Electronic and Mechanical Systems

This section focuses on electronic and mechanical systems, which combine components to perform specific tasks in a wide range of products, from everyday household devices to complex industrial machinery. Understanding how forces, stresses, material properties, and manufacturing processes influence the design and production of these systems is crucial for studying Design and Technology.

Forces and Stresses

Both electronic and mechanical systems are affected by different types of forces and stresses depending on the materials used and the tasks the system performs. Some key points include:

• Mechanical Stress: In mechanical systems, materials are exposed to various stresses, such as tensile stress (stretching), compressive stress (squeezing), and shear stress (sliding forces). These stresses affect the materials used in gears, levers, springs, and other mechanical components.
• For example, steel is used in high-stress components like gears and shafts because it has excellent tensile strength, while brass is chosen for gears or bearings due to its ability to withstand friction and wear.
   
• Electronic Stress: In electronic systems, electrical stress (due to excessive current or voltage) and thermal stress (due to heating from the operation of the circuit) can affect components such as resistors, capacitors, and wires. Electronic components must be designed to handle these stresses without failing.
• For instance, resistors are chosen based on their ability to dissipate heat, while capacitors are selected for their voltage tolerance.

Fatigue: Both electronic and mechanical systems can experience fatigue after repeated cycles of stress. For example, springs in mechanical systems may become less effective over time, while electronic circuits may suffer from the deterioration of materials after prolonged use.

Ecological and Social Footprint

The ecological and social footprint of electronic and mechanical systems is a growing concern in design:

• Ecological footprint: The materials used in both electronic and mechanical systems can have significant environmental impacts. For example, metals like copper and gold, used in electronic circuits, require mining, which contributes to habitat destruction, pollution, and CO2 emissions. On the other hand, mechanical components made from metals like steel and aluminium can be recycled, reducing the overall environmental impact.
• The production of batteries for electronic systems (like lithium-ion batteries) has a particularly high ecological footprint due to the extraction of rare minerals and the energy-intensive manufacturing processes.
• Sustainable alternatives, such as using recycled materials or biodegradable components, can help reduce the ecological footprint of products.
• Social footprint: The social impact of producing electronic and mechanical systems can involve both positive and negative outcomes. On the positive side, products like solar panels and electric vehicles contribute to reducing environmental harm. On the negative side, the manufacturing of electronics and machinery often takes place in countries with lower labour costs, where workers may face poor working conditions or low wages.

Ethical sourcing, fair trade practices, and recycling initiatives can help mitigate these impacts.

Use of Material Properties in Commercial Products

The choice of materials is vital for both electronic and mechanical systems, as they must be suited to the specific demands of the product:

    Electronic Systems:

• Conductivity: Materials such as copper and gold are used for electrical wiring because they conduct electricity efficiently. Silicon is used in semiconductors for its ability to control electrical current.
• Insulation: Materials like PVC (Polyvinyl Chloride) and Teflon are used to insulate wires and components to prevent short circuits and electrical hazards.
• Thermal management: Components like aluminium and ceramic are used in heat sinks and casings to dissipate heat and prevent overheating in devices like computers and mobile phones.

    Mechanical Systems:

• Strength and hardness: Metals like steel and titanium are used for structural components that must withstand significant mechanical stress, such as gears, levers, and frames.
• Lubricity and wear resistance: Materials like brass, bronze, and nylon are used for bearings, bushings, and gears due to their resistance to friction and wear.
• Flexibility: In some systems, such as springs or flexible couplings, materials like stainless steel or rubber are used for their ability to bend without breaking.

The properties of materials are matched to their specific roles within a system to ensure maximum efficiency and longevity.

Stock Forms, Types, and UK Sizes

Stock forms and types of materials vary depending on the nature of the system being designed. Key stock forms for both electronic and mechanical systems include:

    Electronic Components:

• Resistors, capacitors, inductors, and diodes are commonly sold in standard sizes based on their voltage, resistance, and current ratings. These components are typically purchased in packets or bulk and are often small, modular, and standardised to fit into printed circuit boards (PCBs).
• Wires and cables: Available in various thicknesses (measured in gauge) and insulation types, such as PVC or Teflon, to match the required electrical properties and environmental conditions.

    Mechanical Components:

• Metals such as steel, aluminium, and brass are available in bars, sheets, and tubes, typically in standard UK sizes like 20mm x 20mm bars or 1m x 2m sheets. These materials are often processed into final components via cutting, milling, and welding.
• Springs, gears, and bearings come in standard sizes, which are often specified by ISO (International Organization for Standardization) or other industry standards.
• Pipes and tubing come in standard diameters (e.g., 15mm, 22mm, 50mm) depending on the material and application.

Standard stock forms ensure that materials are easy to source and fit into existing production processes.

Scales of Production

The scale of production impacts both material choice and manufacturing methods:

• One-off production: In small-scale or bespoke manufacturing, such as custom-made mechanical parts or electronics (e.g., prototypes or high-end products), more expensive materials and precise manufacturing techniques are often used. For example, titanium might be used for a custom aerospace component, and hand-soldering might be used for delicate electronic circuits.
• Batch production: For intermediate quantities, such as limited runs of products or seasonal electronics (e.g., smart devices or small appliances), materials like aluminium, steel, and polycarbonate are chosen for their cost-effectiveness and suitability for mass production. Batch production uses tools like CNC machines and injection moulding.
• Mass production: Large-scale production, such as in the manufacture of consumer electronics or automotive parts, requires high-volume manufacturing methods like injection moulding, die-casting, and automation. Plastic and steel are commonly used for their durability, cost-effectiveness, and ease of mass production.

Each scale of production has its own set of challenges and requires appropriate material selection, manufacturing processes, and quality control measures.

Tools, Equipment, and Processes

The tools, equipment, and processes used in the production of electronic and mechanical systems vary depending on the complexity of the system:

    Electronic Systems:

• Soldering irons and soldering stations are used for connecting electronic components to PCBs.
• Pick and place machines are used in high-volume production to place components onto PCBs accurately.
• Circuit board etching: This process uses laser cutters or chemical etching to create the pathways on printed circuit boards.
• Surface-mount technology (SMT) and through-hole technology (THT) are used to assemble components onto boards.

    Mechanical Systems:

• CNC (Computer Numerical Control) machines are used to cut, mill, and shape metals, plastics, and composites to create precise mechanical components like gears, shafts, and housings.
• Injection moulding is used for creating plastic components like housings for electronic devices, and die-casting is used for metal parts such as engine blocks.
• Welding, riveting, and screwing are common methods for joining mechanical parts.
• Casting is often used to create larger components, such as engine parts or frames.

These tools and processes allow manufacturers to create products with high accuracy, efficiency, and repeatability.

Commercial Processes

Commercial processes are essential for scaling production and ensuring that products meet design specifications and consumer demands:

• Injection moulding: A common process for producing plastic parts, such as casings for electronics or components for automotive systems. It allows for high-volume production with consistent quality and precision.
• Casting: Used for creating complex shapes, especially for metal parts like engine components. Materials like aluminium and zinc are commonly used.
• Welding: Essential for joining metal parts in mechanical systems. MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding are commonly used in manufacturing for their precision and strength.
• Assembly lines: Used in high-volume production of both electronic and mechanical systems. These lines allow for the efficient assembly of components into final products.
• Quality assurance and testing: Ensures that the finished products meet safety standards, function correctly, and are free of defects. This can involve automated testing systems, visual inspections, and stress testing.

Accuracy and Quality Control

In both electronic and mechanical systems, accuracy and quality control are vital to ensure that the products meet the required standards and function properly:

• Tolerance levels: In mechanical systems, tolerances define the acceptable variation in the dimensions of parts. Tight tolerances are crucial in systems like engines or transmissions, where precise measurements ensure proper functioning.
• Calibration: In electronic systems, ensuring components like resistors and capacitors are correctly calibrated is essential to ensure circuits perform as expected.
• Testing and inspection: Throughout the production process, testing systems and visual inspections ensure that parts meet design specifications. For example, automated test rigs might check the performance of motors, while multimeter testing ensures that electronic circuits function correctly.
• Six Sigma and Lean Manufacturing: These methodologies are used to minimise defects and waste in production processes, ensuring high-quality products at lower costs.

Quality control processes are integral to maintaining the reliability and safety of both electronic and mechanical systems.

Summary

Electronic and mechanical systems are complex, and their design and production require a deep understanding of material properties, forces and stresses, manufacturing techniques, and quality control. By selecting the right materials, choosing appropriate manufacturing processes, and maintaining strict quality control, designers and manufacturers can ensure that these systems perform reliably and sustainably.