CNC Machinery
 Module Objectives:
 Define Machining.
 Recognize the main machining processes.
 Calculate the cutting and rotational speeds for turning
and milling.
Basics of Machining
 Have you ever think how these parts are produced?
Machining
 Machining is one of the manufacturing techniques used to
produce parts.
 The modern types of machining techniques include the use of
CNC (Computer Numerical Control) machines.
 To understand CNC basics, let’s have a look at the conventional
machining.
Here we can see how a small gear could be produced:
 Machining is a class of material-
working processes that involves
using a power-driven machine
tool to shape metal.
 The most important conventional machine tools
that shape materials to a size by cutting away
unwanted portions, are:
 Turning (Lathe) machine.
 Milling machine.
Turning (Lathe) Machine
The primarily function, of the
turning machine is to produce a
cylindrical surfaces.
Turning Machine
Turning machine and its
main parts
Turning Machine Operations
Some important turning
machine operations are:
1. Facing:
Is to remove a small
of material (around
mm) from the end
workpiece to produce
and true face and
bring the workpiece
desired length.
amount
1 – 2
of the
smooth
also to
to the
Facing
2. Parallel Turning
Is to move the cutting tool
parallel to the workpiece
axis in order to reduce its
diameter.
3. Drilling
Is to make a hole having a
specific diameter and depth in a
material.
Drilling could be done by special
drilling machines, milling or
turning machine.
Drilling using a drilling machine
Drilling using Lathe machine
4. Threading
To make spiral or helical cuts on a
material. These cuts are usually found on
bolts (external threading) or nuts
(internal threading).
Thread in technical
drawing
External Thread
(outside) Bolt
Internal Thread
(inside) Nut
5. Recessing
To make a groove having a
specific width and depth into the
material.
Internal Recess
External Recess
6. Taper cutting
To increase or decrease the diameter of the
workpiece in a uniform rate.
Tapered Part
Taper cutting on the turning
machine
Name The Following Turning Operations ?
Milling Machine
Milling is to use a rotating multitoothed cutter into the workpiece to
remove material, in order to make gears, slots, holes, pockets and
many
different
shapes.
Milling Machine
Generally Milling machines
are classified into :
1. Vertical milling machine
The spindle positioned perpendicular
to its worktable.
Vertical Milling
Machine
Milling Machine
2. Horizontal milling machine
The
cutting
tool
positioned
horizontally and parallel to the
worktable.
Horizontal Milling
Machine
Parts of Milling Machine
Examples of Milling Operations
 milling.avi
 milling machine operations.wmv
Example of Milling Operations
Turning
and
Milling
Cutters
Available in different shapes, and made of
different special materials. For example:
• High Speed Steel (HSS).
•Tungsten Carbide.
Turning Cutting tools
Milling Cutters
Cutting Speed and Feed
 Cutting speed (Vc)
 The cutting speed is the speed at which the circumference of
the work part moves along the cutter.




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The magnitude of cutting speed is determined by the:
1. Material of the work part.
2. Material of the cutter.
3. Infeed (surface quality, roughing, finishing).
4. Life of the tool.
 The cutting speed is chosen from tabulated values.
Rotational Speed (n)
 Once the cutting speed is chosen, the rotational speed
has to be calculated.
 The following formula can be used to calculate the
rotational speed:




Vc
n
 Xd
Where,
Vc: the cutting speed in (m/min).
d: the work part diameter in (m).
n:
the rotational speed in revolution per minute
(RPM) (Rev/min).
Infeed Speed (Vf)
Together with the cutting movement,
infeed allows a continuous chip removal
during several rotations. The infeed
speed (Vf) is indicated in mm/min.
The following formula is used to
calculate the infeed speed:
Vf = n x f
Where:
Vf: the infeed speed in mm/min
n:
the rotational speed in
revolution
per minute (RPM).
f: the infeed in mm/rev; chosen
from
tabulated values.
Examples
 Example 1:
 How many number of rotations (n) are required, if the
diameter to be machined is 12 mm and the cutting speed is
283 m/min?
 Example 2:
 Calculate the cutting speed for turning if the cutting is done
on 60 mm diameter workpiece and at number of rotations of
1500 RPM?
 Example 3:
 Calculate the cutting speed for milling if the milling tool
diameter (d) = 50 mm and the number of rotations (n) = 520
rev./min?
 Example 4:
 Calculate the number of rotations (n) if the milling tool
diameter = 12 mm and the cutting speed Vc = 120 m/min.