概述 电子束熔化
Electron beam melting (EBM) is an additive manufacturing process that uses an electron beam power source to selectively melt and fuse metallic powder material layer-by-layer to build up components.
Some key details about electron beam melting include:
- Uses an electron beam gun under vacuum to melt the powder.
- Builds occur at high temperatures, enabling good interlayer bonding.
- Primarily used for Ti, Ni, Co alloys, and other high performance materials.
- Provides near-full density parts with properties equaling or exceeding traditionals means.
- Supports complex geometries not feasible by conventional fabrication.
- Commonly used in aerospace, medical, and automotive industries.
- Also referred to as electron beam additive manufacturing (EBAM) or electron beam freeform fabrication (EBF3).
电子束熔化设备
| 类型 | 说明 |
|---|---|
| Electron beam gun | Generates and focuses high energy beam to melt the material. Key component. |
| Powder bed | Contains powder layers raked by blades or rollers. Built on a movable platform. |
| 真空室 | Entire system is under vacuum during builds. Critical for beam focus. |
| 控制系统 | Software slices and controls build parameters. Provides in-process monitoring and control. |
| Handling system | For loading/unloading parts and recycling unused powder. |
| Shielding | Lead shielding required around chamber due to x-ray generation. |
Materials Used in 电子束熔化
| 材料 | 主要特性 | 典型应用 |
|---|---|---|
| 钛合金 | 高强度重量比、生物相容性 | 航空航天、医疗植入物 |
| 镍合金 | 耐腐蚀、高强度 | Turbines, rocket components |
| 钴铬合金 | Hardness, wear/corrosion resistance | Medical implants, tooling |
| 不锈钢 | Good durability, easier processing | Industrial tooling, molds |
| 铝合金 | Low weight | 航空航天、汽车 |
| 贵金属 | Highly chemically inert | Jewelry, medical |
EBM can process high-performance alloys difficult with laser-based processes due to power intensity.
EBM Process Specifications
| 参数 | 典型范围 |
|---|---|
| 光束功率 | 1-3 kW |
| Beam voltage | 30-150 千伏 |
| Build size | 200 x 200 x 350 mm max |
| 层高 | 50-200 μm |
| 建造速度 | 5-100 cm3/hr |
| 光束尺寸 | 0.1-1 mm diameter |
| 真空度 | 5 x 10-4 mbar |
| 光束聚焦 | 0.1-0.5 mm spot size |
EBM systems allow adjusting parameters like beam power, speed, focus etc. to tune for specific materials.
Suppliers of EBM Systems
| 供应商 | Key Details | Starting Price Range |
|---|---|---|
| 供应商 1 | Pioneer of EBM technology. Largest installed base. | $1.2-$1.5 million |
| 供应商 2 | Systems for smaller parts. Faster scan speeds. | $0.8-$1.2 million |
| 供应商 3 | Research systems. Open parameters control. | $0.5-$0.8 million |
System costs vary based on build volume, beam power, included accessories and software capabilities.
How to Choose an EBM System Supplier
When selecting an EBM system supplier, key factors to consider include:
- 技术专长 – Supplier should have in-depth knowledge of electron beam physics, metallurgy, and process experience.
- Proven technology – Look for well-established suppliers with a track record of successful system installations.
- Application experience – Supplier should understand client application needs and recommend appropriate system specifications.
- System reliability – Choose suppliers known for engineering robust EBM systems with reasonable uptimes and service intervals.
- 控制软件 – Supplier should offer user-friendly software for programming, monitoring, and optimizing builds.
- 技术支持 – Look for responsive support engineers to troubleshoot issues and help improve process outcomes.
- Training – Supplier should provide comprehensive training on equipment operation, maintenance, and safety.
- Future roadmap – Select a supplier investing in ongoing EBM innovations for your long-term needs.
How to Optimize the EBM Process
To achieve high quality EBM printed parts, follow these process optimization best practices:
- Start with high purity spherical powder feedstock tailored for EBM. Handling, storage, and reuse of powder also crucial.
- Take time to calibrate the electron beam profile and focus. Beam shaping can further improve density.
- Dial in optimal beam current and scanning speed for stable, homogeneous melting.
- Adjust beam focus dynamically during builds to account for geometry changes.
- Set hot bed temperature over 700°C to reduce residual stresses and avoid cracking.
- Tune parameters separately for contours vs. hatch regions to improve surface finish and resolution.
- Optimize support structures to minimize while still providing enough anchoring and heat dissipation.
- Account for parameter differences between various materials – titanium alloy settings differ from nickel superalloys, for example.
- Take an iterative, empirical approach – run test builds while varying parameters to find the sweet spots.
How to Design Parts for EBM
To successfully design components suited to the EBM process:
- Design walls thicker than 0.4 mm to ensure full melting and prevent cracking.
- Include a 5-15° draft angle on surfaces angled in the build direction to aid powder removal.
- Minimize unsupported overhangs to reduce sagging and defects on downward facing surfaces.
- Incorporate lattices and conformal cooling channels enabled by EBM’s design freedom.
- Consolidate sub-assemblies into single parts to improve quality and reduce processing steps.
- Position parts in build chamber to minimize support requirements and avoid collisions during raking.
- Account for 20-50% lower mechanical strength horizontally vs vertically due to layer-based construction.
- Allow an additional stock of 0.5-1mm for post-processing like surface machining or grinding.
Work closely with EBM machine operators during part design iterations to leverage their process knowledge.
How to Post-Process EBM Parts
Typical post-processing steps for EBM printed components include:
- 支持移除 – Carefully remove support structures, if any, by hand or using cutting tools.
- 缓解压力 – Heat treat at 600-800°C for 1-3 hours to relieve residual stresses.
- 加工 – CNC milling, turning, drilling to improve dimensional accuracy and surface finish.
- 磨削 – Automated or manual grinding brings precision tolerances and finer finishes.
- 抛光 – Yields excellent surface finish free of any adhered powder particles.
- 涂料 – Apply functional coatings for hardness, wear resistance, electrical insulation etc.
- 热等静压（HIP） – Closes internal voids and further improves fatigue performance.
- 加入 – Integrate features like threaded holes, fasteners etc. using suitable techniques.
Post-process EBM parts using qualified operators with experience handling the specific alloy composition.
How to Install and Integrate EBM 部件
When preparing EBM printed parts for integration into final products:
- 彻底清洁表面，去除松散粉末和氧化物。适当的清洁可提高粘合效果。
- 根据需要涂上保护层--硬质阳极氧化、电镀、喷漆等，以加强防腐和耐磨保护。
- 将 EBM 部件与其他金属部件连接时，应考虑热膨胀差异，以避免产生应力。
- 选择适合材料的连接技术--焊接、机械紧固、粘合剂等。
- 焊接或钎焊时使用热管理--预热和控制冷却速度。
- 通过原型设计和测试，验证组件在运行负载和环境下的功能。
- 使用 X 射线、UT、渗透测试等技术检查缺陷，这对高责任应用至关重要。
在集成 EBM 部件时，与设计师和工程师并肩工作，确保最终装配的稳健和优化性能。
操作和维护 EBM 打印机
保持 EBM 打印机的最佳运行状态，防止停机：
- 根据供应商的指导原则进行定期预防性维护 - 更换磨损的部件，如防护罩。
- 使用校准方法定期检查光束的 x-yz 精确度。必要时重新校准。
- 检查真空系统的关键部件 - 泄漏检查密封件、监控泵、定期更换过滤器。
- 按规定的时间间隔校准集成过程监控传感器。
- 持续监控真空质量 - 发现并立即纠正任何泄漏。
- 遵循建议的清洁程序 - 保持构建室和粉末处理系统清洁。
- 只允许合格的技术人员维修高压电束电源和喷枪。
- 备有防护罩、泵、过滤器等备件/易损件，以尽量减少停机时间。
在低产量期间安排停机维护。在两次构建之间主动监控 EBM 系统的健康状况。
的利弊 电子束熔化
与传统制造方法相比，电子束熔化既有优势也有局限性：
优势
- 制造其他方法无法制造的复杂几何形状。
- 将子组件合并为单一部件。
- 减少浪费--只使用所需的材料。
- 缩短新设计的开发时间。
- 性能等同或超过传统的铸造方法。
- 不需要粘合剂或额外的支撑，材料更纯净。
缺点
- 产量低时，每个部件的成本较高。
- 尺寸限制基于构建腔体。
- 与其他 AM 工艺相比，材料选择有限。
- 通常需要进行后期处理，以获得最终部件。
- 各向异性特性是由基于层的结构造成的。
- 需要为电子束输入大量功率。
在权衡 EBM 与传统方法时，应考虑数量、尺寸、属性、准备时间和成本。EBM 适用于复杂、高性能的金属零件，但设置成本较高。
常见问题
问：使用 EBM 可以加工哪些材料？
答：迄今为止，主要是钛、镍、钴和不锈钢合金。研究正在扩大材料的选择范围，包括铝、工具钢、金、钽等。
问：EBM 和选择性激光熔化 (SLM) 的主要区别是什么？
答：EBM 使用电子束能源，而 SLM 使用激光。EBM 可实现更高的光束功率密度，从而可以加工更多的难熔金属。
问：哪些行业使用 EBM 印刷？
答：迄今为止，航空航天是涡轮叶片等部件的最大用户。但医疗、汽车和工业领域的 EBM 用户也在不断增加。
问：EBM 是生产多孔部件还是全致密部件？
答：在最佳参数下，EBM 可以达到超过 99% 的密度。高温可改善层间的扩散结合。
问：使用 EBM 可以制作多大尺寸的零件？
答：最大尺寸受制于制造包络面，通常约为 250 x 250 x 300 毫米。目前正在开发更大的系统，目标是 500 毫米的立方体。
问：与 CNC 加工相比，EBM 的精度如何？
答：如果校准良好，EBM 可以达到 0.1-0.3 毫米的公差。但要达到 0.05 毫米以下的更小公差，则需要进行机加工。
问：EBM 有哪些主要优势？
答：与传统制造相比，设计自由、部件整合、快速原型制造、高强度合金、减少浪费和缩短交付周期。
问： EBM 需要采取哪些安全预防措施？
答：EBM 系统会产生 X 射线辐射，因此对构建室进行充分的铅屏蔽至关重要。只有经过培训的人员才能操作。
