Multi cut threading macro program example using G76

Custom Macro – Using variables for the Programming :

Ideal application for the use of Variable programming (i.e. Custom Macro Programming) on a CNC Lathe :

As such the usage is covering very vast application area. You name it and it can be coded using macros. But, by and large following are the core application areas :  

1)   Threading applications like variable lead threading, Multi start threading,   

      Square and Trapezoidal threading, circular form non-standard type    

      threading ;  

2)   Multi-start worm cutting ; 

3)   Face and radial grooving of non-standard type;  

4)   Design one’ s own cycle of any type.

Example :  Carrying out 4 start threading of the size – M16 x 2.0 mm pitch.  Write a custom Macro “A” Program for the same. Use Multi-cut threading cycle – G76. Use following data :

Data : 

i)     O. D. = 15.8 mm  
ii)    δ1 = 30.0 mm  
iii)   δ2 = 5.0 mm  
iv)   1^st cut depth = 0.3 mm  
v)    Lead = Pitch x no. of starts = 2 x 4 = 8 mm  
vi)   Chamfer amount = 1.0 times the lead.  
vi)   Root diameter = 13.3 mm  
vii)  Thd. Height = 1.25 mm  
viii) Length of threads = 50 mm  
ix)   No. of finishing passes = 3 nos.  
x)    Limiting depth of cut per pass = 0.075 mm  
xi)   Depth of cut for finishing pass = 0.050 mm.
xii)  Angle of Approach = 60 degrees.

(A)   Custom Macro – A for FANUC OT-D/C systems

O0001 (4 START THREADING);

N1;
T0000;
G28 U0 W0;
T0101;
G50 S800;
G97 S800 M03;
G65 H01 P#100 Q30000;
M08;
N10;
G0 X17.0 Z#100;
G65 H83 P20 Q#100 R36000;
G76 P031060 Q75 R50;
G76 X13.3 Z-55.0 P1250 Q300 F8.0;
G65 H02 P#100 Q#100 R2000;
G65 H80 P10;
N20;
M09;
G97 M05;
G28 U0 W0;
M30;
%

(B)  Custom Macro “B” for FANUC Oi Mate – TB/TC system :

O0001 (4 START THREADING);

N1;
T0000;
G28 U0 W0;
T0101;
G50 S800;
G97 S800 M03;
#100 = 30.0;
M08;
N10;
G0 X17.0 Z#100;
IF [#100 GT 36.0] GOTO 20;
G76 P031060 Q75 R50;
G76 X13.3 Z-55.0 P1250 Q300 F8.0;
#100 = #100 + 2.0;
GOTO 10;
N20;
M09;
G97 M05;
G28 U0 W0;
M30;
%

____________  

Jasmin C. Shah,

CNC Application Engineering and Programming consultant

Date :  13^th September, 2006