Problem with the G70 command

[markus314]

Hey!

I'm using a turning machine with a fanuc O-T system .. Can anyone tell me whats wrong with this kind of code?

....
G70 P1 Q2
N1 G00 X 10.
....
...
....
G01 Z-30. F0.1
X30.
N2
G70 P1 Q2
G28 U0 W0
...

I expected the machine run to the cycle between N1 and N2 two times and return to home. I've done this many times with a G71 command first, which then had the cycle and the G70 commands like this later in the program:

G70 P1 Q2
G70 P1 Q2

But this time the machine after reaching X30. in the second run of the cycle started on another run of the cycle directly, trying to move to X10. from the end point of the cycle (X30. Z-30.). This caused a crash, can someone please explain why?

[dcoupar]

AFAIK, you must do the G71 first.

[markus314]

It's just so weird to make G70 work as a function if G71 is used first, but if not it works just like a GOTO.. It's just so unlogical!! And so unlike fanuc from my experience.

And what about if you start a program and then jump over the G71 command and goes straight to G70, will it still act like this? Or will it check for G71 in the program in some way? It sound crazy to me..

[Mike Stevenson]

G70 is the finish command for the G71 and G72 codes. It is not for jumping around in the program. Use a subprogram for that.

[markus314]

Ok, so you have to have a G71 command to have a G70 command? It's so strange that G70 don't have the same function if you don't use G71 first, you allready have a GOTO command! Why make an exeption in the behavior of G70 that has no possitive effect at all?

It looks like a flaw to me! G70 should read from P to Q no mather whats been done previously in the program. Since you have to write a G00 command at the same line as P this is a flaw that could cause a lot of problems in the case of typing errors or cases like mine where you expect it to work as it normally does because most likely the G00 would crash the tool..

[Mike Stevenson]

markus314,

I'm sorry newbee but It does not work that way.

[adamant]

Originally Posted by dcoupar AFAIK, you must do the G71 first.

Seems to me I have run a G70 without a G71,G72,G73 before.......................

I'd try it like this.

N1 G00 X 10Z.1
G01 Z-30. F0.1
X30.
N2G0 Z.1
G70 P1 Q2
G28 U0 W0

That should Run between the N1 and N2 and then repeat.

I could be wrong................It is fun to just plug the numbers in and see what works if you got the time.

[Mike Stevenson]

Originally Posted by adamant Seems to me I have run a G70 without a G71,G72,G73 before....................... I'd try it like this. N1 G00 X 10Z.1 G01 Z-30. F0.1 X30. N2G0 Z.1 G70 P1 Q2 G28 U0 W0 That should Run between the N1 and N2 and then repeat. I could be wrong................It is fun to just plug the numbers in and see what works if you got the time.

And are willing to risk a crash on a lathe.

[Geof]

Originally Posted by adamant Seems to me I have run a G70 without a G71,G72,G73 before... I could be wrong................It is fun to just plug the numbers in and see what works if you got the time.

I played with a program on my Haas simulator and found it would do G70 without any G71 or G72.

[Mike Stevenson]

Maybe that's true in the HAAS world but I doubt it. Take it from an old Fanuc lathe guy, you know not what you do. Especially if you are jumping around with modal codes in place in your program. I hope I'm wrong. Can you please tell me why you want to do this lazy thing?

[Geof]

Originally Posted by Mike Stevenson Maybe that's true in the HAAS world but I doubt it....... .... I hope I'm wrong. Can you please tell me why you want to do this lazy thing?

"lazy" thing?

I am puzzled by your post.

I have a program with a G71 sequence that roughs out a profile which is then finished by a G70.

I deleted the G71 line and ran the program; it ran and the tool followed the profile path...that is the finished profile path.

Which is what I said in my post.

[adamant]

Originally Posted by Geof I played with a program on my Haas simulator and found it would do G70 without any G71 or G72.

Dang I was getting ready to make some money......