1. CNC MILLING
Under the guidance of
DR.SHANTALA
associate professor
Department of Mechanical Engineering
RV Institute of Technology and Management (RVITM) Bengaluru
ANAND GHALE
1RF19ME005
3. CONVENTIONAL MACHINES
In a conventional m/c parameters like feed, depth of cut and speed
are manually controlled by the operator.
The accuracy of the job depends mainly on the skill of the worker.
These machines have the following disadvantages.
1. More time consumption.
2. Less accuracy.
3. Less production.
4. Requires skilled labour.
5. More wastage of material
EVOLUTION OF CNC MACHINES
4. • Numerical control means directing, guiding or retaining power over something by the
use of numbers.
•Numerical control can defined as a form of programmable automation on which the
process is controlled by numbers, letters and symbols
•. The year which followed world war-II increased the needs of aerospace industries that
created demands on the capabilities of m/c tools. Using techniques which had advanced
rapidly during the war, machine tool designers & electronic engineers together built
machine tools to produce profiles & shapes that were nearly impossible by conventional
machine tools. US Air force combined with Parsons corp.
•to produce first NC machine in the year 1947. The termnumerical control was coined by
Massachusetts institute of technology, USA. By mid 1960s, Russia, Japan, West-Germany,
England etc was, leading manufacturers of NC machines.
NUMERICAL CONTROL MACHINE
5. •In earlier days the conventional machines were used in industries where the operator used
to control the various machining parameters such as feed, speed, depth of cut etc. in the
year 1947, the united states Air force introduced NC machine for manufacturing Air craft
components. But these machines were commercially available in the year 1955.
•In the year 1971, there was a rapid development in the field of electronics like integrated
circuits and micro controllers were developed. These devices were used to control the NC
machines.
•A simple computer was interfaced to the NC system which stored the data, instructions
and programs which were required to run the CNC machines. In a CNC machine all the
numerical functions are controlled by the computer.
•The computer also gives the display of various parameters of the machine like spindle
speed, feed rate, depth of cut etc. It consists of electronic instrumentation to measure the
output.
CNC MACHINES
6. 1.It eliminates human errors.
2.Requires semi-skilled labour.
3.Higher flexibility.
4.High accuracy.
5.Wastage is minimum.
6.Suitable for batch production
.
7.Less space is required.
8.Reduces inspection cost.
9.More operational safety.
10.Quality of product is high.
ADVANTAGES OF CNC MACHINES
7. DISADVANTAGES
1.Initial cost is high.
2.It require skilled programmer.
3.It is not suitable for small scale production.
4.Maintenance cost is more.
1.Numbers of operations per component are many.
2.Complexity of the operation.
3.Size of batches is medium.
4.Repetition of batches is large.
5.Layout cost of the component is high. 6.Variety of
components to be produced is more.
APPLICATIONS
8. What is CNC programming?
It is a set of instructions given to the machine to perform a given task. CNC
Programming can be done in two ways.
1. EIA/ISO Format (Fanuc/ISO Control) EIA: Electronics industries association O-
series.
ISO: International standard organization. In this method programming can be done by
use of G and M codes.
G codes are called preparatory functional codes and M codes are called miscellaneous/
Machine function/ on-off functions.
2. Dialogue based programming , In this method the programming can be done by use
of symbols like line, circle, square, ellipse , pentagon, spline, multi-line etc.
CNC PROGRAMMING
9. 1. Absolute dimensioning: In absolute dimensioning all the dimensions/points are
measured from common reference point or zero point. This zero point is called datum
point.
Two types of dimensioning
•Absolute dimensioning(G90)
•Incremental dimensioning(G91)
DIMENSIONING
10. 2. Incremental dimensioning
In incremental dimensioning all the points are measured from current
tool position. These dimensions are measured from the previous
measuring point.
