MANUFACTURING

1. MANUFACTURING (Lecture 2)

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

3. 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

4. Forming Processes • 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 Casting with a two-piece mold

5. Fenders Bumpers Trunk Lids Doors Hoods Some parts of an automobile that are made through pressing 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 Rolling of a slab

6. 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

7. 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

8. 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

9. 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

10. Material Removal Processes • Sawing A power hacksaw A vertical bandsaw

11. 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

12. 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

13. 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

14. 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