Method for additive manufacturing with partial curing
A method of additive manufacturing (AM) includes dispensing a first building material formulation to form an outer region, and dispensing a second building material formulation to form an inner region, the outer region surrounding the inner region, the inner and outer regions being shaped to form a layer of the object; exposing the layer to a first curing condition, repeating the dispensing and the exposing to sequentially form a plurality of layers of the object and collectively exposing the plurality of layers to a second curing condition. The selections are such that the first building material formulation is hardened to a higher degree than the second building formulation. The outer regions form a hardened coating that at least partially encapsulates the inner regions. The second curing condition is other than the first curing condition and is selected to increase the degree that the inner region is hardened.
1. A method of manufacturing a three-dimensional object via additive manufacturing (AM), the method comprising:
dispensing a first building material formulation to form an outer region, and dispensing a second building material formulation to form an inner region, the outer region surrounding the inner region, the inner and outer regions being shaped to form a layer of the object;
exposing the layer to a first curing condition, wherein the first and the second building material formulations and the first curing condition are selected such that upon the exposing to said first curing condition, the first building material formulation is polymerized to a higher degree than the second building formulation,
repeating the dispensing and the exposing to the first curing condition to sequentially form a plurality of layers of the object, wherein the outer regions form a hardened coating that at least partially encapsulates the inner regions; and
collectively exposing the plurality of layers to a second curing condition, wherein the second curing condition is other than the first curing condition and wherein the second curing condition is selected to increase a degree that the inner region is hardened by polymerization and/or cross-linking,
wherein the first building material formulation comprises a first curable material which is a UV curable material, and a photo-initiator in an amount that ranges from 1 to 3 weight percent of the total weight of the first building material formulation, and the second building material formulation comprises a second curable material which is a UV curable material, and a photo-initiator in an amount that is less than 50% of said amount of the photo-initiator in the first building material formulation,
wherein each of the first and second building material formulations provides a transparent hardened material, and
wherein said first curing condition comprises UV-irradiation.
2. The method of claim 1 , wherein the second building material formulation comprises at least a sub-formulation A and a sub-formulation B, each comprising the second curable material, wherein an amount of the photo-initiator in sub-formulation A ranges from 1 to 3 weight percent of the total weight of sub-formulation A, and an amount of the photo-initiator in sub-formulation B is less than 50% of the amount of the photoinitiator in sub-formulation A, and wherein an amount of sub-formulation A in the inner region is no more than 50% by weight of an amount of sub-formulation B in the inner region.
3. The method of claim 2 , wherein dispensing the second building formulation is such that the sub-formulation A is dithered within the inner region.
4. The method of claim 1 , wherein said second curable material features, when hardened, at least one of:
a heat distortion temperature (HDT) above a steady state temperature of the plurality of layers during the AM process;
a glass transition temperature (Tg) above a steady state temperature of the plurality of layers during the AM process;
a heat distortion temperature (HDT) above 70° C.; and
a glass transition temperature (Tg) above 70° C.
5. The method of claim 1 , wherein said first curable material features, when hardened, at least one of:
a heat distortion temperature (HDT) below a steady state temperature of the plurality of layers during the AM process;
a glass transition temperature (Tg) below a steady state temperature of the plurality of layers during the AM process;
a heat distortion temperature (HDT) below 70° C.; and
a glass transition temperature (Tg) below 70° C.
6. The method of claim 1 , wherein the coating is configured to have a thickness that is less than 1 mm.