Mold assembly apparatus and method for molding metal articles

Abstract

Apparatus assemblies and methods for melting and injection molding an article from a meltable metal that is sensitive to heating by radio frequency (RF) induction. An exemplary apparatus includes a mold including a cavity having a shape of an article to be molded, a delivery chute including a channel for delivering a solid metal billet from a proximal end of the delivery chute to a distal end which is adjacent to the mold, and an RF induction heating coil that surrounds the cavity of the mold and the distal end of the delivery chute. Advantageously, the portion of the mold defining the cavity and at least the distal end of the delivery chute (i.e., those portions surrounded by the RF coil) are formed of materials that are substantially insensitive to heating by RF induction so that the metal billet is melted and molded at approximately the same time.

1 . An apparatus for melting and molding an article from a solid metal billet, comprising:
 a mold including a cavity having a shape of an article to be molded;   a delivery chute including a channel for delivering a solid metal billet from a proximal end to a distal end, the distal end being adjacent to the cavity of the mold, at least that portion of the mold defining the mold cavity and at least the distal end of the delivery chute being formed of a material that is substantially not sensitive to heating by RF induction; and   an RF induction heating coil surrounding the cavity of the mold and the distal end of the delivery chute.   
     
     
         2 . An apparatus as defined in  claim 1 , wherein at least the mold and distal end of the delivery chute are contained with a chamber under vacuum or an inert atmosphere. 
     
     
         3 . An apparatus as defined in  claim 1 , wherein the delivery chute further comprises at least one gate member for selectively allowing passage of a metal billet through the channel. 
     
     
         4 . An apparatus as defined in  claim 1 , further comprising a pressing member for selectively pressing a molten metal billet into the cavity. 
     
     
         5 . A apparatus as recited in  claim 4 , wherein the pressing member includes a contacting surface having a mesh, sawtooth, or textured pattern. 
     
     
         6 . An apparatus as defined in  claim 1 , wherein at least the portion of the mold defining the mold cavity is formed of ceramic. 
     
     
         7 . An apparatus as defined in  claim 1 , wherein at least the distal end of the delivery chute is formed of ceramic. 
     
     
         8 . A method of manufacturing a molded metal article, comprising:
 introducing a solid metal billet into a delivery chute having a channel leading to a molding cavity of a mold, at least that portion of the mold defining the cavity being formed of a material that is not sensitive to heating by RF induction;   selectively heating the metal billet by RF induction heating adjacent the mold cavity so as to melt the metal billet such that the metal fills the molding cavity without substantial heating of the mold;   allowing the metal within the molding cavity to cool so as to form a metal molded article; and   removing the metal article from the molding cavity.   
     
     
         9 . A method as recited in  claim 8 , wherein the volume of the metal billet is substantially equal to the volume of the mold cavity, the method further comprising maintaining the metal in a heated molten configuration until substantially all metal material has entered the molding cavity and the cavity is substantially filled. 
     
     
         10 . A method as recited in  claim 8 , wherein at least that portion of the mold defining the mold cavity is formed of ceramic. 
     
     
         11 . A method as recited in  claim 8 , wherein at least the distal end of the delivery chute is formed of a material that is insensitive to heating by RF induction. 
     
     
         12 . A method as recited in  claim 11 , wherein at least the distal end of the delivery chute is formed of ceramic. 
     
     
         13 . A method as recited in  claim 8 , wherein the metal billet comprises a zirconium based metallic amorphous alloy formed from low purity materials. 
     
     
         14 . A method as recited in  claim 13 , wherein the zirconium based metallic amorphous alloy comprises at least one of the compositions selected from the group consisting of (Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 ) 98 Y 2 , (Zr 34 Ti 15 Cu 12.5 Ni 11 Be 28 ) 98 Y 2 , Zr 34 Ti 15 Cu 12 Ni 11 Be 28 Y 2 , (Zr 34 Ti 15 Cu 12 Ni 11 Be 28 ) 98 Y 2 , (Zr 34 Ti 15 Cu 10 Ni 11 Be 22.5 ) 98 Y 2 , (Zr 55 Al 15 Ni 10 Cu 20 ) 98 Y 2 , and (Zr 55 Al 15 Ni 10 Cu 20 ) 96 Y 4 . 
     
     
         15 . A method as recited in  claim 8 , wherein the metal billet comprises at least one of iron, silver, or gold. 
     
     
         16 . A method as recited in  claim 8 , wherein the method is performed under vacuum or in an inert atmosphere. 
     
     
         17 . A method as recited in  claim 8 , further comprising pressing a surface of the metal within the mold cavity with a pressing member before the metal completely cools. 
     
     
         18 . A method as recited in  claim 17 , wherein the pressing member applies a mesh, sawtooth, or textured pattern to a surface of the metal within the mold cavity. 
     
     
         19 . A method as recited in  claim 8 , wherein RF induction heating of the metal billet melts the metal billet within about 5 seconds or less. 
     
     
         20 . A method as recited in  claim 8 , wherein RF induction heating of the metal billet melts the metal billet within about 1 second or less. 
     
     
         21 . An apparatus for melting and molding an article from a solid metal billet, comprising:
 a mold including a cavity having a shape of an article to be molded, at least that portion of the mold defining the cavity being formed of ceramic so as to be substantially not sensitive to heating by RF induction;   a delivery chute including a channel for delivering a metal billet from a proximal end to a distal end of the chute, the distal end being adjacent to the cavity of the mold, at least the distal end of the delivery chute being formed of ceramic so as to be substantially not sensitive to heating by RF induction;   an RF induction heating coil surrounding the cavity of the mold and the distal end of the ceramic delivery chute; and   a pressing member for selectively pressing a molten metal billet into the cavity.   
     
     
         22 . A method of manufacturing an orthodontic bracket from metal, comprising:
 selectively heating a metal billet by RF induction heating adjacent to a molding cavity defined by a mold, the cavity being in the shape of at least a portion of an orthodontic bracket so as to melt the metal billet such that substantially all of the metal enters the molding cavity and substantially fills the molding cavity, the mold being formed of a material that is substantially insensitive to heating by RF induction such that there is substantially no heating of the mold by RF induction;   allowing the metal within the molding cavity to cool so as to form a solid metal orthodontic bracket; and   removing the solid metal orthodontic bracket from the molding cavity.   
     
     
         23 . A method as recited in  claim 22 , wherein at least that portion of the mold defining the molding cavity is formed of ceramic. 
     
     
         24 . A method as recited in  claim 22 , wherein the metal billet comprises a zirconium based metallic amorphous alloy. 
     
     
         25 . A method as recited in  claim 24 , wherein the zirconium based amorphous metallic alloy is selected from the group consisting of (Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 ) 98 Y 2 , (Zr 34 Ti 15 Cu 12.5 Ni 11 Be 28 ) 98 Y 2 , Zr 34 Ti 15 Cu 12 Ni 11 Be 28 Y 2 , (Zr 34 Ti 15 Cu 12 Ni 11 Be 28 ) 98 Y 2 , (Zr 34 Ti 15 Cu 10 Ni 11 Be 22.5 ) 98 Y 2 , (Zr 55 Al 15 Ni 10 Cu 20 ) 98 Y 2 , and (Zr 55 Al 15 Ni 10 Cu 20 ) 96 Y 4 . 
     
     
         26 . A method as recited in  claim 22 , wherein the method is performed under vacuum and/or in an inert atmosphere. 
     
     
         27 . A method as recited in  claim 22 , wherein the molding cavity is configured such that the molten metal enters the molding cavity through an entrance portion of the molding cavity corresponding to a bonding pad of the orthodontic bracket. 
     
     
         28 . A method as recited in  claim 27 , further comprising pressing a surface of the metal within the molding cavity adjacent to the entrance with a pressing member before the metal completely cools. 
     
     
         29 . A method as recited in  claim 28 , wherein the pressing member applies a mesh, sawtooth, or textured pattern to a bonding pad surface of the orthodontic bracket. 
     
     
         30 . A method as recited in  claim 29 , further comprising bending the bonding pad surface of the orthodontic bracket subsequent to removing the metal orthodontic bracket from the molding cavity so as to, form a curved bonding pad with undercuts within the bonding pad surface. 
     
     
         31 . A method as recited in  claim 22 , wherein selective heating of the metal billet so as to melt the metal billet is accomplished substantially simultaneously with the metal entering the molding cavity. 
     
     
         32 . A method of manufacturing an orthodontic bracket from a zirconium based metallic amorphous alloy, comprising:
 selectively heating a metal billet of a zirconium based metallic amorphous alloy material by RF induction heating adjacent to a molding cavity defined by a mold, the cavity being in the shape of an orthodontic bracket so as to melt the metal billet, the metal billet having a volume substantially equal to a volume of the molding cavity such that substantially all of the metal enters the molding cavity and substantially fills the molding cavity, the mold being formed of a material that is substantially insensitive to heating by RF induction such that there is substantially no heating of the mold by RF induction;   allowing the metal within the molding cavity to cool so as to form a solid metal orthodontic bracket; and   removing the solid metal orthodontic bracket from the molding cavity;   wherein heating and molding of the orthodontic bracket is performed under vacuum.   
     
     
         33 . A method as recited in  claim 32 , wherein the zirconium based metallic amorphous alloy comprises at least one alloy selected from the group consisting of (Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 ) 98 Y 2 , (Zr 34 Ti 15 Cu 12.5 Ni 11 Be 28 ) 98 Y 2 , Zr 34 Ti 15 Cu 12 Ni 11 Be 28 Y 2 , (Zr 34 Ti 15 Cu 12 Ni 11 Be 28 ) 98 Y 2 , (Zr 34 Ti 15 Cu 10 Ni 11 Be 22.5 ) 98 Y 2 , (Zr 55 Al 15 Ni 10 Cu 20 ) 98 Y 2 , and (Zr 55 Al 15 Ni 10 Cu 20 ) 96 Y 4 . 
     
     
         34 . A method as recited in  claim 32 , wherein at least the portion of the mold defining the molding cavity is formed of ceramic. 
     
     
         35 . A method as recited in  claim 32 , wherein selective heating of the metal billet so as to melt the metal billet is accomplished substantially simultaneously with the metal entering the molding cavity. 
     
     
         36 . A method of manufacturing an orthodontic bracket from metal, comprising:
 selectively heating a metal billet by RF induction heating adjacent to a molding cavity defined by a mold formed of a material that is substantially insensitive to heating by RF induction, the molding cavity being in the shape of an orthodontic bracket, the metal billet melting such that substantially all of the metal enters the molding cavity through an entrance portion of the molding cavity corresponding to a bonding pad of the orthodontic bracket, the metal substantially filling the molding cavity;   pressing a surface of the metal within the molding cavity adjacent to the entrance with a pressing member before the metal completely cools so as to apply a mesh, sawtooth, or textured pattern to a bonding pad surface of the orthodontic bracket;   allowing the metal within the molding cavity to cool;   removing the metal orthodontic bracket from the molding cavity; and   bending the bonding pad surface of the orthodontic bracket so as to form a curved bonding pad having undercuts within the bonding pad surface.   
     
     
         37 . A method as recited in  claim 36 , wherein at least that portion of the mold defining the molding cavity is formed of ceramic. 
     
     
         38 . A method as recited in  claim 36 , wherein the metal billet comprises a zirconium based metallic amorphous alloy. 
     
     
         39 . A method as recited in  claim 38 , wherein the zirconium based metallic amorphous alloy comprises at least one alloy selected from the group consisting of (Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 ) 98 Y 2 , (Zr 34 Ti 15 Cu 12.5 Ni 11 Be 28 ) 98 Y 2 , Zr 34 Ti 15 Cu 12 Ni 11 Be 28 Y 2 , (Zr 34 Ti 15 Cu 12 Ni 11 Be 28 ) 98 Y 2 , (Zr 34 Ti 15 Cu 10 Ni 11 Be 22.5 ) 98 Y 2 , (Zr 55 Al 15 Ni 10 Cu 20 ) 98 Y 2 , and (Zr 55 Al 15 Ni 10 Cu 20 ) 96 Y 4 . 
     
     
         40 . A method as recited in  claim 36 , wherein selective heating of the metal billet so as to melt the metal billet is accomplished substantially simultaneously with the metal entering the molding cavity.