JPH1157936A - Molding sand removing method for vaccum molding process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a mold for vacuum molding process having flat upper surface without causing sand inclusion defect by packing molding sand into a suction molding flask on a pattern plate, scraping this surface and blowing the compressed air after suction-reducing the pressure and hardening, to remove the remained molding sand on the upper ends of a sprue rod and a venting hole rod. SOLUTION: A molding film 6 is sucked and closely adhered on the patthen plate 10 provided with the sprue rod 1, pattern 2 and venting hole rod 3, through a suction hole 4 and fine holes 5, etc. Successively, the suction molding flask 20 is set in the pattern plate 10 and in the inner part thereof, the molding sand S is filled at higher than the heights of the sprue rod 1 and the venting hole rod 3, and this upper surface is horizontally leveled with a scraper. Further, in the molding sand S, the suction for reducing the pressure is executed from a suction tube 23 through hollow chamber 21 in the suction molding flask 20 and filter pipes 22 communicating with the hollow chamber to reduce the pressure and harden the upper surface part thereof. In this condition, the molding sand S remaining at the upper ends of the sprue rod 1 and the venting hole rod 3, is blown off and removed with the conpressed air from air blowing nozzles 30. Thereafter, the molding sand S in the suction molding flask 20 is further reduced to the pressure and hardened, and the pattern is removed to obtain the mold for vaccum molding process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a vacuum mold (so-called V
The present invention relates to a method for removing casting sand remaining on a molding film at the upper end of a sprue bar and a vent hole bar when molding a mold.

[0002]

2. Description of the Related Art Conventionally, when a hanging dam is used for pouring a molten metal into a vacuum mold, the flatness of molding sand on the upper surface of a suction casting frame is set to set the hanging dam. As described above, in order to obtain the flatness of the casting sand on the upper surface of the suction casting frame, the upper portion of the casting frame is generally scraped with a scraper, but when using a sprue bar and a vent hole bar, the molding is closely adhered. The height of the sprue bar and the vent hole bar is adjusted so that the height of the sprue bar and the vent hole bar is lower by 1 to 2 mm from the upper surface of the suction flask. From the above, even when the scraper is used to level the sand in the molding of the vacuum mold, a small amount of molding sand remains on the upper portion of the formed film at the upper ends of the gate and the vent hole. If the casting sand is left as it is, it falls into a mold cavity formed later and causes casting defects, so that the casting sand needs to be completely removed. From the above, the removal of the casting sand left on the molded film at the upper end of the gate and the vent hole bar is performed by brush cleaning of an operator, and this operation is scraped and leveled horizontally. It was necessary to carefully perform the process so as not to cause irregularities on the upper surface of the casting sand and adversely affect the setting of the hanging weir.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the casting sand left on the molding film at the upper end of the gate and the vent hole is leveled horizontally by scraping. It is an object of the present invention to provide a method for removing molding sand in a vacuum mold molding that reliably removes the molding sand without adversely affecting the upper surface.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is directed to a method in which a suction mold is placed on a model plate provided with a sprue bar and a vent hole bar on which a molded film is suction-contacted. Then, the top of the suction casting flask is scraped and the top of the casting sand is leveled by horizontal scraping, and the casting sand remaining on the top of the molding film at the upper end of the gate and the vent hole is removed. The upper surface is sealed with a seal film, and the pressure in the suction casting frame is reduced to solidify the casting sand under reduced pressure. After that, the molding film is left on the suction casting frame side, and the model plate is removed from the suction casting frame to form a mold. A method for removing molding sand in a mold making method, wherein after scraping the upper surface of the suction molding frame to level the upper surface of the molding sand horizontally, the inside of the suction molding frame is suction-reduced to solidify the molding sand under reduced pressure; Bars and vents Left on top of molded film at rod top Is characterized in that consists of the steps of removing the template sand by blowing compressed air against the sand.

[0005]

Embodiments of the present invention will be described below in detail with reference to the drawings. The box-shaped model plate 10
On the upper surface thereof, a sprue bar 1, a model 2, and a vent hole bar 3 provided on the upper portion of the model 2 are attached. Apply a reduced pressure suction to the surface to form a molded film 6
Is adhered by suction. A suction casting frame 20 is placed on the model plate 10 on which the formed film 6 is brought into close contact with suction, and casting sand S is put into a space defined by the model plate 10 and the suction casting frame 20. . The suction casting frame 20 has a hollow chamber 21 inside the side wall, and a filter pipe 22 communicating with the hollow chamber 21.
Is disposed at an upper position, and the hollow chamber 21 is connected to a vacuum source via a suction pipe 23 and an opening / closing valve (not shown). The upper ends of the sprue bar 1 and the vent hole bar 3 are lower than the upper end surface of the suction casting frame 20 by 1 to 2 mm. In this state, the upper surface of the suction casting frame 20 is scraped by a scraper (not shown), and the upper surface of the casting sand S is leveled horizontally. At this time, since the upper ends of the gate bar 1 and the vent hole bar 3 are lower than the height of the suction casting frame 20 by 1 to 2 mm, more casting sand S remains on the forming film 6.

Next, the on-off valve (not shown) provided on the suction pipe 23 is opened to reduce the pressure in the suction casting frame 20 through the filter pipe 22, and the upper surface of the casting sand S is reduced and solidified. Next, the air blow nozzles 30, 30 corresponding to the gate bar 1 and the vent bar 3 are lowered to the state shown in FIG. 1, and the top of the formed film 6 at the upper ends of the gate bar 1 and the vent bar 3 is blown by compressed air. The sand S is blown off and removed. At this time, since the upper surface of the casting sand S in the suction casting frame 20 is in a depressurized and solidified state, the casting sand S is maintained in a horizontal state without being blown off by the blowing compressed air. Is blown away.

Next, the air blow nozzles 30 are raised, and at the same time, the upper surface of the suction casting frame 20 (the upper surface of the casting sand S) is covered with a seal film. The molding sand S in the suction casting frame 20 adhered to the upper surface is further solidified under reduced pressure. Thereafter, the suction on the model plate 10 side is stopped in the same manner as in the normal molding of the reduced pressure mold, and the model film 10 is left on the suction casting frame 20 side (the lower surface of the casting sand S).
From the suction casting frame 20 to complete the molding of the reduced pressure mold. The depressurized mold molded in this way is used for pouring, so that the upper surface on which the hanging weir is set is maintained in a horizontal state without being uneven, so that there is no leakage of hot water. It is set in a stable state without any gaps, and there is no sand biting defect due to mixing of casting sand during pouring.

[0008]

As is apparent from the above description, the present invention scrapes the upper surface of the suction casting flask to level the upper surface of the molding sand horizontally, and then sucks and reduces the pressure in the suction molding flask to solidify the molding sand under reduced pressure. Compressed air is blown against the molding sand remaining on the molding film at the upper end of the gate bar and the ventilation hole bar to blow off and remove the molding sand, so that the upper surface of the leveling sand is leveled. It is possible to remove the molding sand automatically without causing any adverse effects on the setting of the hanging weirs used for pouring, and also has an excellent effect such as the prevention of sand biting defects due to the mixing of molding sand.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate gate 3 Vent rod 6 Molded film 10 Model plate 20 Suction casting frame 30 Air blow nozzle S Cast sand

Claims (1)

[Claims] 1. A suction casting flask is placed and set on a model plate provided with a sprue bar and a vent hole bar on which a molding film is suctioned and adhered to the surface, casting sand is charged, and the upper surface of the suction casting flask is scraped. The casting sand upper surface is leveled horizontally, the casting sand remaining on the upper surface of the molding film at the upper end of the gate and the vent hole bar is removed, and the casting sand upper surface is sealed with a seal film and the pressure in the suction casting frame is reduced. A method for removing sand from a suction mold in a vacuum mold making method, in which the molding film is removed from the suction mold while leaving the forming film on the suction mold after solidifying the molding sand under reduced pressure. After the top surface of the casting sand is leveled by horizontal scraping, the pressure in the suction casting frame is reduced by suction, and the casting sand is decompressed and solidified. Removing compressed sand by blowing compressed air to And a method for removing molding sand in reduced pressure mold molding.