📚 AS Edexcel Engineering: Case Study Practical Exercise | AS Edexcel 工程：案例分析实战演练
Case study analysis is a core component of the AS Edexcel Engineering examination. It requires you to apply theoretical knowledge to a real-world product, evaluating materials, processes, mechanics, electronics, ergonomics, and sustainability. This article presents a practical exercise using an adjustable desk lamp as the case, guiding you through a structured analytical approach to develop key skills for top marks.
案例分析是 AS Edexcel 工程考试的核心组成部分，要求你将理论知识应用于实际产品，评估其材料、工艺、力学、电子、人体工程学及可持续性。本文以可调节台灯为案例进行实战演练，通过系统化的分析方法，帮助你培养高分所需的核心技能。
1. Interpreting the Design Brief | 解读设计概要
Before any analysis, read the design brief carefully. For our adjustable desk lamp, the brief states: 'a task light for home office use, with an adjustable arm and head, LED illumination, powered by mains electricity, durable yet lightweight, cost-effective, and visually appealing.' You must extract key constraints and objectives.
在分析之前，仔细阅读设计概要。对于我们可调节台灯，概要指出：'用于家庭办公的任务照明，具有可调节臂部和灯头，采用 LED 光源，市电供电，耐用而轻便，成本效益好且外观吸引人。'你必须提取关键约束和目标。
Highlight functional requirements (adjustability, brightness), performance targets (light weight, durability), and non-technical aspects (aesthetics, cost). This forms the basis for all evaluations.
突出功能要求（可调性、亮度）、性能目标（轻质、耐用）和非技术方面（美观、成本）。这构成了所有评价的基础。
2. Functional and Performance Specifications | 功能与性能指标
nslate the brief into measurable specifications. For the lamp: adjustable height range 300– neutral white), power consumption ≤10 W, total mass ≤2 kg, expected lifespan 20,000 hours.
将设计概要转化为可量化的规格。对于台灯：可调高度范围 300–600 mm，灯头俯仰角 ±90°，光通量 ≥400 lm，色温 4000 K（中性白），功耗 ≤10 W，总质量 ≤2 kg，预期寿命 20000 小时。
List performance criteria like impact resistance, thermal management for LEDs, and electrical safety compliance (e.g., BS EN 60598). These will guide material and component selection.
列出性能标准，如抗冲击性、LED 的热管理以及电气安全合规性（例如 BS EN 60598）。这些将指导材料和元器件的选择。
3. Material Selection and Justification | 材料选择与理由
Identify components: base, arm linkages, head housing, diffuser lens, fasteners. Base requires high density for stability but not excessive weight. A zinc-aluminium alloy (Zamak) or mild steel with a polymer cover could be suitable. Provide justification using property profiles.
识别各部件：底座、臂部连杆、灯头外壳、扩散透镜、紧固件。底座需要高密度以保持稳定，但不过重。锌铝合金（Zamak）或低碳钢加聚合物外壳可能是合适的。利用性能图提供理由。
yield strength ≈170 MPa, density 2.7 g/cm³. A table comparing candidate materials could be used.
对于臂部，挤压铝合金 6063 提供了高比强度、耐腐蚀性和良好的可挤压性。提供数据：屈服强度约 170 MPa，密度 2.7 g/cm³。可使用比较候选材料的表格。
| Material | Yield Strength (MPa) | Density (g/cm³) | Relative Cost | Processability |
|---|---|---|---|---|
| Al 6063-T6 | 170 | 2.7 | Medium | Excellent (extrusion) |
| Mild steel | 250 | 7.8 | Low | Good (stamping) |
| ABS (glass-filled) | 50 | 1.2 | Low | Good (injection mould) |
The final selection for the arm is Al 6063-T6, with its excellent balance of strength, weight and cost.
臂部的最终选择是 Al 6063-T6，其强度、重量和成本达到了出色的平衡。
4. Manufacturing Process Evaluation | 制造工艺评估
For each component, evaluate suitable manufacturing processes. The aluminium arm can be produced by hot extrusion, then cut to length and drilled for pivot holes. Extrusion offers high production rate, good surface finish, and low material waste.
对于每个组件，评估合适的制造工艺。铝合金臂部可通过热挤压成型，然后切割至所需长度并钻孔用于枢轴。挤压成型具有高生产率、良好的表面光洁度和低材料浪费。
The base, if steel, could be stamped and bent from sheet metal, or die-cast if using Zamak. The LED diffuser lens might be injection-moulded polycarbonate for optical clarity and impact resistance.
底座如为钢材，可通过钣金冲压折弯成型，或若使用 Zamak 则采用压铸。LED 扩散透镜可选用注射成型聚碳酸酯，以获得光学透明度和抗冲击性。
Discuss process capabilities: extrusion tolerance, die-casting cycle time, injection moulding tooling cost. Justify choices against production volume (assume medium volume, 10,000 units/year).
讨论工艺能力：挤压公差、压铸循环时间、注射成型模具成本。根据产量（假设年产 10,000 件中等批量）论证选择。
5. Structural and Mechanical Analysis | 结构与力学分析
head, with centre of mass at 0.4 m from the pivot, the moment M = F × d = (0.8 kg × 9.81 m/s²) × 0.4 m ≈ 3.14 N·m.
分析台灯完全伸展时的受力情况。臂部和灯头对底座枢轴施加一个力矩。假设臂部和灯头质量为 0.8 kg，质心距离枢轴 0.4 m，则力矩 M = F × d = (0.8 kg × 9.81 m/s²) × 0.4 m ≈ 3.14 N·m。
M = F × d = (0.8 kg × 9.81 m/s²) × 0.4 m ≈ 3.14 N·m
Calculate the required friction or locking force at the adjustment joints to hold the position. The pivot screw must generate enough clamping force to resist this moment.
计算调节关节处所需的摩擦力或锁紧力以保持位置。枢轴螺钉必须产生足够的夹紧力来抵抗该力矩。
imple bending stress check: σ = M y / I. The arm tube can be approximated as a cantilever.
简单弯曲应力校核：σ = M y / I。臂管可近似为悬臂梁。
6. Electronic System Design | 电子系统设计
efficiency. Block diagram: AC input → rectification → DC-DC buck converter → constant current output → LED array.
LED 驱动器必须将 230 V 交流市电转换为恒流供给 LED。选用带 PWM 调光控制的开关电源（SMPS）以提高效率。框图：交流输入 → 整流 → DC-DC 降压转换器 → 恒流输出 → LED 阵列。
Specify components: bridge rectifier, filter capacitor, controller IC (e.g., MP24894), MOSFET, inductor, current sense resistor. Ensure thermal management with a heatsink on the LED MCPCB.
指定元器件：桥式整流器、滤波电容、控制 IC（如 MP24894）、MOSFET、电感和电流检测电阻。确保在 LED 金属芯 PCB 上安装散热器进行热管理。
Protection circuits: overcurrent, overtemperature, and EMC filtering to meet regulatory standards.
保护电路：过流、过温和 EMC 滤波，以满足法规标准。
7. Ergonomics and Safety Considerations | 人机工程与安全考量
Adjustment mechanisms must be operable with one hand and require low force. Knobs should be large enough for comfortable grip, with textured surfaces. The lamp should remain stable at extreme positions without tipping.
调节机构应可单手操作且所需力度小。旋钮应足够大以便舒适抓握，并带有纹理表面。台灯在极限位置应保持稳定而不倾倒。
Safety: Insulation between live parts, double insulation or earthing, strain relief on the power cord, and a tilt switch to cut power if the lamp falls. Surface temperatures must stay below 60 °C to prevent burns.
安全性：带电部件之间的绝缘、双重绝缘或接地、电源线的应力消除，以及倾倒断电开关（如果台灯倾倒）。表面温度须保持在 60 °C 以下以防烫伤。
8. Sustainability and Lifecycle Impact | 可持续性与生命周期影响
Conduct a lifecycle assessment (LCA) covering raw material extraction, manufacturing, use, and end-of-life. Aluminium arm is recyclable with low energy for recycling. The LED array offers long life, reducing replacement waste. The base, if steel, is also recyclable.
进行生命周期评估（LCA），涵盖原材料提取、制造、使用和报废。铝合金臂可回收，回收能耗低。LED 阵列寿命长，减少了更换废弃物。底座如为钢制，也可回收。
Design for disassembly: Use mechanical fasteners instead of adhesives to allow separation of materials. Minimise mixed-material joints. Specify recycled content where possible.
面向拆卸的设计：使用机械紧固件而非粘合剂，以便材料分离。尽量减少混合材料接头。在可能的情况下指定回收含量。
9. Costing and Value Engineering | 成本与价值工程
Estimate component costs: aluminium tube extrusion ≈ £2.50/m, LED array + driver PCB ≈ £4.00, plastic moulded parts ≈ £1.20 each, steel base stamping ≈ £1.80. Assembly labour and overhead add £3.00 per unit. Total bill of materials about £12–15.
估算组件成本：铝合金管挤压材约 2.50 英镑/米，LED 阵列及驱动 PCB 约 4.00 英镑，塑料注塑件每个约 1.20 英镑，钢底座冲压件约 1.80 英镑。装配人工和管理费用每件增加 3.00 英镑。物料总成本约 12–15 英镑。
Value engineering: Could the arm be made of glass-filled nylon to reduce cost? Trade-off strength and thermal performance. Analyse cost-benefit. A simplified design with fewer adjustable joints may lower production cost.
价值工程：臂部可否改用玻纤尼龙以降低成本？需权衡强度和热性能。分析成本效益。减少可调节关节的简化设计可降低生产成本。
Published by TutorHao | Engineering Revision Series | aleveler.com
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