CNC Lab
Manual NC Part Programming:
The following considerations must be borne in mind before actually writing the program:
1) What tools does the part require?
2) How is the workpiece clamped?
3) Is the working range in both the directions sufficient or is it necessary to
reposition, turn and clamp the workpiece?
4) All coordinate points, referred to the origin should be calculated before making a
program table.
5) Feed, Speed and depth of cut should be calculated depending on the tool and
workpiece materials
Working Range: The maximum working range without repositioning and turning extends
from the tool center to the work piece locating edges and is designated by X and Z.
Machine Zero: This point is a fixed point of reference for defining other points.
Workpiece Zero: The intersection of the axis of the workpiece and the facing side of the
workpiece is defined as the workpiece zero.
Reference Point: A fixed point to which the tool is traversed before starting any cutting
operation, switching off. (Home position)
Part program for a CNC machine:
A part program contains all the information for the machining of a component that is fed
to the control unit.
The input information required is fed in a series of blocks.
The control unit provides the control signal at the correct time and in the correct
sequence to the various drive units of the machine.
There are three types of input information in a part program for control of the machine:
1) Information on desired work/tool relationship.
2) Information on rate of work/tool relationship.
3) Information on auxiliary functions.
Program Structure:
It consists of the following three steps:
1) Program start
2) Blocks
3) Program end
Block Format:
N90 G___ X__ S__ T__ M__ eob
N – Number of block address
90 – Block Number
G – Preparatory function
X__ & Z__ – Path data
F – Feed rate (mm/min)
S – Speed rate (rev/min)
T – Tool number
M – Miscellaneous function
eob – End of Block
Some Definitions
? Preparatory functions: which unit, which interpolator, absolute
or incremental programming, which circular interpolation plane,
cutter compensation, etc.
• b. Coordinates: three translational, and three rotational axes.
• c. Machining parameters: feed, and speed. => feed rate, spindle
speed
• d. Tool control: tool diameter, next tool number, tool change.
• e. Cycle functions: drill cycle, ream cycle, bore cycle, mill cycle,
clearance plane.
• f. Coolant control: coolant on/off, flood, mist.
• g. Miscellaneous control: spindle on/off, tape rewind, spindle
rotation direction, pallet change, clamps control, etc.
• h. Interpolators: linear, circular interpolation
STEPS IN NC PROGRAMMING
1) Analyze drawing features and part requirements
2) Find co-ordinates of each point required to make the part
3) Trace out path to be followed by tool
4) Look up NC codes for tool movement/miscellaneous commands
5) Write step by step NC code
6) Manual check
7) Simulate NC code
8) Debug the code
8) Machine the part
? TURNING NC PROGRAM:
The raw stock is rotated at a high speed and a tool is used to make symmetric
cuts around the stock.
TURNING OPERATION
PROLIGHT CNC TURNING CENTER
Prolight CNC Turning Center:
Machine Specifications
Axis Travel
X axis 4″
Y axis 10″
Swing over Bed 6″
Swing over Cross slide 3.9″
Work Area
Table Size 11.5″ * 7″
Table Load Capacity 100 lbs.
Spindle
Drive Motor 1 hp
Motor Type DC Permanent Magnet
Spindle Nose Threaded 2.25-8 UN-2A-RH
Speed Range 0 – 1,200 RPM and 0 – 3,600
RPM
Accuracy
Ballscrew 0.001″/ft
Repeatability 0.0005″
Resolution 0.00025″
Dimensions
Width 36″
Depth 22″
Height 24″
Figure 1: Coordinate system
Raw Stock Specification:
Brass Piece: 3 (length) and 0.75 (diameter) inches
N1 G90 – Code for Absolute Coordinate
N2 S2000 M03- Rotation speed 2000 rpm, M03- Spindle On
N3 G00 X0.5 Z0.4 – Bring to position before cutting starts
N4 G1 X0.375 Z0- Slowly bring right at the edge of the workpiece
N5 G91-Shift to Incremental Programming
N6 M98 P100 L5- Call Subprogram 100 using M98 for 5 cycles
N7 M98 P200 L5- Call Subprogram 200 using M98 for 5 cycles
N8 M98 P300 L5-Call Subprogram 300 using M98 for 5 cycles
N9 M98 P400 L5 -Call Subprogram 400 using M98 for 5 cycles
N10 M98 P500 L5- Call Subprogram 500 using M98 for 5 cycles
N11 G1 Z0.005-Bring back into position away from the workpiece
N12 G1 X0-Bring in alignment with the axis of the workpiece
N14 M05-Stop spindle
N15 M02-End of Program
O100-Subprogram 100
G01 X-0.005 F5
Z-1.25 F5
G0 Z1.25
Z +
(0, 0)
X +
M99-End of Subprogram
O200
G01 X-0.005 F5
Z-1.0 F5
G0 Z1.0
M99
O300
G01 X-0.005 F5
Z-0.75 F5
G0 Z0.75
M99
O400
G01 X-0.005 F5
Z-0.5 F5
G0 Z0.5
M99
O500
G01 X-0.005 F5
Z-0.25 F5
G0 Z0.25
M99
MILLING NC PROGRAM:
The raw stock is held stationary and the tool is rotated at a high speed and
moved to make necessary cuts.
MILLING OPERATION
PROLIGHT MACHINING CENTER
Machine Specifications
Axis Travel
X axis 12″
Y axis 6″
Z axis 9″
Work Area
Table Size 19.5″ * 6.25″
Table Load Capacity 100 lbs.
No. of T-Slots/Size three 3/8″ T-Slots
Spindle
Drive Motor 1 hp
Motor Type DC Permanent
Magnet
Throat 6.25″
Speed Range 0 – 5,000 RPM
Accuracy
Repeatability 0.0005″
Resolution 0.00025″
Dimensions
Width 26″
Depth 32.5″
Height 32.5″
The difference in the NC programming of a Turning center and a Machining Center is
that in a machining center, the worktable moves, but the programming is done for the
movement of the tool.
1) Milling Centre
a. Side with 3” length (X)
b. Side with 2” length (Y)
c. Side with 1.5” length (Z)
d. Origin
(0, 0, 0) X +
Y+
CNC Lab
Important Things to Remember:

1) This is an individual assignment. Before you submit your program, you can send
it to the TA for verification. Considering the large number of students in the class,
you should send your work at least two days before the assignment due date so
that he has enough time to go through your work.
2) Milling Centre
a. Side with 3” length is fixed parallel to axis (X)
b. Side with 2” length is fixed parallel to axis (Y)
c. Side with 1.5” length is fixed parallel to axis (Z)
d. S=1500 (Spindle RPM)
e. Tools : T1 (diameter is 0.15”)
f. Z = 0 at the top surface of the wax block
g. X=0 and Y=0 are located at the bottom left corner

Raw Stock Specification:
Milling Operation-Wax Piece: 3*2*1.5 inches
Write a Milling NC program for the following design:
Use the simplified design and dimensions from homework 1 (“LAB”). The depth of the
letters is 0.3″.
(0, 0, 0) X +
Y+
To make sure that the all of the programs start the same, the TA has given the first and
last few lines. You will not need to define any feed (F) for any of the program. You will
need to fill in the values for X and Y on N7 (line 7), and continue your program after N8
(line 8). You are free to use absolute or incremental (or both) coordinate in the main body
of your program.
N1 M06 T01 (Installing tool)
N2 G90 (absolute coordinate system)
N3 G00 X0 Y0 Z0.8
N4 M10
N5 G91 (incremental coordinate system)
N6 S1500 M03
N7 G00 X ___Y ___ (Plunge your X and Y coordinate)
N8 G01 Z-1.1 (Tool goes 0.3″ into the part)
……
……
……
N? G00 Z1.1
N? M05 (end of program)
Submission:
Please submit your entire program to D2L in .txt format.