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UNM ME 260L - ME 260L Lecture Notes

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Group 9 3 / 1 / 2006 Ch. 15: Extrusion and Drawing of Metal Ch. 16: Sheet-Metal Forming ProcessCHAPTER 1515.1 IntroductionProducts Made by ExtrusionsEconomics of ExtrusionsDrawingSlide 715.2 The Extrusion ProcessSlide 9VariablesExtrusion ForceSlide 12Metal FlowSlide 1415.3 Hot ExtrusionSpecial RequirementsDie DesignSlide 18Slide 19Die MaterialsLubricationSlide 22Slide 2315.4 Cold ExtrusionSlide 25Slide 2615.5 Extrusion DefectsSlide 2815.6 Extrusion Equipment15.7 The Drawing ProcessSlide 31Slide 3215.8 Drawing PracticeSlide 34Slide 3515.9 Drawing Defect and residual Stresses15.10 Drawing EquipmentSlide 38IntroductionShearingSlide 41Slide 42Shearing OperationsSlide 44Slide 45Punches and DiesPunches and DiesSheet-Metal Characteristics and FormabilitySlide 49Formability Tests for Sheet-MetalsSlide 51Bending Sheets, Plates, TubesSlide 53Slide 54Ch.16 Sections 16.6 - 16.916.6 Miscellaneous Bending and Related OperationsSlide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 6716.7 Deep DrawingSlide 69Slide 70Slide 71Slide 72Slide 7316.8 Rubber Forming16.9 SpinningSlide 76Slide 77Diffusion Bonding/Superplastic FormingSpecialized Forming ProcessesExplosive formingMagnetic-pulse formingSlide 82Manufacturing of Metal Honeycomb StructuresDesign Considerations in Sheet-Metal FormingEquipment for Sheet-Metal FormingEconomics of Sheet-Forming OperationsReferencesGroup 93 / 1 / 2006Ch. 15: Extrusion and Drawing of MetalCh. 16: Sheet-Metal Forming ProcessDavid OrtegelSteven NeidigkTim NgoJason MaestasCHAPTER 15Extrusion and DrawingOfMetalsExtrusionRooted From Latin Term “Extrudere”(To Force out).A Cylindrical Billet is Forced Through A DieSame Concept as forming Play-DoeDie Geometry remains constant throughout the operationForms a constant extruded cross-sectionAluminum, copper, Steel Magnesium, lead are the most common material used in the Extruding process15.1 IntroductionProducts Made by ExtrusionsRailings for Sliding DoorsWindow FramesAluminum LaddersExtrusions can be cut into desired lengths, allowing for discreet parts such to be produced as Gears, and BracketsEconomics of ExtrusionsExtrusions can be economical for Large productions runs as well as short ones.Tool cost is generally low Manufactures are able to produce quantity because of the ability to cut individual parts from a single extrusionDrawingDrawing – Cross-sections of solid rod, wire, or tubing is reduced or changed in shape by pulling through a die.•Developed between 1000 -1500 AD•Used to from shafts, automobile components, spindles, fasteners.Depending on the ductility pf the material used extrusions can be caries out various ways:1. Cold Extrusion – Extrusion carried out a ambient temperature. Often combined with forging operations2. Hot Extrusions – Extrusions carries out at elevated temperatures3. Impact extrusion – punch is rapidly descends on billet material4. Hydrostatic extrusion – pressure is applied by a piston through incompressible fluid medium surrounding the billet15.2 The Extrusion Process3 Basics Types of Extrusion:•Direct or Forward Extrusion: A billet is placed in a chamber and forced hydraulically through a die by a ram. Fig a•Indirect Extrusion (Reverse, Inverted, Backward Extrusion): The Die Moves Toward the billet material. fig b• Hydrostatic Extrusion: –A Billet that is smaller that the chamber is used. –The Chamber is filled with a fluid. Pressure is then applied to the pressing stem–There is no friction to overcomeVariables•Die Angle•A ۪ – Initial cross-sectional Area•A – Final cross-sectional AreaExtrusion ForceThe force required for extrusionsF = A*k*ln( A ۪ / A )k = Constant determined experimentally•The force required depends on:–Strength of Billet Material–Extrusion Ratio: A ۪ /A–Friction between the billet material and the chamber–Temperature–Speed of the Ram–Type of lubricants usedExtrusion constant k for various metals at different temperatureMetal FlowFlow patterns influence the quality and mechanical properties of the extruded productMaterial flows longitudinally (ex. Fluid flowing in a channel)The extruded product has a elongated grain structure-A common technique in investigating a flow is to section the round billet in half-Dead-Metal Zone – The corner of the material stays stationary. Bright finishes result due to material flowing past the die angle-Fig a – flow patterns attained with low friction-Fig b – flow patterns attained with high friction-Fig c – flow pattern attained with high friction or cooling of the billets outer regions in the chamber15.3 Hot ExtrusionExtrusions carried out at elevated temperaturesUsed for metals that do not have sufficient ductility at room temperature.Used when wanting to reduce forces on billet materialSpecial RequirementsDue to excessive heat die wear becomes excessive and rapid cooling of the product after extrusion causes deformations. Pre-heated dies prolong the life of the die done my hot forging. This also reduces rapid cooling if the materialBillet develops an oxide film. Oxides can result in a finished product that is unacceptable.Placing a dummy block, a little smaller than the chamber ahead of the ram, results in a thin shell of the oxide layer left in the container. CLead 200–250Aluminum and its alloys 375–475Copper and its alloys 650–975Steels 875–1300Refractory alloys 975–2200Die Design Main types of die designs:1) Square dies: Used in extruding nonferrous metals- Develops dead metal zones that form the dies angle2) Solid or Hollow Dies: Used in extruding tubing products- The ram is fitted with a mandrel that pierces a hole in the billet-Wall thickness is limited to 1 mm for aluminum. 3mm for stainless steels, 5mm to stainless steels3) Spider, porthole dies ,and bridge dies: Used in creating hollow cross-section extrusions-Created by welding chamber methods-Metal divides and flows around the supports for the internal mandrel-The extruded strands become welded back together by the high internal pressure existing in the chamberonly suitable for aluminum and its alloys because of their capacity to create strong welds.(a)(b)(c)Die MaterialsHot Worked dies Steels are used for hot extrusionCoatings such as zirconia used to extend die life•Not suitable for dies used for complex shapes because of the sever stress gradients that

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