JPH03213318A - Injection molding method - Google Patents

Abstract

PURPOSE:To improve releasing properties of a molded product by carrying out molding while a mold is resonated by vibration at the dwelling time of injection molding cycle. CONSTITUTION:A node section of resonance generated by the supersonic waves of a mold 1 is retained by retaining components 7 and 9 with possible smallest contact area. A nozzle 4 of a molding machine is brought into contact with a sprue 3a of a movable side mold 3, and a molding material is injected and formed in a cavity 2a through said sprue 3a. Then, wave lengths (n) are resonated by vibrating vertically the mold 1 by means of the generation of supersonic vibration in a vibrator 10 by a supersonic oscillator 12. At that time, resonance is generated in a manner that a loop section of resonance conformes with the cavity 2a and that the supersonic vibration effect can be utilized to the machine. A material close to a contact surface is reheated efficiently and instantly by the friction heat or the like between a material injected into the mold 1 and a wall surface by said arrangement, and strain generated on the contact surface in the processes of injection and filling of the material is relaxed to make the release properties of a mold and the flow of molding material good.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection molding method for a molding material, and in particular, by making a mold resonate with a vibration means during pressure retention and/or mold release in an injection molding cycle. This invention relates to an injection molding method that improves mold release properties of molded products.

[Prior Art] In general, injection molding involves the process of filling a mold with a molding material to perform molding, and then ejecting the molded product from the mold using an ejector or the like. However, it is difficult to release the molded product from the mold smoothly because the molded product tends to adhere to the cavity surface, especially when the molded product has a large contact area with the cavity surface or has a complex shape. However, this often resulted in poor mold release.

Therefore, attempts have been made to facilitate mold release by improving the smoothness of the mold surface or applying a mold release agent to the mold surface.

However, in the case of the former, if the structure of the mold becomes complicated, it is very difficult to make the mold surface smooth. Moreover, in the latter case, there is a problem in that it is necessary to remove the mold release agent, which is disadvantageous from an economic point of view.

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. Deformation may occur and the mold releasability may deteriorate.

In this case, if an attempt is made to forcefully release the molded product by strongly pressing the ejector pin, distortion will occur in the portion of the molded product that comes into contact with the ejector pin, which is undesirable.

Therefore, in order to prevent this flow orientation and uneven cooling, the mold gate, sprue, runner, etc. should be improved.
Alternatively, attempts have been made to improve the temperature control of the mold, but none of these have been able to sufficiently improve mold release properties.

Therefore, several methods have been proposed to improve the releasability of molded products using ultrasonic vibration or the like.

For example, in JP-A No. 54-46262, there is a mold release method in which ultrasonic vibrations are applied to a mold for a polymer molded product to release the molded product, and in JP-A No. 1-182016, a mold release method is proposed. The mold is vibrated by ultrasonic vibration etc. continuously or intermittently during injection filling, demolding, etc.
There have been proposals for molded products with improved mold releasability, etc.

[Problem II that the Invention Attempts to Solve] However, the above-mentioned conventional molding method has the following problems.

That is, JP-A-54-46262, JP-A-1-18
The technique proposed in the 2016 issue has the problem of transmitting ultrasonic vibrations to the outside of the mold, which adversely affects the mold itself and other parts of the device. Furthermore, since the material and the horn are in direct contact with each other, a large load is placed on the horn and the ultrasonic oscillator 1, resulting in the problem that sufficient ultrasonic vibration cannot be applied to the material.

Furthermore, simply applying ultrasonic vibrations to the mold does not allow the ultrasonic vibrations to be efficiently transmitted to the material, resulting in the problem of insufficient mold releasability.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide an injection molding method that improves the releasability of molded products.

As a result of intensive research to achieve the above object, the present inventors have found that by simply causing the mold to resonate with vibration means during the pressure holding and/or release of the injection molding cycle, the mold is subjected to ultrasonic vibration. The present invention was completed based on the discovery that the releasability of a molded article can be significantly improved compared to the case where ultrasonic vibrations are applied without causing the disadvantages caused by the conventional ultrasonic vibration application described above.

[Means for Solving the Problems] The injection molding method of the present invention is a method for injection molding a molding material, in which molding is performed while making the mold resonate with vibration during pressure retention and/or mold release in an injection molding cycle. Here's how to do it. In a preferred embodiment, the material near the contact surface is efficiently and instantaneously reheated by the frictional heat between the injected material and the mold wall surface due to the vibration effect.
In order to alleviate the strain that occurs during the material injection and filling process on the contact surface, the abdomen of the resonance caused by ultrasonic waves or the resonance is made to match the position of the mold cavity.
<' J Shi Shaoyue beginning - In order to prevent desecration of the fan card, the nodes of resonance caused by ultrasonic waves are aligned with the positions of the fixed mold holder and the movable mold holder. This is a method of making it resonate so that it resonates.

Another preferred embodiment is a method in which the movable mold resonates during demolding in order to promote demolding of the molded product by vibration.

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

First, an embodiment of an injection molding apparatus will be described based on FIG.

In the figure, a mold 1 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 at a position of the fixed mold 3 corresponding to the cavity 2a. Mold 1 contains metal, ceramics,
Is it possible to use graphite or the like, reduce the transmission loss of ultrasonic waves, and increase the amplitude of ultrasonic vibrations to increase t1?
1 Benisa IT% Out of town? To H 1- ÷ l orgasm
・) For ΔV-Monel, phosphor bronze, duralumin, etc. are preferably used.

Furthermore, the surface of the mold l may be subjected to treatments such as plating and graining. Furthermore, it is also possible to divide the mold l into three or more pieces, in which case the dividing surface is located as close to the abdomen of ultrasound resonance as possible in order to improve the transmission of ultrasonic vibrations. It is preferable to do so.

Furthermore, the mold l has an L-L that changes the direction of vibration transmission.
A vibration direction converting body such as a converting body, an L-R converting body, an L-LL converting body, etc. can also be provided.

In addition, regarding mold temperature control and molded product ejection methods, please refer to
A joint attached to the mold for introducing or discharging the mold temperature regulating medium into the mold may be preferably installed near the joint, although known methods may be used. In addition, when the protruding bottle 2c is provided in the mold, the clearance between the protruding bottle 2c and the hole through which it passes is
It is preferable that the minimum value be set at the position of the node in the state before protrusion. In addition, it is preferable to apply a surface coach ink to the surface of the protruding bottle 2c to improve slippage.
Note that the ejection bottle 2c is reciprocated by the ejection device 13.

4 is a nozzle of a molding machine (not shown), and a sprue 3a
The molding material is injected and supplied to the cavity 2a through the. The contact surface of the sprue 38 with the nozzle 4 is located at approximately the node (described later) of the ultrasonic vibration (displacement waveform) in the stationary mold 3 so that the vibration applied to the mold l is not transmitted to the molding machine. 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.

The movable mold 2 is held by the fixed plate 7 by providing a groove 2b on the outer periphery of the movable mold 2 and bringing the tapered tip 7a of the fixed plate 7 into contact with this groove 2b. . In this case, the movable mold 2 by the fixed plate 7
is held by line contact, and the movable mold 2
The contact area between the fixed plate 7 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 made of a fixing jig is attached to the tip thereof. This fixed plate 9 holds the outer periphery of the fixed mold 3 at approximately the center, and in this case, similarly to the holding of the movable mold 2, the fixed plate 9 suppresses external vibration of the fixed mold 3. For,
Groove 3b of stationary mold 3 and tapered tip 9a of stationary plate 9
This is a holding state due to line contact caused by contact.

As for the method of holding the mold l, as in this embodiment, it is preferable to use a holding member having as small a contact area as possible, such as a node that resonates with ultrasonic waves.

Reference numeral 10 denotes a vibrator that applies vibrations to the mold l, and its tip abuts against the mold surface of the movable mold 2 on the side opposite to the cavity 2a, and screws and the like are connected by a member 11. .

As the vibration, it is possible to use a vibration with a frequency of 10cm2 to 10cm2. Among these frequencies, H! is set to 10 in order to obtain the vibration effect in a short period of time and to suppress excessive heat generation of the molding material. Frequency ultrasound of ~100 KH is preferred.

Further, as the vibration generator, the above-mentioned vibrator, electrodynamic vibrator, mechanical vibrator, electro-hydraulic vibrator, etc. can be used.

Reference numeral 12 denotes an ultrasonic oscillator that causes the vibrator 10 to generate ultrasonic vibrations, thereby exciting the mold 1 (movable mold 2 and fixed mold 3) to resonate.

The resonant frequencies of the movable mold 2 and the fixed mold 3 are designed and manufactured in advance to a frequency that can be tracked by the ultrasonic oscillator, so the nozzle 4 of the molding machine is brought into pressure contact with the sprue 38, and the molding material is released. Resonance frequency with respect to momentary load fluctuations from the time when the cavity 2a is injected and filled through the sprue 33 to the time when the mold is opened and the molded product attached to the movable mold 2 is ejected and released by the bin 2C. Changes in the output power are always tracked, and the required amount of power (less than the maximum output) is set to be supplied in accordance with the momentary changes.

Further, as the ultrasonic vibration mode, in addition to longitudinal vibration, known vibration modes such as transverse vibration, torsional vibration, radial vibration, and flexural vibration can be used.

Next, a first embodiment 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 sprue 3a is inserted into the mold.

After injecting and filling the molding material into the cavity 2a, the ultrasonic oscillator 12 generates ultrasonic vibrations in the vibrator lO during pressure retention, thereby causing the mold l to resonate at n wavelengths by longitudinal vibration. Here, the holding pressure time refers to the time before the molded product is released from under the injection eaves. Note that the resonance time can be appropriately selected within the pressure holding time. Furthermore, the timing for generating ultrasonic vibrations can be selected depending on the desired effect.

It is preferable that the amplitude of the ultrasonic vibration is set to be large enough to fully exhibit its effect, or to be set in accordance with the fatigue strength of the material of the gold 51.

In addition, when making the mold l resonate at n wavelengths, n in the n wavelength resonance is either m/2 (m is a positive integer), or there is a resonant node ( In order to match the non-vibrating points at the intersection of the displacement waveforms,
It is preferable to set n<3 so that the number of knots is as small as possible.

Furthermore, even if ξ is n < 3, the resonance belly (the point where the displacement waveform is farthest apart and vibrates most strongly),
It coincides with the cavity 2a, and resonates so that the vibration effect of the ultrasonic wave can be utilized as effectively as possible. In this way, due to frictional heat between the material injected into the mold l and the mold wall surface,
By efficiently and instantaneously reheating the material near the contact surface and alleviating the strain that occurs during the injection and filling process of the material at the contact surface, the releasability of the molded product and the tearing of the molding material are improved. .

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

This injection molding method improves the releasability of the molded product by making only the movable mold 2 resonate during mold release in two injection molding cycles.After cooling the molded product in the mold, the movable mold 2 With the mold retracted and opened, vibration is applied to cause resonance, and at the same time, the molded product is ejected by the ejector 3113.

Molding materials that can be molded by the injection molding method described above include organic materials such as plastics, rubber, and elastomers, inorganic polymers, and ceramics.

Inorganic materials such as metals and glass, other foodstuffs, and mixed materials thereof can be cited as materials that have the fluidity of clay during molding.

Here, examples of plastics include the following:

As thermoplastic resins, α-olefin resins (polyethylene, polypropylene, polystyrene, syndiotactic polystyrene, vinyl chloride resin, polyphthene, ultra-high molecular weight polyethylene, polymethylpentene, ionomer, polybutylene, etc.), polyethylene terephthalate, polyethylene allylate, etc.) Polyether resins (polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyallylsulfone, polyoxybenzylene, polyphenylene oxide, polycyanoallyl ether [JP-A-62-223226], etc.) ) Polycarbonate resin Polyimide resin Polyamide resin Polyamide-imide resin Methacrylic resin Fluorine resin MBS (methacrylate phthalodiene styrene) resin AAS (acrylate axolonitrile styrene) 4N resin AS (acrylonitrile styrene) M resin styrene) resin ABS (acrylonitrile styrene) ) Resin Polyacetal resin Cellulose resin Polyvinylidene chloride Chlorinated polyethylene EVA (Ethylene Vinyl polyurethane resin Silicone resin Allyl resin Furan resin Liquid crystalline polymer Epoxy resin Phenol resin Polyphtadiene resin Silicone resin Unsaturated polyester resin Amino resin (butadiene acetate) Styrene resin thermoplastic elastomer Styrene-phtadiene elastomer Polyester elastomer Polyethylene elastomer Urethane elastomer Vinyl chloride elastomer Nato.

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

By this method, home appliance parts, automobile parts.

We can mold communication equipment parts, information recording equipment parts, daily necessities, photoelectric equipment parts, optical parts, etc.

[Experimental Example] Hereinafter, the results of an experiment conducted using the injection molding method 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 making the mold resonate during pressure holding during the injection molding cycle, and the ejection pressure at the time of releasing the molded product was determined. The inner diameter of the tip on the open mouth side was measured.

The results are shown in Table 1.

Experimental example 1 except that the mold was not caused to resonate by ultrasonic waves.
An experiment was conducted under the following conditions.

The results are shown in Table 1.

Experimental Example 2 An experiment was conducted under the same conditions as Experimental Example 1, except that injection molding was performed while causing resonance only during mold release of the injection molding cycle.

The results are shown in Table 1.

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

The results are shown in Table 1.

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

The results are shown in Table 1.

[Hereinafter, blank spaces] Table 1 As a result, according to the present invention, by causing the mold to resonate with ultrasonic waves during pressure holding or mold release in an injection molding cycle, it is possible to avoid applying ultrasonic waves in similar cases. It can be seen that it is much easier to release the molded product. In addition, by making the mold resonate both during holding pressure and during mold release,
It can be seen that the mold releasability is further improved compared to when resonance is caused alone.

In addition, from the comparison results of the inner diameter of the tip on the open mouth side of the molded product, it is found that if the mold is not made to resonate with ultrasonic waves during pressure retention, residual strain tends to remain, causing the molded product to shrink and worsening mold releasability. I know.

[Effects of the Invention] As explained above, according to the injection molding method of the present invention,
By causing the mold to resonate with ultrasonic waves during pressure holding in the injection molding cycle, it is possible to reduce distortion of the molded product, thereby suppressing deformation of the molded product and improving mold releasability of the molded product.

Furthermore, by causing Venus to resonate with ultrasonic waves during mold release in the injection molding cycle, it is possible to improve the mold release properties of the f& shaped product.

[Brief explanation of drawings]

FIG. 1 is a cutaway side view of essential parts showing an embodiment of an injection molding apparatus for carrying out the injection molding method according to the present invention, and FIG.
a) and (b) are a plan view and a side view showing an example of a cavity, and FIG. 3 is a displacement waveform at the time of mold resonance.
FIG. 2 is an explanatory diagram of wavelengths. 1: Mold 2: Movable side mold 3: Fixed side mold 2a: Cavity 2b, 3b: Groove 3a Varnish blue, 9: Fixing jig 13: Ejection device: Vibrator

Claims (3)

[Claims] (1) An injection molding method for injection molding a molding material, characterized in that the mold is caused to resonate by vibration during pressure holding in an injection molding cycle. (2) An injection molding method for injection molding a molding material, characterized in that the mold is caused to resonate by vibration during mold release in an injection molding cycle. (3) The injection method according to claim 1 or 2, characterized in that the molding is performed while resonating so that the nodes of resonance due to vibration coincide with the positions of the stationary mold holder and the movable mold holder. Molding method.