JPH10315268A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for injection molding with an easy undercut treating mechanism. SOLUTION: In the mold used for a method for simultaneously injection molding and decorating comprising the first step of supplying a decorating sheet onto a movable mold of a pair of injection molds having a fixed mold A and the movable mold B and then fixing the sheet by a frame 23 at four sides of a periphery of a cavity of the mold, the second step of clamping both the molds and injecting resin, and the third step of moving part of the fixed mold laterally to the moving direction of the movable mold after the resin is solidified and then releasing a product from the fixed mold to be sequentially executed, a slide core 3 of part of the fixed mold sliding laterally by a hydraulic cylinder 4 for an undercut 2 has a structure that the sheet is fixed at lateral position by the frame for fixing the sheet at four sides at the time of clamping the molds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold used in a simultaneous painting method for injection molding. In particular, the present invention relates to an injection mold used when a molded product has an undercut.

[0002]

2. Description of the Related Art Injection molding simultaneous painting method is an excellent method for painting a three-dimensional molded product surface since a laminated or transfer type painted sheet is formed and formed along the surface of the molded product. . Here, an example of the simultaneous injection molding painting method will be described with reference to FIGS.

FIG. 7 shows a state before a painting sheet is supplied between dies. The type A is a male type and is a fixed type to be attached to a fixed side die plate. (Note that in order to avoid complication, peripheral devices that are not essential for the description, such as a die plate, are not shown in these drawings.) Type B is a female type and is a movable type that is attached to a movable side die plate. is there. The leading end of the continuous band-shaped picture sheet S unwound from the roll R is
1 is a state of being gripped from both sides. Then, from this state, the painted sheet is supplied between the pair of molds A and B to be in a state after the supply of the painted sheet in FIG. That is, the conveyance chuck 21 moves downward while holding the painting sheet S, and conveys the painting sheet to a position where the fixed chuck 22 located below the outside of the mold can grasp the leading end of the painting sheet. When the fixed chuck 22 completes the gripping of the front end of the painting sheet, the transport chuck 21 releases the grasping of the painting sheet, moves upward outside the mold, returns to the original position, and moves the painting sheet to the mold B in preparation for the next shot. Grip on the upstream side of. Next, the clamp 23 always located between the dies is moved forward (to the left in the drawing) toward the dies B by a driving mechanism such as an air cylinder, so that the painted sheet is pressed against and fixed to the parting surface of the dies B. As a result, the supply of the painting sheet between the molds is completed. The clamp 23 is a frame having a frame shape as shown in FIG. 11 so as to surround the four sides around the cavity of the mold B and press the painted sheet. The inside of the frame of the clamp 23 is usually substantially rectangular as shown in FIG. 4 of clamp 23
A sliding rod 29 is connected to the corner, and the sliding rod is slidably fitted into the mold B and connected to a drive source (not shown) such as a fluid pressure cylinder provided behind the parting surface of the mold B. Is driven.

[0004] When performing vacuum forming (preliminary forming) of a painted sheet, first, a hot platen 24 as a heat source for heating and softening the painted sheet is inserted from the retracted position outside the mold to between the opened molds. , To the position facing the painted sheet to be heated. This state is shown in FIG. Next, as shown in Fig. 9,
First, the softened sheet S is heated and softened. The hot platen 24 moves forward (to the left in the drawing) and moves to a position where it contacts the clamp 23. Then, the heating surface of the hot platen is separated from the painting sheet by a predetermined distance to heat the painting sheet. In addition, at the same time as the hot platen moves to the heating position, in the same figure, a cutter 25 made of a heating wire such as a nichrome wire provided over the hot plate comes into contact with the painting sheet, and the continuous strip-like painting sheet is formed. Cut to the size of one shot. The parting surface of the mold B is provided with a receiving groove 26 on a surface portion facing the cutter 25 so as not to interfere with the cutter. For the purpose of heating and softening the painted sheet, as shown in FIG. 9, in addition to the non-contact type heat plate which heats the painted sheet by radiant heat without contact with the painted sheet, there is also a contact sheet which heats the painted sheet by conduction heat. Sometimes a hot plate is used. Then, after or simultaneously with the heating and softening of the painting sheet, air is sucked in from a ventilation hole (not shown) provided in the mold B, and the painting sheet is vacuum-formed to form the cavity forming surface 27 of the mold B (see FIG. 9). )
Preform the painted sheet.

Then, both molds A and B are clamped. If the prepainted sheet is being formed, the hot platen 24 is moved and retracted from between the two dies to a retracted position outside the dies before the preforming. In the case where the preforming is performed, the molds A and B are clamped in a state where the painted sheet is kept in close contact with the cavity surface of the mold B during the vacuum forming even after the preforming. FIG. 10 shows a state after the pre-forming of the painted sheet and the clamping of the mold. As shown in FIG. 10, on the parting surface of the mold A, a receiving groove 28 serving as a concave portion capable of accommodating the clamp is provided on a parting surface portion of the mold A facing the clamp so that the clamp 23 does not hinder the mold clamping. It is.

Then, a resin formed by heating and melting is injected and filled into a cavity formed by the two dies which are clamped. The resin is usually injected from the injection nozzle through the runner (runner) and the gate (gate) to the side of the fixed mold A. Then, after the resin is cooled and solidified, the mold is opened, and the molded product is ejected from the mold A by ejecting the molded product with an ejector pin or the like. In the case of transfer, a final molded product is obtained by peeling and removing only the support sheet of the painted sheet including the support sheet and the transfer layer from the molded product.

By the way, conventionally, when a molded article having an undercut is generally obtained by injection molding, an undercut processing mechanism such as using a slide core and sliding the slide core laterally with an angular pin is provided in a mold. When the molded product is ejected from the mold in the mold open state and the mold is released, the undercut portion does not hinder the release. Similarly, in the simultaneous injection molding painting method, the mold is provided with an undercut processing mechanism depending on the shape of the molded product. For example, FIG. 5 shows a painted molded product used for an automobile console box. The molded article M is provided with a mounting rib 1 protruding therefrom. A- of FIG.
FIG. 6 is a sectional view of a main part of the mounting rib 1 at the A line.
Shown in The mounting rib 1 may be treated as an undercut portion in the simultaneous injection molding painting method.
The reason is that, in a molded product having an excessively deep drawing of the painted sheet, the stretch of the painted sheet is large and the distortion of the picture becomes large, so that the mold structure is such that the drawing is reduced as much as possible.

[0008] In the case of ordinary injection molding without using a painted sheet, a dividing surface (parting surface) for dividing a molding die into a movable die and a fixed die is a parting line PL as shown in FIG.
Set to position 2. In the division at the parting line PL2, the mounting rib 1 as shown in FIG. 5 does not become an undercut. Therefore, the mold does not require an undercut processing mechanism. On the other hand, in the simultaneous injection molding and painting method in which the painted sheet is fixed on the parting surface, the sheet is deeply drawn down at the parting line PL2 when the painted sheet is formed (Δx1 in FIG. 6). However, in the case of a molded product used for a console box or the like as shown in FIG. 5, the painting surface requiring painting is a position slightly lower from the upper side as shown in FIG. It is not necessary to go to the lower part where the protrudes. Therefore, the parting surface of the mold is the parting line PL1. By doing so, the aperture can be as small as Δx2. As a result, the mounting rib 1 becomes the undercut 2 portion. As described above, in a molding die used for simultaneous painting by injection molding, it is necessary to consider drawing of a painted sheet, so that an undercut processing mechanism tends to be added more often than a normal molding die.

[0009]

There have been various types of undercut processing mechanisms for injection molding dies, and a slide core is one of the conventional mechanisms. However, in the simultaneous injection molding painting apparatus, a sheet supply mechanism for supplying the painting sheet between the molds, a clamp mechanism for further fixing the painting sheet to the mold, and a heating plate for heating and softening the painting sheet as appropriate. It is necessary to provide a device such as a heating mechanism around the mold.
Therefore, undercut processing mechanisms that can be used so as not to interfere with these mechanisms have been limited.

For example, as shown in FIG. 2, an inclined groove is provided in the fixed mold B, a split mold 5 is provided in the inclined groove, and before the molded product is ejected from the fixed mold A with an ejector pin or the like, the molded article is removed. This is a mechanism in which the split mold 5 forming the undercut portion is guided and moved by an inclined groove by a hydraulic cylinder or the like provided in the fixed mold A. However, this mechanism cannot secure a large slide amount in the split mold 5 and is not suitable for an undercut having a length (50 mm) as shown in FIG. Next, in the mechanism shown in FIG. 3, the slide core 3 provided on the fixed die A side is rotated by an angular pin (inclined pin) 6 raised from the movable die B side according to the opening and closing of the die. (In the drawing direction) (in the drawing direction). In this mechanism, since the angular pin 6 comes out obliquely to the side of the mold, it may interfere with the feeding device for the painted sheet or the heating plate of the sheet heating device. Further, depending on the arrangement position of the angular pins and the size of the mold, the direction in which the molded product is taken out is restricted. Next, the mechanism shown in FIG.
Is operated laterally by the slide hydraulic cylinder 4 instead of by the angular pin.
Since the hydraulic cylinder cannot withstand the injection pressure in the hydraulic cylinder, it is necessary to fix the slide core 3 by inserting the fixing pins 8 into the slide core 3 with the hydraulic cylinder 7 for fixing, which makes the mechanism complicated. was there.

[0011]

Therefore, in order to solve the above-mentioned problems, in the injection molding die of the present invention, a sheet with a picture is supplied on a movable die of a pair of injection molding dies consisting of a fixed die and a movable die. After that, a first step of fixing the painted sheet with a frame on all sides of the cavity of the mold, a second step of clamping both molds and injecting a resin, and after the resin is solidified, a part of the fixed mold Is moved in the transverse direction to the moving direction of the movable mold, and then, a third step of releasing the product from the fixed mold, and a mold used in the injection molding simultaneous painting method performed in this order,
Part of the fixed die that slides in the horizontal direction is configured so that the horizontal position is fixed by a frame that fixes the painted sheet in all directions during mold clamping. Further, in the above-mentioned injection molding die, between the first step and the second step, a heat source for heating the painted sheet enters between the two molds in the mold opened state, and after the painted sheet is heated and softened. It is also used in a simultaneous injection molding painting method in which a vacuum is drawn from the movable mold and a vacuum forming process is performed to bring the picture sheet along the cavity forming surface of the movable mold.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an injection mold according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram illustrating an undercut processing mechanism in the case of the injection molding die of the present invention. As shown in FIG.
Is reciprocated in the lateral direction by lateral driving means such as a hydraulic cylinder 4 for sliding. Here, the “lateral direction” refers to a direction forming a predetermined angle (for example, 90 °) with respect to the opening / closing (moving) direction of the movable mold. In FIG. 1, the direction is the vertical direction (of course, depending on the shape of the molded product, the direction may be the front and back of the paper of FIG. 1). For fixing the slide core 3 so as to withstand the injection pressure, a clamp 23 for fixing a sheet with a picture is used instead of the fixing pin 8 driven by a hydraulic cylinder as shown in FIG. The slide core 3 and the slide hydraulic cylinder 4 are provided for the fixed die A.
The clamp 23 is provided on the movable mold B side.

The clamp 23 is a sheet fixing means for fixing the picture sheet to the movable mold B, and is a frame for fixing the picture sheet around the cavity of the mold. Clamp 2
The shape of No. 3 is, for example, a shape as shown in FIG. The clamp 23 is installed on the movable die B, and is driven by a sliding rod 29 in a direction perpendicular to the parting surface as shown in FIG. 11 to fix or release the painting sheet. As shown in FIG. 10, the clamp 23 keeps the sheet S with the picture fixed even when the mold is clamped, and does not retreat outside of both molds even when the mold is clamped. Therefore, in the mold having no undercut processing mechanism according to the present invention, as shown in FIG. 10, a receiving groove 28 which is a concave portion capable of accommodating the clamp 23 is provided on the parting surface of the fixed mold A as shown in FIG. The clamp 23 was provided on the parting surface so that the clamp 23 did not hinder mold clamping. In the injection molding die of the present invention, at least a part where the undercut processing mechanism is provided on the parting surface of the fixed die is not formed by the receiving groove 28 but in the moving space of the slide core 3 as shown in FIG.
The clamp 23 is received and stored. Moreover, at the time of storage, that is, at the time of mold clamping, the clamp 23 is in contact with the back surface of the slide core 3 and fixes the slide core 3 so as to prevent the slide core 3 from retreating.

Since the clamp 23 is a frame, the slide core 3 pushes the clamp 23 downward in the drawing by the injection pressure, but the clamp 23 receives the injection pressure by the other side of the clamp 23 (not shown). If the slide core 3 is also on the other side of the clamp 23, these are canceled because the slide cores on both sides press the clamp 23 in the opposite direction. When only one of the molded products has an undercut as shown in FIG. 5, the undercut processing mechanism is only one for the clamp (see FIG. 11). Since the clamp 23 is housed by the receiving groove 28 on the side where there is no, the clamp 23 is fixed by the receiving groove 28, and the slide core 3 is finally fixed. Even in such a case, in the case of a formed product as shown in FIG. 5, the mounting ribs 1 serving as undercuts are separated into two portions on one side, so that only the respective small portions are separated and independent slides. A core can be provided and each can be driven by a separate and independent hydraulic cylinder. With such a structure, the parting surface of the fixed mold A between the two slide cores is provided with the receiving groove 28 and receives the clamp 23 as in the normal case. Therefore, each slide core can be fixed by fixing the movement of the clamp 23 by the receiving groove 28 on the same side.

As described above, in the injection molding die of the present invention,
The frame (clamp) used as the sheet fixing means in the injection molding simultaneous painting apparatus is also used as the fixing means for the slide core, so that the hydraulic cylinder for fixing, which has been conventionally used, is unnecessary, and the structure is correspondingly reduced. And the control can be simplified. Although the lateral driving means is a hydraulic cylinder in FIG. 1, the slide core 3 is fixed by the clamp 23, and may be a pneumatic cylinder or the like. Also, in FIG. 1, the clamp 23 does not receive and fix the slide core 3 with the entire thickness of the rear surface thereof, but this is also for the sake of easy understanding in the drawing in relation to the hydraulic cylinder 4 for slide. If a recess is provided to allow the piston of the hydraulic cylinder to move the slide core in the horizontal direction (the horizontal direction in the direction of opening and closing of the mold), it is possible to contact the slide core with the entire thickness of the back surface of the slide core. Can be fixed.

The term "painting" as used in the present invention means, in addition to simply giving a visible pattern such as a picture, a character or a figure to a molded product, a pattern which is not visible, or a hard coating, a conductive film or the like. And the like. Known patterns such as an ink layer formed by printing or the like and a metal thin film formed by vacuum evaporation or the like are examples of a visible pattern. Examples of an invisible pattern are transparent to visible light and fluorescent by ultraviolet irradiation. Is used.

[0017]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example) As a mold for injection molding of the present invention,
A molded product M for a console box of an automobile as shown in FIG. 5 was manufactured by simultaneous injection molding and painting using a mold having an undercut treatment mechanism as shown in FIG. The painted sheet used was a 125 μm-thick acrylic resin film having a wood grain pattern printed on the inner side (molded product side) with an ink obtained by adding a pigment to an acrylic resin binder, followed by vinyl chloride-acetic acid. It is a continuous belt-shaped sheet coated with a 2 μm thick adhesive of a vinyl copolymer.

The part to be the undercut 2 is composed of two mounting ribs 1 provided separately on one side of the molded product.
The slide core 3, which is a part of the fixed mold A, has a mold structure provided independently only for each undercut portion. The slide cores 3 are independently operated by a slide hydraulic cylinder 4 provided independently, but are reciprocated in the horizontal direction in conjunction with each other. In order to fix the two slide cores 3, one clamp 23, which is a frame for fixing the picture sheet installed on the movable mold B to the parting surface of the movable mold B, was used. The clamp 23 has a shape as shown in FIG. The other three side surfaces of the molded product M on which the mounting ribs are not provided have no slide core. On the parting surfaces of the movable die A corresponding to these three side surfaces and the parting surface which is not a slide core portion on one side where the light core 3 is provided, as shown in FIG. A receiving groove 28 is provided. The receiving groove 28 on the slide core side has a structure in which the clamp 23 is received on the side surface so that the clamp 23 can receive the slide core even if the slide core is pressed by the injection pressure. The hydraulic cylinders used in the above mold structure are two for the clamp (movable mold side), one for the ejector for ejecting the molded product (fixed mold side), and two for the slide core (fixed mold side). Individual.

Then, using the above-prepared painted sheet, injection molding was carried out according to the procedure illustrated in FIGS.
First, the sheet S with the picture is transferred onto the parting surface of the movable mold B of the pair of the fixed mold A and the movable mold B by the transport chuck 2.
1 and the fixed chuck 22. Thereafter, the sheet with the picture is clamped on the four sides around the cavity of the movable mold B.
3 (FIG. 8). Next, a hot platen 24 for heating the painted sheet is inserted between the two molds in the mold open state from the retracted position outside the mold, and the painted sheet is heated by radiant heat by non-contact heating at a predetermined distance from the painted sheet. Softened (FIG. 9). Next, vacuum drawing was performed from the movable mold, and the painted sheet was preformed by vacuum forming along the cavity forming surface 27 of the movable mold (FIG. 10). Thereafter, both molds were clamped. By the mold clamping, the slide core was fixed by the clamp (FIG. 1, left side). Then, the heat-resistant ABS resin was injected, and after the resin was cooled and solidified, the mold was opened.
Clamp 2 which fixed slide core by mold opening
After releasing the fixation, the slide core 3 was moved by the slide hydraulic cylinder 4 to open the undercut 2 portion. Then, the molded product was ejected from the fixed mold by ejecting with an ejector pin. The resulting molded article was decorated with a sheet with a picture layer laminated on the surface, and the slide core did not move due to the resin pressure, and no burrs were observed on the slide core.

(Comparative Example 1) Instead of the mold used in Example 1, the structure as illustrated in FIG. 4 is used, and the fixing pin 8 and the fixing hydraulic cylinder 7 of the slide core 3 are not provided.
As the slide core, a mold having a structure simply operated by the slide hydraulic cylinder 4 was used. A receiving groove 28 provided in the fixed mold A so that the clamp does not disturb the mold clamping is also provided in the slide core so as not to contact the clamp. Accordingly, the slide core has a structure that is not fixed by the clamp. The number of hydraulic cylinders is the same as in the above embodiment. Then, injection molding was performed in the same manner as in Example 1. However, in the obtained molded product, burrs were generated at the slide core portion because the slide core moved by losing the resin pressure.

(Comparative Example 2) A mold having a structure further provided with a fixing pin 8 and a fixing hydraulic cylinder 7 of the slide core 3 was used in comparison with the mold used in Comparative Example 1. The number of hydraulic cylinders is further increased to two for fixing hydraulic cylinders (fixed type side), and is seven in total. When injection molding was performed in the same manner as in Example 1, no burrs were formed on the slide core of the obtained molded product. However, since the number of hydraulic cylinders was increased as compared with the embodiment, the mold structure became complicated. Further, since the slide hydraulic cylinder and the fixing hydraulic cylinder are operated at different timings, the control is complicated.

[0023]

According to the present invention, in the injection molding die used in the simultaneous injection molding painting method, the slide core for undercut processing is fixed using the clamp (frame) for fixing the sheet with the image. Therefore, even a molded product having an undercut can have a simple mold structure. In addition, operation control related to the thyroid core can be easily performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an undercut processing mechanism in an injection mold according to the present invention.

FIG. 2 is a conceptual diagram illustrating a general undercut processing mechanism (inclined groove).

FIG. 3 is a conceptual diagram illustrating a general undercut processing mechanism (angular pin).

FIG. 4 is a conceptual diagram illustrating a general undercut processing mechanism (hydraulic slide).

FIG. 5 is a plan view showing an example of a molded product by a simultaneous painting method of injection molding.

FIG. 6 is an explanatory diagram of an undercut portion in a cross-sectional view taken along line AA of FIG. 5;

FIG. 7 is a conceptual explanatory view of a procedure according to an example of a simultaneous painting method for injection molding (part 1: before supplying a painting sheet).

FIG. 8 is a conceptual explanatory view of the procedure (part 2: after supplying a sheet with a picture).

FIG. 9 is a conceptual explanatory view of the procedure (part 3: painting sheet heating).

FIG. 10 is also a conceptual explanatory view of the procedure (part 4: vacuum forming of a sheet with a picture, after clamping).

FIGS. 11A and 11B are a front view and a side view for explaining a shape of a clamp which is a frame for fixing a painted sheet.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mounting rib 2 undercut 3 slide core 4 slide hydraulic cylinder 50 split mold 6 angular pin 7 fixing hydraulic cylinder 8 fixing pin 21 transfer chuck 22 fixed chuck 23 clamp (frame) 24 heating plate 25 cutter 26 receiving groove 27 cavity forming surface 28 receiving groove 29 sliding rod A type (fixed type, male type) B type (movable type, female type) M molded product PL1 parting line (in the case of the present invention) PL2 parting line (general injection) In case of molding) R roll S Painting sheet

Claims (2)

[Claims] 1. A first step of supplying a painted sheet onto a movable mold of a pair of injection molding dies, which comprises a fixed mold and a movable mold, and then fixing the painted sheet with a frame around four sides of a cavity of the mold. And a second step of injecting the resin by clamping the two dies, and after the resin is solidified, moving a part of the fixed die in a direction transverse to the moving direction of the movable die, and then removing the product from the fixed die. A third step of molding and a mold used in the simultaneous injection molding and painting method, in which order, a part of the fixed mold that slides in the lateral direction is a frame for fixing the painted sheet in all directions at the time of mold clamping. Injection molding die whose lateral position is fixed by the body. 2. Between the first step and the second step, a heat source for heating the painted sheet enters between the two molds in the mold open state, heats and softens the painted sheet, and then moves the sheet from the movable mold. 2. The injection molding die according to claim 1, wherein the injection molding die is used in a simultaneous injection molding and painting method in which a vacuum forming step is performed in which a vacuum drawing step is performed so that the painting sheet is made to conform to the cavity forming surface of the movable mold.