G71 internal profiling question

[Rich L]

I'm pretty new to G-code programming and I have a question about G71 internal profiling using a gang tool lathe. My control is Fanuc 0i Mate TB.

All of the descriptions I've seen show a left hand profiling tool doing its internal cutting against positive X inside (+X away from me) surface. My question is whether it is possible to use a right hand profiler against the -X internal surface. Does G71 care about the profile being on the negative side of center?

Thanks for any advice!

Cheers,
Rich

[ad64075]

You can indeed profile on the X- side during a G71 cycle. I have done it many times. Just be certain your machine will allow enough travel in the X- direction.

[sinha_nsit]

In fact, X- internal machining is logically equivalent to X+ external machining as regards toolpath definition, start position of the tool and finishing allowances.
But on most machines, you may get an overtravel alarm.

[Rich L]

Thanks for the indications it should work. Admittedly, I haven't quite tried it yet but I do wonder about the two consecutive warnings I've gotten here about overtravel. If the profile causes the toolplate (gang tool lathe) to move within bounds why would I see an overtravel alarm? Why would "most machines" give me an overtravel alarm for G71 internal profiling?

Cheers,
Rich

[dcoupar]

Originally Posted by sinha_nsit In fact, X- internal machining is logically equivalent to X+ external machining as regards toolpath definition, start position of the tool and finishing allowances. But on most machines, you may get an overtravel alarm.

On turret style machines you can only take the centerline of the boring bar holder a certain distance past the centerline of the spindle, so if you are boring on the x- side you may reach that limit (see attached .jpg).

With a gang-style machine, you should be able to arrange your tooling so the boring bar will run without x-axis exceeding the travel limits.