Layer transfusion for additive manufacturing

1. An additive manufacturing system for printing a three-dimensional part, the additive manufacturing system comprising:

an imaging engine configured to develop imaged layers of a thermoplastic-based powder;

at least three rollers, wherein each roller is positioned in a fixed position and rotatable about an axis of rotation, wherein at least a first roller comprises a nip roller and the second roller comprises a release roller wherein the fixed positions of the nip roller and the release roller are proximate a build plane and wherein the fixed position of a third roller of the at least three rollers is located a distance from the build plane;

a rotatable belt having a first surface and a second surface, the rotatable belt configured to receive imaged layers of a thermoplastic-based powder on the first surface, each imaged layer having a length from a leading edge to a trailing edge and a width from a first side to a second side, wherein the second surface of the belt is configured to engage the at least three rollers and wherein the at least three rollers define a path of travel of the belt wherein the travel path of the belt proximate the build plane follows a first distance between a transfer engaging location at the nip roller and a transfer disengaging location at the release roller, and the travel path descends in a rotational direction toward the nip roller and ascends in a rotational direction away from the build plane proximate the transfer disengaging location;

a first heater configured to heat the imaged layers on the belt;

a build platform configured to move and receive the imaged layers from the belt in a layer-by-layer manner to print the three-dimensional part on the build platform; and

a gantry configured to move the build platform in a reciprocating pattern such that a top surface of the part being formed on the build platform travels within the build plane and out of the build plane, the movement being synchronized with the rotational rate of the belt wherein the gantry is configured to move the top surface of the part being formed in the build plane a second distance from a first build plane location to a second build plane location wherein the second distance is longer than the first distance, wherein the first build plane location is located a third distance in an upstream direction of the transfer engaging location such that the part being formed on the build platform is not in contact with the imaged layer or the belt at the first build plane location, and the leading edge of the imaged layer is configured to register with a front location of the build platform at the nip roller as the top surface of the part being formed moves in the build plane such that the imaged layer is transferred to the previously printed layer in a line by line manner across the width of the imaged layer utilizing pressure and heat as the nip roller rotates and the build platform is moved from the first build plane location to the second build plane location, and wherein the second build plane location is located a distance from the transfer disengaging location such that the trailing edge is configured to disengage the belt as the top surface of the part being formed moves in the build plane.

2. The additive manufacturing system of claim 1 , wherein the imaging engine comprises an electrophotography engine which is configured to develop the imaged layers from the thermoplastic-based powder.

3. The additive manufacturing system of claim 1 , wherein the belt comprises a multiple-layer belt.

4. The additive manufacturing system of claim 1 , wherein the gantry is configured to move the build platform in a reciprocating rectangular pattern.

5. The additive manufacturing system of claim 1 , and further comprising a second heater spaced apart from the fixed location of the nip roller and configured to heat a surface of the three-dimensional part prior to engaging the nip roller.

6. The additive manufacturing system of claim 1 , wherein the nip roller comprises a heatable roller.

7. The additive manufacturing system of claim 1 , further comprising:

a first cooling unit configured to cool the transfer medium between the nip roller and the release roller.

8. The additive manufacturing system of claim 7 , wherein the nip roller is configured to be heated to at least the fusion temperature of the thermoplastic-based powder.

9. The additive manufacturing system of claim 1 , and further comprising a cooling unit located downstream of the release roller, the second cooling unit configured to hold the part at about a creep relaxation temperature of the thermoplastic-based powder.

10. The additive manufacturing system of claim 9 , wherein the cooling unit is further configured to hold the part within about 10° C. degrees Celsius of a creep relaxation of the thermoplastic-based powder.

11. The additive manufacturing system of claim 1 , and further comprising a second heater configured to heat the movable build platform to assist in maintaining the average part temperature.

12. The additive manufacturing system of claim 1 , and further comprising a cooling unit located downstream from the transfer disengaging location, the cooling unit configured to actively cool the transfused layers to hold the printed three-dimensional part at about an average part temperature that is below a deformation temperature of the three-dimensional part.

13. An additive manufacturing system for printing a three-dimensional part, the additive manufacturing system comprising:

at least two rollers, wherein each roller is positioned in a fixed position and rotatable about an axis of rotation, wherein at least a first roller comprises a nip roller and a second roller comprises a release roller spaced a first distance from the nip roller, wherein the fixed positions of the nip roller and the release roller are proximate a build plane wherein the nip roller and the release roller define a path of travel of a belt proximate the build plane and wherein the travel path descends in a rotational direction toward the build plane proximate the nip roller and ascends in a rotational direction away from the build plane proximate the release roller;

the rotatable belt having a front side and a back side, the front side configured to receive a developed layer of a thermoplastic-based powder from an electrophotography engine and the back side configured to engage the at least two rollers wherein the developed layer has a leading edge and a trailing edge and a width defined by first and second side surfaces;

a build platform configured to move and receive the imaged layers from the belt in a layer-by-layer manner to print the three-dimensional part on the build platform;

a gantry configured to move the build platform in a reciprocating pattern such that a top surface of the part being formed on the build platform travels within the build plane and out of the build plane, the movement being synchronized with the rotational rate of the belt wherein the gantry is configured to move the top surface of the part being formed in the build plane a second distance from a first build plane location to a second build plane location wherein the second distance is longer than the first distance, wherein the first build plane location is located a third distance in an upstream direction of the nip roller such that the part being formed on the build platform is not in contact with the imaged layer or the belt at the first build plane location, and the leading edge of the imaged layer is configured to register with a front location of the build platform at the nip roller as the top surface of the part being formed moves in the build plane such that the imaged layer is transferred to the previously printed layer in a line by line manner across the width of the imaged layer utilizing pressure and heat as the nip roller rotates and the build platform is moved from the first build location to the second build location, and wherein the second build plane location is located a distance from the release roller such that the trailing edge is configured to disengage the belt as the top surface of the part being formed moves in the build plane.

14. The additive manufacturing system of claim 13 , wherein the rotatable belt comprises a multiple-layer belt.

15. The additive manufacturing system of claim 13 , wherein the gantry is configured to move the build platform in a reciprocating rectangular pattern.

16. The additive manufacturing system of claim 13 , and further comprising:

a first cooling unit configured to cool the rotatable belt between the nip roller and the release roller.

17. The additive manufacturing system of claim 13 , and further comprising a heater spaced apart from the nip roller and configured to heat a surface of the three-dimensional part prior to each layer transfusion.

18. The additive manufacturing system of claim 13 , and further comprising a cooling unit configured to cool the transfer medium between the nip roller and the release roller.

19. The additive manufacturing system of claim 13 , and further comprising a cooling unit located downstream from the release roller, the cooling unit configured to actively cool the transfused layers to hold the printed three-dimensional part at about an average part temperature that is below a deformation temperature of the three-dimensional part.

20. The additive manufacturing system of claim 13 , and further comprising a first heater configured to heat the developed layer on the belt.

21. The additive manufacturing system of claim 20 , and further comprising a second heater configured to heat the upper surface of the part being printed prior to engaging the belt proximate the nip roller.

22. The additive manufacturing system of claim 13 , and wherein the nip roller is configured to be heated.