I need some help making G76 multi-repeat threading work.
The machine is a Daewo Puma 8HC-3A with Fanuc 15-TF control.
I want to thread 1/8” NPT on brass.
27 Threads Per Inch, thread lead = 0.037037”. Will simplify to .037”
From charts, thread depth = .027”
From charts, the thread length is ~3/8, so I will use .4” to be threaded onto my brass
Major dia at big end from charts is .405
The tool start will be positioned .2” in front of stock, making that a Z0.200” dimension, a Z total travel of .6”.
Extending he slope of standard pipe threads makes the X position at that lead-in to be 0.3675”
Total X diameter change over Z stroke of .600” is: .405 - .3675 = .0375”
In trying to understand the G76 operation, I want a 1st cut depth of .001”, a minimum cut depth of .001”, finish allowance .001”, and 1 finish pass.
Here is the code I have tried:
(THREADING HERE)
G20 G56 G90
G97 G98 M17
M42
G50 S2000
T0606
G00 X1. Z5.0
M03 S60
M08
Z.200
X.3675
G76 P010060 Q10 R10
G76 X.351 Z-0.400 P270 Q10 R-375 F.037
G00 X8. Z10.0 M05
M09
M30
%
Removed stock from chuck, so as to just observe process cutting air.
The above code (with S700 code) results in 10 threading passes, but they didn’t look right.
Changed to S60 so as to observe what’s going on. I monitored the X & Z positions during the threading passes, and X DID NOT CHANGE during the Z movement from +.2 to -.4
And the X values didn’t make sense to me. Below is what I observed for X positions during the 10 passes.
Pass # X @ start X @ end
1 .361 .361
2 .371 .371
3 .381 .381
4 .391 .391
5 .401 .401
6 .411 .411
7 .421 .421
8 .276 .276 <<<<<==== ??
9 .351 .351
Very bizarre results.
Sure need some help with this.
Cheers