JPS595383B2 - How to remove the mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of demolding a mold using microwaves in an investment casting method (precision casting method).

In the investment casting method, wax, urea resin,
A model is formed from heat-disappearing substances such as naphthalene or polystyrene, and many of these models are assembled to sprues, weirs, etc. made of the same material to form a tree, and then a mold material is coated on this tree to form a mold. , the eliminable substance is removed from within the mold to obtain a mold.

The removal of fugitive substances in this case is called demolding.

There are many types of demolding methods, including the autoclave demolding method that uses heated steam and the thermal shock method that uses a high-temperature heating furnace all at once, but one of them is the method that uses microwaves. be.

The principle of the microwave demolding method is that microwaves act on a model made of a fugitive material (dielectric material) inside a mold made by a normal method, causing it to generate heat. The purpose is to dissolve substances.

This method uses a relatively simple device and can recover fugitive substances without degrading them. It also generates little gas when the model melts, and the gas generated is easy to collect because it is at room temperature and pressure. In addition to this advantage, there are also great cost advantages, such as the equipment being simple and compact, and the recovered fugitive substances having little deterioration, making it possible to reuse them.

However, this demolding method has the disadvantage that the mold is more likely to break during demolding than the autoclave demolding method, thermal shock method, etc., and is particularly unsuitable for demolding a tree-shaped mold.

One of the reasons for this is that the thermal output is often small, and under conditions of room temperature and pressure, the fugitive model expands and cracks the outer mold as it gradually heats up.

Another reason is that steam and gas generated by fugitive substances cannot be quickly extracted from the inside of the mold, and the mold cracks due to the pressure of these steam and gas.

In the above-mentioned microwave demolding method, the present invention prevents mold cracking without repeating multiple tests in casting method design by delaying the microwave irradiation on the previously detected parts of the mold that are likely to break. This provides a method to prevent this.

That is, the method for demolding a mold using microwaves of the present invention involves attaching a shield to a fragile part of the mold containing a fugitive substance to be demolded, delaying the melting of the part, and then irradiating the mold with microwaves. It is characterized by:

Next, an embodiment of the method of the present invention will be described using FIG.

In the figure, A is a tree made of dielectric material that absorbs microwaves and generates heat, and is made of a large number of models a) a e
a Weir 2..., b, runner (trunk) through b...
The tree A is attached to the tree A, and one end of the runner C is provided with a riser port d, and the outer periphery of the tree A is provided with a mold B coated with a microwave-transparent fireproof material.

This tree A is assembled using a threaded shaft and nut, and the outer circumference of the tree I)-A is coated with several layers of refractory coating using refractory slurry in a well-known manner. The metal shaft at the center of the tree trunk C was taken out after mold B was made, where e is the hole left when the shaft was removed, and 13 is the nut remaining at the top of tree A.

A mold B having the above-described tree A therein is set with the riser port d facing down on a turntable 3 provided at the bottom of a shield box 1 having a microwave irradiation port 2 at the top.

This turntable 3 is connected to a separately provided rotary drive device (not shown), and the bottom surface of the shield box 1 is supported by a rotary shaft 6 inserted vertically from the center.

This table 3 is made of a microwave blocking material.

Conventionally, microwaves were irradiated into the shield box 1 in this state, but in this case there was a problem that the tip of the mold always broke.

The reason for this is thought to be that the fugitive substance inside the mold B absorbs the microwave and melts and expands before the lower part elutes, or the generated gas accumulates. It will be done.

In the method of the present invention, a cap 14 made of a metal capable of blocking microwaves is placed over the easily breakable part of the tip of the mold B, thereby reducing the microwave absorption of the fugitive substance in this part more than in other parts. I also tried to delay it.

After the other part, that is, the lower part of Tsu'J-A, has eluted,
The cap 14 is removed and the microwave is irradiated again to completely elute the vanishing substance.

At this time, the nut 13 is demolded at the same time.

Although not shown in the drawings, the fugitive substances that have melted can be taken out from the area by providing holes or grooves in the part of the turntable 3 that is covered with the mold B, or by making the shaft 6 hollow. Also good.

According to the above method, the parts of the mold that absorb microwaves and melt, causing thermal expansion or gas generation are covered with caps, which delays the melting of fugitive substances in those parts and prevents mold cracking. The occurrence can be effectively prevented.

In the method of the present invention, for example, a jig as shown in FIG. 2 can be used.

Figure 2 shows a mold removal device with the structure shown in Figure 1, in which a jammer plate is installed to locally block microwaves or to control the degree of microwave application by rotating the turntable. A circular band 8 is formed by joining both ends of a band-shaped metal plate to the support 7, and an appropriate number of these bands 8 are attached in parallel to the support 1 at a predetermined interval, and then attached to the top center of the support 7. is provided with a metal cap 9.

If the above jig is used, the parts of the mold having the structure shown in Fig. 1 that are prone to cracking, such as the tip of the mold and the part of the mold adjacent to model a, can be covered, so that the microwave absorption in these parts can be reduced. Mold cracks caused by delays, thermal expansion, etc. can be effectively prevented.

When using a jig with the configuration shown in Fig. 2, mold B containing a fugitive substance is set in this jig, and the turntable 3 is irradiated with microwaves at rotational speeds of 5 r , p , and m. As a result, no cracking of the mold occurred.

The microwave used at this time was 2450 h, the irradiation time was 5 minutes for the first time, 10 minutes for the second time, urea resin was used as the evanescent substance, and the ratio was 1.8 to 9.

However, the shape of the jig is not limited to the above, and should be determined in advance by taking into consideration the position of the part where mold cracks are likely to occur during demolding, the position of the irradiation port, and the rotation speed of the turntable. Designed with.

Generally, it is desirable to melt the feeder first, then the runner, the weir, and the model, and the model should be designed so that the part furthest from the weir is melted last.

As is clear from the above description, the mold demolding method using microwaves of the present invention can prevent cracking without any special devising in the casting method design by using a very simple shield. It is very easy to operate.

In addition, since the fugitive substances are removed smoothly, there are various advantages such as less deterioration, higher recovery rate, and great advantages in recycling and reuse.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the first embodiment of the method of the present invention;
The figure represents a perspective view showing part 1 of the microwave shielding jig used in the method of the present invention. In the figure, 1... Shield box, 2... Microwave irradiation port, 3... Turntable, 6... Rotating shaft, 7...
Support, 8...Band, 9...Cap, A...Tree, B...Mold.

Claims (1)

[Claims] 1. An investment casting method characterized by attaching shields to easily breakable parts of a mold containing a fugitive substance to be demolded and delaying the melting of the fugitive substance in the part, followed by irradiation with microwaves. Method for demolding the mold.