Method of making a three dimensional object by stereolithography

A method for reducing irregularities in cure depth of a region of a layer of an object made by stereolithography, comprising the steps of:

• at least partially solidifying a first portion of a region of a layer by exposing the first portion to synergistic stimulation comprising a first set of lines spaced apart from each other so that no direct adhesion occurs between the lines,
• at least partially solidifying a second portion of the region of the layer by exposing the second portion to synergistic stimulation comprising a second set of lines spaced apart from each other so that no direct adhesion occurs between the lines of the second set, and with the second set of lines overlapping the first set of lines at intersection area elements which being exposed by both the lines of the first set and the lines of the second set, receive an increased exposure;
• at least partially solidifying a third portion of the region of the layer, which at least substantially includes all area elements not receiving the increased exposure resulting from the combined exposures of the first and second sets, by exposing the third portion to synergistic stimulation comprising at least a third set of lines, wherein the combined exposure of the first, second, and at least third sets results in substantially all area elements of the entire region receiving substantially equivalent exposures, wherein the lines of the at least third set are adhered to each other and to the lines of the first and second sets.

A method for reducing irregularities in cure depth of a region of a layer of an object made by stereolithography, comprising the steps of:

• at least partially solidifying a first portion of a region of a layer by exposing the first portion to synergistic stimulation comprising a first set of lines spaced apart from each other so that no direct adhesion occurs between the lines;
• at least partially solidifying a second portion of the region of the layer by exposing the second portion to synergistic stimulation comprising a second set of lines spaced apart from each other so that no direct adhesion occurs between the lines of the second set;
• at least partially solidifying a third portion of the region of the layer by exposing the third portion to synergistic stimulation comprising a third set of lines spaced apart from each other so that no direct adhesion occurs between the lines of the third set, and wherein at least some individual area elements, exposed by the lines of the first set, the lines of the second set, and the lines of the third set, receive a maximum exposure where they overlap;
• at least partially solidifying a fourth portion of the region of the layer, which at least substantially includes all area elements not receiving the maximum exposure resulting from the combined exposures of the first, second, and third sets, by exposing the fourth portion to synergistic stimulation comprising at least a fourth set of lines, wherein the combined exposure of the first, second, third, and at least fourth sets results in substantially all area elements being given similar exposures, wherein the lines of the fourth set are adhered to each other and to the lines of the first, second, and third sets.

A method for reducing irregularities in cure depth of a region of a layer of an object made by stereolithography, comprising the steps of:

• at least partially solidifying a first portion of a region of a layer by exposing the first portion to synergistic stimulation comprising a first set of lines spaced apart from each other so that no direct adhesion occurs between the lines,
• at least partially solidifying a second portion of the region of the layer by exposing the second portion to synergistic stimulation comprising a second set of lines spaced apart from each other so that no direct adhesion occurs between the lines of the second set, and wherein at least a portion of the lines of the first set and a portion of the lines of the second set adhere to each other, and wherein the lines of the first set do not overlap the lines of the second set, wherein at least some individual area elements exposed by the lines of at least one of the sets receive a maximum exposure;
• at least partially solidifying a third portion of the region of the layer, which at least substantially includes all area elements not receiving the maximum exposure resulting from the exposures of the first and second sets, by exposing the third portion to synergistic stimulation comprising at least a third set of lines, wherein the combined exposure of the first, second, and the at least third sets results in substantially all area elements being given similar exposures, wherein the lines of the at least third set are adhered to each other and to the lines of the first and second sets.

A method for determining a solidification depth of at least a portion of a skin of a three-dimensional object being formed by stereolithography from a medium solidified by exposure of a set of spaced skin lines to a beam of synergistic stimulation having a power and a scanning velocity, comprising the steps of:

• a) determining the power of the beam of synergistic stimulation;
• b) determining the spacing between the skin lines;
• c) determining the scanning velocity of the beam;
• d) calculating the exposure the beam provides based on the power of the beam, the spacing between the skin lines and the scanning velocity of the beam;
• e) specifying medium parameters of the medium relating solidification depth to exposure;
• and
• f) determining the solidification depth from the calculated exposure and the relationship between solidification depth and exposure.

A method for selecting exposure parameters to provide a desired skin depth of a skin formed from a set of spaced skin lines on a layer of an object made by stereolithographically by forming stacked layers of a medium solidified by exposure to a beam of synergistic stimulation having a scanning velocity, comprising the steps of:

• a) selecting the desired skin depth;
• b) specifying medium parameters of the medium relating solidification depth to exposure;
• c) determining the exposure required to obtain the desired skin depth by using the material parameters of the medium which relate skin depth to exposure;
• d) specifying two of beam power, skin line spacing and scanning velocity;
• e) calculating the remaining unspecified parameter of step d) using the determined exposure and the two parameters specified in step d).

A method for determining material parameters of a material having a penetration depth and a critical exposure corresponding to specific synergistic stimulation, which parameters are parameters necessary for predicting cure depth of a skin on a layer of an object made stereolithographically, comprising the steps of:

• forming a first skin on a first area of a layer by exposing the first area to a beam of synergistic stimulation having a beam power in a pattern of first skin vectors having a first offset traced at a first velocity, providing a first amount of exposure;
• forming at least a second skin on at least a second area of a layer by exposing the at least second area to the laser in a pattern of at least second skin vectors having at least a second offset traced at at least a second velocity, providing at least a second amount of exposure different from the first amount of exposure;
• measuring the thickness of the first skin and the at least second skin;
• determining the first and at least second amounts of exposures according to the relationship of exposure=beam power.div.(offset.times.velocity);
• fitting the measured thicknesses versus logarithm of exposures for the first and at least second skins to a linear relationship;
• and
• determining the slope of the linear relationship which is the penetration depth and determining the X-intercept of the linear relationship which is the critical exposure.

A stereolithographic method of constructing an object having internal and external regions, by forming stacked layers of a medium solidified by exposure to synergistic stimulation applied in a pattern, comprising the steps of:

• exposing substantially all external regions of the object to synergistic stimulation to provide skin fill on the external regions;
• specifying internal regions of the object to be selected and unselected portions wherein there is at least a selected portion and there is at least an unselected portion;
• exposing the selected portion of the internal regions to synergistic stimulation to provide skin fill on the selected portions of the internal regions;
• and
• exposing the unselected portion to synergistic stimulation in a hatch pattern.

A stereolithographic method of constructing an object by forming stacked layers of a medium solidified by exposure to synergistic stimulation applied in a pattern, comprising the steps of:

• identifying any up-facing regions, down-facing regions, and internal regions of a first layer;
• identifying any internal regions of a second layer;
• exposing any down-facing region of the first layer to synergistic stimulation to solidify substantially all area elements of the down-facing region;
• exposing any up-facing region of the first layer to synergistic stimulation to solidify substantially all area elements of the up-facing region;
• exposing at least a first portion of any internal region of the first layer to synergistic stimulation to solidify substantially all area elements within the first portion wherein the first portion has a width substantially greater than a cure width of lines of a hatch pattern;
• and
• exposing a second portion of any internal region of a second layer to synergistic stimulation in lines of a hatch pattern.