MET 141
Manufacturing
Processes and
Materials
Change of Form
Spring 2002
Introduction
Other forms of manufacturing involve
methods that reduce or increase the volume of a
material.
• When changing the form of a workpiece, we are
only changing the shape.
• Major methods include:
• Melting the material
• Powdering the material
• Deforming the material
• These processes include many methods of:
• Casting Materials
• Drawing
• Powder metallurgy
• Spin forming
• Forging
• High-energy
• Bending
forming
Casting
Involves placing a liquid material into a
mold where it hardens or solidifies into a final
shape.
• Variations of casting include:
• Sand Casting
• Permanent Mold Processes
• Green Sand
• Gravity feed
• Dry Sand
• Low-pressure feed
• Investment processes
• Hot-chamber Die
• Lost wax
• Cold-chamber Die
• Shell mold
• Centrifugal
• Centrifuged
• Slush
• Continuous
Basic Concept
• Many terms used in sand casting apply to other
forms of casting.
• Basic concept of sand casting is that fine sand is
packed around a pattern to form a mold.
• Pattern is then removed leaving a cavity.
• Molten metal, ceramic slurry, or other liquefied
material is poured in.
• Once solidified, the mold is opened and the
work piece is removed.
Patterns
• In sand casting, patterns are generally made
out of a hardwood.
• Since most metals shrink when they cool the
pattern must be made oversized.
• Shrinkage of steel castings vary from 0.5%
to 2% depending on the alloy in the steel
Two Significant Problems
• Two significant problems.
• Parting plane through the longest horizontal
section
• Draft angle-typically about 2 degrees
Sand Casting Procedure
• Only damp sand will work.
• Oil or water is mixed into sand (mulling)
• Sand is packed into a flask around a pattern
• 2 parts: upper (cope), lower (drag)
• Vertical hole (sprue) is cut in which to pour liquefied
material.
• Horizontal holes (runners) are cut from sprue to
pattern.
• Pattern is removed and two halves are mated together.
Sand Casting Procedure
• Dam is created to allow molten metal to flow
into sprue under oxide layer.
• Gate controls and allows even horizontal flow of
material into the mold (good grain structure)
• Trap catches loose sand
• Vents allow steam or trapped gas to escape.
Sand Casting Procedure cont.
• Riser allows molten material to completely fill
the mold.
• Metal is poured slowly and evenly until seen in the riser.
• Metal solidifies.
• Most metals shrink on the surface.
• Sprue and riser is cut from the part.
Casting Assembly Line
Multiple Casts
• Single sprue tree
• Multiple runners and
patterns
Sand Casting
(Green Sand)
Characteristics
Advantages
Disadvantages
Sand Casting
(Dry Sand)
Characteristics
Advantages
Disadvantages
Investment Casting
(Lost Wax)
Characteristics
Advantages
Disadvantages
Investment Casting
(Shell Mold)
Characteristics
Advantages
Disadvantages
Investment Casting
(Centrifuged)
Characteristics
Advantages
Disadvantages
Investment Casting
(Vacuum)
Characteristics
Advantages
Disadvantages
Investment Casting
(Vacuum)
Permanent Mold
(Gravity Feed)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Low Pressure Feed)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Hot Chamber Die)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Cold Chamber Die)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Centrifugal)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Centrifugal)
Permanent Mold
(Slush)
Characteristics
Advantages
Disadvantages
Permanent Mold
(Continuous Pour)
Characteristics
Advantages
Disadvantages
Casting Based on Weight
Casting Based on Material
Investment Casting
(Lost Wax)
Characteristics
Advantages
Disadvantages
Casting Based on Shape