1. ME1008: MANUFACTURING TECHNOLOGY
UNIT I
CASTING

2. INTRODUCTION TO CASTING
Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify.
It is most ancient process of manufacturing metallic components.

3. INTRODUCTION TO CASTING

4. Following steps involved in the casting process Melting the metal.
Pouring it into a previously made mould or cavity.
Cavity which conforms the shape of the desired component which we obtained.
Allowing the molted metal to cool and solidify in the mould.
Removing the solidified component from the mould.
Cleaning it for further treatment if necessary.
Note: “the solidified piece of metal which is taken out of mould is casting”

5. APPLICATIONS Engine and cylinder block. Pistons, piston rings
Wheels and housing of steam and hydraulic turbines.
Turbine and jet engine blades, etc.

6. CLASSIFICATION OF CASTING PROCESS
Expandable mould casting, one casting mould with less accuracy, eg: sand casting.
Permanent mould casting, mould will used repeatedly for number of casting be achieved, it is used for mass production and it with high accuracey.
Semi-permanent casting, high refractory materials is used, so it is not suitable for permanent moulding.

8. PATTERNS
In casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process.
It is not exact replica of the exact desired casting.
It is slightly larger than the desired casting, because of allowances.

9. TYPES OF PATTERN Single piece pattern Split piece pattern
Loose piece, Gated, match pattern
Sweep pattern
Cope and drag pattern
Skeleton pattern
Shell and follow board pattern.

10. TYPES OF PATTERN contd….
Single piece pattern: It is simplest of all pattern is made in one piece. It is suited for limited process only.
Spilt piece pattern: It is used for intricate casting for usual shapes. These two patterns are joined together with the help of dowel pins.

11. TYPES OF PATTERN contd….
Loose piece pattern: Some patterns usually single piece are made to have loose pieces in order to enable their easy with drawn from the mould.

12. TYPES OF PATTERN contd….
Gate pattern
Match plate pattern

13. TYPES OF PATTERN contd….
Sweep pattern
Cope and drag

14. TYPES OF PATTERN contd….
Skeleton pattern
Follow
pattern

15. TYPES OF PATTERN contd….
Shell pattern

16. REQUIREMENTS OF A GOOD PATTERN
Secure the desired shape and size of the casting.
Cheap and readily repairable.
Simple in design for ease of manufacture.
Light in mass and convenient to handle.
Have high strength and long life in order to make as many moulds as required.
Retain its dimensions and rigidity during the definite service life.
Its surface should be smooth and wear resistant.
Able to withstand rough handling.

17. DESIGN CONSIDERATION IN PATTERNS
1. Proper allowance should be provided. 2. The parting line should be carefully selected. 3. Proper material should always be selected. 4. The wall thickness and sections should kept as uniform as possible. Abrupt changes should invariably be avoided. 5. The use of offset pairing, instead of cores, should be encouraged to as great extent as it is possible. Abrupt changes should invariably be avoided.   

18. PATTERN LAYOUT
Pattern making consists of two different stages to prepare a layout and to shape the different parts. Layout consists of the following steps: a. Initially study the drawing pattern and select a wood that can suitably accommodate two views. b. Take on surface of the wood as base and plane the adjacent surface. c. Take a folding rule and measure the dimensions as per the drawing. d. Prepare the layout by using various measuring and marking tools locating position of core prints and surface to be machined.

19. PATTERN MATERIALS Wood: Piece and short run production
Metal: Large scale and mass production
Cement, Plastics for example epoxy resin: Batch production.

20. ALLOWANCE Shrinkage allowance Machining allowance
Pattern draft or tapper
Corners and fillets
Rapping or shake allowance
Distortion allowance

21. MOULDING SAND Molding sand is also known as foundry sand.
Sand with moistened and compressed to pack well and hold its shape.
It is used in the process of sand casting.
Green sand is an aggregate of sand, bentonite clay, pulverized coal and water.
Main purpose of this sand to make mould cavity for casting process.

22. MOULDING SAND contd… Green sand:
It is sand used in the wet condition for making the mould. It is mixture of silica sand with per cent clay and 6-8 per cent water
Green sand moulds are not dried and metal is poured in them in the wet condition
Being damp the sand can be easily worked with hand to give it any desired shape
This sand is used for producing small to medium sized moulds which are not very complex

23. MOULDING SAND contd… Loam sanding:
Loam sand is sand containing up to 50 % clay which has been worked to the consistency of builder mortar.
This sand is used for loam sand moulds for making very heavy castings usually with the help of sweeps and skeleton patterns.

24. MOULDING SAND contd…
Dry sand: If we dry the green sand mentioned above, then we get dry sand. the physical composition remains same, except for water content. Facing sand: This sand comes in contact with direct contact of molten metal hence it is subjected to severest conditions. the basic composition is silica sand and clay.

25. GATING AND RISERING
The assembly of channels which facilitates the molten metal to enter into the mold cavity is called the gating system.
Gating also called as sprue.
Goals of Gating System:
The goals for the gating system are:
To minimize turbulence to avoid trapping gasses into the mold
To get enough metal into the mold cavity before the metal starts to solidify
To avoid shrinkage
Establish the best possible temperature gradient in the solidifying casting so that the shrinkage if occurs must be in the gating system not in the required cast part.
Incorporates a system for trapping the non-metallic inclusions

26. CORE
A core is a device used in casting and molding processes to produce internal cavities and reentrant angles.
The core is normally a disposable item that is destroyed to get it out of the piece.
They are most commonly used in sand casting, and also used in injection molding method.

27. SHELL MOULD CASTING
Shell mold casting is a metal casting process similar to sand casting.
Molten metal is poured in mold cavity.
In shell mold casting, the mold is a thin- walled shell created from applying a sand- resin mixture around a pattern.

29. SHELL MOULD CASTING contd….
Metal piece pattern is used, so it reused to make more number of mould.
It allows the higher production rate.
Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly cast iron, carbon steel, alloy steel, stainless steel, aluminum alloys, and copper alloys used.

30. SHELL MOULD CASTING contd….
The shell mold casting process consists of the following steps:
Pattern creation: A two-piece metal pattern is created in the shape of the desired part, typically from iron or steel.
Other materials such as aluminum for low volume production or graphite for casting reactive materials.

31. SHELL MOULD CASTING contd….
Mold creation - First pattern is heated to °C ( °F) and coated with a lubricant to facilitate removal.
Next, the heated pattern is clamped to a dump box contains a mixture of sand and a resin binder.
The dump box is inverted, allowing this sand-resin mixture to coat the pattern.
The heated pattern partially cures the mixture, which now forms a shell around the pattern.
Each pattern half and surrounding shell is cured to completion in an oven and then the shell is ejected from the pattern.

32. SHELL MOULD CASTING contd….
Mold assembly - The two shell halves are joined together and securely clamped to form the complete shell mold.
If any cores are required they are inserted prior to closing the mold. The shell mold is then placed into a flask and supported by a backing material.

33. SHELL MOULD CASTING contd….
Pouring - The mold is securely clamped together while the molten metal is poured from a ladle into the gating system and fills the mold cavity.
Cooling - After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting.

34. SHELL MOULD CASTING contd….
Casting removal - After the molten metal has cooled, the mold can be broken and the casting removed.
Trimming and cleaning processes are required to remove any excess metal and sand from the feed system.

35. INVESTMENT CASTING
Investment casting is an industrial process based on and also called lost-wax casting.
The first step in investment casting is to manufacture the wax pattern for the process. 

36. INVESTMENT CASTING contd….

37. INVESTMENT CASTING contd….

38. INVESTMENT CASTING contd….

39. INVESTMENT CASTING contd….

40. INVESTMENT CASTING contd….

41. INVESTMENT CASTING contd….

42. CENTRIFUGAL CASTING

43. CENTRIFUGAL CASTING
In this process molten metal is poured into a spinning die.
The die can be spinning either on a vertical or horizontal axis depending on the configuration of the desired part.
Ring and cylinder types cast vertical centrifugal process.
Tubular shapes are made with the horizontal centrifugal process.

44. CENTRIFUGAL CASTING contd….
Permanent mold is rotated continuously about its axis at high speeds (300 to 3000 rpm) as the molten metal is poured.
The molten metal is centrifugally thrown towards the inside mold wall, where it solidifies after cooling. 

45. CENTRIFUGAL CASTING contd….
Castings can be made in almost any length, thickness and diameter.
Different wall thicknesses can be produced from the same size mold.
Eliminates the need for cores.
Resistant to atmospheric corrosion, a typical situation with pipes.
Mechanical properties of centrifugal castings are excellent.
Only cylindrical shapes can be produced with this process.

46. CENTRIFUGAL CASTING contd….
Features of centrifugal casting:
Castings can be made in almost any length, thickness and diameter.
Different wall thicknesses can be produced from the same size mold.
Eliminates the need for cores.
Resistant to atmospheric corrosion, a typical situation with pipes.
Mechanical properties of centrifugal castings are excellent.
Only cylindrical shapes can be produced with this process.

47. DEFECTS IN CASTING Open Blows and Blow Holes Pin Hole Porosity
Entrapped Air and other gases
Cracked Casting
Bent or Twisted Casting
Dropped Mould
Fusion
Swell
Run out
Mismatch
Mis-run and Cold Shut