Three-dimension printer with mechanically scanned cathode-comb

Patent metadata

Field	Value
Publication number	US-2016332228-A1
Application number	US-201514709009-A
Country	US
Kind code	A1
Filing date	May 11, 2015
Priority date	May 11, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

A 3-D printer scalable to large sizes employs a combination of mechanical and electrical scanning of a linear array of electron beams that operate to melt material of a powder bed. A housing holding the electron beam sources may be maintained at a high vacuum and positioned close to a print surface to minimize electron travel in a softer vacuum surrounding a print bed.

First claim

We claim:

1 . A three-dimension printer comprising:
a print bed for supporting an object to be printed; a printer bar extending along a transverse axis; a printer bar carriage assembly supporting the printer bar with respect to the print bed to move longitudinally above the print bed at a predetermined height above a print surface over the print bed; wherein the printer bar supports a plurality of independently controllable, transversely separated electron sources for generating electron beams directed toward the print bed and an electron deflector assembly for transverse deflection of the electron beams; a powder handling system for applying powder at the print surface over the print bed; and a controller communicating with the electron sources and printer bar carriage to scan the electron sources over powder on the print bed to selectively fuse the powder at the print surface into a printed object according to a program stored in a non-transient medium.

2 . The three-dimension printer of claim 1 wherein the electron beams are constrained to move substantially only in the transverse direction with respect to the printer bar.

3 . The three-dimension printer of claim 1 wherein the electron deflector provides a common deflection field across each of the electron beams to deflect the electron beams in unison.

4 . The three-dimension printer of claim 3 wherein the deflection field is a magnetic field produced by at least one Helmholtz coil pair separated along a longitudinal axis.

5 . The three-dimension printer of claim 1 wherein the electron sources are transversely spaced by no more than one-half of a transverse range of deflection of the electron sources measured at the print surface.

6 . The three-dimension printer of claim 1 further including a first housing holding a print bed and printer bar and a second housing within the first housing holding the electron sources of the printer bar and further including at least a first and second vacuum pump, the second vacuum pump communicating with the second sealable airtight housing to pump gas from the second sealable airtight housing into the first sealable airtight housing, and the first vacuum pump communicating with the first sealable airtight housing to pump gas from the first sealable airtight housing to an exhaust point outside of the first sealable airtight housing.

7 . The three-dimension printer of claim 6 wherein the first vacuum pump provides a higher pressure vacuum in the first sealable airtight housing than the second vacuum pump provides in the second sealable airtight housing.

8 . The three-dimension printer of claim 7 wherein the second vacuum pump operates to maintain a hard vacuum with a pressure of less than 10 −4 Torr.

9 . The three-dimension printer of claim 7 wherein the first vacuum pump operates to maintain a soft vacuum with a pressure greater than 10 −4 Torr.

10 . The three-dimension printer of claim 6 wherein the surface of the second housing closest to the print surface is less than six inches from the print surface.

11 . The three-dimension printer of claim 6 wherein the second housing provides a transverse slit positioned between the electron sources and the print bed to allow passage of the electron beams throughout a transverse deflection of the electron beams and wherein the second housing is substantially sealed but for the transverse slit.

12 . The three-dimension printer of claim 11 further including an electron transmissive window covering the slit.

13 . The three-dimension printer of claim 6 further including a nitrogen purge system for filling the second housing when the first housing is unsealed.

14 . The three-dimension printer of claim 6 wherein the electron sources include electrode emitting cathodes and wherein a majority of a path length of the electron beams between the cathodes and the print surface is within the second housing.

15 . The three-dimension printer of claim 1 wherein the electron sources include electron-emitting cathodes spaced from the print surface by less than two feet.

16 . The three-dimension printer of claim 1 wherein there are at least 10 electron sources and wherein the printer bar carriage assembly provides a longitudinal movement of at least 15 feet.

17 . The three-dimension printer of claim 1 wherein the powder handling system provides a movable powder spreader controllably movable along a plane above the print bed to apply powder to the print head.

18 . The three-dimension printer of claim 1 further including a powder preheat heater positionable to move along the transverse direction over the print bed.

19 . The three-dimension printer of claim 1 wherein the controller executes the program to receive identifications of regions on the print surface for melting by an electron beam and selects among different electron beams capable of melting that region to promote parallel operation of electron beams.

20 . The three-dimension printer of claim 1 wherein each electron beam is associated with an electron beam detector, and wherein the controller further executes the program to compensate for failure of an individual cathode by employing adjacent cathodes.

Assignees

• Wisconsin Alumni Res Found

Inventors

• Mackie Thomas Rockwell
• Walker Brandon Joseph

Classifications

• B22F10/85 Primary

  for controlling or regulating additive manufacturing processes · CPC title

• B22F12/45

  Two or more · CPC title

• B22F12/13

  to preheat the material · CPC title

• B22F12/20

  Cooling means · CPC title

• B22F10/28

  Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM] · CPC title