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Plastics and Injection Molding

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Plastics and Injection MoldingPlasticsVariety of Plastics & Plastics ProcessesExtrusionCalendaringThermoformingCastingLess Common MethodsMoldingCompression MoldingTransfer MoldingRotation MoldingReaction Injection MoldingBlow Molding, BottlesBlow Molding, Plastic BagsInjection MoldingSlide 17Injection Mold LayoutPlunger Type Injection Molding PressScrew Type Injection PressesInjection Molding ScrewsScrew Configuration DesignBarrier Flight ScrewsPress ParametersClamping MechanismsInjection Molding DefectsShort ShotFlashWeld LinesJettingEjector Pin MarksSink MarksWarpage/Residual StressesWarpage DefectsGate, Sprue, and Runner SystemRunner DesignRunner Cross SectionsSlide 38Gate DesignVentingRunner & Gate Sizing ‘Classic Method'Estimating Pressure DropViscosity in Non-Newtonian FluidsDetermining the ViscosityTables of Mass Flow IndexSlide 46Some Plots of ViscositySlide 48Slide 49Approximating Curves of  vs Additional GeometriesExample: Iterative Mold LayoutExample: Determining FlowSlide 54Example: Determining Shear Flow RateExample: Determining ViscosityExample: Estimating Pressure DropExample: More Pressure DropsExample: Iterate to Get Similar DropsRunner Sizing- Bryce’s MethodGate Sizing- Bryce’s MethodVent Sizing & Position- Bryce’s MethodMold Design ExampleExample- Runner DesignExample- Upstream RunnersExample- GatesExample- VentsEstimating Clamping ForceExample- Clamping ForceCommon PolymersSlide 71Common Shaping Processes for ThermoplasticsCommon Shaping Processes for ThermosetsSummaryCreditsDisclaimerDepartment of Mechanical Engineering, The Ohio State UniversitySl. #1GATEWAYGATEWAYPlastics and Injection MoldingDepartment of Mechanical Engineering, The Ohio State UniversitySl. #2GATEWAYGATEWAYPlasticsAdvantagesLight WeightHigh Strenght-to-Weight RatioComplex Parts - Net ShapeVariety of Colors (or Clear)Corrosion ResistantElectrical InsulationThermal InsulationHigh Damping Coefficient“Low” pressures and temp requiredDisadvantagesCreepThermally Unstable- Can’t withstand Extreme HeatU-V Light SensitiveRelatively low stiffnessRelatively low strengthDifficult to Repair/ReworkDifficult to Sort/RecycleDepartment of Mechanical Engineering, The Ohio State UniversitySl. #3GATEWAYGATEWAYTwo basic types of plasticsThermoset- Heat hardening/ Undergoes chemical changeThermoplastic- Heat softening/ Undergoes physical changeA wide variety of plastic manufacturing processes existExtrusion ExpansionLamination (Calendering) Solid-Phase Forming Thermal Forming CastingFoaming SpinningMolding• compression, transfer, blow, rotational, injectionVariety of Plastics & Plastics ProcessesDepartment of Mechanical Engineering, The Ohio State UniversitySl. #4GATEWAYGATEWAYExtrusionExtrusion process•most common manufacturing of plastic resin•combines pigments, additives and resin•high heat, high pressure  molten mixture•pushed through die•create warm plastic for possible further “finishing” operation such as pelletizing, calendaring, or moldingFigure ref: Process Selection, KG Swift and JD Booker, p. 64.Department of Mechanical Engineering, The Ohio State UniversitySl. #5GATEWAYGATEWAYCalendaringRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Department of Mechanical Engineering, The Ohio State UniversitySl. #6GATEWAYGATEWAYThermoformingRef: Figure from S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Typical parts: advertising signs, refrigerator liners, packaging,appliance housings, panels for shower stall.Department of Mechanical Engineering, The Ohio State UniversitySl. #7GATEWAYGATEWAYCastingRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Department of Mechanical Engineering, The Ohio State UniversitySl. #8GATEWAYGATEWAYLess Common Methods• Expansion - expandable polystyrene bead fill mold and bond (steam)• Foaming - liquid chemicals - combine & cure (isocynate polyal) • Spinning- produces plastic fibers- Similar to extrusion• Solid Phase Form- forming plastic below glass temperature- Similar to stamping or forgingDepartment of Mechanical Engineering, The Ohio State UniversitySl. #9GATEWAYGATEWAYMoldingMolding process• Most common plastic “finishing” process• Many molding methods – Transfer Molding– Blow Molding – Compression Molding– Rotational Molding– Reaction Injection Molding– Injection MoldingDepartment of Mechanical Engineering, The Ohio State UniversitySl. #10GATEWAYGATEWAYCompression Molding•Pre-shaped part placed directly into heated mold.•Examples: Dishes, Handles, Electrical Components, Fittings and housingsFigure ref: Process Selection, KG Swift and JD Booker, p. 50.Department of Mechanical Engineering, The Ohio State UniversitySl. #11GATEWAYGATEWAYTransfer MoldingRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Typical parts: electrical and electronic components, rubber and silicone parts.Department of Mechanical Engineering, The Ohio State UniversitySl. #12GATEWAYGATEWAYRotation MoldingRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Typical parts: tanks, trash cans, boat hulls, buckets, housings, toys, carrying cases, and footballs.Department of Mechanical Engineering, The Ohio State UniversitySl. #13GATEWAYGATEWAYReaction Injection MoldingRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Typical parts: automotive bumpers and fenders, thermal insulation for refrigerators and freezers, and stiffeners for structural components.Department of Mechanical Engineering, The Ohio State UniversitySl. #14GATEWAYGATEWAYBlow Molding, Bottles• Hollow plastic parts with relatively thin walls.• Typical parts: Bottles, Bumpers, Bags, Ducting.Figure ref: Process Selection, KG Swift and JD Booker, p.55.Department of Mechanical Engineering, The Ohio State UniversitySl. #15GATEWAYGATEWAYBlow Molding, Plastic BagsRef: Figure from: S. Kalpakjian, Manufacturing Processes for Engineering Materials, Second Ed., Addison Wesley, 1991Department of Mechanical Engineering, The Ohio State UniversitySl. #16GATEWAYGATEWAYInjection Molding•Complex Plastic Parts•Examples: Fittings, Containers, Bottle Tops,


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