Sep. 25
Assignment
 Rolling:
Rolling is the process in which reducing the thickness or changing in cross section area of
work piece by compressive force applied by two rolls.
Figure 1: Rolling
 Product of rolling:
 Seamless Ring
 Taps
 Seamless tube
1. Seamless Rings:
Figure 2: Seamless Rings
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Sep. 25
Assignment
 Manufacturing process of Rings:
Ring Rolling:
In the ring rolling process, a thick ring is expand into a large diameter ring with a reduce
cross-section. The ring is placed between two rolls, one of which rotate, and reduce the
thickness of work piece by placing the work piece between rolls and rotate it. The volume
of ring constant during deformation, the reduction in thickness is compensated by an
increase in the ring’s diameter.
The ring-shaped blank may be produced by such means as by cutting from plate, by
piercing or by cutting a thick-walled pipe. Various shaped can be ring rolled by the use of
shaped rolls. Typically application of ring rolling are large rings for rockets and turbines,
gearwheel rims, ball-bearing and roller-bearing races, flanges, and reinforcing rings for
pipes.
This process can be carried out at room temperature, depending on the size, strength, and
ductility of work piece material. Compare to other manufacturing processes capable of
making the same part, the advantage of this process are short production time, material
saving, close dimensional tolerances, and favorable grain flow in the product.
Figure 3 Ring rolling process
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Assignment
2. Taps:
 Manufacturing process of rolling taps:
Thread Rolling:
The thread-rolling process is a cold-forming process by which straight or tapered threads
are found on round rods, by passing them between dies. Threads are formed on the rod or
wire each stroke of a pair of flat reciprocating dies. Typically products are screws, bolts,
and similar threaded parts. Depending on die design, the major diameter of a rolled thread
may or may not be larger than a mechanical thread. That is the same as the blank
diameter. In either case, volume constancy is maintained, because not material is
removed.
The process is capable of generating similar shapes, such as grooves and various gear
forms, another surface, and it can be used in the production of almost all threaded
fastener at high rating production. In other methods, threads are formed with rotary dies
at production rates as high as 80 pieces per second.
The thread-rolling process has the advantage of generating threads without loss of
material and with a good strength. The surface finish is very smooth, and the process
induces compressive residual stresses on the work piece surface, thus improving fatigue
life.
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Assignment
Thread rolling is superior to the other method of manufacturing threads, because
machining the thread cuts through the grain-flow line of the material, whereas rolling the
thread leaves a grain flow pattern that improve the strength of thread.
Figure 4Thread rolling (Flat dies)(Tow rollers die)
Threads are roller on metal in the soft condition, because of ductility requirement. However, they
can subsequently be subjected to heat treatment and, if necessary, to final machining or to
grinding. For metal in hard condition, threads are machined and ground. Rolled threads are
readily available in the most widely used standard thread forms uncommon or special-purpose
threads are usually machined.
3. Seamless tube:
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Sep. 25
Assignment
 Manufacturing process of seamless tube:
Tube Rolling:
Rotary tube piercing is a hot-working process for making long, thick-walled seamless
pipe and tubing. It is based on the principle that when a round bar is subjected to radial
compressive force, tensile stresses develop at the center of the bar. When it is
subsequently subjected to cyclic compressive stresses, a cavity begins to form at the
center of the bar. This phenomenon can be demonstrated with a short piece of round
eraser, by rolling it back and forth on the hard flat surface.
Rotary piercing is carried out using an arrangement of rotating rolls. The exes of the rolls
are skewed, in order to pull the round bar through the rolls by the axial component of the
rotary motion. An internal mandrel assists the operation, buy expanding the hole and
sizing the inside diameter of the tube. The mandrel may be held in place by a long rod, or
it may be a floating mandrel without a support because of the severe deformation that the
bar undergo, the material must be high in quality and free from defect.
Figure 5 Seamless tube Rolling
The diameter and thickness of tube and pipes can be reduced by tube rolling. This uses
shaped rolls. Some of those operations can be carried out either with or without an
internal mandrel. In the pilger mill, the tube and an internal mandrel undergo a
reciprocating motion; the rolls are specially shaped and are rotated continuously. During
the gap cycle on the roll, the tube is advanced and rotated, starting another cucle of tube
reduction.
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Sep. 25
Assignment
 References:
Book Name: Manufacturing Engineering and Technology.
Author: Steven R. Schmid
Edition: Fourth Edition.
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