Extrusion

1. MANUFACTURING
TECHNOLOGY – I
CRAFTED BY:
RAMESH KUMAR A
Assistant Professor
Sona College of Technology
Salem
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2. EXTRUSION
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3. EXTRUSION
A compression forming process in which the work metal is forced
to flow through a die opening to produce a desired cross-
sectional shape
PROS:
variety of sections possible (hot extrusion)
grain structure and strength enhancement (cold)
close tolerance (cold)
no material wastage
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4. TYPES OF EXTRUSION
Direct Extrusion
The ram forces the work billet metal to move forward
to pass through the die opening
Indirect Extrusion
The die is mounted to the ram rather than at the
opposite end of the extruder container housing
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5. DIRECT EXTRUSION
Friction increases the extrusion force
Hollow section is formed using a mandrel
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6. INDIRECT EXTRUSION
Metal is forced to flow through
the die in an opposite direction
to the ram’s motion
Lower extrusion force as the
work billet metal is not moving
relative to the container wall
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7. EXTRUSION PROCESSES
Hot extrusion
 Keeping the processing
temperature to above the re-
crystalline temperature
 Reducing the ram force,
increasing the ram speed, and
reduction of grain flow
characteristics
 Controlling the cooling is a
problem
 Glass may be used as a
lubricant
Cold extrusion
 Often used to produce discrete
parts
 Increase strength due to strain
hardening, close tolerances,
improved surface finish,
absence of oxide layer and
high production rates
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8. EXTRUSION
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9. IMPACT EXTRUSION
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combination

10. IMPACT EXTRUSION
Impact extrusion is performed at higher speeds and shorter
strokes than conventional extrusion
It is for making discrete parts
For making thin wall-thickness items by permitting large
deformation at high speed
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11. HYDROSTATIC EXTRUSION
 The billet is completely surrounded by pressurized liquid, except where the
billet contacts die
 Using hydrostatic system to reduce the friction and lower the power
requirement
 Sealing is the major problem
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12. EXTRUSION DEFECTS
 Centre-burst
 Internal crack due to excessive
tensile stress at the centre
possibly because of high die
angle, low extrusion ratio
 Piping
 Sink hole at the end of billet
under direct extrusion
 Surface cracking
 High part temperature due to low
extrusion speed and high strain
rates
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13. EXTRUSION DEFECTS
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