JPH1024445A - Skin integrating molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a short time and perfect filling by enhancing the fluidity of a core material resin by a method wherein mold clamping pressure is controlled so as to hold the resin pressure in a mold cavity in multiple stages in response to molding processes within the set pressure range. SOLUTION: In an injection molder 100, first of all, both the molds 3 and 4 of a mold assembly 10 are opened. Then, a skin material S is set at the predetermined position opposing to the mold cavity 5 of a mold parting surface and its peripheral edge part is grasped. After that, the molds are closed so as to realize a low pressure mold clamping state. Under the state just mentioned above and the previously given condition that injection time is confined in 5sec or less, core material Q is injected and filled in the mold cavity 5. By detecting the resin pressure in the mold cavity 5 during the injection and filling, a mold clamping controlling part issues an operation command to a mold clamping cylinder 22 so as to keep the resin pressure at the pre-set pressure within the pressure range of 70-150kgf/cm<2> , for example, for controlling a mold clamping pressure in order to obtain a molded article integral with the skin, in which the skin material S and the core material Q uniformly come into close contact with each other.

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, so that when the injection is shifted to the mold clamping press, a rapid change in the resin flow occurs, and as a result, the flow mark Defects occur, and these defects cause the surface properties of the skin material to become non-uniform, resulting in poor appearance.
Furthermore, for example, a mold structure that does not leak resin is required, such as a shearing edge structure for the parting surface.
The cost of the mold is increased, mold maintenance is required to prevent wear of the shear edge portion, and 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. (4) In recent years, particularly in the field of injection molded products, there has been a strong demand for weight reduction and cost reduction. In order to realize this, there is a trend in the industry to respond to the demand for thinner products. The tendency is seen. Therefore, in the above method, the resin flow path of the core material in the mold cavity is narrowed, so that an increase in resin pressure is inevitable. In addition, in the above-mentioned method, the cost increase due to the high functionality of the auxiliary equipment of the mold is unavoidable, the cooling and solidification of the core material resin is fast, and the molding requires a high-speed, high-pressure clamping pressure load. .

[0004]

In order to solve the above problems, in the present invention, in the first invention, a skin material is interposed between a pair of opposed left and right or upper and lower molds. After the mold is closed, a molten resin serving as a core material is injected and filled into a mold cavity formed by the skin material and the two dies, and the skin material and the core material are integrally molded to form a skin integral molding. In the method, after applying to the mold a mold clamping pressure that allows the mold to open with the pre-filled resin pressure, and injecting and filling the molten resin amount obtained by adding the cooling solidification shrinkage amount of the molten resin, The mold clamping pressure is controlled so as to maintain the resin pressure in the mold cavity in multiple stages within a set pressure range according to the molding process. Also, the second
In the invention of the first aspect, during the injection filling in the first aspect, the resin pressure in the mold cavity is set to 70 to 150 kgf / cm ² ,
Thereafter, the pressure was reduced to ² to 50 kgf / cm ² . Further, in the third invention, in the first and second inventions, the pressure switching of the resin pressure in the mold cavity is performed when injection filling is completed or when a set time is reached within 5 seconds from the start of injection filling. In the fourth invention, the injection filling time in each of the above inventions is set to 5 seconds or less. And
In the fifth invention, the temperature of the mold during molding was kept as low as possible without causing condensation. In addition, the sixth
According to the invention, during the injection filling, the moving amount of the mold is controlled so that the mold opening amount is set in advance.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, after a skin material is interposed between a pair of left and right or upper and lower molds facing each other and the mold is clamped, a mold formed by the skin material and the two molds is used. In a skin integral molding method in which a molten resin serving as a core material is injected and filled into a mold cavity, and the skin material and the core material are integrally molded, a mold that allows a mold to be opened by a pre-filled resin pressure. After the clamping pressure is applied to the mold, the amount of the molten resin obtained by adding the amount of cooling, solidification, and shrinkage of the molten resin is injected and filled, and the resin pressure in the mold cavity is molded within a set pressure range. The mold clamping pressure was controlled so as to be held in multiple stages according to the process. As a result, the following preferable molding is performed. During injection filling, the mold opening behavior is exhibited by controlling the mold clamping pressure to a moderate pressure of, for example, 70 to 150 kgf / cm ² in the mold cavity. As a result, the mold cavity volume (resin flow The flow of the core material resin is increased by the expansion of the path) and the degassing effect, so that the filling is completed in a short time and complete filling is achieved, and at the same time, the pressure is reduced. In particular, a remarkable effect is exhibited at the time of thinning molding. In this case, the opening amount of the mold is as small as about 1 mm or less, 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. Can operate enough. After injecting and filling the resin amount obtained by adding the cooling solidification shrinkage amount, for example, the resin pressure in the mold cavity is increased to 2 to 50 kgf.
By controlling the mold clamping pressure to a pressure as low as / cm ^2, a uniform pressure-holding action from the mold clamping side according to the cooling and solidifying behavior of the resin is performed, without causing deformation or warpage.
In addition, uniformity of the adhesion of the skin material to the core material can be achieved without damaging the skin material. At the time when the injection filling is completed, the core material resin is almost fully filled (also referred to as a just pack), so that no defect such as a flow mark occurs at all. During injection filling, the effect of short-time filling by the mold opening behavior and the control of resin pressure in the mold cavity reduce the pressure applied to the skin material during core material injection, shorten the loading time, As much as possible. By controlling the mold clamping pressure (mold opening, holding pressure) with the peripheral part of the skin sandwiched between the mold parting surfaces, the skin is appropriately tension controlled and held, and the skin is moderately tensioned (tensile). , While preventing the local extension of the skin material, thereby obtaining a molded product with high decorative performance uniformly extended over the entire core material.

[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.
FIG. 3 is a flowchart of the skin integral molding step, and FIG. 3 is a graph showing the correlation between the resin pressure in the mold cavity, the holding time, and the degree of damage to the skin material in the skin integral molding step.

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. In addition, the fixed mold 3 and the movable mold 4
Is maintained at a predetermined temperature by the temperature controller 8. Mold clamping device 20
Is provided with a mold clamping cylinder 22 that operates to open and close the molds 2 and 4 of the mold apparatus 10. The movable mold 4 is guided by a tie bar (not shown) with respect to the fixed mold 2. Go 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 raw 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 through 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 that has received an operation command from an injection control unit 61, and is driven. You.

On the other hand, as shown in FIG. 1, a control device 60 is provided with a position sensor for measuring pressure information measured by a resin pressure sensor 64 disposed on the fixed mold 3 and a gap between the molds 3 and 4. 65, a hydraulic control valve 69 for the clamping cylinder 22 which operates in response to an output signal from the clamping control unit 63, and a timer 6 for the clamping control unit 63.
2 and an injection control unit 61. 70 is a hydraulic supply source. In the present 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 or an electrically driven mold clamping mechanism is provided. Or an injection molding machine.

In the present invention, the operation of the injection molding machine 100 configured as described above is performed according to the process shown in FIG. First, the molds 3 and 4 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, and the periphery is gripped to close the mold. After the mold is brought into the low-pressure mold-clamped state, a condition that the injection time is set within 5 seconds is given in advance, and the core material Q is placed in the mold cavity 5.
Injection filling. When setting the skin material S,
It is desirable to maintain a slight tension state (tensile state) so that the skin material S does not loosen. The resin pressure in the mold cavity 5 during the injection filling is detected by the resin pressure sensor 64, and the mold clamping control unit 63 controls the mold clamping cylinder so as to maintain the pressure within a pressure range of, for example, 70 to 150 kgf / cm ^2. An operation command is issued to 22 to perform mold clamping pressure control.

FIG. 3 is a graph showing the correlation between the resin pressure in the mold cavity, the holding time, and the degree of damage to the skin material. (A) in the figure is a region where the degree of damage of the skin material S is extremely large (non-formed region), (B) is a region where the degree of damage is extremely small (non-defective region), and (C) is a possibility of damage depending on set conditions. Indicates an unstable region (boundary region). The factors that cause damage to the skin material are roughly classified into three factors: "temperature", "pressure", and "time", all of which are received from the core material molten resin.

The term "pressure" means "resin pressure in the mold cavity". In the present invention, since the resin pressure in the mold cavity is set by controlling the mold clamping pressure, it also means "mold clamping pressure". Is done. In this case, the smaller the "pressure", the less damage to the skin material, but the amount of mold opening during injection filling increases, and resin leakage occurs. To prevent this, a mold with a special structure that does not cause resin leakage If it is, the cost increases. Further, the shaping ability becomes insufficient, and in particular, when the core material is made thinner to reduce the weight and cost, the insufficient capacity becomes remarkable. Therefore, a high pressure state is required, but the skin material is likely to be damaged. From the above, it is necessary to perform control in consideration of “pressure” and “time” at the same time. In the conventional method using the injection molding machine, since the operation is performed in the region D in FIG. 3, the damage to the skin material is large, and the molding failure cannot be avoided.

However, as a result of various studies and examinations by the present applicant, it has been found that if the time is extremely short, the damage to the skin material S is not so large even in a considerably high pressure state, and a short time of about 5 seconds. Then, the upper limit of the resin pressure is 150 kgf
/ Cm ² (region (E) in FIG. 3)
It turns out. However, as can be seen from FIG. 3, as the time (holding time) increases, the allowable pressure for avoiding the damage of the skin material S sharply decreases. Therefore, the upper limit of the resin pressure at the time of shaping the core material resin is set to 150 kgf. / Cm ² and when the resin pressure is 70 kgf / cm ² , the continuable time was within about 5 seconds (FIG. 3 (F)). The resin pressure is 50k
In the region (G) of FIG. 3 of gf / cm ² or less, the skin damage is slight even when the resin is kept for a long time. The opening amount of the mold becomes large, and resin leakage is large, which causes trouble in operation.

In this embodiment, since the sealing effect is provided on the parting surface of the skin material S by gripping the periphery of the skin material S with the mold parting surface, the material and thickness of the skin material S Generally, if the mold opening amount is about 0.5 to 1 mm, resin leakage does not occur without using a specially structured mold. Therefore, in order to keep the mold opening to this level, the lower limit of the resin pressure during injection filling is 7
About 0 kgf / cm ² is appropriate, and the range of the resin pressure during injection filling is set to 70 to 150 kgf / cm ² . Furthermore, in order to minimize the load time of the resin pressure on the skin material S during the injection filling, the injection conditions are set so that the injection filling time is an allowable holding time (in this case, within 5 seconds). did.

"Temperature" means resin temperature. "Temperature", that is, the lower the core material molten resin temperature, the better,
If it is too low, plasticization and flow failure of the core material resin will be caused, resulting in molding failure. Therefore, it is important to select a temperature condition suitable for the resin characteristics.
The temperature is set to around 00 to 230 ° C. Therefore, in order to reduce the amount of heat received by the skin material S from the resin, for example, by lowering the mold temperature using the temperature controller 8, the surface layer of the skin material S is cooled (prevention of temperature rise). Do. However, in this case, if the mold temperature is too low, condensation will form on the mold surface, causing rust on the mold and inducing machine trouble. It is important to hold the mold. In this embodiment, the temperature is set at about 20 to 40 ° C. in consideration of the cooling efficiency of the skin material S and the fluidity of the core material resin Q. As described above, the most suitable pressure range, temperature range, and holding time for the skin integral molding are selected and set from the core material resin characteristics mainly composed of the skin material characteristics and the molded product shape, and the mold clamping pressure, the mold temperature and By controlling the injection time, a molded article of extremely high quality without skin damage can be obtained.

During injection filling, a mold cavity space (core material resin flow path) is formed by a mold opening behavior corresponding to injection filling.
The expansion and degassing effect promotes the filling flow of the core material resin Q. As a result, combined with the heat insulating effect of the skin material S, the resin pressure is reduced and the resin is completely filled into the mold cavity. In addition, the filling can be performed in a short time. The effect of the short-time filling is effective in facilitating the setting range of the injection condition for achieving the above-described minimization of the injection time. In addition, since the outer periphery of the skin material is clamped and held at a low pressure on the mold parting surface, the tension control of the skin material S corresponding to the injection filling of the core material resin (the skin material S becomes part Sliding along the 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. Further, in the two-layer molding method using a conventional press molding machine, means for fixing the skin material is separately required, and there is a problem that the method is complicated.

The amount of resin obtained by adding the amount of cooling, solidification, and shrinkage of the resin is injected and filled, and the amount of the mold opened during filling is set to a minute area of, for example, about 0.5 to 1 mm within a range where the resin does not leak. When the filling is completed, it is almost fully filled (just-packed), so that there is no defect such as a flow mark at the time of shifting to the mold clamping / holding step.
Can be uniformly maintained. In addition, in addition to the above-described molding method of setting the amount of mold opening by controlling the mold clamping pressure, the amount of movement of the movable mold 4 (the amount of mold opening) is detected by the position sensor 65 at the same time as the start of the injection filling, and is set in advance. The mold clamping control unit 63 controls the mold clamping cylinder 2 so that the mold opening amount is set.
2, an operation command may be issued to control the mold clamping position (mold opening amount). In this case, the set value of the mold opening amount is set to, for example, about 0.5 to 1 mm within a range in which the resin does not leak, whereby the same effect as in the case of the mold opening amount setting by the mold clamping pressure control described above is obtained. Furthermore, by setting the mold opening amount corresponding to the amount of resin solidification shrinkage, it is possible to obtain a more complete just pack filling. Control (reduction of resin pressure in the cavity and prevention of resin leakage) can be performed.

After the injection and filling are completed, a mold clamping pressure holding process is started based on a time-out signal of the timer 62 which is started simultaneously with the start of the injection. The set time in this case is set according to the shape of the molded product within the range of the allowable maximum holding time (5 seconds in FIG. 3) determined from the skin material characteristics. In the mold clamping pressure step, mold clamping pressure control is performed so as to maintain the resin pressure at a preset pressure in a pressure range of, for example, ^{2 to} 50 kgf / cm ² . The reason is, as described above, FIG.
(G), the upper limit is 50 kgf / cm ²
The reason is that if it is 50 kgf / cm ² or less, the damage to the skin material S is extremely small even if it is continued for a long time.
If the weight is less than kgf / cm ² , the core material resin Q will have insufficient pressure holding (forming and holding) capability. As described above, by controlling the mold clamping pressure in a state in which the amount of the resin obtained by adding the amount of the cooling solidification shrinkage of the resin is filled into the mold cavity, the entire surface from the mold clamping side corresponding to the cooling solidification shrinkage behavior of the resin is obtained. Good and integrated skin holding, without deformation, warping and damage to the skin material at the same time as the shaping of the core material Q, and with the skin material S and the core material Q evenly adhered by the uniform and uniform pressure-holding action. Goods are obtained. After the cooling of the core material resin Q is completed, the mold is opened, the product is taken out, and the peripheral portion of the skin material Q is trimmed and the gate and runner portions are cut as necessary.

As described above, the feature of the present invention is that, based on the characteristics of the skin material, optimal molding conditions such as pressure, temperature, and time in the integral skin molding are set based on the resin characteristics of the core material and the shape of the molded product. Control of pressure, mold temperature and injection filling time. It is another object of the present invention to inject and fill a resin amount obtained by adding the amount of cooling / solidification shrinkage of the resin and to apply a uniform pressure-holding effect from the mold clamping in accordance with the cooling / solidification shrinkage behavior of the resin. By doing so, it is possible to stably obtain an extremely high-quality integrated skin product without deformation, warpage, or damage to the skin material S. The resin pressure in the above molding method is 70 to 150 kgf / during injection and filling.
cm ² , and the control pattern was ² to 50 kgf / cm ^{2 during} the mold clamping pressure. However, if the pressure range was acceptable, for example, the injection pressure was reduced during injection filling, and once the filling was completed, After the pressure is increased, a control pattern for maintaining the low pressure again is also possible.

In the method of controlling the resin pressure in the above molding, the mold clamping pressure feedback control is performed by detecting the resin pressure by the resin pressure sensor 64 according to the procedure shown in FIG. For example, by converting the mold clamping pressure into a desired resin pressure and setting it,
Although the control accuracy is somewhat deteriorated, there is also a method that utilizes the fact that the mold clamping pressure and the resin pressure are balanced by the mold opening behavior. In the present embodiment, a molded product having a normal mold structure is used for the purpose of obtaining a skin-integrated molded product having excellent surface properties at a lower cost. Similar molding can be performed using a mold having a structure. However, in the case of individual parts, it is unavoidable that the cost is somewhat high, but since the mold opening during injection filling can be set large, the resin pressure in the mold cavity is thoroughly reduced, and the skin material is damaged. When the main purpose is prevention, a great effect can be obtained, but it is not preferable because complicated control such as prevention of a flow mark defect is required.

There is no particular limitation on the skin material S, and it 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. In the present embodiment, the sheet material S is used in the form of a sheet. However, the material S may be preformed in advance into a shape roughly conforming to the properties of the molded product.

For the core material Q, a thermoplastic resin such as PP or PE is used, and talc, fiber, etc. are added as necessary.

[0023]

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) A good molded product without deformation and warpage can be obtained by a uniform pressure-holding action from the mold clamping side in accordance with the cooling, solidification and shrinkage behavior of the resin. (3) A mold having a shear edge structure or the like and ancillary equipment for holding a skin material are not required, and low cost and improved productivity can be realized.

[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 flowchart of a skin integral molding process according to an embodiment of the present invention.

FIG. 3 is a graph showing a correlation among a resin pressure in a mold cavity, a holding time, and a degree of damage to a skin material in a skin integral molding step according to an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed board 2 Movable board 3 Fixed mold 4 Movable mold 5 Mold cavity 8 Temperature controller (temperature controller) 10 Mold device 20 Mold clamping device 22 Mold cylinder 30 Injection device 32 Barrel 34 Screw 36 Screw blade 38 Hopper 39 Nozzle 40 Injection cylinder 42 Hydraulic motor 50 Hydraulic supply source 52 Hydraulic control valve 60 Control device 61 Injection control unit 62 Timer 63 Mold clamping control unit 64 Resin pressure sensor 65 Position sensor 69 Hydraulic control valve 70 Hydraulic supply source 100 Injection molding machine Q Core material (core resin) S Skin material

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 9:00

Claims (6)

[Claims] A mold material is clamped by interposing a skin material between a pair of left and right or upper and lower molds facing each other, and then a core material is inserted into a mold cavity formed by the skin material and the two molds. Injection molding of the molten resin to form the skin material and the core material integrally, wherein a mold clamping pressure that allows the mold to open with the pre-filled resin pressure is applied to the mold. After applying the load, the molten resin amount obtained by adding the cooling solidification shrinkage amount of the molten resin is injected and filled, and the resin pressure in the mold cavity is held in multiple stages according to the molding process within a set pressure range. A method of integrally molding a skin, comprising controlling a mold clamping pressure. 2. During the injection filling, the resin pressure in the mold cavity is set to 70 to 150 kgf / cm ^2, and thereafter, 2 to 50 kgf / cm 2.
^{2. The} method according to claim 1, wherein the pressure is reduced to kgf / cm < ² >. 3. The pressure switching of the resin pressure in the mold cavity is performed when injection filling is completed or when a set time within 5 seconds from the start of injection filling is reached.
The integrated skin molding method as described in the above. 4. The method according to claim 1, wherein the injection filling time is within 5 seconds. 5. The mold temperature during molding is kept as low as possible within a range that does not cause dew condensation.
The integrated skin molding method as described in the above. 6. The method according to claim 1, wherein, during the injection filling, the amount of movement of the mold is controlled so that the amount of mold opening is set in advance.