JPH0298414A - Molding method and device for plastic molding - Google Patents

Abstract

PURPOSE:To obtain a molded material of low distortion by contriving averaging of a molten resin flow, by a method wherein a preform is preformed into a shape resembling to that of finished goods at low pressure and high-pressure mold clamping is performed by making use of a top and bottom forces. CONSTITUTION:A material (pellet) 18 within a hopper 19 is agitated by an agitating bar 17 turning by a motor 20 and sent into a heating cylinder 23 with a screw 14. Since the heating cylinder 23 is heated to an appropriate temperature, the material 18 which has been sent away is plasticized. Plasticized resin is sent to a premolding part 6 through a nozzle 16 and preformed at low pressure without having lean. A transfer part 5 is slid and the preforming part 6 is transferred to the center of a top and bottom forces 3, 4 of a molding mold. A blank which has been supplied within the bottom force 4 a little while ago is pressurized and molded by a clamping and lowering actions of a molding cylinder 12. Since a preform is premolded into a shape resembling to finished goods like this, at the time when main molding with the top and bottom forces 3, 4 is performed, flowing distance of molten resin becomes uniform and acts upon the preform so that the same becomes a shape free from a distortion.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to plastic molding having a preforming process and a main molding process, and particularly a molding method and molding suitable for precision molding and supply assembly of small plastic parts. Regarding equipment etc.

[Conventional technology]

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

What is described in Japanese Patent Application Laid-open No. 57-151321 is also
This is similar to this type of molding method.

This publication describes that a preform injection molded around an injection mold core at a preforming station is moved to a final molding station, and the preform molded around this core is compressed from an air valve in the core. A technique of blow molding by blowing out air is described.

[Problem to be solved by the invention]

The above-mentioned conventional techniques lack consideration in that they attempt to mold the resin material without applying more stress than necessary.

For example, in the injection molding method, an injection pressure higher than necessary must be applied to the resin in order to compensate for the injection pressure loss that inevitably occurs due to flowing through a narrow and long flow path. As a result, the internal strain of the resin increases, reducing the precision of the molded product, and at the same time, the specifications and size of the molding machine become unnecessarily large. In addition, since the flow direction is unidirectional, the flow direction is strong.

An object of the present invention is to provide a molding method that does not apply unnecessary stress during the molding process, and a molding apparatus suitable for obtaining molded products, in order to obtain high-precision molded products with small distortion. It is in.

[Means to solve the problem]

The present invention provides a method for making the resin flow uniform and obtaining a low-distortion molded product when molding a plastic molded product.
When a resin molded product is obtained by final molding the preformed product using upper and lower molds, the preform is preformed at low pressure into a shape close to the shape of the finished product, and then the upper and lower molds are molded. It is a method of molding plastic moldings that uses a mold to clamp the mold under high pressure to equalize the flow of molten resin and obtain molded products with low distortion.In addition, as a device for obtaining molded products with low distortion, a hopper is also used. , a heating cylinder, and a nozzle are arranged in a straight line to constitute a preforming unit, a molding cylinder, upper and lower molds are arranged parallel to the preforming unit to constitute a main molding unit, and these preforming units and A transfer part that moves in a direction crossing the main forming unit is provided, a preforming cavity is provided in the transfer part, and the preform formed in the preforming cavity is moved by the transfer part to the position of the main forming unit part. Accordingly, there is provided a molding apparatus for a plastic molded product configured to perform main molding of a preform using an upper mold and a lower mold.

[Effect]

Since the preform is preformed into a shape close to the finished product, when the main molding is performed using the upper and lower molds, the distance through which the molten resin flows is uniform, and the molded product is free from distortion.

In addition, the preforming unit and the main forming unit are arranged in parallel,
A transfer section is provided between these, and the preform is conveyed by this transfer section, resulting in a very simple device.

〔Example〕

Hereinafter, a method and apparatus according to a first embodiment of the present invention will be explained with reference to FIGS. 1 to 5.

First, in FIG. 1, a guide 10 is placed on the top surface of the base 1.
, a lower die 4, a slider cylinder 11, and a pedestal 2 are assembled. A transfer part 5 having a preformed part 6, a molded product, and a receiving part 7 is slidably assembled to the slider cylinder 11 via a mounting plate 22. Reference numeral 61 denotes a preforming cavity provided in the transfer section 5.

The pedestal 2 has an upper mold 3. Forming cylinder 12. A main forming unit B consisting of an eject section 13, a nozzle 16 in contact with the upper surface of the transfer section 5, and a heating cylinder 23. Heater 15
．． A preforming unit A consisting of a hopper 19 and the like is assembled.

At the center of the hopper 19 is a stirring rod 17 , which is rotated by a motor 20 . A screw 14 is incorporated. The transfer section 5 shown in FIG. 2 includes a preforming section 6. Molded product receiving part7. The escape holes 21 of the molding die are arranged at appropriate pitches.

Next, the operation will be explained.

The material (pellets) 18 in the hopper 19 is stirred by a stirring rod 17 rotated by a motor 20, and sent into a heating cylinder 23 by a screw 14. Since the heating cylinder 23 is heated to an appropriate temperature by the heater 15, the material 18 sent therein is plasticized. As shown in FIG. 3, the plasticized resin is preformed into the preforming section 6 through the nozzle 16 under low pressure without shifting.

This preforming also serves as accurate metering.

At the same time, the molded product 9 that has been molded in the previous cycle is ejected into the molded product receiving portion 7 by moving the ejecting section 13 up and down. Once both operations are completed.

As shown in FIG. 4, the transfer part 5 is slid by the slider cylinder 11, the preforming part 6 is moved to the center of the upper mold 3 and the lower mold 4, which are the molding molds, and the molded product receiving part 7 is moved to the pedestal 2. The molded product is transferred to a molded product transfer section (not shown) on the outer guide 10 of the molded product.

Here, the blank 8 in the preforming part 6 is forcibly fed into the cavity of the lower mold 4 by operating the eject part 13 after lowering the upper mold 3 slightly. At the same time, the molded product 9 in the molded product transfer section is taken out and carried out to the next process.

Next, as shown in FIG. 5, the transfer part 5 is slid and retreated by the slider cylinder 11 until the escape hole 21 of the mold is aligned with the mold position. Then, by the mold clamping and lowering operation of the molding cylinder 12, the blank 8, which was previously fed into the lower mold 4, is pressurized and molded.

After the molding and cooling time has elapsed, the molding cylinder 12 rises and the upper die 3 rises. 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 section 5 retreats to the original position (right end in FIG. 1) and shifts to the next cycle.

When the transfer section 5 is at a position other than the origin, the upper surface of the transfer section 5 and the tip of the nozzle 16 are always in contact to prevent the plasticized resin from leaking from the tip of the nozzle 16. There is.

Upper mold 3. Lower mold 4. A cooling or heating flow path may be provided above the preforming section 6 of the transfer section 5 and the heating cylinder 23.

Figure 6 shows that the plasticized material is made to flow in a directional manner without shifting relative to the shape of the molded product, and the preformed blank is reheated to an appropriate temperature, fed into the mold, and pressurized. This is an illustration of the process of final molding and ensuring precision through molding.

That is, FIG. 6(a) shows a preformed product, then (b) shows reheating, and FIG. 6(c) shows that main molding is performed using upper and lower molds. In this case as well, since the flow of the molten resin can be made uniform, a molded product without distortion can be obtained.

In FIG. 7, an assembly member 24 is used instead of the lower mold 4, plasticized resin is supplied into this member 24, and the molded product 9 is assembled to the assembly member 24 by pressure molding with the upper mold 3. Explain the conditions.

FIG. 8 shows that in the cavity part of the lower mold 4 that is not involved in molding,
An example is shown in which a supply port 25 for plasticized resin is provided.

First, plasticized resin is supplied into the cavity of the lower mold 4 from the supply port 25 . When the supply is completed, the pieces of the upper mold 3 are clamped to perform pressure molding. At this time, supply port 24
is closed at a portion of the upper mold 3 that is not involved in molding the piece.

FIG. 9 shows a state in which the heating cylinder 23 or the heater 15 is used to heat the cylinder to an appropriate temperature, and a nozzle 16 is installed at the tip of the cylinder to obtain a blank shape that approximates the shape of the molded product. From the outlet of this nozzle 16, the plasticized resin is supplied into the mold while being preformed into an extremely thin plate shape under low pressure.

Immediately thereafter, it is press-molded using a mold. Since it has already been formed into a thin sheet under low pressure, it can be further formed into a thin sheet.

According to this example, (1) Since preforming was performed at low pressure without any deviation, distortion within the blank was small and high precision molding was possible.

(2) Since the preform is made to approximate the finished product, the flow distance of the resin during pressure molding is short and uniform.

Therefore, processing distortion is small.

(3) Since the resin is directly flowed in the mold during the mold clamping operation, there is little pressure loss, making it suitable for downsizing the molding machine. Moreover, the moldable projected area is wide.

(4) Low-temperature molding is possible because the flow distance is short.

(5) Preforming the blank, ejecting the molded product, transporting the preformed blank, transporting the molded product, supplying the preformed blank, and taking out the molded product can be performed simultaneously, which is advantageous for automation.

(6) There are no gate marks, which is advantageous for molding designed parts.

〔Effect of the invention〕

As explained above, according to the present invention, firstly, pellets are plasticized and preformed by being discharged from a nozzle, and the preformed product is actually molded using upper and lower molds to make a resin. In those that obtain molded products.

The preform is preformed at low pressure into a shape close to that of the finished product, and then the upper and lower molds are clamped under high pressure to equalize the flow of the molten resin and create a molded product with low distortion. Since the method for molding the plastic molded product to be obtained is made uniform, the flow of the molten resin is made uniform, making it possible to obtain a molded product with less distortion.

In addition, as a device for that purpose, a hopper, a heating cylinder, and a nozzle are arranged in a straight line to constitute a preforming unit, and a molding cylinder, an upper mold, and a lower mold are arranged parallel to the preforming unit to form a main molding part. A transfer section is provided which moves in a direction perpendicular to the preforming unit and the main forming unit, a preforming cavity is provided in the transfer section, and the preform is transferred to the preforming cavity through the transfer section. Since the preform is moved to the main molding unit position and then main molded using the upper and lower molds, the apparatus is simple and can be made smaller.

In the above embodiment, a cup-shaped molded product is obtained, but any shape can be applied.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a molding apparatus according to an embodiment of the present invention, and FIG.
The figure is a plan view of the transfer section, and Figures 3 to 5 are
Part 6 partially cross-sectional side view showing the operating state of the transfer section
The drawings are a process diagram of a blank, FIG. 7 is a cross-sectional view when directly connected to an assembly member, FIG. 8 is a cross-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... Frame, 3... Upper mold, 4...
- Lower mold, 5... Transfer part, 6... Preforming part, 7... Molded product receiving part, 8... Blank, 9... Molded product, 10... Guide, 11... -Slider cylinder, 12...molding cylinder. 13...Eject, 14...Screw, 15...
・Heater, 16... Nozzle, 17... Stirring bar, 18.
...Material, 19...Hopper, 20...Motor, 21
... escape hole, 22 ... mounting plate, 23 ... heating tube,
24... Member, 25... Supply port, 26... Slit portion, 61... Preforming cavity. (αnrai 6 koku 杢′V mouth 1st daily rate 2 figure

Claims (1)

[Scope of Claims] 1. A resin molded product is obtained by plasticizing pellets and preforming them by discharging them from a nozzle, and then main-molding the preformed product using upper and lower molds, The preform is preformed at low pressure into a shape close to that of the finished product, and then the upper and lower molds are clamped under high pressure to equalize the flow of the molten resin and create a molded product with low distortion. A method for molding a plastic molded product. 2. A preforming unit is constructed by arranging a hopper, a heating cylinder, and a nozzle in a straight line, and a main molding unit is constructed by placing a molding cylinder, upper and lower molds parallel to the preforming unit, and these A transfer part that moves in a direction crossing the molding unit and the main molding unit is provided, a preforming cavity is provided in the transfer part, and the preformed product is transferred to the main molding unit position by the transfer part. A plastic molding device configured to move a preform into an upper mold and a lower mold for final molding. 3. The apparatus for molding a plastic molded product according to claim 2, wherein the preforming cavity is a hole that opens upward and downward, and the lower surface of the hole is closed with another component of the forming apparatus. 4. The apparatus for molding a plastic molded article according to claim 2, further comprising a molded article receiving section provided at the tip of the transfer section. 5. The product according to claim 2, characterized in that the main forming unit is provided with an eject part, and a mechanism is provided for fixing the molded product after molding is completed to the upper mold and ejecting it to the molded product receiving part. Molding equipment for plastic molded products. 6. The method for molding a plastic molded article according to claim 1, characterized in that the preform is preformed into a shape close to that of a finished product, and the preform is heated again to perform main molding. 7. A method for molding a plastic molded product according to claim 1, characterized in that the preform is placed directly into the assembly member, and the assembly member and the molded product are joined by applying pressure and molding. . 8. For molding, when a plastic molded product is obtained by combining an upper mold and a lower mold, the molding is performed at the bottom of the cavity of the lower mold, and an injection nozzle from the side is provided near the opening of the lower mold. Mold. 9. The apparatus for molding a plastic molded product according to claim 2, wherein the transfer part is provided with an escape hole for allowing insertion of the upper mold. 10. The apparatus for molding a plastic molded product according to claim 2, wherein the transfer part is supported so as to be guided and slid on the upper surface of the slider cylinder. 11. In the product according to claim 2, the transfer part is arranged so that the nozzle of the preforming unit part matches the preform cavity, the preform cavity matches the main molding unit, and the relief hole matches the upper die. 1. A molding device for a plastic molded product, characterized in that the device is configured to move so as to sequentially position and stop at three positions.