JPH0255209B2 - - Google Patents

Description

Detailed Description of the Invention (Objective) The present invention relates to a so-called casting method in which a reactive liquid resin such as an epoxy resin, polyester resin, or polyurethane resin is injected into a mold, hardened, and molded. The object of the present invention is to provide a casting method that can easily produce a good molded product that does not contain air bubbles and is well-filled even in the details of the mold even when a resin liquid with a fast curing speed is used.

(Prior art) Recently, parts have been frequently molded by the casting method, in which reactive liquid resins such as epoxy resins, polyester resins, and polyurethane resins are injected into molds, but in this case, the most problematic This results in air bubbles being mixed into the molded product, which becomes a major problem especially when a resin with a fast reaction rate is used.

In other words, measure the casting resin stock solution such as the base agent and curing agent,
When mixing, air from the atmosphere mixes into the resin liquid and creates bubbles, so these are defoamed in a vacuum box before being poured into the mold, but if a resin with a fast curing speed is used, defoaming is necessary. Due to the need to keep the time extremely short, defoaming is insufficient, resulting in air bubbles being mixed into the molded product.

In order to solve this problem, it is necessary to measure and mix the resin stock solution in a state where no air is mixed in. For this purpose, it is necessary to pump the resin stock solution, which has been vacuum degassed in advance to remove air, using a gear pump, bellows pump, etc. An automatic metering, mixing and dispensing machine that automatically measures, mixes and dispenses liquid in a sealed state using a liquid volume pump has been developed and is in use.

However, this automatic metering, mixing and dispensing machine is extremely expensive, and has the disadvantage that it is difficult to replace the resin liquid and is difficult to adapt to high-mix, low-volume production using many types of resin liquid. The present invention was achieved as a result of intensive research into a method for easily obtaining a molded product without the inclusion of air bubbles.

(Structure) That is, the present invention includes a resin stock solution storage tank for separately storing casting resin stock solutions such as a base resin and a curing agent connected to a vacuum evacuation device, and a first casting resin supply pot equipped with a stirring device. A second vacuum box containing a casting mold connected to a vacuum exhaust device and a compressed air supply device is connected via a resin supply pipe and sequentially deployed from an upper position to a lower position and maintained in a vacuum pumped state. The resin stock solution, that is, the main resin, curing agent, etc., stored in the storage tank is transferred to a casting resin supply pot housed in a first vacuum box located below the tank and maintained in an evacuated state. A predetermined amount of resin is dripped through the supply pipe introduced into the first vacuum box from the resin supply port, and at the same time as the stirring device finishes stirring and mixing, a second vacuum box is located further below the supply pot and maintained in a evacuated state. The resin is dripped into the casting mold housed inside through the supply pipe connected from the resin supply port of the supply pot to the resin injection port of the mold, and a series of casting operations are performed in an evacuated and airtight state. At the same time as filling is completed, the second mold containing the casting mold is placed.
This is a casting method characterized by introducing compressed air into a vacuum box and filling it under pressure, and the details are as described below based on Examples.

FIG. 1 is a sectional view showing an example of a casting apparatus for carrying out the casting method of the present invention, in which 1 and 1' are sealed tanks for storing resin stock solution, and 2 is a resin supply pot 4 located below the tank. 3 is a second vacuum box that houses a casting mold 5 located below the vacuum box 2; 6 is a vacuum pump; 7 is a compression pump;
15 is a connection pipe between the resin stock solution storage tanks 1, 1', the first and second decompression boxes 2 and 3, and the vacuum pump 6;
22 is a connection pipe between the second decompression box 3 containing the casting mold 5 and the squeeze pump 7; 9 is a cleaning liquid storage tank;
2, 12' are resin stock solution supply pipes, 13 are cleaning liquid supply pipes, 17 are supply pipes for casting resin liquid to the mold, 8 is a stirrer, 10, 10'11, 14, 16, 18, 19,
20 is a two-way or three-way opening/closing pot for performing the pouring operation.

(Function) Next, the casting method will be explained. First, the vacuum pump is activated to evacuate the resin stock solution storage tanks 1, 1' and the first and second vacuum boxes 2 and 3, so that the resin solution does not mix with the resin stock solution. The air contained in the tank is removed by vacuum defoaming and stored in a vacuum evacuation state, and both the first and second decompression boxes are maintained in a vacuum evacuation state, and then the opening/closing cocks 10, 10' are opened to open the storage tank 1, A predetermined amount of the resin stock solution 1' is dropped into the resin supply pot 4 according to the liquid volume scale attached to the tank, stirred and mixed by the stirrer 8, and then the opening/closing pot 16 is opened to pour the resin liquid into the casting mold 5. Drop filling is performed, and when the resin liquid overflows from the deaeration port 21, the opening/closing pot 16 is closed to stop the filling, and the opening/closing pot 19 is opened to introduce compressed air into the second vacuum box 3. is held in a pressurized state for a predetermined period of time, and the casting resin is filled into the mold under pressure to complete the casting operation.

After the casting work is completed, the first and second decompression boxes 2 and 3
The pressure is returned to atmospheric pressure by operating the opening/closing knobs 14 and 18, the mold is taken out and the cast product is cured,
The cleaning liquid is drained from the cleaning liquid storage tank 9 to clean the resin supply pot 4 and the resin supply pipe 17 in preparation for the next operation.

(Effects) A feature of the casting method of the present invention is that the resin stock solution, that is, the main agent and curing agent, is vacuum degassed and then stored in a vacuum evacuated state, so there is no air contamination and no moisture contamination. First of all, since there is no moisture, it is extremely easy to handle the polyurethane resin liquid, which should not be contaminated with moisture.

Next, according to the casting method of the present invention, the resin stock solution is stored with air removed, and even during subsequent mixing and stirring, no air is mixed in, and it can be immediately filled into molds without vacuum defoaming. Because I can,
Even when a resin with a fast curing speed is used, the curing reaction hardly progresses and the mold can be filled with excellent fluidity, and the mold can be filled under pressure using compressed air immediately after filling is completed. Therefore, even parts with complex shapes can be filled to the smallest detail of the mold, and a good cast product without air bubbles can be obtained.

The casting method of the present invention can be applied to all resins such as epoxy resins, polyester resins, and polyurethane resins, but it has a pot life of 2 minutes/2 minutes, which was difficult to cast in the past.
Even when using a polyurethane resin with a relatively high viscosity and a short pot life (viscosity 550 cps/25°C at 20°C), it has been possible to obtain a good molded product without inclusion of air bubbles.

Further, the device used in the present invention has a simple structure and is inexpensive, and is easy to operate.
In addition, equipment such as the resin supply pot can be easily cleaned and resin can be changed easily, making it suitable for high-mix, low-volume production using multiple types of resin. Automatic operation using a solenoid valve or the like makes the operation easier and faster, resulting in even smoother casting work.

As described above, the present invention can quickly and easily obtain a good molded product without air bubbles using an extremely simple device, and is also well suited for high-mix, low-volume production using multiple types of resin. This casting method is excellent in both quality and economy, and has great practical effects in industry.

[Brief explanation of drawings]

The drawing is a cross-sectional view showing an embodiment of a vacuum casting device used in carrying out the casting method of the present invention.
1 and 1' are resin stock solution storage tanks, 2 is a first vacuum box that accommodates a casting resin supply pot, 3 is a second vacuum box that accommodates a casting mold, 4 is a resin supply pot, and 5 is for casting. The mold 8 is a stirring device.

Claims (1)

[Claims] 1. A resin stock solution storage tank that separately stores casting resin stock solutions such as base resin and curing agent connected to a vacuum evacuation device, and a first vacuum box that accommodates a casting resin supply pot equipped with a stirring device and a vacuum evacuation device. and a second housing housing a casting mold connected to a compressed air supply device.
Decompression boxes are connected with resin supply pipes and sequentially arranged from the upper position to the lower position, and the casting resin stock solution, that is, the base resin, curing agent, etc. stored in the resin stock solution storage tank maintained in a vacuum evacuated state, is transferred to the tank. A molding resin supply pot housed in a first vacuum box located below the storage tank and maintained in an evacuated state is connected through a supply pipe introduced into the first vacuum box from the resin supply port of the storage tank. The resin supply port of the supply pot is placed in a casting mold housed in a second vacuum box located below the supply pot and maintained in a vacuum state. The resin is dripped and filled through the supply pipe connected to the resin injection port of the mold, a series of casting operations are performed in an evacuated and airtight state, and as soon as the filling is completed, the resin is poured into the second vacuum box containing the casting mold. A casting method characterized by introducing compressed air and filling under pressure.