Case Study Practice: Redesigning a Phone Stand | 案例分析实战演练：重新设计手机支架

📚 Case Study Practice: Redesigning a Phone Stand | 案例分析实战演练：重新设计手机支架

Engineering case studies require you to analyse an existing product, identify weaknesses and propose a redesigned solution based on technical knowledge. This practice unit walks you through the complete process, from understanding the problem to evaluating a new design for a phone stand.

工程案例分析要求你分析现有产品、识别缺陷并基于技术知识提出重新设计的解决方案。本练习单元将带你走完完整流程，从理解问题到评估一款手机支架的新设计。

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1. Introduction to the Case Study | 案例介绍

The product under review is the ‘GripMax’ universal phone stand, a plastic desktop accessory designed to hold smartphones between 4 and 7 inches. It features a spring-loaded clamp and a simple tilt hinge. However, customer feedback reveals frequent complaints: the stand tips over easily, the clamp loses tension after a few months, and the viewing angle cannot be locked securely.

待审产品是 “GripMax” 通用手机支架，这是一款塑料桌面配件，用于固定4至7英寸智能手机。它采用弹簧夹和一个简易的倾斜铰链。然而，客户反馈显示频发投诉：支架容易翻倒、夹子在使用几个月后失去张力、视角无法牢固锁定。

To address these issues, you will adopt the role of a design engineer tasked with creating an improved version that is more stable, durable and user-friendly while keeping manufacturing costs reasonable.

为了解决这些问题，你将扮演设计工程师的角色，负责打造一个更稳定、更耐用且用户友好的改进版本，同时将制造成本控制在合理范围内。

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2. Understanding the Problem | 理解问题

Before jumping to solutions, it is crucial to analyse the root causes of the product’s failures. The instability arises from a narrow base footprint and a high centre of mass when a heavy phone is attached, creating an overturning moment.

在提出解决方案之前，分析产品失效的根本原因至关重要。不稳定性源于狭窄的底座占地面积和安装重手机时较高的质量中心，这会产生倾覆力矩。

The clamping force degradation is primarily due to the use of a low-carbon steel spring that undergoes plastic deformation after repeated cycles, as well as stress relaxation in the plastic clamp arms.

夹持力衰减主要是由于使用了低碳钢弹簧，该弹簧在反复循环后发生塑性变形，以及塑料夹臂中的应力松弛所致。

The locking mechanism for angle adjustment relies solely on friction between two smooth plastic surfaces, which wears out quickly and cannot hold the desired tilt under dynamic loads (like tapping the screen).

角度调节的锁紧机构仅依靠两个光滑塑料表面之间的摩擦，这种摩擦会迅速磨损，无法在动态载荷（如点击屏幕）下保持所需的倾斜角度。

By defining these technical problems in engineering terms, we can focus our redesign on targeted improvements.

通过用工程术语定义这些技术问题，我们可以将重新设计聚焦在有针对性的改进上。

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3. Existing Product Analysis | 现有产品分析

A thorough product analysis involves disassembling the GripMax and documenting its components, materials, manufacturing methods and assembly sequence. The stand comprises a base, two clamp jaws, a compression spring, a pivot pin and a tilt head.

彻底的产品分析包括拆卸 GripMax 并记录其零部件、材料、制造方法和装配顺序。该支架由一个底座、两个夹爪、一个压缩弹簧、一个枢轴销和一个倾斜头组成。

The base and clamp jaws are injection-moulded from polypropylene (PP), chosen for its low cost and good impact resistance. However, PP has relatively low stiffness and creep resistance, which contributes to jaw deformation under sustained load. The spring is a helical compression spring made from music wire (carbon steel) without corrosion protection; in moist environments it can rust, further reducing performance.

底座和夹爪采用聚丙烯(PP)注塑成型，选择 PP 是因为其低成本且抗冲击性良好。然而，PP 的刚度和抗蠕变性相对较低，这在持续载荷下导致夹爪变形。弹簧是一个由琴钢丝（碳钢）制成的螺旋压缩弹簧，没有防腐蚀保护；在潮湿环境中可能生锈，进一步降低性能。

The tilt head uses a simple cylindrical pivot that is press-fitted into the base. The interference fit provides some friction, but it is insufficient to prevent movement. No ratchet, detent or positive locking feature is present. The base footprint is a circle of diameter 60 mm, which offers limited stability when the phone is positioned at an angle.

倾斜头采用一个简单的圆柱形枢轴，压入底座。过盈配合提供了一些摩擦力，但不足以阻止移动。没有棘轮、定位槽或任何正向锁定功能。底座占地是一个直径为60毫米的圆形，当手机以一定角度放置时，提供的稳定性有限。

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4. Identifying Weaknesses | 识别缺陷

Based on the analysis, three critical weaknesses are identified: insufficient base stability (static and dynamic), rapid loss of clamping force, and an unreliable angle-adjustment mechanism. Each weakness can be translated into an engineering requirement for the new design.

基于分析，确定了三个关键缺陷：底座稳定性（静态和动态）不足、夹持力快速丧失以及角度调节机构不可靠。每个缺陷都可以转化为新设计的工程要求。

Weakness 1 – Stability: The moment required to tip the stand is low because the base radius is small and the phone’s weight acts far from the pivot. To improve stability, the new design must increase the base footprint or lower the centre of gravity. A wider, non-circular base or the addition of a counterweight could be considered. The target is to withstand a lateral force of at least 3 N at the top of the phone without tipping.

缺陷1 – 稳定性：使支架倾倒所需的力矩很小，因为底座半径小，且手机的重量作用点远离支点。为提高稳定性，新设计必须增大底座占地面积或降低重心。可考虑更宽的非圆形底座或增加配重。目标是在手机顶部承受至少3牛的侧向力而不倾倒。

Weakness 2 – Clamping durability: The spring and plastic combination must maintain a minimum clamping force of 5 N after 10,000 cycles, representing daily use over three years. This requires a spring with higher fatigue strength and a clamp body material with lower creep.

缺陷2 – 夹持耐久性：弹簧与塑料的组合必须在10000次循环后保持至少5牛的夹持力，这代表三年每日使用。这要求使用疲劳强度更高的弹簧以及蠕变更低的夹体材料。

Weakness 3 – Angle locking: The tilt mechanism needs a positive locking feature, such as a toothed disc or a ratchet, that resists dynamic loads without relying solely on friction. The user must be able to adjust the angle in distinct steps, with a minimum locking torque of 0.8 Nm.

缺陷3 – 角度锁定：倾斜机构需要一个正向锁定功能，例如齿盘或棘轮，能够抵抗动态载荷而不依赖纯摩擦。用户必须能够按清晰档位调节角度，最小锁紧力矩为0.8牛·米。

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5. Design Brief and Specification | 设计概要及规格

The design brief is to develop a new phone stand, ‘StableGrip Pro’, that overcomes the three identified weaknesses while remaining competitive in cost. The product specification translates the voice of the customer and engineering analysis into measurable targets.

设计概要是开发一款名为 “StableGrip Pro” 的新手机支架，克服三个已识别的缺陷，同时在成本上保持竞争力。产品规格将客户之声和工程分析转化为可量化的目标。

Key specifications: base dimensions 120 mm x 80 mm elliptical shape to increase tipping resistance; clamping force >= 8 N when new, retained >= 6 N after fatigue test; angle adjustment from 0° to 75° in 15° increments using a detent mechanism; materials must be recyclable and suitable for high-volume injection moulding; target manufacturing cost below £2.50 per unit at 50,000 units

Published by TutorHao | Year 11 工程 Revision Series | aleveler.com

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