JPH0939047A - Injection molding die, injection molding apparatus, and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transferability with low injection pressure by using a conventional material for a die including the surface of a cavity by a method wherein a gas vent groove is formed in a peripheral fringe part of the cavity, a hole is provided on a contact surface surrounded by a seal member excepting the peripheral fringe part, and an interconnected gas pressurizing and suction mouth is provided. SOLUTION: A groove 21 (for example, width 5mm×depth 2mm, groove pitch 15mm) is processed excepting a peripheral fringe part of a resin passage of a cavity 6, a sprue, a runner, a gate, etc., in a grid form on a contact surface to a fixed die side on a parting surface between a movable side die 3 and the fixed side die 2. Further, a gasket 20 being a seal member making the cavity 6 an airtight state after closing the die is provided. A gas vent groove is formed on a peripheral fringe part of the cavity 6. Though gas can pass through the gas vent groove, a materiel can not enter that. For example, its depth is about 3/100mm, and its length is about 5mm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injection molding die,
The present invention relates to an injection molding apparatus and an injection molding method, and particularly to an injection molding die, an injection molding apparatus, and an injection molding method for improving transferability (appearance) on one surface of a molded product.

[0002]

2. Description of the Related Art Generally, a molded article having a gloss or pattern on its surface is obtained by press-fitting a molten resin into a cavity of a mold made of a general steel material, stainless steel or the like to form the molten resin into a predetermined shape and It is obtained by transferring the gloss and pattern of the surface to the surface.

However, in the case of injection molding using such a metal mold, it is not easy to approximate the gloss and pattern of the surface of the molded product. For example, the condition of the mold surface is transferred unevenly, Weld marks and flow marks are likely to occur on the surface of molded products.

These transfer defects are due to the following causes. Since the injection mold is usually made of a metal material with good thermal conductivity, when injection molding is performed using such a mold, the molten resin filled in the cavity is the surface of the mold. Immediately upon contact with, a solidified layer is formed on the resin surface. Moreover, since the mold internal pressure is low during the molten resin filling process, the molten resin does not come into sufficient contact with the mold surface, and the molten resin surface is not uniform due to turbulent flow near the gate or unrectification. At the same time, the solidified layer is formed on the surface. Therefore, even if a predetermined high pressure is applied at the same time as the filling of the molten resin is completed, the mold surface is not sufficiently transferred because the solidified layer has already been formed on the surface of the molten resin. It also leads to the generation of marks and flow marks.

As an injection molding method for eliminating the transfer failure due to such a cause, for example, as described in Japanese Patent Application Laid-Open No. 4-219912, the cavity surface for which the transferability is desired to be improved is made of ceramics, zirconia oxide, or the like. It is known to use a mold made of a material having a heat retaining effect.

According to this mold, when the high temperature molten resin filled in the cavity comes into contact with the material having a heat retaining effect on the surface of the cavity, the temperature of the surface having the material is instantly increased and the molten resin is It exhibits excellent wettability with respect to the surface having the above-mentioned material and adhesiveness thereby. Therefore,
When the surface of the molten resin is brought into close contact with the surface of the material due to the flow pressure flowing in the mold, the molten resin adheres instantly to the surface of the material and the filling progresses, and the filling is completed. As a result, even if the holding pressure applied to the molten resin that has been completely filled is low, the surface having the material is accurately transferred to the surface of the molded product.

Further, when the surface of the material is instantly heated by the filled molten resin, the filling due to the adhesiveness due to the wettability between the surface of the material and the molten resin and the temperature increase of the interface between the two. Turbulent flow of the resin near the gate and non-rectification during filling are instantly alleviated by the filling pressure of the molten resin, and the molten resin is evenly adhered to the surface having the material. Therefore, the generation of weld marks, flow marks, etc. can be prevented.

[0008]

However, in the above-mentioned conventional example, since ceramics or the like is used for the cavity surface for which transferability is desired to be improved, processing for imparting gloss or a fine pattern to the surface of the molded product is performed. Is difficult to use and is rarely used.

On the other hand, as a method for improving transferability without using a mold made of a material having a heat-retaining effect as described above, a method of filling molten resin at a high pressure and pressing it strongly against the mold surface, or a mold as a whole There is a method of setting the temperature higher than the normal mold temperature.

In the former method, however, the size of the injection molding machine becomes large, and defects such as burrs and warps easily occur, so that a high precision injection molding machine is required. In addition, since the mold itself must be thick to withstand high pressure, manufacturing of the mold is costly, and high internal stress remains in the molded product due to high pressure filling, resulting in deterioration of the quality of the molded product. To do. Furthermore, aluminum molds and resin molds cannot be used.

In the latter method, the transferability is improved by setting the temperature of the entire mold at a high temperature, but on the other hand, the cooling (plasticizing) process requires a long time, resulting in a significant decrease in molding work efficiency. Occurs.

By the way, there are many molded products which require glossiness on one side but need only maintain the mounting dimensions on the other. Conventionally, such molded products require high transferability on only one side. Also, it was not efficient because it was formed by any of the methods described above.

In view of the above-mentioned conventional state of the art, therefore, the present invention provides a molded product which requires high transferability on only one side, and uses a conventional mold material including the cavity surface while maintaining a low injection pressure. An object of the present invention is to provide an injection molding die, an injection molding apparatus, and an injection molding method capable of improving transferability.

[0014]

In order to achieve the above object, the first aspect of the present invention is to provide a groove, a cavity, a sprue, and a groove on both or either of the contact surfaces on the parting surfaces of the fixed mold and the movable mold. It is formed by removing the peripheral portion of the resin flow passage such as a runner and a gate, and after the mold is closed, a sealing member for making an area surrounding the cavity airtight is fixed, and a gas vent groove is formed in the peripheral portion of the cavity. The injection molding die is provided with a hole formed in a contact surface surrounded by the sealing member except the peripheral portion, and further provided with a gas pressurizing / suction port communicating with the hole.

In a second aspect of the invention, in the injection molding apparatus equipped with the injection molding die, the mold temperatures of the fixed side mold and the movable side mold are set with a constant difference, and injection from the mold closing stroke is performed.
Until the end of the pressure-holding process, gas is sucked from the gas pressurizing / suction port to bring the inside of the cavity into a negative pressure state, and from the cooling process to the mold opening process, gas is pumped from the gas pressurizing / suction port to It is characterized by having a control unit for controlling the inside of the cavity to be in a pressurized state.

Further, in the third invention, the mold on the side for which the transferability is desired to be improved is maintained at a high temperature, and the mold on the opposite side is maintained at a temperature 10 ° to 80 ° lower than the mold on the high temperature side. The method is an injection molding method in which the inside of the cavity is kept in a negative pressure state from the mold closing process to the end of the injection / pressure-holding process, and the cavity is pressurized from the cooling process to the mold opening process.

(Operation) In the injection molding die of the present invention, the groove is provided on both or one of the contact surfaces of the fixed side mold and the movable side mold on the parting surface, so that the mold is contacted when the mold is closed. As a result of the reduction of the area, the thermal conductivity on the parting surface is reduced, and the temperature difference between the fixed side mold and the movable side mold is kept constant during injection. Further, when the mold is closed, the area surrounding the cavity by the sealing member is in an airtight state except for the communicating portion between the hole formed in the contact surface and the gas pressurizing / suction port.

In the injection molding apparatus using such a mold, with the fixed side mold and the movable side mold set by the controller with a constant temperature difference, after the mold is closed, filling of the molten resin into the cavity is started. From this time until the end of the pressure-holding process, gas is sucked from the gas pressurization / suction port and the hole through the gas vent groove at the peripheral edge of the cavity, so that the inside of the cavity in the area surrounded by the sealing member when the mold is closed is negative. It will be in a pressure state. As a result, the filling property of the molten resin filled in the cavity is improved. At the same time, for example, when the fixed side mold has a cavity and is set higher than the movable side mold, the molten resin is brought into close contact with the cavity surface of the fixed side mold, which is maintained at a high temperature, and instantly comes into contact with the cavity. The filling progresses while wetting the surface precisely. On the other hand, the resin surface in contact with the cavity surface on the low temperature side is cooled and contracts at the same time as the filling progresses, so that it is separated from the cavity surface on the low temperature side, and the adhesive force between the cavity surface on the high temperature side and the molten resin is The pressure decreases toward the end of the pressure holding process.

However, even if the adhesion between the surface of the cavity on the high temperature side and the molten resin deteriorates in this way, the gas is sent from the gas pressurizing / suction port from the cooling step after the pressure holding step to the mold opening step. Since the cavity is pressurized, the adhesion of the molten resin to the cavity surface on the high temperature side increases,
As a result, a molded article having a high transferability on one side can be obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view at the time of injection in an embodiment of a mold and an injection molding apparatus equipped with the same according to the present invention, and FIG. 2 is a schematic view showing a state of taking out a molded product in the apparatus shown in FIG. FIG. 3 is a cross-sectional view, and FIG. 3 is a cross-sectional view taken along the line XX of FIG.

The injection molding apparatus of this embodiment is constructed by using, for example, a pin protruding type two-piece mold. Figure 1
As shown in FIG. 2, the fixed mold 2 having the cavity 6 is mounted on the fixed mounting plate 1, and the movable mold 3 having the core 9 is mounted on the movable mounting plate 8 via the receiving plate 4 and the spacer block 5. Is attached to.

In the spacer block 5, an ejector pin 15 that can penetrate the receiving plate 4 and the core 9 and project from the core surface, and a sprue lock pin 14 that can penetrate the receiving plate 4 and the movable mold 3 to sprue. , And an ejector plate 7 that penetrates the receiving plate 4 and the movable mold 3 and supports an eject return pin 16 that can project from the movable mold 3. By providing the ejector plate 7 with the stop pin 17 that engages with the movable side mounting plate 8, the ejector plate 7 causes the return pin 16 to contact the fixed side mold 2 as the movable side mold 3 moves when the mold is closed. When it comes in contact and is pushed back, it stops at a predetermined position.

Further, as shown in FIG. 3, grooves 21 (for example, width 5 mm × depth 2 mm, groove pitch 1 are formed on the contact surfaces of the movable mold 3 and the fixed mold 2 on the fixed mold side of the parting surfaces.
5 mm) has a lattice pattern of cavities 6, sprues 18 and runners 1.
A gasket 20, which is a sealing member that is processed except for the peripheral portion 24 of the resin flow passage such as 9 and the gate 25, and that keeps the cavity 6 airtight after the mold is closed, is provided.
A gas vent groove (not shown) is provided in the peripheral portion 24 of the cavity 6.
Are formed. Gas can pass through the gas vent groove but material cannot enter. For example, the depth is about 3/100 mm and the length is about 5 mm,
The depth and length differ depending on the fluidity of the material, and it is shallow for low viscosity materials and deep for high viscosity materials.

Groove 2 surrounded by gasket 20
Holes 22a and 22b are bored on the surface on which the No. 1 is formed, and gas pressurization / suction ports 23a and 2a communicating with the holes 22a and 22b.
3b are provided on the side surfaces of the fixed mold 2, respectively. Although the groove 21 is provided on the fixed mold side in this example, the present invention is not limited to this, and it may be provided on both or one of the contact surfaces of the movable side mold 3 and the fixed side mold 2 on the parting surface. .

In addition, this apparatus sucks gas from the gas pressurizing / sucking ports 23a and 23b to make the inside of the cavity 6 in a negative pressure state from the mold closing process to the end of the injection / holding process, and the mold opening process from the cooling process. Gas pressurization / suction ports 23a, 23b up to the stroke
A control unit (not shown) is provided to control the gas so that the inside of the cavity 6 is pressurized. Then, the control unit controls the temperature of the fixed side mold 2 and the movable side mold 3 separately, and sets the molding temperature of the A surface side and the B surface side of the molded product shown in FIG. 1 to a constant difference. This set temperature difference is kept constant even during injection (when the mold is closed). That is, as described above, the mold configuration is such that the contact area is reduced by providing the groove on both or either of the contact surfaces of the parting surfaces of the movable side mold 3 and the fixed side mold 2, and thus the contact area is reduced. The heat conductivity in the mold becomes small, and the temperature difference between the fixed mold 2 and the movable mold 3 is kept constant even during injection (mold closing).

Next, an injection molding method using an apparatus equipped with the above-described mold will be described with reference to FIGS. 1 to 3.

In the state shown in FIG. 1, that is, when the movable mold 3 is moved toward the fixed mold 2 and the movable mold 3 and the fixed mold 2 are closed, sprues, runners, gates, etc. The cavity 6 is filled with the molten resin through the resin flow path, and thereafter, a pressure holding step for the molten resin in the cavity 6 is performed for a certain time. Further, after the cooling (plasticizing) step, as shown in FIG. 2, the movable mold 3 is retracted to open the mold, and the ejector plate 7 is moved to push up the ejector pin 15 to take out the molded product.

In order to improve the transferability of the surface A of the molded product shown in FIG. 2 in such a molding cycle, the temperature of the cavity 6 surface of the fixed mold 2 is the temperature of the core 9 of the movable mold 3. Will be higher than. At this time, the temperature difference can be kept constant by the mold configuration having the groove 21 described above. Further, it is possible to control the temperature difference at the time of mold closing to be constant without providing the groove 21 in the mold, but in the case without the groove 21, heat is taken to the side having a low mold temperature at the time of contact with the mold. Since this is easy, it is necessary to perform temperature control again until the injection after the mold is closed to achieve the set temperature difference. Therefore, it takes time from the mold closing to the injection, and the molding work efficiency is reduced. However, this is not the case with the mold according to the present invention.

Further, the mold temperature on the higher temperature side is preferably set to the heat distortion temperature when the molding resin is a crystalline resin and to the glass transition temperature when the molding resin is an amorphous resin. The mold temperature on the low temperature side is set to be 10 to 80 ° C. lower than the mold temperature on the high temperature side depending on the molding resin. For example, the mold temperature is set to 140 ° C. for the high temperature side and 80 ° C. for the low temperature side for polyacetal, 96 ° C. for the high temperature side for ABS resin, 60 ° C. for the low temperature side, and 130 ° C. for the high temperature side and 70 ° C. for the low temperature side for polycarbonate. In addition, the temperature difference in the above-mentioned Examples has a balance with the material characteristics and the cooling (plasticizing) time, so that the temperature difference is 10 °.
It can be appropriately set between -80 °.

During a series of molding cycles of mold closing, injection, pressure holding, mold opening, and product taking-out, from the mold closing to the pressure holding process completion, the gas pressurizing / suction ports 23a, 23b shown in FIG. Gas is sucked from the holes 22a and 22b through a gas vent groove (not shown) in the peripheral portion 24 of the cavity 6, and a negative pressure state (for example, 300 to 300) in the cavity 6 in the closed space surrounded by the gasket 20 when the mold is closed. 600 mmHg)
And As a result, the filling property of the molten resin filled in the cavity 6 is improved, and at the same time, the molten resin is kept at a high temperature, and when it comes into contact with the surface of the cavity 6, it is instantly brought into close contact with the surface of the cavity 6 while the surface of the cavity 6 is being densely filled. proceed. On the other hand, the resin surface in contact with the core 9 on the low temperature side is cooled and contracts at the same time as the filling progresses, so that the resin surface is separated from the surface of the core 9 and the adhesive force between the surface of the cavity 6 on the high temperature side and the molten resin is reduced. Progresses toward the end of the pressure holding process.

Therefore, from the cooling process after the pressure-holding process is completed, gas is sent from the gas pressurizing / sucking ports 23a and 23b to pressurize the inside of the cavity 6 (for example, 5 to 10 kg / cm ² ).
And As a result, the adhesive force of the molten resin to the surface of the cavity 6 maintained at a high temperature becomes strong, so that a molded product having a highly transferable surface can be obtained.

According to the injection molding method of this embodiment, the surface A of the molded product shown in FIG. 2 has a beautiful appearance, and the surface B is in a sinking state, but the predetermined mounting dimensions are maintained. Further, since such a molded product can be obtained with a low injection pressure, the manufacturing cost of the mold can be reduced, and an aluminum mold or a resin mold can also be used. Further, since the gas is sent to the inside of the cavity for the purpose of improving the adhesion during the cooling process, it is possible to suppress the lengthening of the cooling process due to the high temperature of the mold.

[0034]

As described above, according to the present invention, the groove is provided on both or either of the contact surfaces of the fixed side mold and the movable side mold on the parting surface, and the sealing member is used when the mold is closed. The fixed side mold and the movable mold are used by using an injection molding mold having a structure in which the area surrounding the cavity is made airtight except for the communication part between the hole formed in the contact surface and the gas suction / pressurization port. The mold temperature with the side mold is set with a constant difference, and from the mold closing process to the injection / pressure holding process, gas is sucked from the gas pressurizing / suction port to bring the inside of the cavity into a negative pressure state, and from the cooling process. Up to the mold opening process, by using the injection molding apparatus and method having a control unit for controlling the pressure of the gas from the gas pressurizing / suction port to control the inside of the cavity to be in a pressurized state, the resin filling property is improved. As the temperature rises, the mold surface heated to a high temperature and the molten resin get wet For sex and adhesion is expressed, it requires only a low injection pressure, it is possible to give excellent appearance to one surface of the molded article which contacts the mold surface to a high temperature. In addition, the resin surface in contact with one surface on the side with a slightly lower temperature starts to solidify and shrinks due to filling, but after the injection / pressure-holding process is complete, the mold surface is heated from cooling (plasticization) to the mold opening process. On the other hand, since the molten resin is pressurized, it is possible to maintain the close contact between the mold surface and the molten resin which have been heated to a high temperature.

Further, according to the present invention, as the mold material including the surface of the cavity, the conventional mold material can be used as it is, so that the processing such as gloss and pattern is easy. In addition, for molded products that require high transferability on only one side, a lower injection pressure is required than before, so it is possible to reduce the thickness of the mold and use aluminum molds and resin molds, improving productivity and reducing costs. Produce the effect of.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view at the time of injection in an embodiment of an injection molding die and an injection molding apparatus including the same according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a state when a molded product is taken out in the device shown in FIG.

FIG. 3 is a cross-sectional view taken along line XX shown in FIG.

[Explanation of symbols]

 1 Fixed Side Mounting Plate 2 Fixed Side Type 3 Movable Side Type 4 Receiving Plate 5 Spacer Block 6 Cavity 7 Ejector Plate 8 Movable Side Mounting Plate 9 Core 11 Sprue Bushing 12 Guide Pin 13 Guide Pin Bushing 14 Sprue Lock Pin 15 Ejector Pin 16 Return Pin 17 Stop pin 18 Sprue 19 Runner 20 Gasket 21 Groove 22a, 22b Hole 23a, 23b Gas pressurization / suction port 24 Peripheral part 25 Gate

Claims (3)

[Claims] 1. A groove (21) is formed in a cavity (6), a sprue (18), and / or in both or one of the contact surfaces of the fixed side mold (2) and the movable side mold (3) on the parting surface.
A sealing member (20) which is formed except for the peripheral portion (24) of the resin flow path such as the runner (19) and the gate (25), and which keeps the area surrounding the cavity (6) airtight after the mold is closed. ) Is fixedly provided, a gas vent groove is formed in the peripheral edge portion (24) of the cavity (6), and holes (22a, 22b) are formed in the contact surface surrounded by the sealing member (20) excluding the peripheral edge portion (24). ) Is provided, and the hole (22
a, 22b) and gas pressurizing / suction port (23a, 2)
A mold for injection molding provided with 3b). 2. An injection molding apparatus equipped with the injection molding die according to claim 1, wherein the mold temperatures of the fixed side mold (2) and the movable side mold (3) are set with a constant difference, From the mold closing process to the injection / pressure-holding process, gas is sucked from the gas pressurizing / suction ports (23a, 23b) to bring the inside of the cavity (6) to a negative pressure state, and from the cooling process to the mold opening process. The gas pressurization / suction port (23
the cavity (6) by pumping gas from a, 23b)
An injection molding apparatus having a control unit for controlling the inside to be in a pressurized state. 3. The mold on the side for which the transferability is desired to be improved is maintained at a high temperature, and the mold on the opposite side is placed at a temperature higher than that of the mold on the high temperature side.
Maintaining a low temperature of 0 ° to 80 °, maintaining a negative pressure inside the cavity (6) from the mold closing stroke to the injection / pressure holding stroke, and pressurizing the cavity (6) from the cooling stroke to the mold opening stroke. Injection molding method.