WO1981002995A1 - Injection molding method and machine therefor - Google Patents

Abstract

A molding cavity (2) formed by molding dies (1, 1') is communicated with a resin passage (4) through a press-fitted land (5) having a relatively large diameter and a plunger (6) is inserted telescopically into the land to reciprocate between the surface of the cavity and the position opened with a land gate (7). When resin is molded, the plunger is raised to open the land gate thereby reducing its pressure loss. After molding the resin, the plunger is lowered to close the land gate, and moved at its end to reach the surface of the cavity. Accordingly, it can urge the resin retained in the land to thereby pressurize the resin in the cavity so as to compensate for the shrinkage of the resin and to form a smooth finishing surface which leaves no molding mark on a molded product.

Description

 Technical Field Injection molding method and its apparatus

 The present invention relates to an injection molding method and apparatus for performing high-pressure molding of a synthetic resin product such as a thermoplastic resin or a thermosetting resin.

 s technology

 In recent years, the precision molding of injection molded products and the production of t-class products are sudden.] With this, high-pressure injection molding is used to sufficiently fill the material (resin) in every corner of the mold (capital). The conventional injection molding apparatus has a tendency to carry out the injection, but the injection material (resin) from the injection hole is injected through the resin passage (runner) into the capillaries. Since the resin is injected from the gate into the capital, the resin is squeezed extremely at the injection port and the gate, so that the pressure loss is large and the pressure transmission inside the caster is also high. Even if the size of the injection machine is increased, there is a limit to increasing the internal pressure of the machine even if the size of the injection machine is increased.] In addition, in order to compensate for the amount of shrinkage of the resin during solidification, a pressure must be applied after injection into the resin passage. ), The control of the injection machine is duplicated, and the injection molding cycle time is shortened. This was also difficult. In addition, it is unavoidable that the injection marks remain on the molded article, but the appearance of the molded article is also bad, such as the possibility that a fluoromark may be generated near the injection gate.

Ο? Ι won.

 Disclosure of the invention

 The present invention enables high-pressure molding of a synthetic resin such as a thermoplastic resin or a thermosetting resin without using a large-sized injection machine, and leaves an injection gate mark on an injection-molded product. The purpose of the present invention is to prevent the occurrence of marks and to prevent sink marks or deformation due to shrinkage or the like of a molding material.

 Another object of the present invention is to provide an injection molding method and apparatus which can control an injection machine more easily than conventional injection molding and can shorten the injection molding cycle. It is.

 According to the invention, a predetermined amount of resin is injected from a resin passage through a press-fitting land into a capty formed by clamping a mold, and then fitted into the press-fitting land: 7 ° Langer] 3 After closing the press-fit land gate and interrupting the connection between the press-fit land and the resin passage, it is determined from the pressure inside the cavity and the amount of shrinkage when the resin solidifies. The present invention provides an injection molding method characterized by press-fitting the residual resin in a press-fitting land into a capital.

 Also, according to the invention, according to the mold, the captive formed and the resin passage are displaced through the press-fitting land, and the captive surface is reduced within the press-fitting land. Both of them reciprocate between a position where the press-fit land gate is opened and an injection molding apparatus characterized by inserting a 7 ° runner.

 REAl

A, \ V:? 0 Brief description of drawings

 FIG. 1 is a front sectional view of a conventional injection mold, FIG. 2 is a perspective view of a conventional injection molded product, FIG. 5 is a front sectional view of one embodiment of the injection mold of the present invention, and FIG. 4a, 4b and 4c are enlarged views of the press-fit land in Fig. 5, which show the state at the time of injection, injection completion, and molding completion, respectively.

FIG. 3o5 is a front sectional view of another embodiment of the injection molding die of the present invention, FIG. 0a, FIG. 0b and FIG.

The enlarged view of the press-fit land in Fig. 5 shows the state at the time of injection, injection completion, and molding completion, respectively.

 BEST MODE FOR CARRYING OUT THE INVENTION In order to explain this invention in detail, this will be described below with reference to the accompanying drawings.

FIG. 1 shows a conventional injection mold, which is formed by molds 1 and 1 '. A capty 2 is formed, and a runner 1 and a mold 3 connected to molds 1 and 2 are connected to each other. A resin passage (runner) 4 is provided between the resin and the injection machine, which is shown in the figure, and the runner 14 and the cavity 2 pass through an injection gate having a very small pore. They are always in communication. Reference numeral 10 denotes a heater for heating the resin on the inlet side of the injection gate. In this conventional injection molding apparatus, the injection material (resin) from the injection machine is injected into the capite 2 through the runner 4 through the injection gate, which has a very fine hole. Since the resin is injected into the injection gate, the resin is extremely squeezed at the injection gate. Injection due to large loss of staff and possessing good pressure transmission inside the capillaries There is a limit to increasing the internal pressure of the capity even if the machine is enlarged.] And it is necessary to keep the pressure after injection into the resin passage to compensate for the shrinkage of the resin when it solidifies. Along with the complicated control of the injection machine, it has been difficult to shorten the injection molding cycle. Also, for molded products,

2 It is unavoidable that the injection gate marks remain as shown in the figure, and that there is a possibility that a mouth mark will occur near the injection gate.

:: The appearance of the molded article was poor, such as the presence of cracks. FIG. 3 shows an embodiment of the present invention, wherein reference numerals 1 and 1 'are dies, and a capty 2 is formed by the dies. Reference numeral 3 denotes a runner die connected to the dies 1 and 1 'described above, and a resin passage (run) 4 which is not shown in the drawing and which communicates with the injection machine is provided. Reference numeral 5 denotes a press-fitting land—an end of which is open to the cavity surface, and the press-fitting land 5 slides up to the cavity surface. Runger 6 is inserted. Also, on the side of the press-fitting land 5, the gate 7 of the resin passage 4 is open within the moving range of the 7 ° runner 6] 9, and the gate 7 is a flanger. It is opened and closed by the movement of 6. That is, h. 9) Resin passage 4 and E inlet land 5 are disconnected or blocked. 8, 8 'are hydraulic chambers of the plunger 6, 9, 9' are liquid passages, and 10 is a heater o

 In the embodiment shown in FIG. 3, first, the molds 1 and 1 'are clamped to form a capty 2, and the plunger 6 inserted into the press-fitting land 5 is shown in FIG. 4a. The upper part of the gate 7, that is, the resin passage 4 and the press-fit land 5 are not connected.

OMPI

WIFO And hold it.

 In this state, an injection machine (not shown) is operated, and the resin is injected (injected) into the capital 2 from the injection machine via the resin passage (runner) 4 and the press-fit land 5. After the injection is completed, as shown in Fig. 4b. Push down on the ranger 6 to the lower part of the gate 7, immediately to the position where the gate 7 will be closed by the force changer 6. At this time, the connection between the injection machine and the capty 2 is blocked, so that the shrinkage due to the pressure in the cap 2 after injection or the solidification of the resin, etc., as in the conventional injection molding equipment, is prevented. It is not necessary to control the injection machine in consideration of it, and the injection machine moves to the next process operation. On the other hand, even after the gate 7 is closed, the resin remains in the press-fitting land 5, and the resin is kept in response to the set holding pressure in the capacity 2 and the shrinkage of the resin in the capacity when the resin is solidified. T Gradually while controlling the movement of the runner 6: ° Extrude the runner 6 to the cavity 2 side, and when the molding is completed, as shown in Fig. 4c, with the capital surface (molded product surface). H. Control so that the end faces of runner 6 match. When the molding is completed, the mold is opened in the same manner as in the conventional method, the molded article is released, the mold is closed again, and the same steps as above are repeated to carry out molding.

 FIG. 5 shows another embodiment of the present invention, wherein 1 is a mold, 3 is a runner mold, and 11 is a protruding pin. Caper 2 is formed by the inner mold 5 and the protruding pin 11. Reference numeral 4 denotes a resin passage (runner) provided in the runner mold 3.

 O PI

V IPO In addition to communicating with a large injection machine shown in FIG. 1 via a filter 11, the other is connected to the cavity 2 via a press-fitting land 5. Reference numeral 6 denotes a flange fitted in the resin passage 4 and the press-fitting land 5. The piston 14 is inserted into the cylinder 13 with a ranger.]), And the oil passages 15 and 16 are inserted into the cylinder 13. The pressure oil supplied and discharged reciprocates between the outer surface of the capty 2 and the resin passage 4. This fu. The outer diameter of the flange 6 is loosely fitted in the resin passage 4 and the outer diameter of the flange 6 is tightly fitted in the press-fit land 5.], and the plunger 6 is a joint between the plastic passage 4 and the press-fit land 5. That is, the press-fit land gate 7 enters and exits.]? The resin passage 4 and the press-fit land 5 are disconnected and blocked. When the bridger 6 moves to the capty surface, it forms a part of the capty 2 together with the runner mold 3. Reference numeral 17 denotes a protruding pin for a resin passage, which is elastically pressed by a panel 19 having a weaker mold clamping force J through a protruding piston 18. 20 is a mold temperature adjusting fluid passage, 21 is a mold temperature adjusting fluid conduit, and 22 is a runner mold temperature adjusting fluid passage.o

 The embodiment shown in FIG. 5 operates similarly to the embodiment shown in FIG. First, the mold 1 and the runner mold 3 are clamped to form a capital 2. At this time, as shown in Fig. 0a. The runner 16 is pulled up into the resin passage 4] 9, and the resin passage 4 and the press-fit land 5 are kept in communication. In this state, make an injection machine not shown.

One CHFI V irO When the resin is moved, the resin is injected (injected) into the capital 2 through the sprue 12, the resin passage (runner 1) 4 and the press-fitting land 5. After a predetermined amount of resin has been injected into cavity 2. Push the runner 1 to the press fit land 5 side. When the plunger 6 reaches the press-fit land gate 7 as shown in FIG. 0b, the press-fit land gate 7 and the plunger 1 6 are closely fitted, and the resin passage 4 and the press-fit The connection with Hand 5 is cut off. For this reason, the connection between the injection machine and the capital 2 is blocked, so that the pressure inside the capital 2 or the solidification of the resin after the injection as in the conventional injection molding equipment It is not necessary to control the injection machine in consideration of shrinkage caused by the injection, and the injection machine moves to the next process operation. On the other hand, even if the plunger 16 is fitted into the press-fit land gate 7 and the communication between the resin passage 4 and the press-fit land 5 is cut off, the resin remains in the press-fit land 5. ] ?, Residual resin: ° According to Ranger 6] 9, To control the amount and time of press-fitting into Capitol 2] 9, Setting in Capitol 2 While maintaining the holding pressure, replenish the amount of shrinkage due to the solidification of the resin in the capty, and when molding is completed, as shown in Fig. Όc, the capty surface (molded product surface) and the plan Controls the movement of Pranja 6 so that the end faces of Jar 6 coincide. When the molding is completed, the mold is opened, the protruding pin 11 protrudes to release the molded product, and the protruding pin 17 for the resin passage is protruded from the panel 1S. The formed resin passage 4 is also formed by the runner mold 3.

When the above process is completed, mold clamping is performed again and The same process is repeated to carry out molding. In the embodiment of FIG. 5, the runner mold 3 is a cold mold, and the resin in the resin passage 4 is taken out (released) for each molding cycle. However, the runner mold is a hot runner mold, and the resin in the resin passage 4 is molded in the next step without rejecting the inside of the resin passage 4 for each molding cycle. It goes without saying that it is possible to make use of it.

 According to the invention, after the injection is completed, the communication between the press-fitting land 5 and the resin passage 4 is cut off by the plunger 6]), and the ° 6) ?? Pressurizes the remaining resin in the press-in land 5 to maintain the pressure during the molding (solidification) in the capital 2 and replenish the shrinkage of the molding material (resin) during solidification. As a result, precise and high-grade molded products can be obtained.

Also, the injection machine does not need to switch to the holding pressure after injection, so that the injection screw or injection plunger can be easily controlled and the injection (injection) amount can be accurately controlled. At the same time, after the injection, it is possible to move to the next process immediately, so that the molding cycle can be shortened. Furthermore, the injection gate directly connected to the capite is large, so that the gate does not remain on the molded product, and the captive is pressurized by the positive landing force. The pressure is transmitted to all or enough inside the capi- ty, and before starting the injection, the 7 ° run, depending on the runner]) The gate connecting the resin passage and the press fit land should be closed. The gate resin depends on the blanger.] Every 9 cycles It is cleaned at the gate part by the previous injection! The injection gate was blocked due to the mixture of the cooled material (cold slug) into the next injection material, etc.), and contact between materials with different temperatures in the early and late injection periods It has the effect of preventing the occurrence of flow marks caused by the above-mentioned factors.

Claims

Range of SB request  1. Clamp the mold (1, 1 ') and inject a predetermined amount of resin from the resin passage (4) through the press-in land (5) into the formed cap (2). After injection, the plunger (6) fitted into the press-fit land (5) is closed.] 5 The press-fit land gate (7) is closed, and the EE-fill land (5) and the resin passage (4) are closed. ), The press-fitting land, which is determined from the pressure applied in the captive (2) and the amount of shrinkage during resin solidification, etc., removes the residual resin in the captive (5). (2) An injection molding method characterized by press-fitting inside.  2. According to the mold (1, 1 ')]) The formed cap (2) and the resin passage (4) are connected through the press-in land (5) and the press-in run. Reciprocating between the cavity surface and at least the position where the press-fit land gate (7) is open: the 7 ° runner (S) is inserted into the door (5). And injection molding equipment. O PI  , \ Vi? 0 η-ώ