JP5580666B2 - Hard liquid resin molding die and hard liquid resin molding method - Google Patents

Description

  The present invention relates to a mold for molding a hard liquid resin such as liquid silicon, and more particularly, to an ejector pin for projecting a product in a mold for molding a hard liquid resin such as liquid silicon and a sliding clearance between the holes. The present invention relates to a molding die having a structure that can prevent resin flow and enables mass production (continuous molding) with a hard liquid resin such as liquid silicon.

  The present invention also relates to a method for molding a hard liquid resin such as liquid silicon by a mold, and in particular, to an ejector pin for projecting a product in a mold for molding a hard liquid resin and a sliding clearance between the holes. The present invention relates to a molding method that can prevent the resin from flowing in and enables mass production (continuous molding) with a hard liquid resin such as liquid silicon.

  Recently, with the advent of high-intensity LEDs for illumination, liquid silicon resin is becoming the mainstream as a sealing material for the semiconductor element and a material for the lens portion. The reason for this is that it has excellent heat resistance, weather resistance, and transparency.

  Silicone resin is imagined as an image of a rubber-based soft material, but in the above usage, there is a demand for liquid silicone resin that will become harder after molding (hereinafter sometimes referred to as hard liquid resin). Growth is expected in the future.

  The molding of this hard liquid resin is a molding method in which the raw material which is liquid at room temperature is generally two-component, and the two components of the main agent and the curing agent are mixed in a certain ratio and injected into a high-temperature mold and heat-cured. It becomes. A hard liquid resin is a very high-performance resin, but a mold for molding the resin requires an advanced mold technique, and many problems remain to be overcome.

  One of them is an ultra-low viscosity resin, and therefore, the resin flows into the gap in the mold during the injection process during molding. As a final step of injection molding, when a product part is taken out from the mold, it is common to eject the product part with an ejector pin and release it. On the other hand, in the case of molding a normal thermoplastic resin, the clearance between the ejector pin and the hole is provided from about 5 μm to 10 μm on one side even in the case of a resin having good fluidity. It is unlikely to disturb the movement of the mold.

  On the other hand, in the case of a hard liquid resin, even if the clearance between the ejector pin and the hole is 3 μm on one side, the resin gets into the gap and falls into a non-slidable state due to clogging. A clearance of 1 μm or less on one side must be maintained during resin filling.

  However, if the clearance between the ejector pin and the hole is reduced, the sliding resistance between the ejector pin and the hole will increase, which may cause galling, so it is not a problem to be solved if the clearance is easily reduced. In this situation, mass production has not been achieved.

  In order to solve this problem, the present invention has a novel structure of the ejector portion.

  Although no prior invention that directly solves the problem of the present invention has been found, Patent Document 1 discloses an invention that prevents the occurrence of flashes that protrude around a protruding pin during injection molding. In this invention, the movable side mold that advances and retreats with respect to the fixed side mold is provided with a protruding pin for discharging the molded product in the cavity. This protruding pin is made of a brass material which is a material having a thermal expansion coefficient larger than that of the mold material. At normal temperature, the diameter of the protruding pin is about 0.03 mm smaller than the inner diameter of the communication hole, and the protruding pin is easily inserted into the communication hole when the mold is assembled. At the time of molding, the temperature of the entire mold rises, and the protruding pin is thermally expanded to increase its diameter. On the other hand, since the communication hole expands only slightly, the gap between the protruding pin and the communication hole becomes small, the resin injected into the cavity does not enter the gap, and the molded product does not flash.

  Patent Document 2 discloses that a resin molded product with a high quality appearance can be obtained by improving the transferability of fine irregularities without extending the molding cycle through efficient temperature control and preventing the generation of burrs. A molding die apparatus is disclosed in which the heat insulating material is hardly deteriorated and the structure is simple. According to the present invention, in a molding die apparatus for obtaining a resin molded product in which a resin having a fine concavo-convex shape on its inner surface is filled with a resin and the fine concavo-convex shape is transferred and formed on the surface, the mold on the movable side A cavity is formed by facing both mold parts provided on the plate and the fixed-side mold plate, and a heat insulating layer is formed between the outer surface and the mold plate so that the mold part can be temperature-adjusted. A gap is formed around the mold plate and the dimension of the gap is set so as to be closed by thermal expansion of the mold part during molding.

  Furthermore, Patent Document 3 discloses an invention relating to an injection mold that aims to easily and surely prevent galling between the movable side insert and the movable side mold plate. . The present invention is for injection molding in which a movable side mold plate is disposed so as to face a fixed mold, and a movable side insert moved by a protruding mechanism is inserted into a through hole formed in the movable side mold plate. In the mold, a ring-shaped guide member fitted to the movable side insert is detachably disposed in the through hole of the movable side template. Further, the guide member is configured by being arranged in an annular recess formed concentrically with the through hole on the end surface of the movable mold plate on the fixed mold side.

  Furthermore, Patent Document 4 discloses a casting apparatus and a casting method that can raise the mold effectively and quickly to a desired temperature and improve the yield of cast products. The casting apparatus according to the present invention has a fixed mold and a movable mold, and has a plurality of projecting pins inserted and disposed in projecting holes penetrating the movable mold. The movable type is provided with a temperature raising circuit, and the protruding pin is also provided with a temperature raising circuit. High temperature oil is allowed to flow through the temperature raising circuit to raise the temperature of the retainer plate and the ejector plate that hold the proximal end portion of the ejection pin, thereby indirectly raising the temperature of the ejection pin. This effectively raises the temperature of the mold including the movable mold.

JP-A-6-246799 JP 2000-238103 A JP-A-10-655 JP 2009-50855 A

  Since a hard liquid resin such as hard liquid silicon has a very low viscosity, a high mold and a high dimensional accuracy are required in a mold that is injected into a mold and molded. As one of the problems, there is a problem that the resin flows into a gap of several μm between the ejector pin installed for taking out the product and the hole, and the ejector pin cannot move due to the clogged resin.

  The present invention is intended to solve the above-mentioned problems and problems, and can prevent the resin from flowing into the clearance portion of the ejector pin and the hole, and also ensures an appropriate clearance during the ejection operation, thereby enabling mass production molding. The present invention relates to a mold having a partial structure.

  In order to enable mass production molding of hard liquid resin such as hard silicon, the present invention uses an electromagnetic induction heating method and applies a temperature change to the ejector pin within a molding cycle. ) Is changed so that an appropriate clearance can be secured at the time of resin filling and at the time of ejection operation.

The mold for molding a hard liquid resin of the present invention is a mold composed of a movable mold and a fixed mold for molding a hard liquid resin, and is formed between an ejector pin provided in one mold and a hole of the mold. to properly control the clearance around the ejector pin, only setting the temperature control means of the ejector pin, characterized by heating the ejector pins to a temperature higher than the temperature in the mold.

  Further, in the hard liquid resin molding die of the present invention, the temperature control means of the ejector pin comprises an electromagnetic coil as a heating means of the ejector pin and a thermocouple as a temperature measuring means.

The method of molding a hard liquid resin of the present invention is a method of molding a hard liquid resin by a mold composed of a movable mold and a fixed mold, wherein the temperature of the ejector pin is higher than the temperature in the mold within the molding cycle. By controlling so that it is heated , the clearance between the ejector pin and the hole of the mold is controlled for each molding operation.

  Furthermore, when the temperature of the ejector pin is controlled within the molding cycle, the rigid liquid resin molding method of the present invention detects the temperature of the ejector pin by a thermocouple as the temperature measuring means of the ejector pin, and electromagnetically acts as the heating means. The ejector pin is heated by a coil.

  As described above, according to the present invention, by giving an appropriate temperature change to the ejector pin within the molding cycle, the clearance between the ejector pin and the hole can be reduced to 2 μm or less on one side during resin filling, and the clearance of 4 μm on one side during ejection. Since it can be provided and sliding galling during the resin filling and ejection operations can be prevented, mass production molding can be made possible.

(A) (B) Sectional drawing of the mold for rigid liquid resin molding of this invention which installed the ejector pin temperature control apparatus (A) (B) (C) (D) (E) Clearance control diagram in the molding cycle for explaining temperature control of the ejector pin in the hard liquid resin molding method of the present invention.

  An embodiment of the hard liquid resin molding die of the present invention will be described with reference to the drawings. FIG. 1A shows the entire structure of a hard liquid resin molding die of the present invention equipped with an electromagnetic induction heating method, and FIG. 1B shows a detailed structural view in the vicinity of the ejector pin. Hereinafter, in the present invention, the vertical direction is expressed in FIG. 1A, but this does not mean the same as the installation direction of the entire apparatus.

  The hard liquid resin molding die of the present invention shown in FIG. 1A is composed of an upper die 10 (movable die) and a lower die 20 (fixed die). Although an injection molding machine is installed above the upper mold 10, it is not shown here because it is not an invention relating to the structure of the injection molding machine. An injection nozzle of an injection molding machine (not shown) touches the center line portion of FIG. The injection molding machine repeats mold clamping, weighing, injection (molding), cooling, mold opening, and ejecting in a normal cycle. The resin injected from the injection molding machine at the time of injection molding is supplied from the injection nozzle to the sprue 1 and passes through the runners 2 arranged radially to fill the product portion 3. In general, a plurality of radial runners 2 are provided, whereby a plurality of product parts 3 can be formed simultaneously. After the filling is completed and the molded resin is cooled and hardened, the mold is opened, and the molded and hardened resin portion is ejected by the ejector pins 4 to take out the product.

  However, since the hard liquid resin such as hard liquid silicon targeted by the present invention has a very low viscosity, the resin is not in a slight clearance between the ejector pin 4 and the hole on the mold side when the resin is filled in the mold. The resin that has flowed in will solidify and the ejector pin will slide and become immobile. In some cases, a galling phenomenon may occur.

  In the present invention, in order to solve such a problem, ejector pin temperature control means is provided on the outer periphery of the ejector pin 4. This temperature control means is provided with an electromagnetic coil 5 as a heating means for an ejector pin and a thermocouple 6 as a temperature measurement means, and the temperature of the ejector pin 4 is positively controlled by a heating control device 7. Thus, by controlling the temperature of the ejector pin 4 appropriately and changing the volume (diameter dimension) of the ejector pin 4 using thermal expansion, the clearance from the hole can be controlled within the molding cycle. It is possible.

  The protruding operation of the molded and hardened resin portion 3 is achieved by relative movement of the lower mold 20 and the ejector pin 4 (detailed description is omitted) after the mold is opened. In a normal hard liquid resin molding die, the diameter of the ejector pin 4 is 3 to 4 mm, and the clearance from the die hole on the die surface is generally 2 to 3 μm on one side. If there is such a clearance, the ejector pin 4 can smoothly move up and down in the lower mold 20. Since this clearance only needs to be achieved on the mold surface, as shown in FIG. 1B, the hole in the mold expands downward inward of the mold. An electromagnetic coil 5 as a heating means for the ejector pin and a thermocouple 6 as a temperature measuring means are provided in a portion where the hole in the mold is widened.

  FIGS. 2A to 2E are diagrams showing clearance control between the ejector pin 4 and the hole of the mold in the molding process of the hard liquid resin using the mold for molding the hard liquid resin of the present invention. is there. First, in a normal state (the state shown in FIG. 2A), it is formed in such a size as to provide a clearance of 2 to 3 μm on one side. Thereafter, heating is performed, and a predetermined current is passed through the electromagnetic coil 5 by the heating control device 7 so that the temperature of the ejector pin 4 is rapidly increased to a predetermined temperature, so that the clearance from the mold hole is substantially 0 μm ( FIG. 2B). At this time, since the heating control device 7 can know the temperature of the ejector pin 4 by the thermocouple 6 as temperature measuring means, it knows how much current can be flowed to the predetermined temperature. be able to. During normal injection molding, the mold temperature is about 150 ° C., and the eject pin 4 is preferably about 250 ° C. higher (about 400 ° C.). In this way, with the clearance between the ejector pin 4 and the hole substantially 0 μm (clearance close to 0 μm of 1 μm or less), the resin is injected by the injection operation of the injection molding machine, and the mold The product part 3 is filled with resin (state shown in FIG. 2C). After filling is complete, the injection molding machine cycle enters the cooling process, whereupon the heating of the ejector pins 4 is stopped. The ejector pin 4 returns to the original state by cooling (the state shown in FIG. 2D). In FIG. 2 (D), the clearance is set to 2 to 3 μm so that it takes time to cool until the clearance becomes the normal state, but it is not necessary to spend the time until here. In any case, since the temperature of the ejector pin 4 can be known by the thermocouple 6 as the temperature measuring means, it is possible to know that the clearance necessary for the ejecting operation has been formed. Then, the resin part 3 is protruded and taken out by relative movement between the lower mold 20 and the ejector pin 4 (state shown in FIG. 2E).

  In this way, by utilizing the rapid heating feature of the electromagnetic induction heating method, the clearance is substantially 0 μm when the resin is filled in the molding cycle, and a predetermined clearance is secured when the product part is taken out after the resin is cured. As a result, it is possible to prevent the ejector pins and the holes from being squeezed at the same time when the resin flows and the protrusion is caused by a small clearance.

DESCRIPTION OF SYMBOLS 1 ... Sprue 2 ... Runner 3 ... Product part 4 ... Ejector pin 5 ... Electromagnetic coil 6 ... Thermocouple 7 ... Heating control apparatus 10 ... Upper die 20 ..Lower mold

Claims (4)

In a mold comprising a movable mold and a fixed mold for molding a hard liquid resin, in order to properly control the clearance between an ejector pin provided in one mold and a hole in the mold, the ejector pin around, set the temperature control means of the ejector pin,
A mold for molding a hard liquid resin, wherein the ejector pin is heated to a temperature higher than that in the mold.   2. The mold for molding a hard liquid resin according to claim 1, wherein the temperature control means for the ejector pin comprises an electromagnetic coil as a heating means for the ejector pin and a thermocouple as a temperature measurement means. In a method of molding a hard liquid resin by a mold composed of a movable mold and a fixed mold, the molding is performed by controlling the temperature of the ejector pin to be higher than the temperature in the mold within the molding cycle. A hard liquid resin molding method characterized by molding by controlling a clearance between an ejector pin and a hole of a mold for each operation.   When controlling the temperature of the ejector pin in the molding cycle, the temperature of the ejector pin is detected by a thermocouple as a temperature measuring means of the ejector pin, and the ejector pin is heated by an electromagnetic coil as a heating means. The hard liquid resin molding method according to claim 3.

Images