New approaches to Materials Education - a course authored by Mike Ashby and David Cebon, Cambridge, UK, 2007 © MFA and DC 2007 Unit 5. Selecting processes: shaping, joining and surface treatment

© MFA and DC 2007 Outline Processes and their attributes Screening by attributes Selecting shape-forming processes Selecting joining processes Selecting surface-treatment processes Exercises More info: “Materials: engineering, science, processing and design”, Chapter 18 and 19 “Materials Selection in Mechanical Design”, Chapters 7 and 8

© MFA and DC 2007 Manufacturing processes Joining Welding Adhesives Fasteners Welding Primary shaping Casting Molding PM methods Injection moulding Secondary shaping Machining Drilling Cutting Machining Surface Treating Painting Polishing Heat treating Painting

© MFA and DC 2007 Each family has attributes that differ. Family Joining Shaping Surfacing Data organisation: the PROCESS TREE Kingdom Process data-table Class Casting Deformation Molding Composite Powder Rapid prototyping Member Compression Rotation Injection RTM Blow Attributes Process records RTM Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general RTM Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general Blow molding Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general Blow molding Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general Injection molding Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general Injection molding Material Shape Size Range Min. section Tolerance Roughness Economic batch Documentation -- specific -- general Difficult !

© MFA and DC 2007 Shape classification Wire drawing, extrusion, rolling, shape rolling: prismatic shapes Casting, molding, powder methods: 3-D shapes Stamping, folding, spinning, deep drawing: sheet shapes Some processes can make only simple shapes, others, complex shapes.

© MFA and DC 2007 Structured data for injection moulding* 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 moulding is then ejected. Injection moulding (Thermoplastics) *Using the CES EduPack Level 2 DB Process characteristics Discrete True Prototyping False Economic Attributes Economic batch size1e e+006 Relative tooling cost high Relative equipment cost high + links to materials Shape Circular PrismTrue Non-circular PrismTrue Solid 3-DTrue Hollow 3-DTrue Physical attributes Mass range kg Roughness µm Section thickness mm Tolerance0.1-1mm Cost modeling Relative cost index Typical uses Injection molding is used ………. Key physical factors in choosing a shaping process (economics always important)

© MFA and DC 2007 Unstructured data for injection moulding* 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. The economics. Capital cost are medium to high; tooling costs are high, making injection moulding economic only for large 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 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. The process. Most small, complex plastic parts you pick up – children’s toys, CD cases, telephones – are injection moulded. 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 moulding is then ejected. Various types of injection moulding machines exist, but the most common in use today is the reciprocating screw machine, shown schematically here. Polymer granules are fed into a spiral press like a heated meat-mincer where they mix and soften to a putty-like goo that can be forced through one or more feed-channels (“sprues”) into the die. *Using the CES EduPack Level 2 DB

© MFA and DC 2007 Finding information with CES Browse SelectSearch Toolbar PrintSearch web File Edit View Select Tools Find what? Which table? SLS Processes RTM Joining Shaping Surface treatment ProcessUniverse Table: ProcessUniverse Subset: Edu Level 2

© MFA and DC 2007 Selection of processes Step 2Screening: eliminate processes that cannot do the job Step 3Ranking: find the processes that do the job most cheaply Step 4Documentation: explore pedigrees of top-ranked candidates Step 1Translation: express design requirements as constraints & objectives Process selection has the same 4 basic steps

© MFA and DC 2007 Shape Circular prismatic Non-circular prismatic Flat sheet etc Physical attributes Mass range kg Tolerance mm Roughness  m Material Ceramic Hybrid Metal Polymer Ferrous Non-ferrous B 1 > B > B 2 Batch size B Selection by series of screening stages Browse SelectSearch 1. Selection data Edu Level 2: Processes - shaping 2. Selection Stages Graph Limit Tree Results X out of 60 pass Process 1 Process 2 Process 3 Process 4 Process 5 ………

© MFA and DC 2007 Spark-plug insulator: translation  Mass 0.05 kg  Section3 - 5 mm  Tolerance < 0.5 mm  Roughness< 100  m  Batch size >2,000,000  Material classAlumina  Shape class3-D, hollow Constraints Free variable Choice of process Body shell Insulator Central electrode Make 2,000,000 insulators from alumina with given  shape  dimensions  tolerance and  surface roughness Design requirements Insulator Translation of design requirements Function

© MFA and DC Economic attributes Physical attributes Mass range Range of sect. thickness kg - Tolerance Roughness Shape mm  m m Hollow, 3 D Economic batch size - Materials Ceramics Alumina Hybrids B-carbide Metals Silicon Polymers W-carbide 2 Spark-plug insulator: screening Body shell Insulator Central electrode Translation Select Level 2: Shaping processes 1  Mass 0.05 kg  Section 3 – 5 mm  Tolerance < 0.5 mm  Roughness < 100  m  Batch size >2,000,000  Material class Alumina  Shape class 3-D, hollow Constraints  e6

© MFA and DC 2007 The selection: two shaping processes Powder pressing and sintering Powder injection molding

© MFA and DC 2007 Data organisation: joining processes Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Gas welding Material Joint geometry Size Range Section thickness Relative cost... Documentation Attributes Adhesives Welding Fasteners Braze Solder Gas Arc e -beam... Class Member Family Kingdom Surface treatment Joining Shaping Processes  Lap  Butt  Sleeve  Scarf  Tee Joint geometry

© MFA and DC 2007 A joining record* Gas Tungsten Arc (TIG) Tungsten inert-gas (TIG) welding, the third of the Big Three (the others are MMA and MIG) is the cleanest and most precise, but also the most expensive. In one regard it is very like MIG welding: an arc is struck between a non-consumable tungsten electrode and the work piece, shielded by inert gas (argon, helium, carbon dioxide) to protect the molten metal from contamination. But, in this case, the tungsten electrode is not consumed because of its extremely high melting temperature. Filler material is supplied separately as wire or rod. TIG welding works well with thin sheet and can be used manually, but is easily automated. Physical Attributes Component size non-restricted Watertight/airtight True DemountableFalse Section thickness 0.7-8mm Economic Attributes Relative tooling cost low Relative equipment cost medium Labor intensitylow Typical uses TIG welding is used ………. *Using the CES EduPack Level 1 DB + links to materials Joint geometry LapTrue Butt True Sleeve True Scarf True Tee True Materials Ferrous metals Key physical factors in choosing a joining process Documentation

© MFA and DC 2007 Data organisation: joining and surface treatment FamilyKingdom Surface treatment Joining Shaping Processes Class Heat treat Paint/print Coat Polish Texture... Member Electroplate Anodize Powder coat Metallize... Attributes Process records Anodize Material Why treatment? Coating thickness Surface hardness Relative cost... Documentation Anodize Material Why treatment? Coating thickness Surface hardness Relative cost... Documentation Anodize Material Why treatment? Coating thickness Surface hardness Relative cost... Documentation Anodize Material Why treatment? Coating thickness Surface hardness Relative cost... Documentation Anodize Material Function of treatment Coating thickness Surface hardness Relative cost... Documentation Anodize Material Function of treatment Coating thickness Surface hardness Relative cost... Documentation  Thermal insulation  Electrical insulation  Color  Texture  Decoration ….  Increased hardness  Wear resistance  Fatigue resistance  Corrosion resistance  Oxidation resistance Function of treatment

© MFA and DC 2007 A surface-treatment record* Induction and flame hardening Take a medium or high carbon steel -- cheap, easily formed and machined -- and flash its surface temperature up into the austenitic phase-region, from which it is rapidly cooled from a gas or liquid jet, giving a martensitic surface layer. The result is a tough body with a hard, wear and fatigue resistant, surface skin. Both processes allow the surface of carbon steels to be hardened with minimum distortion or oxidation. In induction hardening, a high frequency (up to 50kHz) electromagnetic field induces eddy-currents in the surface of the work- piece, locally heating it; the depth of hardening depends on the frequency. In flame hardening, heat is applied instead by high- temperature gas burners, followed, as before, by rapid cooling. Economic Attributes Relative tooling costlow Relative equipment cost medium Labor intensitylow *Using the CES EduPack Level 2 DB + links to materials Key physical factors in choosing a surface treatment Physical Attributes Curved surface coverage Very good Coating thickness300-3e+003µm Processing temperature K Surface hardness Vickers Typical uses Induction hardening is used ….. Function of treatment Fatigue resistance Friction control Wear resistance Hardness Documentation

© MFA and DC 2007 The main points The structure allows easy searching for process data Select first on primary constraints Shaping: material, shape and batch size Joining: material(s) and joint geometry Surface treatment: material and function of treatment Then add secondary constraints as needed. Documentation in CES, and Processes can be organised into a tree structure containing records for structured data and supporting information

© MFA and DC 2007 Pause for demo

© MFA and DC 2007 Exercises: Browsing processes 5.1 Find, by browsing, the Level 2 record for the shaping process Resin transfer molding (RTM) in Shaping: Composite forming. What products, typically, is it able to make? 5.2 Find the Level 2 record for shaping process Abrasive jet machining and cutting in Shaping: Machining: non-conventional machining. Can it be used to cut glass? 5.3 Find the Level 2 record for the joining process Friction-stir welding in Joining: Mechanical welding. How does the process work? 5.4 Find the Level 2 record for the surface coating process Metal flame spraying in Surface treatment: Surface coating. What are its principal uses?

© MFA and DC 2007 Exercises: Searching for processes 5.5 Find, by searching, the record for the rapid prototyping process with the trade name SLS. What classes of material can it handle? 5.7 Find, by searching, the record for Vitreous enameling. What Functions can it perform? 5.6 Find, by searching, the record for Flexible adhesives. Which polymers are used for flexible adhesives?

© MFA and DC 2007 Exercise : Selecting shaping processes 5.8 A process is required to mold ABS components with a solid 3-D shape in large numbers: it should be economic at a batch size of 1,000,000 or more. Use the CES Level 2 Shaping data-table to find possible candidates.  Material: ABS (TREE stage)  Process: Molding (second TREE stage)  Shape: 3-D solid (LIMIT stage) and Economic batch size > 10 6 (LIMIT stage) Results: Compression molding Injection molding, thermoplastics

© MFA and DC 2007 Exercise : Cutting CFRP sheet 5.9 A process is required to cut flat 4mm CFRP sheet for the face-sheets of a light-weight sandwich panel. Using the Level 2 Shaping data-table to select it. The requirements are  Material: CFRP (TREE stage)  Shape: flat sheet (LIMIT stage)  Section thickness: 4mm (LIMIT stage)  Process characteristics: Cutting (LIMIT stage) Results: Abrasive jet machining and cutting Band sawing Laser cutting Water-jet cutting

© MFA and DC 2007 Exercise: Joining metal sheet Gillette “Sensor 3” razor A process is required to join 0.6 mm steel blades onto aluminum sheet carriers to form a lap joint. Use the Level 2 Joining data-table to find them. The requirements are  Materials to be joined: metals  Joint geometry: lap joint  Section thickness: 0.6 mm  Demountable: No (X) All done with a LIMIT stage Results: Brazing Power beam (laser, electron beam) Resistance welding Rivets and staples Ultrasonic welding Blades The reality: Laser spot welds

© MFA and DC 2007 Exercise: Surface treatment of gears Emerson Transmission Corp Enhancing performance of gears A process is required to improve the wear resistance and fatigue resistance of steel gears. The requirements are  Materials: steel  Purpose of treatment: wear resistance fatigue resistance  Curved surface coverage: very good Results: Carburizing and carbo-nitriding Nitriding Induction hardening and flame hardening

© MFA and DC 2007 End of Unit 5