📚 AS CCEA Engineering: Case Study in Action | AS CCEA 工程：案例分析实战演练
Case studies bring AS Engineering theory to life. They require you to investigate a real-world product or system, apply scientific principles, and justify design decisions. This article walks you through a practical case study and shows how to structure your analysis for CCEA assessments.
案例分析能让 AS 工程理论变得生动具体。你需要研究真实的产品或系统，运用科学原理，并论证设计决策。本文将通过一个实战案例，为你展示如何组织符合 CCEA 要求的分析。
1. Purpose of Case Studies in AS Engineering | AS 工程中案例研究的目的
Engineering case studies develop your ability to solve open-ended problems. You will learn to identify constraints, select materials, evaluate manufacturing routes, and consider the social and environmental impact of a design.
工程案例研究培养你解决开放性问题的能力。你将学习识别约束条件、选择材料、评估制造路线，并考虑设计的社会和环境影响。
In the CCEA specification, case studies test your integrated understanding of mechanics, electronics, materials, and systems. They also strengthen your skills in research, calculation, and critical evaluation – essential for both the examination and further study.
在 CCEA 大纲中，案例研究考察你对机械、电子、材料和系统的综合理解。同时还能强化研究、计算和批判性评估的能力——这些对考试和后续学习都至关重要。
2. The 5-Step Approach to Engineering Case Studies | 工程案例研究的五步法
A structured methodology keeps your work clear and rigorous. The five steps we recommend are: define, research, analyse, evaluate, and present.
结构化的方法能让你的分析清晰严谨。我们推荐的五个步骤是：定义、研究、分析、评价和呈现。
- Define the problem, design brief, and key specifications. | 定义问题、设计概要和关键规格。
- Research existing solutions, materials, and relevant standards. | 研究现有方案、材料以及相关标准。
- Analyse forces, stresses, circuits, or thermal behaviour using engineering principles. | 分析力、应力、电路或热行为，运用工程原理。
- Evaluate manufacturing options, costs, risks, and sustainability. | 评价制造选项、成本、风险和可持续性。
- Present findings in a logical report with diagrams, calculations, and justified conclusions. | 呈现结果，形成逻辑清晰的报告，包含图表、计算和合理的结论。
3. Practical Case Study: Adjustable Laptop Stand | 实战案例：可调节笔记本电脑支架
Our worked example is an adjustable laptop stand aimed at students and remote workers. The product must raise a 15-inch laptop to eye level, allow angle adjustment, fold for portability, and support a load of 5 kg safely.
我们的分析案例是一款面向学生和远程工作者的可调节笔记本电脑支架。该产品需要将 15 英寸笔记本抬高至视线水平、支持角度调节、可折叠携带，并能安全支撑 5 公斤的负载。
This case study covers mechanical design, material selection, manufacturing, structural analysis, and testing – typical of AS CCEA Engineering assignments.
本案例研究涵盖了机械设计、材料选择、制造工艺、结构分析和测试——这些都是 AS CCEA 工程中常见的任务类型。
4. Problem Definition and Design Brief | 问题定义与设计概要
A clear design brief anchors the whole project. We defined the core need: a height- and tilt-adjustable portable stand that accommodates laptops up to 380 mm × 260 mm, with a total mass under 1.2 kg.
清晰的设计概要是整个项目的基石。我们定义的核心需求是：一款可调高度和倾角的便携式支架，适用于最大 380 mm × 260 mm 的笔记本电脑，总质量低于 1.2 kg。
Key constraints included a manufacturing cost below £12 per unit, at least 5 000 cycles of adjustment without loosening, and compliance with UKCA safety markings.
关键约束条件包括：单件制造成本低于 12 英镑、至少 5000 次调节不松动，以及符合 UKCA 安全标志要求。
5. Stakeholder Needs and Product Specification | 利益相关者需求与产品规格
We identified three primary stakeholders: the end user (comfort, portability), the manufacturer (ease of assembly, low tooling cost), and the environment (recyclability, minimised material use).
我们确定了三个主要利益相关方：终端用户（舒适性、便携性）、制造商（易于组装、模具成本低）和环境（可回收性、材料用量最小化）。
The product specification was translated into measurable targets, summarised in the table below.
产品规格被转化为可测量的目标，总结于下表中。
| Parameter | Target | 中文说明 |
| Max load | 50 N (5.1 kg) | 最大负载 |
| Height range | 120 – 280 mm | 高度范围 |
| Tilt angles | 0° – 35° | 倾角范围 |
| Stand mass | < 1.2 kg | 支架质量 |
| Durability | 5 000 cycles | 耐久性 |
6. Material Selection and Properties | 材料选择与性能分析
We shortlisted three materials for the main structural arms: aluminium alloy 6061-T6, ABS (acrylonitrile butadiene styrene), and 304 stainless steel. Selection was driven by specific stiffness, strength, density, and cost.
我们将主结构臂的候选材料范围缩小为三种：6061-T6 铝合金、ABS（丙烯腈-丁二烯-苯乙烯共聚物）和 304 不锈钢。选择依据是比刚度、强度、密度和成本。
Using a simplified Ashby approach, we plotted strength against density and identified 6061-T6 as the best compromise – offering high yield strength with low weight. The table below compares key properties.
我们采用简化的 Ashby 方法，以强度对密度作图，发现 6061-T6 是最佳折衷选择——兼具高屈服强度和低重量。下表对比了关键性能。
| Property | 6061-T6 Al | ABS | 304 SS |
| Density (kg/m³) | 2 700 | 1 050 | 8 000 |
| Yield strength (MPa) | 276 | 45 | 215 |
| Young’s modulus (GPa) | 69 | 2.3 | 193 |
| Relative cost per kg | 3 | 1.2 | 6 |
ABS was retained for non-load-bearing components such as the laptop tray, while 6061-T6 was chosen for the folding arms and hinge base.
ABS 被保留用于非承重部件如笔记本托盘，而 6061-T6 则用于折叠臂和铰链底座。
7. Manufacturing Process Evaluation | 制造工艺评价
We evaluated three primary processes: die casting for the aluminium arms, injection moulding for the ABS tray, and stamping for the stainless steel hinge plates.
我们评估了三种主要工艺：铝臂的压铸、ABS 托盘的注塑成型，以及不锈钢铰链板的冲压。
Die casting offered excellent surface finish and rapid cycle times, but the tooling cost was high for small batches. CNC machining was considered as an alternative for prototyping, offering lower upfront investment but higher per-unit cost.
压铸可提供优异表面光洁度和快速循环时间，但对于小批量生产模具成本较高。CNC 加工作为原型制造备选方案，前期投资较低，但单件成本更高。
Injection moulding was the clear choice for the ABS tray because of its ability to produce complex ribs and snap-fit features in one shot. Stamping produced consistent hinge components with minimal material waste.
注塑成型显然是 ABS 托盘的理想选择，因为它能一次成型出复杂的肋板和卡扣特征。冲压则以极少材料浪费生产了一致性良好的铰链部件。
8. Structural and Mechanical Analysis | 结构与力学分析
The most critical mechanical part is the vertical support arm, which acts as a cantilever beam when fully extended. We modelled the arm as an aluminium tube fixed at the base with the laptop load applied at the free end.
最关键机械部件是垂直支撑臂，它在完全伸展时可视为悬臂梁。我们将该臂建模为一根铝合金管，底部固定，自由端承受笔记本负载。
Given a load F = 50 N at a distance L = 0.22 m from the fixed end, the maximum bending moment M is calculated as:
在距固定端 L = 0.22 m 处施加 F = 50 N 的载荷，最大弯矩 M 计算如下：
M = F × L = 50 N × 0.22 m = 11 N·m = 11 000 N·mm
The cross-section is a circular tube with outer diameter D = 25 mm and wall thickness t = 2 mm, giving inner diameter d = 21 mm. The second moment of area I is:
横截面为圆管，外径 D = 25 mm，壁厚 t = 2 mm，内径 d = 21 mm。截面惯性矩 I 为：
I = π(D⁴ – d⁴) / 64 = π(25⁴ – 21⁴) / 64 = π(390 625 – 194 481) / 64 ≈ 9 632 mm⁴
Maximum bending stress occurs at the outermost fibre, y = D/2 = 12.5 mm. Using the flexure formula:
最大弯曲应力出现在最外层纤维处，y = D/2 = 12.5 mm。运用弯曲公式：
σ = M y / I = 11 000 × 12.5 / 9 632 ≈ 14.3 MPa
The yield strength of 6061-T6 is 276 MPa, giving a safety factor of approximately 19. This confirms the arm is more than strong enough; stiffness and stability become the design drivers.
6061-T6 的屈服强度为 276 MPa，安全系数约为 19。这证实该臂强度绰绰有余；刚度和稳定性成为设计驱动因素。
9. Risk Assessment and Safety Considerations | 风险评估与安全考量
We carried out a simplified FMEA (Failure Mode and Effects Analysis) for the stand. Potential hazards identified included pinch points at hinge joints, sharp edges after stamping, and tip-over if the base footprint is too small.
我们对支架进行了简化 FMEA（失效模式与影响分析）。识别出的潜在危险包括：铰链关节处的夹手点、冲压后的锋利边缘，以及基座占地面积过小导致的倾翻。
Mitigations included adding plastic hinge covers, specifying deburring for all metal edges, and increasing the base depth to 180 mm to lower the centre of gravity. All contact materials were specified as non-toxic and RoHS compliant.
缓解措施包括添加塑料铰链罩、规定所有金属边缘必须去毛刺，以及将基座深度增加至 180 mm 以降低重心。所有接触材料均指定为无毒、符合 RoHS 标准。
A risk rating matrix assigned each hazard a severity and likelihood score, ensuring that no residual risk fell into the ‘high’ category.
风险评级矩阵为每种危险分配了严重程度和发生概率评分，确保无残余风险落入“高风险”类别。
10. Integrated Design and Prototyping | 集成设计与原型制造
Our design integrates a friction hinge mechanism that allows stepless tilt adjustment. A spring-loaded locking pin enables quick height changes without separate tools.
我们的设计集成了摩擦铰链机构，可实现无级倾角调节。弹簧加载的锁定销无需额外工具即可快速调节高度。
We produced a functional prototype using CNC-machined aluminium arms, 3D-printed ABS joints, and off-the-shelf stainless steel fasteners. This allowed us to verify fit, range of motion, and ease of assembly before committing to mass-production tooling.
我们利用 CNC 加工的铝臂、3D 打印的 ABS 关节以及市售不锈钢紧固件制作了功能原型。这使我们在投入量产模具之前，能够验证配合、运动范围和装配简易性。
Design for manufacture (DFM) principles were applied to reduce part count from 24 to 14, cutting assembly time by an estimated 35%.
我们应用面向制造的设计（DFM）原则，将零件数量从 24 个减少到 14 个，预计装配时间缩短约 35%。
11. Testing and Evaluation Strategy | 测试与评价策略
A structured test plan was designed to validate the product against the original specification. Mechanical load tests applied 55 N (10% overload) for 24 hours with no permanent deformation recorded.
我们制定了结构化测试计划，以对照原始规格验证产品。机械负载测试施加 55 N（10% 过载）持续 24 小时，未记录到永久变形。
Adjustment cycling reached 6 200 repetitions without significant loosening, exceeding the 5 000-cycle target. A tilt-table test confirmed the stand remained stable on a 15° incline.
调节循环测试达到 6200 次而无明显松动，超过了 5000 次的目标。倾斜台测试确认支架在 15° 斜面上仍保持稳定。
User trials with 10 participants rated ergonomics and portability above 4.2/5. Minor issues with hinge stiffness at extreme angles were noted and resolved by modifying the friction pad material.
对 10 名参与者的用户试用将人机工程学和便携性评分达到了 4.2/5 以上。记录了极端角度下铰链僵硬的小问题，通过更换摩擦垫材料得以解决。
12. Conclusion and Reflection | 结论与反思
This case study demonstrates a complete engineering design loop – from problem definition through analysis and prototyping to validation. The adjustable laptop stand met all key specifications, with a measured factor of safety above 18 and excellent user feedback.
本案例展示了完整的工程设计循环——从问题定义、分析、原型制造到验证。可调节笔记本电脑支架满足所有关键规格，实测安全系数超过 18，用户反馈优良。
Reflecting on the process, we observed that early material selection and DFM input significantly reduced late-stage changes. Writing a clear design brief and specification proved essential for maintaining focus during detailed analysis.
回顾整个过程，我们发现早期的材料选择和 DFM 参与显著减少了后期变更。撰写清晰的设计概要和规格对于在详细分析阶段保持专注至关重要。
Published by TutorHao | Engineering Revision Series | aleveler.com
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