drilling on cnc machine (me181056)

Title: To Perform Drilling on CNC Milling machine
Location: CIM Center
MANUFACTURING PROCESSESS LAB – VII
Student’s Name: MUHAMMAD SHEHRYAR IMTIAZ Registration Number/Roll No. ME181056
Max. Marks: 20
A. Introduction
CNC
The abbreviation CNC stands for Computer(ized) Numerical(ly) Control(led), and refers
specifically to the computer control of machine tools for the purpose of (repeatedly) manufacturing
complex parts in metal as well as other materials, using a program written in a notation conforming
to the EIA-274-D standard and commonly called G-code
CNC was developed in the late 1940s and early 1950s by the MIT Servomechanisms Laboratory.
CNC machines were relatively briefly preceded by the less advanced NC, or Numerical(ly)
Control(led), machines. The introduction of CNC machines radically changed the manufacturing
industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to
produce, and the number of machining steps that required human action have been dramatically
reduced. With the increased automation of manufacturing processes with CNC machining,
considerable improvements in consistency and quality have been achieved. CNC automation
reduced the frequency of errors and provided CNC operators with time to perform additional tasks.
CNC automation also allows for more flexibility in the way parts are held in the manufacturing
process and the time required to change the machine to produce different components. In a
production environment, a series of CNC machines may be combined into one station,commonly
called a "cell", to progressively machine a part requiring several operations. CNC machines today
are controlled directly from files created by CAM software packages, so that a part or assembly
can go directly from design to manufacturing without the need of producing a drafted paper
drawing of the manufactured component. In a sense, the CNC machines represent a special
segment of industrial robot systems, as they are programmable to perform many kinds of
machining operations (within their designed physical limits, like other robotic systems).
G CODES
G-code is a common name for the programming language that is used for NC and CNC machine
tools. It is defined in EIA RS-274-D. G-code is also the name of any word in a CNC programthat
begins with the letter G, and generally is a code telling the machine tool what type of action to
perform, such as:
 Rapid move
 Controlled feed move in straight line or arc
 Series of controlled feed moves that would result in a hole being drilled.
 Change a pallet
To Perform Drilling on CNC Milling machine

 Set tool information such as offset.
There are other codes; the type codes can be thought of like registers in a computer
 X position
 Y position
 Z position
 M code (another "action" register)
 F feed rate
 S spindle speed
 N line number
 R Radius
 T Tool selection
 I Arc data X axis
 J Arc data Yaxis
G-code files are output by CAM software such as Smartcam, Gibbscam, Featurecam, Edgecam,
Mastercam, etc. G-code is also output by specialized CAD systems used to design printed circuit
boards. Such software must be customized for each type of machine tool that it will be used to
program.

DRILLING
Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-
section in solid materials. The drill bit is usually a rotary cutting tool, often multi-
point. The bit is pressedagainst the work-piece and rotated at rates from hundreds
to thousands of revolutions per minute. This forces the cutting edge against the
work-piece, cutting off chips (swarf) from the hole as it is drilled. There are
different types of drilling operations, few of them are listed below:
1. Reaming
2. Tapping
3. Counter Boring
4. Counter Sinking
5. Centering (Center Drilling)
6. Spot Facing

B. Post Lab
Q1) A drilling operation is to be performed with a 12.7-mm diameter twist drill
in a steel work-part. The hole is a blind hole at a depth of 60 mm and the point
angle is 118°. The cutting speed is 626.6 rpm and the feed is 0.30 mm/rev.
Determine:
(a) The cutting time to complete the drilling operation [4]
(b) Metal Removal Rate during the operation, after the drill bit reaches full
diameter. [2]

Q2) Briefly explain any 4 types of drilling operations? [8]
REAMING:
Reaming is used to slightly enlarge a hole, to provide a better tolerance on its
diameter, and to improve its. The tool is called a ‘reamer’ and is usually has straight
flutes. The tools used to ream the hole are hand reamer, fluting reamer, machine
reamer and chucking reamer.
TAPPING:
Tapping is used to provide internal screw threads on an existing hole. This operation
is performed by a tool called a ‘tap’. Taping can also be done by robotic hands and by
manual means. Taping is extensively used in drilling operations.
CENTERING:
Also called center drilling, this operation drills a starting hole to accurately establish
its location for subsequent drilling. The tool is called a center drill. Centre drilling is
used for delicate industrial works especially in major automobile industries.
COUNTER BORING:
Counter boring provides a stepped hole, in which a larger diameter follows a smaller
diameter partially into the hole. A counter-bored hole is used to seat bolt heads into a
hole so the heads do not protrude above the surface.

Q3) Center drilling operation can be used to assist other drilling operations and
helps prevent flaws in them. How? [3]
The purpose of the centre drill is to create an accurate centre hole in the face of a job
so as a live centre can be inserted to support the weight and load of the job, whilst
turning it. It is just marking and making a room so that drill bit pointer area fits
perfectly before performing a job. This reduces miss direction just before am initial
drill is made. If that initial hole is flawed, then whole further drill is also faulty
because it moves forward on. Also, the vibration on the work piece also disturbs the
initial hole. So, centre drill makes the room and other operation either it is drilling,
milling, taping or boring can be made easily.
Q4) Why a periodic withdrawal of drill bit is necessary from the hole during a
Pecking operation. [3]
Periodic withdrawal is necessary because continuous chips are being formed, it is
forced through the flutes to the work surface. The usual friction in metal cutting
between the chip and the rake face of the cutting edge and the rubbing between the
outside diameter of the drill bit and the newly formed hole, are two reasons for chip
making and also increase the drill deficiency in making further cut. To prevent this
either we must lubricate the hole while drilling or pecking is used to remove the chips
in the hole and make the drilling area clear before further drilling.

drilling on cnc machine (me181056)

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