Method and apparatus for creating sacrificial patterns and cast parts

• US 20060255512A1
• Filed: 05/12/2005
• Published: 11/16/2006
• Est. Priority Date: 05/12/2005
• Status: Active Grant

• Current Assignee: Victor Joyner
• Original Assignee: Victor Joyner
• Inventors: Joyner, Victor
• Granted Patent: US 7,479,247 B2
• Time in Patent Office: Days
• US Class Current: 264/496
• CPC Class Codes: B29C 2791/005 Using a particular environment, e.g. sterile fluids other than air
• CPC Class Codes: B29C 2791/006 Using vacuum
• CPC Class Codes: B29C 35/0888 using transparant moulds

Abstract

A process and apparatus for casting three-dimensional parts and sacrificial models from a class of casting compounds which incorporate one or more radiation activated photo initiators which cause polymerization of the casting compound causing it to solidify or transition from a solid in a first state to a solid more suitable for use as a sacrificial model in a lost wax casting process. The class of casting compounds include, 1) compounds which act as conduits for the polymerization initiating radiation during and/or after hardening and 2) compounds which are hardened by a radiation induced chain reaction throughout the body of fluid casting compound. These compounds allow the part being cast to be cured within transparent molds that are supported by transparent mold frames. The apparatus consists of a radiation source positioned to irradiate the casting compound within a mold cavity through the mold frame and mold wall to effect the polymerization, solidifying, process. Separation of the molded part from the mold is enabled by the relative flexibility between the part and mold cavity walls. This is a function of using a soft, flexible material for the mold body and/or a polymerization process which caused the casting compound the solidify into a soft, flexible object. When the polymerized cast part is at least partially removed from the mold, it may be subjected to additional radiation of a frequency different form that initially applied the cause the solid cast part to transition to a hard or ridged part having properties more suitable for a model which is to be used as a sacrificial model in a lost wax process. An automated casting system is anticipated which is enabled by the use of very soft, stretchable and deformable material for the mold body and supporting the mold with radiation transparent mold frames. Oxygen and other gases in the atmosphere react with some casting compounds to create a sticky film on mold cavity walls which causes difficulty when removing a casting from a mold. This problem is eliminated by purging the mold cavity with an inert gas between casts.

Claims

1. An apparatus for casting parts, comprising:

a mold incorporating a mold cavity for receiving a casting compound;

a plurality of inter-fitting sections dimensioned to create said mold cavity when assembled;

said inter-fitting sections fabricated from one or more of a class of materials which have the properties of being radiation transparent, yielding to the touch, stretchable, pliable and shape retentive; and

a radiation transparent mold frame comprised of a plurality of sections for containing, stabilizing and holding said inter-fitting sections in said assembled condition for creating said mold cavity.

2. An apparatus as defined by claim 1 wherein said casting compound is a polymerizable liquid containing at least two substances, each which becomes a polymerization inducing agent when subjected to radiation at a frequency different from the other.

3. An apparatus as defined by claim 1, comprising:

means for filling said mold cavity with a polymerizable casting compound; and

means for causing polymerization of said casting compound within said mold cavity by subjecting said casting compound within said mold cavity to a polymerization initiating radiation whereby said casting compound becomes a solid part.

4. An apparatus as defined by claim 3 wherein said polymerization initiating radiation has a frequency selected from one or more of the class of frequency bands consisting of radio frequency, high frequency, microwave, x-ray, infrared, visible light and ultraviolet.

5. An apparatus as defined by claim 1, comprising:

means for bringing said plurality of inter-fitting sections together to create said mold cavity; and

means for enclosing said plurality of inter-fitting sections within said radiation transparent mold frame.

6. An apparatus as defined by claim 5 where in said means for bringing said plurality of inter-fitting sections together to create said mold cavity and said means for enclosing said plurality of inter-fitting sections within said radiation transparent mold frame comprises a converging conveying means.

7. An apparatus as defined by claim 1, comprising:

means for purging said mold cavity with an inert gas;

means for evacuating said mold cavity for creating a partial vacuum therein; and

means for filling said evacuated mold cavity with said casting compound.

8. An apparatus as defined by claim 7 wherein said inert gas is argon.

9. An apparatus as defined by claim 7 wherein said casting compound is a polymerizable liquid containing a substance which becomes a polymerization inducing agent when subjected to radiation.

10. An apparatus as defined by claim 9, wherein said radiation has a frequency selected from one or more of the class of frequency bands consisting of radio frequency, high frequency, microwave, x-ray, infrared, visible light and ultraviolet.

11. An apparatus as defined by claim 9, wherein said radiation is actinic radiation.

12. An apparatus as defined by claim 9, wherein said radiation is ultraviolet radiation.

13. An apparatus as defined by claim 7, comprising:

at least one vent hole means for allowing gas to escape as said mold cavity is filled with said casting compound; and

said hole having a small diameter, such as might be created by a 22 gauge needle.

14. An apparatus as defined by claim 7 wherein said casting compound is a polymerizable liquid containing at least two substances, each of which becomes a polymerization inducing agent when subjected to radiation at a frequency different from the other.

15. An apparatus as defined by claim 14, wherein said radiation frequencies are selected from one or more of the class of frequency bands consisting of radio frequency, high frequency, microwave, x-ray, infrared, visible light, blacklight ultraviolet and blacklight blue ultraviolet.

16. An apparatus as defined by claim 14, wherein one of said substances becomes a polymerization inducing agent when subjected to actinic radiation.

17. An apparatus as defined by claim 14, wherein one of said substances becomes a polymerization inducing agent when subjected to microwave radiation.

18. An apparatus as defined by claim 14, wherein one of said substances becomes a polymerization inducing agent when subjected to blacklight ultraviolet radiation and one of said substances becomes a polymerization inducing agent when subjected to blacklight blue ultraviolet radiation.

19. An apparatus as defined by claim 14, wherein one of said substances becomes a polymerization inducing agent when subjected to 352 nanometer radiation and one of said substances becomes a polymerization inducing agent when subjected to 368 radiation.

20. An apparatus as defined by claim 7 wherein said means for filling said evacuated mold cavity with casting compound comprises means for pressure injecting said casting compound into said evacuated mold cavity.

21. An apparatus as defined by claim 7, comprising:

means for causing polymerization of said casting compound within said mold cavity by subjecting said casting compound within said mold cavity to a polymerization initiating radiation whereby said casting compound becomes a solid casting; and

means for removing said solid casting from said mold cavity.

22. An apparatus as defined by claim 21 wherein said means for removing one of said mold frame sections for destabilizing an associated one of said inter-fitting sections and said means for removing said one of said inter-fitting sections from said casting comprises a diverging conveying means.

23. An apparatus as defined by claim 21, wherein said means for removing said solid casting comprises:

means for removing one of said mold frame sections for destabilizing an associated one of said inter-fitting sections;

means for removing said one of said inter-fitting sections from said casting;

means for removing a last one of said mold frame sections for destabilizing an associated last one of said inter-fitting sections; and

means for removing said last one of said inter-fitting sections from said casting for completely removing said solid casting from said mold.

24. An apparatus as defined by claim 23, comprising:

means for submitting said casting to a second source of polymerization initiating radiation after removing at least one of said inter-fitting sections from said casting

25. An apparatus as defined by claim 24 wherein said means for removing one of said mold frame sections for destabilizing an associated one of said inter-fitting sections and said means for removing said one of said inter-fitting sections from said solid casting comprises a diverging conveying means.

26. An apparatus as defined by claim 7, comprising:

means for causing polymerization of said casting compound within said mold cavity by subjecting said casting compound within said mold cavity to a first polymerization initiating radiation whereby said casting compound becomes a soft casting; and

means for causing polymerization of said soft casting by subjecting said soft casting to a second polymerization initiating radiation whereby said soft casting becomes a hard casting.

27. An apparatus as defined by claim 26, comprising:

means for removing one of said mold frame sections for destabilizing an associated one of said inter-fitting sections after said casting compound becomes said soft casting;

means for removing said one of said inter-fitting sections from said casting;

means for removing a last one of said mold frame sections for destabilizing an associated last one of said inter-fitting sections;

means for removing said last one of said inter-fitting sections from said soft casting for completely removing said soft casting from said mold; and

subjecting said removed soft casting to said second polymerization initiating radiation whereby said soft casting becomes a hard casting.

28. An apparatus as defined by claim 26, comprising:

means for removing one of said mold frame sections for destabilizing an associated one of said inter-fitting sections after said casting compound becomes said soft casting;

means for removing said one of said inter-fitting sections from said soft casting;

subjecting said partially exposed soft casting to said second polymerization initiating radiation whereby said soft casting becomes a hard casting;

means for removing a last one of said mold frame sections for destabilizing an associated last one of said inter-fitting sections;

means for removing said last one of said inter-fitting sections from said hard casting for completely removing said hard casting from said mold.

29. An apparatus as defined by claim 7, wherein said means for filling said mold cavity comprises:

a source of inert gas;

a pressure regulator for regulating the outlet pressure of said source of inert gas;

a gas flow control valve for controlling gas flow from said pressure regulator mutually exclusively between first and second gas conduits;

a fill valve including and inlet port, mold connection port and an outlet port wherein said inlet port and said outlet port are mutually exclusively connected to said mold connection port;

said first gas conduit connected between said gas flow control valve and said inlet port;

a casting compound reservoir incorporating a casting compound injection output means for transporting casting compound to said inlet port of said fill valve;

said second gas conduit connected between said gas flow control valve and said casting compound reservoir for supplying pressurized gas to said casting compound reservoir for forcing casting compound through said casting compound injection output means;

a vacuum pump for evacuating said mold cavity via said outlet port of said fill valve; and

mean for connecting the sprue of said mold cavity to said mold connection port of said fill valve.

30. An apparatus for casting parts, comprising:

a mold incorporating a mold cavity;

a plurality of inter-fitting sections dimensioned to create said mold cavity when said inter-fitting sections are assembled as a mold assembly;

said inter-fitting sections fabricated from one or more of a class of materials which have the properties of being radiation transparent, yielding to the touch, stretchable, pliable and shape retentive;

a radiation transparent mold frame comprised of a plurality of sections for containing, stabilizing and holding said inter-fitting sections together as said mold assembly;

a converging conveying means for bringing said plurality of inter-fitting sections together for creating said mold assembly;

said converging conveying means for bringing said plurality of sections of said radiation transparent mold frame together for enclosing said plurality of inter-fitting sections;

means for purging said mold cavity with an inert gas;

means for evacuating said mold cavity for creating a partial vacuum therein;

means for filling said evacuated mold cavity with a casting compound;

means for causing polymerization of said casting compound within said mold cavity by subjecting said casting compound within said mold cavity to a polymerization initiating radiation whereby said casting compound becomes a casting; and

a diverging conveying means for removing said mold frame sections for destabilizing said inter-fitting sections and removing said inter-fitting sections from said casting.

31. An apparatus as defined by claim 30, comprising:

means for initiating a second polymerization reaction within said casting after said casting is at least partially uncovered by removal of at least one of said inter-fitting sections.

32. A method for casting parts, including the steps of:

creating a mold incorporating a mold cavity by assembling a plurality of inter-fitting sections fabricated from one or more of a class of materials which have the properties of being radiation transparent, yielding to the touch, stretchable, pliable and shape retentive which are dimensioned to create said mold cavity;

stabilizing said mold by enclosing it in a radiation transparent mold frame;

purging said mold cavity with an inert gas;

evacuating said mold cavity;

filling said evacuated mold cavity with a casting compound;

subjecting said casting compound within said mold cavity to a polymerizing initiating radiation and thereby causing said casting compound to polymerize into a solid casting;

removing said radiation transparent mold frame from said mold; and

removing said inter-fitting sections from said casting.

33. A method for casting parts as defined by claim 32, including the step of subjecting said solid casting to a second polymerizing initiating radiation after at least one of said inter-fitting sections are removed from said casting during said step of removing said inter-fitting sections from said casting and thereby causing said casting to polymerize into a solid casting having enhanced properties.

34. A method for casting parts as defined by claim 33, wherein said steps of subjecting said casting compound within said mold cavity to a polymerizing initiating radiation and thereby causing said casting compound to polymerize into a solid casting and subjecting said solid casting to a second polymerizing initiating radiation employ radiation in different bands selected from the class of radiation bands including the 352 nanometer band and the 368 nanometer band.

35. A method for casting parts as defined by claim 32, including the step of subjecting said solid casting to a second polymerizing initiating radiation after said step of removing said inter-fitting sections from said casting and thereby causing said casting to polymerize into a solid casting having enhanced properties.

36. A method for casting parts as defined by claim 33, wherein said steps of subjecting said casting compound within said mold cavity to a polymerizing initiating radiation and thereby causing said casting compound to polymerize into a solid casting and subjecting said solid casting to a second polymerizing initiating radiation employ radiation in different bands selected from the class of radiation bands including the 352 nanometer band and the 368 nanometer band.

37. A method for casting parts as defined by claim 32, including the steps of:

regulating the outlet pressure of a source of inert gas to maintain a first pressure which will not result in gas escaping between mating faces of said plurality of inter-fitting sections;

using said inert gas at said first pressure for performing said step of purging said mold cavity;

regulating said outlet pressure of said source of inert gas to maintain a second pressure great enough to force said casting compound into said mold cavity; and

completing said step of filling said mold cavity with casting compound by applying said inert gas at said second pressure to the source of said casting compound.

38. A method for casting parts as defined by claim 37 wherein said first and second pressures are equal.