JP2984693B2 - Injection molding method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an injection molding method for a molding material, and more particularly, to a method in which a mold is resonated by vibrating means at the time of pressure holding and / or release from an injection molding cycle. The present invention relates to an injection molding method in which the releasability of a molded product is improved.

[Prior Art] In general, in injection molding, there is a process in which after molding is performed by filling a mold with a molding material, a molded product is removed from the mold using a protruding pin or the like. However, the release of the molded product from the mold is difficult because the molded product is easily adhered to the cavity surface. If so, mold release failure often occurs.

Therefore, to improve the smoothness of the mold surface than before,
Alternatively, a mold release agent is applied to the surface of the mold to facilitate the release.

However, in the former case, when the structure of the mold is complicated, it is very difficult to smooth the mold surface. In the latter case, there is a problem that it is necessary to remove the release agent, which is disadvantageous in terms of economy.

In addition, in general injection molding, distortion occurs in the molded product due to the flow orientation that occurs when the molding material is filled into the mold and the uneven cooling of the molded product after filling, and the distortion causes the molded product to deform. May occur and the releasability may decrease. In this case, if the molded product is forcibly released from the mold by strongly pressing the protruding pin, the portion of the molded product where the protruding pin abuts is undesirably distorted.

Therefore, in order to prevent this flow orientation and uneven cooling,
Although various measures have been taken to improve the gate, sprue or runner of the mold, or to improve the temperature control of the mold, they have not sufficiently improved the releasability.

Therefore, several methods have been proposed for improving the releasability of a molded product by using ultrasonic vibration or the like. For example, in Japanese Patent Application Laid-Open No. 54-46262, a release method in which ultrasonic vibration is applied to a molding die of a polymer molded product to release the molded product is disclosed. Continuously,
Alternatively, there has been proposed a device in which a mold is intermittently vibrated by ultrasonic vibration or the like at the time of injection filling, at the time of release, or the like, so as to improve the releasability of a molded product.

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

That is, the technology proposed in Japanese Patent Application Laid-Open Nos. 54-46262 and 1-182016 discloses that ultrasonic vibration is transmitted to the outside of the mold, which adversely affects the mold itself and other parts of the apparatus. There's a problem. Furthermore, since the material and the horn are in direct contact, a large load is applied to the horn and the ultrasonic oscillator, and there is a problem that ultrasonic vibration cannot be sufficiently applied to the material.

Furthermore, simply applying ultrasonic vibration to the mold,
There is a problem that the ultrasonic vibration cannot be efficiently transmitted to the material, and thus the releasability is not sufficient.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection molding method in which the releasability of a molded product is improved.

The present inventors have conducted intensive studies to achieve the above object, and as a result, during the pressure holding and / or the release from the injection molding cycle, the mold is resonated by the vibration means, so that the ultrasonic vibration is simply applied to the mold. As a result, the present inventors have found that the releasability of a molded article can be significantly improved without causing the above-described inconvenience due to the application of the ultrasonic vibration, as compared with the case of applying.

[Means for Solving the Problems] The injection molding method of the present invention relates to a method for performing injection molding of a molding material, wherein the molding is performed while causing the mold to resonate by vibration during pressure holding and / or release from the injection molding cycle. There is a way to do it. And, as a preferred embodiment, by the vibration effect, the frictional heat between the injected material and the mold wall surface, etc.
In order to efficiently and instantaneously reheat the material near the contact surface and relieve the strain generated during the material injection / filling process at the contact surface, the abdomen of the ultrasonic resonance is adjusted to the position of the mold cavity. To resonate to match and / or to prevent ultrasonic vibrations from transmitting outside the mold,
This is a method of resonating so that nodes of resonance by ultrasonic waves coincide with the positions of the fixed mold holding unit and the movable mold holding unit.

Another preferred embodiment is a method of causing the movable mold to resonate at the time of mold release in order to accelerate the mold release of the molded product by vibration.

[Example] An example of the above-mentioned solving means will be described below.

First, an embodiment of the injection molding apparatus will be described with reference to FIG.

In the figure, reference numeral 1 denotes a mold, which is divided into a movable mold 2 and a fixed mold 3. A cavity 2a is provided on the contact surface of the movable mold 2 with the fixed mold 3, and a sprue 3a is provided on the position of the fixed mold 3 corresponding to the cavity 2a.
Is provided. The mold 1 can be made of metal, ceramics, graphite, etc., but has a small transmission loss of ultrasonic waves, and a material that does not cause fatigue even when the amplitude of ultrasonic vibration is increased, for example, titanium alloy, K-monel. ,Phosphor bronze,
It is preferable to use duralumin or the like.

Further, the surface of the mold 1 may be subjected to a treatment such as plating or graining. Further, the mold 1 can be divided into three or more parts. In this case, in order to improve the transmission of the ultrasonic vibration, the division surface is located as close to the antinode of the ultrasonic resonance as possible. Preferably.

Further, the mold 1 has a L-
A vibration direction converter such as an L converter, an LR converter, and an LLL converter may be provided.

In addition, as for the method of controlling the temperature of the mold and the method of projecting the molded product, a known method can be used, but a joint attached to the mold to introduce or discharge the medium for controlling the temperature of the mold is not provided. , Preferably near the node. Also, when providing the protruding pin 2c in the mold, the clearance between the protruding pin 2c and the hole through which the protruding pin 2c passes,
It is preferable to set the minimum value at the position of the node in the state before the protrusion. Further, it is preferable to apply a surface coating to the surface of the protruding pin 2c to improve the slip. The projecting pin 2c is reciprocated by the projecting device 13.

Reference numeral 4 denotes a nozzle of a molding machine (not shown), and a sprue 3a
The molding material is injected and supplied to the cavity 2a via the. The contact surface of the sprue 3a with the nozzle 4 is positioned substantially at a node (described later) of the ultrasonic vibration (displacement waveform) in the fixed mold 3 so that the vibration applied to the mold 1 is not transmitted to the molding machine. It is.

Reference numeral 5 denotes a first holding member (clamping member) which is supported by a cylinder 6 so as to be able to advance and retreat, and a fixing plate 7 serving as a fixing jig is attached to a front end thereof. The fixed plate 7 holds a substantially central outer periphery of the movable mold 2. The holding of the movable-side mold 2 by the fixed plate 7 is performed by using a groove 2 b
And the tapered tip 7a of the fixing plate 7 is provided in the groove 2b.
This is done by contacting Accordingly, in this case, the movable mold 2 is held by the fixed plate 7 in a line contact state, and the contact area between the movable mold 2 and the fixed plate 7 is extremely small. Thereby, the outflow of the vibration of the mold to the outside can be minimized.

Reference numeral 8 denotes a second holding member fixed to the outside of the cylinder 6, and a fixing plate 9 serving as a fixing jig is attached to the tip of the second holding member. The fixed plate 9 holds the outer periphery at substantially the center of the fixed mold 3, and in this case, similarly to the holding of the movable mold 2, the vibration of the fixed mold 3 is prevented from flowing out to the outside. The groove 3b of the fixed mold 3 and the tapered tip 9a of the fixed plate 9
Is held by contact of

As a method for holding the mold 1, as in this embodiment, it is preferable to hold the node of the resonance by the ultrasonic wave using a holding member having a contact area as small as possible.

Reference numeral 10 denotes a vibrator for applying vibration to the mold 1, the tip of which abuts against the mold surface of the movable mold 2 on the side opposite to the cavity 2 a, and is connected by a mounting member 11 such as a screw. Frequency as the vibration can be used vibrations 10H _z ~10MH _z. Among these frequencies, the effect of vibration can be obtained in a short time, and in order to suppress excessive heat generation of the molding material,
Frequency of 10KH _z ~100KH _z is preferable.

Further, as the vibration generating device, the above-described vibrator, electro-mechanical shaker, mechanical shaker, electro-hydraulic shaker, or the like can be used.

Reference numeral 12 denotes an ultrasonic oscillator that generates ultrasonic vibrations in the vibrator 10 to excite the mold 1 (the movable mold 2 and the fixed mold 3) to resonate.

The resonance frequencies of the movable mold 2 and the fixed mold 3 are designed in advance to frequencies that can be tracked by the ultrasonic oscillator.
Since it is manufactured, the nozzle 4 of the molding machine is brought into pressure contact with the sprue 3a, and the molding material is transferred to the cavity 2a through the sprue 3a.
From the time of injection and filling to the time when the mold is opened, the molded product attached to the movable mold 2 is protruded, and the mold is released by the pin 2c. In addition, the supply of necessary power is set so as to supply a required amount (less than the maximum output) in accordance with an instantaneous change.

The ultrasonic vibration modes include longitudinal vibration,
Known vibration modes such as lateral vibration, torsional vibration, radial vibration, and flexural vibration can be used.

Next, a first embodiment of an injection molding method performed by using the above-described injection molding apparatus will be described.

The nozzle 4 of the molding machine (not shown) is pressed against the sprue 3a of the fixed mold 3, and the molding material is injected and filled into the cavity 2a via the sprue 3a.
12 causes the vibrator 10 to generate ultrasonic vibration, thereby causing the mold 1 to resonate for n wavelengths by longitudinal vibration. here,
The dwell time refers to the time from the end of injection to the time before the molded product is released. The resonance time can be appropriately selected within the dwell time. The time at which the ultrasonic vibration is generated can be selected according to the desired effect.

The greater the amplitude of the ultrasonic vibration, the better the effect can be exhibited, but it is preferable to set it according to the fatigue strength of the material of the mold 1.

When the mold 1 is caused to resonate for n wavelengths, n in the n-wavelength resonance is m / 2 (m is a positive integer). In order to match the non-vibrating point at the intersection of the displacement waveforms,
It is preferable that n <3, which has as few nodes as possible.

Further, even in the case of n <3, the antinode of resonance (the point where the displacement waveform is farthest and vibrates most strongly)
Resonate with the cavity 2a so that the vibration effect of the ultrasonic wave can be used most effectively. This way,
The material near the contact surface is efficiently and instantaneously reheated by frictional heat between the material injected into the mold 1 and the mold wall surface, and the strain generated during the material injection / filling process at the contact surface is reduced. By doing so, the releasability of the molded article becomes good.

 Next, a second embodiment of the injection molding method will be described.

This injection molding method, at the time of mold release in the injection molding cycle,
Only the movable mold 2 resonates to improve the releasability of the molded product. After the molded product is cooled in the mold, the movable mold is retracted to open the mold, and the vibration is reduced. Simultaneously with the application to resonate, the molded product is projected by the ejection device 13.

Examples of the molding material that can be molded by the above-described injection molding method include organic materials such as plastics, rubbers, and elastomers, inorganic materials such as inorganic polymers, ceramics, metals, and glasses, and other foodstuffs and their mixed materials. Materials having some fluidity may be mentioned.

Here, the following can be mentioned as the plastic.

Α-olefin resins (polyethylene, polypropylene, polystyrene, syndiotactic polystyrene,
Polyvinyl chloride resin, polybutene, ultra-high molecular weight polyethylene, polymethylpentene, ionomer, polybutylene, etc.) Polyester resin (polyethylene terephthalate,
Polybutylene terephthalate, polyarylate, etc.) Polyether resins (polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyallylsulfone, polyoxybenzylene, polyphenylene oxide, polycyanoallylether [Japanese Patent Application Laid-Open No. Sho 62] -223226] etc.) Polycarbonate resin Polyimide resin Polyamide resin Polyamide imide resin Methacryl resin Fluoro resin MBS (methacrylate butadiene styrene) resin AAS (acrylate acrylonitrile styrene) resin AS (acrylonitrile styrene) resin ACS (chlorinated acrylonitrile polyethylene styrene) ) Resin ABS (acrylonitrile butadiene styrene) resin Polyacetal resin Cellulose resin Polyvinylidene chloride Chlorinated polyethylene EVA (ethylene vinyl acetate) resin Polyurethane resin Silicone resin Allyl resin Furan resin Liquid crystal polymer etc. Thermosetting resin Epoxy resin Phenol resin Polybutadiene resin Silicone resin Unsaturated polyester resin Amino resin etc. Styrene-butadiene as thermoplastic elastomer Based elastomers Polyester based elastomers Polyethylene based elastomers Urethane based elastomers Vinyl chloride based elastomers etc.

The injection molding in the present invention includes multicolor molding, injection compression molding, insert molding, outsert molding, injection foam molding, reaction injection molding, mixed color injection molding, magnetic field injection molding, and the like. This includes all molding methods that employ a method in which a molding material in a rubber-like state is pressed into a mold, shaped into a predetermined shape, and then a molded product is taken out.

By this method, home electric parts, automobile parts, communication equipment parts, information recording equipment parts, daily miscellaneous goods, power generation equipment parts, optical parts and the like can be formed.

[Experimental Examples] Hereinafter, experimental results performed using the injection molding method of the present invention will be described in comparison with comparative examples.

Experimental Example 1 Injection molding device: device shown in Fig. 1 Molding material: polystyrene (HF10 manufactured by Idemitsu Petrochemical Co., Ltd.) Die: 60 mm x 60 mm prismatic shape, material S45C Inner diameter 20 mm, wall thickness 1 mm and depth 20 mm forming a cup-shaped cavity (FIG. 2) ultrasonic generator: the fundamental frequency 19.15KH _z (Seidensha electronic industry Co., Ltd. SONOPET 1200-B) molding conditions: clamping force 3.5 (ton) injection pressure 940 (Kg / cm ₂ ) Resin temperature 210 (° C) Amplitude 10 μm Resonance The mold was a one-wavelength resonator (No. 3
Figure) Under the above conditions, injection molding is performed while resonating the mold at the time of holding the pressure in the injection molding cycle, the protrusion pressure at the time of mold release of the molded product is obtained, and the inner diameter of the tip of the molded product at the opening side is determined. It was measured.

 Table 1 shows the results.

Comparative Example 1 An experiment was performed under the same conditions as in Experimental Example 1, except that the mold was not resonated by ultrasonic waves.

 Table 1 shows the results.

Experimental Example 2 An experiment was performed under the same conditions as in Experimental Example 1 except that injection molding was performed while resonating the mold only at the time of mold release in the injection molding cycle.

 Table 1 shows the results.

Experimental Example 3 An experiment was performed under the same conditions as in Experimental Example 1 except that the injection molding was performed while the mold was resonated during the pressure holding and the mold release during the injection molding cycle.

 Table 1 shows the results.

Comparative Example 2 An experiment was performed under the same conditions as in Experimental Example 1 except that injection molding was performed while applying ultrasonic waves to the mold only under mold release during the injection molding cycle under conditions that do not resonate the mold. .

 Table 1 shows the results.

As a result, according to the present invention, at the time of pressure holding or release from the injection molding cycle, by resonating the mold with ultrasonic waves, compared with a case in which ultrasonic waves are not applied in the same case,
It can be seen that the release of the molded product is much easier. Also,
It can be seen that the resilience of the mold during both the pressure holding and the mold release further improves the releasability compared to the case where the mold is resonated alone.

In addition, from the comparison result of the inner diameter of the tip portion on the open port side of the molded product, if the mold does not resonate with the ultrasonic wave at the time of holding the pressure, the residual strain tends to remain, the molded product shrinks, and the releasability deteriorates. You can see that.

[Effects of the Invention] As described above, according to the injection molding method of the present invention, when the pressure is maintained during the injection molding cycle, the mold is resonated by the ultrasonic waves, thereby reducing the distortion of the molded product, and thus the molding is performed. It is possible to suppress the deformation of the product and improve the releasability of the molded product.

In addition, at the time of mold release in the injection molding cycle, the mold is resonated by ultrasonic waves, so that the mold releasability of the molded product can be improved.

[Brief description of the drawings]

FIG. 1 is a cutaway side view showing an embodiment of an injection molding apparatus for carrying out an injection molding method according to the present invention, and FIGS. 2 (a) and (b) are plan views showing an embodiment of a cavity. FIG. 3, a side view, and FIG. 3 are explanatory diagrams of a displacement waveform and a wavelength at the time of mold resonance. 1: mold, 2: movable mold 3: fixed mold, 2a: cavity 2b, 3b: groove, 3a: sprue 7,9: fixing jig, 10: vibrator 13: projecting device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Nakajima 2-9-1-13 Torigoe, Taito-ku, Tokyo Inside Seidensha Electronics Co., Ltd. (72) Inventor Noriaki Matsugishi 2-9-1 Torigoe, Taito-ku, Tokyo No. 13 Seidensha Electronics Co., Ltd. (56) References JP-A-2-131909 (JP, A) JP-A-3-217223 (JP, A) JP-A-63-135334 (JP, A) JP JP-A-62-135333 (JP, A) JP-A-52-92269 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. A method for injection-molding a molding material, characterized in that a mold is resonated by vibration during a pressure holding in an injection molding cycle. 2. A method for injection molding a molding material, wherein the mold is resonated by vibration at the time of release from the injection molding cycle. 3. The molding is performed while resonating so that nodes of resonance due to vibration coincide with the positions of the fixed mold holding unit and the movable mold holding unit. Injection molding method.