Recoating system for using high viscosity build materials in solid freeform fabrication

• US 6,656,410 B2
• Filed: 01/17/2002
• Issued: 12/02/2003
• Est. Priority Date: 06/22/2001
• Status: Expired due to Fees

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Hull, Charles W., Newell, Kenneth J.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US10/052,506
• Publication Number:
  US 20020195747A1
• Time in Patent Office: 684 Days
• Field of Search: 264/113, 264/234, 264/308, 264/401, 425/78, 425/174.4, 425/404
• US Class Current: 264/401
• CPC Class Codes: B22F 1/107 containing organic material comprising solvents, e.g. for slip casting
• CPC Class Codes: B22F 10/16 by embedding the binder within the powder bed
• CPC Class Codes: B22F 10/73 of powder
• CPC Class Codes: B22F 12/10 Auxiliary heating means
• CPC Class Codes: B22F 12/44 characterised by the configuration of the radiation means
• CPC Class Codes: B22F 12/63 Rollers
• CPC Class Codes: B22F 12/67 Blades
• CPC Class Codes: B29C 35/00 Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor moulds with incorporated heating or cooling means B29C33/02 ; thermal after-treatment of shaped articles B29C71/02; curing devices for plastics dental prostheses A61C13/14; before moulding B29B13/00
• CPC Class Codes: B29C 41/12 Spreading-out the material on a substrate , e.g. on the surface of a liquid
• CPC Class Codes: B29C 64/106 using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
• CPC Class Codes: B29C 64/124 using layers of liquid which are selectively solidified
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B29K 2105/0094 having particular viscosity
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 70/10 Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A method of applying highly viscous paste-like build materials in layers in a solid freeform fabrication apparatus to form three-dimensional objects. A viscosity modifier is first introduced into the build material to establish a low viscosity state and then the material is dispensed in layers on a working surface. The viscosity modifier is then removed from the build material preferably by evaporation, and the layer is selectively solidified to form the three-dimensional object. The method substantially eliminates the undesirable effects of induced shear stress imposed on lower layers when attempting to apply uniform layers of highly viscous materials in solid freeform fabrication techniques. The method allows for the use of highly viscous paste-like materials that can include upwards of 50% by weight of metallic, ceramic, mineral, or polymer powders. Preferably the binder is a photocurable resin or thermocurable material which is selectively solidified to form the three-dimensional objects.

Claims

1. A method of applying a build material in layers in a solid freeform fabrication apparatus, the method comprising the steps of:

a) introducing a viscosity modifier in the build material to establish a low viscosity state having a first viscosity value;

b) applying the build material by the apparatus on a working surface to form a layer of build material while the build material is in the low viscosity state;

c) transforming the layer of build material from the low viscosity state to a high viscosity state by removing the viscosity modifier, the transformation being of an amount sufficient that when applying another layer of the build material late low viscosity state over the layer of build material in the high viscosity state, the transference of shear stress to the layer of build material in the high viscosity state is substantially prevented; and

d) solidifying portions of the layer to establish a solidified state of build material forming the layers of the three-dimensional object;

e) repeating steps b) through d) until said three-dimensional object is formed.

3. The method of claim 1 wherein the step transforming the layer of build material is accomplished by applying thermal heat to remove the viscosity modifier from the layer of build material.

4. The method of claim 1 wherein the viscosity modifier is a solvent and the solvent is removed from the layer of the build material by evaporation.

5. The method of claim 4 wherein the solvent is selected from the group consisting of hydrocarbons, aliphatic hydrocarbons, naphtha, mineral oil, aromatic hydrocarbons, benzcne, toluene, functional aromatics, O-Cresol, halogenated hydrocarbons, chlorinated solvents, carbon tetrachioride, carbon dioxide, freon, methylene chloride, monohydric alcohols, polyhydric alcohols, phenols, ethers, tetrahydrotbran, glycol ethers. ketones, acetone, cyclohexanone, acetophenone, amines, n-Butylamine, N,N-Dimethylaniline, acids, chromic acids, nitric acids, phosphoric acids, inorganics, water, silicon tetrachloride, phosphoric trichloride, esters, N-Butyl acetate, ethyl acetate, nitrogen-containing compounds, nitrates, nitriles, organic sulfur compounds, acids/aldehydes, acetic acid, trichloroacetic acid, hydroxide bases, ammonium hydroxide, sodium hydroxide, peroxides, hydrogen peroxide, and combinations thereof.

22. The method of claim 1 wherein the viscosity modifier is introduced in the build material prior to being delivered to the apparatus.

2. The method of claim 2 wherein the high viscosity state of the build material has a second viscosity value wherein the first viscosity value of the build material is less than at least one-half of the second viscosity value.

6. The method of claim 2 wherein in transforming the layer of build material from the low viscosity state to the high viscosity state, the second viscosity value of the build material is raised at least to a point where the build material in the layer is substantially self-supporting.

7. The method of claim 2 wherein the build material in the high viscosity state is a liquid, a semi-solid, a gel, a foam, or a paste, and the second viscosity value of the high viscosity state is greater than at least about 10,000 centipoise at ambient conditions.

8. The method of claim 7 wherein the high viscosity state build material is a photopolymerizable resin.

9. The method of claim 8 wherein the photoplymerizable resin is selected from a photopolyrner based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

10. The method of claim 7 wherein the high viscosity state build material is a thermally polymerizable material.

11. The method of claim 10 wherein the thermally polymerizable material includes a peroxide-based thermal initiator.

12. The method of claim 7 wherein the build material comprises a plurality of particulate matter and a bonding agent.

13. The method of claim 12 wherein the particulate matter is a powder comprising any combination of a polymer, mineral, metal, or ceramic.

14. The method of claim 13 wherein the polymer powder is a thermoplastic selected from the group consisting of ABS, Nylon, polypropylene, polycarbonate, polyethersulfate and combinations thereof.

15. The method of claim 13 wherein the metallic powder is selected from the group consisting of steel, steel alloy, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, tungsten, tungsten carbide, molybdenum, nickel alloy, lanthanum, hafnium, tantalum, rhenium, rubidium, bismuth, cadmium, indium, tin, zinc, cobalt, manganese, chromium, gold, silver, and combinations thereof.

16. The method of claim 13 wherein the ceramic powder is selected from the group consisting of aluminum nitride, aluminum oxide, calcium carbonate, fluoride, magnesium oxide, silicon carbide, silicon dioxide, silicon nitride, titanium carbide, titanium carbonitride, titanium diboride, titanium dioxide, tungsten carbide, tungsten trioxide, zirconia, zinc suphide, and combinations thereof.

17. The method of claim 13 wherein the mineral powder is selected from the group consisting of cerium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, lutetium oxide, samarium oxide, terbium oxide, yttrium oxide, and combinations thereof.

18. The method of claim 12 wherein the bonding agent comprises a photopolymerizable resin or a thermally polyrnerizable material.

19. The method of claim 18 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

20. The method of claim 18 wherein the thermally polymerizable material includes a peroxide-based thermal initiator.

21. The method of claim 19 wherein the build material further comprises a polymethyl methacrylate tackifier additive.

23. A system of applying a build material in layers in a solid freeform fabrication apparatus to form a three-dimensional object, the system comprising:

means for delivering the build material to the apparatus;

means for introducing a viscosity modifier in the build material to establish a low viscosity state having a first viscosity value;

means for applying the build material by the apparatus on a working surface while the build material is in the low viscosity state to form a layer of the build material;

means for transforming the layer of build material by removing the viscosity modifier from the layer of the build material to establish a high viscosity state for the layer of build material, the removal of the viscosity modifier being of an amount sufficient that when applying another layer of the build material in the low viscosity state over the layer of build material in the high viscosity state, the transference of shear stress to the layer of build mated al in the high viscosity state is substantially prevented; and

means for solidifying portions of the layer of the build material to establish a solidified state forming the three-dimensional object.

24. The system of claim 23 wherein the high viscosity state of the build material has a second viscosity value wherein the first viscosity value of the build material is at least less than about one-half of the second viscosity value.

25. The system of claim 23 wherein the means for transforming the layer of build material includes a means for thermally heating the layer of build material to remove the viscosity modifier from the layer of build material.

26. The system of claim 23 wherein the viscosity modifier is a solvent removed by evaporation.

27. The system of claim 26 wherein the solvent is selected from the group consisting of hydrocarbons, aliphatic hydrocarbons, naphtha, mineral oil, aromatic hydrocarbons, benzene, toluene, functional aromatics, O-Cresol, halogenated hydrocarbons, chlorinated solvents, carbon tetrachloride, carbon dioxide, freon, methylene chloride, monohydric alcohols, polyhydric alcohols, phenols, ethers, tetrahydrofuran, glycol ethers, ketones, acetone, cyclohexanone, acetophenone, amines, n-Butylamine, N,N-Dimethylaniline, acids, chromic acids, nitric acids, phosphoric acids, inorganics, water, silicon tetrachloride, phosphoric trichloride, esters, N-Butyl acetate, ethyl acetate, nitrogen-containing compounds, nitrates, nitriles, organic sulfur compounds, acids/aldehydes, acetic acid, trichloroactic acid, hydroxide bases, amonium hydroxide, sodium hydroxide, peroxides, hydrogen peroxide, and combinations thereof.

28. The system of claim 23 wherein the means of transforming the layer of build material transforms the layer at least to a point where the build material in the layer is substantially self-supporting.

29. The system of claim 23 wherein the build material in the high viscosity state is a liquid, a semi-solid, a gel, a foam, or a paste, and the second viscosity value of the high viscosity state is greater than at least about 10,000 centipoise at ambient conditions.

30. The system of claim 29 wherein the high viscosity state build material is a photopolymerizable resin or a thermally polymerizable material.

31. The system of claim 30 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

32. The system of claim 29 wherein the build material comprises a plurality of particulate matter and a bonding agent.

33. The system of claim 32 wherein the particulate matter is a powder comprising any combination of a polymer, mineral, metal, or ceramic.

34. The system of claim 33 wherein the polymer powder is selected from the group consisting of thermoplastics, ABS, Nylon, polypropylene, polycarbonate, and polyethersulfate and combinations thereof.

35. The system of claim 33 wherein the metallic powder is selected from the group consisting of steel, steel alloy, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, tungsten, tungsten carbide, molybdenum, nickel alloy, lanthanum, hafnium, tantalum, rhenium, rubidium, bismuth, cadmium, indium, tin, zinc, cobalt, manganese, chromium, gold, silver, and combinations thereof.

36. The system of claim 33 wherein the ceramic powder is selected from the group consisting of aluminum nitride, aluminum oxide, calcium carbonate, fluoride, magnesium oxide, silicon carbide, silicon dioxide, silicon nitride, titanium carbide, titanium casrbonitride, titanium diboride, titanium dioxide, tungsten carbide, tungsten trioxide, zirconia, zinc sulphide, and combinations thereof.

37. The system of claim 33 wherein the mineral powder is selected from the group consisting of cerium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, lutetium oxide, samarium oxide, terbium oxide, yttrium oxide, and combinations thereof.

38. The system of claim 32 wherein the bonding agent comprises a photopolymerizable resin or a thermally polymerizable material.

39. The system of claim 38 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

40. The system of claim 39 wherein the build material further comprises a polymethyl methacrylate tackifier additive.

41. The system of claim 23 wherein the means for solidifying portions of the layer of build material is accomplished by exposing the portions of the layer of build material to actinic radiation.

42. The system of claim 30 wherein the thermally polymerizable material includes a peroxide based thermal initiator.

43. The system of claim 38 wherein the thermally polymerizable material includes a peroxide based thermal initiator.

44. A solid freeform apparatus for forming a three-dimensional object from a build material in a plurality of layers, the apparatus comprising:

means for dispensing the build material to form a layer of build material on a working surface while the build material is in a low viscosity state;

means for transforming the layer of the build material to a high viscosity state, the transformation being of an amount sufficient that when applying another layer of the build material in the low viscosity state over the layer of build material in the high viscosity state, the transference of shear stress to the layer of build material in the high viscosity state is substantially prevented; and

means for solidifying portions of the layer of the build material to establish a solidified state by selectively exposing the portions of the layer of the build material to radiation.

45. The apparatus of claim 44 further comprising:

means for introducing a viscosity modifier in the build material to establish the low viscosity state having a first viscosity value, the high viscosity state having a second viscosity value and wherein the first viscosity value of the build material is at least less than about one-half of the second viscosity value.

46. The apparatus of claim 45 wherein the means for dispensing the build material comprises at least one smoothing member and the means for removing the viscosity modifier comprises at least one heater for evaporating the viscosity modifier.

47. The apparatus of claim 45 wherein the means for dispensing the build material comprises at least one gravity fed recoating applicator.

48. The apparatus of claim 47 wherein the gravity fed recoating applicator comprises a container for holding the build material, a distribution roller adjacent the container, a skive adjacent the distribution roller, and a smoothing member adjacent the distribution roller, the distribution roller and container being positioned so as to establish a dispensing orifice wherein build material is dispensed through the dispensing orifice when the distribution roller rotates.

49. The apparatus of claim 44 further comprising two or more means for dispensing the build material, each means for dispensing the build material adapted to dispense a different formulation of build material.

50. A method of building a three-dimensional object in a solid freeform fabrication apparatus in layerwise fashion, the method comprising the steps of:

a) retaining at least one build material containing a viscosity modifier in the apparatus, the build material being in a low viscosity state;

b) applying the build material to a working surface to form a layer of the build material while the build material is in the low viscosity state;

c) transforming the layer of build material from the low viscosity state to a high viscosity state by removing the viscosity modifier from the layer of the build material, the transformation being of an amount sufficient that when applying another layer of the build material in the low viscosity state over the layer of build material in the high viscosity state, the transference of shear stress to the layer of build material in the high viscosity state is substantially prevented; and

d) solidifying at least a portion of the applied layer of the build material establishing a solidified state of the build material;

e) repeating steps b) through d) until the three-dimensional object is formed.

51. The method of claim 50 further comprising the step of:

f) separating the solidified three-dimensional object from un-solidified build material in the high viscosity state.

52. The method of claim 50 wherein more than one build material formulation is applied to form the three-dimensional object.

53. The method of claim 50 wherein the high viscosity state of the build material has a second viscosity value wherein the first viscosity value of the build material is less than at least one-half of the second viscosity value.

54. The method of claim 50 wherein the step of transforming the layer of build material is accomplished by applying heat to remove the viscosity modifier from the layer of build material.

55. The method of claim 54 wherein the viscosity modifier is a solvent removed by evaporation.

56. The method of claim 55 wherein the solvent is selected from the group consisting of hydrocarbons, aliphatic hydrocarbons, naphtha, mineral oil, aromatic hydrocarbons. benzene, toluene, functional aromatics, O-Cresol, halogenated hydrocarbons, chlorinated solvents, carbon tetrachloride, carbon dioxide, freon, methylene chloride, monohydric alcohols, polyhydric alcohols, phenols, ethers, tetrahydrofuran, glycol ethers, ketones, acetone, cyclohexanone, acetophenone, amines, n-Butylamine, N,N-Dimethylaniline, acids, chromic acids, nitric acids, phosphoric acids, inorganics, water, silicon tetrachloride, phosphoric trichloride, esters, N-Butyl acetate, ethyl acetate, nitrogen-containing compounds, nitrates, nitriles, organic sulfur compounds, acids/aldehydes, acetic acid, trichloroactic acid, hydroxide bases, ammonium hydroxide, sodium hydroxide, peroxides, hydrogen peroxide, and combinations thereof.

57. The method of claim 53 wherein in transforming the layer of build material from the low viscosity state to the high viscosity state, the second viscosity value of the build material is raised at least to a point where the build material in the layer is substantially self-supporting.

58. The method of claim 53 wherein the build material in the high viscosity state is a liquid, a semi-solid, a gel, a foam, or a paste, and the second viscosity value of the high viscosity state is greater than at least about 10,000 centipoise at ambient conditions.

59. The method of claim 58 wherein the high viscosity state build material is a photopolymerizable resin or a thermally polymerizable material.

60. The method of claim 59 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

61. The method of claim 60 wherein the build material further comprises a polymethyl methacrylate tackifier additive.

62. The method of claim 58 wherein the build material comprises a plurality of particulate matter and a bonding agent.

63. The method of claim 62 wherein the particulate matter is a powder comprising any combination of a polymer, mineral, metal, or ceramic.

64. The method of claim 63 wherein the polymer powder is a thermoplastic selected from the group consisting of ABS, Nylon, polypropylene, polycarbonate, and polyethersulfate and combinations thereof.

65. The method of claim 63 wherein the metallic powder is selected from the group consisting of steel, steel alloy, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, tungsten, tungsten carbide, molybdenum, nickel alloy, lanthanum, hafnium, tantalum, rhenium, rubidium, bismuth, cadmium, indium, tin, zinc, cobalt, manganese. chromium, gold, silver, and combinations thereof.

66. The method of claim 63 wherein the ceramic powder is selected from the group consisting of aluminum nitride, aluminum oxide, calcium carbonate, fluoride, magnesium oxide, silicon carbide, silicon dioxide, silicon nitride, titanium carbide, titanium carbonitride, titanium diboride, titanium dioxide, tungsten carbide, tungsten trioxide, zirconia, zinc sulphide, and combinations thereof.

67. The method of claim 63 wherein the mineral powder is selected from the group consisting of cerium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, lutetium oxide, samarium oxide, terbium oxide, yttrium oxide, and combinations thereof.

68. The method of claim 62 wherein the bonding agent comprises a photopolymerizable resin.

69. The method of claim 68 wherein the photopolymerizable resin is selected from a phoropolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

70. The method of claim 50 wherein the step of solidifying portions of the layer of build material is accomplished by exposing the portions of the layer of build material to actinic radiation.

71. The method of claim 50 wherein the step of applying the build material comprises spreading the build material along the working surface with at least one smoothing member.

72. The method of claim 62 wherein the bonding agent is a thermally polymerizable material.

73. The method of claim 72 wherein the step of solidifying portions of the layer of build material is accomplished by exposing the portions of the layer of build material to infra-red radiation.

74. The method of claim 59 wherein the thermally polymerizable material includes a peroxide based thermal initiator.

75. The method of claim 72 wherein the thermally polymerizable material includes a peroxide based thermal initiator.

76. A method of forming a three-dimensional object from a build material in a layer wise fashion by solid freeform fabrication, the method comprising the steps of:

a) applying the build material on a working surface to form a layer of build material while the build material is in a low viscosity state;

b) transforming the layer of build material from the low viscosity state to a high viscosity state, the transformation being of an amount sufficient that when applying another layer of the build material in the low viscosity state over the layer of build material in the high viscosity state, the transference of shear stress to the layer of build material in the high viscosity state is substantially prevented;

c) solidifying portions of the layer of build material in the high viscosity state to establish a solidified state of the build material forming the three-dimensional object;

d) repeating steps a) through c) until said three-dimensional object is formed.

77. The method of claim 76 wherein the high viscosity state of the build material has a second viscosity value wherein the first viscosity value of the build material is less than at least one-half of the second viscosity value.

78. The method of claim 77 wherein a viscosity modifier is present in the layer of build material applied in the low viscosity state, and the step of transforming the layer of build material is accomplished by applying thermal heat to remove the viscosity modifier from the layer of build material.

79. The method of claim 78 wherein the viscosity modifier is a solvent removed by evaporation.

80. The method of claim 79 wherein the solvent is selected from the group consisting of hydrocarbons, aliphatic hydrocarbons, naphtha, mineral oil, aromatic hydrocarbons, benzene, toluene, functional aromatics, O-Cresol, halogenated hydrocarbons, chlorinated solvents, carbon tetrachloride, carbon dioxide, freon, methylene chloride, monohydric alcohols, polyhydric alcohols, phenols, ethers, tetrahydrofuran, glycol ethers, ketones, acetone, cyclohexanone, acetophenone, amines, n-Butylamine, N,N-Dimethylaniline, acids, chromic acids, nitric acids, phosphoric acids, inorganics, water, silicon tetrachloride, phosphoric trichloride, esters, N-Butyl acetate, ethyl acetate, nitrogen-containing compounds, nitrates, nitriles, organic sulfur compounds, acids/aldehydes, acetic acid, trichloroactic acid, hydroxide bases, ammonium hydroxide, sodium hydroxide, peroxides, hydrogen peroxide, and combinations thereof.

81. The method of claim 77 wherein in transforming the layer of build material from the low viscosity state to the high viscosity state, the second viscosity value of the build material is raised at least to a point where the build material in the layer is substantially self-supporting.

82. The method of claim 77 wherein the build material in the high viscosity state is a liquid, a semi-solid, a gel, a foam, or a paste, and the second viscosity value of the high viscosity state is greater than at least about 10,000 centipoise at ambient conditions.

83. The method of claim 82 wherein the high viscosity state build material is a photopolymerizable resin or a thermally polymerizable material.

84. The method of claim 83 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

85. The method of claim 84 wherein the build material further comprises a polymethyl methacrylate tackifler additive.

86. The method of claim 82 wherein the build material comprises a plurality of particulate matter and a bonding agent.

87. The method of claim 86 wherein the particulate matter is a powder comprising any combination of a polymer, mineral, metal, or ceramic.

88. The method of claim 87 wherein the polymer powder is a thermoplastic selected from the group consisting of ABS, Nylon, polypropylene, polycarbonate, polyethersulfate and combinations thereof.

89. The method of claim 87 wherein the metallic powder is selected from the group consisting of steel, steel alloy, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, tungsten, tungsten carbide, molybdenum, nickel alloy, lanthanum, hafnium, tantalum, rhenium, rubidium, bismuth, cadmium, indium, tin, zinc, cobalt, manganese, chromium, gold, silver, and combinations thereof.

90. The method of claim 87 wherein the ceramic powder is selected from the group consisting of aluminum nitride, aluminum oxide, calcium carbonate, fluoride, magnesium oxide, silicon carbide, silicon dioxide, silicon nitride, titanium carbide, titanium carbonitride, titanium diboride, titanium dioxide, tungsten carbide, tungsten trioxicle, zirconia, zinc sulphide, and combinations thereof.

91. The method of claim 87 wherein the mineral powder is selected from the group consisting of cerium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, lutetium oxide, samarium oxide, terbium oxide, yttrium oxide, and combinations thereof.

92. The method of claim 86 wherein the bonding agent comprises a photopolymerizable resin.

93. The method of claim 92 wherein the bonding agent comprises a photopolyrnerizable resin or a thermally polymerizable material.

94. The method of claim 93 wherein the photopolymerizable resin is selected from a photopolymer based group consisting of acrylates, epoxies, vinyl ethers, and combinations thereof.

95. The method of claim 76 wherein the step of solidifying portions of the layer of build material is accomplished by exposing the portions of the layer of build material to actinic radiation.

96. The method of claim 93 wherein the thermally polymerizable material includes a peroxide based thermal initiator.