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

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.

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.

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.

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.