KR100534063B1 - apparatus and method for manufacturing a blow-molded fluoropolymeric bellows with an uniform thickness - Google Patents

Abstract

The present invention relates to a blow-molded fluororesin bellows, a manufacturing apparatus and a manufacturing method thereof, having a uniform pleated thickness, wherein the core mold is designed in a split form, and an elastic means is inserted between the core molds. And assembling the fluorine resin tube with the mold apparatus while maintaining a constant distance between the core molds, and blow molding the press apparatus by applying air pressure into the tube. According to this, it is possible to produce a bellows with a uniform thickness of the wrinkles portion has the effect of improving the durability of the product.

Description

Apparatus and method for manufacturing a blow-molded fluoropolymeric bellows with an uniform thickness

The present invention relates to a blow molded fluororesin bellows, a manufacturing apparatus and a manufacturing method thereof, and more particularly, a fluororesin made of a fluororesin bellows, a split core mold and an elastic means, etc., characterized in that the thickness of the wrinkles is uniform. It relates to a mold apparatus for bellows and a method for producing a fluororesin bellows using the same.

In general, the bellows is a mechanical part having a circular cross section and a structure in which a plurality of corrugations are formed in the longitudinal direction, and is a connecting pipe for controlling the amount of deformation caused by thermal expansion and contraction in a pipeline, a pressure vessel, or the like. This bellows is very useful for absorbing and blocking the deformation caused by noise, vibration, thermal expansion, etc. generated in various industrial pumps or engines. Such bellows are manufactured by cold die-rolling a material such as phosphor bronze or stainless steel or by blow molding a synthetic resin material. Many chemicals use fluorine resins with excellent chemical resistance.

Conventional blow molding methods for molding a fluororesin bellows include: (a) flaring both ends of a tube made of fluororesin and assembling a mold apparatus; (B) heating the assembled tube and the mold apparatus; (C) pressurizing both ends of the mold apparatus with a press and then pressurizing compressed air into the tube; And (d) a cooling take-out step. .

1A is a cross-sectional view of a portion of a fluororesin bellows manufactured according to a conventional method. As shown in Figure 1a, the fluorine resin bellows manufactured by the conventional manufacturing method has a disadvantage that the thickness of the circumferential wall becomes thinner toward the outer end of the wrinkles. This is because the length of the expanded fluororesin tube is shorter than the length of the bellows crease expanded by pressure. Due to the non-uniform thickness of the pleated portion of the fluororesin bellows, the conventional products tend to be damaged by the pressure of the thin portion of the pleated portion when the fluid moves at high pressure, and there is a difficulty in predicting the replacement cycle of the product.

FIG. 2 shows a conventional mold apparatus used in the molding process of the fluororesin bellows shown in FIG. 1. The conventional four-part mold apparatus includes an upper die 11, a lower die 14 having an air injection portion 14a, and two core molds 13 which are symmetrical and engageable with each other. However, the conventional mold apparatus has a problem that only one type of product can be molded with a set of core molds. For example, with a mold apparatus having five sets of core molds, only five bellows products (a bellows product having five corrugations) could be molded.

Therefore, in order to manufacture other kinds of bellows products, the mold apparatus must be manufactured and used separately, so that the manufacturing cost of the mold increases, and if the other products are produced, it is inconvenient to replace the entire mold, thereby increasing the production time. exist.

As a result, the conventional blow molding technology of the fluororesin bellows has a problem in that the cost for the mold apparatus is excessively consumed and the thickness of the wrinkle part of the product is uneven to shorten the life cycle of the product.

The present invention is to solve the above-mentioned general drawbacks, the technical problem to be achieved by the present invention is a cylindrical housing, an upper die, a lower die, upper and lower core molds, a plurality of intermediate core molds and the core molds It is to provide an apparatus for producing a fluorine resin bellows having a uniform thickness of the pleats, characterized in that it comprises a plurality of elastic means located between.

Another object of the present invention is to provide a blow molding method of the fluororesin bellows using the manufacturing apparatus.

Another technical problem to be achieved by the present invention is to provide a bellows of blow molded fluorine resin, characterized in that the wrinkle portion according to the manufacturing apparatus and method has a uniform thickness.

Mold apparatus for blow molding the bellows according to the present invention for achieving the above object is a cylindrical housing; An upper die located at an upper end of the housing; A lower die positioned at an inner bottom of the housing and having an air inlet formed therein; Upper and lower core molds housed in the housing in contact with the lower die and the upper die inner surfaces, respectively; A plurality of intermediate core molds positioned between the upper core mold and the lower core mold, the diameter of the upper end portion and the lower end portion being larger than the diameter of the center portion; And a plurality of elastic means positioned between the upper core mold and the intermediate core mold, between the intermediate core mold and the intermediate core mold, and between the intermediate core mold and the lower core mold.

Further, in the above-described mold apparatus, a plurality of through holes are formed in the upper die and the lower die, and a plurality of tabs are formed in the upper and lower core mold surface portions in contact with these dies to allow the bolt to pass through the through holes. The upper die and the upper core mold and the lower die and the lower core mold are then integrated by receiving in the tab.

Further, in the above mold apparatus, it is preferable that grooves for accommodating the flared portions of the fluororesin tube are formed in the upper die and the lower die in contact with the flared portions of the fluororesin tube.

In the above mold apparatus, the upper and lower core molds and the plurality of intermediate core molds are provided with a plurality of grooves for accommodating one end of each elastic means on a contact surface in contact with another adjacent core mold. desirable.

Further, in the above mold apparatus, it is preferable that the upper and lower core molds and the plurality of intermediate core molds are composed of two symmetric members that can be joined to take out the molded bellows.

On the other hand, the fluorine resin bellows blow molding method according to the present invention,

(A) mounting one end of the flared tube of fluororesin to the mold apparatus, and flaring another end;

(B) heating the mold apparatus;

(C) compressing the mold apparatus by pressurizing one end of the mold apparatus after injecting low pressure compressed air into the tube 31 through the air inlet of the lower die;

(D) inflating the tube 31 to the mold surface by injecting high pressure compressed air into the tube 31 while the mold apparatus is compressed; And

(E) cooling the mold apparatus and then dismantling the mold apparatus.

In addition, in the above manufacturing method, the mold apparatus includes a cylindrical housing; An upper die located at an upper end of the housing; A lower die positioned at an inner bottom of the housing and having an air inlet formed therein; Upper and lower core molds housed in the housing in contact with the lower die and the upper die inner surfaces, respectively; A plurality of intermediate core molds positioned between the upper core mold and the lower core mold, the diameter of the upper end portion and the lower end portion being larger than the diameter of the center portion; And a plurality of elastic means located between the upper core mold and the core mold, between the intermediate core mold and the intermediate core mold, and between the intermediate core mold and the lower core mold.

In addition, in the above manufacturing method, the step (a) comprises the steps of flaring one end of the tube of the fluororesin; Sequentially assembling the one end flared tube and the upper die of the mold apparatus and the plurality of intermediate core molds, and then positioning support means and elastic means between the core molds; Engaging the lower die in a state in which one end of the flared tube is accommodated in each mold internal space, and then pressurizing to flare the other end of the tube; Injecting 1 to 8 kg / cm 2 of compressed air into the tube and then removing the support means; And after receiving the respective molds in the housing, reducing the pressure in the tube to atmospheric pressure.

Further, in the above production method, the heating temperature in the step (b) is 320 to 385 ℃ and the heating time is 80 to 140 minutes, in the step (c) the mold pressing force is 40 to 60 kg / ㎠, air pressure Is 0.2 to 3 kg / cm 2, and the pressure of the compressed air in the step (d) is preferably 10 to 20 kg / cm 2.

On the other hand, the bellows according to the present invention is made of a fluorine resin, characterized in that the wrinkle portion has a uniform thickness.

In addition, the fluorine resin is preferably made of one selected from the group consisting of Perfluoroalkoxy (PFA), Fluorinated Ethylene Propylene (FEP), and Ethlyene-Tetrafluoroethylene (ETFE).

Hereinafter, a blow molded fluororesin bellows according to a preferred embodiment of the present invention, a manufacturing apparatus and a manufacturing method thereof will be described in detail with reference to the accompanying drawings.

1B is a cross-sectional view of a part of the blow molded fluororesin bellows of the present invention. As shown in Fig. 1B, one example of the blow molded fluororesin bellows according to the present invention is, unlike the conventional blow molded fluororesin bellows shown in Fig. 1A, the thickness of the wrinkles is uniform throughout. The specific shape of the wrinkle part may be arbitrarily changed as the shape of the core mold of the present invention is changed, and even if the shape of the wrinkle part is changed, the thickness of the wrinkle part may be kept uniform by adjusting the gap between the core molds. have.

Table 1 shows the results of measuring the thickness of each of the pleated portions of the bellows (Sample 1) and the bellows (Sample 2) manufactured according to the embodiment of the present invention for the 1.8 mm fluororesin tube according to the conventional molding method. Indicated. As shown in Figures 1a and 1b, wrinkles A and C represent the peaks and valleys of the wrinkles, respectively, and the expansion of the tube occurs more and more from C to the portion A. The thickness of the wrinkle part may be measured by cutting a portion to be measured by a thickness measuring device such as a conventional method known in the art, more specifically, a thickness meter.

Table 1. Comparison of thickness measurement of blow molded fluororesin bellows (unit mm)

A B C Psalm 1 0.3 1.1 1.6 Psalm 2 1.1 1.7 1.5

On the other hand, the fluorine resin can be molded by selecting from a commercially available fluorine resin known in the art such as PFA, FEP and ETFE, preferably has a low melt index (Melt Index) of the fluorine resin blow The fluorine resin suitable for molding can be selected and molded.

Figure 3 is a schematic cross-sectional view of a mold apparatus according to an embodiment of the present invention for the blow molding of the fluororesin bellows, as shown in Figure 3, the mold apparatus according to an embodiment of the present invention is a lower die 24 , The lower core mold 22, the plurality of intermediate core molds 23, the upper core mold 22, and the upper die 21 are stacked, and each member is accommodated in the housing 25.

The upper and lower core molds 22 and the plurality of intermediate core molds 23 are divided, and a plurality of elastic means 26 are located between each core mold so that each core mold maintains a constant distance. Therefore, since the length of the tube expanded in the shape of the core mold by the high pressure air can be sufficiently secured, the thickness of the wrinkle part can be kept uniform. The spacing between the above core molds can be changed depending on the shape of the bellows crease, more specifically, the arc length of the bellows crease.

The elastic means 26 in the mold apparatus according to the embodiment of the present invention shown in FIG. 3 is compressed when the upper die 21 or the lower die 24 is pressed to closely adhere to each core mold 22, 23. By forming a wrinkled portion of a desired shape can be formed. Each of the elastic means 26 has a different elastic force according to its position, and preferably a coil spring in which the restoring force disappears after compression.

The housing 25 in the mold apparatus shown in FIG. 3 is for accommodating the upper die 21, the lower die 24, the upper and lower core molds 22, and the plurality of intermediate core molds 23.

In the mold apparatus, the cylindrical housing 25, the upper die 21, the lower die 24, the upper and lower core molds 22, and the plurality of intermediate core molds 23 are excellent in strength, toughness and wear resistance, and have high temperature. It may be made of a material having a low expansion property in, preferably an alloy tool steel (STD), nickel chromium steel (SNC) and the like can be used.

4 is a cross-sectional view of the upper die and the lower die in FIG. 3, where FIG. 4A shows the upper die 21 and FIG. 4B the lower die 24, respectively.

As shown in FIGS. 4A and 4B, grooves 21c for accommodating both ends of the flared fluororesin tube 31 of FIG. 7 are formed on outer surfaces of the upper die 21 and the lower die 24. 24c) are formed, respectively, so that the tube and the upper and lower dies 21 and 24 can be sealed to pressurize the inside of the tube. On the other hand, the lower die 24 has an air inlet 24a for injecting air into the tube at the center thereof.

4A and 4B, the upper and lower dies 21 and 24 are formed with a plurality of through holes 21b and 24b, and each through hole is formed of upper and lower core molds (to be described later). 22).

5 is a plan view of an upper (or lower) core mold in contact with an upper die (or lower die), wherein a plurality of tabs 22b are formed on a surface of the upper and lower core molds 22 which contact upper and lower dies. It is. Thus, the bolt is penetrated through each of the through holes 21b and 24b of the upper die and the lower die 21 and 24, and then accommodated in the tab 22b of the upper and lower core molds 22, so that the upper die 21 and The upper core mold 22 and the lower die 24 and the lower core mold 22 can be integrated. Accordingly, it is possible to completely seal between the upper and lower dies 21 and 24 and the corresponding upper and lower core molds 22 to pressurize the tube 31 by air pressure.

On the other hand, the upper surface and the lower core mold 22 has a plurality of tabs for receiving one end of the elastic means 26 on the opposite surface of the surface on which the plurality of tabs 22b are formed, that is, the surface contacting the intermediate core mold 23. The groove is formed to prevent the separation of the elastic means 26 when the mold is compressed.

As described above, the upper and lower core molds 22 are divided, and two or more (in this embodiment, two members) symmetrical members are combined to form a single upper and lower core mold 22. Form each.

As shown in FIG. 5, horizontal through holes 22c are formed in the respective members constituting the upper and lower core molds 22 to engage and disassemble the other members. The bolt can be inserted through the through-hole of one member to pass through the through-hole of both members, and then the two members can be configured as a single upper and lower core mold 22 by engaging the nut at one end of the other member. (Of course, the binding state can be decomposed through the reverse process, and the description thereof is omitted).

6A and 6B are cross-sectional views and a plan view of one intermediate core mold 23, each intermediate core mold 23 may also be composed of two symmetrical members that can be joined to take out the molded bellows, the combination of both members And parts for decomposition.

That is, as shown in Figs. 6A and 6B, horizontal through holes 23c for fastening and disassembling are formed in each member constituting each intermediate core die 23. Figs. The bolt can be inserted through the through-hole of one member to pass through the through-hole of both members, and then the two members can be configured as a single intermediate core mold 23 by engaging the nut at one end of the other member (of course). , The binding state can be broken through the reverse process, and the description thereof will be omitted).

On the other hand, a plurality of grooves 23b are formed on both surfaces of each intermediate core die 23. As described above, one end of each elastic means 26 is accommodated in the elastic means receiving portion formed on the surface of the upper or lower core mold 22, and the other end is the elastic means receiving portion 23b of the intermediate core mold 23. It is kept in). Therefore, when each mold is compressed, the separation of the elastic means 26 does not occur.

7 is a view showing the manufacturing process of the fluororesin bellows of uniform thickness in accordance with the present invention in each step, the fluororesin bellows blow manufacturing process according to the present invention is as follows.

Step 1: First flaring one end of the tube 31 by placing the tube 31 of the cylindrical fluorine resin produced through the primary manufacturing process in the auxiliary die 33 and pressurizing the upper end with a constant pressure (one end of the tube Machine the part so as to be perpendicular to the center part (FIG. 7A).

In this step, the temperature and pressure conditions are selected according to the physical properties of the fluorine resin to be molded, the auxiliary die 33 is heated to about 200 to 300 ℃, the tube 31 at a pressure of about 15 to 50 kg / ㎠ Pressurize.

Step 2: With the flared end of the tube 31 positioned on the surface of the upper die 21 of the apparatus, the upper core mold 22 and the plurality of intermediate core molds 23 on the outside of the tube 31. ) Are sequentially assembled, and finally the lower core mold 22 is positioned (FIG. 7B).

In this step, the support means 32 is inserted to maintain a constant gap between the plurality of core molds 22 and 23, and uses a material which does not cause deformation to the pressure applied. Preferably, the same material as the material for producing the core molds 22 and 23 can be used.

In addition, the elastic means 26 is positioned between the core molds 22 and 23 by receiving one end of the elastic means 26 in the elastic means accommodating portion formed on the surface of each core mold 22 and 23, respectively.

Step 3: After joining the lower die 24 with one end of the flared tube 31 in the inner space of each core mold 22 and 23, the other end of the unflared end of the tube 31 is lowered. Pressurization using the die 24 (FIG. 7C).

The temperature and pressure conditions in this step of flaring the end of the tube are the same as the temperature and pressure conditions in step 1 above.

Step 4: After injecting 1 to 8 kg / cm 2 of compressed air into the tube 31 to maintain a constant gap formed between each of the core molds 22 and 23, and placed between each core mold (22 and 23) Remove the supporting means 32 (as shown in FIG. 7D, which is also shown in this figure without the supporting means 32 for convenience).

In this step, if the pressure supplied into the tube 31 is lower than the above range, each core mold 22 and 23 cannot maintain a constant interval, and conversely, if the pressure is high, the tube 31 may be damaged. .

Step 5: After the upper and lower dies 21 and 24 and each core die 22 and 23 are housed in the housing 25, the pressure in the tube 31 is reduced to atmospheric pressure (FIG. 7E).

Step 6: After reducing the pressure in the tube 31, the mold apparatus is heated using conventional heating means (FIG. 7F). As a heating means used for blow molding of the fluororesin, an electric furnace can be preferably used.

The heating temperature and the heating time in this step can be changed according to the physical properties such as melting index and melting point of the fluorine resin used, and the heating time can be reduced as the heating temperature is increased. The heating temperature is preferably in the range of the melting point of the fluorine resin to be molded, that is, 320 to 385 ° C, and the preferred heating time is 80 to 140 minutes.

If the heating temperature is too low or the heating time is too short, the fluidity of the resin becomes low, the resin may not expand properly, and product abnormalities may occur. If the heating temperature is too high or the heating time is too long, the fluidity of the resin may increase. The tube shape of the resin may collapse and molding may not be possible.

Step 7: After transferring the mold apparatus of step 6 to the pressurizing apparatus, pressure is applied to the mold apparatus, and air is supplied into the tube to preform the tube in the form of bellows (FIG. 7G).

When one end of the mold apparatus, i.e., the upper die 21 is pressed, the elastic means 26 is compressed and all core molds are brought into close contact to form a bellows cavity of a desired shape. At this time, since the tube 31 located inside the core mold may also be twisted under pressure in the longitudinal direction, it is advantageous to expand the tube 31 preliminarily to maintain a uniform thickness of the wrinkle part. Therefore, before pressurizing one end of the mold apparatus, a constant air pressure is applied to the tube 31 to inflate the tube 31 preliminarily. Preferably the mold pressing force in this step is 40 to 60kg / ㎠ and the air pressure is 0.2 to 3kg / ㎠.

Step 8: When the predetermined value applied to the mold apparatus is reached, the pressure of the air supplied into the tube 31 is increased to expand the tube 31 to be in close contact with the surface of each core mold (FIG. 7H). At this time, the pressure of the air to be supplied is preferably 10 to 20 kg / cm 2. By the end of this step the tube has a bellows shape.

Step 9: After step 8 is finished, the mold is cooled while maintaining pressure on the mold, after which the mold is dismantled to take out the final bellows product. FIG. 7I is a partial cross-sectional view of the final bellows in which the blow molding process is completed. FIG.

On the other hand, in the present process, a preferred cooling method may use a water cooling method for passing low temperature water into or out of the mold.

In each step described above, the apparatus for pressurizing the mold may use a conventional pressurization apparatus, preferably a hydraulic press such as hydraulic pressure, hydraulic pressure, pneumatic press, or the like.

The present invention described as described above relates to a fluorine resin bellows having a uniform thickness of a wrinkle part, a manufacturing apparatus thereof, and a manufacturing method thereof, and accordingly, the present invention has the following effects.

First, since the thickness of the wrinkle part of the fluororesin bellows of the present invention is uniform, the durability of the product can be improved and the usage cycle can be grasped.

Second, since the core mold constituting the mold apparatus is divided, it is not necessary to manufacture the mold separately according to the specifications of each product, thereby reducing the mold cost.

Third, by simply adding or subtracting the split core mold, it is possible to produce a variety of products, thereby eliminating the inconvenience of replacing the entire mold according to the product, thereby simplifying the production process.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Figure 1a is a partial cross-sectional view of the conventional blow molded fluorine resin bellows folds.

Figure 1b is a partial cross-sectional view of the blow molded fluorine resin bellows wrinkles in accordance with an embodiment of the present invention.

2 is a cross-sectional view of a conventional mold for blow molding of the fluororesin bellows.

3 is a cross-sectional view of a mold apparatus for blow molding of a fluororesin bellows according to an embodiment of the present invention.

4A is a cross sectional view of the upper die shown in FIG. 3;

4B is a cross sectional view of the lower die with the air inlet shown in FIG. 3;

5 is a plan view of the upper and lower core molds.

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6A is a cross-sectional view of any one of the split intermediate core molds shown in FIG. 3.

6B is a front view of the split intermediate core mold shown in FIG. 6A.

7 is a view showing each step of the manufacturing process of the fluororesin bellows having a uniform thickness, according to the present invention.

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Claims (11)

In the bellows manufacturing apparatus for blow molding a fluororesin bellows, Cylindrical housing 25; An upper die 21 positioned at an upper end of the housing; A lower die 24 positioned at a lower end of the housing and having an air inlet 24a formed therein; Upper and lower core molds 22 housed in the housing 25 in contact with inner surfaces of the lower die 21 and the upper die 24, respectively; A plurality of intermediate core molds 23 disposed between the upper core mold and the lower core mold 22, the diameters of the upper end portion and the lower end portion being larger than the diameter of the center portion; And Many located between the upper core mold 22 and the intermediate core mold 23, between the intermediate core mold 23 and the intermediate core mold 23, and between the intermediate core mold 23 and the lower core mold 22. Bellows manufacturing apparatus characterized in that it comprises a resilient means (26). 2. The upper die 21 and the lower die 24 have a plurality of through holes 21b and 24b formed therein, and a plurality of tabs on the upper and lower core mold 22 surface portions in contact therewith. 22b is formed to allow the bolt to pass through the through holes 21b and 24b, and then into the tab 22b to accommodate the upper die 21, the upper core mold 22, and the lower die 24. And lower core mold (22) is integrated. The upper die 21 and the lower die 24 are provided with the flared portions of the tube 31 of the fluororesin in contact with the flared portions of the fluororesin tube 31. Bellows manufacturing apparatus, characterized in that the grooves (21c, 24c) for. 2. The upper and lower core molds 22 and the plurality of intermediate core molds 23 are formed with a plurality of grooves for accommodating one end of each elastic means in contact surfaces in contact with adjacent other core molds. Bellows manufacturing apparatus characterized in that. The upper and lower core molds 22 and the plurality of intermediate core molds 23 are made up of two symmetrical members which can be joined to take out the molded bellows. Bellows manufacturing apparatus to use. (A) mounting one end of the flared tube of fluororesin to the mold apparatus, and flaring another end; (B) heating the mold apparatus; (C) compressing the mold apparatus by injecting low pressure compressed air into the tube 31 through the air inlet of the lower die and then pressing one end of the mold apparatus; (D) inflating the tube 31 to the mold surface by injecting high pressure compressed air into the tube 31 while the mold apparatus is compressed; And (E) cooling the mold apparatus and then dismantling the mold apparatus. The method of claim 6, wherein the mold apparatus Cylindrical housing 25; An upper die 21 positioned at an upper end of the housing; A lower die 24 positioned at a lower end of the housing and having an air inlet 24a formed therein; Upper and lower core molds 22 housed in the housing 25 in contact with inner surfaces of the lower die 21 and the upper die 24, respectively; A plurality of intermediate core molds 23 disposed between the upper core mold and the lower core mold 22, the diameters of the upper end portion and the lower end portion being larger than the diameter of the center portion; And Many located between the upper core mold 22 and the intermediate core mold 23, between the intermediate core mold 23 and the intermediate core mold 23, and between the intermediate core mold 23 and the lower core mold 22. Bellows manufacturing method characterized in that it comprises a resilient means (26). The method of claim 6, wherein the step (a), Flaring one end of the tube of fluororesin 31; One end flared tube 31, the upper die 21 of the mold apparatus and the plurality of core molds 22, 23 are sequentially assembled, and then the support means 32 between the core molds 22, 23. And positioning the elastic means 26; Coupling the lower die 24 in a state in which one end of the flared tube 31 is accommodated in each of the mold internal spaces, and pressurizing to flaring the other end of the tube 31; Injecting 1 to 8 kg / cm 2 of compressed air into the tube (31), then removing the support means (32); And And after receiving each of the molds in the housing (25), reducing the pressure in the tube (31) to atmospheric pressure. The method of claim 6, wherein the heating temperature in the step (b) is 320 to 385 ° C and the heating time is 80 to 140 minutes, the pressure applied to the mold in the step (c) is 40 to 60 kg / ㎠, air pressure Is 0.2 to 3 kg / cm 2, and the pressure of the compressed air in the step (d) is 10 to 20 kg / cm 2. delete delete