Green sand mould


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Green sand mould

  1. 1. Green Sand Mould By Payal Saxena 12 MEU 099
  2. 2. Introduction What is a mould? A mould is a hollowed-out block that is filled with a liquid like plastic, glass, metal, or ceramic raw materials .The liquid hardens or sets inside the mold, adopting its shape. A mold is the counterpart to a cast.
  3. 3. Classification of moulding sands According to their use in the foundry, moulding sands are classified into following categories: 1. Green sand: The term "green sand" is known principally because of the moisture content within the sand. The sand undergoes a "mulling" process in which various clay and chemical additives that act as binders are blended with the sand, which results in a compound which is suitable for the sand molding process. Cont..
  4. 4. It is sand used in the wet condition for making the mould. It is mixture of silica sand with 15-25 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.
  5. 5. 2. Dry sand: Dry sand is the green sand that has been dried or baked after preparing the mould. Drying sand gives strength to the mould so that it can be used for larger castings.
  6. 6. 3. Loam sand: 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.
  7. 7. 4. Parting sand: This sand is used during making of the mould to ensure that green sand does not stick to the pattern and the cope and drag parts can be easily separated for removing the pattern without causing any damage to the mould.
  8. 8. 5. Facing sand: Facing sand is the sand which covers the pattern all around it. The remaining box is filled with ordinary floor sand. Facing sand forms the face of the mould and comes in direct contact with the molten metal when it is poured.
  9. 9. 6. Backing sand: Backing sand is the bulk of the sand used to back up the facing sand and to fill up the volume of the flask. The main purpose for the use of backing sand is to reduce the cost of moulding.
  10. 10. 7. System sand: This is the sand used in mechanized foundries for filling the entire flask. Sand, cleaned and reactivated by the addition of water and binders is used to fill the flask. Because of the absence of any fresh sand, system sand must have more strength, permeability and refractoriness compared to backing sand.
  11. 11. 8. Core sand: Core sand is the sand used for making cores. This is silica sand mixed with core oil. That is why it is also called oil sand.
  12. 12. Green sand Moulding process Green sand molding is more wide develop than any other process. Green sand molding is replacing many of the more expensive moulding methods as sand control is being applied.
  13. 13. Why we use Green sand Molding process ? -Reasonable cost. -Environmental friendly. -High productivity (Economical). -Easily adaptable to manual , semi-auto and automatic moulding Machines.
  14. 14. Properties 1 Green sand for moulding must fulfill and pack tightly round the pattern under pressure. It must be “Flowable”. 2 Green sand for moulding should be able of being deformed slightly without cracking, so that the pattern can be withdrawn. In other words, it must exhibit “Plastic” behaviour.
  15. 15. 3 Green sand must have sufficient strength to strip from the patterns and support its own weight without deforming, and withstand the pressure of molten metal when the mould is cast. It must therefore get “Green Strength”. 4 Green sand should be “Permeable” , so gases and steam can escape from the mould at the beginning of pouring to avoid any kind of defects.
  16. 16. 5 Green sand must get “Dry Strength” to prevent erosion by liquid metal during pouring as the mould surface dries out. 6 Green sand must guarantee a good “Refractoriness” to withstand the high temperature involved without melting or fusing with the metal.
  17. 17. Green sand components Foundry sand Bentonite Additives Water Dead Clay
  18. 18. Bentonite is one of the most important component of green sand. RULE OF BENTONITE = THE SAND BINDER
  19. 19. Advantages These molds are relatively inexpensive to produce , since material is readily available.  Complex patterns can be accommodated in the mold design, at affordable costs.  Easily adapts to automated production methods.