JPH01160621A - Molding method - Google Patents

Abstract

PURPOSE:To obtain a molded article without any shrink mark, warpage or property dispersion by including each process wherein a melted material is injected into the cavity of die members heated above the softening temperature of an injecting material and the same melted material aforementioned is charged into the cavity through heating the die member above the softening temperature of the material while retaining the solidified material in the cavity. CONSTITUTION:At first, the die members 2, 3 are heated rapidly by means of a high frequency inductance coil 27 and made up to or above the softening temperature of the injecting material 30, and then the melted material 30 is injected into the cavities 12, 13. Following this, the material 30 is cooled and solidified by the high boiling medium to be passed through cooling hole 14, 15. In the next place, the die members 2, 3 are heated above the softening temperature of the material 30, and the solidifying material 33, 34 within each of cavity 12, 13 are melted only in its superficial portions 33a, 34a. Subsequently, the same melted material 37 is injected into the cavity of the contracted portion 35, 36 and melted mixingly with each superficially layered portion 33a, 34a one another, thus, the shrink mark or warpage of the solidifying material up to that time are disappeared.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a molding method.

[Background technology]

FIG. 7 shows one of the injection molding apparatuses mainly used for resin molding, aluminum die-cast molding, etc. The device includes a fixed side profile 1 and a movable profile 2.3, and the movable profile 2.3 includes a receiving plate 5 provided on the front side of a mounting plate 4. A recess 8 into which the tip of a cylinder 7 equipped with a piston 6 is fitted, and an injection port 9 communicating with the recess 8 are provided at the center of the fixed-side mold member 1. Two passages 10 and 11 communicate with the injection port 9. In addition to cavities 12.13 being formed in the mold members 2 and 3 on the movable side, cooling holes 14.15 are also provided. Each cavity 12. of the same profile 2°3.
13 faces an ejector pin 16, 17 arranged on the front side of the mounting plate 4.

By the way, in the conventional molding method, the mold material 2.3 is cooled below the temperature at which the injected material 20 solidifies, and the molten material 20 in the cylinder 7 is poured into the cavity 12.13 by the piston. By injecting and solidifying with 6, 1
A molding cycle was configured. In the cavity 13 for thick-walled molding shown in FIG. 8(a), the material 21 receives heat from the cavity 13 and solidifies from the surface layer 21a to the center portion 21b. During the solidification process, the surface layer portion 21a that solidifies first is pulled by the central portion 21b that solidifies and contracts later.
As shown in the figure, sink marks 22 occur, but in the past, the molded product was taken out as is. Figure 9 (
In the uneven thickness molding cavity 12 shown in a), the material 23 is solidified into a thick portion 23a and a thin portion 23b. The thin portion 23b solidifies quickly, while the thick portion 2
3a, solidification is delayed due to the central portion 23C, so the thin portion 23b that solidifies quickly is the thick portion 23 that solidifies slowly.
As shown in FIG. 9(b), the thin portion 23b is warped 23d by being pulled by the force 23a, but in the past, it was taken out as a molded product as it is. In this way, molded products with curls or warps are not desirable as products.

In addition, in the conventional molding method, the mold material 2.3 was cooled in advance and the material was injected later.
As shown in the figure, the material 24 injected into the cavity 12 from the gate 18 begins to solidify near the gate 18, and solidification is delayed in the final filling part 24a away from the gate 18, filling the space between the two. A pressure difference occurs, and as a result, the mechanical and electrical properties of the obtained molded products vary, which is a cause of quality deterioration.

[Purpose of the invention]

In view of the above circumstances, it is an object of the present invention to provide a molding method capable of obtaining a molded product of good quality without curling, warping, or variation in properties.

[Disclosure of the invention]

To achieve the above object, the present invention includes at least a step of injecting a molten material into a cavity of a mold material heated above the softening temperature of the material to be injected, and cooling the mold material to solidify the injected material. a step of heating the mold material above the softening temperature of the material while retaining the solidified material in the cavity and filling the cavity with the same molten material, and cooling the mold material after the filling. The gist is a molding method that includes a step of cooling the material in the mold material during one molding cycle.

Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof.

1 to 6 show an embodiment of the molding method according to the present invention. As seen in these figures, the molding apparatus for carrying out this molding method is substantially the same as that described in the conventional art, and thus similar components are designated by the same reference numerals and will not be described. In addition, the cooling holes 14.15 provided in the movable side mold material 2゜3,
A high-boiling point medium is flowed, and high-frequency induction coils 27 are wound around the outer peripheries of the same mold members 2 and 3, respectively, so that only the mold body can be rapidly heated and cooled to shorten cycle time. There is.

By the way, in the molding method according to the present invention, first, the mold material 2.3 is rapidly heated by the high-frequency induction coil 27.27 to reach a temperature equal to or higher than the temperature at which the material 30 to be injected is softened. This corresponds to section A in FIG. 6, in which the shapes 2 and 3 are heated from t,'c (solidification temperature of the material) to t2°C (softening or melting temperature of the material).

The material 30 molten in the cylinder 7 is then forced out by the piston 6 and passed through the inlet 9 to the two gates 18
．． 19 into the cavities 12 and 13. Since the material 30 is heated to a temperature higher than the softening temperature of the material 30, the material 30 does not start solidifying immediately after entering the cavities 12 and 13 from around each gate 18 and 19. A uniform pressurized state is obtained as a whole while maintaining a molten state within 13. This allows material 3
The packing density in the cavities 12 and 13 of No. 0 is made uniform at all locations, and by cooling in the next step, properties with uniform mechanical and electrical properties can be obtained. Note that the manner in which the temperature of the mold material is maintained at a constant t2° C. during the injection is shown in section B in FIG. 6.

The cooling process corresponds to section C in FIG. In this section, the shapes 2 and 3 are cooled from t2°C to t1°C. This is due to the high boiling medium being passed through the cooling holes 14.15. When the cooling process ends, the D section in FIG. 6, that is, the solidification section begins. During this solidification period, the temperature of the mold material is maintained at 11°C. FIG. 2 shows an outline of the solidification, and FIGS. 3(a) and (bl) show the cavity 12 after solidification.
The situation inside 13 is magnified and shown as hail. Figure 3 (a
) In the cavity 13 for thick walls, the solidified material 31 has sink marks 31a, and even in the cavity 12 for uneven thicknesses, shown in FIG.
2a occurs. This is the same as before. However, in the molding method according to the present invention, instead of taking out the molded product as it is, by combining the next molding cycle as the latter cycle, it is possible to obtain a good product without the aforementioned sink marks or warpage.

That is, the latter half of the cycle is a combination of the steps of heating the mold material E, surface melting and injection of the molding material F, cooling G, and solidifying H as shown in FIG. The mold material heating E
In the section, the shapes 2 and 3 are heated from 11°C to t! heated to ℃. In the next section F, the solidified material 33.34 in each cavity 12.13 is kept at t2.degree. C., and only the surface layer portions 33a, 34a thereof are melted. Material 33.34
Since only the surface layer portions 33a and 34a are melted, a volume shrinkage of 35.36 remains between each cavity 12.13 and each material 33, 34, and these shrinkage amounts of 35.
The same molten material 37 is injected from the cylinder 7 into the gap 36, so that the inside of the cavity 12, 13 is filled. With this supplementation, the molten material 37 is
A and 34a are melted and mixed with each other, and the shrinkage and warpage that the solidified material had until then disappears. When the above-mentioned replenishment is completed, the process moves to the next cooling process G, and in the same process G,
The mold materials 2 and 3 are cooled from t2°C to 11°C, and then proceed to a solidification step H in which the temperature is maintained at 11°C. This solidification process H
In this case, as shown in Figure 5 (a) and (bl), the central part, where the solidification rate is slow, has already finished solidifying and only the surface part has melted, making the solidification rate uniform, so that no whiskers or warping occur. As a result, there is no curling or warping, and
As mentioned above, a molded product of good quality without variation in properties can be obtained. Note that the surface melting and injection step F is shorter than the step B in terms of time. This is because in step F, it is necessary to melt only the surface layer of the material, not the entire material.

〔Effect of the invention〕

Since the molding method according to the present invention is constructed as described above, it is possible to obtain a molded product of good quality without sink marks, warping, or variations in properties.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a molding device for carrying out the molding method according to the present invention during a material injection step, Fig. 2 is a cross-sectional view of the same device during a solidification step, and Fig. 3 is a view of the interior of the cavity. Fig. 4(a) is a cross-sectional view showing the solidified state of the thick-walled material, and Fig. 4(b) is a cross-sectional view showing the solidified state of the uneven-walled material. shows the relationship between the material whose surface layer has solidified in the cavity and the material that has been supplemented, and the same figure (
a) is a cross-sectional view of the thick-walled material, BL is a cross-sectional view of the material with uneven thickness, Figure 5 is a cross-sectional view of the final solidified material, Figure (b) is a cross-sectional view of the material with uneven thickness, Figure 6 is a graph showing a schematic diagram of time and temperature changes in each process, and Figure 7 is a cross-sectional view of the uneven thickness material. Cross-sectional view of the molding device, No. 8
The figure shows the formation of whiskers on a thick material. Figure (a) is a cross-sectional view showing how the central part of the material pulls on its outer periphery during solidification, and figure (b) shows the appearance of sink marks. FIG. 9 is a cross-sectional view showing how the material with uneven thickness warps, and FIG. Fig. 10(b) is a cross-sectional view showing how the warpage has occurred, and Fig. 10 is a cross-sectional view showing how the material solidifies near the gate of the cavity and remains molten at the final filling portion.1. 2.3...Form material 12.13...Cavity agent Patent attorney Takehiko Matsumoto Figure 6 Process Figure 7

Claims (2)

[Claims] (1) At least a step of injecting the molten material into the cavity of the mold material heated above the softening temperature of the material to be injected, a step of cooling the mold material to solidify the injected material, and a step of injecting the solidified material into the cavity. A step of heating the mold material while being held in the tee to a temperature higher than the softening temperature of the material and filling the cavity with the same molten material as described above, and cooling the mold material after the filling to cool the material inside the mold material. A molding method that includes a step during one molding cycle. (2) The molding method according to claim 1, wherein the mold material is provided with heating/cooling means near the cavity.