JPH0588180B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a cylindrical body made of fiber reinforced plastics (FRP) used as a component of a pressure-resistant container, a high-speed rotating body, etc. A method that improves workability during the grinding process of cylindrical bodies, in which a prototype is created by the cutting method and the outer surface is finished ground to produce a product, and also improves the reliability of the finished product in terms of accuracy. Regarding.

[Conventional technology]

FRP cylindrical bodies are often manufactured by the so-called filament winding method, in which resin-impregnated continuous fibers are wound around a mold with a circular cross section, the resin is heated and cured, and then removed from the mold. Since the cylindrical body obtained by this method is likely to have uneven thickness, it is necessary to remove this in applications that require precision.

On the other hand, in order to take advantage of the characteristics of FRP, which are lightweight, high strength, and high elasticity, it is necessary to minimize the amount of fiber breakage after molding. In particular, in the case of thin-walled cylindrical bodies, the required strength must be obtained with a small number of fibers, so there is a strong demand for this. For this reason, the FRP cylindrical body obtained by the above method generally leaves the inner surface as it was when demolded, and only the outer surface is machined to remove uneven thickness.

The conventional method for machining the outer surface of the FRP cylindrical body 1 is as shown in Fig. 4.
The core body 2 is inserted into the cylindrical body in a state where a frictional force is generated against the cylindrical body, and the core body 2 is mounted on a processing machine such as a lathe or a grinder to cut or grind the outer surface.

[Means for the invention to solve the problem]

However, in the conventional method described above, if the coefficient of thermal expansion of the FRP cylindrical body before demolding is larger than that of the mold, the cylindrical body tightly adheres to the mold after heating hardening and cooling, making demolding difficult. Therefore, the disadvantage is that the cylindrical body must be removed from the mold by applying a punching force or a pulling force using some kind of pressure loading device, and furthermore, when a large demolding pressure is applied, the cylindrical body may be damaged. There is a drawback.

In addition, when machining the outer peripheral surface, the conventional method of inserting a machining core after removing the mold from the mold
Because a gap is likely to occur between the FRP cylindrical body and the core body,
It is difficult to increase uneven thickness removal rate. On the other hand, if the method of reducing the gap by forcefully pushing the core body is adopted, the inner surface of the cylindrical body will be damaged and the quality will deteriorate.

Here, if it is difficult to replace the mold and core, it is possible to use the mold as it is as a core for processing, but there is a partial gap between the FRP cylindrical body and the mold after hardening. In this case, when the FRP cylindrical body is not in uniform contact with the mold, uneven thickness may not be removed during machining performed based on the core, and moreover, due to the machining of the outer surface. A cylindrical body whose inner diameter changes and shrinks makes demolding even more difficult.

[Means for solving problems]

In order to solve the above problems, the present invention firstly solves the above problems.
A mold having a structure as shown in FIG. 1 is used. The illustrated mold 3 has a cylindrical body 5 with a shaft 4 for attaching it to a winding machine or a processing machine at both ends of the axial center, and an elastic deformable body airtightly integrated on the outer periphery of the body through a pressure applying chamber 6. It consists of an outer cylinder 7 that can be used as a pressurizer, and a means 10 for maintaining the pressure in the pressure chamber 6, such as a stop valve, which is inserted in the middle of a pipe 9 connected to the pressure introduction port 8. When the pressure increases, the outer cylinder 7 expands and expands in diameter.

Now, in the method of the present invention using such a mold, pressurized fluid such as oil is introduced into the above-mentioned pressure adding chamber 6, and the outer cylinder 7 of the mold 3 is moved from the chain line position in FIG. 2 to the solid line line. In the first step of expanding the diameter at the position, a resin-impregnated fiber bundle is wound around the outer circumferential surface of the diameter-expanded mold 7 in a predetermined orientation and thickness using the filament winding method, and the resin is heated and hardened to obtain the FRP cylindrical body 1. In the second step, by applying a higher internal pressure than in the first step, the outer cylinder 7
In the third step, the diameter of the mold is further expanded from the solid line position in Fig. 2 to fully adhere to the inner surface of the cylindrical body 1.The mold 3 is mounted on a processing machine such as a lathe or a grinder, and In the fourth step, the outer surface of the cylindrical body 1 is centered and the outer surface of the cylindrical body 1 is ground to remove uneven thickness, and the pressure inside the additional chamber 6 is removed and the outer cylinder 7 is reduced to its original diameter. As shown, the steps of the fifth step of creating a gap between the cylindrical body 1 and the outer tube 7 and the sixth step of extracting the cylindrical body 1 from the mold 3 are obtained.

According to this method, in the third step, the mold and
Since the gap between the FRP cylinder and the body completely disappears,
Uneven thickness can be reliably removed by using the mold as a core for processing.

In addition, the mold whose diameter has been expanded in the first step is
Since the diameter is reduced in this step to a smaller value than when the resin-impregnated fibers are wound, it is also possible to eliminate the need to apply demolding pressure to the cylindrical body in the sixth step.

The diameter expansion rate and diameter reduction rate of the mold 3 may be appropriately set in consideration of the difference in coefficient of thermal expansion between the FRP cylindrical body and the mold, and the change in the inner diameter of the cylindrical body due to processing of the outer surface. The diameter of the mold can be controlled depending on the degree of internal pressure load.
The setting value can be selected arbitrarily.

〔effect〕

As described above, in the method of the present invention, an FRP cylindrical body is formed on a mold whose diameter has been expanded in advance, and the machining of the outer peripheral surface of the cylindrical body is performed by further expanding the diameter of the mold. Finally, the diameter of the mold is reduced to a smaller diameter than when wrapping the fibers and the mold is removed, so the work of replacing the mold with the processing core and the associated FRP It is possible to eliminate scratches on the cylindrical body, and when grinding the outer circumferential surface, it is possible to expect processing with a high uneven thickness removal rate in which the grinding knife or grinding wheel hits the same circumference over the entire length of the cylindrical body.

Furthermore, demolding can be performed without applying pressure to the cylindrical body, which makes it very simple, and there is no damage to the cylindrical body due to demolding pressure.

Therefore, high quality FRP cylindrical bodies can be easily mass-produced.
It becomes possible to obtain it cheaply. Among these, in the production of GFRP (glass fiber reinforced plastics) cylinders, which have a coefficient of thermal expansion larger than that of the mold, it is important to make demolding easy, and in the case of thin-walled cylinders, it is difficult to apply unreasonable demolding pressure. A particularly great effect can be expected from the point that there is no need to insert a processed core.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an example of a mold used in the method of the present invention, Figures 2 and 3 are explanatory diagrams of the method of the present invention using the mold, and Figure 4 is an explanation of the conventional method. It is a diagram. 1... FRP cylindrical body, 3... Mold, 4... Shaft, 5... Cylindrical body, 6... Pressure addition chamber,
7...Outer cylinder, 8...Pressure inlet, 9...Pipe,
10...Pressure holding means.

Claims (1)

[Claims] 1. The first step is to expand the diameter of the mold using an internal pressure applying means that can maintain pressure.The resin-impregnated fiber bundle is wound around the outer peripheral surface of the expanded mold to a predetermined orientation and thickness based on the filament winding method, and then heated. The second step is to harden and obtain a cylindrical body. The third step is to further expand the diameter of the mold by applying a higher internal pressure than the first step and make it adhere to the cylindrical body. The outer surface of the cylindrical body is measured based on the mold. The fourth step is to remove uneven thickness by grinding, the fifth step is to reduce the diameter of the mold by removing internal pressure and create a gap between it and the cylinder, and the sixth step is to extract the cylinder from the mold. A method of manufacturing a fiber-reinforced plastic cylinder comprising: