recent advances in sand casting

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brief history and recent advances

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    Traditional Manufacturing Processes

    Casting

    Forming

    Sheet metal processing

    Cutting

    Joining

    Powder- and Ceramics Processing

    Plastics processing

    Surface treatment

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    Casting

    Refractory moldpour liquid metalsolidify, removefinish

    VERSATILE: complex geometry, internal cavities, hollow

    sections

    VERSATILE: small (~10 grams)very large parts (~1000 Kg)

    ECONOMICAL: little wastage (extra metal is re-used)

    ISOTROPIC: cast parts have same properties along all

    directions

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    Different Casting Processes

    Process Advantages Disadvantages Examples

    Sand many metals, sizes, shapes, cheap poor finish & tolerance engine blocks,cylinder heads

    Shell mold better accuracy, finish, higher

    production rate

    limited part size connecting rods, gear

    housings

    Expendable

    pattern

    Wide range of metals, sizes,

    shapes

    patterns have low

    strength

    cylinder heads, brake

    components

    Plaster mold complex shapes, good surface

    finish

    non-ferrous metals, low

    production rate

    prototypes of

    mechanical parts

    Ceramic mold complex shapes, high accuracy,

    good finish

    small sizes impellers, injection

    mold tooling

    Investment complex shapes, excellent finish small parts, expensive jewellery

    Permanent

    mold

    good finish, low porosity, high

    production rate

    Costly mold, simpler

    shapes only

    gears, gear housings

    Die Excellent dimensional accuracy,

    high production rate

    costly dies, small parts,

    non-ferrous metals

    gears, camera bodies,

    car wheels

    Centrifugal Large cylindrical parts, good

    quality

    Expensive, few shapes pipes, boilers,

    flywheels

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    Sand Casting

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    History of metal casting Late 20th Century

    Early 1970sThe Semi-Solid Metalworking (SSM)

    process is conceived of at Massachusetts Institute of

    Technology. It combines aspects of casting with aspects

    of forging.

    1971The Japanese develop V-Process molding. This

    method uses unbonded sand and a vacuum. 1972The first production Austempered Ductile Iron

    (ADI) component is produced by Wagner Castings

    Company.

    1976Compacted graphite iron (CGI), an iron withelongated graphite particles with rounded edges and

    roughened surfaces, is developed in the U.K. It has

    characteristics of both gray and ductile iron.

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    1982The Warm Box binder system was introduced.

    1993First foundry application of a plasma ladle refiner

    (melting and refining in one vessel) occurs at Maynard

    Steel Casting Company in Milwaukee, WI. 1995Babcock and Wilcox, Barberton, OH, patent a lost

    foam vacuum casting process to produce stainless steel

    castings with low carbon content.

    1996Cast metal matrix composites were first used in aproduction model automobile in the brake rotors for the

    Lotus Elise.

    1997Electromagnetic casting processes developed by

    Argonne and Inland Steel Corporation. Electromagnetic

    edge containment greatly reduces cost and energy

    expenditures in steel production

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    Recent advances in sand casting technology

    After 5000 years of technological advances, metal casting

    plays a greater part in our everyday lives and is more essential

    than it has ever been.

    There are various developments in sand casting technology

    which include advanced permanent molding, flexible machines

    for metal mold casting, improved molding and solidification

    practices for sand casting, rapid prototyping, Computer

    modeling and simulation

    Advanced casting processes are rapidly being adopted. These

    include lost foam castings in volume production, continuous

    castings, advanced semi permanent mold casting, semisolidcasting(SSM) and no bake Sand Castings

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    Lost foam casting

    Lost foam casting(LFC) is a type of investment casting process

    that usesfoam patternsas a mold. The method takes advantage

    of the properties of foam to simply and inexpensively create

    castings that would be difficult to achieve using other casting

    techniques.

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    9

    Variations and Developments

    Continuous casting

    Lost foam molding

    3D Printing of Investment tooling

    Direct printing with metal droplets

    Uniform metal spray

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    Continuous casting ref AISI

    Steel from the electric or basic oxygen furnace is tapped into a ladle and taken tothe continuous casting machine. The ladle is raised onto a turret that rotates the ladleinto the casting position above the tundish. Referring to Figure 2,liquid steel flows outof the ladle (1) into the tundish (2), and then into a water-cooled copper mold (3).Solidification begins in the mold, and continues through the First Zone (4) and Strand Guide (5).In this configuration, the strand is straightened (6), torch-cut (8), then discharged (12)for intermediate storage or hot charged for finished rolling.

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    3D Printing

    of Investment cast tooling

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    12

    Shell and part (Turbine blade)

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    13

    Microcasting of droplets

    CMUMIT

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    14

    Environmental Issues

    Smelting

    Energy

    Off-gassing see AFS webpage on green sand emissions;http://www.afsinc.org/environmental.html

    Cooling water

    Waste sand disposal

    Off shore locations

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    Metal Smelting; reducing oxides and sulfides to

    metal..

    http://www.steel.org/learning/howmade/blast_furnace.htm

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    Environmental loads by

    manufacturing sector

    Carbon Dioxide and Toxic Materials per Value of Shipments

    0

    0.5

    1

    1.5

    2

    2.53

    3.5

    4

    4.5

    5

    Chemicals

    Petroleum

    andC

    oal

    Plastics

    and

    Rubber

    PrimaryM

    etal

    Fabricated

    Met

    al

    Machinery

    Electronic

    Transportation

    Manufacturing industries

    Weight/Dollars

    CO2 (metric ton/$10,000)

    Toxic Mat'ls (lb/$1000)

    EPA 2001, DOE 2001

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    Vacuum castingand molding

    Similar to investment casting, except: fill mold by reverse gravity

    Easier to make hollow casting: early pour out

    3D Printing of Investment tooling:-

    The Technology Used for

    Creating 3D Printed Concept Models

    1. Fused Deposition Modeling (FDM)

    Technology

    2. PolyJet 3D Printing Technology

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    No Bake Sand Casting No Bake is a casting process that uses chemical binders to bond the molding sand.

    The sand is then transported to the mold fill station in preparation for filling of the

    mold. A mixer is then used to blend sand with the chemical binder and the catalyst.

    When the sand exits the mixer, the binder begins the hardening process.

    After the compaction process, a rollover process is used to remove the mold from

    the pattern box. The mould is then readied for handling the molten metal. After a

    shakeout process, the molded sand is taken away from the casting. Then various

    procedures follow including the finishing and the sand can be reclaimed by thermalmeans.

    In the No-Bake resin sand casting process, sand molds are created using a wood,

    metal, or plastic pattern. Sand is mixed with a plastic binder in a high-speed mixer.

    This sand is deposited into box containing the pattern and all essential gating, risersand chills for pouring.

    The sand mixture sets up hard in a few minutes and the mold is removed from the

    pattern. Cores for forming internal passages in the castings are made using the same

    process. Cores are carefully placed into the molds. The molds are then closed and

    are ready for pouring.

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    Conclusion:As there is a growth in technology , there is an advancement in each and every

    stage of casting process which proportionally reduces the cost and time of

    manufacturing with an improved quality of a product.

    References:-1. Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in

    Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.

    2. Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994), Manufacturing Processes ReferenceGuide, Industrial Press Inc., ISBN 0-8311-3049-0.

    3. Rao, T. V. (2003), Metal Casting: Principles and Practice, New Age International, ISBN

    978-81-224-0843-0.

    4. Campbell, John (2003), Casting (2nd ed.)