Mold Structure and Method of Manufacture Thereof
Disclosed are a mold gate insert as well as a mold assembly and an injection molding machine incorporating such a mold gate insert. The mold gate insert comprises a base structure formed of a wear resistant material having a first thermal conductivity. The base structure defines a mold cavity, at least in part, a nozzle assembly alignment portion for aligning a nozzle assembly with respect to the base structure, and a gate for communication between the mold cavity and the nozzle assembly. The mold gate insert further comprises a heat dam being completely enclosed by the base structure. The heat dam is made of a material having a second thermal conductivity being less than the first thermal conductivity and arranged within the base structure in proximity to the nozzle assembly alignment portion such that the heat flow between the nozzle assembly and the base structure is impeded. Furthermore, a method of producing the mold gate insert is disclosed.
1 . A mold gate insert, comprising:
a base structure formed of a wear resistant material having a first thermal conductivity and defining:
a mold cavity, at least in part;
a nozzle assembly alignment portion for aligning a nozzle assembly with respect to the base structure; and
a gate for communication between the mold cavity and the nozzle assembly; and
a heat dam being completely enclosed by the base structure;
wherein the heat dam is made of a material having a second thermal conductivity being less than the first thermal conductivity, and is arranged within the base structure in close proximity to the nozzle assembly alignment portion such that the heat flow between the nozzle assembly and the base structure is impeded.
2 . The mold gate insert of claim 1 , wherein the cross-section of the heat dam is one of substantially rectangular, circular and quadratic.
3 . The mold gate insert of claim 1 , wherein the base structure further defines a cooling channel within the base structure for cooling the mold cavity.
4 . The mold gate insert of claim 3 , wherein the shape of the cooling channel corresponds to the adjacent surface of the mold cavity.
5 . The mold gate insert of anyone of the preceding claims, wherein the base structure is made from steel.
6 . The mold gate insert of anyone of the preceding claims, wherein the heat dam is made from a ceramic material.
7 . A heat dam disposed in a base structure of a mold gate insert for use in a molding system, the base structure having a first thermal conductivity, said heat dam comprising a body made of a material having a second thermal conductivity being less than the first thermal conductivity, said body being completely enclosed within the base structure in close proximity to a nozzle assembly alignment portion of the mold gate insert such that the heat flow between a nozzle assembly and the base structure is impeded.
8 . A mold assembly for an injection molding machine, comprising:
a mold cavity;
a mold core cooperating with said mold cavity to form a molded article from molten plastic resin injected into said mold cavity during an injection cycle;
a gate for permitting flow of said resin from a nozzle tip into said mold cavity, said gate formed in a mold gate insert according to anyone of claims 1 to 6 ; and stripping means for stripping said molded article from said mold cavity.
9 . An injection molding machine having a plurality of mold cavities for forming a plurality of molded articles during an injection cycle, comprising:
a source of molten plastic resin;
a plurality of nozzle assemblies, each said nozzle assembly having a nozzle channel for conveying said resin to a heated nozzle tip; and
a mold gate insert according to anyone of claims 1 to 6 adjacent each said nozzle assembly, said mold gate insert permitting communication between said nozzle assembly and its respective mold cavity.
10 . An investment casting method for producing a mold gate insert including a base structure formed of a wear resistant first material having a first thermal conductivity and a heat dam being made of a second material having a second thermal conductivity being less than the first thermal conductivity, the method comprising:
providing a wax model of the base structure, wherein the second material of the heat dam is completely enclosed by the wax model of the base structure;
coating the wax model of the base structure with a ceramic shell;
hardening the ceramic shell of the wax model of the base structure;
replacing the wax of the wax model of the base structure within the ceramic shell by the molten first material, which thereby completely encloses the second material of the heat dam; and
solidifying the molten first material within the ceramic shell of the base structure and removing the ceramic shell.
11 . The investment casting method of claim 10 , wherein the wax of the wax model of the base structure within the ceramic shell is replaced by the molten first material by casting the molten first material into the ceramic shell of the wax model of the base structure and thereby melting and removing the wax of the wax model of the base structure within the ceramic shell.
12 . The investment casting method of claim 10 , wherein the wax of the wax model of the base structure within the ceramic shell is replaced by the molten first material by removing the wax of the wax model of the base structure within the ceramic shell and thereafter casting the molten first material into the ceramic shell.
13 . The investment casting method of anyone of claims 10 to 12 , wherein the wax model of the base structure completely enclosing the second material of the heat dam is provided by molding wax over a piece of material having the shape of the heat dam.
14 . The investment casting method of anyone of claims 10 to 12 , wherein the wax model of the base structure completely enclosing the second material of the heat dam is provided by molding a wax structure, having the shape of the base structure and a cavity having the shape of the heat dam.
15 . The investment casting method of anyone of claims 10 to 12 , wherein the wax model of the base structure completely enclosing the second material of the heat dam is provided by molding a wax structure having the shape of the base structure as a solid block and, thereafter, mechanically processing said solid block to provide for a cavity having the shape of the heat dam.
16 . A method for producing a mold assembly element including a base structure formed of a wear resistant first material having a first thermal conductivity and a heat dam being made of a second material having a second thermal conductivity being less than the first thermal conductivity, the method comprising:
providing a wax model of the base structure, wherein the second material of the heat dam is completely enclosed by the wax model of the base structure;
coating the wax model of the base structure with a ceramic shell;
hardening the ceramic shell of the wax model of the base structure;
replacing the wax of the wax model of the base structure within the ceramic shell by the molten first material, which thereby completely encloses the second material of the heat dam; and
solidifying the molten first material within the ceramic shell of the base structure and removing the ceramic shell.