Electrophotography-based additive manufacturing with pre-sintering

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

one or more electrophotography engines configured to develop the layers of the three-dimensional part from a part material;

a transfer belt configured to receive the developed layers from the one or more electrophotography engines;

a pre-sintering heater configured to heat and press the developed layers to a sintering temperature and to sinter the developed layers on the transfer belt to provide sintered contiguous films;

a build platform;

a pressing element configured to engage with the transfer belt downstream of the pre-sintering heater to press the sintered contiguous films into contact with an intermediate build surface of the three-dimensional part on the build platform in a layer-by-layer manner;

wherein the pre-sintering heater is located upstream along the transfer assembly a distance from the pressing element such that the sintered contiguous films cool down to a transfer temperature, which is about 50° C. to 120° C. less than the sintering temperature, prior to reaching the pressing element.

2. The additive manufacturing system of claim 1 , wherein the pressing element comprises a nip roller.

3. The additive manufacturing system of claim 2 , wherein the pressing assembly further comprises a heating element configured to heat the nip roller to a temperature that is within about 15° C. below a glass transition temperature of the part material.

4. The additive manufacturing system of claim 1 , wherein the pressing element is configured to press the sintered films with an applied pressure that is less than about 30 pounds-per-square-inch.

5. The additive manufacturing system of claim 4 , wherein the applied pressure is less than about 10 pounds-per-square-inch.

6. The additive manufacturing system of claim 1 , pre-sintering heater comprises a non-contact heater.

7. The additive manufacturing system of claim 1 , pre-sintering heater comprises a press roller, a backing roller, and a heating element configured to heat the backing roller, wherein the press roller and the backing roller engage the developed films and the transfer assembly.

8. The additive manufacturing system of claim 1 , wherein each of the one or more electrophotography engines includes a development station retaining a supply of the part material, which comprises an acrylonitrile-butadiene-styrene copolymer, and wherein the transfer temperature ranges from about 100° C. to about 130° C.

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

one or more electrophotography engines configured to develop a layer of the three-dimensional part from a part material comprising an acrylonitrile-butadiene-styrene copolymer;

a transfer belt configured to receive the developed layer from the one or more electrophotography engines;

a pre-sintering heater configured to sinter the developed layer on the transfer belt to provide sintered contiguous films;

a nip roller engaged with the transfer belt at a location downstream from the pre-sintering heater such that the sintered contiguous film cools down to a temperature ranging from about 100° C. to about 130° C. prior to reaching the nip roller.

10. The additive manufacturing system of claim 9 , and further comprising a heating element configured to heat the nip roller to a temperature that is within about 15° C. below a glass transition temperature of the part material.

11. The additive manufacturing system of claim 9 , wherein the pre-sintering heater is configured to sinter the developed layer by heating the developed layer to a temperature ranging from about 180° C. to about 220° C.

12. The additive manufacturing system of claim 11 , wherein the pre-sintering heater is configured to sinter the developed layer without apply pressure to the developed layer.

13. The additive manufacturing system of claim 9 , and further comprising pressing the cooled sintered contiguous film into contact with an intermediate build surface of the three-dimensional part with an applied pressure that is less than about 30 pounds-per-square-inch.

14. A method for printing a three-dimensional part with an additive manufacturing system, the method comprising:

producing a developed layer of a part material with one or more electrophotography engines of the additive manufacturing system;

transferring the developed layer from the one or more electrophotography engines to a transfer assembly of the additive manufacturing system;

sintering the developed layer at the transfer assembly to produce a sintered contiguous film including heating the developed layer to a sintering temperature;

actively cooling the sintered contiguous film down to a transfer temperature, which is about 50° C. to 120° C. less than the sintering temperature.

15. The method of claim 14 , wherein the part material comprises an acrylonitrile-butadiene-styrene copolymer, and wherein sintering the developed layer comprises heating the developed layer to a temperature ranging from about 180° C. to about 220° C.

16. The method of claim 14 , wherein the transfer temperature ranges from about 100° C. to about 130° C.

17. The method of claim 14 , and further comprising pressing the cooled sintered contiguous film into contact with an intermediate build surface of the three-dimensional part with an applied pressure that is less than about 30 pounds-per-square-inch.

18. The method of claim 14 , wherein the transfer assembly comprises a transfer belt having a line speed ranging from about 2 inches/second to about 8 inches/second.

19. The additive manufacturing system of claim 1 , and further comprising a cooler, the cooler configured to actively cool the sintered contiguous films cool down to the transfer temperature.

20. The method of claim 14 , and further comprising preheating the intermediate build surface of the layer prior to layer transfer.