📚 IGCSE OCR Engineering: Practical Case Study Walkthrough | IGCSE OCR 工程：案例分析实战演练
Case study analysis is a vital skill for IGCSE OCR Engineering students, requiring you to apply theoretical knowledge to real-world design challenges. This article provides a step-by-step practical walkthrough using the design of an adjustable smartphone stand as a detailed example. By following the complete engineering process—from identifying the problem to evaluating the final prototype—you will see how to structure your own project reports and meet the assessment objectives for analysis, development, and evaluation.
案例分析是IGCSE OCR工程学生的一项关键技能，要求你将理论知识应用于实际设计挑战。本文通过一个可调节手机支架的设计实例，提供一步一步的实战演练。遵循完整的工程流程——从明确问题到最终原型评估——你将学会如何构建自己的项目报告，并满足分析、开发与评估的考核目标。
1. Identifying the Design Problem | 明确设计问题
Our design brief is to create a portable desktop stand that can securely hold a smartphone and allow the user to adjust the viewing angle for watching videos or making video calls. The main problem is that many existing stands are either too flimsy, lack angle adjustability, or cannot accommodate a range of phone sizes. A successful solution must address these shortcomings while being easy to manufacture and aesthetically pleasing.
我们的设计任务是创造一款便携式桌面支架，能够稳固地夹持智能手机，并允许用户调节视角以便观看视频或进行视频通话。主要问题在于许多现有支架要么过于单薄、缺乏角度可调性，要么无法适应不同尺寸的手机。一个成功的方案必须解决这些缺点，同时易于制造且外形美观。
Key user needs were gathered from a simple survey with potential users, highlighting the desire for one-handed adjustment, stable base, cable management, and a foldable design for travel. These needs form the basis of our design specification and guide all subsequent decisions.
通过与潜在用户的简单调查收集了关键需求，突出了单手调节、稳定的底座、线缆管理以及可折叠便携等期望。这些需求构成了设计规格的基础，并指导所有后续决策。
2. Research and Existing Solutions | 调研与现有方案
Researching existing products helps avoid reinventing the wheel and reveals common weaknesses. We analysed four types of phone stands: fixed-angle plastic holders, multi-joint aluminium arms, magnetic dash mounts, and wooden wedge stands. Each was assessed for stability, adjustability, compactness, and cost.
调研现有产品有助于避免重复发明并揭示常见缺陷。我们分析了四种手机支架：固定角度塑料底座、多关节铝合金臂、磁吸式仪表台支架以及木质楔形支架。分别评估了它们的稳定性、可调节性、便携性和成本。
Fixed-angle stands are cheap but cannot change viewing position; multi-joint arms are flexible but often unstable on desks; magnetic mounts require a metal plate on the phone; wooden wedges are stylish but not adjustable. These insights steered us toward a hybrid concept: a folding base combined with a ratcheting hinge mechanism to offer multiple steady positions.
固定角度支架便宜但无法改变视角；多关节臂灵活但在桌面上常常不稳；磁吸支架需要在手机上粘贴金属片；木质楔块有设计感却不可调。这些发现引导我们走向一种混合概念：折叠底座结合棘轮铰链机构，提供多个稳固的档位。
3. Developing a Design Specification | 制定设计规格
A clear specification turns user needs into measurable targets. We formulated the following key specification points: The stand must support devices 130 mm to 180 mm tall, accommodate a device thickness up to 12 mm, provide at least 5 distinct stable angles between 15° and 65° from vertical, withstand a static load of 500 g without tipping, fold to a thickness under 25 mm, and be manufactured using sustainable materials where possible.
明确的规格将用户需求转化为可测量的目标。我们制定了以下关键规格：支架必须支持130毫米至180毫米高的设备，兼容厚度不超过12毫米的设备，在垂直方向15°至65°之间提供至少5个清晰的稳定角度，能承受500克的静态载荷而不会翻倒，折叠后厚度小于25毫米，并尽可能使用可持续材料制造。
We also set aesthetic and ergonomic targets: smooth edges, a soft-touch surface, and operation with one hand. The target production cost for a batch of 50 units was kept under £3.50 per stand. This specification serves as a constant reference point for evaluating design ideas later in the process.
我们还设定了美学与人体工程学目标：光滑的边缘、柔触感的表面以及单手操作。批量生产50件的目标成本控制在每个支架3.50英镑以内。这一规格在整个过程中作为评估设计概念的恒定基准。
4. Generating Creative Concepts | 生成创意概念
Using the specification, we sketched three distinct concept ideas. Concept A featured a folding origami-style cardboard frame; Concept B used a sliding aluminium arm with a locking screw; Concept C combined a curved plywood base with a 3D-printed ratchet hinge. We applied a morphological chart to mix and match features from each.
依据规格，我们绘制了三个不同概念的草图。概念A采用折叠折纸风格的纸板框架；概念B使用带锁紧螺丝的滑动铝臂；概念C将弯曲的胶合板底座与3D打印的棘轮铰链相结合。我们利用形态矩阵对各个特征进行混合匹配。
Concept C scored highest in a decision matrix because it offered the best balance of stability, adjustability, and material sustainability. The ratchet mechanism allows easy one-handed angle change, while the curved wood base provides a large footprint without excessive weight. We selected the C concept for further development.
概念C在决策矩阵中得分最高，因为它提供了稳定性、可调节性和材料可持续性的最佳平衡。棘轮机构允许轻松的单手角度变换，而弯曲的木质底座在不增加过多重量的情况下提供了大支撑面。我们选择概念C进行深入发展。
5. Developing the Chosen Design | 发展选定方案
With Concept C selected, we refined every detail. The ratchet hub was designed with three pawls and a 36-tooth gear wheel, giving 10° increments and a theoretical maximum angle of 70°. We modelled the pivot friction and chose a stainless steel spring to apply consistent pressure on the pawls. Dimensions were optimised in CAD to ensure the centre of mass stayed well within the base footprint at all angles.
选定概念C后，我们细化了所有细节。棘轮轴心设计为三个棘爪和一个36齿齿轮，每档10°，理论最大角度为70°。我们模拟了枢轴摩擦力，并选用不锈钢弹簧对棘爪施加恒定压力。在CAD中优化尺寸，确保在所有角度下重心都稳稳落在底座投影面内。
The phone cradle was designed with adjustable silicone grips to accommodate different widths. A hidden slot in the base allows a charging cable to pass through, addressing the cable management requirement. The entire unit can be disassembled into three flat pieces for compact storage. These refinements enhanced both function and user experience.
手机托架设计有可调节的硅胶夹爪，以适应不同宽度。底座内的隐藏插槽允许充电线穿过，满足了线缆管理需求。整个装置可拆卸为三块平板，便于紧凑收纳。这些改进增强了功能与用户体验。
6. Material Selection and Justification | 材料选择与论证
Choosing the right materials ensures the design meets mechanical and environmental requirements. For the base and supporting arm, we considered birch plywood, acrylic, and ABS plastic. A comparison table helped justify the final choice.
选择合适的材料可以确保设计满足力学与环境要求。对于底座和支撑臂，我们考虑了桦木胶合板、亚克力和ABS塑料。通过对比表格帮助论证最终选择。
| Property | Birch Plywood | Acrylic | ABS |
|---|---|---|---|
| Density (g/cm³) | 0.68 | 1.18 | 1.04 |
| Tensile Strength (MPa) | 45 | 65 | 40 |
| Sustainability | Renewable, biodegradable | Non-renewable, recyclable | Oil-based, recyclable |
| Aesthetics | Warm, natural grain | Glossy, transparent | Matte, many colours |
Birch plywood was selected for the base due to its low embodied energy, warm appearance, and adequate strength. It can be laser-cut accurately and finished with natural oil. The ratchet hub and pawls require better wear resistance, so PLA filament was chosen for 3D printing, offering enough strength and easy prototyping. The spring is stainless steel for corrosion resistance and consistent force.
桦木胶合板因其低蕴能、温暖外观和足够强度而被选作底座材料。它可以精确激光切割，并用天然油饰面。棘轮轴心和棘爪需要更好的耐磨性，因此选择PLA线材进行3D打印，提供了足够的强度且易于原型制作。弹簧选用不锈钢，以获得耐腐蚀性和稳定的弹力。
7. Manufacturing Processes and Planning | 制造工艺与计划
The base and arm are produced using laser cutting from 6 mm birch plywood sheets, a subtractive process ideal for 2D profiles. The ratchet components are 3D-printed using fused deposition modelling (FDM), which is an additive process well-suited for complex internal geometries. The production plan involves cutting the plywood pieces, sanding edges, applying oil finish, printing the PLA parts, and assembling with the metal spring and fasteners.
底座和支撑臂采用激光切割从6毫米桦木胶合板制作，这是一种适合二维轮廓的减材工艺。棘轮部件采用熔融沉积建模（FDM）3D打印，这是一种适合复杂内部几何形状的增材工艺。生产计划包括切割胶合板件、边缘打磨、涂油饰面、打印PLA零件，以及使用金属弹簧和紧固件进行组装。
We created a process flow chart and estimated each step’s time. Laser cutting takes roughly 2 minutes per base, while printing one set of ratchet parts needs about 45 minutes. The assembly is manual and designed to require no adhesive, using snap-fits and screws. A jig was designed to ensure consistent screwing positions during batch production.
我们绘制了工艺流程图并估算每一步的时间。激光切割每个底座大约需要2分钟，而打印一套棘轮零件约需45分钟。装配采用手工方式，设计为无需粘合剂，利用卡扣和螺钉连接。还设计了一个夹具，确保批量生产中螺钉定位的一致性。
8. CAD Modelling and Technical Drawings | CAD建模与技术制图
All components were modelled in parametric CAD software, allowing quick changes to dimensions. The assembly model was used to check for interferences between the ratchet parts and to visualise the product in its folded and extended positions. We generated an exploded isometric view to show the relationship between the twelve components.
所有部件均使用参数化CAD软件建模，便于快速调整尺寸。装配模型用于检查棘轮部件之间的干涉，并可视化产品在折叠和展开位置的状态。我们生成了分解等轴测视图，展示十二个部件之间的装配关系。
From the 3D model, we derived 2D orthographic drawings with dimensions to BS 8888 standards. These drawings include front, side, and plan views, along with a detailed view of the ratchet mechanism. Tolerance notes were added for the snap-fit features: the gap between pawl and gear tooth was controlled to 0.2 mm ± 0.05 mm to ensure smooth operation.
从三维模型中，我们导出了符合BS 8888标准的二维正交图并标注尺寸。这些图纸包括前视图、侧视图和平面图，以及棘轮机构的详细视图。为卡扣配合特征添加了公差注释：棘爪与齿轮齿之间的间隙控制在0.2毫米±0.05毫米，以确保运行顺畅。
9. Prototyping and Testing | 原型制作与测试
A physical prototype was built using the same processes planned for production. The test plan aimed to verify every specification point. First, we placed phones of various sizes in the cradle and adjusted through all five angle positions. The stand held all devices securely without slipping. To test the 500 g load, we attached a calibrated weight to a phone and confirmed the stand did not tip, even at the steepest 65° angle.
使用与生产计划相同的工艺制作了实体原型。测试计划旨在验证每一个规格点。首先，我们把不同尺寸的手机放入托架，并调节到全部五个角度位置。支架稳固地夹持住所有设备，没有滑动。为了测试500克负载，我们将校准重量附加到手机上，确认即使在最陡的65°角下支架也不会翻倒。
We measured the folding thickness at 22 mm, well under the 25 mm target. One-handed operation was recorded on video, and five test users rated the experience. The ratchet action produced an audible click and felt secure. However, initial prototypes showed slight warping of the 3D-printed gear after 50 cycles, leading to a material adjustment in the next iteration.
我们测量折叠厚度为22毫米，远低于25毫米目标。单手操作被录像记录，并由五名测试用户对体验进行评分。棘轮动作发出清晰的咔嗒声，感觉牢固。然而，初始原型在50次循环后出现3D打印齿轮的轻微变形，这导致在下个迭代中调整了材料。
10. Evaluation and Iterative Improvement | 评估与迭代改进
We evaluated the prototype against the original specification using a simple pass/fail table with comments. All mechanical requirements passed, but the one-handed adjustment was not perfect for left-handed users because the release button was positioned on the right. We therefore added a symmetrical button layout. The warping issue was solved by annealing the PLA parts at 60°C for 30 minutes, which increased crystallinity and dimensional stability.
我们对照原始规格，使用简单的通过/未通过表格并附评论对原型进行了评估。所有力学要求都通过了，但单手调节对左撇子用户并不完美，因为释放按钮位于右侧。因此我们增加了对称按钮布局。翘曲问题通过对PLA部件在60°C下进行30分钟退火处理得以解决，这提高了结晶度和尺寸稳定性。
Cost analysis showed that the material cost per unit was £2.10, well within the £3.50 budget, leaving room for packaging. User feedback also suggested adding a non-slip silicone pad on the base bottom, which we incorporated. This iterative cycle of test, evaluate, and refine is the heart of engineering design and demonstrates how a product evolves from a concept to a viable solution.
成本分析显示，每件的材料成本为2.10英镑，远在3.50英镑预算之内，为包装留出了空间。用户反馈还建议在底座底部增加防滑硅胶垫，我们采纳了这一建议。这种测试、评估和改进的迭代循环是工程设计的核心，展示了产品如何从概念发展为可行的解决方案。
11. Sustainability and Environmental Considerations | 可持续性与环境考量
Engineering cases must consider the full product life cycle. Our design uses sustainably sourced birch plywood certified by the FSC, and the PLA is derived from corn starch, making it industrially compostable under the right conditions. At the end of life, the wooden parts can be composted or incinerated for energy recovery, while metal springs and fasteners can be recycled.
工程案例必须考虑完整的产品生命周期。我们的设计使用经FSC认证的可持续来源桦木胶合板，PLA源自玉米淀粉，在合适条件下可在工业设施中堆肥。在产品寿命结束时，木质部件可以堆肥或焚烧回收能量，而金属弹簧和紧固件可以回收利用。
We simplified disassembly by using only two types of screws and no adhesives, which eases separation for recycling. The packaging was designed to be a single folded cardboard sleeve, eliminating plastic blister packs. A simple carbon footprint estimation showed that local sourcing of plywood and using a renewable-based plastic reduced the overall CO₂ equivalent compared to an all-ABS design by approximately 40%.
我们通过仅使用两种规格的螺丝且无粘合剂来简化拆卸，便于分类回收。包装设计为单张折叠纸板套，消除了塑料泡罩。简单的碳足迹估算表明，与全ABS设计相比，本地采购胶合板并使用可再生基塑料可将整体二氧化碳当量降低约40%。
Published by TutorHao | Engineering Revision Series | aleveler.com
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