MANUFACTURING (Lecture 2)

Manufacturing Processes Processes add value to materials A process involves a number of steps or operations Four basic processes applied on production materials are forming, material removal, assembly (or joining) and conditioning Forming operations change the geometry of the starting material without cutting it Material removal or separating processes remove a part of the starting material using a tool to get the desired geometry Combining processes join two materials or deposit material onto the exterior surface of the starting material Conditioning processes add value to the starting material by improving its internal and physical properties

Forming Processes Casting A material in a liquid or semisolid form is poured or forced to flow into a mold cavity and allowed to solidify, thus taking the solid shape of the cavity The process can be applied on metals, ceramics and plastics The term casting is commonly used for metals The term molding is used for plastics Examples of molds – cake-pan, an ice-cube-tray or the footprints on a beach Types of castings – sand casting and die casting Sand casting – pouring molten metal into a sand mold, breaking up the mold to remove the casting Sand casting requires a pattern – a full sized model of the part Die casting is a permanent-mold-casting – molten metal is injected into the mold cavity under high pressure Molds for die casting are named as dies

Forming Processes Pressing Casting with a two-piece mold Pressing Pressing is commonly used for majority of sheet metal parts of an automobile A measured amount of material is poured into a mold. A plunger with its own shape is lowered to force the material to spread out and fill the mold The material is forced into the shape of the mold at the bottom and the shape of the plunger at the top Mechanical or hydraulic presses are used The plunger and the base of a forming die transform the sheet metal into the required shape – drawing – fuel tank of a motorbike

Forming Processes Pressing Rolling is a type of pressing – thickness of the starting material is reduced by compressive forces exerted by two opposing rolls Great pressure can make the powdered metal into a solid. The material is then heated to make the object hard – sintering Some parts of an automobile that are made through pressing Fenders Bumpers Trunk Lids Doors Hoods Rolling of a slab

Forming Processes Forging The oldest metal forming operation Work part is heated and compressed using either impact or gradual pressure part Forging machine applying an impact load – forging hammer Forging machine applying gradual pressure – forging press Examples – high-strength components for automotive and aircrafts like engine crank shafts and connecting rods, gears, aircraft structural components, and jet engine turbine parts

Extruding a red hot metal Forming Processes Extrusion A compression process in which the work metal is forced to flow through a die opening, thereby taking the shape of the opening as its own cross-section Toothpaste is a very good example of the process Different shapes are possible especially with hot extrusion The end product does not require much more shaping and machining Extruding a red hot metal

Forming Processes Blow Molding Air pressure is used to inflate soft plastic into a mold cavity One-piece hollow plastic parts with thin walls are possible, such as bottles and similar containers The technology is borrowed from the glass industry with which plastics compete in the disposable or recyclable bottle market

Material Removal Processes Operations that remove excess material from the starting workpiece to get the desired geometry Use of knives and scissors is a common example Important processes – shearing, sawing and machining operations such as turning, drilling and milling, shaping and planing and grinding Nontraditional processes – lasers, filters, magnets and electrochemical energy Sawing A narrow slit is cut into the workpiece by a tool consisting of a series of narrowly spaced teeth Most sawing operations – work is held stationary and saw blade is moved relative to it Types – hacksawing and bandsawing Hacksaw blade – thin straight tool with cutting teeth on one edge Bandsaw blade – endless flexible loop with teeth on one edge – pulley-like drive mechanism

Material Removal Processes Sawing A power hacksaw A vertical bandsaw

Material Removal Processes Shearing Metal cutting operation along a straight line between two cutting edges – similar to using a pair of scissors Typically used to cut large sheets into smaller sections for subsequent pressworking operations Other similar processes are blanking and punching Shearing Blanking and punching

Material Removal Processes Turning Cutting tool with a single cutting edge – rotating workpiece to generate a cylindrical shape Turning is commonly performed using a lathe Drilling Used to create a round hole A rotating tool that has two cutting edges The holes can be made from 1/10,000 of an inch to 3½ inches Milling Rotating tool with multiple cutting edges – plane or straight surface Types – vertical milling and horizontal or face milling

Material Removal Processes Shaping and Planing Single-point cutting tool moved linearly relative to the workpiece Creating a straight, flat surface Shaping – tool provides the speed motion and the workpiece remains static Planing – workpiece provides the speed motion while the tool remains motionless. Grinding Used to provide surface finish and the uniform thickness of the workpiece Abrasive particles are used – sand paper or grinding wheel Abrasives – very small crushed particles of hard materials like aluminum oxide and silicon carbide Grinding wheel – usually disk-shaped, precisely balanced for high rotational speeds Common forms of grinding – polishing, buffing and the use of toothpaste Grinding tools

Assembly Processes Two or more separate parts are joined to form a new entity Components are connected – permanently or semi permanently Types – mechanical methods, thermal methods and adhesive bonding Mechanical Assembly Various fastening methods – use of hardware components, called fasteners Products using mechanical assembly – automobiles, large and small appliances, telephones, furniture, utensils and wearing apparels Categories – nails, threaded fasteners and rivets Mechanical assembly is often preferred for its ease of assembly and disassembly Nails are commonly used for wood – finishing nails, box nails and common nails