TWI462817B - Mold for synthetic resin molding - Google Patents

Description

Synthetic resin molding mold

The present invention relates to a mold used for injection molding or compression molding of a thermoplastic resin or a thermosetting resin, and the like, and is a mold for molding a synthetic resin which alternately heats and cools the surface of a cavity.

As one of the appearance qualities of the damaged molded article, there is a problem that a weld line is generated. When the molten resin is filled into the mold, the weld line is generated in a portion where the resins flowing from different directions merge with each other at the front end. As a result of the formation of a solidified layer on the surface of the resin due to the contact of the molten resin at the front end with the surface of the cavity, even if the resin is completely filled and the holding pressure is applied, the surface of the mold cannot be sufficiently transferred to the cured layer of the resin merging portion, and becomes a micro V shape. The groove remains on the surface.

In addition, the term "appearance" as used herein means the surface state of the molded article, that is, the appearance of the molded article, and "good appearance quality" means that the surface of the molded article is good because the transfer from the surface of the mold to the cured layer of the resin is good. The design is excellent in appearance.

For example, when the molded article 1 having a plurality of openings 2 shown in FIG. 9 is formed by the conventional mold 3 shown in FIG. 17 and FIG. 18, it is filled from the gate 4 through the gate 5 to the cavity space via the gate 6. The molten resin of 7 is cut by the core portion 8 in which the opening portion 2 is formed, and since the resin merges from the core portion 8 on the downstream side in the resin flow direction, the weld line 9 shown in Fig. 19 is generated.

The material of the molded product was polycarbonate (transparent), and the molded article had a size of 100 mm in length × 50 mm in width × 1.2 mm in thickness, and the mold had one gate of the side gate.

In order to suppress the generation of the weld line, the molten resin is filled into the mold and the mold temperature is raised in advance when the holding pressure is applied after the filling, but the mold temperature is raised, and the corresponding cooling time requires a corresponding time, and as a result, the forming is performed. The cycle becomes longer. Further, since the molded article cannot be sufficiently cooled, defects are generated when the mold is released from the mold.

Therefore, various ways of heating the cavity surface of the mold only during filling of the molten resin into the mold are disclosed below.

A. Hot and cold water switching mode

In this manner, hot water and cold water are alternately flowed through the water pipe for mold temperature adjustment to adjust the temperature (see Patent Document 1, Patent Document 2, and Patent Document 3).

The advantage of this method is that it can be used in general-purpose molds, and the investment in the attached equipment is less.

The disadvantage of this method is that since the position of the water pipe for mold temperature adjustment is separated from the surface of the mold, the temperature rises and falls slowly, and since the upper limit of the heating temperature is 160 degrees Celsius, the resin having a high glass transition temperature cannot be sufficiently obtained. effect.

B. Hot and cold switching mode (steam heating type)

In this manner, the vapor and the cold water are alternately flowed through the mold temperature adjustment flow path to adjust the temperature (see Patent Document 4 and Patent Document 5).

The advantage of this method is that the surface temperature of the mold rises faster than hot water, and the temperature difference of the surface of the mold is small because the circuit through which the medium flows is dense.

The disadvantage of this method is that since the upper limit of the surface temperature of the mold is 155 degrees Celsius, the use of the resin is limited, and the production equipment such as the boiler or the medium switching device is very expensive, even if the sealing mold is used to seal the mold, it will rust, because it is ribbed. The portion supports the nested structure of the division, and therefore it is necessary to have a thickness for maintaining the strength of the mold, and it is not possible to arrange the flow path near the surface of the mold.

C. mold surface insulation method

In this method, a thin film heat insulating layer such as ceramic is provided on the surface of the mold, and the heat conduction between the resin and the mold is deteriorated to delay the cooling and solidification (see Patent Document 6).

The advantage of this method is that there is no need to introduce new production equipment, and because the surface is covered, there is no need to directly process the mold.

The disadvantage of this method is that since the rise of the mold surface temperature is small, the weld line does not disappear, the additional processing of the mold cavity can not be performed, and the mold surface temperature cannot be controlled.

D. High frequency induction heating method

This method causes a current to flow through an inductor coil located at a position close to the surface of the mold to generate a magnetic field, generates a current on the surface of the mold, and raises the temperature with Joule heat (refer to Patent Document 7).

The advantage of this method is that the surface of the mold can be sufficiently heated (or above 250 degrees Celsius), the temperature of the surface of the mold rises rapidly, and since it is heated from the outside, it is not necessary to process the mold.

The disadvantage of this method is that since the gap between the inductor coils cannot be heated, the temperature deviation of the surface of the mold is large, and it is impossible to produce an inductor coil that conforms to the shape of a complicated cavity, and since it cannot be heated in the forming step, The forming cycle becomes longer.

E. Radiation heating method

In this manner, the mold surface is irradiated with a halogen lamp in the mold opening (refer to Patent Document 8).

The advantage of this method is that the mold is not processed because it is irradiated from the outside.

The disadvantage of this method is that the temperature rise of the mold surface is time consuming and cannot correspond to the height difference of the mold surface.

F. Electric heating method

In this method, a mold in which an insulating layer is coated on a surface of a mold and then a conductive layer is coated thereon is used, and a direct electrode is provided to conduct electricity to generate heat (see Patent Document 9).

The advantage of this method is that the temperature rises faster, and the surface temperature of the mold becomes a high temperature (above 250 degrees Celsius), and the mold processing is hardly required.

The disadvantage of this method is that since the current passes through the shortest distance between the electrodes, it is not possible to uniformly heat up.

G.匣heater mode

In this method, the mold is heated by a crucible heater provided in a mold (see Patent Document 10 and Patent Document 11).

The advantage of this method is that the mold can be kept at a high temperature and is easy to set.

The disadvantage of this method is that the change of the mold temperature is time consuming (generally, the temperature cannot be adjusted in the forming cycle), the surface of the mold having the difference in height cannot be uniformly heated (because the crucible heater is not easily bent), and in order to reduce the difference in heating Increase the number of heaters.

Although either method has advantages and disadvantages, it is necessary to form a flow path for the cold and hot medium or a heater insertion hole in the manner in which the hot and cold medium flows through the mold or inserts the crucible heater into the mold, but Conventionally, the hole machining from the outer wall of the drill can only be provided with a straight flow path or a heater. Therefore, a uniform distance cannot be formed on the surface of the cavity having a three-dimensional shape with irregularities, and the surface temperature of the cavity cannot be uniformly heated.

In order to avoid the above problems caused by the limitation of the hole processing, it is also possible to divide the nest into a plurality of pieces to form a three-dimensional circuit. However, in order to prevent the leakage of the medium itself when the medium is a fluid, it is necessary to seal the entire flow path. However, since the sealing surface is a surface that cannot be abutted by the nesting, it is impossible to support the nesting and it is not possible to ensure sufficient mold strength. Further, if the cutting is performed here, if the cutting is performed on a surface of 4 mm or less from the surface of the cavity, another problem of machining deformation occurs.

When heated by a fluid, a temperature difference is created at the inlet and outlet of the circuit. Further, since the heater cannot be densely arranged during heating of the heater, there is a problem that temperature deviation occurs.

When a medium flow path having a width of 4 mm or more or a space portion required for the heater insertion hole is provided at a distance of 4 mm or less from the surface of the cavity, the cavity surface corresponding to the space portion is bent by the molding pressure of the resin in the mold, and thus A gloss deviation occurs on the surface of the resin molded article, and the appearance quality is defective.

In order to avoid the above problem, it is necessary to provide a space portion required for the medium flow path or the heater insertion hole at a position 4 mm or more from the surface of the cavity, but the cavity surface is due to the relationship between the distance from the heating medium to the cavity surface and the heat transfer. The temperature rise time is slower.

Since the weld line which causes the defect of the appearance of the molded article disappears, that is, the cosmetic coating for hiding the weld line is not required, the method for reducing the cost has been highly anticipated for many years.

As a solution to the above-described course, it is known to raise the surface temperature of the mold to a relatively high level so that the groove depth of the weld line becomes shallow, and then raise the temperature to the temperature inherent to the material to make the weld line disappear. However, when the temperature of the mold is kept at a high temperature, the surface of the molded article is soft from the mold, and the molded article is deformed. Therefore, it is necessary to set the temperature of the resin to be high during the filling of the resin and to maintain the pressure of the resin.

Therefore, the temperature adjustment technique for heating and cooling the surface of the mold in one cycle of the injection molding process has been proposed. However, various methods have been proposed, and there are disadvantages in that it cannot be used as a technique for determination.

Further, in the molding of the synthetic resin molded article, there is an important problem that, in addition to the problem of the appearance quality of the molded article, there is a problem of how to control the influence of the shrinkage state of the resin to the bending of the molded article in the molded article.

The bending control of the resin molded article is required to be made in a size that is exactly the same as the size of the design or the size within the tolerance (to avoid bending), and deliberate in a specific direction in consideration of the assembly workability of the molded article and other parts. Give a certain degree of bending (deliberately imparting bending).

As a method of improving the bending, it is known that the bending is generated in the same direction as the mold closing direction, and the two mold temperature adjusters are used to make the fixed mold and the movable mold have different temperatures to fix the mold forming surface and the movable mold forming surface. The difference in contraction adjusts the amount of bending.

However, in this method, since the entire mold is always in a state of temperature difference, there is a problem that the difference in thermal expansion of the mold causes scratches and breakage of the fixed mold and the movable mold. Therefore, the temperature difference in which the amount of bending can be sufficiently adjusted cannot be achieved. Further, there is no effective improvement method for the bending generated in the direction perpendicular to the mold closing direction, which is the current state of the art.

As described above, in the bending control of any of the conventional die technologies, it is not always necessary to carry out sufficiently and surely. Therefore, in the production line of the factory, it is necessary for the operator to personally apply the correcting operation to the molded product, and this freehand operation becomes an obstacle to the improvement of the production efficiency of the entire production line. Since the molded article exceeding the correction operation boundary is a defective product and has to be discarded, the shape of the molded article to be molded may have a very poor yield in the forming process.

As disclosed in Patent Document 12, the inventors of the present invention have proposed a synthetic resin molding die in which an electric heater is placed close to a surface of a cavity. However, research and development up to that time have been achieved to improve the appearance quality of a molded article. The bending control of the molded article cannot be achieved. The present invention has been completed based on the experience gained from subsequent research and development.

Patent Document 1: Japanese Patent Publication No. 09-314628

Patent Document 2: Japanese Patent Laid-Open No. Hei 10-100156

Patent Document 3: Japanese Patent Laid-Open No. Hei 11-115013

Patent Document 4: Japanese Patent Laid-Open Publication No. 2001-18229

Patent Document 5: Japanese Laid-Open Patent Publication No. 2002-316341

Patent Document 6: Japanese Laid-Open Patent Publication No. 2002-172655

Patent Document 7: Japanese Patent Laid-Open No. Hei 10-80938

Patent Document 8: Japanese Laid-Open Patent Publication No. 2000-238104

Patent Document 9: Japanese Laid-Open Patent Publication No. 04-265720

Patent Document 10: Japanese Patent Publication No. 08-230005

Patent Document 11: Japanese Laid-Open Patent Publication No. 2004-74629

Patent Document 12: Japanese Patent No. 4052600

An object of the present invention is to provide a mold for molding a synthetic resin which is not affected by the shape of the surface of the cavity, and can sufficiently close the electric heater to any portion of the surface of the cavity, so that the mold can be rushed without temperature rise deviation. When the temperature is raised to a desired temperature, the molding cycle does not become long, and the occurrence of the weld line can be surely prevented (improving the appearance quality), and the amount of shrinkage of the resin is adjusted for each portion of the molded article, whereby the bending control is surely performed.

(1) The mold for molding a synthetic resin of the present invention comprises a nest having a cavity space and a master mold supporting the nest, and a molten resin is filled into the cavity space to form a surface on which the cavity surface is transferred. The product is characterized in that the nesting of the mold is divided into a nested surface member having a cavity surface and a nested back member having no cavity surface, and the nested surface member is from the back of the nested surface member a side facing the surface of the cavity to form a groove passing through a portion near the surface of the cavity, and a rib is protruded in the nested back member, and an electric heater is received in the groove, when the nested table member and the nested back member are assembled Pressing the electric heater by the front end of the rib fitted to the groove to closely position the electric heater to the deepest part of the groove and divide the electric heater into a plurality of system settings; a flow path for a cooling medium that cools each nest by flowing cooling water; and is provided with cooling by the cooling water and by the electric heating During the entire forming cycle of the pressure-maintaining cooling step of heating, the controllers of the respective systems are individually energized to control the controllers for different temperature control of the respective control regions; the cavity and the parts of the molded article Corresponding to the shape or thickness, the plurality of control regions are divided into temperature differences; the controller portion suppresses the molding in the control region when the molten resin filled in the cavity of the mold cavity is cooled and solidified The heating temperature of the electric heater in the region where the product is contracted is lower than the region where the shrinkage of the molded article is promoted, or the heating temperature of the electric heater in the region where the shrinkage of the molded article is promoted is smaller than the region where the shrinkage of the molded article is suppressed. High; the temperature difference between the control regions is set to simultaneously adjust the temperature difference between the bending generated in the mold closing direction of the molded article and the bending generated in the vertical direction, and the heating temperature is set to prevent the welded wire of the molded product The temperature produced.

(2) The mold for molding a synthetic resin according to the above item (1), wherein the electric heater is a thin tube heater having a diameter of 4 mm or less having a high degree of freedom of deformation.

The groove for accommodating the electric heater may be formed in a plurality of spiral or rotating shapes as shown in FIG. 6 and FIG. 7 except that a plurality of linear or curved shapes are formed side by side, and along the groove. It is also possible to impart a high or low direction to the traveling direction or to form a three-dimensional bending. In the example shown in FIG. 4, a plurality of slots for the electric heaters are all disposed at the same level, but as shown in FIG. 8 or FIG. 10, part or all of the slots for the electric heater are corresponding to the shape or thickness of the molded article. It can also be placed at different levels.

As shown in Fig. 11, the molding cavity is divided into a plurality of heating regions to be given a temperature difference corresponding to the shape or thickness of each portion of the molded article. The electric heater is arranged in a plurality of systems in units of the heating area, and each system The electric heater appropriately changes the current amount of energization, the energization time, and the timing of energization start and energization stop according to the setting of the controller unit to control the heating amount, the heating rate, and the temperature rise gradient.

In the above-mentioned item (1), the mold for molding a synthetic resin according to the invention is characterized in that the nesting of the mold is divided into a nested surface member having a cavity surface and a nested back member having no cavity surface, and a tank for housing the electric heater. The nesting surface member is formed by cutting from the back side of the nested surface member toward the surface of the cavity, and thus is different from the conventional method of linearly perforating the filling hole of the crucible heater from the side surface of the mold. It is not affected by the shape of the surface of the cavity, that is, in the case where the surface of the cavity has a step portion or a concave portion or a curved portion, the groove is cut along the step portion or the concave portion or the curved portion, thereby forming a mold The specific shape corresponding to the specific shape of the cavity surface corresponds to the distance between the surface of the cavity and the groove at any position along the longitudinal direction of the groove.

Further, a rib is protruded from the nested back member, and an electric heater is housed in the groove. When the nested surface member and the nested back member are assembled, the electric heater is pressed by the front end of the rib fitted to the groove, and the electric heater is used. By positioning in the tightest state and holding it at the deepest part of the groove, the same heat transfer distance is set at any part of the cavity surface, so that it can be rapidly and uniformly heated to a desired temperature without a temperature rise deviation.

As described above, the nested surface member and the nested back member of the mold are rapidly heated without the temperature rise deviation, and are maintained at a desired high temperature, so that the resin surface of the portion where the resin flowing from the different directions merges with each other does not form a solidification. The layer can surely prevent the occurrence of weld lines and improve the appearance quality of the molded article.

According to the above (1), the synthetic resin molding die of the invention can be The surface temperature of the cavity is at a temperature of 250 degrees Celsius or higher, and can be rapidly heated to a temperature above the glass transition temperature of the synthetic resin. Further, by making the setting density of the electric heater dense, it is possible to prevent the deviation of the surface temperature of the cavity. The special equipment other than the power supply unit is not required, and the entire molding apparatus can be constructed at a low price. Since the thickness of the nest can be arbitrarily determined, the necessary mold strength can be maintained. Moreover, since the heating and cooling medium are not used, the rust resistance is also strong.

Further, the groove for accommodating the heater can be opened by separating the nested table member from the nested back member, so that the repair or replacement of the electric heater can be easily performed.

Further, in the above-mentioned (1), the mold of the invention is provided, and a plurality of electric heaters are provided in the mold, and the molding cavity is divided into a plurality of temperatures to be given a temperature difference depending on individual shapes such as the shape or thickness of the molded article. In the heating zone, the electric heaters of the system for processing each heating zone are operated according to the conditions of the controller section. Therefore, each heating zone can be controlled to be heated to an optimum temperature state, thereby avoiding bending or intentionally imparting bending in a desired direction. In addition to improving the appearance quality, the amount of molding shrinkage can be adjusted for each part to easily and surely perform bending control.

The advantages of the mold of the invention described in the above item (1) can be summarized as follows.

(a) Different temperature control is performed in a unit by a plurality of electric heaters, and individual control of the movable mold and the fixed mold can of course be achieved, and temperature control can be partially performed even in each mold.

(b) Since the electric heater is directly disposed in the nesting, the temperature control can be continuously performed throughout the forming cycle including the pressure maintaining cooling.

(c) The forming shrinkage can be adjusted by the temperature difference portion of the cavity surface.

(d) Increasing the temperature difference of the cavity surface using a region above the glass transition temperature.

(e) In the portion where the forming shrinkage is large, the surface temperature of the cavity is lowered, and at the portion where the forming shrinkage is small, the surface temperature of the cavity is raised, thereby eliminating the difference in forming shrinkage to eliminate unnecessary bending.

(f) The bending can be generated in the opposite direction by adjusting the temperature difference, and the bending is adjusted (deliberately imparting bending) in consideration of the assembly state when the molded article is combined with other components.

(g) It is possible to control the bending which is not achievable by the conventional method and which is perpendicular to the direction of the closed mold.

(h) The bending of the simultaneous closing direction of the mold and the direction perpendicular to the vertical direction can be simultaneously adjusted by the condition of the surface temperature of the cavity.

In the mold for molding a synthetic resin according to the above aspect (2), the electric heater is configured by a thin tube heater having a diameter of 4 mm or less having a high degree of freedom of deformation. Therefore, even if the surface shape of the cavity is three-dimensional and the height is different, the electric heater can be used. The bending is inserted into the groove, so that the groove depth can be adjusted according to the shape of the cavity surface, and the surface of the three-dimensional cavity can be heated to a uniform temperature or an arbitrary temperature.

Since the electric heater can be bent, the shape of the molded product can be heated in a wide range of electric heaters at a low price.

Since the electric heater is easily bent, it can be disposed at a portion having a height difference and a free curved surface and a side surface, and can be disposed at a uniform distance from the surface of the mold.

The above and other features and advantages of the present invention will become more apparent from the written description.

Hereinafter, the details of the embodiments of the present invention will be further described, but the present invention is not limited thereto. In addition, the same elements in the respective drawings are denoted by the same reference numerals.

1 to 7 show an embodiment of the invention according to the above item (1), and the mold 10 is formed of a fixed mold 11 and a movable mold 12 in the same manner as a known mold for molding a resin (in addition, other moldings connected to the mold 10) The illustration of the device section is omitted).

This mold 10 is used to form a flat plate-like molded article of the molded article 1 shown in Fig. 9, and thus the cavity space 25 is formed into a flat space.

The fixed mold 11 is constituted by a female mold 13 and a nest, and the nesting system is divided into a nested watch member 15 and a nested back member 16. The movable mold 12 is constituted by a female mold 14 and a nest, and the nesting system is divided into a nested watch member 17 and a nested back member 18.

On the flat surface of the nested surface member 15 of the fixed mold 11, recesses of the same depth are formed in the width direction, and the recess is closed by the flat underside of the nested surface member 17 of the movable mold 12 (corresponding to the portion of the cavity surface 29). At the time of the portion, the cavity space 25 is formed.

In the nested surface member 15 of the fixed mold 11, from the flat lower side, that is, the side opposite to the cavity surface 28 toward the cavity surface 28, the opposing cavity surface 28 is formed at equal intervals, parallel to each other and the same depth. A plurality of slots 19 at right angles. In the nested surface member 17 of the movable mold 12, from the flat upper side, that is, the surface opposite to the cavity surface 29, toward the cavity surface 29, A plurality of grooves 20 are formed at right angles to the cavity surface 29, parallel to each other and at the same depth.

On the flat upper side of the nested back member 16 of the fixed mold 11, a plurality of ribs 23 are formed at equal intervals and in parallel with each other, and the ribs 23 are disposed at the same interval as the groove 19, and the width of the rib 23 is the same as described above. The groove 19 is completely fitted, and the protruding length of the rib 23 is set to be shorter than the depth of the groove 19 by the outer diameter of the heater 21. Therefore, when the nested table member 15 of the fixed mold 11 and the nested back member 16 are assembled, the electric heater 21 pressed to the front end of the rib 23 is positioned and held at the deepest portion of the groove 19.

A straight line drawn by connecting the deepest portions of the grooves 19 to each other is parallel to the cavity surface 28, and the distance between each of the electric heaters 21 and the cavity surface 28 accommodated therein is preferably set to be 4 mm or less.

As described above, by bringing the electric heater 21 into close contact with the nested watch member 15 of the fixed mold 11, the heat of the electric heater 21 is easily conducted to the nested watch member 15.

On the flat lower side of the nested back member 18 of the movable mold 12, a plurality of ribs 24 are formed at equal intervals and in parallel with each other, and the ribs 24 are disposed at the same interval as the groove 20, and the width of the rib 24 is the same as described above. The groove 20 is completely fitted to the size, and the protruding length of the rib 24 is set to be shorter than the depth of the groove 20 by the outer diameter of the electric heater 22. Therefore, when the nested table member 17 of the movable mold 12 and the nested back member 18 are assembled, the electric heater 22 pressed to the front end of the rib 24 is positioned and held at the deepest portion of the groove 20.

The straight line drawn by connecting the deepest portions of the grooves 20 to each other is parallel to the cavity surface 29, and the distance between each of the electric heaters 22 and the cavity surface 29 accommodated therein is preferably set to be 4 mm or less.

As described above, by bringing the electric heater 22 into close contact with the nested table member 17 of the movable mold 12, the heat of the electric heater 22 is easily conducted to the nested table member 17.

Further, as will be described later, the electric heaters 21 and 22 are divided into a plurality of systems, and the electric power supplied to each system is individually controlled.

Fig. 8 is a view showing another embodiment of the invention according to the above (1), wherein the mold is formed of a fixed mold and a movable mold, similarly to the known mold for molding a resin. Further, only the nested portion is illustrated, and the illustrations other than the nested portion and the other portions of the forming device connected to the mold are omitted.

The mold is used to form a curved plate-shaped molded article, so that the cavity space 25 is formed as an upward convex curved space.

The fixed mold is constituted by a master mold and a nest, and the nest system is divided into a nested watch member 15 and a nested back member 16. The movable mold is constituted by a master mold and a nest, and the nesting system is divided into a nested watch member 17 and a nested back member 18.

The concave portion at the center of the upper surface of the nested surface member 15 of the fixed mold is formed with the same depth in the width direction, and the concave portion is closed by the curved cavity surface 29 at the lower central portion of the nested surface member 17 of the movable mold. At this time, the above-described cavity space 25 is formed.

In the nested surface member 15 of the fixed mold, a plurality of grooves 19 are formed at equal intervals and parallel to each other in the upward direction from the flat lower side, that is, the surface opposite to the cavity surface 28 toward the cavity surface 28.

The depth of the grooves 19 is set so that the curved line drawn when the deepest portions of the grooves 19 are connected to each other is a curved line parallel to the cavity surface 28 of the cavity. That is, the distance between the groove 19 and the cavity surface 28 is plural The slots 19 are all formed in the same manner.

The distance between each of the electric heaters 21 housed in each of the grooves 19 and the cavity surface 28 is preferably set to be 4 mm or less. As described above, by bringing the electric heater 21 into close contact with the nested watch member 15 of the fixed mold, the heat of the electric heater 21 is easily conducted to the nested watch member 15.

In the nesting table member 17 of the movable mold, a plurality of grooves 20 are formed at equal intervals and parallel to each other in the downward direction from the flat upper side, that is, the surface opposite to the cavity surface 29 toward the cavity surface 29.

The depth of the grooves 20 is set so that the curved line drawn when the deepest portions of the grooves 20 are connected to each other is a curved line parallel to the cavity surface 29. That is, the groove 20 is formed in such a manner that the shortest distance between the groove 20 and the cavity surface 29 is the same in all of the plurality of grooves 20.

On the flat upper side of the nested back member 16 of the fixed mold, a plurality of ribs 23 are formed at equal intervals and parallel to each other, and the ribs 23 are disposed at the same intervals as the above-mentioned grooves 19, and the width of the ribs 23 is the same as the above-mentioned grooves 19 fully fitted size.

The protruding length of the ribs 23 is set so that the bending line drawn when the front ends of the ribs 23 are connected to each other is a bending line parallel to the cavity surface 28 of the cavity. That is, the rib 23 is formed in such a manner that the shortest distance between the rib 23 and the cavity surface 28 is the same in all of the plurality of ribs 23.

In any of the ribs 23, the protruding length of the ribs 23 is set to be shorter than the depth of the above-mentioned groove 19 at the corresponding position by the outer diameter of the electric heater 21. Therefore, when the nested table member 15 of the fixed mold and the nested back member 16 are assembled, the electric heater 21 extruded to the front end of the rib 23 is positioned and held in the above groove. The deepest part of 19.

The distance between each of the electric heaters 21 housed in each of the grooves 19 and the cavity surface 28 is preferably set to be 4 mm or less.

As described above, by bringing the electric heater 21 into close contact with the nested watch member 15 of the fixed mold, the heat of the electric heater 21 is easily conducted to the nested watch member 15.

On the flat lower side of the nested back member 18 of the movable mold, a plurality of ribs 24 are formed at equal intervals and parallel to each other, and the ribs 24 are disposed at the same interval as the groove 20, and the width of the rib 24 is the same as the above groove 20 fully fitted size.

The protruding length of the ribs 24 is set such that the bending line drawn when the front ends of the ribs 24 are connected to each other is a bending line parallel to the cavity surface 29. That is, the ribs 24 are formed in such a manner that the shortest distance between the ribs 24 and the cavity surface 29 is the same in all of the plurality of ribs 24.

In either of the ribs 24, the protruding length of the rib 24 is set to be shorter than the depth of the groove 20 at the corresponding position and the outer diameter of the electric heater 22. Therefore, when the nested table member 17 of the movable mold and the nested back member 18 are assembled, the electric heater 22 pressed to the front end of the rib 24 is positioned and held at the deepest portion of the groove 20.

The distance between each of the electric heaters 22 housed in each of the grooves 20 and the cavity surface 29 is preferably set to be 4 mm or less.

As described above, by bringing the electric heater 22 into close contact with the nested table member 17 of the fixed mold, the heat of the electric heater 22 is easily conducted to the nested table member 17.

Further, as will be described later, the electric heaters 21 and 22 are divided into a plurality of systems, and the electric power supplied to each system is individually controlled.

Fig. 10 is a view showing still another embodiment of the invention according to the above item (1), in which the mold 10 is constituted by a fixed mold 11 and a movable mold 12. The illustration of the other forming device portions connected to the mold 10 is omitted.

This mold 10 is formed into a long rod-shaped molded article having a section in the width direction which is thickest on the one side and has a thickness in the opposite side as shown in the longitudinal direction of the width direction of Fig. 11 . The narrow portion 1a and the wide portion 1b are cut by the opening portion in the vertical direction of the longitudinal section in the width direction.

The fixed mold 11 is constituted by a female mold 13 and a nest, and the nesting system is divided into a nested watch member 15 and a nested back member 16. The movable mold 12 is constituted by a female mold 14 and a nest, and the nesting system is divided into a nested watch member 17 and a nested back member 18.

On the flat upper surface of the nested surface member 15 of the fixed mold 11, a projection corresponding to the opening of the molded article 1 is formed, and the flat portion of the nested surface member 17 of the movable mold 12 is formed to correspond to the above-mentioned portions 1a, 1b. The recessed portion forms a cavity space 25 when the fixed mold 11 and the movable mold 12 are closed.

Below the flatness of the nested watch member 15 of the fixed mold 11, a plurality of grooves 19 which are at right angles to the cavity space 25 are formed at equal intervals, parallel to each other and at the same depth. On the flat upper side of the nested watch member 17 of the movable mold 12, a plurality of grooves 20 which are formed at right angles to the cavity space 25 are formed at equal intervals and in parallel with each other. The depth of the grooves 20 is set according to the cross-sectional shape of the cavity space 25.

On the flat top surface of the nested back member 16 of the fixed mold 11, a plurality of ribs 23 are formed at equal intervals and parallel to each other, and the arrangement interval of the ribs 23 is formed. Similarly to the above-described groove 19, the width dimension of the rib 23 is completely fitting with the groove 19, and the protruding length of the rib 23 is the same, and is set to be shorter than the depth of the groove 19 by the outer diameter of the electric heater 22. Therefore, when the nested table member 15 of the fixed mold 11 and the nested back member 16 are assembled, the electric heater 22 pressed to the front end of the rib 23 is positioned and held at the deepest portion of the groove 19.

A straight line drawn by connecting the deepest portions of the grooves 19 to each other is parallel to the inner surface of the cavity space 25, and the distance between each of the electric heaters 22 and the cavity space 25 accommodated therein is preferably set to be 4 mm or less. .

As described above, by bringing the electric heater 22 into close contact with the nested watch member 15 of the fixed mold 11, the heat of the electric heater 22 is easily conducted to the nested watch member 15.

A plurality of ribs 24 are formed at equal intervals and parallel to each other at a flat bottom of the nested back member 18 of the movable mold 12. The ribs 24 are disposed at the same interval as the groove 20, and the width of the rib 24 is the same as the groove. The size of the 20 fully fitted, the protruding length of the rib 24 corresponds to the shape of the cavity space 25 to give a difference in length. The length of each rib 24 is set to be shorter than the depth of the groove 20 by the outer diameter of the electric heater 21. Therefore, when the nested table member 17 of the movable mold 12 and the nested back member 18 are assembled, the electric heater 21 pressed to the front end of the rib 24 is positioned and held at the deepest portion of the groove 20.

A straight line drawn by connecting the deepest portions of the grooves 20 to each other is parallel to the inner surface of the cavity space 25, and the distance between the respective electric heaters 21 and the inner surface of the cavity space 25 is preferably set. Below 4mm.

As described above, by bringing the electric heater 21 into close contact with the nested table member 17 of the movable mold 12, the heat of the electric heater 21 is easily conducted to the nested table member 17.

In any embodiment, the electric heaters 21, 22 are in accordance with the shape of the molded article 1. The individual specific forms such as the thickness are set in a plurality of systems, and the electric power supplied to the electric heaters 21, 22 of the respective systems is regulated by a control device such as a variable transformer or a thyristor provided in each system of the controller unit 40. Output, using the mold closing signal of the injection molding machine and the timer to make the forming cycle and action.

In addition to the mold temperature adjuster that adjusts the temperature of the entire mold 10, the cooling medium flow path 26 is provided in the nested back member 16 of the fixed mold 11, and the cooling medium flow path 27 is provided in the nested back member 18 of the movable mold 12, so The circuit through which the cooling water flows is connected to the cooling medium flow paths 26 and 27, and the cooling water is opened and closed by the electromagnetic valve, so that the cooling of each nest can be performed at any time. The heating time can be controlled not only by a timer, but also by adjusting the temperature of the mold surface by assembling the temperature sensor to the mold.

Even if the thickness of each of the nested table members 15, 17 is a sufficient thickness of 4 mm or more, the heaters 21, 22 can be provided at any groove depth. Therefore, sufficient mold strength can be obtained, and deformation does not occur during machining.

The heat transfer time can be shortened by making the inner surface of each of the cavities 25 and the bottom of the grooves 19, 20 of the nesting table members 15, 17 abutting the surfaces of the electric heaters 21, 22 4 mm or less. The surface temperature of the cavity can be raised to a predetermined temperature in a short time. This can also be achieved when the amount of heat energy required for the temperature rise is small, and the cooling of the cavity 25 can be achieved relatively quickly. The grooves 19, 20 of the nested table members 15, 17 described above are not to be 4 mm or less in the width of the curved groove due to the resin pressure in the mold. Each of the nested table members 15 and 17 does not require a space other than the installation grooves 19 and 20 of the electric heaters 21 and 22, and since it is strong as a mold structure, no countermeasure against reinforcement is required.

After the heaters 21, 22 are disposed in the slots 19, 20 of the nested table members 15, 17 described above, the piezoelectric heaters 21, 22 are tightened by the ribs 23, 24 of the nested back members 16, 18 described above. In order to adhere to each of the nested surface members 15, 17 described above, there is no heat transfer loss, and the temperature of the cavity surface can be raised with high efficiency.

By using a plurality of electric heaters 21, 22 having different control loops, different temperature control can be performed separately, and the appearance quality of the molded article can be adjusted.

When the diameter of the electric heaters 21, 22 is 4 mm or less, the distance between the heaters can be densely arranged, and the surface temperature of the cavity can be made uniform. Moreover, even a curved portion or a portion having a height difference can be simply bent and inserted by hand.

According to the above-described in-mold heater setting method of the present invention, the mold temperature can be raised and lowered in a short time, and the curing of the resin can be delayed in the resin flow and the holding pressure. This is because it is not only an effect of improving the appearance quality of the molded article, but also an improvement in fluidity of the resin, so that a molded article having a conventionally insufficient thickness can be formed.

Moreover, this effect can obtain the same effect in addition to resin injection molding, and is effective in all the forming processes of the mold for the purpose of cooling and solidifying by using a molten molten fluid.

(Experimental example of improvement in appearance quality of molded article)

The experimental mold 10 of the molded article 1 shown in Fig. 9 was produced in the same manner as in Fig. 1, and Fig. 13 is a graph showing the representative value of the temperature change when the heater output 1300 W to heat the surface of the cavity. The material of the molded article 1 is polycarbonate (transparent), and the molded article has a size of 100 mm in length × 50 mm in width × 1.2 mm in thickness, and the mold has one gate of the side gate.

From the mold temperature regulator, water of 90 degrees Celsius is passed through the mold to adjust the temperature to the electric heater (outer tube diameter: 1.6 mm, heat per unit length: 975 W/m, manufacturer: Okazaki Co., Ltd., Form: H35 Micro Heater) Heating for 15 seconds raises the cavity surface temperature to 175 degrees Celsius.

Further, in the present experimental example, since the shape of the molded article 1 is a flat shape, the focus is placed on the improvement of the appearance quality, and the heating of the electric heater is uniformly performed in each part, and the bending control is not verified. Therefore, the present invention is a conventional example.

One cycle of forming is performed as follows.

(1) At the same time as the start of mold opening, the electric heater is energized to start heating.

(2) The molded article is taken out from the mold at the same time as the heating of the electric heater, and the mold is closed.

(3) After the mold closing is completed, the mold is subjected to the injection of the molten resin, and the holding pressure is applied. The heating of the electric heater is performed at the stage of closing the mold or at any time until the end of the pressure maintaining step.

(4) After the pressure holding step, the cooling water solenoid valve is opened after the cooling step is started, and the cooling water flows through the nested cooling water pipe to lower the temperature to the state before the heating starts.

(5) One cycle of forming ends and returns to (1).

In this experimental example, the surface of the cavity is 175 degrees Celsius, which is higher than the glass transition temperature of the molding resin (144 degrees Celsius in polycarbonate), so that even if the molten resin is in contact with the surface of the cavity, it will not be completely cured, and the fusion welding can be suppressed. The effect of the line.

If a molded article formed by a conventional method is measured by a laser microscope For the weld line, the depth of the weld line is about 5 μm, and the width of the weld line is about 15 μm. However, if the mold is used in this experimental example, the state of the weld line cannot be measured even by a laser microscope.

(Experimental example of performing appearance quality improvement forming and bending control forming)

Since the mold of the present invention has a structure in which an electric heater as a heat source is directly disposed in the mold, temperature control can be performed not only at the time of injection but also during pressure-holding cooling. Further, since a plurality of heaters independently perform temperature control, if a temperature difference is given in the forming step, the amount of bending changes.

The molded article shown in Fig. 12, which is formed by the mold shown in Fig. 10, is simultaneously subjected to the embodiment of the present invention without fusion forming (appearance quality improvement molding) and bending control molding. The molded article has a shape of 168 mm in length, 7.5 mm in width, and 0.7 to 2.2 mm in thickness, and has gates of two side gates at two ends of the long side, and the molding resin is PMMA (polymethyl methacrylate) resin.

In the longitudinal cross-sectional view in the width direction of Fig. 11, the 1a portion having a width of 1.6 mm and the 1b portion having a width of 3.2 mm are subjected to cooling from the four sides including the side surface, thereby constituting one half of the molded article as a whole. the above.

This point is analyzed by CAE. Part 1a is solidified at a high pressure due to the cooling effect from the four sides, so that the shrinkage is less. The 1b portion is wider than the 1a portion, so that even if there is cooling from the side surface, the curing is slow, and the shrinkage is obtained. . Therefore, it is predicted that the bending caused by the difference in contraction between the two portions 1a, 1b is caused. Therefore, using the temperature control of the electric heaters 21, 22, try two parts 1a, 1b The difference in shrinkage is improved.

First, a normal molding was performed with the completed mold, and a bending of 0.3 mm was generated in the bending direction + side of Fig. 16 to obtain a result of matching with the CAE analysis. Next, the electric heaters 21, 22 shown in Fig. 10 are divided into four heating zones (1), (2), (3), and (4) as shown in Fig. 11, and the conditions are changed by the setting of the controller section. Change to the heating zone (1) and the heating zone (3) to accelerate the cooling and solidification at a lower temperature to suppress the shrinkage, and the heating zone (2) and the heating zone (4) are delayed to cool and solidify at a higher temperature to promote shrinkage and shift the bending. Finally, the amount of bending can be made 0mm. One cycle of forming is substantially the same as the above experimental example.

Figure 14 is a graph showing the relationship between the cavity surface temperature recording and the forming step. The graph of Figure 15 shows the measured values of the cavity surface temperature records for each control zone. This makes it possible to simultaneously adjust the temperature difference between the bending generated in the mold closing direction and the bending in the vertical direction while maintaining the high temperature required for the non-welding (improvement in appearance quality). Further, by making the temperature difference reversed, it was confirmed that the bending was caused in the bending direction side of Fig. 16 .

The present invention has been described with reference to the embodiments of the present invention. However, the present invention is not limited by the scope of the invention.

The present application claims priority on Japanese Patent Application No. 2009-119318, filed on Jan.

10‧‧‧Mold

11‧‧‧Fixed mould

12‧‧‧ movable mold

13‧‧‧Mother of fixed molds

14‧‧‧Mother of movable molds

15‧‧‧Folding table components for fixed molds

16‧‧‧Folding backing members of fixed molds

17‧‧‧ Nested table members of movable molds

18‧‧‧Chasing back member of movable mold

19‧‧‧Slots of nested table members for fixed molds

20‧‧‧Slots of nested table members of movable molds

21‧‧‧Electrical heaters for fixed molds

22‧‧‧Electrical mold heater

23‧‧‧Fixed ribs of nested back members

24‧‧‧ ribs of nested back members of movable molds

25‧‧‧ cavity space

26‧‧‧Flow path for cooling medium for fixed mold

27‧‧‧Flow path for cooling medium of movable mold

28‧‧‧ cavity surface

29‧‧‧ cavity surface

40‧‧‧Electric controller controller

Fig. 1 is a schematic longitudinal cross-sectional view showing a mold for molding a synthetic resin according to an embodiment of the present invention.

Figure 2 is a front elevational view showing the separated state of the nested portion of the mold of Figure 1.

Figure 3 is a longitudinal cross-sectional view showing the separated state of the nested portion of the mold of Figure 1.

Figure 4 is a longitudinal cross-sectional view showing the assembled state of the nested portion of the mold of Figure 1.

Figure 5 is a plan view of the nested watch member of the movable mold in the mold of Figure 1.

Figure 6 is a bottom plan view of the nested watch member of Figure 5.

Figure 7 is a right side view of the nested table member of Figure 5.

Fig. 8 is a longitudinal cross-sectional view showing an assembled state of a nested portion in a mold for molding a synthetic resin according to another embodiment of the present invention.

Fig. 9 is a plan view of a molded article formed by the mold of Fig. 1.

Fig. 10 is a schematic longitudinal cross-sectional view showing a mold for molding a synthetic resin according to still another embodiment of the present invention.

Fig. 11 is a longitudinal cross-sectional view in the width direction of a molded article formed by the mold of Fig. 10, together with a heating temperature range of each control region.

Fig. 12 is a front view of a molded article formed by the mold of Fig. 10.

Fig. 13 is a graph showing the relationship between the cavity surface temperature recording and the forming step in the experiment of improving the appearance quality of the mold of Fig. 1.

Fig. 14 is a graph showing the relationship between the cavity surface temperature recording and the forming step in the experiment of improving the appearance quality and bending control of the mold of Fig. 10.

Fig. 15 is a graph showing the cavity surface temperature recording of each control region in the experiment of improving the appearance quality and bending control of the mold of Fig. 10.

Fig. 16 is a front view showing a molded article showing a reference in the bending direction.

Fig. 17 is a schematic plan view of a mold for molding a synthetic resin of a conventional method.

Figure 18 is a schematic longitudinal cross-sectional view of the mold of Figure 17.

Fig. 19 is a plan view showing a molded article formed by the mold of Fig. 17.

10. . . Mold

11. . . Fixed mold

12. . . Movable mold

13. . . Fixed mold master

14. . . Master mold of movable mold

15. . . Fixed mold nesting table member

16. . . Fixed mold nesting back member

17. . . Nested table member of movable mold

18. . . Nested back member of movable mold

19. . . a slot for a nested table member of a fixed mold

20. . . Slot of nested table member of movable mold

twenty one. . . Fixed mold heater

twenty two. . . Movable mold heater

twenty three. . . The rib of the nested back member of the fixed mold

twenty four. . . Rib of the nested back member of the movable mold

25. . . Cavity space

26. . . Cooling medium flow path for fixing mold

27. . . Flow path for cooling medium of movable mold

28. . . Cavity surface

29. . . Cavity surface

40. . . Controller unit of electric heater

Claims (2)

A mold for molding a synthetic resin, which is formed by a nest having a cavity space and a master mold supporting the nest, and a molten resin is filled into the cavity space to form a molded article on which a cavity surface is transferred, which is characterized in that : nesting the mold into a nested surface member having a cavity surface and a nested back member having no cavity surface, from the back side of the nested surface member toward the cavity The surface forms a groove passing through a portion near the surface of the cavity, and a rib is protruded in the nested back member, and an electric heater is accommodated in the groove, and the nested surface member and the nested back member are assembled by fitting Extruding the electric heater at a front end of the rib of the groove to closely position the electric heater to the deepest portion of the groove and distinguishing the electric heater into a plurality of system settings; the nesting is arranged to flow cooling water a cooling medium flow path for cooling each nest; the entire molding cycle including a pressure-maintaining cooling step including cooling by the cooling water and heating by the electric heater Electric heaters are individually controlled a controller portion for performing different temperature control on each control region; the cavity is divided into a plurality of control regions to be given a temperature difference corresponding to the shape or thickness of each portion of the molded article; the controller portion is When the molten resin filled in the cavity space of the mold is cooled and solidified, in the control region, the heating temperature of the electric heater in the region where the shrinkage of the molded article is suppressed is lower than the region where the shrinkage of the molded article is promoted, or The heating temperature of the electric heater in the region where the shrinkage of the molded article is promoted is higher than the region in which the shrinkage of the molded article is suppressed; The temperature difference between the control regions is set to simultaneously adjust the temperature difference between the bending generated in the mold closing direction of the molded article and the bending generated in the vertical direction, and the heating temperature is set to prevent the weld line of the molded article from being generated. temperature. The mold for molding a synthetic resin according to the first aspect of the invention, wherein the electric heater is a thin tube heater having a diameter of 4 mm or less having a high degree of freedom of deformation.