Where to find Canned Cycle rules or explanations?

[lethal375]

Where to find info regarding programming rules for canned cycles?

I have 2 lathes with Fanuc controls
O-T & 21iT and both use the 2 line format

Example:
G71 - ROUGHING CYCLE
U(1) - DEPTH OF CUT
R - RETRACT VALUE
P - FIRST LINE OF SUBROUTINE
Q - LAST LINE OF SUBROUTINE
U(2) - AMOUNT LEFT ON FOR FINISHING IN X
W - AMOUNT LEFT ON FOR FINISHING IN Z
F - FEED RATE

The problem is with program lines just before and after

Even if you get this G71 info correct in the program you still need to have the correct line format before the 1st G71 line and after the 2nd G71 line

My Fusion Fanuc turning post processor puts the rapid move before canned cycle in 2 lines and controls will not except
Example:
N26 G0 Z0.0
N27 X1.56
N28 G71

Change to this and it works
N26 G0 X1.56 Z0.0
N27 G71

Is this a machine manufacturer specific?
Control specific?
Canned Cycle specific?

I guess I am asking, Am I missing something?

Thanks

 

[sinha]

controls will not except
Example:
N26 G0 Z0.0
N27 X1.56
N28 G71

Change to this and it works
N26 G0 X1.56 Z0.0
N27 G71

Unbelievable!
Possibly a typo in the program.

 

[DouglasJRizzo]

Where's the D.O.C?
Seems like quite a bit is missing.

 

[Mtndew]

Unbelievable!
Possibly a typo in the program.

I agree, there's no reason either way won't work.

 

[lethal375]

I did not add any of the G71 information in my example
Just wanted to show the lines before the G71 and what problems I am having

 

[William Lynn]

You already know which one works and which one doesn't. I never bothered to use G71 in all my years, but I'd guess it needs both X and Z coordinates on the same line.

 

[angelw]

I did not add any of the G71 information in my example
Just wanted to show the lines before the G71 and what problems I am having

As mentioned by Sinha and Mtndew, both of the code examples before the G71 Block should work just fine and there are no rules to be found with regards to the positioning Block before the G71 Blocks except for the commonsense rules where you would park the tool at an X coordinate slightly larger than the OD of the workpiece for an OD roughing program and slightly smaller than the bore of the workpiece for an ID roughing program.

If the face of the workpiece is Z Zero, or there is a finishing allowance on the face, its normal and sensible practice to park the tool at a Z Coordinate that will give clearance of the face of the workpiece, say 1mm (0.040). Parking the tool at Z0.0, as in your example code, where the face of the workpiece is zero, is at best going to rub the face of the work as the tool rapids to the next DOC (depending on whether you have included a finish allowance with the "W" address in the second G71 Block) and worse if there is a finish allowance of material on the face of the work.

Regards,

Bill

 

[lethal375]

Thanks guys
Just thought I was missing something

 

[rjwalker1973]

You already know which one works and which one doesn't. I never bothered to use G71 in all my years, but I'd guess it needs both X and Z coordinates on the same line.

It is according to if you want to use type 1 or type 2 roughing with the G71. I use type 2 nearly always so my first black after the G71 references my X and Z so that I choose Type 2.

 

[angelw]

It is according to if you want to use type 1 or type 2 roughing with the G71. I use type 2 nearly always so my first black after the G71 references my X and Z so that I choose Type 2.

Hello rj,
The OP's reported issue is whether or not the positioning move before the G71 is simultaneous or one axis at a time.
Why anyone would write the software to track whether a positioning move before a certain function was made by simultaneous axis, particularly when it would have no effect whatsoever on the operation of the function, is rather unbelievable.
Regards,

Bill

 

[rjwalker1973]

Hello rj,
The OP's reported issue is whether or not the positioning move before the G71 is simultaneous or one axis at a time.
Why anyone would write the software to track whether a positioning move before a certain function was made by simultaneous axis, particularly when it would have no effect whatsoever on the operation of the function, is rather unbelievable.
Regards,

Bill

I agree Bill. My post was in response to William's musings about G71.