1 Unstructured data for injection molding* Finding information with - PDF document

Process Selection Manufacturing processes � Processes and their attributes � The text book classified manufacturing processes into three broad categories � Screening by attributes Shaping � � Selecting shape-forming processes Joining � � Selecting joining processes Surface treatment � � Selecting surface-treatment processes � Each has many sub-categories, which may then be further subdivided � Case study + demos into individual processes � Many processes are used in combination with others Manufacturing process selection involves identifying which will � work best for a particular application More info: “ Materials Selection in Mechanical Design ”, Chapters 7 and 8 ME 474-674 Winter 2008 ME 474-674 Winter 2008 Slides 7 -1 Slides 7 -2 Examples of processes Data organization: the PROCESS TREE Difficult ! Attributes Kingdom Family Class Member RTM RTM Blow molding Blow molding Material Casting Material Compression Injection molding Material Injection molding Shaping Joining Shape Material Shaping Shape Deformation Material Rotation Shape Material Shape Size Range Size Range Shape Process Molding Size Range Shape Injection Min. section Size Range Shaping Min. section data-table Size Range Min. section Size Range Composite Tolerance Min. section RTM Tolerance Blow moulding Min. section Sand casting Tolerance Min. section Roughness Tolerance Powder Roughness Surfacing Blow Tolerance Roughness Tolerance Economic batch Roughness Economic batch Roughness Rapid prototyping Economic batch Roughness Economic batch Documentation Documentation Economic batch Documentation Economic batch -- specific Documentation -- specific Documentation -- specific Documentation Each family has -- general -- specific -- general -- specific Surface -- general -- specific Joining attributes that differ. -- general -- general treating -- general Process records Fusion welding Induction hardening ME 474-674 Winter 2008 ME 474-674 Winter 2008 Slides 7 -3 Slides 7 -4 Shape classification Structured data for injection molding* Injection molding (Thermoplastics) Some processes can make only simple shapes, others, complex shapes. � INJECTION MOULDING of thermoplastics is the equivalent of pressure die casting of metals. Molten polymer is injected under high pressure into a cold steel mould. The polymer solidifies under pressure and the molding is then ejected. Shape Economic Attributes Circular Prism True Economic batch size 1e+004 - 1e+006 Non-circular Prism True Relative tooling cost high Solid 3-D True Relative equipment cost high Hollow 3-D True Physical attributes Cost modeling Mass range 0.01- 25 kg fx fx Relative cost index Roughness 0.2 - 1.6 µm Section thickness 0.4 - 6.3 mm Tolerance 0.1 - 1 mm Process characteristics + links to materials Discrete True Prototyping False Typical uses Key physical factors in choosing � Wire drawing, extrusion, � Stamping, folding, � Casting, molding, Injection molding is used ………. rolling, shape rolling: spinning, deep drawing: powder methods: a shaping process prismatic shapes sheet shapes 3-D shapes ( economics always important ) ME 474-674 Winter 2008 Slides 7 -5 ME 474-674 Winter 2008 Slides 7 -6 *Using the CES EduPack Level 2 DB 1

Unstructured data for injection molding* Finding information with CES File Edit View Select Tools The process. Most small, complex plastic parts you pick up – children’s toys, CD cases, telephones – are injection moulded. Mould Granular Polymer Injection moulding of thermoplastics is the equivalent of pressure Toolbar Browse Select Search Print Search web die casting of metals. Molten polymer is injected under high Nozzle pressure into a cold steel mould. The polymer solidifies under Cylinder pressure and the moulding is then ejected. Various types of injection moulding machines exist, but the most common in use today is the reciprocating screw machine, shown Table: ProcessUniverse Table: ProcessUniverse schematically here. Polymer granules are fed into a spiral press Find what? SLS RTM like a heated meat-mincer where they mix and soften to a putty- Heater Screw Which table? Processes like goo that can be forced through one or more feed-channels Subset: Edu Level 2 Subset: Edu Level 2 (“sprues”) into the die. No.8-CMYK-5/01 ProcessUniverse � Design guidelines. Injection moulding is the best way to mass-produce small, precise, plastic parts with complex shapes. The surface finish is good; texture and pattern can be moulded in, and fine detail reproduces well. The only finishing operation + is the removal of the sprue. Joining � The economics . Capital cost are medium to high; tooling costs are high, making injection moulding economic only for large + Shaping batch-sizes (typically 5000 to 1 million). Production rate can be high particularly for small mouldings. Multi-cavity moulds are often used. The process is used almost exclusively for large volume production. Prototype mouldings can be made using + Surface treatment cheaper single cavity moulds of cheaper materials. Quality can be high but may be traded off against production rate. Process may also be used with thermosets and rubbers. � Typical uses . The applications, of great variety, include: housings, containers, covers, knobs, tool handles, plumbing fittings, lenses, etc. � The environment. Thermoplastic sprues can be recycled. Extraction may be required for volatile fumes. Significant dust exposures may occur in the formulation of the resins. Thermostatic controller malfunctions can be extremely hazardous. *Using the CES EduPack Level 2 DB ME 474-674 Winter 2008 ME 474-674 Winter 2008 Slides 7 -7 Slides 7 -8 Process Selection Selection by series of screening stages Ceramic Browse Select Search � Like materials selection, process selection also has the same 4 basic steps Hybrid Ferrous Material Metal � Once a material is selected, it becomes one of the constraints in process 1. Selection data Non-ferrous Polymer selection Edu Level 2: Processes - shaping Edu Level 2: Processes - shaping Shape Step 1 Translation: express design requirements as constraints & objectives 2. Selection Stages Circular prismatic Non-circular prismatic Graph Limit Tree Step 2 Screening: eliminate processes that cannot do the job Flat sheet etc Physical attributes Step 3 Ranking: find the processes that do the job most cheaply 0.2 0.3 Mass range kg Results Tolerance mm 0.5 Step 4 Supporting information: explore pedigrees of top-ranked candidates X out of 60 pass Roughness μ m 100 Process 1 B 1 > B > B 2 Process 2 Batch size B Process 3 Because there are thousands of variants of processes, supporting information plays a particularly important role Process 4 Process 5 ……….. ME 474-674 Winter 2008 ME 474-674 Winter 2008 Slides 7 -9 Slides 7 -10 Example of the Translation step Spark-plug insulator: translation Example : Casing for a capacitance pressure sensor for use as a traffic sensor Insulator Translation of design requirements The sensor lies across the road, covered by a rubber mat. Vehicle pressure deflects Body shell Insulator top face, changing capacitance between top Function face and copper conducting strip. � Material class Alumina Central Constraints electrode � Shape class 3-D, hollow � Mass 0.05 kg Design requirements � Section 3 - 5 mm Function Casing for road-pressure sensor Make 2,000,000 insulators � Tolerance < 0.5 mm from alumina with given < 100 μ m Material: Al alloy � Roughness Constraints Shape: non-circular prismatic � shape � Batch size >2,000,000 Minimum section: 2 ± 0.025 mm � dimensions Objectives Minimize cost � tolerance and Free variable Choice of process � surface roughness Free variable Choice of process ME 474-674 Winter 2008 Slides 7 -11 ME 474-674 Winter 2008 Slides 7 -12 2