Basic Manufacturing - Casting Process PDF

ME204 BASIC MANUFACTURING PROCESS (4-0-0) 4 Dr. RAMESH M R Professor Department of Mechanical Engineering 1 Classification of Manufacturing process Examples Examples Examples Examples Examp...

ME204 BASIC MANUFACTURING PROCESS (4-0-0) 4 Dr. RAMESH M R Professor Department of Mechanical Engineering 1 Classification of Manufacturing process Examples Examples Examples Examples Examples Steps involved in casting i. Pattern making ii. Preparation of moulds iii.Core Making iv.Melting and pouring the molten material v. Solidification and further cooling to room temperature vi.Cleaning, Inspection, and defects if any remove Steps involved in casting Steps involved in casting Steps involved in casting Steps involved in casting Steps involved in casting Steps involved in casting Steps involved in casting Steps involved in casting Terms Terms Selection of Manufacturing Process Selection of Manufacturing Process Cast Products Advantages of casting Complex shapes, internal cavities and hollow sections produced Quick process and Suitable for mass production No limit on size, shape and weight of the product, Very large parts produced economically High strength and rigid parts obtained as casting exhibit uniform properties in all the direction Limitations Dimensional accuracy and surface finish does not meet exactly Presence of defects in cast parts Not economical for small parts Properties are infirier when compare to formed parts Labor intensive PATTERNS MATERIALS USED FOR PATERN ▪ Wood ▪ Metal ▪ Plastics ▪ Gypsum ▪ Wax  Selection of pattern material Size and shape of the casting Dimensional accuracy of casting Number of castings required Casting process to be used 18  Properties of pattern material Machinability Wear resistance Strength Dimensional stable Resistance to variation in temp. & humidity Repairability 19  Wood Low cost Light in weight Easily available Ease of fabricating to many shapes Absorbs moisture and dimensions will change Lower life Suitable for production of small quantity castings 20  Metal Metals used → Al, CI, Brass, etc. Used for mass production High strength More life compared to wood patterns Suitable for production of large castings 21  Plastics Wax Low weight Used for prototype castings Easier formability Withdrawal is easy Do not absorb moisture Disposable patterns Good corrosion resistance 22 TYPES OF PATTERNS Single Piece Pattern Made of wood and inexpensive Used for casting simple shape Low quantity production TYPES OF PATTERNS Split Pattern Two/Three piece pattern Used for casting intricate shapes Easy removal of pattern from the mould TYPES OF PATTERNS Loose Piece Pattern Patern with complex shapes , when it is difficult to withdraw from the mould, two or more loose pieces are assembled together to form a single patern TYPES OF PATTERNS Match Plate Pattern Both halves of pattern mounted on single plate Match plate → metal/wood; Pattern → metal Mass production of small castings with accuracy TYPES OF PATTERNS Gated Pattern Made of metal & produce multi-cavity in one mould Gates and runners integral with pattern Productivity is more TYPES OF PATTERNS Sweep Pattern Sweep the desired shape in the mould Produce symmetrical shaped large size castings E.g. Bell shape/Cylindrical shape TYPES OF PATTERNS Skeleton Pattern Skeleton → made of strips of wood → forms the outline of desired shape of casting Skeleton type → depends on geometry of job Large size castings in small quantities produced  Pattern allowances Shrinkage allowance Machining allowance Draft allowance Shaking allowance Distortion allowance Pattern allowances depends on: ✓ Design of a product ✓ Type of mould material ✓ Shrinkage characteristic of material to be cast 28 Shrinkage Allowances  Machining Allowance Provided to compensate for rough surface of the cast product when taken out of the mould cavity Machining allowance → excess dimension of casting to be machined/finished Machining allowance depends on: ✓ Size and shape of a casting ✓ Type of cast material ✓ Degree of finish required  Draft/ Taper Allowances Taper allowance → taper provided on the vertical faces of pattern Provided to facilitate easy withdrawal of pattern from the mould Taper allowance depends on:Size and shape of a casting, Type of moulding, Intricacy of job/product Draft → typical range: 1° to 3°  Distortion Allowance Provided to compensate for distortion of weaker sections of casting when just solidified Equal amount of distortion has to be given to a pattern in a direction opposite to that of likely distortion direction Rapping and Shake Allowance Provided to compensate for slight enlargement of mould cavity when pattern is rapped all around vertical faces before withdrawal Slight enlargement results in increase in size of final casting Dimension of original pattern has to be reduced → -ve allowance has to be provided to the pattern → Shaking allowance  Moulding Sand Sand used to make moulds and strongly bonded together in flask Moulding sand = Base sand + Binder + water + Additives Base Sand Base Sand Properties or Requirements of Base Sand Properties or Requirements of Base Sand Binders Additives Additives Types of moulding sand Green sand Sand contains moisture → silica sand + water (6-8%) + clay (18- 30%) Used for making small to medium sized castings Rate of production of cast product is high Types of moulding sand Dry sand Dry sand → completely dried green sand Higher strength than green sand mould Used for making medium to large sized castings Provides better dimensional accuracy and surface finish to casting Disadvantage → More expensive and likely to be distorted Types of moulding sand Loam sand Loam sand → silica sand + water + clay (50%) Completely dried before casting process Used for making heavy castings → bells; large cylinders; chemical plant pans Disadvantage → time consuming Types of moulding sand Facing sand Facing sand → silica sand + clay + coal dust Used next to the pattern and in contact with molten metal Coal dust prevents the molten metal from entering the sand Produces clean and smoother casting surface Types of moulding sand Parting sand Parting sand → Fine dry silica sand (Non-sticky) Sprinkled on the pattern and parting surfaces of mould halves Easy withdrawal of pattern and separation of cope and drag at parting surface Core sand Core sand → Silica sand + Oil Used for making the cores Types of Sand Moulds GREEN SAND MOULD DRY SAND MOULD Types of Sand Moulds SKIN DRIED MOULD NO-BAKE SAND MOULD METHODS OF SAND MOULDING 1. Bench Moulding 2. Floor Moulding 3. Pit Moulding 4. Machine Moulding Pit Moulding Machine Moulding JOLT SQUEEZE MACHINE Machine Moulding SAND SLINGER SPECIAL MOULDING PROCESS SHELL MOULDING SHELL MOULDING SHELL MOULDING CARBON DIOXIDE MOULDING CARBON DIOXIDE MOULDING INVESTMENT MOULDING INVESTMENT MOULDING INVESTMENT MOULDING INVESTMENT MOULDING CONTINUOUS CASTING CONTINUOUS CASTING CENTRIFUGAL CASTING TRUE CENTRIFUGAL CASTING SEMI CENTRIFUGAL CASTING CENTRIFUGING CASTING GRAVITY DIE CASTING GRAVITY DIE CASTING PRESSURE DIE CASTING HOT CHAMBER PRESSURE DIE CASTING HOT CHAMBER PRESSURE DIE CASTING COLD CHAMBER PRESSURE DIE CASTING COLD CHAMBER PRESSURE DIE CASTING SQUEEZE CASTING SQUEEZE CASTING SLUSH CASTING SLUSH CASTING Green Sand Flask-less moulding Green Sand Flask-less moulding Plaster of Paris Flask-less moulding GATING SYSTEM REQUIREMENTS/ PURPOSE OF GATING SYSTEM  TYPES OF GATES TOP GATE  TYPES OF GATES TOP GATE- Advantages  TYPES OF GATES BOTTOM GATE  TYPES OF GATES BOTTOM GATE-examples  TYPES OF GATES BOTTOM GATE  TYPES OF GATES PARTING GATES RISERING SYSTEM REQUIREMENTS OF RISERING SYSTEM  TYPES OF RISERS TOP or OPEN RISER  TYPES OF RISERS BLIND or INTERNAL RISER CORES CORES- Classification based on material CORES- BINDERS CORES- BINDERS CORES- Classification based on position and their use HORIZONTAL CORES CORES- Classification based on position and their use VERTICAL CORES CORES- Classification based on position and their use BALANCED CORES CORES- Classification based on position and their use DROP CORES CORES- Classification based on position and their use KISS CORES CORES- Classification based on position and their use RAM-UP CORES  CASTING DEFECTS SHRINKAGE DEFECTS  CASTING DEFECTS POROSITY DEFECTS  CASTING DEFECTS MISRUN DEFECTS  CASTING DEFECTS PENETRATION DEFECTS  CASTING DEFECTS MOULD SHIFT  CASTING DEFECTS COLD SHUT DEFECTS  CASTING DEFECTS HOT TEARS DEFECTS  SOLIDIFICATION SOLIDIFICATION OF PURE METAL  SOLIDIFICATION MECHANISM OF SOLIDIFICATION 1. Nucleation-Formation of stable nuclei in metal 2. Grain growth-Nuclei grow to form crystals resulting in grain structure  SOLIDIFICATION Forms of Nucleation a. HOMOGENEOUS NUCLEATION  SOLIDIFICATION Forms of Nucleation B. HETEROGENEOUS NUCLEATION SOLIDIFICATION OF ALLOYS SOLIDIFICATION  SOLIDIFICATION CAST METAL STRUCTURE PROGRESSIVE AND DIRECTIONAL SOLIDIFICATION MELTING FURNACES-CLASSIFICATION MELTING FURNACES-CLASSIFICATION CUPOLA FURNACE CUPOLA FURNACE CUPOLA FURNACE GAS FIRED/OIL FIRED PIT FURNACES GAS FIRED/OIL FIRED PIT FURNACES COKE FIRED FURNACES ELECTRIC RESISTANCE FURNACES ELECTRIC RESISTANCE FURNACES INDUCTION MELTING FURNACES DIRECT ARC ELECTRIC FURNACES DIRECT ARC ELECTRIC FURNACES INDIRECT ARC ELECTRIC FURNACES INDIRECT ARC ELECTRIC FURNACES CASTING DESIGN CONSIDERATION DESIGN FOR MINIMUM CASTING STRESSES DESIGN FOR MINIMUM CASTING STRESSES DESIGN FOR MINIMUM CASTING STRESSES DESIGN FOR MINIMUM CASTING STRESSES DESIGN FOR MINIMUM CASTING STRESSES DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR DIRECTIONAL SOLIDIFICATION DESIGN FOR METAL FLOW CAST WELD DESIGN DESIGN FOR MINIMUM COSTING DESIGN FOR MINIMUM COSTING DESIGN FOR MINIMUM COSTING DESIGN FOR MINIMUM COSTING FUNCTIONAL DESIGN Thank You 167