课程：MA6502 Fundamentals & Advances in Additive Manufacturing（南洋理工大学 NTU） 来源 PDF：

• MA6502 2022-2023 Semester 2（April/May 2023）
• MA6502 2023-2024 Semester 2（April/May 2024）

两份均为 闭卷考试，时间 3 小时，含 4 道必答大题，每题含若干小问。

一、整体对比 / Overall Comparison

两套试卷的 共同知识骨架：七大 AM 工艺族原理 → 粉末/耗材特性 → 工艺选型与应用场景 → 后处理与质量 → 混合制造与新兴技术。

The shared knowledge backbone of the two papers is: principles of the seven AM process families → powder/feedstock properties → process selection and application scenarios → post-processing and quality → hybrid manufacturing and emerging technologies.

二、2023-2024 Semester 2（April/May 2024） / 2023-2024 Semester 2 Paper

Q1. 3D 打印敏捷性 + EBM + SLM（25 分） / 3D Printing Agility + EBM + SLM (25 marks)

• (a) 3D 打印赋能制造敏捷性的 3 个关键优势（6 分） / Three key advantages of 3D printing for manufacturing agility (6 marks)
• (b) 医疗植入体为何选 EBM 而非其他 3D 打印工艺（5 分） / Why EBM is selected for medical implants rather than other 3D printing processes (5 marks)
• (c) EBM 的 2 个局限（4 分） / Two limitations of EBM (4 marks)
• (d) 解释 SLM 工艺（含图）（10 分） / Explain the SLM process with a diagram (10 marks)

Q2. 粉末流动性 + LMD + DED vs PBF（25 分） / Powder Flowability + LMD + DED vs PBF (25 marks)

• (a) 影响 PBF 粉末流动性的 3 个因素（6 分） / Three factors affecting PBF powder flowability (6 marks)
• (b) 粉末基 LMD（Laser Metal Deposition） 工艺（含图）（10 分） / Powder-based LMD (Laser Metal Deposition) process with a diagram (10 marks)
• (c) DED 相较 PBF 的 3 个独特优势（9 分） / Three unique advantages of DED over PBF (9 marks)

Q3. STL/弦高 + SDL + 金属 Binder Jetting（25 分） / STL/Chord Height + SDL + Metal Binder Jetting (25 marks)

• (a) STL 的 tessellation 原理与 弦高（chord height） 定义（4 分） / STL tessellation principle and definition of chord height (4 marks)
• (b) 弦高与 表面光滑度 的关系（含图）（5 分） / Relationship between chord height and surface smoothness, with a diagram (5 marks)
• (c) SDL（Selective Deposition Lamination） 的 3 个优势（6 分） / Three advantages of SDL (Selective Deposition Lamination) (6 marks)
• (d) Binder Jetting 打印金属零件流程（含图）（10 分） / Binder Jetting process for metal parts, with a diagram (10 marks)

Q4. PolyJet + 混凝土打印（25 分） / PolyJet + Concrete Printing (25 marks)

• (a) 多色 + 多材料 + 透明生物医学模型 → 推荐 PolyJet 并讲流程（含图）（9 分） / For a full-colour, multi-material, transparent biomedical model, recommend PolyJet and explain the process with a diagram (9 marks)
• (b) 该工艺的 2 个局限（4 分） / Two limitations of this process (4 marks)
• (c) 机械臂混凝土打印 工艺（6 分） / Robotic-arm concrete printing process (6 marks)
• (d) 混凝土打印的 3 个优势（6 分） / Three advantages of concrete printing (6 marks)

三、2022-2023 Semester 2（April/May 2023） / 2022-2023 Semester 2 Paper

Q1. LOM + 喷墨 vs 气溶胶 + SLA（25 分） / LOM + Inkjet vs Aerosol Jet + SLA (25 marks)

• (a) LOM（Laminated Object Manufacturing） 工艺流程（6 分） / LOM (Laminated Object Manufacturing) process flow (6 marks)
• (b) LOM 作为原型技术的 2 个优点 + 2 个缺点（4 分） / Two advantages and two disadvantages of LOM as a prototyping technology (4 marks)
• (c) Inkjet vs Aerosol Jet 在墨水粘度 / 液滴尺寸 / 最小特征尺寸的对比（9 分） / Compare Inkjet vs Aerosol Jet in ink viscosity, droplet size and minimum feature size (9 marks)
• (d) 影响 SLA 打印速度与分辨率的 6 个因素（6 分） / Six factors affecting SLA printing speed and resolution (6 marks)

Q2. 粉末流动性 + 测量方法 + AM 标准（25 分） / Powder Flowability + Measurement Methods + AM Standards (25 marks)

• (a) 流动性定义 与其对 PBF 过程/零件的重要性（6 分） / Definition of flowability and its importance to the PBF process/part (6 marks)
• (b) 2 种流动性测量方法（含图）：Hall 漏斗、FT4 剪切仪等（10 分） / Two flowability measurement methods with diagrams, such as Hall funnel and FT4 shear tester (10 marks)
• (c) ISO/ASTM AM 标准三级体系（General / Category / Specialized）及意义（9 分） / Three-level ISO/ASTM AM standards system (General / Category / Specialized) and its significance (9 marks)

Q3. 船用螺旋桨 → WAAM + 混合制造（25 分） / Marine Propeller → WAAM + Hybrid Manufacturing (25 marks)

• (a) 1300 mm 螺旋桨、丝材 → 推荐 DED 工艺（WAAM）并讲流程（含图）（10 分） / For a 1300 mm propeller using wire feedstock, recommend DED (WAAM) and explain the process with a diagram (10 marks)
• (b) 该 DED 技术的 3 个优势（6 分） / Three advantages of this DED technology (6 marks)
• (c) DED + CNC 混合制造 的 2 个优势 + 2 个挑战（9 分） / Two advantages and two challenges of DED + CNC hybrid manufacturing (9 marks)

Q4. FDM 多色 + ExOne BJ + 粘结剂要求（25 分） / Multi-Colour FDM + ExOne BJ + Binder Requirements (25 marks)

• (a) FDM 多色打印的 2 个挑战 与 1 个解决方案（7 分） / Two challenges and one solution for multi-colour FDM printing (7 marks)
• (b) ExOne Metal Binder Jetting 制造金属工具/模具的完整流程（10 分） / Full ExOne Metal Binder Jetting process for metal tooling/molds (10 marks)
• (c) Binder Jetting 粘结剂的 4 个要求（8 分） / Four requirements for Binder Jetting binders (8 marks)

四、两套试卷共同核心考点 / Shared Core Exam Topics

1. 七大 AM 工艺族（ISO/ASTM 52900）：Vat Photopolymerization / Material Extrusion / Material Jetting / Binder Jetting / Powder Bed Fusion / Directed Energy Deposition / Sheet Lamination。
2. PBF 深入：EBM vs SLM 对比、粉末粒径/形状/流动性、Hall/FT4 测量、熔池与致密度。
3. DED 深入：LMD（粉末）vs WAAM（丝材）、修复与大件制造、DED + CNC 混合加工。
4. Binder Jetting 完整链路：铺粉 → 喷胶 → 固化 → 脱粉 → 脱脂 → 烧结 → 熔渗/HIP。
5. 聚合物工艺：SLA 参数、FDM 多色、PolyJet 多材料多色透明。
6. 薄片层压：LOM（纸张 + 激光）、SDL（纸张 + 彩色喷墨）。
7. STL 与前处理：tessellation、chord height、切片分辨率。
8. 应用情境选型：医疗植入体（EBM/SLM）、船用大件（WAAM）、多彩生物模型（PolyJet）、建筑（混凝土打印）、大型模具（ExOne BJ）。
9. 标准与生态：ISO/ASTM 三级结构、验收与后处理规范。

English supplement: The repeated core topics are the seven ISO/ASTM AM process families, PBF powder and process behaviour, DED variants and hybrid manufacturing, the full Binder Jetting chain, polymer processes, sheet lamination, STL preprocessing, application-based process selection, and the ISO/ASTM standards ecosystem.

五、复习建议 / Revision Advice

1. 按工艺族"画思维导图"：对七大 AM 工艺族各画一张"原理 + 能量源 + 材料形态 + 层厚 + 典型材料 + 优缺点 + 典型应用 + 后处理"单页总结；试卷 60% 以上的分数落在这一框架内。
2. 绘图题必练：SLM、LMD/WAAM、Binder Jetting、PolyJet、LOM/SDL 的示意图要能徒手画出并标注"能量源 / 材料供给 / 熔池或胶层 / 基板 / 扫描方向 / 保护气"六要素。绘图题分值通常占 10 分，是高性价比拿分点。
3. 对比类题是高频：EBM vs SLM、LMD vs WAAM、DED vs PBF、BJ vs SLM、Inkjet vs Aerosol Jet、Ridge vs LASSO 等——用 表格形式 作答，每条区别不要超过 1–2 行，阅卷更易拿分。
4. 工艺选型题：按题目关键词（大件/多色/透明/植入体/修复/金属/耐高温/低成本）先锁定 最贴题的 1–2 个工艺，再用 3 条理由论证；避免堆砌全部工艺。
5. 记忆"数字锚点"：SLM 层厚 20–60 μm、EBM 粉床 650–700°C、WAAM 沉积率 kg/h 级、BJ 烧结收缩 15–20%、PolyJet 层厚 14–27 μm、混凝土层厚 10–30 mm——有具体数字的答案得分更高。
6. 粉末与材料基础：粒径分布、球形度、流动性（Hall/FT4/休止角/Carr 指数）、水分与循环粉——这块是 每年必考 的背景知识，连续两届都出现。
7. 新兴主题：STL/弦高、多色 FDM 或 PolyJet、混凝土/大型件打印、AM 标准体系——2023-2024 明显加强了"新兴工艺与应用"的覆盖，建议做专题复习。
8. 后处理与质量链：脱脂-烧结-HIP-熔渗、热处理去应力、Ra/致密度、支撑移除——许多大题的"后半段分数"都在后处理。
9. 实战演练：限时 45 分钟做一套（一题约 45 min），严格按"关键词抬头 + 解释 + 数字 + 图示"作答，再对照本文档校准。

English supplement: Revise by process family, practise diagrams, answer comparison questions using tables, lock onto the most suitable process in selection questions, memorize key numerical anchors, review powder/material fundamentals, track emerging topics, understand post-processing and quality chains, and practise timed answers using keywords, explanations, numbers, and diagrams.

附录：核心考点参考答案 / Appendix: Suggested Answers for Core Topics

下述答案为综合性参考要点，考试时可根据题目分值与具体情境进行组合扩写。

A. 七大 AM 工艺族概览 / Overview of the Seven AM Process Families

English supplement: Vat Photopolymerization uses UV curing of liquid resin for high accuracy and smooth surfaces but has brittle, low-heat-resistance materials. Material Extrusion uses heated thermoplastic filament and is cheap and easy, but anisotropic. Material Jetting jets UV-curable droplets and is excellent for multi-material, full-colour and transparent parts, but expensive. Binder Jetting selectively deposits binder into powder and is fast and low-stress, but needs debinding and sintering. Powder Bed Fusion uses laser/electron/thermal energy to fuse powder and gives dense functional parts, but is costly and stress-prone. Directed Energy Deposition feeds powder or wire into a melt pool and is good for large parts and repair, but needs machining. Sheet Lamination bonds sheets and is cheap/large/full-colour, but has weak Z-direction properties and waste-removal issues.

B. PBF 深入 / Powder Bed Fusion in Detail

B1. EBM vs SLM 对比 / EBM vs SLM Comparison

English supplement: SLM uses a laser in inert gas, finer powder, lower powder-bed temperature, better surface finish and broader material range, but higher residual stress. EBM uses an electron beam in vacuum, coarser powder and high preheating, giving lower residual stress and good Ti implant performance, but rougher surfaces and only conductive materials.

B2. 粉末流动性（flowability） / Powder Flowability

定义：粉末在重力或外力下成股/成层自由流动并均匀铺展的能力。

影响 PBF 性能的因素（三大因素）：

1. 粒径与分布：15–45 μm（SLM）/ 45–105 μm（EBM）窄高斯分布最佳；过细团聚，过粗铺层差。
2. 球形度：气雾化/等离子雾化 → 高球形度 → 滚动阻力小；破碎法 → 带棱角/卫星粒 → 流动性差。
3. 含水量：水形成液桥和氢键 → 颗粒结块 + 熔池气孔；需烘干除湿。

重要性：流动性直接决定 铺粉均匀性 → 粉床密度 → 熔池稳定性 → 孔隙率 → 致密度 → 力学性能。

测量方法：

• Hall 漏斗（ASTM B213）：测 50 g 粉末流完时间（s/50 g），简单、但细粉易堵。
• FT4 / Freeman 粉末流变仪：螺旋桨旋入粉柱测 BFE，可动态评估。
• 休止角（angle of repose）：粉堆自然坡度，越小流动性越好。
• Hausner 比 / Carr 指数：Hausner = 振实密度/松装密度，<1.25 流动性好。

English supplement: Flowability is the ability of powder to flow and spread uniformly under gravity or external force. It controls powder spreading, powder-bed density, melt-pool stability, porosity, density and mechanical properties. Important factors include particle size distribution, sphericity and moisture. Measurement methods include the Hall funnel, FT4 powder rheometer, angle of repose, Hausner ratio and Carr index.

B3. SLM 工艺流程（10 分标准答案） / SLM Process Flow (10-mark Answer)

1. CAD 切片 + 支撑生成；
2. 粉斗下落 + 刮刀铺一层（20–60 μm）；
3. Ar/N₂ 保护下，激光按扫描路径完全熔化粉末形成熔池并与下层冶金结合；
4. 工作台下降一层，重复铺粉—熔化；
5. 完成后冷却、切割支撑、去应力热处理、HIP/机加工。

关键参数：激光功率、扫描速度、hatch spacing、层厚、扫描策略（棋盘/条纹/旋转角）。

English supplement: SLM starts from CAD slicing and support generation. A thin powder layer is spread, then a laser fully melts selected regions under inert gas. The build platform lowers and the process repeats. After printing, the part is cooled, removed from the plate, stress-relieved, support-removed, and often HIPed or machined. Key parameters include laser power, scan speed, hatch spacing, layer thickness and scan strategy.

B4. EBM 用于医疗植入体的理由 / Why EBM is Suitable for Medical Implants

• 真空防污染：Ti64 不受 O/N/H 污染，疲劳/生物相容性好；
• 高温预热去应力：薄壁多孔件不变形；
• 直接打印多孔点阵：利于骨整合；
• 能量效率高、适合高熔点难加工合金（Ti、TiAl、CoCr）。

English supplement: EBM is suitable for implants because vacuum reduces oxygen/nitrogen/hydrogen contamination, high-temperature preheating reduces residual stress and distortion, porous lattices can be printed directly for osseointegration, and the process is efficient for difficult high-melting alloys such as Ti, TiAl and CoCr.

C. DED 深入 / Directed Energy Deposition in Detail

C1. DED 工艺家族 / DED Process Family

English supplement: DED includes powder-fed laser processes such as LMD/LENS, wire-fed arc processes such as WAAM, and electron-beam wire processes such as EBAM. They differ in energy source, feedstock, deposition rate, accuracy and typical applications.

C2. DED 相较 PBF 的独特优势 / Unique Advantages of DED over PBF

1. 可修复 + 改型：在已有零件上局部增材；PBF 必须从空基板开始。
2. 不受粉床限制的大尺寸：机械臂/龙门→米级甚至多米级；PBF 典型 <0.5 m。
3. 高沉积率 + FGM：实时切换送丝/送粉成分，功能梯度材料；PBF 难实现。
4. 粉末利用率高、可与 CNC 混合加工、保护气用量少。

English supplement: Compared with PBF, DED can repair or modify existing parts, build much larger components beyond powder-bed size limits, achieve high deposition rates, create functionally graded materials by changing feedstock composition, and integrate naturally with CNC machining.

C3. LMD 工艺流程 / LMD Process Flow

1. CAD 切片 → 3/5 轴机器人路径；
2. 载气（Ar）送粉与激光同轴汇聚于基材；
3. 激光形成熔池，粉末入池熔化凝固；
4. 沉积头按路径运动，逐层堆积；
5. 整体或局部惰性气氛；
6. 后处理：热处理 + CNC 精加工。

English supplement: In LMD, CAD data is sliced into a 3- or 5-axis toolpath. Argon carries powder through a coaxial nozzle into a laser-generated melt pool on the substrate. The deposition head moves along the path, builds layers under inert shielding, and the part is then heat-treated and CNC finished.

C4. WAAM（船用螺旋桨场景） / WAAM for Marine Propeller Scenario

推荐理由：1300 mm 件超 PBF/激光 DED 能力；WAAM 高沉积率 + 丝材成本低 + 机器人焊接设备成熟。

流程：

1. 切片 → 焊接路径；
2. 机械臂末端装 MIG/TIG/CMT 焊枪；
3. 引弧 + 送丝熔化 → 基板堆焊；
4. 层间温度控制（冷却、换向）；
5. 后续整体去应力 + CNC 精加工桨叶曲面。

3 优势：高沉积率（kg/h 级）、丝材便宜 + 100% 利用率、基于成熟焊接机器人投资低。

English supplement: WAAM is suitable for a 1300 mm propeller because the part exceeds typical PBF and laser DED build capacities. WAAM has high kg/h-level deposition rate, low-cost wire feedstock, near-100% material utilization and mature robotic welding equipment, but it needs stress relief and CNC finishing.

C5. DED + CNC 混合制造 / DED + CNC Hybrid Manufacturing

优势：

1. 一次装夹兼具近净成形 + 高精度表面；
2. 可原位加工 DED 完成后无法到达的内部特征；
3. 对昂贵零件支持局部修复-切削更经济。

挑战：

1. 热管理复杂：沉积高温 vs 切削冷却，残余应力控制难；
2. 系统集成难：同机床协调 DED/CNC 路径 + 碰撞检测 + 切屑/粉尘处理，设备软件投资高。

English supplement: Hybrid DED + CNC combines near-net-shape deposition with precision machining in one setup. It can machine internal or hard-to-access features during the build and repair expensive parts economically. Challenges include thermal management, residual stress, toolpath coordination, collision avoidance, chip/powder handling and high machine/software cost.

D. Binder Jetting 深入 / Binder Jetting in Detail

D1. 金属 BJ（ExOne）全流程 / Full Metal BJ (ExOne) Process

铺粉 → 喷粘结剂 → 固化(curing 180–200°C) → 脱粉 → 脱脂(debinding) → 烧结(>0.8Tm) → [熔渗/HIP]
       ↓
   绿件(green) → 棕件(brown) → 成品
                       收缩 15–20%

特点：

• 常温无应力成形、无激光；
• 速度是同规模 PBF 的数倍；
• 可一次打印多件（nesting）；
• 烧结收缩需精确补偿。

English supplement: Metal Binder Jetting spreads powder, selectively jets binder, cures the green part, depowders it, debinds it into a brown part, then sinters it above about 0.8Tm. Infiltration or HIP may be added. It is stress-free and fast because there is no laser melting, but sintering shrinkage must be compensated accurately.

D2. 粘结剂的 4 个要求 / Four Binder Requirements

1. 打印头兼容：低粘度（<20 cP）+ 合适表面张力（25–40 mN/m），稳定 drop-on-demand、不堵嘴。
2. 快速渗透 + 足够绿件强度：毫秒级渗入粉床，下层铺粉前有初强度。
3. 脱脂可完全热解无残留：避免碳化积炭污染烧结件，影响力学性能。
4. 化学稳定 + 安全环保：不腐蚀喷头/粉末、不吸潮变质、低 VOC、可长期储存。

English supplement: The binder must be compatible with the printhead, penetrate quickly while giving enough green strength, thermally decompose completely without residue during debinding, and remain chemically stable, safe and environmentally acceptable during storage and printing.

D3. BJ vs 金属 PBF 对比 / BJ vs Metal PBF Comparison

English supplement: Binder Jetting is faster and lower-stress because it jets binder layer-by-layer without local melting, but it needs debinding and sintering and has shrinkage. SLM directly produces high-density metal parts by laser melting, but is slower, more expensive and stress-prone.

E. 聚合物 / 材料喷射 / 薄片层压 / Polymer, Material Jetting and Sheet Lamination

E1. SLA 打印速度与分辨率 6 因素 / Six Factors Affecting SLA Speed and Resolution

1. 激光功率 / UV 强度 —— 固化速率上限；
2. 扫描速度 / 振镜精度 —— 速度 vs 最小线宽；
3. 层厚 —— Z 分辨率 vs 层数；
4. 光斑尺寸（spot size） —— XY 分辨率；
5. 树脂特性（Dp、Ec、粘度）；
6. 零件几何 / 摆放方向 —— 截面、支撑、悬空。

English supplement: SLA speed and resolution are affected by laser power/UV intensity, scan speed and galvanometer accuracy, layer thickness, spot size, resin properties such as penetration depth, critical exposure and viscosity, and part geometry/orientation.

E2. PolyJet（多色多材料透明场景） / PolyJet for Multi-Colour, Multi-Material Transparent Models

原理：多喷头同时喷射不同光敏树脂 + 可溶支撑，UV 即时固化，体素级混色。

流程：

1. 多喷头沿 X 扫描，同时喷射不同树脂 + 支撑；
2. UV LED 紧随固化；
3. 工作台下降一层（14–27 μm），重复；
4. 水溶/碱液去支撑。

优势：多达 7 种材料混合 + 全彩 + 透明；适合血管 + 骨骼 + 组织的解剖模型。

局限：

1. 仅限光敏树脂，力学/耐热差，UV 易老化；
2. 材料+设备昂贵，支撑材料无法回收。

English supplement: PolyJet uses multiple printheads to jet different photopolymers and soluble support material, followed immediately by UV curing. It supports voxel-level colour/material mixing, full colour and transparency, making it suitable for anatomical models. Limitations include resin-only materials, poor heat/mechanical performance, UV ageing, high machine/material cost and non-recyclable support.

E3. FDM 多色挑战 + 解决方案 / Multi-Colour FDM Challenges and Solutions

挑战：

1. 颜色残留 / 清洗塔废料：单喷头切丝时旧色残留形成过渡条纹；
2. 多喷头校准难：Z/XY 偏置标定、抬升不净会拖蹭表面、热串扰色差。

解决方案：

• 单喷头 + 多色丝材切换（Prusa MMU / Bambu AMS）+ 自动清嘴塔；
• 或 CMYK 色彩混合喷嘴实时混色。

English supplement: Multi-colour FDM faces colour contamination and purge-tower waste when a single nozzle switches filament, and calibration problems when multiple nozzles are used. Solutions include automatic material systems with purge towers or real-time CMYK colour-mixing nozzles.

E4. LOM 工艺（6 分标准答案） / LOM Process (6-mark Answer)

1. 带热熔胶纸卷送入工作台；
2. 加热压辊热压粘合当前层与下层；
3. CO₂ 激光切割当前切片轮廓 + 周围废料 crosshatch；
4. 工作台下降一层厚，送新纸层，重复；
5. 完成后手剥 crosshatch 得到类木质零件。

优点：耗材便宜、无支撑、速度快。 缺点：Z 向差易分层、不耐潮、精细特征难、剥废费人工。

English supplement: LOM feeds adhesive-backed paper, bonds each sheet using a heated roller, cuts the layer outline and waste crosshatch with a CO2 laser, lowers the platform and repeats. Advantages are cheap material, no support and fast build. Disadvantages are weak Z-direction bonding, moisture sensitivity, poor fine-feature capability and labour-intensive waste removal.

E5. SDL 的 3 个优势 / Three Advantages of SDL

1. 耗材极便宜 + 可回收（普通 A4 纸）；
2. 天然全彩打印（层前喷墨 CMYK，照片级彩色）；
3. 办公室友好（无激光、无毒气、无粉尘）。

English supplement: SDL uses ordinary recyclable paper, can naturally produce full-colour parts using CMYK inkjet printing before lamination, and is office-friendly because it avoids lasers, toxic fumes and powder dust.

E6. Inkjet vs Aerosol Jet / Inkjet vs Aerosol Jet

English supplement: Inkjet is stricter in ink viscosity and produces larger droplets/features, making it suitable for 2D colour printing and Binder Jetting. Aerosol Jet accepts a wider viscosity range, creates smaller droplets and features, and can print on non-flat 3D surfaces, making it suitable for flexible electronics and sensors.

F. STL 与前处理 / STL and Preprocessing

F1. 弦高（Chord Height） / Chord Height

定义：STL 三角面片的弦（三角形面）与其近似的真实曲面之间的 最大垂直距离。

与光滑度关系：

• 弦高 ↓ → 面片数 ↑ → 模型贴近真实曲面 → 表面光滑；
• 弦高 ↑ → 多边形刻面明显；
• 经验值：≤ 打印机 XY 分辨率或层厚的一半，过小则 STL 文件膨胀、切片耗时。

大弦高：┌─┬─┐  台阶明显
        │ │ │
小弦高：┌┬┬┬┬┐ 接近真实曲面

English supplement: Chord height is the maximum perpendicular distance between an STL triangular facet and the true curved surface it approximates. Smaller chord height means more facets, better geometric fidelity and smoother surfaces. Larger chord height gives visible faceting. A practical rule is to keep chord height no larger than about half the printer XY resolution or layer thickness; too small a value causes bloated STL files and slow slicing.

G. AM 标准体系（ISO/ASTM） / AM Standards System (ISO/ASTM)

G1. 三级金字塔结构 / Three-Level Pyramid Structure

1. General / Top-level（通用）：术语、工艺分类、通用原则（ISO/ASTM 52900 术语、52910 设计要求）。
2. Category / Process-category（工艺族）：七大工艺族或材料类通用要求（52904 金属 PBF、52911 设计指南）。
3. Specialized（专用/材料-工艺-应用）：Ti64 SLM 航空件、不锈钢 BJ 件等具体规范（粉末+参数+后处理+验收）。

English supplement: The ISO/ASTM AM standards hierarchy has three levels: General or top-level standards for terminology and common principles; Category or process-family standards for AM process families or materials; and Specialized standards for specific material-process-application combinations such as Ti64 SLM aerospace parts or stainless-steel BJ parts.

G2. 意义 / Significance

• 避免各国/各厂重复造标准；
• 通用层稳定 + 专用层灵活，新材料/新工艺可"fill-in"式纳入；
• 为航空/医疗法规行业提供可追溯质量闭环，促进 AM 零件认证。

English supplement: The standards system avoids duplicated national or company standards, keeps the general layer stable while allowing specialized standards to be added flexibly, and provides traceable quality loops for regulated industries such as aerospace and medical devices.

H. 混凝土 3D 打印 / Concrete 3D Printing

H1. 机械臂混凝土打印流程 / Robotic-Arm Concrete Printing Process

1. CAD 建筑模型 → 切片 + 机械臂姿态规划；
2. 原料：水泥 + 骨料 + 纤维 + 外加剂（高流动 + 快触变 + 快凝）；
3. 泵送混凝土至喷嘴；
4. 六轴机械臂按 3D 路径挤出条带（10–30 mm 层厚）；
5. 逐层堆叠；层间控制早期强度 + 黏结；
6. 常规湿养护。

相较龙门式优势：非平面、斜壁、悬挑、曲面墙；多机协同。

English supplement: Robotic-arm concrete printing starts with a CAD building model, slicing and robot posture planning. A printable cement mixture is pumped to the nozzle and extruded in 3D paths with 10-30 mm layers. Early strength, interlayer bonding and wet curing must be controlled. Compared with gantry systems, robotic arms can print non-planar, inclined, overhanging and curved walls and support multi-robot collaboration.

H2. 混凝土打印 3 个优势 / Three Advantages of Concrete Printing

1. 无模板施工 → 模具 + 人工成本大幅下降；
2. 几何自由度高 → 自由曲面、镂空、拓扑优化墙体；
3. 施工快 + 安全 + 低浪费 → 连续作业、工期短、废料少、高空作业少。

English supplement: Concrete printing reduces formwork and labour cost, enables freeform or topology-optimized walls, and improves speed, safety and material efficiency through continuous operation, shorter construction time, less waste and less work at height.

I. 3D 打印敏捷性 / 3D Printing Agility

1. 无模具快速迭代：CAD → 打印 → 测试，小时级完成，边际成本极低；
2. 按需分布式生产：CAD 为"数字库存"；全球节点本地化打印，抗供应链风险；
3. 几何自由 + 大规模定制：拓扑优化、随形水道、点阵结构、“一人一款"医疗器械。

English supplement: 3D printing improves manufacturing agility through tool-less rapid iteration, distributed on-demand production using CAD as digital inventory, and geometry freedom for mass customization such as topology optimization, conformal cooling, lattice structures and patient-specific medical devices.

J. 综合答题策略 / General Exam Answer Strategy

English supplement: For concept questions, give a definition, keywords and one example. For process-flow questions, include energy source, material feed, melt pool/binder layer, substrate, scanning direction and shielding gas. For diagrams, label the source, head, platform, printed layer and arrows. Use tables for comparison questions, and for selection questions choose the best process first, then justify it with geometry, material, scale, cost and accuracy.

K. 高频易错点提醒 / Frequent Mistakes

1. EBM 仅限导电材料：不要写"EBM 可打陶瓷/聚合物”。
2. SLM vs SLS：金属完全熔化叫 SLM；尼龙/塑料部分烧结叫 SLS/MJF，不要混用。
3. BJ 必须烧结才有强度，绿件强度很低；不要把 BJ 当作"一步成型"。
4. DED ≠ PBF：DED 没有粉床，材料在熔池处由喷嘴实时送入。
5. LOM 材料是纸 + 胶 + 激光；SDL 是 纸 + 胶 + 刀片 + 彩喷，不是激光。
6. PolyJet 属 Material Jetting，不是 SLA；后者在树脂槽中激光点扫，前者是多喷头按像素喷射。
7. WAAM 是 DED 的子类；精度差，必须 CNC 后加工，不是"直接可用"。
8. 弦高是垂直距离，不是弦长；越小越光滑。
9. 粘结剂喷射要求不是"颜色鲜艳"，是打印兼容 + 渗透性 + 可热解 + 安全稳定。
10. 标准 3 层级是 General → Category → Specialized，顺序别写反。

English supplement: Common mistakes include treating EBM as suitable for non-conductive materials, confusing metal SLM with polymer SLS/MJF, forgetting BJ needs sintering, mixing DED with PBF, confusing LOM and SDL, calling PolyJet SLA, assuming WAAM is directly usable without machining, confusing chord height with chord length, giving irrelevant binder requirements, and reversing the ISO/ASTM standards hierarchy.

附录 L：2023-2024 各小题参考答案（详版） / Appendix L: Detailed Suggested Answers for 2023-2024

详见本文档早期版本逻辑，以下给出 精简答题骨架；考试时用"要点 + 1 句解释 + 数字/例子"展开。 See the earlier logic in this document. The following gives a concise answer skeleton; in the exam, expand each point with one explanation plus numbers/examples.

Q1(a) 3D 打印敏捷性 3 优势（6 分） / Three agility advantages of 3D printing (6 marks)

快速迭代 / 分布式按需生产 / 几何自由与大规模定制（见 I 节展开）。

Rapid iteration / distributed on-demand production / geometry freedom and mass customization (see Section I).

Q1(b) 医用植入体选 EBM（5 分） / Why choose EBM for medical implants (5 marks)

真空防 O/N/H 污染 → 生物相容性好；高温预热去应力 → 薄壁多孔件；可直接打印多孔点阵利于骨整合；适合 Ti64/CoCr/TiAl。

Vacuum prevents O/N/H contamination and improves biocompatibility; high-temperature preheating reduces stress for thin-walled porous parts; porous lattices support osseointegration; suitable for Ti64/CoCr/TiAl.

Q1(c) EBM 2 局限（4 分） / Two limitations of EBM (4 marks)

表面粗糙（Ra 20–35 μm）；设备贵且仅限导电材料；粉末易烧结成饼。

Rough surface finish (Ra 20-35 μm); expensive equipment and conductive materials only; powder can sinter into a cake.

Q1(d) SLM 工艺（10 分，含图） / SLM process (10 marks, with diagram)

见 B3，画出：激光 + 振镜 + 刮刀 + 粉斗 + 工作台 + 保护气。

See B3. Draw: laser + galvanometer + recoater blade + powder hopper + build platform + shielding gas.

Q2(a) 粉末流动性 3 因素（6 分） / Three factors affecting powder flowability (6 marks)

粒径分布 / 球形度 / 含水量（见 B2 展开）。

Particle size distribution / sphericity / moisture content (see B2).

Q2(b) LMD 工艺（10 分，含图） / LMD process (10 marks, with diagram)

见 C3，画出：激光 + 同轴粉末喷嘴 + 熔池 + 基材 + 机械臂运动。

See C3. Draw: laser + coaxial powder nozzle + melt pool + substrate + robotic motion.

Q2(c) DED 相比 PBF 3 优势（9 分） / Three advantages of DED over PBF (9 marks)

修复改型 / 大件尺寸 / 高沉积率 + FGM（见 C2）。

Repair/modification / large part size / high deposition rate + FGM (see C2).

Q3(a) 弦高定义（4 分） / Definition of chord height (4 marks)

见 F1：三角面片与真实曲面的最大垂直距离。

See F1: the maximum perpendicular distance between the triangular facet and the true curved surface.

Q3(b) 弦高 vs 光滑度（5 分，含图） / Chord height vs smoothness (5 marks, with diagram)

弦高 ↓ → 面片数 ↑ → 光滑 ↑；图见 F1。

Chord height down -> facet number up -> smoothness up; see F1 for diagram.

Q3(c) SDL 3 优势（6 分） / Three advantages of SDL (6 marks)

便宜环保 / 天然全彩 / 办公室友好（见 E5）。

Cheap and recyclable / natural full colour / office-friendly (see E5).

Q3(d) BJ 金属流程（10 分，含图） / Metal BJ process (10 marks, with diagram)

铺粉 → 喷胶 → 固化 → 脱粉 → 脱脂 → 烧结 →（熔渗/HIP）；见 D1。

Spread powder -> jet binder -> cure -> depowder -> debind -> sinter -> (infiltration/HIP); see D1.

Q4(a) PolyJet 推荐 + 流程（9 分，含图） / PolyJet recommendation and process (9 marks, with diagram)

见 E2：多喷头多种树脂 + 支撑，UV 即时固化，体素级混色。

See E2: multiple printheads jet multiple resins plus support, UV cures immediately, voxel-level colour/material mixing.

Q4(b) PolyJet 2 局限（4 分） / Two PolyJet limitations (4 marks)

材料力学/耐热差 + UV 老化；材料与设备昂贵、支撑不可回收。

Poor mechanical/thermal performance and UV ageing; expensive materials/equipment and non-recyclable support.

Q4(c) 混凝土机械臂打印（6 分） / Robotic-arm concrete printing (6 marks)

见 H1。

See H1.

Q4(d) 混凝土打印 3 优势（6 分） / Three advantages of concrete printing (6 marks)

无模板 / 几何自由 / 快速 + 安全（见 H2）。

No formwork / geometry freedom / fast and safe construction (see H2).

附录 M：2022-2023 各小题参考答案（详版） / Appendix M: Detailed Suggested Answers for 2022-2023

Q1(a) LOM 工艺（6 分） / LOM process (6 marks)

5 步流程（见 E4）。

Five-step process (see E4).

Q1(b) LOM 2 优点 + 2 缺点（4 分） / Two advantages and two disadvantages of LOM (4 marks)

见 E4。

See E4.

Q1(c) Inkjet vs Aerosol Jet（9 分） / Inkjet vs Aerosol Jet (9 marks)

粘度 1–30 cP vs 1–1000 cP；滴 20–50 μm vs 1–5 μm；最小特征 20–50 μm vs ~10 μm。见 E6。

Viscosity 1-30 cP vs 1-1000 cP; droplet size 20-50 μm vs 1-5 μm; minimum feature 20-50 μm vs about 10 μm. See E6.

Q1(d) SLA 6 因素（6 分） / Six SLA factors (6 marks)

功率 / 扫描速度 / 层厚 / 光斑 / 树脂 / 几何方向（见 E1）。

Power / scan speed / layer thickness / spot size / resin / geometry and orientation (see E1).

Q2(a) 流动性定义与重要性（6 分） / Flowability definition and importance (6 marks)

见 B2。

See B2.

Q2(b) 2 种测量方法（10 分，含图） / Two measurement methods (10 marks, with diagram)

Hall 漏斗（s/50g）+ FT4（BFE）；画漏斗 + 旋转螺旋桨示意（见 B2）。

Hall funnel (s/50g) + FT4 (BFE); draw a funnel and rotating blade/paddle sketch (see B2).

Q2(c) ISO/ASTM 3 级结构（9 分） / ISO/ASTM three-level structure (9 marks)

General → Category → Specialized，附意义（见 G）。

General -> Category -> Specialized, with significance (see G).

Q3(a) WAAM 推荐 + 流程（10 分，含图） / WAAM recommendation and process (10 marks, with diagram)

见 C4：送丝 + 电弧 + 机械臂 + 基板。

See C4: wire feed + electric arc + robot arm + substrate.

Q3(b) WAAM 3 优势（6 分） / Three WAAM advantages (6 marks)

沉积率 / 丝材经济性 / 焊接机器人成熟（见 C4）。

Deposition rate / wire cost-effectiveness / mature robotic welding system (see C4).

Q3(c) DED + CNC 2 优势 + 2 挑战（9 分） / DED + CNC: two advantages and two challenges (9 marks)

优势：一次装夹、可修复；挑战：热管理、系统集成（见 C5）。

Advantages: one setup and repair capability; challenges: thermal management and system integration (see C5).

Q4(a) FDM 多色 2 挑战 + 1 解决（7 分） / Multi-colour FDM: two challenges and one solution (7 marks)

颜色残留 + 多喷头校准；单喷头 + AMS + 清洗塔（见 E3）。

Colour residue + multi-nozzle calibration; single nozzle + AMS + purge tower (see E3).

Q4(b) ExOne BJ 流程（10 分） / ExOne BJ process (10 marks)

见 D1 全链路。

See the full process chain in D1.

Q4(c) 粘结剂 4 要求（8 分） / Four binder requirements (8 marks)

打印头兼容 / 快速渗透 + 绿件强度 / 完全热解无残留 / 化学稳定 + 安全（见 D2）。

Printhead compatibility / fast penetration + green strength / complete thermal decomposition without residue / chemical stability + safety (see D2).