US3506061A - Apparatus for vacuum-casting a plurality of metal parts in a single mold - Google Patents

Apparatus for vacuum-casting a plurality of metal parts in a single mold Download PDF

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Publication number
US3506061A
US3506061A US462835A US3506061DA US3506061A US 3506061 A US3506061 A US 3506061A US 462835 A US462835 A US 462835A US 3506061D A US3506061D A US 3506061DA US 3506061 A US3506061 A US 3506061A
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Prior art keywords
metal
mold
cores
cavities
gates
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Expired - Lifetime
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US462835A
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English (en)
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Peter J Clemm
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General Electric Co
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General Electric Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum

Definitions

  • the molding apparatus that I am concerned with comprises a plurality of cores disposed in stacked relationship and containing recesses defining cavities of a shape conforming to that of the parts being cast.
  • These cores are made from a high strength material, such as graphite, that allows the cores to be reused for many repeated casting operations.
  • the mold is referred to herein as a permanent mold.
  • the casting operation it is important that the casting operation not impose damaging stresses on the cores, and it is also important that the cast parts be removable from the mold without damaging the cores. It is, of course, just as important that the cast parts themselves not be damaged either by the casting operation or by their removal from the mold.
  • An object of the present invention is to prevent the stresses produced by such differential contraction from damaging either the cast parts or the cores.
  • Another object is to construct the mold in such a manner that the cast parts can easily be removed without imposing damaging stresses on either the cast parts or the cores.
  • I provide a mold assembly in which separable, reusable cores are disposed in stacked relationship with the above-described cavities located between adjacent cores.
  • a reservoir, or entry region, for molten metal is disposed adjacent one end of the mold assembly, and molten metal is fed from this reservoir into the cavities.
  • the cavities are interconnected by gates of small cross section that provide passageways between the cavities through which molten metal flows from the reservoir into the cavities to successively fill the cavities,
  • the interior of the mold is maintained under a vacuum while the cavities are being filled, and thus there is no air or other gas present to interfere with filling the cavities through the small gates.
  • the cast parts are removed from the mold. This removal is effected by fracturing the metal in the small cross-section gates between adjacent cast parts, each such fracture permitting removal of one of the cast parts and an adjacent core. This fracture is produced by a predetermined separating force applied either to the cast part being separated or to the core between the adjacent cast parts.
  • the cross-sectional area of the metal in the gate is sufiiciently small that said predetermined separating force fractures the gate metal before it produces damaging stresses elsewhere, either in the cast part being removed or the immediately adjacent core.
  • FIG. 1 is a cross-sectional view through a mold assembly embodying one form of the invention
  • FIG. 2 is a sectional view taken along the line 22 of FIG. 1;
  • FIG. 3 is a diagrammatic view illustrating the general manner in which the mold and cast parts cool after the mold-filling operation.
  • FIG. 4 is a sectional view of a portion of a slightly modified mold assembly.
  • a mold assembly 10 comprising a plurality of cores 12 disposed in vertically-stacked relationship.
  • Each of these cores 12 has a recess 14 in one or both of its horizontally-disposed faces, and this recess 14 together with a recess 14 on an adjacent core 12 defines a cavity 16 of a shape conforming to that of the part to be cast.
  • the lowermost core 12 is imperforate, but each of the other cores includes a centrally-located passage, or gate, 20 extending vertically therethrough. These gates 20 are preferably disposed in aligned relationship along an axis 21 that is centrally located with respect to the cavities.
  • Each of the illustrated cores 12, except the top one is of a disk shape with a circular outer periphery.
  • the top core 12 may be thought of as being cup-shaped with a circular outer periphery. The circular outer peripheries of all the cores are in alignment.
  • the top core 12 forms a reservoir, or entry region, 22 for molten metal that is fed downwardly through the gates 20* to fill the cavities 16, as will soon be described in more detail.
  • a jacket 24 of cup-form Surrounding all the cores 12 is a jacket 24 of cup-form that has a cylindrical portion 25 with internal threads 26 that mate with external threads on the top core 12. When these threads are tightened by suitably rotating the jacket 24 relative to the upper core 12, the lower wall 27 of the jacket 24 engages the lower core 12 and clamps all the cores together.
  • Each of the illustrated cores 12 has a planar surface 28 that engages a corresponding planar surface on the adjacent core or cores to provide a good seal between these parts when the cores are clamped together by rotation of the outer jacket 28.
  • These planar surfaces are referred to as the parting surfaces of the cores. In the illustrated mold assembly, these parting surfaces 28 extend substantially perpendicular to the central axis 21. If desired, the parting surfaces of adjacent cores may be of a conical form or some other form capable of providing a good seal therebetween at the outer periphery of the cavity 16 to prevent the escape of molten metal from the cavity.
  • the heat used during the casting operation can be derived from any suitable source, but I prefer to use an induction coil 32 that surrounds the entire mold assembly. When this coil is appropriately energized, it heats the mold assembly to the desired temperature.
  • a first step in the casting operation is to place a charge of solid copper in the reservoir 22 at the top of the mold.
  • This copper has been suitably pre-treated to free it of all but a tiny part of its sor-bed gases.
  • the whole mold assembly together with the copper charge is heated by the coil 32 while under vacuum. As the copper melts, it is fed by gravity through the gates 20 and into the cavities 16. The lowermost cavity 16 is first filled, followed by successively higher cavities.
  • the illustrated mold assembly for making precision castings that have a high freedom from included gases. It will be assumed that the castings are to be made of copper, though it should be understood that many other metals are equally usable.
  • the cores 12 and the jacket 24 of the mold assembly are preferably made of a high purity graphite.
  • the mold assembly is heated to a high temperature, e.g., between 1,000 and 2,000 degrees F., while in a high vacuum.
  • This heating in a vacuum drives off most of the gases from the walls of the mold, thus assuring that these gases will not find their way into the castings during the casting operation.
  • a high vacuum is also maintained immediately before and during the casting operation, and this allows the cavities 16 and gates 20 to be completely filled with molten metal without any interference from gases. While I prefer to provide a vacuum in which the pressure is 10 mm. of mercury or lower, many of the advantages mentioned hereinafter can be realized with lesser degrees of vacuum, e.g.
  • vacuum as used herein is intended to denote a pressure below several millimeters of mercury.
  • I employ a very high vacuum, primarily because I wish to maintain the cast parts substantially free of internal gases.
  • the desired vacuum is obtained, preferably, by locating the mold assembly in an evacuated chamber (not shown) provided with a suitable vacuum pump that holds the pressure in the chamber at the desired low level.
  • the gates 20 have a very small cross section.
  • the vacuum environment makes it feasible to rely upon the small gate cross-section since there is no gas present inside the mold to inhibit flow through the gates and no need to provide for gas escape therethrough, as would usually be the case with casting in air.
  • each of the gates can be of a uniform cross section, but in the preferred form of the invention illustrated, each of the gates has a single restricted portion 40 intermediate its ends.
  • this restricted portion has a diameter of about 5 inch.
  • the gate diameter gradually increases to about .275 inch.
  • Gates of substantially this same size and shape can be used whether the casting metal is copper or some other metal.
  • FIG. 3 illustrates with the dotted lines A, B, C and D successive positions that the freezing front passes through as the temperature drops. It will be noted from this figure that the freezing front passes upwardly and radially inwardly, passing through successive positions A, B, C, and D as the temperature drops.
  • the mold assembly is positioned with its bottom portion contacting a base (not shown) that is cooled at a suitable rate, preferably from outside the evacuated chamber in which the mold is located.
  • suitable thermal insulation can be provided about the jacket to control the cooling pattern.
  • I By maintaining the assembly at a high temperature during the entire filling operation, I maintain the metal in each of the gates in a molten state until all the cavities being fed through it have filled. This insures that there will be no premature freezing in the gates that could interfere with filling cavities therethrough.
  • I By cooling in the general manner illustrated, I maintain a centrallylocated head of molten metal in communication with the still-molten metal in each cavity until substantially all the metal in the cavity freezes. This permits metal to be fed through the gates from points above the still-molten metal to maintain the cavities filled despite the tendency of the cooling metal to shrink at a greater rate than the graphite of the mold.
  • the metal that was in the gates 20 is suitably detached from the cast parts and discarded. Any plastic deformation or shrinkage defects which may have occurred in the gates do not affect the quality of the cast parts, in view of this detachment of the gate metal from the cast parts.
  • the small cross section of the gate also serves in an important manner to provide for removal of the cast parts from the mold without damage to the mold or the cast parts. Such removal is effected after the casting op eration by first unscrewing the jacket 24 and then separating it from the mold assembly. This frees the bottom, or first, core 12 for removal. After the first core 12 is so removed, the second core 12 is suitably gripped at its outer periphery and a downward separating force is applied thereto. This fractures the metal in the lowermost gate 20 and separates the second core 12 and the casting in the lowermost cavity 16 from the other castings. This procedure is repeated, successively freeing each newly exposed core and casting from the assembly until finally all of the castings have been removed from the assembly.
  • each newly exposed casting can be freed from the assembly by applying a separating force directly to it instead of applying the force through the core 12 just above it.
  • the separating force can be either a twisting force or a force that loads the gate metal in tension, or a combination of these forces.
  • the metal in the gate being relatively weak due to its small cross section, fractures in response to the separating force before the stresses elsewhere produced by the separating force are high enough to damage either the casting or the core.
  • the cross-sectional area of the gate is purposely made small enough to impart this amount of weakness to the metal in the gate.
  • each of the cast parts in the illustrated apparatus has a diameter of about 2.7 inches and a minimum thickness of about inch.
  • Each of the cores has an outside diameter of about 3.5 inches and a minimum thickness of about inch.
  • the gates have a very small volume in comparison to that of the cavities, e.g., a few percent or less, and this contributes to a high casting yield with little scrap.,That is, only a few percent or less of the metal is scrapped when the gate metal is detached from the cast part and discarded after the cast parts are removed from the mold.
  • a further benefit of using the constricted gates is that, due to intimate contact between the graphite and the molten metal as the metal passes through the constrictions, a substantial percentage of the minute amount of oxygen remaining in the molten metal is extracted from the metal.
  • the castings are shown as being of circular disk form, it is to be understood that other more complex shapes can be produced, if desired, by suitably shaping the recesses that form the cavities 16. It is to be understood, of course, that by varying the number of cores the mold assembly can easily be adapted to accommodate fewer or more castings. By producing a large number of similar parts in a single mold assembly which is of a highly compact design, I can reduce the space, time, and equipment required for a given casting.
  • each of the cores illustrated in FIG. 1 is of a one-piece construction, it is to be understood that the cores can, if desired, be of two or more pieces of suitable form.
  • I show each core constructed of two pieces, 12a and 12b, with mating parting surfaces 29.
  • Each of the pieces 12a and 12b can, if desired, be considered as a core.
  • the cast parts can be removed from a mold of this construction in substantially the same manner as described hereinabove with respect to the embodiment of FIG. 1.
  • Permanent mold apparatus for vacuum-casting a plurality of metal parts comprising:
  • each of said cast parts being separable from its adjacent cast part after a predetermined separating force is applied either to the cast part being separated or to a core between adjacent cast parts
  • said gates being sufiiciently small in cross-section that the solid metal in a gate adjacent a cast part being separated has a breaking strength low enough to fracture in response to said predetermined separating force before the stresses elsewhere produced by said separating force are high enough to damage either said cast part or said adjacent core,
  • At least one of said gates has a constriction intermediate its longitudinally opposed ends, thereby providing at said constriction a relatively weak zone in the metal of said gate that is more susceptible than the rest of said gate metal to fracture by said separating force.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
US462835A 1965-06-10 1965-06-10 Apparatus for vacuum-casting a plurality of metal parts in a single mold Expired - Lifetime US3506061A (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3656539A (en) * 1969-01-29 1972-04-18 Amsted Ind Inc Apparatus for casting molten metal
US3841384A (en) * 1973-02-21 1974-10-15 Howmet Corp Method and apparatus for melting and casing metal
US3859703A (en) * 1971-12-09 1975-01-14 Hale Fire Pump Co Method for making a check valve for a pump
US3973750A (en) * 1972-10-06 1976-08-10 Office National D'etudes Et De Recherches Aerospatiales (O.N.E.R.A.) Casting mold for directional solidification of an alloy
US4008032A (en) * 1974-03-20 1977-02-15 Pahl Karl Heinz Device for the cyclic manufacture of molded parts
US4287936A (en) * 1978-11-16 1981-09-08 Ljublinsky Efim Y Ingot casting apparatus
US4345965A (en) * 1978-08-04 1982-08-24 Kloeckner-Werke Ag Method and apparatus for making two component mouldings
US4374635A (en) * 1978-04-17 1983-02-22 American Standard Inc. Casting installations
US4399859A (en) * 1980-11-13 1983-08-23 Ford Motor Company Diecasting assembly
US20040083609A1 (en) * 2002-11-04 2004-05-06 Malott Theodore A. Two-piece molded fan
US20130277007A1 (en) * 2012-04-20 2013-10-24 Fs Precision Tech Single piece casting of reactive alloys
CN118404006A (zh) * 2024-04-25 2024-07-30 无锡普金精密机械制造有限公司 一种增程器铝合金壳体的铝合金浇铸模具

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011011574B4 (de) * 2011-02-09 2015-04-02 Voith Patent Gmbh Verfahren zum Gießen eines Schaufelrads

Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US644425A (en) * 1899-02-04 1900-02-27 Joseph Wm Harrison Apparatus for casting metal.
US1070500A (en) * 1911-05-04 1913-08-19 David Stuart Mackenzie Dental casting apparatus.
US1162339A (en) * 1912-08-21 1915-11-30 Gen Electric Method of making composite metal bodies.
US1162340A (en) * 1912-03-20 1915-11-30 Gen Electric Method of uniting metals.
US1358435A (en) * 1918-10-01 1920-11-09 Harry S Frank Process of making multiple molds and castings
US1550718A (en) * 1923-03-14 1925-08-25 Earl Holley Piston-ring mold
DE544269C (de) * 1929-09-13 1932-04-26 Theodor Rudolf Pawlikowski Verfahren zur Herstellung von Gussformen fuer Kolbenringe
US2127239A (en) * 1935-12-11 1938-08-16 Stoody Co Means for producing high melting point alloy castings
US2548897A (en) * 1947-04-07 1951-04-17 William J Kroll Process for melting hafnium, zirconium, and titanium metals
US2555546A (en) * 1946-08-26 1951-06-05 Holly Mfg Company Gas furnace
US2567693A (en) * 1948-10-14 1951-09-11 Western Electric Co High-pressure nozzle
US2804664A (en) * 1955-09-06 1957-09-03 Joseph B Brennan Casting apparatus
US2940142A (en) * 1958-03-31 1960-06-14 Wells Mfg Company Mold assembly
FR1258736A (fr) * 1960-06-07 1961-04-14 Perfectionnements aux moules permettant de mouler simultanément plusieurs objets analogues
US3233294A (en) * 1962-02-07 1966-02-08 U S Magnet & Alloy Corp Method and apparatus for casting vertically stacked magnet bodies

Patent Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US644425A (en) * 1899-02-04 1900-02-27 Joseph Wm Harrison Apparatus for casting metal.
US1070500A (en) * 1911-05-04 1913-08-19 David Stuart Mackenzie Dental casting apparatus.
US1162340A (en) * 1912-03-20 1915-11-30 Gen Electric Method of uniting metals.
US1162339A (en) * 1912-08-21 1915-11-30 Gen Electric Method of making composite metal bodies.
US1358435A (en) * 1918-10-01 1920-11-09 Harry S Frank Process of making multiple molds and castings
US1550718A (en) * 1923-03-14 1925-08-25 Earl Holley Piston-ring mold
DE544269C (de) * 1929-09-13 1932-04-26 Theodor Rudolf Pawlikowski Verfahren zur Herstellung von Gussformen fuer Kolbenringe
US2127239A (en) * 1935-12-11 1938-08-16 Stoody Co Means for producing high melting point alloy castings
US2555546A (en) * 1946-08-26 1951-06-05 Holly Mfg Company Gas furnace
US2548897A (en) * 1947-04-07 1951-04-17 William J Kroll Process for melting hafnium, zirconium, and titanium metals
US2567693A (en) * 1948-10-14 1951-09-11 Western Electric Co High-pressure nozzle
US2804664A (en) * 1955-09-06 1957-09-03 Joseph B Brennan Casting apparatus
US2940142A (en) * 1958-03-31 1960-06-14 Wells Mfg Company Mold assembly
FR1258736A (fr) * 1960-06-07 1961-04-14 Perfectionnements aux moules permettant de mouler simultanément plusieurs objets analogues
US3233294A (en) * 1962-02-07 1966-02-08 U S Magnet & Alloy Corp Method and apparatus for casting vertically stacked magnet bodies

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3656539A (en) * 1969-01-29 1972-04-18 Amsted Ind Inc Apparatus for casting molten metal
US3859703A (en) * 1971-12-09 1975-01-14 Hale Fire Pump Co Method for making a check valve for a pump
US3973750A (en) * 1972-10-06 1976-08-10 Office National D'etudes Et De Recherches Aerospatiales (O.N.E.R.A.) Casting mold for directional solidification of an alloy
US3841384A (en) * 1973-02-21 1974-10-15 Howmet Corp Method and apparatus for melting and casing metal
US4008032A (en) * 1974-03-20 1977-02-15 Pahl Karl Heinz Device for the cyclic manufacture of molded parts
US4374635A (en) * 1978-04-17 1983-02-22 American Standard Inc. Casting installations
US4345965A (en) * 1978-08-04 1982-08-24 Kloeckner-Werke Ag Method and apparatus for making two component mouldings
US4287936A (en) * 1978-11-16 1981-09-08 Ljublinsky Efim Y Ingot casting apparatus
US4399859A (en) * 1980-11-13 1983-08-23 Ford Motor Company Diecasting assembly
US20040083609A1 (en) * 2002-11-04 2004-05-06 Malott Theodore A. Two-piece molded fan
US20130277007A1 (en) * 2012-04-20 2013-10-24 Fs Precision Tech Single piece casting of reactive alloys
CN118404006A (zh) * 2024-04-25 2024-07-30 无锡普金精密机械制造有限公司 一种增程器铝合金壳体的铝合金浇铸模具
CN118404006B (zh) * 2024-04-25 2025-04-22 无锡普金精密机械制造有限公司 一种增程器铝合金壳体的铝合金浇铸模具

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SE315984B (enrdf_load_html_response) 1969-10-13
GB1127708A (en) 1968-09-18

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