Three-dimensional printing system having semipermeable transparent sheet with aerostatic support

1. A three-dimensional printing system for fabricating a three-dimensional article comprising:

a support plate including a transparent central portion, the support plate defining a gas inlet and a gas outlet;

a transparent sheet disposed above the support plate, the transparent sheet including:

a peripheral seal portion that is sealed with respect to the support plate; and

a central unsupported portion bounded by the peripheral seal portion and overlaying the transparent central portion, the gas inlet, and the gas outlet and defining a central chamber between the transparent sheet and the support plate;

a flow resistance L o is defined for gas exiting from the central chamber through the gas outlet;

a gas pressure source providing gas to the gas inlet; and

a conduit coupled between the gas pressure source and the gas inlet;

a flow resistance L i is defined for gas passing through the conduit, through the gas inlet, and to the central chamber, L i >L o to allow the central unsupported portion of the transparent sheet to maintain a stable configuration as a function of a source gauge pressure P s applied by the gas pressure source to the conduit.

2. The three-dimensional printing system of claim 1 wherein the transparent sheet rests upon an upper surface of the transparent central portion of the support plate when the gauge pressure P s is zero.

3. The three-dimensional printing system of claim 1 wherein the peripheral seal portion of the transparent sheet is supported above the upper surface of the transparent central portion of the support plate.

4. The three-dimensional printing system of claim 3 wherein the support of the peripheral seal portion and the source gauge pressure P s maintain a gap between the central unsupported portion of the transparent sheet and the transparent central portion of the support plate in a range of 100 to 500 microns.

5. The three-dimensional printing system of claim 1 wherein P s is at least 5 pounds per square inch (PSI).

6. The three-dimensional printing system of claim 1 wherein P s is at least about 15 pounds per square inch (PSI).

7. The three-dimensional printing system of claim 1 wherein L i is at least 10 times L o .

8. The three-dimensional printing system of claim 1 wherein P c is a gauge pressure in the central chamber, P s is at least 10 times P c .

9. The three-dimensional printing system of claim 8 wherein P s is at least 30 times P c .

10. The three-dimensional printing system of claim 8 wherein P s is at least 100 times P c .

11. The three-dimensional printing system of claim 1 wherein a resin vessel includes a substructure that is coupled to the transparent sheet, the substructure cooperates with the transparent sheet to house a column of photocurable resin.

12. The three-dimensional printing system of claim 11 further comprising:

a light engine configured to project radiation up through the transparent central portion of the support plate and the transparent sheet and to a build plane within the resin;

a build tray having a lower surface for supporting the three-dimensional article;

a positioning mechanism for positioning a lower surface of the three-dimensional article proximate to the build plane; and

a controller at least operatively coupled to the light engine and the positioning mechanism, the controller operates the light engine and the positioning mechanism to fabricate the three-dimensional article in a layer-by-layer manner.

13. The three-dimensional printing system of claim 12 wherein the controller is coupled to one or more of the gas pressure source and the conduit to modulate the pressure P c to maintain a desired configuration of the unsupported portion of the transparent sheet.

14. A three-dimensional printing system for fabricating a three-dimensional article comprising:

a support plate including a transparent central portion, the support plate defining a gas inlet and a gas outlet;

a transparent sheet disposed above the support plate, the transparent sheet including:

a peripheral seal portion that is sealed with respect to the support plate; and

a central unsupported portion bounded by the peripheral seal portion and overlaying the transparent central portion, the gas inlet, and the gas outlet and defining a central chamber between the transparent sheet and the support plate;

a flow resistance L o is defined for gas exiting from the central chamber through the gas outlet;

a flow resistance L c is defined for gas passing through the central chamber from the gas inlet to the gas outlet, a value of L c is a variable function of a gas flow rate;

a gas pressure source providing gas to the gas inlet; and

a conduit coupled between the gas pressure source and the gas inlet;

a flow resistance L i is defined for gas passing through the conduit, through the gas inlet, and to the central chamber, L i >(L o +L c ) during a steady state flow of gas that maintains a stable physical configuration of the transparent sheet.

15. The three-dimensional printing system of claim 14 wherein the peripheral seal portion of the transparent sheet is supported above the upper surface of the transparent central portion of the support plate.

16. The three-dimensional printing system of claim 15 wherein the support of the peripheral seal portion and a source gauge pressure (P s ) of the gas pressure source maintain a gap between the central unsupported portion of the transparent sheet and the transparent central portion of the support plate in a range of 100 to 500 microns.

17. The three-dimensional printing system of claim 15 wherein the transparent sheet is supported to be generally flat above the central portion of the support plate.

18. The three-dimensional printing system of claim 14 wherein L i is at least ten times (L o +L c ) during operation.