JPH04316826A - Method for preparing blow mold - Google Patents

Abstract

PURPOSE:To obtain a product having beautiful appearance and high dimensional accuracy by simultaneously transferring the shapes of a plurality of the master models arranged to the outer periphery of a cylindrical plate material to simultaneously form a plurality of surface cavities. CONSTITUTION:A superplastic alloy material 9 is pressed to a heat-collapsible master model 8 having a product shape under heating to form a surface cavity layer 11 to which the surface shape of the master model 8 is transferred. A lining layer 12 composed of a backup material is formed to the rear of the surface cavity layer 11 from which the master model 8 is released while it is collapsed. If necessary, a plurality of master models 17, 18 are arranged to the outer periphery of the cylindrical superplastic alloy plate material to be simultaneously transferred to form a plurality of surface cavity layers 20, 21, 22. By this constitution, the cause of a product flaw such as a nest or a pinhole can be removed from a surface and dimensional accuracy is also enhanced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding synthetic resin, and more particularly to a method for making a mold for blow molding to form a hollow plastic container.

0002

[Prior Art] Blow molding is a molding method used to form hollow containers such as bottles from thermoplastic synthetic resin.Blow molding is a molding method used to form hollow containers such as bottles from thermoplastic synthetic resin. In this method, the parison is first molded into a tube-shaped parison, and then, after the mold is closed, air is blown into the parison to inflate it and then the parison is pressed into a cavity.

[0003]Currently, the extrusion blow molding method in which parisons are formed by extrusion molding is most widely used, and the structure of the mold used in this molding is shown in a plan view in FIG. 5 and in a partial sectional view in FIG. It is shown.

This extrusion blow molding mold has a cavity part 1 in the shape of the main body of a bottle, and a pinch-off part 2 under the bottom part of the cavity part 1 for cutting off the parison when the mold is closed. A nozzle attachment hole 3 is carved at the tip of the cavity 1 into which a blow nozzle for blowing air during blow molding is inserted.

[0005] When extrusion blow molding is performed using such a mold, the cut edges of the parison remain as burrs on the bottom of the molded bottle, making the bottle unstable when standing upright. The bottom of the bottle must be recessed, and as is clear from FIG. 6, the bottom of the cavity 1 is undercut.

[0006] In blow molding, the molding pressure is low at 4 to 7 kg per square cm, so the mold clamping pressure can also be low to correspond to this low molding pressure, and the pressure resistance of the mold is not required as much, but the molding cycle is In order to effectively control the temperature, it is preferable that the mold has excellent thermal conductivity, so metal materials with excellent machinability such as mild steel, aluminum alloy, zinc alloy, etc. are used for milling or electrical discharge machining. Machined molds such as these are used.

As mentioned above, in blow molding, an undercut is always provided at the bottom, and the designs of recent products have become highly individualized and diversified, resulting in shapes with many free curved surfaces. During production, extremely complicated processing is required to form the cavity.

[0008] For this reason, if a mold is created by machining, the machining itself is difficult, and final polishing must be done carefully by hand, making it very time consuming and costly to make the mold. Recently, it has become popular to create molds by precision casting using aluminum alloys and zinc alloys.

[0009] Precision casting molds are made by transferring a master model of the product shape made from materials with good workability such as wood or ABS resin onto silicone rubber, and then using a plaster mold with a beautiful surface that is transferred using plaster slurry. made by casting.

For this reason, precision casting has a very clean surface and almost no need for final polishing, and it is also possible to easily form molds with complex shapes, such as undercuts and free-form surfaces, which are difficult with machining, at a low cost. I was able to make it in a short period of time.

[0011]

[Problems to be Solved by the Invention] However, in precision casting molds, casting defects such as pinholes and shrinkage cavities, which are defects of casting molds, easily appear on the surface, and these become product defects as they are, so the appearance quality is affected. It was not suitable as a mold for making strict toiletries or food containers, and it also had the disadvantage that it was difficult to accurately gauge the amount of solidification shrinkage during casting, making it difficult to create molds with high dimensional accuracy. . It is an object of the present invention to overcome these drawbacks of the prior art and to provide a mold with a complex shape of high quality easily and at low cost.

0012

[Means for Solving the Problems] That is, the present invention involves placing a master model in the shape of a product that is resistant to heat collapse and a thin superplastic alloy plate facing each other, and heating the superplastic alloy plate to a superplastic deformation temperature while applying air pressure. After the product shape is transferred by pressing onto the surface of the master model, the master model is collapsed to form a surface cavity layer, and a backing layer made of a back-up material is formed on the back surface of this surface cavity layer, preferably a superplastic alloy plate material. This is a method for creating a blow molding mold which is cylindrical and is characterized by simultaneously transferring the shapes of a plurality of master models placed on the outer periphery of this cylindrical plate material to form a plurality of surface cavities at the same time.

[0013]

[Operation of the Invention] The present invention is constructed as described above, and since a superplastic alloy plate undergoes extremely large plastic deformation even when pressed at a relatively low pressure at the superplastic deformation temperature, the surface shape of the master model is It is possible to easily form a high-quality surface cavity layer with very faithful transfer and no defects or dimensional shrinkage, and since a backing layer is formed on the back side of this surface cavity layer, it can withstand blow molding sufficiently. A mold with appropriate strength is formed.

[0014] Furthermore, since the master model is made of a collapsible material and the master model is easily broken when the master model and the surface cavity layer are separated after forming the surface cavity layer, the master model is not undercut. Even in the case of a complex shape, the mold can be easily released without deforming the surface cavity layer at all.

Furthermore, if the superplastic alloy plate material is made into a cylinder and a plurality of master models are arranged around the outer periphery of this cylindrical plate material to simultaneously create a plurality of surface cavity layers, mold making can be carried out very efficiently.

[0016]

Embodiments Next, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a longitudinal cross-sectional view showing the state in which a superplastic alloy plate material is pressed against a master model to form a surface cavity layer, and shows a steel pressure-resistant container 4 with an open top and an air vent hole 5 in the bottom. A master model 8 having a shape obtained by dividing a product model along a cut-off plane is placed inside.

This master model 8 has heat resistance that can withstand temperatures of about 500°C, which is the deformation temperature of superplastic alloys, and collapsibility that allows it to be easily broken when released from the mold. It is preferable that the superplastic alloy sheet has appropriate air permeability in order to discharge air interposed between the superplastic alloy sheet and the master model and improve the adhesion between the two when pressed onto the model.

[0019] Gypsum is the most suitable material that satisfies these conditions, and wood and ABS, which are materials with excellent workability,
First, a product model was created using resin, etc., and then a master model made of plaster was created by molding the product model using silicone rubber, injecting gypsum slurry into the rubber mold, and transferring the product shape.

[0020] A 1 mm thick aluminum alloy superplastic alloy (A7475) sheet 9 is placed on the upper opening of the pressure vessel 4. Under certain conditions, this superplastic alloy deforms under low stress and undergoes extremely large deformation. Ductility (500-1
22Al is a metal material that exhibits a maximum elongation of 500%.
-Zinc alloy system such as Zn, 10.7Zn-0.9Mg
- Aluminum alloy system such as 0.4Zr-Al, 33
．． Magnesium alloys such as 6Al-Mg, 6Al-
There are various materials such as titanium alloys such as 4V-Ti.

The pressure container 4 has a lid 6 with a pressurized air inlet 7 provided from above the superplastic alloy sheet 9 on which the upper opening is placed.
The superplastic alloy sheet 9 is placed in a heating furnace and heated to 505 to 515°C, which is the temperature at which the largest plastic deformation occurs.

Thereafter, compressed air is introduced from the pressurized air inlet 7 provided in the lid 6 of the pressure container 4 to press the superplastic alloy sheet 9 toward the master model 8, but the pressing conditions at this time are such that the In order to prevent the superplastic alloy sheet 9 from being rapidly deformed and damaged by such pressure, first press it at a low pressure of about 2 kg per square cm for about 10 minutes, then increase the pressure to about 8 to 10 kg per square cm. Appropriate conditions include pressing at a pressure of about 1 minute.

When this superplastic alloy sheet 9 is pressed against the master model 8, since the master model 8 has air permeability, the air between the superplastic alloy sheet 9 and the master model 8 is pushed and the master model 8 Since the superplastic alloy sheet 9 is discharged from the air vent hole 5 provided at the bottom of the pressure vessel 4 through the air, the superplastic alloy sheet 9 is deformed by closely adhering to the master model 8, and the surface shape of the master model 8 is faithfully formed into the superplastic alloy sheet 9. transcribed.

Of course, if the heating conditions and pressing conditions are well controlled when transferring the surface shape of the master model 8 to the superplastic alloy sheet 9, the superplastic alloy sheet 9 will not melt or have holes. , transfer can be performed without worrying about product defects as in the case of precision casting molds.

After the above-described transfer operation is completed, the superplastic alloy sheet 9 is cooled to room temperature, and then placed in the pressure container 4.
The lid 6 is removed and the superplastic alloy sheet 9 is released from the master model 8.

[0026] In this mold release work, as the master model 8 is made of collapsible plaster as mentioned above, the work can be carried out while breaking it appropriately, so it can be used for complex shapes with undercuts. Even if the shape of the master model 8 is transferred, the work can be easily carried out without deforming the superplastic alloy sheet 9 onto which the shape of the master model 8 has been transferred.

Next, as shown in FIG. 3, the surface cavity layer 11 obtained by transferring the master model 8 to the superplastic alloy sheet 9 as described above is obtained with high dimensional accuracy since there is no solidification shrinkage. A backing layer 12 made of a heat-resistant material is formed on the back surface for reinforcement.

It is desired that the backing layer 12 not only have appropriate strength but also be lightweight and have good thermal conductivity, so the backing material for forming this layer should be 3 m in diameter.
Pellet-shaped grains of a light alloy such as aluminum or magnesium with a length of about 5 mm and a small amount of a binder such as an epoxy resin are used.

Furthermore, in order to form a good backing layer 12,
It is preferable to fill the back-up material with high density while applying vibration, and to sandblast the back side of the surface cavity layer 11 with coarse glass beads to improve the adhesion between the two. Therefore, the cooling pipe 13 is embedded in a position close to the surface cavity layer 11 where the cooling effect is high.

After forming the backing layer 12 on the back side of the surface cavity layer 11 in this manner, appropriate machining is performed to form guide pin holes for pinch-off portions and mold matching, and for attachment to a molding machine. The mold is completed.

Next, as another example, an example in which a plurality of shapes are simultaneously transferred from a plurality of master models to a superplastic alloy plate material will be explained with reference to FIG.

Reference numeral 14 denotes a pressure-resistant container with air vent holes 15 and 16 on its sides, and two master models 17 and 18 made of plaster are attached to opposite sides of this pressure-resistant container 14, each having a thickness of 1.5 mm. A 22Al-Zn superplastic alloy pipe 19 is inserted from the upper opening and is placed upright in the center with the closed end as the bottom surface.

The pressure vessel 14, which is now in a state where it can be transferred to the superplastic alloy plate material of the master model, is placed in a heating furnace, and the superplastic alloy pipe 19 placed therein is heated to a superplastic deformation temperature of 270~270°C. Heat to 275°C.

Next, as mentioned above, the superplastic alloy pipe 19 is initially coated with a weight of about 2 kg per square cm, and eventually 1 kg per square cm.
Introduce compressed air with a pressure of about 0 kg.

As a result, the superplastic alloy pipe 19 expands and is pressed against the surfaces of the master models 17 and 18, and the surface shapes of these two master models 17 and 18 are simultaneously transferred to the superplastic alloy pipe 19. 1
9 is cooled and then released from the mold, a surface cavity layer 20 having two cavity transfer parts is formed as shown in FIG.
When this cost cavity layer 20 is divided into two at the center as shown by the dotted line, two surface cavity layers 21 and 22 are formed.
can be obtained at the same time.

The surface cavity layers 21 and 22 thus formed are each formed into a mold by forming a backing layer with a backup material as described above and then performing appropriate machining. By forming the cavity layer at the same time, the mating molds to be combined are completed at the same time.

The above describes a method for simultaneously transferring a master model onto two surfaces and forming two surface cavity layers at the same time, but of course, it is possible to create a larger number of surfaces by changing the shape of the tube of the superplastic alloy plate material in various ways. surface cavity layers can be formed at the same time.

[0038]

Effects of the Invention The present invention has the structure and operation as described above, and first, a mold in which the surface shape of a master model is faithfully transferred, no matter how complicated, can be easily provided at low cost and in a short period of time.

[0039] Furthermore, the mold obtained has a very clean surface with no fear of forming cavities or pinholes, so there is no risk of surface defects in the molded product, and there is no solidification shrinkage. Because there is no such thing, the dimensional accuracy is extremely high.

Furthermore, since a plurality of master models can be transferred at the same time and a plurality of molds can be easily formed at the same time, a set of mating molds to be combined can be formed at the same time, and very efficient mold making can be achieved.

[Brief explanation of drawings]

[Figure 1] First embodiment,

[Figure 2] Longitudinal cross-sectional view of the mold,

[Figure 3] Second embodiment,

[Figure 4] Two surface cavity layers transferred simultaneously,

[Figure 5] Plan view of blow molding mold,

[Figure 6]
A partial sectional view of a blow molding mold.

[Explanation of symbols]

8, Master model 9, Superplastic alloy sheet 11,
Surface cavity layer 12, backing layer

Claims (2)

[Claims] Claim 1: A master model in the shape of a product that is heat-resistant to collapse and a thin superplastic alloy plate are placed opposite each other, and the superplastic alloy plate is heated to a superplastic deformation temperature and is pressed against the surface of the master model using air pressure to form the product. A method for making a blow molding mold, which comprises: collapsing the master model to form a surface cavity layer after transferring the master model, and forming a backing layer of a backing material on the back side of the surface cavity layer. 2. A superplastic alloy plate material having a cylindrical shape, and a plurality of surface cavity layers being simultaneously formed by simultaneously transferring the shapes of a plurality of master models arranged around the outer periphery of the cylindrical plate material. 1. The method for creating a blow molding mold according to 1.