Magnetic platen assembly for additive manufacturing system

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

a printing mechanism configured to print imaged layers of charged powder material to a moving belt; and a platen assembly comprising:

a platen plate having a top surface having a plurality of spaced apart members extending therefrom; and

one or more magnets secured to the platen plate and configured to generate one or more magnetic fields at the top surface of the platen plate; wherein the platen assembly is configured to magnetically couple a build sheet to the top surface of the platen plate due to the one or more generated magnetic fields and the plurality of spaced apart members are configured to be accepted by a plurality of apertures in the build sheet, and wherein the build sheet is configured to receive the printed layers from the printing mechanism wherein the platen assembly moves in a synchronized rate of speed with the imaged layer to transfer the imaged layer from the moving belt to the platen or previously printed part layers over time using heat and pressure.

2. The additive manufacturing system of claim 1 , and further comprising the build sheet, which comprises:

a base sheet comprising one or more ferromagnetic materials; and

a top film disposed on the base sheet and comprising one or more polymeric materials, wherein the top film defines a receiving surface for the build sheet to receive the printed layers and wherein the plurality of apertures extend through the base sheet and the top sheet.

3. The additive manufacturing system of claim 2 , wherein the top film comprises an adhesive tape.

4. The platen assembly of claim 1 , wherein the printing mechanism comprises one or more electrophotography engines and a transfer medium.

5. The additive manufacturing system of claim 1 , and further comprising at least one heating element configured to heat the platen plate and the magnetically coupled build sheet.

6. The additive manufacturing system of claim 1 , and further comprising a gantry mechanism operably secured to the platen plate.

7. The additive manufacturing system of claim 1 , wherein the one or more magnets are permanent magnets.

8. The additive manufacturing system of claim 1 , wherein the one or more magnets are electromagnets configured to receive electrical currents from the additive manufacturing system to generate and to disable the one or more magnetic fields.

9. A method for using a platen assembly in an electrophotography-based additive manufacturing system, the method comprising:

placing a first build sheet onto a top surface of a platen plate that is operably mounted to a gantry mechanism of the additive manufacturing system by positioning a plurality of holes in the first build sheet about a plurality of members extending from the platen plate; magnetically coupling the placed first build sheet to the top surface of the platen plate;

printing imaged layers of a three dimensional part of charged powder material to a moving belt;

transferring the imaged layers of a three-dimensional part onto the magnetically-coupled first build sheet wherein the platen plate and build sheet moves in a synchronized rate of speed with the layer on the moving belt while heating and pressing the printed layers to previously printed layers over time: removing the first build sheet with the printed three-dimensional part from the top surface of the platen plate;

flexing the first build sheet to delaminate the three-dimensional part from the first build sheet; and

placing a second build sheet onto the top surface of the platen plate;

magnetically coupling the placed second build sheet to the top surface of the platen plate; and

printing layers of a second three-dimensional part onto the magnetically-coupled second build sheet.

10. The method of claim 9 , wherein the first build sheet comprises a ferromagnetic base sheet and a top film disposed on the ferromagnetic base sheet, and wherein printing layers of the three-dimensional part onto the magnetically-coupled first build sheet comprises printing layers of the three-dimensional part onto the top film of the first build sheet.

11. The method of claim 9 , wherein printing the layers of the three-dimensional part and printing the layers of the second three-dimensional part are each performed with an electrophotography-based additive manufacturing technique.

12. The method of claim 9 , wherein printing layers of the three-dimensional part onto the magnetically-coupled first build sheet comprises rolling a nip roller across the magnetically-coupled first build sheet.

13. The method of claim 9 , and further comprising heating the platen plate and the build sheet.

14. The method of claim 13 , and further comprising thermally insulating the platen plate from the gantry mechanism.