Strange G71 behaviour

[MachineAmateur]

Hi,

I have old chinese CNC lathe (Washing 320Ti, early 2000) and it has peculiar G-code adoptations (manual is available, but does not offer detailed insight). Particularly strange is G71 without having G70 available at all. Also type II is missing, but that is a minor problem. What happens here is the roughing cycle is followed by finishing cycle automatically!

Is this based on some older standard and if so what is the reasoning behind it? Is there any workaround, particularly tool change would be nice? The routine does run the finishing line-by-line after canned roughing. I wonder if there is some secret sauce here, tried googling older standards but i guess there is none.

The current standard goes back to 1980 i think, so i find it strange why 20 years later they would not use correct implementations in China. Maybe they see the surface finishing unimportant

Thanks.

 

[alphonso]

I don't think that it is a finish cycle. The type I cycle roughs the profile with steps at each pass - no blending to previous pass. When it has roughed the profile completely it comes back and goes over the whole profile (with offset left for finish pass) to sorta smooth out the steps. Leastways, that's how my machines do it.

 

[MachineAmateur]

Yes, thats how it should do it but this one does finishing pass to the final contour dimensions. It has the preparatory smoothing operation too. This is stated in the manual, but to me it kinda defeats the purpose or is related to some very old way of doing things. I can change the feed for finishing pass, but seems like tool change command is not allowed within the G71 blocks.

I can work around it somewhat, tried to invent alternative ways to avoid writing two identical contour profiles as it will lead to eventual errors. One is to do some sort of work shift with G5x command before using the G71, which would leave eg. ~1mm on the surface (and using the profile again with jump command + G54). This is little bit difficult as work coordinates can be written directly, but they cannot be shifted (X+?).

Another method is to do scaling, increase the scale and reduce back for finishing pass. For roughing it could be found out what kind of scaling factor leaves out enough, but not too much for a finishing operation (will rely on gut feeling).

 

[alphonso]

Is this a real Fanuc control or a Chinese copy?

I am only familiar with 0T-C control.

 

[DouglasJRizzo]

Generally, when a G71 has completed the last cut, it will take a profile cut. I think there's a parameter to change that, but most have done it.
I'm curious, is this a real Fanuc CNC or a clone?

 

[LockNut]

Generally, when a G71 has completed the last cut, it will take a profile cut. I think there's a parameter to change that, but most have done it.
I'm curious, is this a real Fanuc CNC or a clone?

A clone? Really Doug? Get real, the Chinese don't have to clone anything!

Paul

 

[CORONA VIRUS]

I don't think that it is a finish cycle. The type I cycle roughs the profile with steps at each pass - no blending to previous pass. When it has roughed the profile completely it comes back and goes over the whole profile (with offset left for finish pass) to sorta smooth out the steps. Leastways, that's how my machines do it.

This "semi finish" action was dependent upon how much stock you left vs your rough DOC. And there are several versions on the canned cycle dependent upon parameter settings.

 

[CORONA VIRUS]

A clone? Really Doug? Get real, the Chinese don't have to clone anything!

Paul[/QUOTF]

From who's ass did you pull your head? They clone everything.

 

[TeachMePlease]

A clone? Really Doug? Get real, the Chinese don't have to clone anything!

Paul

From who's ass did you pull your head? They clone everything.

Psssst.... That was sarcasm