Electron gun cathode protection and beam collimation system, method, and additive manufacturing apparatus

Abstract

The application relates to an electron gun cathode protection and beam collimation system and method and an additive manufacturing device, which comprises a collimating aperture with a hole in the middle and a dynamic positive bias voltage applied to the collimating aperture, which is used to form a non-uniform electrostatic field in the hole to deviate positive ions from an upward path and physically block metal vapor; a collimating lens, which comprises a front collimating lens arranged between an electron gun anode and the collimating aperture and a rear collimating lens arranged on the side of the collimating aperture facing a workpiece, and is used to collimate an electron beam and adsorb metal vapor ions after ionization; and a beam collimation module, which is used to collect the positive ion flow concentration of the collimating lens in real time and dynamically adjust the positive bias voltage of the collimating aperture and the negative bias voltage of the collimating lens. The application can improve the cathode life, control the beam parallelism error within 0.1 mrad, improve the printing density to more than 99.5%, and achieve more than 95% adaptability in multiple working conditions.

Description

Technical Field

[0001] This application relates to the field of electron gun technology, and in particular to an electron gun cathode protection and beam collimation system, method and additive manufacturing equipment. Background Technology

[0002] Electron beam additive manufacturing is an advanced manufacturing technology that uses a high-energy electron beam as a heat source and metal powder as raw material. Its basic principle is as follows: the electron gun cathode emits electrons under electric heating or a high-voltage electric field. These electrons are accelerated by the high-voltage electric field between the anode and cathode to form a high-energy electron beam. The electron beam passes through a vacuum cavity and, after being focused and deflected, acts on pre-laid metal powder, causing the metal powder to melt and stack layer by layer to form the desired shape. It is widely used in high-end manufacturing fields such as aerospace, medical implants, and mold manufacturing. During the operation of electron beam additive manufacturing equipment, the quality of the electron beam and the cathode's working life are two key factors determining the equipment's reliability and printing quality.

[0003] In existing technologies, to extend cathode lifetime and maintain electron beam quality, ion traps are typically used to capture positive ions generated by collisions between the electron beam and residual gas molecules, preventing them from bombarding the cathode in the opposite direction under the accelerating electric field between the cathode and anode. The ion trap consists of multiple conductive plates. By applying a bias voltage to the positively charged plates, a non-uniform electrostatic field is created in the trap region, which exerts an electric force on the positive ions, causing them to deviate from their upward path. Simultaneously, some schemes incorporate an optical barrier along the electron beam transmission path, using the solid portion of the optical barrier to physically block the back-diffusion of metal vapor. These methods can, to a certain extent, suppress the bombardment of the cathode by positive ions and the contamination of the cathode by metal vapor, thereby moderately extending the cathode's operating lifetime.

[0004] However, the above scheme still has the following problems: First, the ion trap can only capture positive ions. Neutral metal vapor, unaffected by the electric field, can diffuse through the ion trap region to the cathode surface, causing contamination. The aperture can only physically block metal vapor; it has neither the ability to capture positive ions nor the function of actively collimating the electron beam. When the ion trap and aperture are set as two independent components, the electron beam needs to pass through multiple conductive plate apertures of the ion trap and the physical aperture of the aperture in sequence. Each component introduces additional beam scattering and edge collisions, leading to an increase in cumulative beam divergence. Second, the installation space and position of the ion trap and aperture inside the electron gun are mutually restrictive. If the ion trap is placed below the vacuum chamber far from the cathode, positive ions are sufficiently accelerated by the cathode-anode electric field before reaching the ion trap, and bombardment damage to the cathode has already occurred, significantly reducing the protection effect. If the ion trap is placed close to the cathode, it conflicts with the installation space of the aperture, making it difficult to simultaneously meet the performance requirements of both within the limited internal space of the electron gun. Third, the bias voltage of the ion trap is usually set to a fixed value. However, the number, energy, and type of positive ions generated vary significantly under different printing materials (metal powders) and different beam currents. A fixed voltage cannot effectively capture ions under different operating conditions, resulting in unstable protection. The combined effect of these problems leads to a cathode lifespan of only about 50 hours, a beam current parallelism error greater than 0.5 mrad, and a print density of less than 98%, making it difficult to meet the requirements of continuous industrial additive manufacturing for equipment reliability and product quality.

[0005] Therefore, it is necessary to improve one or more of the problems existing in the above-mentioned related technical solutions.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this disclosure is to provide an electron gun cathode protection and beam collimation system, method, and additive manufacturing equipment, thereby overcoming at least to some extent one or more problems caused by the limitations and defects of related technologies.

[0008] In a first aspect, this application provides an electron gun cathode protection and beam collimation system, comprising: The collimating aperture has a hole in the middle and is subject to a dynamic positive bias voltage to create a non-uniform electrostatic field in the hole to deflect positive ions from their upward path and physically block metal vapor. The collimating lens includes a front collimating lens disposed between the electron gun anode and the collimating aperture, and a rear collimating lens disposed on the side of the collimating aperture facing the workpiece, for collimating the electron beam and for adsorbing ionized metal vapor ions. The beam collimation module is used to acquire the positive ion current concentration of the collimating lens in real time, and dynamically adjust the positive bias voltage of the collimating aperture and the negative bias voltage of the collimating lens through a fuzzy PID algorithm.

[0009] In one possible implementation, the dynamic positive bias voltage of the collimating aperture ranges from 0V to +200V and is adaptively adjusted based on real-time feedback of the positive ion current concentration and the metal vapor pressure.

[0010] In one possible implementation, the collimating aperture is a thin molybdenum alloy sheet with a thickness of 0.15mm-0.3mm, and the radius of curvature of the arc at the edge of the aperture is 0.05mm-0.1mm.

[0011] In one possible implementation, the front collimating lens and the rear collimating lens are respectively composed of a first focusing coil and an insulating strip and a conductive strip wrapped inside it. The conductive strip is composed of multiple parallel conductive strips stacked at intervals along the electron gun axis. The insulating strip is disposed between the conductive strip and the first focusing coil to insulate and isolate the conductive strip from the first focusing coil. The conductive strip is cylindrical or perforated plate-shaped and is used to pass a negative charge to adsorb ionized metal vapor ions. The first focusing coil is used to collimate the electron beam. The spacing between adjacent conductive strips is 0.5mm-2mm, the material is any one of molybdenum, molybdenum alloy, tungsten or tungsten alloy, the width is 0.5mm-2mm, and the plate thickness is 0.15mm-0.3mm.

[0012] In one possible implementation, the electron gun cathode protection and beam collimation system further includes an ionization gauge disposed inside the electron gun for collecting the pressure of the metal vapor volatilized into the electron gun; the beam collimation module performs feedforward compensation based on the metal vapor pressure. When the metal vapor pressure is greater than 0.1 Pa, the voltage of the collimating aperture is increased to +80 V to enhance the electrostatic lens effect; When the metal vapor pressure is <0.05Pa, the voltage of the collimating aperture is reduced to +50V to avoid over-focusing of the beam spot.

[0013] In one possible implementation, the beam collimation module includes a sampling resistor, an isolation operational amplifier, and a controllable power supply; The sampling resistor is connected in series at the low-voltage end of the power supply circuit of the front collimating lens and the rear collimating lens, and is used to convert the ion current into a voltage drop. The isolated operational amplifier has its input terminal connected to both ends of the sampling resistor and its output terminal connected to the control terminal of the controllable power supply. It is used to amplify and level-convert the floating high-voltage side signal across the sampling resistor, converting it into a grounded measurable signal. The output terminal of the controllable power supply is connected to the collimating aperture, and is used to apply a dynamic positive bias voltage to the collimating aperture based on the measurable signal and through the fuzzy PID algorithm.

[0014] In one possible implementation, the electron gun cathode protection and beam collimation system further includes: an electron optics module for focusing, aberration correction, and deflection scanning of the electron beam; the electron optics module includes: A dynamic focusing coil is positioned after the rear collimating lens to receive the parallel electron beam collimated by the rear collimating lens. The parallel electron beam is then focused in the first stage by a focusing current to form a first working focal spot acting on the workpiece. An aberration correction coil is disposed after the dynamic focusing coil and is used to correct electron beam aberrations passing through the dynamic focusing coil; The second focusing coil is disposed after the aberration correction coil and is used to perform a second-stage focusing on the corrected electron beam to form a second working focal spot acting on the workpiece. A deflection coil, located after the second focusing coil, is used to deflect the second working focal spot to achieve the scanning action.

[0015] In one possible implementation, the fuzzy PID algorithm includes a fuzzification unit, a fuzzy rule base, a defuzzification unit, and a piecewise control strategy: The fuzzification unit is used to convert the real-time acquired deviation and deviation change rate into a fuzzy set, where the universe of discourse of the deviation is... The universe of discourse for the rate of change of deviation is The corresponding fuzzy sets are all The triangular membership function is used. The fuzzy rule base is used for fuzzy reasoning based on the rule table; The deblurring unit is used to convert the fuzzy output into a precise voltage adjustment amount using the centroid method; the voltage adjustment amount formula is: in, For voltage regulation, The membership degree of a fuzzy set. The precise value corresponding to the fuzzy set; The segmented control strategy is as follows: When the deviation is greater than 0.5V and the rate of change of deviation does not exceed 0.5V / s, the voltage regulation amount of the proportional element is obtained through the proportional element formula; the proportional element formula is: in, This is the voltage regulation amount of the proportional element. This is the proportionality coefficient. For deviation; When the deviation is greater than 0.5V and the rate of change of the deviation is greater than 0.5V / s, proportional + derivative fuzzy control is activated. The first voltage control quantity is obtained by using the first parameter adaptive adjustment formula and the first control quantity output formula; wherein, the first parameter adaptive adjustment formula is: in, , ; As the first parameter, The first initial PD reference parameters are for offline tuning. The first parameter correction value for the fuzzy inference output has a domain of 1. , For the second parameter, The second initial PD reference parameters are tuned offline. The second parameter correction value for the fuzzy inference output has a domain of 1. ; The formula for the first control output is: in, This is the first voltage control quantity. Let be the sampling deviation of the ion current concentration at time t. Let be the rate of change of the deviation at time t; When the deviation is greater than or equal to 0.1V and less than or equal to 0.5V, proportional + integral fuzzy control is activated, using the adaptive adjustment formula for the second parameter and the output formula for the second control quantity: in, , ; As the third parameter, The first initial PI reference parameters are for offline tuning. The third parameter correction value for the fuzzy inference output has a domain of 1. , Four, The second initial PI reference parameter is tuned offline. The fourth parameter correction value for the fuzzy inference output has a domain of 1. ; in, This is the second voltage control quantity. for Sampling deviation of ion current concentration at any given time; Maintain the current voltage when the deviation is less than 0.1V.

[0016] Secondly, this application provides an electron gun cathode protection and beam collimation method for controlling the aforementioned electron gun cathode protection and beam collimation system, comprising: A dynamic positive bias voltage is applied to the collimating aperture, so that the collimating aperture can simultaneously perform the dual functions of physical blocking of metal vapor and deflection of positive ion electric field. The conductive strips in the front and rear collimating lenses are activated to pass negative electricity to adsorb ionized vapor ions, and the first focusing coil is activated to collimate the electron beam. The ion current concentration of the conductive strip is acquired in real time through a sampling resistor and an isolation operational amplifier, and the metal vapor pressure parameters are obtained. The bias voltage of the collimating aperture and the negative bias voltage of the conductive strip are dynamically adjusted using a fuzzy PID algorithm.

[0017] Thirdly, this application provides an electron beam additive manufacturing apparatus, including the aforementioned electron gun cathode protection and beam collimation system.

[0018] The technical solution provided in this application may include the following beneficial effects: This application discloses an electron gun cathode protection and beam collimation system, method, and additive manufacturing equipment. The collimation aperture simultaneously withstands a dynamic positive bias voltage along the electron beam transmission path and uses its aperture wall to form a collimating lens electrode. This allows the same aperture structure to collaboratively perform physical interception of neutral metal vapor, electrostatic lens collimation of the electron beam, and electric field capture of positive ions within the same timescale. This avoids the additional beam scattering and structural redundancy introduced by adding independent collimating lens electrodes or separate apertures, thus ensuring the stability of electron beam transmission while improving integration. The beam parallelism error can be controlled within 0.1 mrad, and the print density can be increased to over 99.5%. Furthermore, by placing a pre-collimating lens between the anode and the collimation aperture and a post-collimating lens on the workpiece-facing side of the collimation aperture, high-energy positive ions are captured at the first focal spot position to block… By preventing back-bombardment of the cathode and removing residual positive ions downstream to eliminate ion oscillation effects, the damage path of ions to the cathode is cut off at the front end, and the beam quality is purified at the back end. The cathode lifespan can be increased to four times that of existing technologies, reaching more than 200 hours. Furthermore, the positive ion concentration is collected in real time by the beam collimation module, and the bias voltage of the collimation aperture and the field strength of the collimation lens are dynamically adjusted according to the concentration using a fuzzy PID algorithm. This allows the system to adaptively adjust the capture electric field and the intensity of the electrostatic lens according to the changes in the amount of positive ions generated during the printing process caused by material switching, beam adjustment, or atmospheric fluctuations. This avoids the sudden drop in protection performance or beam quality degradation of the fixed voltage scheme when switching operating conditions. The adaptability to multiple operating conditions is improved to more than 95%. Stable protection and collimation effects can be maintained without manual parameter adjustment during the printing of materials such as titanium alloys, aluminum alloys, and high-temperature alloys.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0021] Figure 1 This diagram illustrates the structure of the electron gun cathode protection and beam collimation system in an exemplary embodiment of this disclosure. Figure 2 This diagram illustrates the structure of the collimating lens in the electron gun cathode protection and beam collimation system according to an exemplary embodiment of this disclosure. Figure 3This diagram illustrates the structure of the beam collimation module of the electron gun cathode protection and beam collimation system in an exemplary embodiment of this disclosure. Figure 4 This diagram illustrates the simulation results of the beam parallelism of the electron gun cathode protection and beam collimation system in an exemplary embodiment of this disclosure. Figure 5 This diagram illustrates the printing density results of the titanium-aluminum alloy electron gun cathode protection and beam collimation system in an exemplary embodiment of this disclosure. Figure 6 This diagram illustrates the tungsten alloy printing density results of the electron gun cathode protection and beam collimation system in an exemplary embodiment of this disclosure.

[0022] Figure descriptions: 100, Electron gun cathode; 200, Electron gun anode; 300, Collimating aperture; 400, Collimating lens; 410, Front collimating lens; 411, Insulating strip; 412, Conductive strip; 420, Rear collimating lens; 500, Beam collimation module; 510, Sampling resistor; 520, Isolation operational amplifier; 530, Controllable power supply; 600, Ionization gauge; 700, Electro-optics module; 710, Dynamic focusing coil; 720, Aberration correction coil; 730, Second focusing coil; 740, Deflection coil; 800, Workpiece; 900, Powder spreading platform. Detailed Implementation

[0023] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0025] The electron gun is the core component of electron beam additive manufacturing equipment. Its basic structure typically includes an electron gun cathode 100 and an electron gun anode 200. The electron gun cathode 100 emits electrons under electric heating or a high-voltage electric field, forming an electron beam. An accelerating voltage of tens of thousands of volts is applied between the electron gun anode 200 and the electron gun cathode 100, creating a strong accelerating electric field between the cathode and anode. This field accelerates the electrons emitted from the electron gun cathode 100, giving them extremely high kinetic energy and forming a high-energy electron beam. After being emitted from the electron gun cathode 100, the electron beam passes through the accelerating aperture of the electron gun anode 200 and travels downstream along the axis of the electron gun, ultimately reaching the surface of the workpiece for printing.

[0026] This exemplary embodiment first provides an electron gun cathode protection and beam collimation system, referencing... Figure 1 , Figure 2 , Figure 3 As shown, the system may include a collimating aperture 300, a collimating lens 400, and a beam collimation module 500.

[0027] Among them, the collimating aperture 300 has a hole in the middle and is subjected to a dynamic positive bias voltage to form a non-uniform electrostatic field in the hole so that positive ions deviate from the upward path and physically block metal vapor. The collimating lens 400 includes a front collimating lens 410 disposed between the electron gun anode 200 and the collimating aperture 300, and a rear collimating lens 420 disposed on the side of the collimating aperture 300 facing the workpiece 800, for collimating the electron beam and for adsorbing ionized metal vapor ions. The beam collimation module 500 is used to acquire the positive ion current concentration of the collimating lens 400 in real time, and dynamically adjust the positive bias voltage of the collimating aperture 300 and the negative bias voltage of the collimating lens 400 through a fuzzy PID algorithm.

[0028] The above method can simultaneously perform physical interception of neutral metal vapor and electric field deflection of positive ions along the electron beam transmission path by using a positively charged collimating aperture 300. This avoids the additional beam scattering and structural redundancy introduced by adding independent collimating lens electrodes or separate apertures, thus ensuring the stability of electron beam transmission while improving integration. Simultaneously, the focusing coils of the front collimating lens 410 and the rear collimating lens 420 collimate the electron beam, controlling the beam parallelism error to within 0.1 mrad and increasing the print density to over 99.5%. Furthermore, the conductive strips 412 in the front collimating lens 410 and the rear collimating lens 420 are negatively charged to adsorb ionized vapor ions, further preventing... The positive ion reverse-bombardment cathode can increase the cathode lifespan to four times that of existing technologies, reaching over 200 hours. Furthermore, the beam control module 500 collects the ion current concentration in real time and dynamically adjusts the positive bias voltage of the collimation aperture 300 and the negative bias voltage of the conductive strip 412 based on this concentration using a fuzzy PID algorithm. This allows the system to adaptively adjust the deflection electric field and adsorption electric field strength according to changes in the amount of positive ions generated during the printing process caused by material switching, beam adjustment, or atmospheric fluctuations. This avoids the sudden drop in protection performance or beam quality degradation of the fixed voltage scheme when switching operating conditions. The adaptability to multiple operating conditions is improved to over 95%. Stable protection and collimation effects can be maintained without manual parameter adjustment during the printing of materials such as titanium alloys, aluminum alloys, and high-temperature alloys.

[0029] In one embodiment, the dynamic positive bias voltage range of the collimating aperture 300 is 0V to +200V, and is adaptively adjusted based on real-time feedback of the positive ion current concentration and metal vapor pressure.

[0030] It should be noted that the bias voltage range of the collimation aperture 300 is 0V to +200V. This range is dynamically adjusted by the beam collimation module 500 based on the real-time collected positive ion concentration and metal vapor pressure. In this application, different printing conditions correspond to different preferred voltage values. For example, when printing titanium alloys in a helium atmosphere with a beam current of 10mA~15mA, the voltage automatically stabilizes at +80V±5V to simultaneously meet the requirements of ion capture efficiency >95% and beam collimation error <0.1mrad; when printing aluminum alloys with a beam current of 5mA~8mA, the voltage automatically drops to +45V±5V; when using contour scanning technology or printing thin-walled structures with a beam current of 1mA~3mA, the voltage automatically drops to +5V±5V; when preheating the powder bed with a beam current greater than 50mA, the voltage automatically increases to +200V to achieve the maximum positive ion capture effect. The adaptive adjustment of the aforementioned voltage value is achieved through closed-loop control of the beam collimation module 500, aiming to achieve an optimal balance between ion capture efficiency and beam collimation under different operating conditions. The bias voltage of the collimation aperture 300 directly affects the electrostatic lensing effect of the electron beam: when the voltage increases, the focusing intensity of the electrostatic lens increases, the beam divergence decreases, but the capture capability for positive ions also increases accordingly; when the voltage decreases, the focusing intensity of the electrostatic lens weakens, the beam divergence increases, but the capture capability for positive ions weakens. Therefore, closed-loop feedback control is used to adjust the voltage to the optimal value under different operating conditions in real time.

[0031] In one embodiment, the collimating aperture 300 is a molybdenum alloy sheet with a thickness of 0.15mm-0.3mm, and the radius of curvature of the arc at the edge of the aperture is 0.05mm-0.1mm.

[0032] It should be noted that the thickness of the collimating aperture 300 is limited to 0.15mm-0.3mm. This thickness represents the optimal balance between physical strength, electron beam transmittance, and electrostatic field uniformity. If the thickness is too small, the sheet will lack mechanical strength under long-term scouring by high-temperature metal vapor, making it prone to deformation or breakage, and unable to maintain a precise aperture shape and stable electrostatic field distribution. If the thickness is too large, the probability of the electron beam colliding with the aperture wall increases, and the electron beam collision loss rate will exceed 5%, affecting the effective beam energy reaching the workpiece surface and printing efficiency. The aperture edge is electrolytically polished to form a rounded transition with a curvature radius of 0.05mm-0.1mm. The rounded transition makes the equipotential surface distribution around the aperture edge smoother, reducing electric field distortion and thus improving the uniformity of the electrostatic lens field. Compared with the conventional right-angle edge design, the rounded transition can effectively reduce the collision loss rate between the electron beam and the aperture edge, and its loss rate can be controlled below 2%. If the radius of curvature is too small, the arc transition is insufficient, and the improvement in electric field uniformity is limited; if the radius of curvature is too large, the aperture area occupied by the arc edge increases, the equivalent beam channel diameter decreases, and the electron beam transmittance is affected.

[0033] In one embodiment, the front collimating lens 410 and the rear collimating lens 420 are respectively composed of a first focusing coil and an insulating strip 411 and a conductive strip 412 wrapped inside it. The conductive strip 412 is composed of multiple parallel conductive strips stacked at intervals along the electron gun axis. The insulating strip 411 is disposed between the conductive strip 412 and the first focusing coil to insulate and isolate the conductive strip 412 from the first focusing coil. The conductive strip 412 is cylindrical or perforated plate-shaped and is used to pass negative electricity to adsorb ionized metal vapor ions. The first focusing coil is used to collimate the electron beam. The spacing between adjacent conductive strips 412 is 0.5mm-2mm, the material is any one of molybdenum, molybdenum alloy, tungsten or tungsten alloy, the width is 0.5mm-2mm, and the plate thickness is 0.15mm-0.3mm.

[0034] It should be noted that the front collimating lens 410 and the rear collimating lens 420 adopt a composite structure in which an insulating strip 411 and a conductive strip 412 are wrapped inside the first focusing coil. It can be understood that the structures of the front collimating lens 410 and the rear collimating lens 420 are both composite structures in which an insulating strip 411 and a conductive strip 412 are wrapped inside the first focusing coil. Their working principle is as follows: After the focusing coil is energized, it generates an axial magnetic field, which applies a focusing force to the electron beam passing through it, thereby achieving the collimation of the electron beam; after a negative charge is applied to the conductive strip 412, a negative potential region is formed around it. When ionized positive ions enter this region, they are attracted by electrostatic attraction and adsorbed to the surface of the conductive strip 412, thereby being removed from the beam; the insulating strip 411 electrically isolates the conductive strip 412 from the focusing coil, preventing the negative voltage of the conductive strip 412 from interfering with the excitation voltage of the coil. The width and thickness of the conductive strip 412 affect its adsorption area and mechanical strength: if the width is too small, the adsorption area is insufficient, and the ion removal efficiency decreases; if the width is too large, it will occupy too much beam channel space and increase the probability of electron beam scattering. The conductive strip 412 is made of refractory metals such as molybdenum, molybdenum alloy, tungsten, or tungsten alloy because these materials have extremely low vapor pressure at high temperatures, will not volatilize in the high-temperature working environment of the electron gun and cause secondary pollution, and also have good conductivity and processing performance.

[0035] In one embodiment, the electron gun cathode protection and beam collimation system further includes an ionization gauge 600, disposed inside the electron gun, for collecting the pressure of the metal vapor volatilized into the electron gun; the beam collimation module 500 performs feedforward compensation based on the metal vapor pressure. When the metal vapor pressure is greater than 0.1 Pa, the voltage of the collimating aperture 300 is increased to +80 V to enhance the electrostatic lens effect; When the metal vapor pressure is <0.05Pa, the voltage of the collimating aperture 300 is reduced to +50V to avoid over-focusing of the beam spot.

[0036] It should be noted that increasing the voltage of the collimating aperture 300 to +80V to enhance the electrostatic lens effect can increase the field strength of the front collimating lens 410 by about 15%; decreasing the voltage of the collimating aperture 300 to +50V to avoid excessive beam focusing can reduce the field strength of the front collimating lens 410 by about 10%.

[0037] The ionization gauge 600 is located inside the electron gun, and the value of the metal vapor pressure it collects reflects the potential risk of metal vapor contamination of the cathode within the electron gun. The beam collimation module 500 performs feedforward compensation based on this metal vapor pressure. Feedforward compensation differs from feedback control: feedback control adjusts only after the ion current concentration changes; feedforward control adjusts in advance based on the trend of vapor pressure changes, before the ion current concentration changes significantly. When the metal vapor pressure is too high, it indicates that a large amount of metal vapor has been generated during the printing process, and the electron gun faces a high risk of contamination. In this case, the voltage of the collimation aperture 300 is increased to enhance the electrostatic lens effect, allowing the electron beam to pass through the contaminated area more quickly. At the same time, the field strength of the pre-collimating lens 410 is increased to enhance the ion capture capability. When the metal vapor pressure is too low, it indicates that the atmospheric environment is relatively clean. The voltage is reduced to avoid over-focusing of the beam spot, and the field strength of the pre-collimating lens 410 is reduced to decrease energy consumption.

[0038] In one embodiment, the beam collimation module 500 includes a sampling resistor 510, an isolation operational amplifier 520, and a controllable power supply 530; The sampling resistor 510 is connected in series at the low-voltage end of the power supply circuit of the front collimating lens 410 and the rear collimating lens 420, and is used to convert the ion current into a voltage drop. The isolation operational amplifier 520 has its input terminal connected to both ends of the sampling resistor 510 and its output terminal connected to the control terminal of the controllable power supply 530. It is used to amplify and level-convert the floating high-voltage side signal across the sampling resistor 510, converting it into a grounded measurable signal. The output terminal of the controllable power supply 530 is connected to the collimating aperture 300, and is used to apply a dynamic positive bias voltage to the collimating aperture 300 based on the measurable signal and through the fuzzy PID algorithm.

[0039] It should be noted that the beam collimation module 500 consists of a sampling resistor 510, an isolation operational amplifier 520, and a controllable power supply 530. Its signal flow is as follows: the front collimating lens 410 and the rear collimating lens 420 are grounded at a low potential, while the collimating aperture 300 is grounded at a high potential. The sampling resistor 510 is connected in series at the low-voltage end of the high-voltage power supply circuit of the front collimating lens 410 and the rear collimating lens 420, i.e., between the negative terminal of the collimating aperture 300 and ground. Its principle is to convert the ion current generated when the collimating lens captures positive ions into a voltage drop, which is linearly proportional to the ion current (U=I×R). The magnitude of the ion current reflects the concentration of captured positive ions, and the positive ion concentration reflects the degree of ionization caused by the collision between the electron beam and residual gas molecules, as well as the level of metal vapor contamination. The sampling resistor 510 uses a high-precision metal film resistor, whose accuracy and low temperature drift characteristics ensure that the converted voltage signal has good linearity and consistency.

[0040] The resistance value of sampling resistor 510 is designed according to the expected ion current range to ensure accurate and measurable voltage drop across the entire range. Isolation operational amplifier 520 is a high-isolation operational amplifier, with its input connected to both ends of sampling resistor 510, used to acquire the differential-mode voltage signal across sampling resistor 510. The principle is that although sampling resistor 510 is located at the low-voltage end of the power supply circuit, this circuit section is still electrically connected to the high-voltage power supply circuit of the collimating lens. Therefore, isolation operational amplifier 520 is needed to achieve electrical isolation between the high-voltage side and the low-voltage control circuit side to prevent the common-mode voltage on the high-voltage side from damaging the subsequent low-voltage control circuit. Isolation operational amplifier 520 amplifies the differential-mode voltage signal across sampling resistor 510 and simultaneously performs level conversion, converting the signal floating at the high-voltage side ground potential into a measurable signal relative to the system ground potential. The controllable power supply 530's control terminal receives the measurable signal amplified and level-converted by isolation operational amplifier 520, and its output terminal is connected to collimating aperture 300. The controllable power supply 530 dynamically adjusts its output voltage according to the control signal, thereby achieving precise and continuous adjustment of the bias voltage of the alignment aperture 300.

[0041] In one embodiment, the electron gun cathode protection and beam collimation system further includes: an electron optics module 700 for focusing, aberration correction, and deflection scanning of the electron beam; the electron optics module includes: A dynamic focusing coil 710 is disposed after the rear collimating lens 420 and is used to receive the parallel electron beam collimated by the rear collimating lens 420. The parallel electron beam is first focused by the focusing current to form a first working focal spot acting on the workpiece. The dynamic focusing coil adjusts the focusing current in real time according to the deflection state of the deflection coil to compensate for the focal shift caused by the deflection of the electron beam. An aberration correction coil 720 is disposed after the dynamic focusing coil 710 and is used to perform feedforward pre-correction of electron beam aberration caused by the deflection coil 740 according to the preset deflection state of the deflection coil 740. The second focusing coil 730 is disposed after the aberration correction coil 720 and is used to perform a second-stage focusing on the corrected electron beam to form a second working focal spot acting on the workpiece. The deflection coil 740 is disposed after the second focusing coil 730 and is used to deflect the second working focal spot to realize the scanning action.

[0042] It should be noted that the dynamic focusing coil 710 is a strong focusing coil, located between the rear collimating lens 420 and the aberration correction coil 720. It receives the parallel electron beam collimated by the rear collimating lens 420 and performs a first-stage focusing on the parallel electron beam using a focusing current to adjust the beam diameter and divergence angle, providing the aberration correction coil 720 with a beam state that meets the incident requirements. The aberration correction coil 720 is located after the dynamic focusing coil 710 and performs feedforward pre-correction of the electron beam aberrations caused by the deflection coil 740 based on the preset deflection state of the deflection coil 740. The second focusing coil 730 is located after the aberration correction coil 720 and performs a second-stage focusing on the collimated and aberration corrected electron beam, forming a working focal spot acting on the workpiece 800. The first-stage focusing and second-stage focusing serve different functional requirements: the first-stage focusing is used to moderately compress and shape the electron beam passing through the rear collimating lens 420 to match the optimal incident parameters of the aberration correction coil 720 and improve the aberration correction effect; the second-stage focusing is used to obtain a suitable beam spot size and energy density for printing on the workpiece surface. A deflection coil 740 is positioned after the second focusing coil 730, and by applying a controllable magnetic field, it deflects the focused electron beam on the surface of the workpiece 800 to achieve the scanning action.

[0043] In one embodiment, the fuzzy PID algorithm includes a fuzzification unit, a fuzzy rule base, a defuzzification unit, and a segmented control strategy. The fuzzification unit is used to convert the real-time acquired deviation and deviation change rate into a fuzzy set, where the universe of discourse of the deviation is... The universe of discourse for the rate of change of deviation is The corresponding fuzzy sets are all The triangular membership function is used. The fuzzy rule base is used for fuzzy reasoning based on the rule table; The deblurring unit is used to convert the fuzzy output into a precise voltage adjustment amount using the centroid method; the voltage adjustment amount formula is: in, For voltage regulation, The membership degree of a fuzzy set. The precise value corresponding to the fuzzy set; The segmented control strategy is as follows: When the deviation is greater than 0.5V and the rate of change of deviation does not exceed 0.5V / s, the voltage regulation amount of the proportional element is obtained through the proportional element formula; the proportional element formula is: in, This is the voltage regulation amount of the proportional element. This is the proportionality coefficient. For deviation; When the deviation is greater than 0.5V and the rate of change of the deviation is greater than 0.5V / s, proportional + derivative fuzzy control is activated. The first voltage control quantity is obtained by using the first parameter adaptive adjustment formula and the first control quantity output formula; wherein, the first parameter adaptive adjustment formula is: in, , ; As the first parameter, The first initial PD reference parameters are for offline tuning. The first parameter correction value for the fuzzy inference output has a domain of 1. , For the second parameter, The second initial PD reference parameters are tuned offline. The second parameter correction value for the fuzzy inference output has a domain of 1. ; The first control output formula is: in, This is the first voltage control quantity. Let be the sampling deviation of the ion current concentration at time t. Let be the rate of change of the deviation at time t; When the deviation is greater than or equal to 0.1V and less than or equal to 0.5V, proportional + integral fuzzy control is activated, using the adaptive adjustment formula for the second parameter and the output formula for the second control quantity: in, , ; As the third parameter, The first initial PI reference parameters are for offline tuning. The third parameter correction value for the fuzzy inference output has a domain of 1. , Four, The second initial PI reference parameter is tuned offline. The fourth parameter correction value for the fuzzy inference output has a domain of 1. ; in, This is the second voltage control quantity. for Sampling deviation of ion current concentration at any given time; Maintain the current voltage when the deviation is less than 0.1V.

[0044] It should be noted that the rule table is as follows: Table 1 Rules Table The core design principle is the "if-then" rule, which covers all combinations of fuzzy sets.

[0045] The fuzzy PID algorithm in this application is not a simple piecewise PID, but rather includes a complete fuzzy logic reasoning framework. The fuzzification unit maps the precise deviation and deviation change rate to a fuzzy set through a triangular membership function. For example, when... At that time, it was in "positive small (PS)" and " The two fuzzy sets have different membership degrees. The fuzzy rule base is based on the experience of domain experts and a large amount of experimental data, covering all combinations of deviation and deviation change rate. For example, when the deviation is "negative large (NB)" and the change rate is "negative large (NB)", the rule output is "positive large (PB)", indicating that the voltage needs to be increased significantly. The defuzzification unit uses the centroid method to perform a weighted average of all activated rule outputs to obtain a precise voltage adjustment amount, thereby achieving smooth and continuous adjustment of the protective light barrier bias voltage.

[0046] The segmented control strategy is finely designed to meet the control requirements under different operating conditions: when the deviation is large but the rate of change is small... This indicates that the system is in a state of large steady-state deviation, and proportional control is used to achieve a fast response; when the deviation is large and the rate of change is drastic... This indicates that the system is facing sudden disturbances (such as a sudden increase in metal vapor caused by rapid switching of printing materials). In this case, proportional + derivative fuzzy control is activated. The predictive nature of the derivative element is used to suppress overshoot, while fuzzy inference is used to adjust the system in real time. and Parameters, implementation Adaptive optimization of parameters; when the deviation is moderate When the system approaches steady state, proportional-integral fuzzy control is activated. The integral element is used to eliminate static errors, and fuzzy inference is used to adjust the system in real time. and Parameters are used to ensure steady-state accuracy; when the deviation is extremely small. The system has entered a steady state. Maintain the current voltage or make minor adjustments based on the sign of the deviation to avoid frequent adjustments that could cause system oscillations.

[0047] Through the complete fuzzy PID algorithm described above, the system of this application can achieve optimal control performance under all operating conditions, including large deviation, rapid change, small deviation, and steady state, realizing true adaptive control and achieving multi-condition adaptability. above.

[0048] Furthermore, the design of fuzzy unit includes fuzzy universe partitioning, membership function mapping, and linguistic variable mapping. The fuzzy domain is divided into: deviation The universe of discourse of U is [-2V, +2V], and the corresponding fuzzy set is {negative large (NB), negative medium (NM), negative small (NS), zero (ZO), positive small (PS), positive medium (PM), positive large (PB)}; Deviation change rate d The universe of discourse for U / dt is [-1V / s, +1V / s], which corresponds to the fuzzy set and the bias.

[0049] The membership function is: a triangular membership function is used, with deviation... For example, U: Negative (NB): [-2V, -1V], peak value at -2V; Negative Midpoint (NM): [-1.5V, -0.5V], peak value at -1V; Zero (ZO): [-0.2V, +0.2V], peak value at 0V; Zhengda (PB): [+1V, +2V], with a peak value at +2V.

[0050] Language variable mapping: mapping precise values ​​collected in real time (such as...) U = +0.8V) is mapped to a fuzzy set.

[0051] In the design of the supplementary defuzzification unit, the defuzzification method is as follows: the centroid method (area center method) is used to convert the fuzzy output set into a precise voltage regulation amount. V; When multiple rules are triggered simultaneously, a weighted average method is used to calculate the final output based on the rule priority.

[0052] Furthermore, this example embodiment also provides performance experimental data for the electron gun cathode protection and beam collimation system: like Figure 4 As shown, by adjusting the current of the matching collimating lens, the beam is focused through the aperture and forms a parallel beam. Simulation calculations and experiments show that the beam parallelism (0.06 mrad) can be controlled within 0.1 mrad.

[0053] like Figure 5 and Figure 6As shown, the printing density is improved to 99.5% by using cathodic protection-beam stabilization, collimation-electron beam with good quality, and stable forming, melting and solidification process, thus improving the printing density. Currently, the printing density of titanium alloy TC4, 316 stainless steel, copper alloy, especially refractory and brittle materials such as titanium-aluminum alloy and tungsten is better than 99.5%.

[0054] Meanwhile, without the cathode protection and beam collimation of this application, the cathode fails due to ion back-bombardment, and its lifespan is usually less than 40 hours. With the adoption of this application, ion back-bombardment is basically eliminated, and the cathode surface remains flat and bright with good emission characteristics even after 200 hours. Currently, the lifespan of the cathode assembly is limited to 200 hours due to the filament lifespan.

[0055] Furthermore, the adaptability to various working conditions is improved to over 95%. This application is applicable to printing on most materials and under different working conditions, including titanium alloys, copper alloys, high-strength steel, intermetallic compounds (TiAl), and refractory materials (tungsten, molybdenum, tantalum, niobium).

[0056] Furthermore, this exemplary embodiment also provides an electron gun cathode protection and beam collimation method for controlling the above-mentioned electron gun cathode protection and beam collimation system, including: A dynamic positive bias voltage is applied to the collimating aperture 300, so that the collimating aperture 300 can simultaneously perform the dual functions of physical blocking of metal vapor and deflection of positive ion electric field. The conductive strips 412 in the front collimating lens 410 and the rear collimating lens 420 are activated to pass negative electricity to adsorb ionized vapor ions, and the first focusing coil is activated to collimate the electron beam. The ion current concentration of the conductive strip 412 is collected in real time by sampling resistor 510 and isolation operational amplifier 520, and the metal vapor pressure parameters are obtained. The bias voltage of the collimating aperture 300 and the negative bias voltage of the conductive strip 412 are dynamically adjusted by a fuzzy PID algorithm.

[0057] It should be noted that the above steps can be performed simultaneously or in an overlapping sequence. For example, applying a dynamic positive bias voltage to the collimating aperture 300 and activating the front collimating lens 410 and the rear collimating lens 420 can be performed simultaneously during the startup phase; the real-time acquisition of positive ion current concentration through the sampling resistor 510 and the isolation operational amplifier 520 is a continuous process that runs throughout the entire printing process.

[0058] The collimating aperture 300 performs dual functions simultaneously based on the same physical structure and at the same time, rather than working in a time-division manner. This creates a synergistic effect, unlike existing technologies where multiple independent components perform a single function. The conductive strip 412 in the front collimating lens 410 and the rear collimating lens 420 involves applying a preset negative voltage to the conductive strip 412, thereby establishing a negative potential region around it capable of attracting positive ions; simultaneously, it activates the focusing coil, causing it to generate an axial magnetic field to collimate the electron beam. The activation parameters of the two collimating lenses can be set separately according to their respective positions and working conditions. For example, the front collimating lens 410 is close to the electron gun anode 200, and the ion energy in its working environment may be higher; the rear collimating lens 420 is close to the workpiece 800, and the ion energy in its working environment may be lower. Specific activation parameters can be conventionally set by those skilled in the art based on actual working conditions.

[0059] Furthermore, this example embodiment also provides an electron beam additive manufacturing apparatus, including the aforementioned electron gun cathode protection and beam collimation system.

[0060] It should be noted that the electron beam additive manufacturing equipment includes, but is not limited to, an electron gun system, a vacuum chamber, a powder spreading platform 900, a vacuum system, and related control software and hardware systems. The workpiece 800 is placed on the powder spreading platform 900. The electron gun cathode protection and beam collimation system, as a core component of the electron gun system, works in conjunction with the aforementioned systems. During equipment operation, the electron gun cathode protection and beam collimation system operates continuously, monitoring the positive ion concentration and metal vapor pressure in real time throughout the printing process, and dynamically adjusting the bias voltage of the collimation aperture 300 to ensure stable cathode protection and beam quality under different printing materials and process parameters. This equipment is suitable for additive manufacturing of conductive powder materials such as titanium alloys, aluminum alloys, and high-temperature alloys.

[0061] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. An electron gun cathode protection and beam collimation system, characterized in that, include: The collimating aperture has a hole in the middle and is subject to a dynamic positive bias voltage to create a non-uniform electrostatic field in the hole to deflect positive ions from their upward path and physically block metal vapor. The collimating lens includes a front collimating lens disposed between the electron gun anode and the collimating aperture, and a rear collimating lens disposed on the side of the collimating aperture facing the workpiece, for collimating the electron beam and for adsorbing ionized metal vapor ions. The beam collimation module is used to acquire the positive ion current concentration of the collimating lens in real time, and dynamically adjust the positive bias voltage of the collimating aperture and the negative bias voltage of the collimating lens through a fuzzy PID algorithm.

2. The electron gun cathode protection and beam collimation system according to claim 1, characterized in that, The dynamic positive bias voltage range of the collimating aperture is 0V to +200V, and it is adaptively adjusted according to the real-time feedback of the positive ion concentration and the metal vapor pressure.

3. The electron gun cathode protection and beam collimation system according to claim 1, characterized in that, The collimating aperture is a thin molybdenum alloy sheet with a thickness of 0.15mm-0.3mm, and the radius of curvature of the arc at the edge of the aperture is 0.05mm-0.1mm.

4. The electron gun cathode protection and beam collimation system according to claim 1, characterized in that, The front collimating lens and the rear collimating lens are respectively composed of a first focusing coil and an insulating strip and a conductive strip wrapped inside it. The conductive strip is composed of multiple parallel conductive strips stacked at intervals along the axis of the electron gun. The insulating strip is disposed between the conductive strip and the first focusing coil to insulate and isolate the conductive strip from the first focusing coil. The conductive strip is cylindrical or perforated plate-shaped and is used to pass a negative charge to adsorb ionized metal vapor ions. The first focusing coil is used to collimate the electron beam. The spacing between adjacent conductive strips is 0.5mm-2mm, the material is any one of molybdenum, molybdenum alloy, tungsten or tungsten alloy, the width is 0.5mm-2mm, and the plate thickness is 0.15mm-0.3mm.

5. The electron gun cathode protection and beam collimation system according to claim 2, characterized in that, It also includes an ionization gauge, located inside the electron gun, for collecting the pressure of the metal vapor that evaporates into the electron gun; the beam collimation module performs feedforward compensation based on the metal vapor pressure. When the metal vapor pressure is greater than 0.1 Pa, the voltage of the collimating aperture is increased to +80 V to enhance the electrostatic lens effect; When the metal vapor pressure is <0.05Pa, the voltage of the collimating aperture is reduced to +50V to avoid over-focusing of the beam spot.

6. The electron gun cathode protection and beam collimation system according to claim 1, characterized in that, The beam collimation module includes a sampling resistor, an isolation operational amplifier, and a controllable power supply; The sampling resistor is connected in series at the low-voltage end of the power supply circuit of the front collimating lens and the rear collimating lens, and is used to convert the ion current into a voltage drop. The isolated operational amplifier has its input terminal connected to both ends of the sampling resistor and its output terminal connected to the control terminal of the controllable power supply. It is used to amplify and level-convert the floating high-voltage side signal across the sampling resistor, converting it into a grounded measurable signal. The output terminal of the controllable power supply is connected to the collimating aperture, and is used to apply a dynamic positive bias voltage to the collimating aperture based on the measurable signal and through the fuzzy PID algorithm.

7. The electron gun cathode protection and beam collimation system according to claim 1, characterized in that, Also includes: Electro-optics module, used for focusing, aberration correction and deflection scanning of electron beam; The electro-optical module includes: A dynamic focusing coil is positioned after the rear collimating lens to receive the parallel electron beam collimated by the rear collimating lens. The parallel electron beam is then focused in the first stage by a focusing current to form a first working focal spot acting on the workpiece. An aberration correction coil is disposed after the dynamic focusing coil and is used to perform feedforward pre-correction of electron beam aberrations caused by the deflection coil according to the preset deflection state of the deflection coil. The second focusing coil is disposed after the aberration correction coil and is used to perform a second-stage focusing on the corrected electron beam to form a second working focal spot acting on the workpiece. A deflection coil, located after the second focusing coil, is used to deflect the second working focal spot to achieve the scanning action.

8. The electron gun cathode protection and beam collimation system according to claim 2, characterized in that, The fuzzy PID algorithm includes a fuzzification unit, a fuzzy rule base, a defuzzification unit, and a piecewise control strategy. The fuzzification unit is used to convert the real-time acquired deviation and deviation change rate into a fuzzy set, where the universe of discourse of the deviation is... The universe of discourse for the rate of change of deviation is The corresponding fuzzy sets are all The triangular membership function is used. The fuzzy rule base is used for fuzzy reasoning based on the rule table; The deblurring unit is used to convert the fuzzy output into a precise voltage adjustment amount using the centroid method; the voltage adjustment amount formula is: in, For voltage regulation, The membership degree of a fuzzy set. The precise value corresponding to the fuzzy set; The segmented control strategy is as follows: When the deviation is greater than 0.5V and the rate of change of deviation does not exceed 0.5V / s, the voltage regulation amount of the proportional element is obtained through the proportional element formula; the proportional element formula is: in, This is the voltage regulation amount of the proportional element. This is the proportionality coefficient. For deviation; When the deviation is greater than 0.5V and the rate of change of the deviation is greater than 0.5V / s, proportional + derivative fuzzy control is activated. The first voltage control quantity is obtained by using the first parameter adaptive adjustment formula and the first control quantity output formula; wherein, the first parameter adaptive adjustment formula is: in, , ; As the first parameter, The first initial PD reference parameters are for offline tuning. The first parameter correction value for the fuzzy inference output has a domain of 1. , For the second parameter, The second initial PD reference parameters are tuned offline. The second parameter correction value for the fuzzy inference output has a domain of 1. ; The formula for the first control output is: in, This is the first voltage control quantity. Let be the sampling deviation of the ion current concentration at time t. Let be the rate of change of the deviation at time t; When the deviation is greater than or equal to 0.1V and less than or equal to 0.5V, proportional + integral fuzzy control is activated, using the adaptive adjustment formula for the second parameter and the output formula for the second control quantity: in, , ; As the third parameter, The first initial PI reference parameters are for offline tuning. The third parameter correction value for the fuzzy inference output has a domain of 1. , Four, The second initial PI reference parameter is tuned offline. The fourth parameter correction value for the fuzzy inference output has a domain of 1. ; in, This is the second voltage control quantity. for Sampling deviation of ion current concentration at any given time; Maintain the current voltage when the deviation is less than 0.1V.

9. A method for cathode protection and beam collimation of an electron gun, characterized in that, For controlling the electron gun cathode protection and beam collimation system as described in any one of claims 1 to 8, comprising: A dynamic positive bias voltage is applied to the collimating aperture, so that the collimating aperture can simultaneously perform the dual functions of physical blocking of metal vapor and deflection of positive ion electric field. The conductive strips in the front and rear collimating lenses are activated to pass negative electricity to adsorb ionized vapor ions, and the first focusing coil is activated to collimate the electron beam. The ion current concentration of the conductive strip is acquired in real time through a sampling resistor and an isolation operational amplifier, and the metal vapor pressure parameters are obtained. The bias voltage of the collimating aperture and the negative bias voltage of the conductive strip are dynamically adjusted using a fuzzy PID algorithm.

10. An electron beam additive manufacturing apparatus, characterized in that, Includes the electron gun cathode protection and beam collimation system as described in any one of claims 1 to 8.

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