Pre-heating methods for performing electron beam powder bed fusion
Electron beam powder bed fusion may be performed using waste powder from laser beam powder bed fusion by pre-heating a build chamber using stepped increases of electron beam current. To perform the pre-heating without smoking the powder, a plurality of predetermined interim temperatures, ranging from an ambient, resting temperature of the build chamber to a predetermined preheated temperature, are determined. A build plate within the build chamber is exposed to a plurality of streams of electrons, one at a time, while the build plate is surrounded by the waste powder. Each stream of electrons has a progressively increasing current, with the current being increased each time an actual temperature of the build chamber reaches or exceeds the next predetermined interim temperature. The actual temperature of the build chamber is monitored during the pre-heating, to compare the actual temperature of the build chamber to the plurality of predetermined interim temperatures.
1. A method of performing electron beam powder bed fusion (EB-PBF) additive manufacturing, comprising:
determining a plurality of predetermined interim temperatures ranging from an ambient, resting temperature of a build chamber of an EB-PBF machine to a predetermined preheated temperature, wherein each subsequent predetermined interim temperature of the plurality of predetermined interim temperatures is greater than each previous predetermined interim temperature of the plurality of predetermined interim temperatures; and
pre-heating the build chamber to the predetermined preheated temperature, wherein the pre-heating the build chamber comprises:
exposing a build plate within the build chamber to a plurality of streams of electrons, one at a time, wherein the build plate is surrounded by waste powder that is leftover and obtained from a laser beam powder bed fusion system, wherein each stream of electrons of the plurality of streams of electrons has a different respective current, and wherein each stream of electrons of the plurality of streams of electrons is configured to raise an actual temperature of the build chamber;
monitoring the actual temperature of the build chamber during the exposing the build plate to the plurality of streams of electrons;
comparing the actual temperature of the build chamber to the plurality of predetermined interim temperatures; and
increasing a power input of the EB-PBF machine a plurality of times, thereby exposing the build plate to a subsequent stream of electrons of the plurality of streams of electrons, wherein the subsequent stream of electrons has a greater current level than a previous stream of electrons of the plurality of streams of electrons, and wherein the increasing the power input is performed each time the actual temperature of the build chamber reaches a respective subsequent predetermined interim temperature of the plurality of predetermined interim temperatures, as determined during the comparing the actual temperature to the plurality of predetermined interim temperatures.
2. The method according to claim 1 , wherein the pre-heating the build chamber to the predetermined preheated temperature comprises actively controlling the power input of the EB-PBF machine to deliver stepped increases of electron beam current.
3. The method according to claim 1 , wherein the pre-heating the build chamber to the predetermined preheated temperature is sufficiently slow such that a static charge of the waste powder is substantially allowed to dissipate, thereby at least substantially preventing smoking of the waste powder.
4. The method according to claim 1 , wherein the plurality of streams of electrons comprises at least seven different streams of electrons and at most twenty different streams of electrons.
5. The method according to claim 1 , wherein the plurality of streams of electrons comprises at least one stream of electrons having a current below 5 milliamp (mA).
6. The method according to claim 1 , wherein the waste powder comprises a titanium alloy powder.
7. The method according to claim 1 , wherein the waste powder has an average particle size of less than 60 micrometers (μm).
8. The method according to claim 1 , further comprising deflecting an electron beam via an electromagnetic field, thereby selectively fusing portions of an initial layer of the waste powder by raising the actual temperature of the portions of the initial layer of the waste powder to above a melting point of the waste powder, wherein the selectively fusing portions of the initial layer of the waste powder is performed after the pre-heating the build chamber to the predetermined preheated temperature.
9. The method according to claim 8 , further comprising:
lowering the build plate;
spreading a subsequent layer of the waste powder across a build area;
selectively fusing portions of the subsequent layer of the waste powder by heating portions of the subsequent layer above the melting point of the waste powder; and
repeating the lowering the build plate, the spreading the subsequent layer of the waste powder, and the selectively fusing portions of the subsequent layer a plurality of times, until a resulting additively manufactured part is completed.
10. The method according to claim 1 , further comprising:
performing laser beam powder bed fusion to create an object; and
reserving the waste powder left over from the performing laser beam powder bed fusion to use in EB-PBF additive manufacturing.
11. The method according to claim 1 , wherein the pre-heating the build chamber to the predetermined preheated temperature takes at least 60 minutes and at most 120 minutes.
12. The method according to claim 1 , wherein the pre-heating the build chamber to the predetermined preheated temperature has an overall rate of temperature increase of between 6-8 degrees Celsius (° C.) per minute.
13. A method of performing electron beam powder bed fusion (EB-PBF) additive manufacturing, comprising:
pre-heating a build chamber to a predetermined preheated temperature, wherein the pre-heating the build chamber comprises:
exposing a build plate within the build chamber to a first stream of electrons at a first current for a first time period sufficient to pre-heat the build chamber to a predetermined first interim temperature, wherein the build plate is surrounded by waste powder that is leftover and obtained from a laser beam powder bed fusion system;
monitoring an actual temperature of the build chamber to determine when the actual temperature of the build chamber reaches the predetermined first interim temperature; and
exposing the build plate to a second stream of electrons once the actual temperature of the build chamber reaches the predetermined first interim temperature, wherein the second stream of electrons has a second current that is greater than the first current, wherein the build plate is exposed to the second stream of electrons for a second time period sufficient to pre-heat the build plate to a predetermined second interim temperature, wherein the predetermined second interim temperature is greater than the predetermined first interim temperature and less than the predetermined preheated temperature.
14. The method according to claim 13 , further comprising determining a plurality of predetermined interim temperatures ranging from an ambient, resting temperature of the build chamber to the predetermined preheated temperature, wherein each subsequent predetermined interim temperature of the plurality of predetermined interim temperatures is greater than each previous predetermined interim temperature of the plurality of predetermined interim temperatures, and wherein the plurality of predetermined interim temperatures comprises the predetermined first interim temperature and the predetermined second interim temperature.
15. The method according to claim 14 , further comprising:
monitoring the actual temperature of the build chamber to determine when the actual temperature of the build chamber reaches the predetermined second interim temperature; and
exposing the build plate to a third stream of electrons once the actual temperature of the build chamber reaches the predetermined second interim temperature, wherein the third stream of electrons has a third current that is greater than the second current, wherein the build plate is exposed to the third stream of electrons for a third time period sufficient to pre-heat the build chamber to a predetermined third interim temperature, wherein the predetermined third interim temperature is greater than the predetermined second interim temperature and less than the predetermined preheated temperature.
16. The method according to claim 15 , further comprising repeating the monitoring the actual temperature of the build chamber a plurality of times for the plurality of predetermined interim temperatures, and repeating the exposing the build plate to a different respective stream of electrons of a plurality of streams of electrons each time the actual temperature of the build chamber reaches a subsequent respective interim temperature of the plurality of predetermined interim temperatures, until the actual temperature of the build chamber reaches or exceeds the predetermined preheated temperature.
17. The method according to claim 13 , wherein the predetermined first interim temperature is 50° C. or lower, wherein the predetermined second interim temperature is 100° C. or lower, wherein a plurality of predetermined interim temperatures comprises a predetermined third interim temperature that is 200° C. or lower, a predetermined fourth interim temperature that is 250° C. or lower, a predetermined fifth interim temperature that is 400° C. or lower, a predetermined sixth interim temperature that is 550° C. or lower, a predetermined seventh interim temperature that is 650° C. or lower, and a predetermined eighth interim temperature that is 750° C. or lower.
18. The method according to claim 13 , wherein the first current of the first stream of electrons is less than 5 mA, and wherein the second current of the second stream of electrons is between 5-15 mA.
19. The method according to claim 13 , wherein the waste powder comprises a titanium alloy powder that has an average particle size of less than 60 μm.
20. A part made using the method of claim 13 .