Electron gun, control method and control program thereof, and three-dimensional shaping apparatus
AssigneeTechnology Research Association for Future Additive Manufacturing
InventorTakashi Sato
Life of this patent
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Abstract
When an emission current is changed, a decrease in brightness of an electron beam is prevented. An electron gun includes a cathode that emits thermoelectrons, a Wehnelt electrode that focuses the thermoelectrons, a control electrode that extracts the thermoelectrons from a distal end of said cathode, an anode that accelerates the thermoelectrons and irradiates a powder with the thermoelectrons as an electron beam, and an optimum condition collection controller that changes at least one of a bias voltage to be applied to the Wehnelt electrode and a control electrode voltage to be applied to the control electrode, and decides a combination of the bias voltage and the control electrode voltage at which the brightness of the electron beam reaches a peak.
Claims10
An electron gun comprising:
- a cathode that emits thermoelectrons;
- a Wehnelt electrode that focuses the thermoelectrons;
- a control electrode that extracts the thermoelectrons from a distal end of said cathode;
- an anode that accelerates the thermoelectrons, and irradiates a powder with the thermoelectrons as an electron beam;
- and
- an optimum condition collection controller that determines a degree of wear of said cathode based on an emission current of said electron gun, and executes a fine adjustment for decreasing a bias voltage of the Wehnelt electrode with maintaining a voltage of the control electrode or executes a readjustment comprising automatically setting a combination of the bias voltage and the control electrode voltage so that a brightness of the electron beam reaches a predetermined brightness, by readjustment of the bias voltage and the voltage of the control electrode, based on the determined degree of wear of said cathode.
A control method of an electron gun, comprising:
- determining a degree of wear of a cathode based on a decrease in an emission current and beam diameter of the electron gun;
- executing, when the decrease in the emission current is not smaller than a predetermined threshold, a readjustment comprising automatically setting a combination of a bias voltage of a Wehnelt electrode and a voltage of a control electrode such that, at the combination, a brightness of the electron beam reaches a predetermined brightness, by readjustment of the bias voltage and the voltage of the control electrode voltage, wherein the Wenhelt electrode focuses thermoelectrons emitted by a cathode and the control electrode extracts the thermoelectrons from a distal end of the cathode;
- and
- executing, when the decrease in the emission current is smaller than the predetermined threshold, a fine adjustment for changing the bias voltage with maintaining a voltage of the control electrode.
A non-transitory computer readable medium storing a control program of an electron gun for causing a computer to execute a method, comprising:
- determining a degree of wear of a cathode based on a decrease in an emission current of the electron gun;
- executing, when the decrease in the emission current is not smaller than a predetermined threshold, a readjustment comprising automatically setting a combination of a bias voltage of a Wehnelt electrode and a voltage of a control electrode such that, at the combination, a brightness of the electron beam reaches a predetermined brightness, by readjustment of the bias voltage and the voltage of the a control electrode, wherein the Wenhelt electrode focuses thermoelectrons emitted by a cathode and the control electrode extracts the thermoelectrons from a distal end of the cathode;
- and
- executing, when the decrease in the emission current is smaller than the predetermined threshold, the fine adjustment for changing the bias voltage with maintaining a voltage of the control electrode.
Dependencies are inferred from the claim text.