JPS5837052B2 - How to make a mold - Google Patents

Description

Detailed Description of the Invention The present invention involves heating molding sand coated with a thermoplastic resin to a temperature higher than the melting point of the thermoplastic resin and filling it into a model, and then cooling and hardening the molding sand filled in the model to form a mold. This relates to improvements in the manufacturing method.

The applicant has filed Japanese Patent Application No. 51-1061 (Japanese Unexamined Patent Publication No. 52-84)
No. 124), molding sand mixed with thermoplastic resin powder or coated with thermoplastic resin is heated above the melting point of the thermoplastic resin, and then the heated molding sand is heated in a model with high-temperature compressed air. We proposed a method for manufacturing molds by blowing the molding sand into the mold, cooling it, and solidifying the thermoplastic resin around the molding sand to bind the molding sand together.

When using the method of Japanese Patent Application No. 51-1061 (Japanese Unexamined Patent Publication No. 52-84124) as a high-speed mold manufacturing method that is currently strongly desired to be developed, the molding sand filled in the model is cooled in a short time. That is the most necessary thing.

This is because, currently, when producing mass-produced castings, the main mold is manufactured using a high-pressure molding machine in around 20 seconds per frame, but the core used for this is produced using a shell mold method that uses thermosetting phenolic resin. It takes 90 to 15 Qsec to manufacture, and this is because the molding balance between the main mold and the core is not balanced.

The above-mentioned imbalance in the molding time between the main mold and the core is a major obstacle in high-speed mold manufacturing methods.

Therefore, there is a strong demand for the development of a high-speed core (mold) manufacturing method that can compete with the speed of high-pressure molding for manufacturing the main mold.

An object of the present invention is to provide a method for cooling and hardening molding sand coated with a thermoplastic resin filled in a model in a short time.

Embodiments of the present invention will be described with reference to the drawings. In the apparatus shown in FIGS. 1 and 2, 1 is a core shooter, and the molding sand 2 coated with a thermoplastic resin is heated at a temperature higher than the melting point of the thermoplastic resin. Model 3 is heated and kept warm at the same time.
Blow molding sand 2 inside.

A heater 4 is installed around the core shooter 1 to heat and keep the molding sand 2 warm.

In addition, at the top of the core shooter 1, there is an air chamber 5 for temporarily storing compressed air used when blowing the molding sand 2 into the model 3, and a pipe for guiding compressed air from the compressor 6 into the air chamber 5. 7 is installed.

The foundry sand 2 has a composition (wt%) of, for example, 97% silica sand and 3% resin (methacrylic resin).

The model 3 has a cavity (female mold) in the shape of the mold to be produced, and is made of plastic, wood, metal, or the like.

Inside the model 3, there are a back part 3a of the model 3 and an inner surface 3 of the model 3.
A ventilation hole 8 is provided which communicates with the model inner surface 3b, and a slit 9 is installed in the ventilation hole 8 on the model inner surface 3b side to prevent the foundry sand 2 from escaping to the model back 3a.

Further, a filling port 10 is provided in the upper part of the model 3 for filling molding sand 2 from the core shooter 1.

Furthermore, an air intake port 11 having a plurality of air intake holes is provided in the lower part of the model 3 in order to exhaust the air in the molding sand 2.

Reference numeral 12 denotes a suction box, which sucks (exhausts) air contained in the molding sand 2 filled inside the model 3.

There is a space 13 inside the intake box 12, and a vacuum pump 14
It communicates with a pipe 15 connected to.

A first embodiment of the present invention using such a device will be described below.

■ 97% silica sand and 3% methacrylic resin are mixed in a container (not shown) to produce molding sand 2 coated with thermoplastic resin.

(2) Insert the blended foundry sand 2 into the core shooter 1.

(2) A current is applied to the heater 4 attached to the core shooter 1 to heat the methacrylic resin to a melting point of 260° C. or higher.

Therefore, the foundry sand 2 has increased fluidity.

Note that the heater 4 continues to keep the methacrylic resin warm so that it continues to melt.

■ Meanwhile, use the compressor 6 to increase the air pressure in the air chamber 5 to approximately 5 k9/ffl.

■ Compressed air (approximately 5k9/cm) is supplied from the air chamber 5.
cr/l) is fed into the core shooter 1, and the molding sand 2, which has been fluidized, is filled into the model 3.

(2) After removing the core shooter 1 from the model 3, operate the vacuum pump 14.

As a result, the air contained in the foundry sand 2 passes through the space 13 of the intake box 12 from the intake hole of the intake port 11 as shown by arrow A, and is sent to the vacuum pump 14 via the pipe 15. It is then discharged.

■ In this state, the molding sand 2 is inside the model back 3a.
Since the pressure is negative with respect to the surrounding external pressure, the air around the model back 3a is sucked into the model 2 through the ventilation hole 8 as shown by arrow B.

(2) The air sucked in from the model back 3a flows from the ventilation hole 8 to the molding sand 2 and then to the air intake box 12, so that the molding sand 2 that comes into contact with the model inner surface 3b is filled with the methacrylic resin. It is cooled to below its softening temperature (approximately 140°C) and hardens.

[Phase] For the reasons explained above, the foundry sand 2 has
It hardens in a short time from the part that contacts the inner surface 3b of the model toward the center.

FIG. 2 shows such a state, where 2a shows a hardened layer and 2b shows an unhardened layer.

When the hardened layer 2a is formed to such an extent that it does not collapse even when the mold is released, the hardened molding sand 2 is taken out from the model 2 to obtain a core (mold).

Next, in the apparatus shown in FIG. 3, the members shown at 1 to 15 are substantially the same as the members shown at 1 to 15 in FIG.

16 is an air box, which has a space 11 inside, and the air box 1
One end of 6 is connected to a compressor 18 by a pipe 19.

The space 17 communicates with the molding sand 2 filled in the model 3 through the ventilation hole 8 .

A second embodiment of the present invention using such an apparatus will be described below.

Work steps ① to ② in this second embodiment are the same as work steps ① to ② in the first embodiment.

(2) Operate the compressor 18 and blow compressed air (approximately 2 to 3 k9/CI!) into the model 3 from the air box 16.

(2) At the same time, the vacuum pump 14 is operated to quickly suck out the air in the molding sand 2 in the model 3 from the suction box 12.

(2) Compressed air is introduced into the model 3 from the model back 3a through the ventilation hole 8 as shown by arrow C, and this compressed air is then introduced into the exhaust port 11 as shown by arrow D.
First, the inner surface of the model 3 is
The foundry sand in contact with b is cooled to a temperature below the softening temperature of the methacrylic resin (approximately 140° C.) and hardens.

(2) For the reasons explained above, the molding sand 2 hardens in a short period of time from the portion that contacts the inner surface 3b of the model toward the center.

[Phase] When the hardened layer is formed to the extent that it does not collapse even when the mold is released, take out the hardened foundry sand 2 from the model 2,
Obtain the mold (core).

In this way, the present invention has the following effects.

■ Since the area of the molding sand that comes into contact with the inhaled air is large, a large amount of molding sand hardens in a short period of time.

■ Since the molding sand hardens from the part where the outer shell of the core (mold) is formed, it is possible to release the mold without hardening to the center of the molding sand.

Therefore, the mold can be released in an extremely short time compared to releasing the mold after all of the filled molding sand has hardened.

If it is made as a core (mold) for mass production and weighs less than 5k9, approximately
Since it can be released from the mold once it has been cured to a certain extent, it is possible to release the mold in a short time, that is, to produce a core (mold) at high speed.

(2) If the inside of the core (mold) released by the method (2) is sucked out, the unhardened molding sand inside the core (mold) will be removed and a hollow core (mold) will be obtained.

■ Inside the molding sand filled in the model, decomposed heptomer of the binder resin is present, but it is exhausted through the intake box, so no odor is emitted from the core (mold) to the surrounding area, allowing for good work. You can get the environment.

(2) In the first embodiment, it took about 35 seconds to fill the molding sand into the mold and release it from the mold to manufacture a core weighing 1.5 kg.

Therefore, the core production time can be significantly reduced compared to the conventional method.

In the second embodiment, the amount of air flowing through the foundry sand is much larger than that in the first embodiment, so that the hardening speed of the foundry sand is increased.

To manufacture a core weighing 1.5 kg, the mold can be released in about 25 seconds after filling the molding sand into the model, and the first
It was further shortened compared to the example.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a first embodiment of the present invention, FIG. 2 is a sectional view showing a state in which the foundry sand is hardened in FIG. 1,
FIG. 3 is a schematic explanatory diagram showing a second embodiment of the present invention. 1... Core shooter, 2... Foundry sand, 3... Model, 4... Heater, 5... Air chamber 6
... Compressor 8 ... Ventilator

Claims (1)

[Claims] 1. A method of manufacturing a mold by heating molding sand coated with a thermoplastic resin to a temperature higher than the melting point of the thermoplastic resin, filling a model with the heated molding sand, and then cooling and hardening the molding sand. After blowing and filling the molding sand into the model, the air in the molding sand is sucked out from one part of the model to suck air into the molding sand from the back of the model,
A method for manufacturing a mold, characterized in that the molding sand in the portion that comes into contact with the model is rapidly cooled to below the softening point of the thermoplastic resin.