Manufacturing Processes II PDF - Forming Technology - Part I

Manufacturing Processes II ET22033 Forming Technology – Part I Eng. (Mr) Amalka Samarathunga BSc Eng Mechanical Engineering, M...

Manufacturing Processes II ET22033 Forming Technology – Part I Eng. (Mr) Amalka Samarathunga BSc Eng Mechanical Engineering, Mphil (Reading) Department of Engineering Technology, Sabaragamuwa University of Sri Lanka Manufacturing Process II- Syllabus Outline Casting Technology Sand casting, process and accessories, Shell moulding, Slurry processes, Investment casting, Die-casting, Centrifugal casting, Continuous casting, Melting practice, Casting properties and defects, Basic mould design. Casting defects and prevention Forming Technology Cold and hot forming, press work, punching, blanking, piercing, rolling, extrusion, cup drawing, wire drawing, drawing parameters, Forming defects and prevention Fabrication and welding technology Fitting, limits and fits, tolerances, Joining and welding methods, process parameters for gas and arc welding, welding fixtures, welding defects and prevention Polymer moulding Introduction to Injection moulding, Compression moulding, blow moulding, GRP moulding, moulding defects and prevention 2  Acknowledgement ✓ All the authors of original materials (figures, photos, diagrams and etc.) ✓ Manufacturing Engineering and Technology, Sixth edition - Serope Kalpakjian, Steven R. Schmid, HamldonMusa ✓ A Textbook of Workshop Technology, - R.S Khurmi, J. K Gupta ✓ Lecture notes;- by Dr. J.R Gamage, Department of Mechanical Engineering, University of Moratuwa 6/17/2022 Engineering Technology 3  What is forming? A Mechanical Deformation Process on metals The workpiece is reshaped without adding or removing material, and its mass remains unchanged 6/17/2022 Engineering Technology 4  What is forming? Forming is changing the shape of a metal using its plastic deformation 5  Effect of Carbon as the alloying element of Steel Low-carbon steel, also known as mild steel, contains under 0.3 percent carbon. It’s known for being easier to weld and machine than higher-carbon steels, and it’s softer and more pliable. Mild steel is also the least expensive type of steel. Medium-carbon steel contains between 0.3 percent and 0.6 percent carbon. It offers a balance of workability, price and durability. Medium-carbon steel is often used for automotive and machine parts. High-carbon steel is steel that contains between 0.6 percent and 2 percent carbon. It’s extremely hard and is often used for tools, cookware and knife blades. However, its hardness can make it more brittle than some other steels, and it’s difficult to weld and machine. 6  Overview of Metal Forming Manufacturing process in which plastic deformation is used to change the shape of metal workpieces The tool, usually called a die, applies stresses that exceed the yield strength of the metal 7  Overview of Metal Forming…Stresses Stresses to plastically deform the metal are usually compressive E.g. rolling, forging, extrusion However, some forming processes, Stretch the metal (tensile stresses) Others bend the metal (tensile and compressive) Still others apply shear stresses 6/17/2022 Engineering Technology 8  Overview of Metal Forming…Material Properties Desirable material properties: Low yield strength High ductility These properties are affected by temperature: Ductility increases and yield strength decreases when work temperature is raised Other factors: Strain rate and friction 6/17/2022 Engineering Technology 9  Volume/Bulk Deformation Process Operations that induce shape changes on the metal work piece by plastic deformation under forces applied by various tools and dies. Starting forms of metals: Cylindrical bars and billets Rectangular billets and slabs and similar shapes The cross section of the workpiece changes without changing the volume This process is occurring by stressing metal sufficiently to cause plastic flow into desired shape 10 Volume/Bulk Deformation Process Performed as cold, warm, and hot working operations Hot working - significant shape changes Cold working- Improved strength during shape change Advantages: Produces common shapes inexpensively. Good mechanical properties. 11 Basic Types of Metal Forming Processes 1. Bulk deformation Rolling processes Forging processes Extrusion processes Wire and bar drawing 2. Sheet metalworking Bending operations Deep or cup drawing Shearing processes 12 13 14 Classification of Bulk Deformation Process Based on Working Temperature Depending on the temperature that the forming process is carried out, Cold Forming Warm Forming Hot Forming 15 Classification of Bulk Deformation Process Based on Working Temperature 16 Classification of Bulk Deformation Process Based on Working Temperature 17 Classification of Bulk Deformation Process Based on Working Temperature 18  Bulk Deformation Process a) Rolling – slab or plate is squeezed between opposing rolls b) Forging – work is squeezed and shaped between opposing dies c) Extrusion – work is squeezed through a die opening, thereby taking the shape of the opening d) Wire and bar drawing – diameter of wire or bar is reduced by pulling it through a die opening 19 Rolling Process 20 1. Rolling Deformation process in which work thickness is reduced by compressive forces exerted by two opposing rolls The rolling process (flat rolling) 21 1. Rolling 22 Rolling Mill Configurations 23 Rolling Mill Configurations 24 Rolling Need to carryout rolling prior to cooling - cooler surfaces will tend to resist deformation 25  Types of Rolling By geometry of work Flat rolling: Used to reduce thickness of a rectangular cross section Shape rolling: a square cross-section is formed into a shape such as an I beam By temperature of work Hot Rolling – most common due to the large amount of deformation required Cold rolling – produces finished sheet and plate stock 6/17/2022 Engineering Technology 26  1. Rolling https://www.youtube.com/watch?v=KRn73gKQ2YU 6/17/2022 Engineering Technology 27  Some of the steel products made in a rolling mill Products: plates & sheets - plates are used for structural applications like bridges, ships and nuclear vessels while sheets (generally 6mm or less in thickness) are used for automotive, 6/17/2022 beverage cans, office & kitchen equipment. Engineering Technology 28  Types of Rolling Rolling Thread Ring Shape Gear Rolling Rolling Rolling Rolling 6/17/2022 Engineering Technology 29  1.1 Thread Rolling Used to form threads on cylindrical parts by rolling them between two dies Commercial process for mass producing bolts and screws Performed by cold working in thread rolling machines Advantages over thread cutting (machining): Higher production rates Better material utilization Stronger threads due to work hardening Better fatigue resistance due to compressive stresses introduced by rolling With the increase in strain hardening, the resistance to deformation of a material increases and the material becomes capable of carrying a higher amount of load in a smaller contact area 6/17/2022 Engineering Technology 30 Work hardening is a general characteristic in metal forming 31  1.1 Thread Rolling 6/17/2022 Engineering Technology 32 1.1 Thread Rolling 6/17/2022 https://www.youtubeE.ncgionemerin/g wTecahntocloghy?v=MvWmH3Dr52o 29  1.2 Ring Rolling A thick-walled ring of smaller diameter is rolled into a thin-walled ring of larger diameter Hot working process for large rings and cold working process for smaller rings Applications: Ball and roller bearing races, steel tires for railroad wheels, and rings For pipes, pressure vessels, and rotating machinery Advantages: ✓ Material savings ✓ Ideal grain orientation ✓ Strengthening through cold working ✓ Good mechanical properties 34 1.2 Ring Rolling Ring rolling used to reduce the wall thickness and increase the diameter of a ring: (1) start, and (2) completion of process 35 1.2 Ring Rolling 32  1.3 Shape Rolling Work is deformed by a gradual reduction into a contoured cross section (I-beams, L-beams, U-channels, rails, round, square bars and rods, etc.) 6/17/2022 Engineering Technology 37  1.4 Gear Rolling Gear rolling is similar to thread rolling with three gears (tools) that form the gear profile on the work 6/17/2022 Engineering Technology 38  Thank You! 6/17/2022 Engineering Technology 39