Green Design and Manufacturing

• The presentation is for IE 366: Manufacturing Processes (1), Part 2, by Prof. Mohammed Hayajneh.
• The presentation covers green design and manufacturing, material selection, and manufacturing process selection.

Green Design and Green Manufacturing

• Green design and green manufacturing are common in industrial activities.
• There is a major emphasis on Design For Environment (DFE), which is also called environmentally conscious design and manufacturing.
• This approach considers all potential adverse environmental impacts from materials, processes, operations, and products early in the design and production phases.
• The goals of green design have led to the concept of Design For Recycling (DFR).
• Recycling involves two basic activities: biological cycle and industrial cycle.
• Manufacturing operations often produce waste, including chips from machining, slag from foundries/welding, additives from sand-casting, hazardous waste, lubricants/coolants, liquids from heat treating/plating, solvents, and smoke/pollutants.
• Guidelines for green design and manufacturing include reducing material waste, and the use of hazardous materials, investigating environmentally friendly manufacturing technologies, improving recycling methods, minimizing energy use, and encouraging recycling.
• Design for the Environment principles include energy efficiency, minimum residues, optimal materials, and recycling.

Material Selection

• Material selection considers cost, reliability, ease of joining, electrical properties, mechanical properties, and ease of fabrication.
• Types of material considerations include: material properties (mechanical, physical, chemical, electrical, optical, magnetic), manufacturing properties, cost, reliability, appearance, service life, availability, and recyclability.
• Engineering materials include metals (ferrous and nonferrous), plastics (thermoplastics, thermosets, elastomers), ceramics, and composites.

Material Properties: Mechanical Behavior

• The tension test can be used to determine the stress-strain curve for materials.
• Material properties can be defined through means of strength, hardness, toughness, and stiffness.
• Hardness is the resistance of a material to localized plastic deformation or indentation.
• Creep is the tendency of a solid material to move slowly or deform permanently under mechanical stresses.
• Toughness (Impact Resistance) describes the ability of a material to absorb energy and plastically deform without fracturing.
• Material fatigue is a phenomenon where structures fail when subjected to a cyclic load.
• Physical properties of materials include density, melting point, specific heat, thermal conductivity, and thermal expansion.

Material Properties: Introduction and Other Considerations

• Electrical, magnetic, optical, and corrosion resistance are important material properties.
• Copper is used in electrical wires because of its electrical properties.
• Aluminum, stainless steel, and copper are commonly used in cookware.
• Wood or plastic are common for cookware handles.
• Thermal conductivity is the rate at which heat flows through a material.
• Metals generally have high thermal conductivity, while nonmetals have poor conductivity.
• High thermal conductivity is related to the ability to remove heat or create specific thermal gradients.
• The coefficient of thermal expansion is generally inversely proportional to the melting point of the material.
• Low-expansion alloys have been developed to mitigate thermal expansion problems.
• Corrosion resistance is an important aspect of material selection, depending on material composition and environment of use. Metals, ceramics and plastics are all subject to forms of corrosion, although corrosion typically refers to metals/ceramics and degradation refers to plastics.
• Corrosion can be uniform (surface), pitting (localized), or result in cracking.
• Key considerations include castability, weldability, and machinability.

Manufacturing Process Selection

• Manufacturing process selection considers dimensional accuracy, surface finish, and manufacturing cost.
• Dimensional accuracy, surface finish, manufacturing cost, tolerance, capital cost, labour cost, wall thickness, mass, complexity, tooling cost, processing time, and production rate/volume are all manufacturing selection criteria.
• The size, thickness, and shape complexity have a major bearing on the manufacturing process.
• A flat part with a thin cross-section cannot be cast properly.
• Complex parts cannot be formed using only one, easy manufacturing process.
• Tolerances and surface finish in hot-working operations are not as good as those in cold-working.
• Manufacturing processes generally involve solidification, shaping, deformation, material removal, property enhancing, surface processing, permanent joining, and/or mechanical fastening operations.
• Casting, forming and shaping, sheet metal processing, polymer processing, machining, and joining are common manufacturing processes.
• Improper material selection can lead to: the component stops functioning; it does not function properly, with the required specifications; it becomes unreliable or unsafe for future use.
• Net-shape and near-net-shape manufacturing is an important methodology where a part is made in only one operation and at or close to the final desired dimensions, tolerances, and surface finish.

Types of Production

• Job shops: Small lots, <10, use general-purpose machines with computer controls.
• Small-batch production: Quantities 10-100, uses similar machines to job shops.
• Batch production: Lot sizes 100-5000, uses more advanced machinery with computer control.
• Mass production: Lot sizes >100,000, uses special-purpose machinery and automated equipment.