JP3255020B2 - Skin integral molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for integrally forming a skin by molding a resin for a core layer and simultaneously fusing and integrating a decorative skin material on the surface of the resin for the core layer.

[0002]

2. Description of the Related Art In recent years, resin molded parts used for automobiles, home appliances, building materials, and the like have increased added value such as cushioning property, decorativeness, touch feeling, and the like, or have reduced cost by reducing the number of molding steps. Therefore, two-layer molding has been performed in which a decorative skin material is integrally molded on the surface of the core layer resin as described below. That is, when using an injection molding machine, a skin material is set between the opened molds, the mold is closed and the mold is closed, and then a mold cavity formed by the skin material and the mold is formed. The inside is injected and filled with a molten resin as a core material.
Then, the holding pressure is supplied by using the injection unit, the cooling is performed for a specified time, the mold is opened, and the product is taken out. From the mold clamping to the product removal in this method, the molding operation is performed by a normal injection molding method, and the mold is clamped with high pressure so that the resin does not leak during injection filling. A method using a press molding machine A skin material is set between both molds that have been opened, and while holding both molds at a predetermined mold opening amount, a space is formed between the skin material and the mold. Then, after injecting and filling the molten resin to be the core material, both molds are subjected to mold clamping press, and then cooled for a specified time,
Open the mold and take out the product.

[0003]

However, such a conventional method has the following problems. (1) In the above-mentioned method, when the core material is injected, usually 300
Since the resin flow of a high resin pressure exceeding kgf / cm ² is applied to the skin material, the skin material is severely damaged, which leads to quality deterioration and poor appearance. For example, in the case of foamable skin material, the cushioning property disappears due to the collapse of the foam layer,
In the case of the raised skin material, the feeling of touch is deteriorated and the sense of quality is lost due to the fall of the hair. (2) In the above method, the core material is injected in a state in which the mold is widely opened. For example, a mold structure in which resin does not leak, such as a shear edge structure of the parting surface, is required. The cost of the mold is increased, the maintenance of the mold is required to prevent the wear of the shear edge portion, and the productivity is reduced. (3) In addition, since it is necessary to set the skin material in the mold open state, it is necessary to hold the skin material during injection of the core material or during the mold clamping press. Must be installed, which complicates operation and increases costs.

[0004]

In order to solve the above-mentioned problems, in the present invention, a mold is closed by interposing a skin material between a pair of left and right or upper and lower pairs of opposing molds, and then closing the mold. Injection-filling a molten resin as a core material into a mold cavity formed by the skin material and the two molds, and a skin integral molding method of integrally molding the skin material and the core material,
The amount of cooling solidification shrinkage of the molten resin is calculated in advance, the amount of the molten resin obtained by adding the amount of cooling solidification shrinkage is injected and filled, and the pressure range of the resin pressure in the mold cavity is set to 5 to 7
0 kgf / cm ² .

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a mold is closed between a pair of opposed left and right or upper and lower molds by closing a mold with a skin material interposed therebetween. Injecting and filling a molten resin as a core material into a mold cavity, in a skin integral molding method of integrally molding the skin material and the core material, a cooling solidification shrinkage amount of the molten resin is calculated in advance,
The amount of the molten resin obtained by adding the amount of the cooling solidification shrinkage is injected and filled, and the mold clamping pressure of the mold is controlled so that the resin pressure in the mold cavity falls within a set pressure range. As a result, the following preferable molding is performed. By injecting and filling the amount of resin to which the amount of cooling solidification shrinkage has been added and performing mold clamping pressure control, a uniform overall pressure holding action from the mold clamping side according to the cooling and solidification behavior of the resin is performed, causing deformation and warping. Without this, uniform adhesion of the skin material to the core material can be achieved. The resin pressure in the mold cavity is, for example, 5 to 70 kg.
The pressure is controlled to be as low as f / cm ² , and high-pressure molten resin flow during injection of the core material is prevented, and damage to the skin material is suppressed. The lowering of the resin pressure in the mold cavity achieved by controlling the mold clamping pressure causes the mold opening operation of the mold at the time of core material injection. As a result, the degassing effect is increased, the reduction of the resin pressure in the mold cavity is promoted, and the flow of the core material resin is performed smoothly, so that the mold cavity is completely filled. In this case, the opening amount of the mold is as small as about 1 mm, which prevents resin leakage in combination with the sealing effect on the parting surface of the skin material, and does not require a special mold such as a shear edge structure. By holding the periphery of the skin material in the low-pressure mold clamping state, it holds the skin material while applying a moderate tension, preventing local expansion of the skin material and maintaining uniform skin material performance I do.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 relate to an embodiment of the present invention,
FIG. 1 is an overall configuration diagram of an injection molding machine used in the present invention, and FIG.
Is a graph showing the correlation between the resin pressure in the mold cavity and the degree of damage to the skin material, and FIG. 3 is a flowchart of the skin integral molding process.

As shown in FIG. 1, an injection molding machine 100 according to the present invention comprises a mold device 10, a mold clamping device 20, an injection device 30, and a control device 60. The mold apparatus 10
It comprises a fixed mold 3 attached to the fixed platen 1 and a movable mold 4 attached to the movable platen 2. The movable platen 2 and the movable mold 4 can be moved forward and backward by the mold clamping cylinder 22 of the mold clamping device 20. Be composed. The mold clamping device 20 includes a mold clamping cylinder 22 that operates to open and close the molds 2 and 4 of the mold device 10. The movable mold 4 is connected to the fixed mold 2 by a tie bar (not shown). You will be guided back and forth.

The injection device 30 includes a screw 32 having a screw blade 36 spirally mounted on the outer periphery of a barrel 32. The screw 34 is rotatable by a forward / reverse hydraulic motor 42 and an injection cylinder 40, and can be freely moved back and forth. The molten resin is injected into the mold cavity 5 formed between the molds 2 and 4 via the nozzle 39 while heating and melting and kneading the resin pellets supplied to the hopper 38. That is, the injection device 30 heats and compresses the resin material in the hopper 38 in the supply zone and the compression zone in the barrel 32, melts and measures in the measurement zone, and passes through the injection zone into the mold cavity 5 via the nozzle 39. It is configured to fire. Hydraulic oil supplied from a hydraulic supply source 50 is supplied to the injection cylinder 40 and the forward / reverse rotation hydraulic motor 42 at a constant pressure set by a hydraulic control valve 52 and driven.

On the other hand, as shown in FIG. 1, the control device 60 includes a mold clamping control unit 64 and a mold clamping control unit 6 for inputting pressure information measured by the resin pressure sensor 62 arranged on the fixed mold 3.
4 and a hydraulic control valve 66 for the mold clamping cylinder 22 that operates in response to the output signal. In this embodiment, an injection molding machine having a direct pressure type mold clamping device is used, but an injection molding machine of a toggle mold clamping device or a vertical injection molding machine may be used.

In the present invention, in the injection molding machine 100 configured as described above, both molds of the mold apparatus 10 are opened,
The skin material S is set at a predetermined position on the mold parting surface facing the mold cavity 5, the periphery is gripped, and the mold is closed.
After the low pressure mold clamping state, the core material Q is injected and filled into the mold cavity 5. When setting the skin material, it is desirable to maintain a slight tension state (tensile state) so that the skin material S does not loosen. Then, the resin pressure in the mold cavity 5 during the injection filling is detected by the resin pressure sensor 62, and the mold clamping control unit 64 controls the mold so as to maintain the pressure at a preset pressure in a pressure range of, for example, 5 to 70 kgf / cm ^2. An operation command is issued to the clamping cylinder 22 to perform mold clamping pressure control.

FIG. 2 is a graph showing the correlation between the resin pressure in the mold cavity and the degree of damage to the skin material. According to this graph, when the resin pressure exceeds 70 kgf / cm ² , the skin material rapidly increases. It was found that the damage degree of S became large and the product quality deteriorated. Therefore, the maximum of the resin pressure range in the low pressure mold clamping pressure control is set to 70 kgf / cm ² .
The reason why the minimum resin pressure range is set to 5 kgf / cm is that if it is less than 5 kgf / cm, the amount of mold opening during injection filling of the core material Q becomes too large and resin leakage occurs. Poor performance causes molding failure. Therefore,
The range of the region C in FIG. 2 is selected as the setting range of the resin pressure.

That is, the cause of damage to the skin material Q is a synergistic effect of “temperature”, “pressure”, and “time”, all of which are caused by the core material S. Here, “temperature” is the core material resin temperature, and the lower the temperature, the less the skin material S is damaged,
On the other hand, poor plasticization and poor flow of the core material resin are apt to occur, resulting in poor molding. Therefore, it is important to select a temperature condition that matches the resin characteristics. For example, in the case of a PP resin (polypropylene resin), the temperature is preferably around 200 to 230 ° C. "Time" is the contact time between the core material resin and the skin material in a high temperature state. The smaller the time, the less the damage to the skin material S, but the core determined by the shape, size, and mold cooling capacity of the molded product. It is limited by the cooling and solidification time of the material resin. Therefore, for example, an average cycle of about 20 to 60 seconds is appropriate. “Pressure” refers to the resin pressure in the mold cavity, and is preferably as small as possible. In the conventional two-layer molding method using an injection molding machine, the resin pressure was in the region A. Therefore, the degree of damage to the skin material S was large, and molding defects with extremely poor surface conditions could not be avoided. By setting this to a resin pressure of 70 kgf / cm ² or less as in the present invention, damage to the skin material S is almost eliminated, and
/ Cm ² or more, there is no mold opening range without resin leakage, and the shaping ability of the core material Q is maintained.

Further, in the present invention, as a result of the mold opening behavior corresponding to the injection filling being performed, good degassing is achieved, which promotes the operation of filling and flowing the core resin into the mold cavity, and furthermore, the skin material Synergistic with the heat insulating effect of the resin, the resin pressure is reduced, complete filling and short time filling are achieved. The resin pressure in the mold cavity is 5 to 70 kgf /
In the mold clamping pressure control of the present invention performed in a pressure range of cm ² ,
Since the mold opening amount is as small as about 1 mm, the skin material S by gripping the peripheral portion of the skin material S on the mold parting surface.
In addition to the sealing effect on the parting surface, resin leakage is small, and a mold having a shear edge structure is not required.

Further, since the peripheral part of the skin material is clamped and held at a low pressure on the parting surface of the mold, the tension control of the skin material S corresponding to the injection filling of the core material resin (the skin material S becomes Sliding along the mold parting surface). On the other hand, in the conventional two-layer molding method using an injection molding machine, tension control cannot be performed because the skin material is completely fixed on the parting surface, and as a result, the skin material is locally stretched, and tearing or surface breakage occurs. Non-uniform properties occur. In addition, in the two-layer molding method using a conventional press molding machine, means for fixing the skin material is separately required, which is complicated.

Further, according to the present invention, the amount of cooling solidification shrinkage of the molten resin is calculated, and the amount of the molten resin obtained by adding the amount of cooling solidification shrinkage is injected and filled. The mold clamping control unit 64 controls the mold clamping cylinder 22 to detect the resin pressure in the cavity and maintain the resin pressure in the mold cavity at a low pressure of about 5 to 70 kgf / cm ^2.
To issue an operation command to continue the mold clamping pressure control. As a result, as a synergistic effect with the heat insulating effect of the skin material S, a uniform pressure-holding action from the mold clamping side corresponding to the cooling, solidification and shrinkage behavior of the resin is performed while suppressing damage to the skin material S, and the core material At the same time as the shaping of Q, the adhesion between the core material and the skin material without deformation or warpage is realized.

When the cooling and solidification of the core material Q is completed, the mold is opened, and if necessary, the peripheral portion of the skin material S is trimmed and the gate and runner portions are cut, and then the product is taken out. Obtain a skin-integrated molded product without damage.

In the above-described series of molding operations, as described above, the mold clamping control section 64 performs feedback control of the mold clamping pressure based on the detection signal of the resin pressure sensor 62.
Note that a method in which feedback control of the mold clamping pressure is not performed is also possible. In this case, for example, simply maintaining the mold-clamping pressure at a low pressure of about 5 to 70 kgf / cm ² may slightly degrade the control accuracy. However, the mold-clamping pressure and the resin pressure are balanced by the mold opening behavior. The resin pressure in the mold cavity can be maintained at 5 to 70 kgf / cm ² .

There is no particular limitation on the skin material s, and the skin material s is properly used depending on the required performance. One example is shown below. In order to obtain a texture and softness, a resin sheet such as a PP resin or a PE resin, a two-layer sheet in which a foam layer such as a foamed PP is attached to the back of a leather or a cloth are used. . In addition, in order to give a feeling of touch and luxury, use a two-layer sheet having a raised layer such as synthetic fiber or cloth on the surface of a resin sheet such as PP or PE, and foam on the back of the resin sheet if necessary. A layer may be provided.

As for the core material Q, a thermoplastic resin such as PP or PE is used, and talc, fiber or the like is added as needed.

[0020]

As described above, according to the method of the present invention, the following excellent effects are achieved. (1) Damage to the skin material (foamable skin material loses soft feeling due to collapse of foam layer, brushed skin material loses feel and luxury due to hair fall, surface of skin material due to local stretching An integrated skin-molded article having very excellent appearance performance without uneven properties, breakage, wrinkles, etc.) can be stably obtained. (2) It is not necessary to use a mold having a shear-edge structure or the like and ancillary equipment for holding the skin material, thereby realizing low cost and improved productivity.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a graph showing a correlation between a resin pressure in a mold cavity and a degree of damage to a skin material according to an example of the present invention.

FIG. 3 is a flowchart of a skin integral molding process according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 fixed platen 2 movable platen 3 fixed mold 4 movable mold 5 mold cavity 10 mold device 20 mold clamping device 22 mold clamping cylinder 30 injection device 32 barrel 34 screw 36 screw blade 38 hopper 39 nozzle 40 injection cylinder 42 hydraulic motor Reference Signs List 50 hydraulic supply source 52 hydraulic control valve 60 control device 62 resin pressure sensor 64 mold clamping controller 66 hydraulic valve 70 hydraulic supply source 100 injection molding machine Q core material S skin material

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/00-45/77

Claims (1)

(57) [Claims] 1. A mold is closed by interposing a skin material between a pair of left and right or upper and lower molds facing each other, and then as a core material in a mold cavity formed by the skin material and the two molds. In a skin integral molding method of integrally molding the skin material and the core material by injection-filling the molten resin, a cooling solidification shrinkage amount of the molten resin is calculated in advance, and the molten resin amount obtained by adding the cooling solidification shrinkage amount is calculated. Injection filling is performed, and the pressure range of the resin pressure in the mold cavity is set to 5 to 7
A method for integrally forming a skin, wherein a mold clamping pressure of a mold is controlled so as to be 0 kgf / cm ² .