JP5795252B2 - Injection molding equipment - Google Patents

Description

  The present invention relates to an injection molding apparatus and an injection molding method effective when a resin, particularly a low-viscosity resin, is used as a molding material.

  As a means for injection molding of a liquid silicone resin, LIM (Liquid Injection Molding) molding has been generally known so far. In the field of impression materials, in recent years, PDMS (Poly Dimethyl Siloxane) has attracted attention as a highly accurate transfer silicone impression material. PDMS has characteristics such as excellent transferability of fine shapes, transparency and heat resistance, resistance to acids and alkalis, and excellent adhesion to glass. Furthermore, since it has the characteristic of low autofluorescence and non-toxicity to living organisms, it is widely used in microchannels and biochips, and is expected to expand further in the future. .

  This PDMS is characterized in that it is a low viscosity liquid silicone resin in terms of physical properties, and the lower limit of the viscosity of the resin used for LIM molding is 60 Pa · s (Pascal second). The upper limit of the viscosity of PDMS is as low as 20 Pa · s (Pascal second). Therefore, when performing injection molding using PDMS as a molding material, the physical property of extremely low viscosity poses a unique problem.

As a problem that becomes apparent when using a molding material having an extremely low viscosity, there is a problem of gas dissolution in the molding material.
It is known that gas is slightly dissolved in liquid. In the case of a liquid silicone resin, if the dissolved gas becomes obvious due to a pressure difference or temperature and becomes bubbles, it causes molding defects. Therefore, dissolution of the gas must be avoided as much as possible. In addition, it is known that the amount of gas dissolved by Henry's law increases in proportion to the pressure of the gas in a situation where pressure is applied to the gas / liquid for pumping.

  When supplying molding materials by pumping molding materials with gas such as air, dissolution of gas into molding materials exists as a general problem. However, when molding materials with high viscosity are used, molding is performed. Dissolution of the gas in the molding material does not pose a big problem, since an imbalance of the concentration between the material surface and other places occurs and the dissolution rate of the gas gradually decreases.

  However, when a molding material having a very low viscosity such as PDMS is used, the gas easily dissolves in the molding material because stirring easily proceeds due to mechanical vibration or thermal motion of molecules constituting the molding material. When injection molding is performed in a state where a lot of gas is dissolved in the molding material, the gas is manifested as bubbles due to a slight negative pressure due to the flow of the resin, and it cures while remaining inside the molded product. A major cause of defects. Therefore, when injection molding is performed using a molding material having an extremely low viscosity, it is an extremely important issue to use a dense material in which no gas is dissolved or mixed as bubbles.

  Conventionally, in order to completely fill the inside of the injection molding apparatus with a dense molding material, the discharging operation of the molding material called purge is repeatedly performed. If the injection molding apparatus is filled with the molding material only by this purging operation, it is necessary to discard the molding material at least 10 times the internal volume of the injection molding apparatus in order to discharge the entrained bubbles.

  However, a liquid silicone having a very low viscosity such as PDMS is relatively expensive as compared with other molding materials, and some resins, for example, cost 100,000 yen per liter. For this reason, the loss by wasting material is large. For example, the internal volume of the injection molding apparatus is about 0.1 liters even if it is small, and in this case, 1 liter of material is discarded by the purge operation. If the resin is 100,000 yen per liter, a loss of 100,000 yen occurs only by the purge operation.

  For this reason, injection molding using PDMS as a molding material has not been performed so far, and generally, a technique called casting is used for molding PDMS. Casting is a simple technique that simply pours the material measured with a beaker or syringe into the mold, resulting in many molding defects such as bubbles remaining, filling defects, and thickness variations, resulting in stable quality molding. I can't do it. Moreover, since it takes 2-3 hours for one molding process, mass production such as 10,000 pieces per month has not been performed so far.

  However, in the current situation where the application field of PDMS is expanding, mass production is indispensable when a resin with extremely low viscosity such as PDMS is used as a molding material. There is a strong demand for an injection molding apparatus that can effectively remove the gas dissolved in the inside and densely fill the flow path in the injection molding apparatus with a molding material without causing molding defects. Yes.

  An example of a technique relating to removal of gas in the molding material is described in Patent Document 1 and Patent Document 2. Further, Patent Document 3 and Patent Document 4 describe examples of techniques aimed at cutting the contact between the liquid material and air.

JP-A-6-122131 JP 2010-64457 A International Publication No. 2008/084813 JP-A-8-119385

  However, in the device described in Patent Document 1, although the molding material is degassed, there is only a means for processing the bubbles remaining in the piping or the molding machine by pushing out the resin with a discharge operation called purging. Further, when the same material is continuously added and used, a vent is provided in the middle of the piping, and only a material containing bubbles that is caught when the material tank is replaced is devised.

  However, waste of materials is inevitable because a large amount of resin is discarded according to the length of the pipe. Among resin materials that have been attracting attention in recent years, there are expensive ones, and there are many examples in which molding is performed with a small amount of resin material. When purging such an expensive and small amount of resin material, the amount discarded is not negligible, so it is necessary to remove the gas in the molding material without performing the purging operation. .

  Moreover, although what is described in patent document 2 is a molding machine only for liquid resin, it does not consider about deaeration of material, and mixing of the bubble to a molded article cannot be prevented. Further, the pressure is reduced to less than the atmospheric pressure after the injection is finished, and this operation may cause bubbles in the material and cause molding defects. Furthermore, in mass production, the storage amount of the material becomes reasonably large, but since the liquid resin material is a compressed fluid, the amount of material discharged from the molding machine increases as the volume of the material to be pushed or pulled increases. The problem that control becomes difficult arises. For this reason, it is not possible to sufficiently cope with mass production only by means for pressing the storage material.

  Patent Document 3 reports a container that can be degassed under reduced pressure and includes a movable plate that covers a part of the surface of the material. However, this technique assumes a high-viscosity liquid resin, and a sufficient effect cannot be obtained in the case of an extremely low-viscosity material such as 20 Pa · s or less. In addition, it is characterized in that degassing is completed quickly by increasing the liquid level using a shower, but in the case of a material with extremely low viscosity, the bubbles can easily move through the material, so the surface area There is no need to increase

The movable plate that covers a part of the surface of the material is provided to prevent the “rat hole” that the liquid level just above the discharge port drops extremely when the material is highly viscous. Yes, the size is insufficient to prevent the gas from being melted when pumped.
Further, there is no means for preventing the compressed air from re-melting into the molding material when the molding material is pumped. Further, only the deaeration of the tank in which the molding material is accumulated is performed, and according to this configuration, a purge operation is required, which is not suitable for processing using a small amount of resin as the molding material.

  Further, the one described in Patent Document 4 is characterized in that the inner surface of the tank and a part thereof have a minute gap, and the replenisher quickly enters the lower side of the floating lid to reduce the contact area with air. The present invention relates to a storage tank float that covers the surface. According to this technology, although the effect of preventing the gas from being dissolved again can be obtained with respect to the material that has been degassed, it is not assumed that the gas is degassed. The inside of the tank is depressurized in a floating state, and when depressurizing and degassing, it acts in a direction that prevents gas degassing. Therefore, it is necessary to open the container once and remove the drop lid. If a gap sufficient for gas discharge is provided between the tank inner surface, the floating lid cannot sufficiently perform the function of reducing the contact area with the air.

  Therefore, no matter what conventional technology is used, a very low viscosity resin such as PDMS can be used as a molding material, and the gas dissolved or foamed in the molding material can be used without wasting the material. Cannot be removed.

  The present invention has been made in consideration of such circumstances, and without incurring the molding material, sufficiently degassing the gas mixed in the molding material as a foam or foam, and an injection molding apparatus An object of the present invention is to provide an injection molding apparatus and an injection molding method in which a molding material can be densely filled in an inner flow path and no molding defects occur.

  In order to solve the above-described problems, an injection molding apparatus according to the present invention includes a storage pumping unit for storing and pumping a liquid resin as a molding material, and a mold for measuring the liquid resin pumped from the storage pumping unit. An injection molding apparatus comprising a metering injection unit for injecting the liquid, wherein the storage pumping unit includes a tank for storing the liquid resin, and an intake / exhaust port for degassing and pumping the liquid resin by decompression, The tank is installed at a higher position than any position in the resin flow path from the resin delivery port provided on the bottom surface of the tank to the discharge port of the nozzle provided in the metering injection unit. Features.

  The tank is installed at a higher position than any position of the resin flow path from the resin delivery port provided on the bottom surface of the tank to the discharge port of the nozzle provided in the metering injection unit. When the liquid resin is degassed, the generated bubbles do not stay in the resin flow path, but quickly rise to the tank side. Therefore, when degassing by depressurizing the tank, the liquid resin in the injection molding apparatus is also degassed at the same time, and the metering injection unit can be filled with resin that does not contain gas. Therefore, it is possible to realize an injection molding apparatus that does not cause molding defects without wasting molding material.

  In the injection molding apparatus of the present invention, a drop lid for the liquid resin accommodated in the tank is attached in a structure movable in the vertical direction of the tank, and the drop lid is a vacuum degassing of the liquid resin. In this case, it is arranged at an upper position that does not hinder deaeration, and when the liquid resin is pumped by pressurizing the inside of the tank, it is lowered to cover the surface of the liquid resin. preferable.

  By making the drop lid moveable in the vertical direction of the tank, when degassing the liquid resin in the tank, the drop lid is raised so that the drop lid does not cover the surface of the liquid resin. In addition to promoting degassing, when degassing is completed, the drop lid can be lowered to cover the surface of the liquid resin to prevent contact between the liquid resin and air after degassing. The state in which the molding material does not contain gas, which is realized by the deaeration process, can be maintained.

  In the injection molding apparatus according to the present invention, it is preferable that a part capable of visually observing the state of the liquid resin is provided in a part of the tank and the resin flow path.

  By providing a visible portion, it is possible to monitor the deaeration state of the liquid resin in detail without opening the tank lid, and it is confirmed that the deaeration process is completed and the process proceeds to the next process. It is possible to maximize the effects of deaeration.

  In a conventional device for performing deaeration in a tank, the completion point of deaeration is determined from the degree of vacuum and time. However, even if the degree of vacuum is high, the bubbles may not be completely removed from the material, and the time required for degassing varies depending on the material. Thus, there is a problem that high quality products are not always obtained. On the other hand, in the present invention, since it is possible to directly confirm whether or not bubbles are contained in the liquid resin material, it is possible to reliably determine the deaeration completion time at the shortest, shortening the defoaming time, It is possible to reduce molding defects due to air bubbles.

  In the injection molding apparatus of the present invention, it is preferable that the lower surface of the drop lid is formed to have the same shape as the bottom surface of the tank.

  By matching the shapes of the bottom surface of the drop lid and the bottom surface of the tank, the liquid resin as the molding material can be used without waste.

  The injection molding method of the present invention includes a storage pumping unit that stores and pumps a liquid resin that is a molding material, and a metering injection unit that measures the liquid resin pumped from the storage pumping unit and injects the resin into a mold. An injection molding method using an injection molding apparatus, wherein a resin flow path from a resin delivery port provided on the bottom surface of a tank containing liquid resin to a discharge port of a nozzle that guides liquid resin to a mold In a state in which the liquid resin in the tank installed at a position higher than any position, the step of degassing the liquid resin in the resin flow path, and the contact between the degassed liquid resin and air are prevented. A step of pumping the degassed liquid resin and injecting and molding the liquid resin.

  As a result, when the liquid resin is degassed, the generated foam does not stay in the resin flow path and can quickly rise to the tank side, and the resin that does not contain foam is densely placed in the metering injection part. Can be filled. Moreover, when the deaeration is completed, the liquid resin is realized in the deaeration process by pumping the liquid resin in a state in which the contact between the liquid resin after the deaeration and the air is prevented. The filled state can be maintained.

  According to the present invention, without wasting the molding material, the gas dissolved or mixed in the molding material is sufficiently degassed, and the molding material is densely filled into the flow path in the injection molding apparatus. Therefore, an injection molding apparatus and an injection molding method that do not cause molding defects can be realized.

It is a figure which shows the structure of the injection molding apparatus which concerns on embodiment of this invention. It is a figure which shows the state which has injected | throwed-in liquid resin to the tank. It is a figure which shows a deaeration process. It is a figure which shows the state of deaeration completion. It is a figure which shows the state which has arrange | positioned the drop lid with respect to the surface of the liquid resin in a tank. It is a figure which shows the process of pressure feeding and measurement of liquid resin. It is a figure which shows the state which the nozzle of the injection molding apparatus is touching with respect to the metal mold | die. It is a figure which shows a mode that liquid resin is inject | poured and filled in the metal mold | die. It is a figure which shows the state which closed the needle valve. It is a figure which shows the state which has made the nozzle retreat from a metal mold | die. It is a figure which shows the mode of a mold opening. It is a figure which shows the mode of protrusion and mold release.

Below, this invention is demonstrated based on the embodiment.
FIG. 1 shows the structure of an injection molding apparatus according to an embodiment of the present invention.
The injection molding apparatus 1 includes a storage pumping unit 2 that stores and pumps a liquid resin that is a molding material, and a metering injection unit 3 that measures the liquid resin pumped from the storage pumping unit 2 and injects the liquid resin into a mold. ing. The injection molding device 1 is a particularly effective device when performing injection molding using a liquid resin, particularly PDMS, as a molding material, a liquid resin having an extremely high viscosity with an upper limit of viscosity of 20 Pa · s.

  The storage and delivery unit 2 includes a tank 12 for containing the liquid resin 11, and the tank 12 is provided with a viewing window 13 for allowing the state of the liquid resin 11 accommodated therein to be visually observed. It has been. The observation window 13 functions as a visible portion and can be formed using a transparent material such as glass or acrylic. Further, the visible portion may be in any other form as long as the state of the liquid resin 11 in the tank 12 can be visually observed. A cooling water flow path 14 is provided in the tank 12, and the outer periphery of the tank 12 is covered with a heat insulating material 15 as necessary.

  A detachable upper lid 21 is attached to the upper portion of the tank 12, and a rod 22 is attached to the center of the upper surface of the upper lid 21 so as to penetrate the upper surface of the upper lid 21 in the vertical direction. A drop lid 23 is attached below the rod 22, and the drop lid 23 can be moved in the vertical direction of the tank 12 by an external actuator 24. The side surface of the upper lid 21 is provided with an intake / exhaust port 25 used for air deaeration and pressure feeding.

  The drop lid 23 can cover the surface of the liquid resin 11 accommodated in the tank 12. Since the drop lid 23 is structured to be movable in the vertical direction of the tank 12, when degassing, the drop lid 23 is raised so that the drop lid 23 does not cover the surface of the liquid resin 11. While promoting the deaeration, when the deaeration is completed, the drop lid 23 is lowered so that the drop lid 23 covers the surface of the liquid resin 11 to prevent contact between the liquid resin after deaeration and the air. Making it possible.

  The metering injection unit 3 includes a plunger 31 that is a rod-like piston that measures liquid resin and injects it into a mold, a nozzle 34 that is a conduit for guiding the liquid resin to the mold, and other components described later. .

  A first flow path 26 for feeding out the liquid resin 11 is provided from the bottom surface 42 of the tank 12, and the first flow path 26 is connected to a second flow path 27 in the metering injection unit 3. . The liquid resin fed through the first flow path 26 reaches the plunger front portion 28 via the second flow path 27, where the plunger 31 moves and the injection amount of the liquid resin is measured. The

  A needle valve 32 is provided in the metering injection unit 3, and a check valve 33 is provided in the needle valve 32 for preventing the liquid resin from flowing back. The nozzle 34 is provided with a third flow path 29 of liquid resin, and the liquid resin measured by the plunger front portion 28 is discharged from the discharge port 30 at the tip of the nozzle 34 through the third flow path 29. Is done.

  The lower end side of the needle valve 32 is inserted into the third flow path 29 in the nozzle 34, and the lower end portion of the needle valve 32 contacts or discharges the discharge port 30 at the tip of the nozzle 34, It functions as a needle valve 35. When the needle valve 35 is opened, the measured liquid resin is injected into the mold by the plunger 31 sliding and moving along the pot 36 which is a cylindrical housing. A cooling jacket 37 is provided on the outer periphery of the nozzle 34.

  A viewing window 38 for visually observing the state of the liquid resin is provided at a portion where the measured liquid resin is accumulated. The observation window 38 can be formed using a transparent material such as glass or acrylic. A cooling water passage 39 is provided around the portion where the measured liquid resin is accumulated, and the outer periphery thereof can be covered with a heat insulating material 40 if necessary. Above the needle valve 32, a needle actuator 41 is attached.

  In the injection molding apparatus of the present invention, the first flow path 26 and the second flow path 27 are provided from the resin delivery port 43 provided on the bottom surface 42 of the tank 12 to the discharge port 30 at the lower end 44 of the nozzle 34. 1 and the third flow path 29 are provided with a series of resin flow paths, but as shown in FIG. 1, the tank 12 is positioned higher than any position of the resin flow paths. is set up. By adopting this structure, it is possible to quickly raise the generated foam to the tank 12 side without remaining in the resin flow path in the deaeration process to be described later, and the measurement injection unit 3 contains the foam. Can be packed tightly with no resin. Further, the resin flow path is always formed upward or obliquely upward from the discharge port 30 at the lower end 44 of the nozzle 34 toward the resin delivery port 43, and there is a portion that is downward or obliquely downward. Absent. Therefore, it is possible to more effectively prevent bubbles generated in the resin channel from staying in the resin channel.

  The bottom surface 42 of the tank 12 is an inclined surface with the resin delivery port 43 at the lowest position, and the lower surface 45 of the drop lid 23 is an inclined surface whose shape matches the bottom surface 42 of the tank 12. By matching the shape of the bottom surface 42 of the tank 12 and the shape of the lower surface 45 of the drop lid 23, the liquid resin 11 stored in the tank 12 can be sent to the metering injection unit 3 without remaining in the tank 12. it can. Further, since the lower surface 45 of the drop lid 23 is an inclined surface, it is possible to prevent air from being caught when the drop lid 23 comes into contact with the liquid surface of the resin.

Next, the operation of the injection molding apparatus according to the embodiment of the present invention and the injection molding method will be described with reference to FIGS. In FIGS. 2 to 12, reference numerals are given only to those necessary for the explanation, and the other parts are the same as those in FIG.
FIG. 2 shows a state in which the liquid resin 11 is put into the tank 12. (A) is the whole figure, (b) is an enlarged view of A part of (a), (c) is an enlarged view of B part of (a).

  When the injection shown in FIG. 2 is performed, the needle valve 35 at the tip of the nozzle 34 is closed, the check valve 33 for preventing backflow is opened, the upper lid 21 is removed from the tank 12, and the liquid resin 11 is transferred to the tank 12. throw into. In consideration of the speed of deaeration, the position of the plunger 31 at this time is preferably set to the forward position as shown in FIG. Considering that bubbles are generated in the tank 12 during degassing and the liquid resin 11 swells in the tank 12, the amount of the liquid resin 11 charged into the tank 12 is 3 minutes of the volume of the tank 12. 2 or so.

  When the liquid resin 11 is charged, bubbles 51 are present in the resin flow path of the injection molding apparatus as shown in FIG. Moreover, as shown in (c), there is a portion 52 in which the liquid resin is not filled, and the liquid resin is not densely filled in the injection molding apparatus.

FIG. 3 shows the deaeration process. (A) is the whole figure, (b) is the enlarged view of C section of (a).
At the time of vacuuming shown in FIG. 3, the upper lid 21 is attached to the tank 12 and vacuuming is performed by the intake / exhaust port 25. As a result, the inside of the tank 12 is depressurized, the air contained in the liquid resin 11 becomes obvious, and many bubbles 51 are generated. Since the tank 12 is installed at a position higher than any of the first flow path 26, the second flow path 27, and the third flow path 29 of the liquid resin, the tank 12 is generated in the flow paths of these liquid resins. The bubble 51 is guided through the first flow path 26 without staying in the tank 12 as shown in FIG. Therefore, deaeration in the injection molding apparatus can be performed effectively.

At this time, the drop lid 23 is in the raised position, and the drop lid 23 does not cover the surface of the liquid resin 11 to promote deaeration.
The generated bubbles 51 are broken and eliminated with the passage of time. However, by appropriately repeating the air release and evacuation, the bubbles are broken during the air release, so the time of the deaeration process can be shortened. .

FIG. 4 shows a state where deaeration is completed. (A) is the whole figure, (b) is the enlarged view of D section of (a).
When the deaeration process is performed for a predetermined time, no large bubbles are present in the liquid resin, and the liquid resin is filled up to the end of the nozzle 34 as shown in FIG. It will be in a state of being densely packed inside.
Since the inspection window 13 is provided in the tank 12, the state of bubbles in the liquid resin 11 can be monitored in the deaeration process, and the absence of bubbles can be confirmed and the process can proceed to the next step. .

  FIG. 5 shows a state in which the drop lid 23 is lowered and the drop lid 23 is disposed on the surface of the liquid resin 11 in the tank 12. The drop lid 23 can be lowered by an external operation. For example, it can be performed by the operation of the external actuator 24. By disposing the drop lid 23 on the surface of the liquid resin 11 in the tank 12, contact between the liquid resin 11 and air can be prevented, and the liquid resin 11 realized by the deaeration process is contained in the injection molding apparatus. It is possible to maintain a tightly packed state.

  FIG. 6 shows a process of pumping and measuring the liquid resin 11. Compressed air is sent into the tank 12 from the intake / exhaust port 25, and the liquid resin 11 is sent under pressure. By this pumping process, the minute bubbles remaining in the liquid resin 11 disappear. The gas sent from the intake / exhaust port 25 is not limited to air, and may be another type of gas as long as it is a clean gas.

  The plunger 31 is moved to a predetermined position to measure the liquid resin to be injected. In this step, a constant amount of liquid resin can be measured each time by always keeping the pumping pressure and the measuring position of the plunger 31 at a constant value.

  If the pumping pressure is too low, the flow rate of the liquid resin fed into the pot 36 is reduced, and the negative pressure is not reached in time for the metering speed, and bubbles are generated, causing defective molding. On the other hand, when the pumping pressure is too high, the problem of the pressure resistance of the tank 12 occurs. As an example of the pumping pressure, the pressure can be about 0.3 MPa.

FIG. 7 shows a state where the nozzle of the injection molding apparatus is touching the mold. (A) is the whole figure, (b) is the enlarged view of E section of (a).
In the present embodiment, the tank 12 and the injection unit including the pot 36 and the plunger 31 move in the vertical direction, and the nozzle 34 is pressed and connected to the mold 61 heated in advance.

  FIG. 8 shows a state in which a liquid resin is injected and filled into a mold. (A) is an overall view thereof, (b) is an enlarged view of an F portion of (a), (c) is an enlarged view of a G portion of (a), and (d) is an enlarged view of an H portion of (a). is there.

  The needle valve 32 is raised and the check valve 33 is closed as shown in FIG. In this state, as shown in (c), the needle valve 35 is opened, and the liquid resin is injected into the mold 61 at the set speed and pressure. The liquid resin 11 injected into the mold 61 begins to harden when it touches the heated mold 61, and is filled in a completely solidified state in the mold 61 as shown in FIG.

FIG. 9 shows a state in which injection is stopped by closing the needle valve 35. (A) is the whole figure, (b) is the enlarged view of I section of (a).
By closing the needle valve 35, the injection of the liquid resin into the mold 61 is stopped. In this embodiment, the check valve 33 is opened.

FIG. 10 shows a state where the nozzle 34 is retracted from the mold 61. (A) is the whole figure, (b) is the enlarged view of J section of (a).
With the needle valve 35 closed, the nozzle 34 is retracted from the mold 61 and released to cut off the heat conduction from the mold 61 to the nozzle 34. In this state, it waits until the liquid resin with which the metal mold | die 61 was filled becomes predetermined | prescribed hardness. When molding is performed continuously, measurement for the next molding may be started in this state.

FIG. 11 shows a state of mold opening. (A) is the whole figure, (b) is the enlarged view of the L section of (a).
The mold opening speed can be controlled to be slow at first, then fast, and slow when stopped. At this time, the protrusion 62 of the mold 61 is not lifted, so that the molded product 63 is not separated from the mold 61.

FIG. 12 shows the state of protrusion and mold release. (A) is the whole figure, (b) is the enlarged view of K section of (a).
In the example shown in FIG. 12, the protrusion 62 of the mold 61 is lifted, so that the injection-molded molded product 63 is released from the mold 61. Another method may be used as the mold release method.

  As described above, the injection molding method of the present invention stores the liquid resin 11 which is a molding material and pumps it, and measures the liquid resin 11 pumped from the storage pumping unit 2 to measure the mold. An injection molding method using an injection molding apparatus 1 equipped with a metering injection unit 3 for injecting into a nozzle, and discharging a nozzle 34 from a resin delivery port 43 provided on a bottom surface 42 of a tank 12 containing a liquid resin 11. The step of degassing the liquid resin in the tank 12 installed at a position higher than any position of the resin flow path leading to the outlet 30, the liquid resin in the resin flow path, and the degassed liquid resin 11 And a step of pumping the degassed liquid resin 11 and injecting and molding the liquid resin 11 in a state in which contact with the air is prevented. In the present embodiment, the state in which contact between the degassed liquid resin 11 and the air is prevented is because the drop lid 23 attached in a structure movable in the vertical direction of the tank 12 is detached from the tank 12. This is realized by covering the surface of the liquid resin 11 that has been noticed.

  By having these steps, when the liquid resin 11 is degassed, the generated bubbles 51 quickly rise to the tank 12 side without staying in the resin flow path. Therefore, it is possible to densely fill the metering injection unit 3 with a resin that does not contain bubbles. Moreover, when deaeration is completed, the drop lid 23 covers the surface of the liquid resin 11 to prevent contact between the liquid resin 11 and the air after deaeration. Therefore, it is possible to maintain a state in which the inside of the injection molding apparatus is densely filled with a liquid resin that does not contain gas in the form of dissolution or mixing of bubbles, which is realized by the deaeration process.

  In the case of a material tank in which deaeration and pressure feeding are performed in one container, in the conventional material tank, it is necessary to open the tank lid and take out and put in the drop lid every time the degassing and pressure feeding processes are switched. For this reason, in addition to the time required for the work, there is a problem that the number of times the lid is opened and closed increases, so that there is a high risk of dust entering the molding material, and the material adheres to the outside of the container and becomes dirty. .

  However, in the present invention, the structure in which the drop lid 23 can be moved in the vertical direction of the tank 12 by driving from the outside without opening the lid does not hinder the deaeration of the gas during the decompression deaeration, In addition, it is possible to prevent the gas from being dissolved again in the material at the time of pumping, and it is possible to solve two conflicting problems at the same time. Further, the outside of the container is not soiled and the risk of dust contamination can be reduced.

  Further, since the purge operation is unnecessary, it is possible to reduce the waste of materials as much as possible, and it is possible to perform molding with a small amount of molding material. Furthermore, by changing from the conventional manual operation to injection molding, molding defects can be solved by precise weighing and injection control by a machine. Moreover, the time required for one molding is shortened to about 3 minutes. Thereby, it is possible to perform molding with stable quality and mass production such as 10,000 pieces per month.

  The present invention fully degass the gas dissolved or foamed in the molding material without wasting the molding material, and densely fills the molding material in the flow path in the injection molding apparatus. It can be used as an injection molding apparatus and an injection molding method that do not cause molding defects, and is particularly effective when injection molding is performed using a liquid silicone resin having an extremely low viscosity as a molding material, such as PDMS. is there. Therefore, with the expansion of the field of use of PDMS, the industrial application range is expected to expand in the scene of mass production of molded products using PDMS as a molding material.

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Storage pumping part 3 Metering injection part 11 Liquid resin 12 Tank 13 Peep window 14 Cooling water flow path 15 Heat insulating material 21 Upper cover 22 Rod 23 Drop cover 24 External actuator 25 Intake / exhaust port 26 First flow path 27 Second flow path 28 Plunger front portion 29 Third flow path 30 Discharge port 31 Plunger 32 Needle valve 33 Check valve 34 Nozzle 35 Needle valve 36 Pot 37 Cooling jacket 38 Peep window 39 Cooling water flow path 40 Heat insulation material 41 Actuator for needle 42 Tank bottom surface 43 Resin delivery port 44 Lower end of nozzle 45 Lower surface of drop lid 51 Foam 52 Location where liquid resin is not filled 61 Mold 62 Projection 63 Molded product

Claims (3)

An injection molding apparatus comprising: a storage pumping unit that stores and pumps liquid resin that is a molding material; and a metering injection unit that measures and injects the liquid resin pumped from the storage pumping unit into a mold,
The storage pumping unit includes a tank for storing a liquid resin, and an intake / exhaust port for degassing and pumping the liquid resin by decompression, from a resin delivery port provided on the bottom surface of the tank, The tank is installed at a position higher than any position of the resin flow path leading to the nozzle outlet provided, and drop lids for the liquid resin contained in the tank are disposed above and below the tank. The drop lid is disposed at an upper position that does not prevent degassing when the liquid resin is degassed under reduced pressure, and pressurizes the inside of the tank to pump the liquid resin. An injection molding apparatus, wherein the injection molding apparatus is disposed at a position where the liquid resin is lowered and covers the surface of the liquid resin . Wherein the portion of the resin flow path and the tank, an injection molding apparatus according to claim 1, wherein a visible portion visible the state of liquid resin is provided. The injection molding apparatus according to claim 1 or 2 , wherein the lower surface of the drop lid is formed to have the same shape as the bottom surface of the tank.

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