[nlh]

Can someone provide me with a sample program with explanation concerning the G71 threading cycle along with the necessary M codes (M33, M73, etc)? I have the programming manual and have been going over it tonight but to be honest I am a bit lost.

As far as experience is concerned I have never used a G71 or similar cycle on any machine. The only other CNC lathe I have ever run is an old Mori SL-1 (Yasnac 2000G) that does not have complex threading cycles, I use G92 for threading on that one(ex. G92 X-10000 Z-20000 F1250).

I need to cut a 1-8 thread in 1018CR. I will be using Top Notch style inserts and the recommended number of passes (Kennametal's recommendations) is between 12 and 15 for this pitch thread. Thing is I don't see how I can input the number of passes using this cycle. It seems as though the control determines that for me, which I am not really comfortable with. The Manual attemps to describe this but doesn't do a very good job. Any help concerning this would be much appreciated.

Thanks,
Nate

[littlerob]

Nate, it is really not that difficult, the D value is a percentage and as it gets closer to finishing (I think the last couple of passes) it gets smaller. I cut alot of threads on an Okuma lathe. Sample program G71X..Z-..D.03H....F.125. The D value is going to determine your rough passes, but when it gets closer to finish X it will be less, it does this in the control automatically, in order to reduce tool pressure, it is not a Mori . Robert

[nlh]

Thanks Rob,

So the D value basically does 2 different things. First pass in your example would be .03", correct? Then after that it switches to a percentage of that value until it get to the tolerance value (can't remember that letter until I look in the book again)? Am I correct on these 2 points?

Thanks again,
Nate

[littlerobb]

It will rough at .03 until it gets to .03 above finish X then it will break it down into a percentage of .03. If that makes sense. Robert

[nlh]

Yes, That makes sense Rob. I know, I'm making it much more complicated than it really is. Once I start using it I'm sure it will all work out fine.

By the way, does this value, amount to the depth of cut per side or diameter (actual .015 per side)?
Thanks

[littlerob]

Yes, That makes sense Rob. I know, I'm making it much more complicated than it really is. Once I start using it I'm sure it will all work out fine.

By the way, does this value, amount to the depth of cut per side or diameter (actual .015 per side)?
Thanks

It is on the diameter, I don't think any OSP controls will give you values on the radius, (could be wrong). but the H value is the height of the thread from crest to root which IS a radial value. Not to over complicate it just to let you know. Robert

[littlerob]

An Okuma control is a different animal, Yasnac is so standardized that most people can muddle their way through the code, even if their not familiar with the machinery, But that OSP control is so friendly, once you know it I don't think there is an equal, Robert


There are also alot of cool features with that canned cycle that you can tweek pretty simply, zigzag infeed, I like that one, if you need anything else send me a P.M.

[nlh]

Rob,

Thanks again. I have my program in the machine and all my tools set but one thing I did notice on the threading is that I can't seem to not make the machine take a large first pass. For instance, with D set at .02, the first pass X diameter comes to .9123 with M33 and M75. No matter what I have tried the smallest first cut amount I can get is .077. I want to get this smaller. I must be doing something wrong but don't know what. I can't make any logical sense of what the machine is doing with the D value and it's threading passes. For instance, I set D to .001. The machine cuts it's first pass at .9230 then proceeds to take a cut at .003" increments. Any idea's?

Would have PM'd you but have to clean them out first.

Nate

[littlerob]

Don't get me wrong I love the machinery, if you're first pass is way to deep increase the H value HALF what you need. ie If your first pass is .05 too deep on the diameter, increase it by .025. It will probably give you an alarm, but that will tell you that you need to increase your start X value. I have been cutting threads on these machines so long I guess I kind of feel them out. Send me a P.M. and I'll make sure you get up and running, Robert