JPS61246037A - Stamping device for thermoplastic resin sheet - Google Patents

Abstract

PURPOSE:To eliminate the facilities and space to provided a conveying means for carrying a resin sheet in a molding machine and prevent thin wall portions in a resin molded part complicated in shape from developing by a structure wherein horizontally splitting molding tools are arranged just in front of an extruder die, through which the resin sheet is extruded. CONSTITUTION:When a storing amount detector 22 detects that the determined amount of molten resin is stored, a central processing unit 26 stops the rotation of a feed screw 4 and at the same time changes over a solenoid-operated on-off valve 23 to a hydraulic pressure supply side so as to keep on giving setting signals for a pressure loading P corresponding to the position S of a pressure piston 11 through a D/A converter 27, a servo-amplifier 28 to a solenoid-operated proportioning pressure valve 24. As a result, the molten resin is extruded from an extruder die 8 in the form of a resin sheet 2 having the thickness, which is changed in response to the change of the pressure loading P. After the predetermined length of the resin sheet 2 is extruded, the solenoid-operated on-off valve is changed over to a pressure release side and at the same time a right and a left molding tools 14 and 15 are shifted by the actuating instruction sent from the central unit 26 in the pressing directions with respect to the resin sheet 2 hung down from the extruder die 8 in order to stamp the resin sheet 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a stamping molding apparatus for thermoplastic resin sheets.

(Prior art) In general, stamping molding equipment for thermoplastic resin sheets consists of a sheet cutting machine, a sheet conveying machine, a stamping molding machine, and a trimming machine on the line, in contrast to an extruder that extrudes the resin sheet laterally. They are often configured by arranging them (for example, see Japanese Unexamined Patent Publication No. 57-60.523).

In this case, in the above-mentioned stamping molding machine, the resin sheet is placed on the lower mold, and the resin sheet is pressure-molded by the downward stroke of the upper mold. The above-mentioned sheet conveyor is required to carry in from the side, and additional consideration must be given to prevent the resin sheet from cooling during conveyance. Also,
The resin sheet extruded and conveyed from the extruder has a constant thickness, but when it is stamped into a relatively complicated shape, thinner parts may occur locally.

That is, for example, when obtaining a resin molded product a with relatively large uneven steps as shown in FIG. 2, the resin sheet is first placed on the molding surface of the lower mold. The part in contact with the convex surface C cools and hardens first, so that the elongation during molding is small. Also, as the upper mold descends, this contact part contacts the convex surface of the molding surface of the upper mold. The contact between the convex portions of both molds and the corners of the convex surfaces is suppressed from sliding. Therefore, the resin sheet has the concave portion d of the resin molded product a.
The portion that becomes the stepped portion f between the convex portion e and the convex portion e has a thinner wall on both sides f.

(Object of the Invention) In view of the above points, the present invention has been made in view of the fact that in conventional stamping molding, equipment space is required to provide a conveyance means for carrying the resin sheet into the molding machine, and in addition, it is difficult to mold resin sheets with complex shapes. This is an attempt to solve the problem that thin parts may occur when obtaining a product.

(Structure of the Invention) In the thermoplastic resin sheet stamping molding apparatus of the present invention, a molten thermoplastic resin stored in a storage chamber is pressurized by a pressurizing means to form a sheet from an extrusion die and extrude it downward. The extruder is equipped with a pressurizing force control means for changing the pressurizing force of the pressurizing means, and a left-right split mold is disposed at the extrusion position of the resin sheet. In this case, the thickness of the resin sheet extruded from the extrusion die changes by controlling the above-mentioned pressure force, and the extruded resin sheet is pressure-molded into a resin molded product by the left and right molds at the extrusion position. .

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In the thermoplastic resin sheet stamping molding apparatus shown in FIG. 1, 1 is an extruder that turns thermoplastic resin into a resin sheet 2 and extrudes it downward; 6 is a stamping machine installed at a position where the extruder 1 extrudes the resin sheet 2; It is a molding machine.

The extruder 1 has a storage chamber 6 connected to the front end of a heating cylinder 5 into which a feeding cylinder 4 is inserted, and heats thermoplastic resin such as polyester, polypropylene, polyvinyl chloride, etc. introduced from a hopper (not shown). The thermoplastic resin is heated in a tube 5, fed by a feeding screw 4, and stored in a molten state in a storage chamber 6. The storage chamber 6 has a cylindrical shape extending in the vertical direction, and has a tapered wedge-shaped extrusion opening (
An extrusion die 8 with the slit 7 opened downward is attached. A pressurizing piston 11 is fitted into the storage chamber 6 so as to be able to move up and down in response to hydraulic pressure applied from a hydraulic source 9 through a hydraulic passage 10 to pressurize the stored resin and push it out from the extrusion die 8. A piston rod 12 inserted and fixed to the pressurizing piston 11 projects above the storage chamber 6, and the pressurizing force by the pressurizing piston 11 is controlled by a pressurizing force control means 13.

On the other hand, the stamping molding machine 3 is equipped with a molding die 14.15 divided into left and right parts at the extrusion position of the resin sheet 2, and a molding surface 16.17 having unevenness corresponding to both molding molds 14.15 is formed. There is. Both molds 14.15
are supported by piston rods 20 and 21 of pressure cylinder devices 18 and 19, each having a stroke direction perpendicular to the extrusion direction of the resin sheet 2.

Next, the specific configuration of the pressurizing force control means 13 will be explained.

That is, in the pressurizing force control means 13, 22 is a storage amount detector that detects the amount of resin stored in the storage chamber B from the position of the pressurizing piston 11, and 23 is a storage amount detector that is interposed in the hydraulic passage 10 and detects the oil pressure for the storage chamber B. The electromagnetic on-off valve 24 supplies and releases the electromagnetic on-off valve 23 and receives an input signal (current value) of the hydraulic pressure provided in the hydraulic passage 10 on the upstream side of the electromagnetic on-off valve 23.
This is an electromagnetic proportional pressure valve that changes the pressure according to the The detection signal (analog signal) by the storage amount detector 22 is A/D
The converter 25 converts it into a digital signal and inputs it to the central processing unit 26, which outputs an operating signal to the electromagnetic on-off valve 23 and also sends a pressure setting signal (digital signal) to the electromagnetic proportional pressure valve 24. is D/
The A converter 27 converts it into an analog signal, and the servo amplifier 28 converts it into a current value, which is then output.

Specifically, information regarding the thickness t of each part of the resin sheet 2 extruded by the extruder 1 is input to the central processing unit 26 . From this thickness information, the resin extrusion amount Q corresponding to the extrusion length β of resin :/--)2 is determined, and this resin extrusion amount Q corresponds to the position S of the pressurizing piston 11 in the storage chamber 6. On the other hand, the thickness of the resin sheet 2 extruded from the extrusion die 8 corresponds to the pressure difference between the pressure in the storage chamber B and the atmospheric pressure due to the swell phenomenon. In other words, the greater the pressure difference, the thicker the resin sheet 2 becomes, so the pressing force P of the resin in the storage chamber 6 to obtain the thickness t can be determined. Based on the thickness information, the central processing unit 26 determines the relationship between the position S1 of the pressurizing piston 11, the amount of resin stored in the storage chamber 6, and the pressurizing force P. When the resin necessary for extruding the resin sheet 2 of a predetermined shape is stored in the electromagnetic proportional pressure valve 24, an injection signal is given to the valve 6, and at the same time, a detection signal is received from the storage amount detector 22 to the electromagnetic proportional pressure valve 24. A pressure setting signal corresponding to the position of the pressurizing piston 11 is output.

II The thickness of each part of the Jffi sheet 2 is set so that the part with a large elongation amount during stamping molding is thicker, so that the thickness of each part of the resin molded product after stamping molding is approximately equal. The portions with a large amount of elongation are the portions formed on the slopes of the molding surfaces 16.degree.

Therefore, when performing stamping molding in the above embodiment, first, information regarding the thickness of the resin sheet 2 to be extruded is inputted to the central processing unit 26 and then transferred to the pressurizing piston/11.
The relationship between the position S and the pressing force P is set. Then, the electromagnetic on-off valve 26 is opened (on the return side) as shown, and the feed system screw 4 is rotated to store the molten resin in the storage chamber B.

When the storage amount detector 22 detects that the specified amount of molten resin has been stored, the central processing unit 26 stops the rotation of the feed system screw 4, switches the electromagnetic on-off valve 26 to the hydraulic pressure supply side, and pressurizes the resin. A setting signal for the pressurizing force P corresponding to the position S of the piston 11 is continuously applied to the electromagnetic proportional pressure valve 24 via the D/A converter 27 and the servo amplifier 28. As a result, the pressurizing piston 11 pressurizes the molten resin in the storage chamber 6 (pressing force P) with the oil pressure determined by the electromagnetic proportional pressure valve 24, and the thickness of the molten resin increases in accordance with the change in the pressurizing force P. The resin sheet 2 is extruded from the extrusion die 8 as a resin sheet 2 that has a change in color.

Then, when the resin sheet 2 is extruded for a predetermined length, the electromagnetic on-off valve 26 is switched to the release side, and the central processing unit 26 sends an operation command to the left and right sides of the resin sheet 2 hanging down from the extrusion die 8. The molds 14 and 15 are stroked in the pressing direction, and stamping is performed. and,
During stamping molding, pressure is held and the resin molded product is released from the mold, and the time between them is used to store molten resin for the next stamping molding.

In the above-mentioned stamping molding, the elongation of the resin sheet 2 during molding is small in the portion that is in contact with the convex surface of the molding surface 16i7 of the drawing molds i4 and 15, and the elongation of the portion molded on the sloped portions of both molding surfaces 16 and 17 is small. However, in this part where the elongation is large, the thickness of the resin sheet 2 is large, so even if the elongation is large, the resin sheet 2 is not thinner than the other parts.

In the above embodiment, both the left and right molds 14 and 15 are movable, but one may be fixed and only the other movable.

(Effects of the Invention) According to the present invention, the resin 7-t extruded from the extrusion die does not need to be transported, so it can be molded immediately without reheating, and the molding time can be shortened. ,
The thickness of each part of the resin sheet can be changed by controlling the pressure applied during extrusion of the resin sheet, so by making the parts where the elongation is large during molding thicker, it is possible to reduce the thickness of local thin parts of the resin molded product. can be prevented from occurring.

[Brief explanation of drawings]

FIG. 7 is a configuration diagram of a stamping molding apparatus according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view showing a portion of a resin molded product that is likely to become thin. 1...Extruder, 2...Resin sheet, 3
... Stamping machine, 6 ... Storage chamber, 8 ... Extrusion die, 11 ... Pressure piston, 16 ... Pressure force Control means, 14.15
・・・・・・Molding mold

Claims (1)

[Claims] (1) A storage chamber for storing a thermoplastic resin in a molten state, a pressurizing means for pressurizing the resin in the storage chamber, and an extrusion die for extruding the pressurized resin in the storage chamber downward into a sheet. , for an extruder equipped with a pressurizing force control means for controlling the pressurizing force of the pressurizing means and changing the thickness of the resin sheet extruded from the extrusion die; A thermoplastic resin sheet stamping molding device characterized by being equipped with a mold.