Manufacturing process I Course Supervisor Walid Khraisat
. Course Objectives The following basic course objectives are expected to be achieved during the course Be able to discuss/explain the importance of understanding the mechanical behavior of materials in manufacturing. Understand the concepts of yield criteria and the different mathematical formulas related to them and their applications Be able to discuss/explain the different bulk deformation processes. Be able to analyze the different bulk deformation processes and identify their advantages and disadvantages. Be able to discuss/explain the different sheet-metal forming processes. Be able to analyze the different sheet-metal forming processes and identify their advantages and disadvantages. Solving manufacturing problems in terms through the calculations of force, power and pressure requirements as well as estimating temperature rise during metal forming operations. Be able to solve engineering problems related to metal forming operations and identify proper toolings
Expected Outcomes 1-An ability to apply knowledge of mathematics, science, engineering, and management 2-An ability to function on multi-disciplinary teams 3-An ability to identify, formulate, and solve engineering problems 4-A knowledge of contemporary issues related to manufacturing processes Textbook(s) and Readings Kalpakjian S., and Schmid S. 2008. Manufacturing processes for engineering materials. Fifrth edition, Prentice-Hall, Inc.
Course Outline Introduction to Manufacturing Engineering Fundamental of mechanical behavior of materials: tension, compression, torsion, bending, hardness, fatigue, creep, impact, residual stresses, tri axial stresses and yield criteria, and work deformation. Bulk deformation processes: forging, rolling, extrusion, and rod and wire drawing Sheet metal forming processes: sheet metal characteristics, shearing, bending of flat sheet and plate stretch forming
Course Content Introduction to Manufacturing Engineering Review of Mechanical properties of materials: Metals polymers Yielding Criteria Tresca Von Mises Manufacturing Process Bulk deformation Processes in Metal working Sheet metal working
What is Manufacturing Manufacture is derived from two Latin words manus (hand) and factus (make); the combination means made by hand manufacturing means production of hardware, which ranges from nuts and bolts to digital computers and military weapons, as well as plastic and ceramic products
Manufacturing Demands Meet design requirements, specifications and demands Economical and environmental friendly Quality from design to aasembly Flexible production methods New developments in materials, production methods and computer integration must be evaluated Manufacturing activities must be integrated in large system Customer feedback Higher productivity
Manufacturing systems The basic components in manufacturing systems
Flexibility Quality Low Cost Speed
What is Design for Manufacture (DFM?) DFM is the concept that says you can't treat the design of a part as a separate process from its manufacture. Planning for manufacturing must be done within the context of the design process. When designing a part, the designer must consider -- design requirements -- part specifications and standards -- economics and efficiency of manufacture DFM is a comprehensive approach to the production of goods, and it integrates the design process with materials, manufacturing methods, process planning, assembly, testing, and quality assurance..
Manufacturing Processes 4 basic process Casting Forming Material Removal Joining Other processes Finishing Painting
Bulk processes rolling extrusion forging solid- and/or hollowsection drawing. Sheet Forming Bending, pressing, Deep drawing spinning shearing
Rolling: Compressive deformation process in which the thickness of a plate is reduced by squeezing it through two rotating cylindrical rolls. Forging: The workpiece is compressed between two opposing dies so that the die shapes are imparted to the work. Extrusion: The work material is forced to flow through a die opening taking its shape Drawing: The diameter of a wire or bar is reduced by pulling it through a die opening (bardrawing) or a series of die openings (wire drawing)
Classification of Forming processes
criteria of classifying metal-forming processes operational temperature (hot, warm or cold forming), shape effect (bulk or sheet forming), operational stress system, operational strain rate, starting material (ingot, slab, billet, bloom, slurry, or powder).
Operational Temperature
Recrystallisation temperature defines hot and cold working Cold Working: working at room temperature, T<0.3T m. Advantages: no oxidization, tighter tolerances, better surface finish, thinner walls, higher strength, easier lubrication. Disadvantages: high tool pressures, deformation forces, equipment power, low material ductility. Hot Working: working with preheated materials, T>0.5T m. Advantages: force and power requirements low, ductility high Disadvantages: takes extra energy to heat the workpiece, oxidization, impaired surface finish, wide dimensional tolerances. Nonisothermal forming: tool much colder than workpiece. Isothermal forming: tool same temperature as workpiece. Warm Working: in between cold working and hot working 0.3T m <T<0.5T m
Cold Working Performed at room temperature or slightly above Many cold forming processes are important mass production operations Minimum or no machining usually required These operations are near net shape or net shape processes
Advantages of Cold Forming vs. Hot Working: Betteraccuracy, closer tolerances Bettersurface finish Strain hardening increases strength and hardness Grain flow during deformation can cause desirable directional properties in product No heating of work required (less total energy)
Disadvantages of Cold Forming Equipment of higher forces and power required Surfaces of starting workpiece must be free of scale and dirt Ductility and strain hardening limit the amount of forming that can be done In some operations, metal must be annealed to allow further deformation In other cases, metal is simply not ductile enough to be cold worked
Warm Working Performed at temperatures above room temperature but below recrystallization temperature Warm working: T/Tm from 0.3 to 0.5 Advantages of Warm Working: Lower forces and power than in cold working More intricate work geometries possible Need for annealing may be reduced or eliminated
Hot Working Deformation at temperatures above recrystallization temperature In practice, hot working usually performed somewhat above 0.5Tm Metal continues to soften as temperature increases above 0.5Tm, enhancing advantage of hot working above this level
Why Hot Working Capability for substantial plastic deformation of the metal far more than possible with cold working or warm working Why? Strength coefficient is substantially less than at room temp. Strain hardening exponent is zero (theoretically) Ductility is significantly increased
Effects of Cold Working Schematic illustration of loading and unloading of a tensile-test specimen. Note that yield stress increases and ductility decreases with prior cold work.
Process Annealing Process Annealing: remove the effect of cold working for finished product. Process annealing: softening for further processing. Recovery: 0.3-0.5 Tm, restore ductility without changing grain structure. Recrystallization: >0.5 Tm, large dislocation by cold working, high strength, reasonable ductility. Avoid very light cold work (2-4%). Avoid using prolonged time.
Shape-effect criterion A process in which a component of a relatively small initial surface area/thickness ratio is deformed in such a way that the ratio is increased, is often classed as a 'bulk deformation the component Of an initially high surface area/thickness ratio, shaped in a process which does not impose any change in the thickness but effects shape changes only, is said to be 'sheet formed'.
Bulk processes are rolling extrusion forging solid- and/or hollowsection drawing. Sheet Forming Bending, pressing, Deep drawing spinning shearing