Process for washing molding die for cold box process and...

Details Process for washing molding die for cold box process and... Process for washing molding die for cold box process and...

1998-11-25

2001-04-24

Lin, Kuang Y. (Department: 1722)

Metal founding

Process

Shaping liquid metal against a forming surface

C164S158000, C134S102200, C134S107000

Reexamination Certificate

active

06220334

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for washing a molding die for preparing a casting die (or core), and an apparatus therefor. In particular, the casting die (or core) is prepared by a cold box process.
2. Description of the Related Art
In a cold box process, a mixture of a phenol resin composition and a polisocyanate is compounded with a casting silica sand to prepare a casting sand. The resulting casting sand is filled in a molding die. Then, a TEA (i.e., triethylamine) gas is introduced into the molding die. Accordingly, a polyurethane resin arises to work as a bonding agent. The bonding agent can be cared at an ordinary temperature. Thus, a casting die (or core) can be prepared precisely in accordance with a cavity of the molding die. After molding the casting die by the cold box process, the bonding agent and silica sand reside on a molding surface and in a vent hole. The molding surface forms the cavity, and the vent holes are opened in the molding surface. Consequently, it is necessary to remove the bonding agent and silica sand when another high-quality casting die should be molded by reusing the molding die.
Conventionally, the following 3 washing processes have been employed to wash the molding die:
(a) brushing the molding die with a metallic brush together with an organic solvent;
(b) blowing the molding die with highly pressurized air together with an organic solvent; and
(c) blowing the molding die with shot particles made from glass or stainless steel, or with sand.
However, it is difficult to remove the bonding agent and silica sand from the molding die by the aforementioned conventional washing processes. Especially, it is difficult to remove them from narrow or congested areas. Accordingly, it is necessary to manually carry out the washing operation by an operator. In addition, it is needed to frequently carry out the removing operation, and it is inevitable that the time required for the operation should be prolonged. Moreover, even if an organic solvent is used in the conventional washing processes, the organic solvent might adversely affect ejector pins, etc., of the molding die, depending on the types of the organic solvent employed.
In particular, the vent hole cannot be processed effectively by the first and second conventional washing processes (a) and (b). Even if the vent holes are processed by the third convention al washing process (c), the molding surface around the vent hole might be damaged, and a mesh, which is usually provided for the vent hole, might be damaged. Moreover, the mesh might make it difficult to recover the glass particles, etc. Consequently, the mesh, etc., should be replaced with new ones regularly under the current circumstances.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the aforementioned circumstances. It is therefor e an object of the present invention to provide a process and an apparatus for washing a molding die for a cold box process easily and fully.
The invent ors of the present invention ma de research and development extensively in order to achieve the object. First of all, they started investigating the chemical processes (1) through (21) as listed in Table 1 through Table 1 (sexies) below, and the physical processes (22) through (31) as listed in Table 2 through Table 2 (quarter) below.
TABLE 1
Chemical Washing
Water Soluble Washing Agent
 (1)
Pure Water or Ultra-pure Water
 (2)
Alkali Aqueous Solution
 (3)
Surfactant Aqueous Solution
 (4)
Surfactant/Alkali Combined Aqueous Solution
 (5)
Surfactant/Organic Solvent Combined Aqueous
Solution
TABLE 1 (bis)
Chemical Washing
Organic Solvent Washing Agent
 (6)
Chlorinated Solvent
 (7)
Hydrocarbon-based Solvent
 (8)
Silicone-based Solvent
 (9)
Alcohol-based Solvent
TABLE 1 (ter)
Chemical Washing
Washing Mode
(10)
Electrolysis Washing with Alkali Aqueous
Solution
(11)
Ultrasonic Washing
(12)
Rotary Brush Washing
(13)
Immersion-oscillation Washing
(14)
Spraying Washing
(15)
Bubbling Washing
TABLE 1 (quater)
Heating
Conduction Heat
(16)
Combustion Mode
(17)
Steam Mode
TABLE 1 (quiquies)
Heating
Radiation Heat
(18)
UV Light Mode
(19)
Plasma Mode
TABLE 1 (sexies)
Chemical Reaction
Oxidation
(20)
Dry Ozone Oxidation Mode
(21)
Wet Ozone Oxidation Mode
TABLE 2
Physical Washing by Shots
Permanent Solid
(22)
Sand
(23)
Plastic Particles
(23)
Glass Particles
(24)
Stainless Steel Particles
TABLE 2 (bis)
Physical Washing by Shots
Disappearing Substance
(26)
Dry Ice
(27)
Air
TABLE 2 (ter)
Physical Washing by Shots
Water-related Substance
(28)
Ice
(29)
Highly-pressurized Water
TABLE 2 (quater)
Physical Washing by Brush
Washing Mode
(30)
Jet-like-propelled Chisel
(31)
Electromotive Brush
Chemical processes (1) through (21), and physical processes (22) through (31) were evaluated in terms of quality, difficulty, washability, cost and safety. They were graded as “Excellent”, “Good”, “Fair” or “Poor” for the characteristics, and were rated in terms of overall performance as well. Note that, in the evaluation, the quality was determined based on the presence of abrasion, etc., on a molding surface of a molding die, and the quality resulted in the superiority or inferiority of a resulting casting die. The casting die was prepared herein by the molding die which had been subjected to the washing processes. Table 3 below summarizes the results of the evaluation on the chemical processes (1) through (21). Table 4 below summarizes the results of the evaluation on the physical processes (22) through (31).
TABLE 3
Over-
all
Eval-
ua-
Quality
Difficulty
Washability
Cost
Safety
tion
 (1)
Fair
Excellent
Poor
Excellent
Excellent
Fair
 (2)
Fair
Excellent
Good
Good
Fair
Good
 (3)
Fair
Good
Fair
Good
Good
Fair
 (4)
Fair
Good
Fair
Fair
Fair
Fair
 (5)
Good
Good
Good
Fair
Fair
Fair
 (6)
Poor
Good
Good
Fair
Poor
Fair
 (7)
Good
Good
Good
Fair
Fair
Good
 (8)
Good
Good
Fair
Poor
Fair
Poor
 (9)
Good
Good
Fair
Fair
Fair
Fair
(10)
Fair
Fair
Fair
Fair
Fair
Fair
(11)
Good
Good
Good
Poor
Good
Good
(12)
Fair
Fair
Fair
Poor
Fair
Poor
(13)
Good
Good
Fair
Fair
Fair
Good
(14)
Good
Good
Fair
Fair
Fair
Good
(15)
Good
Good
Fair
Fair
Good
Good
(16)
Poor
Excellent
Excellent
Good
Poor
Poor
(17)
Fair
Excellent
Fair
Good
Good
Good
(18)
Fair
Good
Fair
Poor
Fair
Fair
(19)
Poor
Fair
Poor
Poor
Poor
Poor
(20)
Good
Fair
Fair
Poor
Poor
Fair
(21)
Fair
Fair
Good
Poor
Poor
Fair
TABLE 4
Over-
all
Eval-
ua-
Quality
Difficulty
Washability
Cost
Safety
tion
(22)
Poor
Excellent
Good
Good
Fair
Fair
(23)
Poor
Good
Poor
Poor
Good
Poor
(24)
Fair
Fair
Fair
Fair
Good
Fair
(25)
Poor
Good
Fair
Good
Good
Fair
(26)
Excellent
Fair
Good
Fair
Good
Good
(27)
Good
Excellent
Poor
Fair
Good
Fair
(28)
Poor
Poor
Good
Good
Good
Fair
(29)
Fair
Good
Fair
Good
Good
Good
(30)
Poor
Fair
Fair
Good
Good
Fair
(31)
Poor
Fair
Fair
Good
Good
Fair
In physical process (26), the dry ice was blown to the molding surface at a high pressure. Physical process (26) was graded as “Excellent”, because no problem arose in the molding surface. However, the mesh provided for the vent hole were damaged, and should be replaced with a new one.
Further, in order to investigate the washing agent in detail, the inventors of the present invention examined a washing agent “TOYOKNOCK” produced by TOYOTA KAGAKU KOGYO CO., LTD. The washing agent worked as an alkali aqueous washing liquid. Furthermore, the present inventors examined hexane, toluene, dichloromethane, heptane, methanol and acetone. The hexane and heptane worked as a paraffin-based organic solvent. The toluene worked as an aromatic organic solvent. The dichloromethane worked as a chlorinated hydrocarbon organic solvent. The methanol worked as an alcohol-based organic solvent. The acetone worked as a ketone-based organic solvent. Among the aforementioned organic solvents, the hexane showed somewhat satisfactory results in terms of the washing ability for the molding surface when it is pressurized to a pressure exerted by an ordinary shower. However, the h

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