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12-04-2010, 05:35 AM #1
Okuma Threading - G33 or G71 What do you use?
Which do you most commonly use and what are the advantages of one over the other?
I have a VERY simple threading job to do.
1"-8 x 2" lg. thread on some 1" Dia. 1018 shafts.
With the G33 I have to input every X move, and on the G71 I do not.
It leaves me to wonder, if G71 is that simple, why would you use G33?
On Fanuc I always used G32 and had to input every X move, so the thought of G71 has me all giddy with just the one line of code.
Is it truly that simple?
12-04-2010, 05:37 AM #2
Nobody say nuthin until he finishes his story.
12-04-2010, 05:59 AM #3
12-04-2010, 06:58 AM #4
I have no idea on lathe threading. I have 5020M controls on mills and the manuals do not cover the lathes. The other site (the one that takes about 2 days to load) has a pretty good okuma page and might be worth looking at.
12-04-2010, 07:14 AM #5
G33 is good for troublesome situations and weird groove shapes that the threading cycles are not so good at. One time I was threading some 8" NPT sections about 10" long, unsupported on the outer end. Using the G76 cycle (on Mits) would not work due to the way that the macro infeeds the tool. The pipe would begin to vibrate after the thread was about half depth, and got progressively worse. So I hand wrote what I thought was an infeed technique that I thought would work better (single side cutting only) and got the job to run ok.
In another instance, I had to cut a rope thread with a round tool, and this is just outside the capability of the standard v thread macro.
12-04-2010, 10:08 AM #6
I use the G71 threading cycle, I only use the G33 when I want to do a single pass to clean up a thread. For instance, I was doing a weird thread in some aluminum and I was using a partial profile insert. After threading I would run a finish tool over the top to cut off any fuzz but some would end up in the thread. So I programed a G33 single pass just to clean up the thread, sort of a re-thread but only one pass.
Results were very nice, then the customer decides to let CF epoxy get all over the threads and asks me to make him a custom die to clean the threads up. They look like Fred Flinstone wheels when they are done with them...why do we bother?
12-04-2010, 11:06 AM #7
Why do we bother....indeed.
I made a delicate little spindle for an edger for an optical shop. It required starting with 1.75" 304SS round and turning it down to 3/16 for 2.5" and then a large flange left on one end. The drawing specified .188 +0.001/-0.0, so I made it the .188 kind of assuming they would install a bearing on it somewhere. The flange required some profile milling in a different setup. It turned out nice, albeit, the design had some very thin sections because it was drilled from the flange end inwards.
Anyways, the next day the customer phones me and asks "what did you make this out of? It was supposed to be stainless, but it seemed awfully soft". Turns out he was pressing 4 bearings on it and (predictably) they seized and stuck and he bent it.
12-04-2010, 01:45 PM #8
Mission control.....we have a problem!!!! lmao j/k
12-04-2010, 02:58 PM #9
I have my "Fanuc" way of doing the threading and it's never been a problem, but being new to the Okuma code I wanted users opinions of which works best for them in a given application and why. Thus my question.
12-04-2010, 03:22 PM #10
J/k Russ...I know I'm in good hands!!!
12-04-2010, 03:28 PM #11
G33 is all I get to use since the parts we make require a variable pitch lead change. Siemens requires a .0008 per inch change in thread pitch. Talk about a PITA to use thread wires on! There prints say measure thread #3 at a given diameter over wires then thread #20 at another given diameter. Try finding a thread gage for that one .
12-05-2010, 07:19 AM #12
Yeah it really is that simple Russ. If you look in the manual, there's also a paramater within the thread cycle that'll allow you to run the actual cut pattern 3 or 4 different ways, from straight infeed to infeed at a specified angle to a cycle where the tool moves fore and aft from cycle to cycle to remove the same amount of material with each pass. It should also automatically reduce the DOC as it nears the specified depth, going from D to D/2 to D/4 to D/8, etc on successive passes.
FWIW, with the exception of the constant material removal cycle, Okuma's control would do all the above in 1980, on controls 2 generations older than your 5020. Takes about 3 lines of code to spec the thread on those rather than the single line, but it beats the hell out of writing out every move. All these controls also allowed you to cut variable lead and variable pitch dia threads within the auto cycle as well. IMO, if Okuma had made their lathe controls available to other builders starting in the late 70's, a Fanuc lathe control would be a rare thing today.
12-07-2010, 12:22 PM #13
We have two Okumas, both run every thread they cut on the G71 cycle. We don't run anything but straightforward threads though. No tapers, no multilead, and 16,12, and 8 pitch on everything. Very basic threading. G71 will do much more complex thread than that, we just don't need to. Works for us.