JP3035811B2 - Sheet thermoforming method and apparatus - 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 and apparatus for thermoforming a sheet.

[0002]

2. Description of the Related Art As a press molding method for a thermoplastic resin sheet, an end of a plastic material is pressed with a blank holder,
A method of press-molding with a punch has been proposed (see Japanese Patent Publication No. 60-21526).

FIG. 14 is a sectional view of such a conventional sheet thermoforming apparatus. FIG. 14A is a sectional view of the sheet thermoforming apparatus before deep drawing, and FIG. FIG. 3 is a cross-sectional view showing a drawn state.

[0004] In this apparatus, the plastic material 123 is placed on the die top surface 116 b, after the upper surface of the plastic material 123 has been pressed by the bra down Kuhoruda 109 is molded by the punch 101. Plastic material 123 against bra down Kuhoruda 109 and the die 116, since the held down in the clearance is not a condition and the a plastic material 123 bra down Kuhoruda 109, frictional resistance between the die 116 is increased, the plastic material 123 It stretches during molding. That is, the thickness of the molded product becomes uneven.

Incidentally, 116a is a die cavity , 12
4 is a tool.

Also, in the drawing press forming using a punch, the end of the material is extruded in a predetermined size and direction in relation to the vertical movement of the punch, so that it is possible to form even a portion where the material inflow is small, and the formability is improved. Has been proposed (see JP-A-60-190327).

In this apparatus, the inflow of the material is performed by external force without using the inflow of the material itself. Therefore,
In the case of molding a material whose stiffness is weakened by heating, an external force of the material may act on an extra pushing force or, conversely, a tensile force. At that time, the material may be wrinkled or may be stretched to reduce the thickness of the material.

Further, in the drawing press forming using a punch, a bead is formed on the outer peripheral portion of the material during the forming to control the tension of the material and simultaneously press the upright wall surface to prevent wrinkles from being generated. (See Japanese Patent Application Laid-Open No. 63-60728).

This device is characterized in that a tension is applied by a bead and a mechanism for pressing a vertical wall surface in a molding process is held in a mold.

When molding a material having a weakened tensile force due to heating, if a bead is attached to the outer peripheral portion of the material as in this apparatus, a large tension is applied to the material,
At present, there is a drawback that the material is stretched, and satisfactory thermoforming has not been performed.

[0011]

The above description relates to a press forming method using a wrinkle holding plate portion in terms of a mold structure. without the characteristics of the material of interest of the present invention (a thermoplastic resin sheet), tension on the material for the material viscosity have low during molding (soft) greatly affects the formability.

In view of the above-mentioned circumstances, the present invention provides a method for thermoforming a thermoplastic resin sheet material or a fiber reinforced composite sheet material containing a thermoplastic resin as a main constituent material, in which the thickness of the product becomes uniform and partially It is an object of the present invention to provide a thermoforming method and an apparatus for a sheet which can be easily formed without unevenness in thickness and unevenness of a bottom portion and a side portion of a product, and can be easily formed.

[0013]

According to the present invention, in order to achieve the above object, (A) at the time of forming a thermoplastic sheet, the sheet is not completely pressed against the sheet thickness, and a predetermined clearance is provided. The sheet is drawn and molded while maintaining the sheet's slipperiness, suppressing sheet elongation, and preventing wrinkles from occurring.

(B) At the time of forming a thermoplastic sheet, the clearance of the holding plate is reduced and the pressure is applied by a forming die, and at the same time, the clearance is gradually increased so that the sheet has slipperiness and freedom of deformation. Then, wrinkle-free molding with less sheet elongation is performed.

(C) For the purpose of minimizing the sheet elongation at the time of the draw-in molding, it is possible to delicately control the pressing force of the wrinkle suppressing plate portion. For a material having a large elongation, a certain clearance (gap) is used. (In general metal materials, molding is performed with the wrinkle pressing plate completely pressed. However, since the thermoplastic sheet is easily stretched, the product thickness is increased.) Is greatly affected by the pressure of the holding plate).

(D) The pressure control of the pressing plate portion using the air cylinder is performed by controlling the pressing force of the pressing plate by controlling the air pressure, so that the pressing force can be controlled in accordance with the sheet deformability during molding.

As a sheet to be molded, a fiber-reinforced thermoplastic resin sheet and a fiber-reinforced thermoplastic resin sheet (reinforced with short fibers, long fibers, unidirectional continuous fibers, woven continuous fibers, etc.) are used.

During the thermoforming of a thermoplastic resin sheet material or a fiber reinforced composite sheet material mainly composed of a thermoplastic resin, the thickness of the product is uniform and the thickness of the product is not partially uneven, and the bottom and side portions of the product are not formed. Can be easily formed.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a sheet thermoforming process according to a first embodiment of the present invention.

In this figure, reference numeral 1 denotes a sheet (material) (a fiber-reinforced thermoplastic resin sheet and a fiber-reinforced thermoplastic resin sheet (reinforced with short fibers, long fibers, unidirectional continuous fibers, woven continuous fibers, etc.)). ] Is used. 2 is a mold type, 3
Is a core type, 4 is a mold type side pressing plate, and 5 is a core type side pressing plate.

First, as shown in FIG. 1A, a sheet 1 is carried between a mold mold 2 and a core mold 3 by a material clamping device (not shown).

Next, as shown in FIG.
Is placed on the core mold 3.

Next, as shown in FIG. 1C, the mold 2 starts to press the sheet 1.

At this time, the periphery of the four corners of the sheet 1 is shown in FIG.
A waving phenomenon (wrinkle) occurs as shown in (D). In this state,
Further, when the mold 2 is lowered, the core-side pressing plate 5 starts to lower.

Next, as shown in FIG. 1E, pressure molding is performed.

What is important here is that in FIG. 1A, the upper surface of the core-side pressing plate 5 is disposed below the upper surface of the core die 3 by a distance a. This is sheet 1
This is for maintaining a predetermined clearance between the core and the pressing die. If the distance a is zero, the sheet 1
Is placed on the core mold 3, and at the same time, the core mold side holding plate 5
, And the sheet 1 remains in one plane.
When the mold 2 is lowered in this state, the sheet 1 comes into close contact with the upper and lower pressing plates 4 and 5, and the frictional resistance between the sheet 1 and the upper and lower pressing plates 4 and 5 increases. As a result, at the time of molding, the sheet 1 elongates.

The sheet 1 is clamped from above and below with the mold-type holding plate 4 and the core-type holding plate 5 while maintaining a predetermined clearance, and the sheet 1 is pressed up and down at the time of molding under a certain pressing force. By being drawn into the mold while sliding from the sheets 4 and 5, the sheet 1 can be formed without elongating the sheet 1 while preventing wrinkles from occurring.

Further, it is possible to adjust the pressing force of the pressing plate during the molding, and furthermore, it has a clearance adjusting mechanism.
Can automatically change the adjustment of the clearance amount during molding.

Further, the thermoforming process will be described in detail with reference to FIG.

In FIG. 1A, after heating the sheet 1,
It carries the sheet 1 between the cavity mold 2 and the core mold 3, dropping sheet 1 on the core mold 3 and the core mold side holding plate 5, the sheet 1 in the cavity mold side pressing plate 4 while lower the cavity mold 2
Press the peripheral part from above. At this time, the sheet 1 is held down by the sheet conveying device (not shown) without being dropped, and is lowered at the same time as the mold 2. The sheet 1 is placed on the core die 3 and the core type side holding plate 5, and then the conveying device clamper is moved. The sheet 1 may be opened to open. Further, as a method of holding down the sheet 1, there are a method of applying pressure through the core type side holding plate 5 and a method of holding a certain clearance between the upper and lower holding plates 4 and 5 with spacers and holding. is there.

Since the sheet 1 is heated and softened,
When placed on the core mold 3 and the core mold side holding plate 5, FIG.
(B). Here, when the mold 2 is lowered , the central portion of the sheet 1 enters the concave portion of the mold 2 while the sheet 1 is pressed downward by the mold-type pressing plate 4. When the mold 2 is further lowered, FIG.
As shown in (C), there is a predetermined gap between the upper and lower pressing plates 4 and 5. At this time, the periphery of the four corners of the sheet 1 is as shown in FIG.
A waving phenomenon (wrinkle) occurs as shown in (D). In this state,
Further, when the mold 2 is lowered, the core-side pressing plate 5 starts to lower. At this time, the supporting force of the core-type pressing plate 5 for supporting the sheet 1 is not enough to extend the wrinkles.

Accordingly, the core-type pressing plate 5 descends while wrinkles are formed around the four corners of the sheet 1.

As the pressure forming of the sheet 1 proceeds, the rigidity of the wrinkles of the sheet 1 increases.
Is gradually increased, and pressure molding is performed as shown in FIG.

Depending on the sheet 1, even if the pinching force is increased, the rigidity of the wrinkles of the sheet 1 is increased.
The gap of No. 5 may be widened.

At the time of pressurization, cooling starts when the sheet 1 comes into contact with the surface of the mold, and the mold is opened when the temperature has dropped below a predetermined temperature, and the product is taken out.

The mold surface temperature is determined by the type of sheet, thickness and the like. Generally, a higher mold temperature results in a product having excellent surface properties, but requires a longer cooling time and lowers productivity.

FIGS. 2 to 5 show a core-type pressing plate driving device.

FIG. 2 shows a system having a holding plate driving mechanism in the apparatus, FIG. 3 shows a system in which an air cylinder 6 is incorporated in a mold, and FIGS. 4 and 5 show a system in which a spring 8 is incorporated in a mold. You.

The embodiment shown in FIG. 2 is an example in which the core-type pressing plate 5 is supported by the air cylinder 6, and the air cylinder 6 is attached to the device base 7.

As described above, the air cylinder 6 is provided as a pressing plate driving mechanism in the apparatus, and the pressing plate portion can be operated separately from the core mold 3 and the mold 2.

In the embodiment shown in FIG. 3, the air cylinder 6 is attached to the core mold 3. A hydraulic cylinder may be used instead of the air cylinder 6.

[0043] Thus, by driving the sheet holding plate through the force of the air cylinder 6, so as to descend together with the cavity mold 2 while the tension applied to the seat 1 with the downward movement of the cavity mold 2.

In the embodiment shown in FIG. 4, guide shafts 9 are erected at the four corners of the core mold 3, and the guide shafts 9 are made to pass through holes formed in the core mold side pressing plate 5, and springs 8 are formed.
Is provided between the core mold side pressing plate 5 and the core mold 3. A flange 10 is formed at the upper end of the guide shaft 9. Notch portions 4 a are provided at the four corners of the mold-type side holding plate 4.

In the embodiment shown in FIG. 5, a guide shaft 9 is suspended from the core-type holding plate 5 and penetrated through a hole formed in the core die 3, and a spring 8 is connected to the core-type holding plate 5 and the core die 3.
It is provided between. A flange 10 is formed at the lower end of the guide shaft 9.

In FIGS. 4 and 5, the sheet holding plate is driven by the force of the spring so that the sheet is lowered together with the mold while applying tension to the sheet as the mold is lowered.

The driving method of the sheet pressing plate portion includes the type of sheet to be used (whether a high pressing force is required),
The size of the mold to be used is fixed, and it is used depending on whether it is used as a dedicated machine. By having the holding plate driving mechanism in the apparatus, the mold manufacturing cost is lower than installing the holding plate driving mechanism in each mold.

FIG. 6 is a view showing a mechanism (part 1) for sandwiching a sheet of the sheet thermoforming apparatus of the present invention. The mechanism has a spacer 11 on the side of the mold-type pressing plate 4, and maintains a certain clearance. The sheet 1 is sandwiched. The spacer 11 may be installed on the core-type holding plate 5,
And the height of the upper surface of the core mold 3 may be the same. The thickness of the spacer 11 is larger than the thickness of the sheet 1.

As described above, the pull-in molding is performed while generating a constant frictional force in the sheet while maintaining the clearance between the pressing plates by using the spacer.

FIG. 7 is a view showing a mechanism (No. 2) for sandwiching a sheet of the sheet thermoforming apparatus according to the present invention.
2 shows a mechanism by which the length of the spring 8 can be adjusted.

As described above, by adjusting the length of the spring and adjusting the spring force, it is possible to control the pressing force of the pressing plate corresponding to the formed sheet.

FIG. 8 is a view showing a clearance adjusting mechanism (part 1) of the holding plate of the sheet thermoforming apparatus of the present invention, wherein the clearance at the time of molding can be arbitrarily changed.

In this mechanism, the spacer pins 13 can be moved in and out, and a jack having an AC servomotor 14 detects the amount of space in and out of the spacer pins 13 with a potentiometer 15. Also, the spacer pins 13
Controls the size between the upper and lower holding plates 4 and 5. The jack may be provided on either the core type side holding plate 5 or the mold type 2.

As described above, the clearance can be adjusted by detecting the clearance with the potentiometer 15 incorporated in the mold, operating the AC servomotor 14 and taking the spacer pins 13 in and out.

FIG. 9 is a view showing a clearance adjusting mechanism (part 2) of the pressing plate of the sheet thermoforming apparatus of the present invention. The clearance detecting sensor 16 is incorporated in the pressing plate.
This figure shows a mechanism capable of detecting a clearance amount and performing pressure forming at an optimum pressing plate interval.

Reference numeral 17 denotes a controller, which receives a detection signal from the clearance detection sensor 16 and measures a dimension between the upper and lower pressing plates 4 and 5 to control the expansion and contraction of the air cylinder 6 based on the signal. Control. 1
9 is a pressure source of the air cylinder 6.

Based on the clearance detection sensor 16,
In the method of controlling the size between the upper and lower pressing plates 4 and 5, a driving device such as a screw jack may be used instead of the air cylinder 6.

Also in this embodiment, the air cylinder 6 is provided by the pressure regulator 18 via the controller 17 by having a clearance adjusting device, detecting the amount of clearance by the clearance detecting sensor 16 incorporated in the mold, and feeding it back. Adjust pressure. In the stage of sandwiching the sheet 1 between the holding plates, the pressing force of the holding plate is reduced, and as the sheet 1 is deformed as the sheet is formed, the pressing force of the holding plate is made constant or increased, thereby preventing the occurrence of wrinkles. .

FIG. 10 is a view showing a mechanism (No. 3 ) for sandwiching a sheet of the sheet thermoforming apparatus of the present invention. FIG. It is.

In this embodiment, the mold 22 has a notch 22a on the outer periphery of the lower end. Reference numerals 24 and 25 are holding plates. The holding plate 24 is supported movably in the vertical direction with respect to the mold 22.

The guide shaft 29 erected on the holding plate 24 is attached to the bracket 26 attached to the mold 22.
Penetrates through. A spring 27 is interposed between the bracket 26 and the holding plate 24.

[0062] compression force of the spring 27 is larger than the sheet pressing force of the pressing plate 25, the presser plate 25 is the same as the pressing plate 5 described above [refer to FIG. 10 (A)].

[0063] In this embodiment, when there is a folded shape to the product perimeter draws sheet 1 at the core mold 23 [see FIG. 10 (B)], the pressure immediately before the start or just after, the core mold side holding plate increases the 25, accordingly, that the cavity mold side holding plate 24 is raised together via a spring force [see FIG. 10 (C)], forming a folded portion while applying a tension in the sheet.

In addition, the conventional thermoforming method of the sheet by vacuum or pressure molding is different from other injection molding methods and the like in that it is low-pressure molding, so that the mold cost is low, and as a result, it is suitable for the production of large parts. And has already been applied in a wide range of fields. In particular, unlike the conventional method, this molding method enables uniform thickness molding of products and is a draw-in molding, so in addition to thin resin sheets, thick sheet sheets that are difficult to form with the conventional technology other than thin resin sheets and reinforced It can also be used for molding a resin sheet containing fibers. Also, since it is a low-pressure molding, it can be applied to molding of large parts, so that application in a wide range of fields can be expected.

[0065]

[Example 1] An ABS sheet having a thickness of 3.5 mm and a product size of 520 (width: w) x 720 (length: l) x 100
FIG. 11 shows the results obtained by measuring the thickness of the product from the corner to the side when molding a (height: h) mm shape, and comparing the vacuum molded product with the main molded product. The maximum thickness reduction rate of the vacuum formed product was 55%, while that of the formed product was 17%, confirming that the reduction in the thickness was small.

[0066]

Example 2 FIG. 12 shows the results of measuring and comparing the sheet heating time and the cooling time in the vacuum forming method and the main forming method using an ABS sheet having a thickness of 2.8 mm. It was confirmed that since the molding temperature was low, the heating time when the same heater was used was short, and the time required for cooling was also short because the sheet temperature was low.

[0067]

[Embodiment 3] By adjusting the clearance of the sheet pressing plate to an optimum value with a spacer using an ABS sheet having a thickness of 2.8 mm, it is possible to form a product without wrinkles. FIG.
Reference numeral 3 indicates the result of measuring the correlation between the frame clearance and the occurrence of wrinkles in the product part. The occurrence of wrinkles can be prevented by setting the frame clearance to 3 to 4 mm with respect to the plate thickness of 2.8 mm.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0069]

As described above, according to the present invention, the following effects can be obtained.

(A) Since the sheet is formed while being drawn in, a product having a uniform thickness and no wrinkles can be obtained.

(B) Since a product having a uniform thickness can be formed, the sheet thickness to be used can be kept to a necessary minimum, and partial reinforcement as in the prior art becomes unnecessary.

As a result, it is possible to reduce material costs and work costs.

(C) Further, since the molding is performed at a low temperature, even a material having a large elongation, which has been difficult to form by vacuum / pressure molding, has a high resin viscosity due to the low temperature, so that molding can be performed while suppressing elongation.

(D) Further, since it is a draw molding, a force for stretching the material is not required, so that it is possible to mold a thick plate material which is difficult to form by vacuum / pressure molding.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a sheet thermoforming process according to a first embodiment of the present invention.

FIG. 2 is a view showing a core-type pressing plate driving device (1) of the sheet thermoforming device of the present invention.

FIG. 3 is a view showing a core-type pressing plate driving device (part 2) of the sheet thermoforming device of the present invention.

FIG. 4 is a view showing a core-type pressing plate driving device (part 3) of the sheet thermoforming device of the present invention.

FIG. 5 is a view showing a core-type pressing plate driving device (part 4) of the sheet thermoforming device of the present invention.

FIG. 6 is a view showing a mechanism (No. 1) for sandwiching a sheet of the sheet thermoforming apparatus of the present invention.

FIG. 7 is a view showing a mechanism (No. 2) for sandwiching a sheet of the sheet thermoforming apparatus of the present invention.

FIG. 8 is a diagram showing a clearance adjusting mechanism (part 1) of a holding plate of the sheet thermoforming apparatus of the present invention.

FIG. 9 is a view showing a clearance adjusting mechanism (part 2) of a pressing plate of the sheet thermoforming apparatus of the present invention.

FIG. 10 is a view showing a mechanism ( No. 3) for sandwiching a sheet of the sheet thermoforming apparatus of the present invention.

FIG. 11 is a view showing the result of comparison between a conventional vacuum molded product and a molded product of the present invention.

FIG. 12 is a diagram showing the results of measuring and comparing sheet heating time and cooling time between a conventional vacuum forming method and a forming method of the present invention.

FIG. 13 is a diagram showing a measurement result of a correlation between the frame clearance of the molded article of the present invention and the occurrence of wrinkles in a product part.

FIG. 14 is a sectional view of a conventional sheet thermoforming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sheet (material) 2, 22 Cavity type 3 Core type 4 Cavity type side holding plate 4a, 22a Notch 5 Core type side holding plate 6 Air cylinder 7 Device base 8, 27 Spring 9, 29 Guide shaft 10 Flange 11 Spacer 12 Adjustment nut 13 Spacer pin 14 AC servomotor 15 Potentiometer 16 Clearance detection sensor 17 Controller 18 Pressure regulator 19 Air cylinder pressure source 24, 25 Press plate 26 Bracket

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 51/00-51/46 B29C 33/12-33/18

Claims (7)

(57) [Claims] [Claim 1] using the core mold and cavity mold, a sheet pressing plate arranged around said core mold and the cavity mold section, even pressing
There is an actuator that moves the plate in the forming direction with respect to the core mold.
The holding surface of the holding plate has a thicker space than the sheet.
A sheet is placed between the pressing plates at a time interval larger than the thickness of the sheet during molding, and tension is applied thereto. A method for thermoforming a sheet, characterized in that a decrease in the thickness of the sheet is minimized. 2. An operating device for using a core mold and a mold, disposing a sheet press plate around the core mold and the mold section, and moving the press plate in a molding direction with respect to the core mold. By detecting the clearance of the pressing plate with a sensor and feeding back to the controller, the moving amount of the operating device is adjusted, and the clearance is controlled in accordance with the molding state to form the sheet. Thermoforming method of sheet. 3. The sheet thermoforming method according to claim 1 , wherein the amount of protrusion of the spacer is adjusted. 4. The sheet thermoforming method according to claim 1, wherein the material is drawn in by the core mold and the mold, and the core-type pressing plate is moved to the mold immediately before or immediately after the molding is completed. Forming a folded shape while applying tension to the sheet to prevent wrinkles from occurring. 5. An actuating device having a core mold and a mold, disposing a sheet press plate around the core mold and the mold, and moving the press plate in a molding direction with respect to the core mold. A sensor for detecting a clearance of the holding plate,
A controller that reads an output from the sensor,
Means for adjusting the amount of movement of the actuator by the controller based on a signal from the sensor and performing clearance control in accordance with the state of molding. 6. have a core mold and cavity mold, a sheet pressing plate is disposed around said core mold and the cavity mold section, the actuating apparatus is provided for moving the molding direction the presser plate against the core mold, A sheet thermoforming apparatus, wherein a spacer thicker than a sheet is provided on a holding surface of the holding plate. 7. A thermoforming apparatus of sheets according to claim 6, thermoforming device for a seat characterized in that it comprises means for adjusting the amount of projection of the spacer.