JPH081722A - Lim molding method - Google Patents

Abstract

PURPOSE:To improve characteristics and a quality of a molding by increasing productivity by enabling automatic demolding by making the most of a distinctive feature of a liquid silicone rubber, by a method wherein a vacuum device is connected, to a cavity of a product part of an end of a row of a molding direction in a mold and the inside of the cavity is depressurized. CONSTITUTION:In the title method an easily separatable rosarylike molded body is infected of a liquid silicone molding material, by a method wherein a plurality of cavities 15 of product parts are arranged between molds 11, 12 and the cavities 15 are connected with each other into a rosarylike state by providing processed gates 16 between the cavities of the product parts. Thus the molds are made into a structure so that a space X between the cavities 15 of the product parts in the molds 11, 12 is taken as 1mm>=X>=0.02mm and the processed gate 16 connects directly the cavities of the product parts in the space. Then a vacuum device (vacuum line 18) is connected with the cavity 15 of the product part of the end part of a row of a molding direction in the molds 11, 12 and the insides of the arranged cavities 15 of the product part is depressurized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to injection molding (hereinafter, LIM, Liquid Injecti) using a liquid silicone molding material.
on Molding) method.

[0002]

2. Description of the Related Art Conventionally, a general L of liquid silicone rubber has been used.
In the IM molding method, the material injected into the mold from the nozzle of the injection molding machine flows through the sprue to the runner, and fills each product section through the gate for each product section provided on the runner. It was a thing. And since air is accumulated at the resin termination point of each product part and defects such as welds are likely to occur,
On the other side of the gate, a dummy such as a pool of water and slag was installed, and burrs were forced to be generated on the parting surface to prevent defects.

Recently, as a cold runner molding method, a cold runner is directly provided for each product part, and liquid silicone rubber is directly injected into each product part,
Revolutionary methods that save the materials used for sprues, runners, and gates and that can be shipped as products immediately after being taken out are being implemented in Germany, Austria, etc. where strict regulations for industrial waste are strict.

[0004]

In the former LIM conventional method, since the runners are provided for each product part, the space between product parts is empty, and the number of products to be taken per die is limited. In addition, the smaller the product, the more the weight of the runner becomes extremely larger than the weight of the product, which is a very disadvantageous molding for the sprue after curing and the silicone rubber in which the runner cannot be regenerated like thermoplastics. Furthermore, after molding, sprue, removal of runner, gate cut,
I was spending time on post-processing such as dummy cutting and deburring.

In the latter cold runner method, since a cold runner is provided for each product part, the interval between the product parts must be widened by the size of the cold runner, and the number of molds taken per die is also limited. Will end up.

Further, since the cold runner portion is in contact with the product portion which is cooled and directly heated, it is difficult to handle the mold because the mold cannot be left closed or the heater cannot be heated up while keeping the contact. There is. For this reason, it is necessary to have a structure in which the cooling part and the heating part can be divided, and further, it is necessary to provide a shut-off mechanism so that the liquid silicone rubber does not drip from the tip of the cold runner part nozzle. Further, depending on the shape of the product, decompression in the mold is required, the mold becomes more complicated and the mold thickness increases, and a wide daylight is required as an injection molding machine.

Further, there is a considerable difference in temperature between the cooling unit of the cold runner section and the unit of the product section to be heated, which causes a difference in the thermal expansion of the steel materials, making it difficult to match the more pieces are taken, and burr-free forming is required. As a result, high precision is required and the molding equipment becomes quite expensive.

[0008]

In view of the above situation, the LIM molding method of the present invention is a molding method which takes advantage of the good characteristics of flowability, low-pressure molding property and rapid curing property, which are the main characteristics of liquid silicone rubber. As a result of examining the structure of the molding die and the pressure reduction inside the die, it was completed.

That is, according to the LIM molding method of the present invention, a plurality of product part cavities are arranged in a row in a molding die, and a processed gate is provided in a space between the product part cavities to form the product part cavities. A method of injection-molding a bead-shaped molded body, which is connected in a beaded shape and is easily separated by a liquid silicone molding material, comprising: (A) setting a space X between the product-portion cavity and the product-portion cavity in the molding die.
1 mm ≧ X ≧ 0.02 mm, and the structure is such that the gates machined in the gap directly connect the product cavities to the product cavities, and (B) the product cavities at the end of the molding direction in the molding die. Connect a vacuum device to
It is characterized by reducing the pressure inside the arrayed product part cavities.

According to the present invention, when a liquid silicone rubber is injection molded at 130 to 230 ° C., a molded product can be obtained without post-treatment such as deburring and gate cutting.
It aims to realize labor saving, rationalization, low system cost, and mass production of molding.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings with reference to the accompanying drawings.

FIG. 1 (a) is a cross-sectional view of the main part of a mold that has been subjected to the LIM molding method of the present invention, and FIG. 1 (b) is an enlarged view of the portion of the chain line B in FIG. 1 (a). A sectional view is shown. Further, FIG. 2 shows the moving side mold 12 in FIG.
It is the top view seen from the direction.

In this embodiment, using φ5 balls as a product, a large number of die sets having a maximum die set W140 (mm) × H300 (mm) that can be attached to a 24 ton horizontal injection molding machine are used to obtain a large number of φ5 balls. The main part of the cavity has a very simple 2-plate type structure that is divided by the parting line on the fixed side and the moving side, but the present invention is limited by the product, mold structure, etc. shown in this example. It is not something that will be done.

In FIGS. 1 and 2, 11 is a fixed mold, 12 is a movable mold, PL is a parting line for both molds, 13 is a sprue, and 14 is two runners running from the sprue. Reference numeral 15 is a product part cavity corresponding to each product. The plurality of product part cavities are arranged in a row, and the dimension X of the space between the product part cavities arranged as shown in FIG. The product part cavity 1 is contracted by the gates 16 provided at the intervals while contracting.
5 are connected in a beaded shape. A plurality of rows of product part cavities connected in a beaded shape are connected to the runner 14 by a gate having the same size as 16. The product portion cavity at the end opposite to the sprue 13 is connected to the second runner 17 through a gate having the same size as that of 16.
The runner 17 connects each product part cavity row to the vacuum line 18. In addition, 19 is a sprue ejector pin and 20 is a runner ejector pin.
Furthermore, to further reduce material loss, sprue 1
There is also a method of making 3 a cold runner.

In this embodiment, the intervals X between the outer peripheries of the product part cavities arranged in rows are 0.2 mm, 0.1 mm and 0.05.
mm, and a gate of length X was machined at the interval of the dimension X, and the product part cavity and the product part cavity were directly connected by the gate. In the case of other plastic moldings, the standard injection pressure is as high as 1500-2500 kgf / cm ^2, and the 0.2 mm spacing design between the product part cavities does not have the injection pressure, which is very unthinkable. On the other hand, the injection pressure of liquid silicone rubber is as low as 100 to 800 kgf / cm ^2, and in the usual case, it is molded at 150 to 400 kgf / cm ^2, so that the interval of 0.1 mm is sufficient for durability. In addition, the good flowability of the liquid silicone rubber, which is promoted by the depressurization of the vacuum line from the molding end, is added, and the conventional fixing concept of the injection molding mold is shaken off and the interval is set to 0.02 ~.
The LIM molding method, which made the best use of the characteristics of liquid silicone rubber, was achieved by making the gate 1 mm and processing the gate there.

Next, the molding process will be described. Using the molding die described above, the inside of the cavity is depressurized by the vacuum device 18 in advance, and the liquid silicone rubber molding material such as the liquid silicone rubber of the addition mold is molded by the injection molding machine. , Sprue 1
3. Inject from the runner 14 into the cavity of the mold φ
5 Ball is molded. Subsequently, the mold is opened, and the sprue 13, the runner 14 for supplying the liquid silicone rubber to the product portion cavities in each row, and the second runner 17 are knocked out by the ejector pins 19 and 20, and the fixed side 11 and the moving side 12 both have blades. Taking out air, etc. Takes it out of the mold at the same time as the φ5 ball with attached equipment.

At this time, since the space between the φ5 balls is very narrow, the balls are separated from each other at the same time when they are taken out,
It becomes a product as it is. The sprue and runner can be separated from the product by the unloader. Table 1 shows a comparison of the molding conditions and efficiency of the φ5 balls of the example and the conventional example.

[0018]

[Table 1] * 1: Interval X is the distance between the outer circumference of the product section and the outer circumference of the product section. A gate was processed on X and the product section was directly connected to the product section. * 2: The number of molds that can be taken on one side is 24 ton
Number processed to 140 (mm) x H300 (mm). * 3: The sprue, runner, and gate are included in the runner and gate methods of the examples and conventional methods, so the weight of one shot was divided by the number of molds taken on one side. * 4: 1 per 1 in case of conventional runner gate method
Since the cold runner method of people, examples and conventional methods is automatic demolding, operation of the molding machine at the start of molding, occasional replacement of molded products overflowing the box after taking out the molding machine, and proper molding From the check of, it was 0.3 people / vehicle. * 5: Measured using Asker Micro Rubber Hardness Tester MD-1 manufactured by Kobunshi Keiki Co., Ltd. * 6: Put 10 g of the molded product into 100 ml of ion-exchanged water and 50 ℃ ×
After 24 hours, it was taken out, returned to room temperature, and measured with a pH meter.

[0019]

The effects of the present invention are listed below.

By reducing the outer peripheral distance between the product cavities and the product cavities to the utmost limit and connecting them directly with a gate, there is no need for conventional post-processing such as sprue, runner, gate cut and deburring, and material loss is also caused. Almost gone.

Further, the number of molds to be taken per one mold can be set to about twice as large as that of the conventional method, and the production efficiency is greatly improved. In addition, good flowability, low-pressure moldability, and fast curing properties, which are the most important features of liquid silicone rubber, could be fully utilized.

Particularly, it is suitable for a small product which is in great demand and a complicated shape can be dealt with by providing a vacuum line, so that the application of LIM molding is further expanded.

By providing a simple take-out facility, automatic demolding was possible, the number of personnel could be reduced, and a molded product having excellent characteristics and quality could be obtained.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view of a main part of a molding die used in an embodiment of the present invention, and FIG. 1 (b) is an enlarged cross-sectional view of a portion B of the chain line in FIG. 1 (a). It is a figure.

FIG. 2 shows the moving side mold 12 in FIG.
It is the top view seen from the direction.

[Explanation of symbols]

 11 Fixed Side 12 Moving Side 13 Sprue 14 Runner 15 Product Cavity, 16 Gate, 17 Second Runner, 18 Vacuum Line, 19 Sprue Ejector Pin 20 Runner Ejector Pin X Interval

Claims (1)

[Claims] 1. A liquid silicone molding method in which a plurality of product part cavities are arranged in a row in a molding die, and a gate formed in a space between the product part cavities is provided to connect the product part cavities in a beaded shape. A method for injection-molding a bead-shaped molded body that is easy to separate depending on the material, wherein (A) the interval X between the product cavity and the product cavity in the molding die is 1 mm ≥ X ≥ 0.02 mm, and the spacing is The processed gate has a structure in which the product cavity is directly connected to the product cavity, and (B) a vacuum device is connected to the product cavity at the end of the molding direction of the molding die to arrange the product cavity. A LIM molding method characterized in that the inside of the cavity is depressurized.