Download - recent Advances in Sand Casting

5/27/2018 recent Advances in Sand Casting

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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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10

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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11

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.), Butterworth-Heinemann, ISBN 0-7506-4790-

66


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TYPES OF MOLDING PROCESS

1 Expendable Mold

1.1 Permanent Pattern

1.1.1 Sand Casting

1.1.2 Plaster Molding

1.2 Expendable Pattern

1.2.1 Lost Foam1.2.2 Lost Wax

(investment casting)

1 Permanent Mold1.1 Die

1.1.1 Hot Chamber

1.1.2 Cold Chamber

1.1.3Thixotropic

Mold prepertation =) metal heating =) pouring =) cooling =) processing


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Expandable mold

permanent pattern

SAND CASTING


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SAND CASTING


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The set of channels through which a moltenmetal flows to the mold cavity is called gating

system.

Typical gating system consists of a pouring

cupand a spruereceiving the poured melt,

runnera channel through which the melt is

supplied to the gates through which the

molten metal enters the mold cavity.


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