting other parts of the device.

Moreover, since the mold clamping part of a conventional injection molding machine can be used, it can be easily applied to a conventional injection molding machine, and its utility value is very high.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view of the main parts of the injection molding apparatus used in Experimental Example 1, FIG. 2(a) is a plan view of the cavity used in Experimental Example 1, and FIG. 2(b) is an explanatory diagram of the flow length. Figure 3 is an explanatory diagram of the displacement waveform and wavelength when the resonator resonates, Figure 4 is an explanatory diagram of the cavity used in the molding experiment of Experimental Example 2, and Figure 5 is an explanatory diagram of the resonance conditions in the molding experiment of Experimental Example 2. Explanatory drawing, Fig. 6(a) is an explanatory drawing of the cavity used in the molding experiment of Experimental Example 5, Fig. 6(b) is an explanatory drawing of the welt part dent, Fig. 7
The figure shows a schematic view of the apparatus used in Comparative Examples 3 and 5. 1: Mold 21: Movable side resonator 3: Fixed side mold 2b, 3b: Groove 7.9: Fixing jig 2: Movable side mold 2a: Cavity 31: Fixed side resonator 3a Varnish blue lO: Vibrator

Claims (2)

[Claims] (1) An injection molding method for injection molding a molding material, characterized in that molding is performed while parts of the molds on the movable side and the fixed side are resonated by vibration. (2) The injection molding method according to claim 1, wherein the vibration is ultrasonic vibration. (3) In an apparatus that performs injection molding by supplying molding material from a molding machine to a cavity via a sprue of a mold, the mold is formed by a fixed side mold and a movable side mold, and these fixed side molds are An injection molding apparatus characterized in that a part of a mold and a movable mold is provided with a part that resonates due to vibration, and this part is held by a fixing jig to a fixed mold and a movable mold, respectively.