Common Shape Casting Processes Basic Casting Terminology Pattern and Cores Sand Casting Sand Casting Sand Casting Sand Casting Sand Casting Patterns Patterns may be made from a variety of materials ID: 1019135
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1. Shape Casting ProcessesCasting Processes
2. Common Shape Casting Processes
3. Basic Casting Terminology
4. Pattern and Cores
5. Sand Casting
6. Sand Casting
7. Sand Casting
8. Sand Casting
9. Sand Casting PatternsPatterns may be made from a variety of materials:WoodMetalHard PolymersEPS (Styrofoam)
10. Types of Sand Casting PatternsOne-Piece
11. Types of Sand Casting PatternsOne-Piece (Using a Follow Board)
12. Types of Sand Casting PatternsSplit Pattern
13. Types of Sand Casting PatternsMatch-Plate
14. Types of Sand Casting PatternsCope-and-Drag Split Patterns
15. Types of Sand Casting PatternsLoose Piece Pattern
16. Types of SandsSands can be comprised of: ordinary silica (SiO2), zircon, olivine, or chromite and may be compounded with additives to meet four requirements:RefractorinessCohesivenessPermeabilityCollapsibility
17. Green SandContains bonding agents and waterTypical “green sand” is:88% silica9% clay3% water
18. MullersContinuous Batch
19. Sand ParametersGrain Size – measured by sifting sand through sievesMoisture Content – measured with moisture meterClay Content – measured by weighing a sample of sand before / after washingPermeability – AFS permeability number measured using “standard rammed sample”(Green) Compressive Strength – measure of mold strength before pouringHardness – resistance of packed sand to penetration
20. Permeability Tester
21. Sand Hardness
22. Desirable Properties of Sand-Based Molding MaterialsInexpensive in bulk quantitiesRetains properties through transportation and storageUniformly fills flask or containerCan be compacted or set by simple methodsSufficient elasticity to remain undamaged during pattern removalCan withstand high temperatures and maintain dimensional stability until solidificationSufficiently permeable to allow gases to escapeSufficiently dense to prevent metal penetrationSufficiently cohesive to prevent wash-out of mold material into the pour streamChemically inert to the metal being castCan yield to solidification and thermal shrinkage, preventing hot tears and cracksRecyclable
23. Sand Casting DefectsSand Expansion Defects – occur on large, flat portions of castings where large expansion must occur in one direction. Can be alleviated by:Careful selection of sand geometry (some sands “slide” past each other more easilyUse of low-expansion sands (zircon or olivine)Additional clay added to absorb expansionVolatile additives in sand mixture (burn off and create space)Voids or Blows – due to trapped gas and low sand permeabilityPenetration – overly fluid pour traps sand particles in meltHot tears or cracks – high solidification shrinkage resisted by mold with poor collapsibility
24. Sand-Cast Parts
25. Green Sand Casting Summary
26. SodiumSilicate-CO2 MoldingSand has 3%-6% sodium silicate (“water glass”) added as binder.Mixed in a standard mullerAddition of high-concentration CO2 gas causes binder to harden in a matter of seconds:Very strong mold, but poor collapsibility
27. No-Bake / Air Set / Chemically Bonded SandsA variety of other binders that cure at room temperature can be used to hold sand togetherProvide greater mold strength than green sand.Added cost and time.
28. Shell CastingIndividual grains of sand are pre-coated with a phenolic resin and heat-sensitive liquid catalist.Sand spread on top of a heated (450 – 600 deg. F) metal pattern.Heat bonds the material near the pattern. Excess sand is poured off.Thin shell is removed and placed in an oven for further curing.
29. Shell Casting
30.
31. Shell-Mold Casting Summary
32. V-Process (Vacuum Molding)
33. Cores and Core-Making
34. Cores to Make Holes
35. Dump-type Core Box (Dry Sand Cores)
36. Chaplets
37. Three-Segment Flasks