Extrusion, Drawing and Sheet Metal Forming

1. Shri. Shamrao Patil (Yadravkar) Educational & Charitable Trust’s
Sharad Institute of Technology, College of Engineering Yadrav- (Ichalkaranji)
(Approved by AICTE, New Delhi, Recognized by Government of Maharashtra & Affiliated to DBATU, Lonere)
Accredited by NAAC ‘A’ Grade and NBA, ISO 9001:2015 Certified Institute
Recognized u/s 2(f) and 12(B) of the UGC Act 1956
Unit 3: Extrusion, Drawing and
Sheet Metal Forming
Mr. S M Ghanvat
ME (CAD/CAM/CAE)
Assistant Professor
Mechanical Department

2. Introduction
Extrusion and drawing involve, respectively, pushing or pulling a material
through a die basically for the purpose of reducing or changing its cross-
sectional area.
Typical parts made by extrusion and drawing: Long pieces having a wide
variety of constant cross sections, rods, shafts, bars for machinery and
automotive power-train applications, aluminum ladders, collapsible tubes,
wire for numerous electrical and mechanical applications and musical
instruments.

3. EXTRUSION PROCESSES
Extrusion processes can be classified as followed:
(A) Hot Extrusion
(i) Forward or Direct extrusion.
(ii) Backward or Indirect extrusion.
(B) Cold Extrusion
(i) Hooker extrusion.
(ii) Hydrostatic extrusion.
(iii) Impact extrusion.
(iv) Cold extrusion forging.

4. Process variables in direct extrusion
Forward or direct extrusion process

5. Backward or indirect extrusion

6. Comparison between Forward and Backward extrusion

7. Cold Extrusion Processes
Hooker extrusion process

8. Hydrostatic extrusion
This is a direct extrusion process.
But the pressure is applied to the metal blank on all sides through a fluid
medium.
The fluids commonly used are glycerine, ethyl glycol, mineral oils, castor oil
mixed with alcohol etc.
Very high pressures are used – 1000 to 3000 MPa.
Relatively brittle materials can also be successfully extruded by this method.

9. Impact extrusion

10. Cold extrusion forging

11. Comparison between Hot extrusion and Cold extrusion

12. Extrusion Defects
Sometimes the surface of extruded metal/products develops surface cracks.
This is due to heat generated in the extrusion process.
These cracks are specially associated with aluminium, magnesium and zinc
alloy extrusions.
The extruded product can develop internal cracks also.
These are variously known as centre burst, centre cracking and arrowhead
fracture.
There are three principal extrusion defects: surface cracking, pipe, and internal
cracking.

13. Extrusion Equipment