JPH0617023B2 - Molding method and molding apparatus for plastic molded product - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plastic molding having a preforming step and a main forming step, and particularly to a molding method and a molding suitable for precision molding and supply assembly of small plastic parts. Regarding equipment, etc.

[Conventional technology]

Conventionally, a molding method having a preforming step and a main forming step is known.

The one described in JP-A-57-151321 is also similar to this type of molding method.

In this publication, a preform injection-molded around a mold core for injection molding by a preform station is moved to a final molding station, and the preform molded around this core is compressed from an air valve of the core. Techniques for blowing air and blow molding are described.

[Problems to be Solved by the Invention]

In the above-mentioned conventional technique, the resin as the raw material is not stressed more than necessary, and therefore, consideration is insufficient in terms of molding.

For example, in the injection molding method, in order to compensate for the injection pressure loss that is inevitably caused by flowing a narrow and long flow path, it is necessary to apply an injection pressure higher than necessary to the resin. Therefore, there is a problem that the internal strain of the resin becomes large and the precision of the molded product is lowered, and at the same time, the specifications and size of the molding machine become unnecessarily large. In addition, since the flow direction is unidirectional, it has a strong dorsitropism.

An object of the present invention is to provide a molding method and the like suitable for obtaining a molding method or a molded product that does not apply more stress than necessary in the molding process in order to obtain a highly accurate molded product with small distortion. It is in.

[Means for Solving the Problems]

The present invention, when molding a plastic molded product, as a method of obtaining a molded product with a uniform resin flow and a low strain, plasticize the pellets, and discharge from a nozzle to perform pre-molding.
When the preformed preform is main-molded with the upper and lower molds to obtain a resin molded product, the preform is preformed at a low pressure to a shape close to that of the finished product, and then the upper and lower metal molds are used. There is a molding method for plastic molded articles that obtains low distortion molded articles by equalizing the flow of molten resin by clamping with a mold at high pressure. The heating cylinder and the nozzle are arranged in a straight line to form a preforming unit, and the forming cylinder and the upper and lower molds are arranged in parallel with the preforming unit to form a main forming unit. A transfer part that moves in the cross direction with respect to the main molding unit is provided, a preforming cavity is provided in this transfer part, and the preform preformed on the preforming cavity is transferred to the main forming unit. This is a molding apparatus for a plastic molded article, which is configured such that a preformed article is main-molded by an upper mold and a lower mold by moving to the position of the tool.

[Action]

Since the preform is preformed into a shape close to the finished product,
When the main molding is performed by the upper and lower molds, the distance that the molten resin flows becomes uniform, and the molding works without distortion.

Also, arrange the preforming unit and the main forming unit in parallel,
A transfer unit is provided between them, and the preformed product is conveyed by this transfer unit, so that the device is very simple.

〔Example〕

A first embodiment method and apparatus of the present invention will be described below with reference to FIGS.

First, in FIG. 1, the guide 1 is provided on the upper surface of the base 1.
0, the lower die 4, the slider cylinder 11, and the pedestal 2 are assembled. The slider cylinder 11 is slidably assembled with a transfer portion 5 having a preformed portion 6 and a molded product receiving portion 7 via a mounting plate 22. Reference numeral 61 is a preforming cavity provided in the transfer unit 5.

On the pedestal 2, a main molding unit B including an upper mold 3, a molding cylinder 12, and an eject portion 13, a nozzle 16 in contact with the upper surface of the transfer portion 5, a heating cylinder 23, a heater 1
5, a preforming unit A including a hopper 19 and the like is assembled.

A stirring bar 17 and a screw 14 which are rotated by a motor 20 are incorporated in the center of the hopper 19. In the transfer portion 5 shown in FIG. 2, the preforming portion 6, the molded product receiving portion 7, and the escape hole 21 of the molding die are arranged with appropriate pitches.

Next, the operation will be described.

The material (pellet) 18 in the hopper 19 is agitated by the agitating rod 17 rotated by the motor 20 and sent into the heating cylinder 23 by the screw 14. Since the heating cylinder 23 is heated to an appropriate temperature by the heater 15, the sent material 18 is plasticized. As shown in FIG. 3, the plasticized resin is preformed through the nozzle 16 to the preforming unit 6 at a low pressure without unevenness.

This preforming also combines accurate metering.

At the same time, the ejecting section 13 is moved up and down to eject the molded article 9 that has completed the previous cycle molding into the molded article receiving section 7. When both operations are completed, the transfer cylinder portion 5 slides by the slider cylinder 11 as shown in FIG. 4, and the preforming portion 6 moves to the center of the upper die 3 and the lower die 4 which are molding dies. The molded product receiving portion 7 is transferred to a molded product passing portion (not shown) on the guide 10 outside the gantry 2.

Here, the blank 8 in the preforming portion 6 is forcibly supplied into the cavity of the lower die 4 by operating the eject portion 13 after slightly lowering the upper die 3. At the same time, the molded portion 9 of the molded product passing portion is taken out and carried out to the next step.

Next, as shown in FIG. 5, the transfer part 5 slides and retracts by the slider cylinder 11 until the relief hole 21 of the mold is aligned with the mold position. And the forming cylinder 12
By the mold clamping lowering operation, the blank 8 previously supplied into the lower mold 4 is pressed and molded.

After the molding and cooling time has elapsed, the upper die 3 is lifted by the rising of the molding cylinder 12. At that time, the molded product attaches to the upper mold 3 and rises. This state is shown in FIG.

After opening the mold, the transfer unit 5 moves back to the origin position (right end in FIG. 1) and shifts to the next cycle. When the transfer unit 5 is located at a position other than the origin, the transfer unit 5
The upper surface of the nozzle is always in contact with the tip of the nozzle 16, and the nozzle 1
It is designed to prevent the plasticized resin from leaking from the tip of 6. Upper mold 3, lower mold 4, transfer part 5
In some cases, a cooling or heating flow path may be provided above the preforming section 6 and the heating cylinder 23.

Fig. 6 shows that the plasticized material does not deviate from the shape of the molded product. It shows a process in which a blank preliminarily molded, which is made to flow with directivity, is reheated to an appropriate temperature and supplied into a mold, and is press-molded to finish-mold to ensure accuracy.

That is, FIG. 6 (a) shows a preformed product, which is then reheated in (b) and then main molded in upper and lower molds in (c). Also in this case, the flow of the molten resin can be made uniform, so that a molded product having no distortion can be obtained.

FIG. 7 shows that an assembly member 24 is used in place of the lower mold 4, a plasticized resin is supplied into the member 24, and pressure molding is performed by the upper mold 3 to assemble the molded product 9 to the assembly member 24. The state of performing will be described.

FIG. 8 shows the cavity part not involved in the molding of the lower mold 4,
An example in which a supply port 25 for plasticized resin is provided is shown.
First, the plasticized resin is supplied from the supply port 25 into the cavity of the lower mold 4. When the supply is completed, pressure molding is performed by the mold clamping operation of the upper mold 3. At this time, the supply port 24
Is closed at a site that is not involved in the molding of the upper mold 3.

FIG. 9 shows a state in which the heating cylinder 23 or the heater 15 is heated to an appropriate temperature, and a nozzle 16 for obtaining a blank shape similar to the shape of the molded product is incorporated at the tip thereof. From the outlet of the nozzle 16, the plasticized resin is supplied at low pressure into the mold while being preformed into an extremely thin plate. Immediately after that, pressure molding is performed with a mold. Since it has already been formed into a thin plate under low pressure, it can be formed into a thin plate.

According to the present embodiment, (1) preforming is performed at a low pressure without unevenness, so that the strain in the blank is small and high-precision molding is possible.

(2) Since the resin is preformed by approximating the finished product, the flow distance of the resin during pressure molding is short and uniform. Therefore, the processing strain is small.

(3) Since the resin is directly flown by the mold of the mold clamping operation, there is little pressure loss and it is suitable for downsizing of molding machines. In addition, the projected area that can be molded is wide.

(4) Low temperature molding is possible due to the short flow distance.

(5) Preforming of blanks, ejecting molded articles, conveying preformed blanks, conveying molded articles, supplying preformed blanks and taking out molded articles can be performed simultaneously, which is advantageous for automation.

(6) There are no gate marks, which is advantageous in forming a design part.

〔The invention's effect〕

As described above, according to the present invention, firstly, the pellets are plasticized and ejected from the nozzle to be preformed, and the preformed preforms are main-formed by the upper and lower molds to obtain a resin. In obtaining a molded product, the preformed product is preformed at a low pressure into a shape close to the shape of the finished product, and then the upper and lower molds are used to perform high-pressure mold clamping to average the molten resin flow. Since a molding method of a plastic molded article for obtaining a low distortion molded article is obtained, a molten resin flow can be made uniform and a molded article with less distortion can be obtained, and as a device therefor, a hopper and a heating cylinder are provided. And the nozzle are arranged in a straight line to form a preforming unit, and a forming cylinder, an upper die, and a lower die are arranged in parallel with the preforming unit to form a main forming unit, and these preforming unit and main forming unit are formed. How to cross The transfer part is provided with a pre-forming cavity, and the pre-formed product pre-formed on the pre-forming cavity is moved to the main molding unit position to transfer the pre-formed product. Since the upper and lower molds are configured to be main-molded, the device is simple and can be downsized.

In addition, in the above-mentioned one embodiment, the explanation is given as to obtain a cup-shaped molded product, but any shape can be applied.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a molding apparatus according to an embodiment of the present invention,
Figure is a plan view of the transfer section, and Figures 3 to 5 are
Partial cross-sectional side view showing the operating state of the transfer portion, 6th
FIG. 7 is a process drawing of a blank, FIG. 7 is a sectional view in the case of being directly connected to an assembly member, FIG. 8 is a sectional side view of an improved mold, and FIG. 9 is a flat perspective view. A: preforming unit, B: main forming unit, 1 ...
... base, 2 ... mounting stand, 3 ... upper mold, 4 ... lower mold, 5 ...
… Transfer part, 6 …… Preliminary molding part, 7 …… Molded product receiving part, 8 …… Blank, 9 …… Molded product, 10 …… Guide,
11 ... Slider cylinder, 12 ... Molding cylinder, 1
3 ... Eject, 14 ... Screw, 15 ... Heater, 16 ... Nozzle, 17 ... Stirring rod, 18 ... Material,
19: hopper, 20: motor, 21: escape hole, 2
2 ... Mounting plate, 23 ... Heating tube, 24 ... Member, 25 ...
… Supply port, 26 …… Slit part, 61 …… Preforming cavity.

Claims (11)

[Claims] 1. A plastic molded product obtained by plasticizing pellets and discharging from a nozzle to perform pre-molding, and pre-molding the pre-molded pre-molded product with upper and lower molds to obtain a resin molded product. Is preformed at a low pressure to a shape close to that of the finished product, and then the upper and lower molds are used to clamp the high pressure to average the flow of the molten resin and obtain a molded product with low distortion. Method of molding things. 2. A preforming unit is formed by arranging a hopper, a heating cylinder, and a nozzle on a straight line, and a forming cylinder and upper and lower molds are arranged in parallel with the preforming unit to form a main forming unit. A transfer part that moves in the intersecting direction with respect to these preforming unit and main forming unit is provided, a preforming cavity is provided in this transfer part, and a preformed product preformed in the preforming cavity is transferred to the transfer part. Molding device for plastic moldings that is configured to perform main molding of the preform by the upper and lower molds by moving to the main molding unit position. 3. The plastic molded article according to claim 2, wherein the preforming cavity is a hole that opens up and down, and the lower surface of this hole is closed by another component of the molding apparatus. Molding equipment. 4. A molding apparatus for a plastic molded article according to claim 2, wherein a molded article receiving section is provided at a front end of the transfer section. 5. The structure according to claim 2, wherein an eject portion is provided in the main forming unit, a molded product after completion of molding is fixed to an upper mold, and a mechanism for ejecting the molded product is provided in the molded product receiving portion. Molding device for plastic molded articles. 6. The method for molding a plastic molded article according to claim 1, wherein the molded article is preformed into a shape close to a finished product, and the preformed preform is heated again to be finally formed. 7. The plastic molded product according to claim 1, wherein the preformed product is directly put into the assembly member, and the assembly member and the molded product are joined by pressurizing and molding. Molding method. 8. When a plastic molded product is obtained by a combination of an upper mold and a lower mold, it is molded at the bottom of the cavity of the lower mold, and a lateral injection nozzle is provided near the opening of the lower mold. Mold for molding. 9. A molding apparatus for a plastic molded article according to claim 2, wherein the transfer section is provided with an escape hole for allowing the insertion of the upper mold. 10. A molding apparatus for a plastic molded article according to claim 2, wherein the transfer portion is slidably supported on the upper surface of the slider cylinder. 11. The transfer part according to claim 2, wherein the transfer part has a position where the nozzle of the preforming unit is aligned with the preforming cavity, a position where the preforming cavity is aligned with the main forming unit, and an escape hole. An apparatus for molding a plastic molded article, characterized in that the molding apparatus is configured to move so as to be sequentially positioned and stopped at three positions corresponding to a mold.