EXAMPLE 1 : NC PART PROGRAMMING
Aim : Holes of diameter 20mm and 10 mm are to be drilled at positions B and C respectively, on a rectangular plate.
Let us first recall the steps we will follow if the holes are to be drilled on a traditional way.
First we take edge A as reference
Mark positions of holes B and C as (20,80) and (90,25) respectively
The centers are punched
Drill of 20mm diameter is put in the spindle
Point B is positioned under the drill
Drill rotation is started and feed is given.
The operation is continued till the hole is drilled to full depth
The drill is retracted
The drill is taken out and replaced by another drill of 10mm diameter
Point C is placed under the drill
Drill is rotated, feed is given
Drilling is done
Drill is retracted
Work is removed from the table.
We
can write a NC program for the above operations as follows:
N001 G92 X0 Y0 F0
N002 G90
N003 G81 X20000 Y80000 Z-68000 R-48000 F100 T01 M03
N004 G80 Z0 F0 M05
N005 G81 X90000 Y25000 Z-68000 R-48000 F100 T02 M03
N006 G80 Z0 F0 M05
N007 X150000
N008 M30
Meaning of the program:
N001
G92 X0 Y0 F0: this instruction will make the machine register corner A
of the work piece as (0,0) in the control system: the operator shifts work piece
such that the corner A is under the spindle.
N002
G90: this will instruct the machine to follow absolute system, taking A
as reference point.
N003 G81 X20000 Y80000 Z-68000 R-48000 F100 T01 M03
This line will call the canned cycle for drilling; specify the point for drilling (B: (20,80)), and the vertical distance to be traversed by the spindle and the distance for rapid traverse. Also this will give instruction about feed, tool (diameter 20mm) and spindle start.
N004 G80 Z0 F0 M05
This
will cancel the G81 cycle and bring the tool to Z0 position at zero feed with
spindle rotation stopped. *
N005 G81 X90000 Y25000 Z-68000 R-48000 F100 T02 M03
This
line will again initiate canned cycle for drilling, specify new position for
drilling (C: (90,25), the vertical distance to be traveled, rapid traverse
distance, feed, tool (diameter 10mm). Also it will instruct to start the
spindle.
N006
G80 Z0 F0 M05: will provide information as explained previously (*).
N007
X150000: Job is removed from the table.
N008 M30 End of tape (Program).