1. Bulk deformation Processes II
ENM208
Bulk deformation Processes II
ANADOLU U N I V E R S I T Y
Industrial Engineering Department
– Bulk Deformation Processes in Metal Forming – II
2006
Saleh AMAITIK

2. Extrusion Manufacturing Processes
Compression forming process in which the work metal is forced to flow through a die opening to produce a desired cross‑sectional shape.
Process is similar to squeezing toothpaste out of a toothpaste tube
In general, extrusion is used to produce long parts of uniform cross-sections
Spring 2005

3. Extrusion is carried out in various ways.
Manufacturing Processes
Types of Extrusion
Extrusion is carried out in various ways.
Extrusion can be classified based on the following
1- Physical Configuration
Direct extrusion.
Indirect extrusion.
2- Working temperature
Cold extrusion.
Warm extrusion.
Hot extrusion.
3- Process type
Continuous process.
Discrete Processes.
Spring 2005

4. Direct Extrusion Manufacturing Processes
Also called Forward Extrusion is illustrated in figure below
A metal billet is loaded into a container, and a ram compresses the material, forcing it to flow through one or more openings in a die at the opposite end of the container.
Starting billet cross section usually round, but final shape is determined by die opening
Spring 2005

5. Direct Extrusion Manufacturing Processes
Hollow sections (for example, tubes) are possible in direct extrusion.
The starting billet is prepared with a hole parallel to its axis. This allows passage of a mandrel that is attached to the block.
As the billet is compressed, the material is forced to flow through the clearance between the mandrel and the die opening.
(a) Direct extrusion to produce a hollow or semi‑hollow cross‑section; (b) hollow and (c) semi‑hollow cross‑ sections
Spring 2005

6. Indirect Extrusion Manufacturing Processes
Also called Backward Extrusion or Reverse Extrusion is illustrated in
figure below
Indirect extrusion to produce
(a) a solid cross‑section and (b) a hollow cross‑section
Spring 2005

7. Hot versus Cold Extrusion
Manufacturing Processes
Hot versus Cold Extrusion
Extrusion can be performed either hot or cold, depending on the work metal and amount of strain to which it is subjected during deformation.
Metal typically extruded hot include aluminum, copper, magnesium, zinc, tin, and their alloys. These same metals are sometimes extruded cold.
Steel alloys are usually extruded hot, although more ductile grades are sometimes cold extruded (for example low-carbon steel).
Aluminum is the probably the most ideal metal for extrusion (hot and cold), and many commercial products are made by this process (for example, door and window frames).
Spring 2005

8. Continuous versus Discrete Extrusion
Manufacturing Processes
Continuous versus Discrete Extrusion
Some extrusion operations producing very long sections in one cycle, but these operations are limited by the size of the billet that can be loaded into the extrusion container.
These processes are more accurately described as semi-continuous extrusion.
In a discrete extrusion operation, a single part is produced in each extrusion cycle.
- Impact extrusion is an example of the discrete processing case
Spring 2005

9. Analysis of Extrusion Extrusion Ratio Manufacturing Processes
Also called the reduction ratio, it is defined as
where rx = extrusion ratio;
Ao = cross-sectional area of the starting billet; and
Af = final cross-sectional area of the extruded section
Applies to both direct and indirect extrusion
Spring 2005

10. The True Strain in Extrusion
Manufacturing Processes
Analysis of Extrusion
The True Strain in Extrusion
For ideal deformation process:
The actual true strain is given by the following empirical equation:
Where x = extrusion strain; and a and b are empirical constants for a given die angle. Typical values of these constants are a = 0.8 and b = 1.2 to 1.5
Spring 2005

11. Analysis of Extrusion Extrusion Pressure Manufacturing Processes
For ideal deformation process:
For indirect extrusion
Where
Is the average flow stress during deformation based on ideal strain 
Spring 2005

12. Extrusion Force and Power
Manufacturing Processes
Analysis of Extrusion
Extrusion Force and Power
The ram force in direct and indirect extrusion is simply given as
Where F = ram force in extrusion (N), p = extrusion pressure (MPa), and A0 = billet area (mm2)
The power required to carry out the extrusion operation is simply
Where P= power in (J/s); F = ram force (N), and v = ram velocity (m/s)
Spring 2005

13. Manufacturing Processes
Wire and Bar Drawing
Drawing is an operation in which the cross section of a bar, rod, or wire is reduced by pulling it through a die opening.
Similar to extrusion except work is pulled through die in drawing (it is pushed through in extrusion)
Spring 2005

14. Wire Drawing versus Bar Drawing
Manufacturing Processes
Wire Drawing versus Bar Drawing
The basic difference between bar drawing and wire drawing is the stock size that is processed.
Bar Drawing is the term used for large-diameter bar and rod stock.
Wire Drawing applies to small-diameter stock.
wire sizes down to 0.03 mm are possible
Although the mechanics are the same, the methods, equipment, and even terminology are different
Spring 2005

15. Drawing Practice and Products
Manufacturing Processes
Drawing Practice and Products
Drawing practice:
Usually performed as cold working
Most frequently used for round cross‑sections
Products:
Wire: electrical wire; wire stock for fences, coat hangers, and shopping carts
Rod stock for nails, screws, rivets, and springs
Bar stock: metal bars for machining, forging, and other processes
Spring 2005

16. Beginning stock has large diameter and is a straight cylinder
Manufacturing Processes
Bar Drawing
Accomplished as a single‑draft operation ‑ the stock is pulled through one die opening
Beginning stock has large diameter and is a straight cylinder
Hydraulically operated draw bench for drawing metal bars
Spring 2005

17. Wire Drawing Manufacturing Processes
Continuous drawing machines consisting of multiple draw dies (typically 4 to 12) separated by accumulating drums
Each drum provides proper force to draw wire stock through
upstream die .
Each die provides a small reduction, so desired total reduction is achieved by the series
Spring 2005

18. Annealing – to increase ductility of stock
Manufacturing Processes
Preparation of the Work for Wire and Bar Drawing
Annealing – to increase ductility of stock
Cleaning - to prevent damage to work surface and draw die
Pointing – to reduce diameter of starting end to allow insertion through draw die
Spring 2005

19. Analysis of Drawing Reduction Ratio Draft Manufacturing Processes
Change in size of work is usually given by area reduction:
where r = area reduction in drawing;
Ao = original area of work (mm2) ; and
Af = final work (mm2)
Draft
The difference between original and final stock diameters
Where d = draft (mm), Do = original diameter of work (mm), and Df = final work diameter (mm).
Spring 2005

20. Analysis of Drawing True Strain Drawing Stress Drawing Force
Manufacturing Processes
Analysis of Drawing
True Strain
If no friction occurred in drawing, true strain could be determined as follows:
Drawing Stress
The stress that results from this ideal deformation is given by
Drawing Force
The draw force is then the area of the drawing cross section multiplied by draw stress
Spring 2005