Facing Sand

A sand casting facing composition comprises a dry mixture of about 77% fine sand, 5% binder, 6% green system sand and 12% burned system sand. The fine sand is mulled with 5.8% wt/wt oil per total dry mixture and catalyst at about 0.5% wt/wt. Preferably, fine sand and binder are mulled with oil, catalyst, green system sand and screened burned system. The mulled mixture is rested, mulled again and rested again before use as facing sand for achieving accurate reproduction of the pattern's fine detail. A method of preparing the mold and preserving fine detail comprises riddling the pattern with a thin layer of the facing sand composition, compacting, riddling with dry system sand and riddling with system sand before compacting about the periphery of the pattern. Final layers of system sand are applied and compacted over the entire pattern.

 

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Types of Molding sand in Casting Process

Types of molding sand:

 

  Green sand:

                                 Natural sand with moisture

 Dry sand:

                                Not suitable for large castings

Facing sand:

This sand is used directly next to the surface of the pattern and comes into contact with the molten metal when the mould is poured.

As a result, it is subjected to the severest conditions and must possess, therefore, high strength and refractoriness. This sand also provides a smoother casting surface and should be of fine texture. It is made of silica sand and clay, and some additives without the addition of used sand.

Facing sand is always used to make dry sand moulds while system sand is frequently used for green sand molding.

Parting sand:

This sand is used to prevent adhering of two halves of mould surfaces in each molding box when they are separated. Thus, to ensure good parting, the mould surface (at contact of cope and Drag) should be treated with parting sand or some other parting material.

It is also sprinkled or applied on the pattern surface (before the molding sand is put over it) to avoid its sticking and permit its easy withdrawal from the mould. The parting sand is fine dry sand.

Backing or floor or black sand:

This is the sand which is used to back up the facing sand and to fill the whole volume of the flask. Old, repeatedly used molding sand is mainly employed for this purpose.             

  Core sand:

                                The core sand mainly consists of silica sand and an organic binder, with very little, if any, clay content. The presence of clay in core sand reduces its permeability and collapsibility. The core sand may contain small percentages of other constituents also, to enhance its properties.            

 Loam sand:

                                50 % of clay and dried hard and using for large castings

 

 

 

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, mechanical Engineering, Gears, spur gears,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Face Gears,IC engine,Metal Casting,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns,Mechnical Previous Years Gate Question Papers ,Mechanical-old-question-paper,Core and Core Box,Shell Moulding,Permanent mold casting,Investment Casting,Die Casting,Centrifugal Casting,Workshop Technology Quiz,Milling Quiz,Metal Quiz,Mechanical Process Quiz,Chemically Bonded Molding Systems,Unbonded Sand Processes,Green Sand Molding,Gases Iin Metal Casting,Plaster Mold Casting,Ceramic Mold Casting,Vacuum Casting,Hot Chamber Die Casting,Continuous Casting,Casting Process Quiz,Types Of Molding Sand In Casting-process,