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Okuma & Howa ACT-20 with FANUC 18TA Control - Thread Chamfering Question

WayneC369

Hot Rolled
Joined
Jan 4, 2014
Location
ATL, GA, USA
Hello All,

I have posted regarding this same question a number of years ago, but I'll be damned if I can find it.

The power supply in this lathe recently went up in smoke and since I have little to no documentation on this thing I have pretty much reverse engineered the entire control integration. During which I came across the M codes M46 and M47 again. The MTB manual's description of these codes is simply and concisely "chamfering "on" command" and "chamfering "off" command", respectively.

The ladder logic shows that an M46 enables this function by clearing the CDZ bit in the control. While M47 disables it by setting said bit. Upon power up the default condition is M46 is active. The FANUC documentation tells me this is for chamfering the lead out during threading operations using G76 & G92. And, therefore, is my source of confusion.

My understanding is the G76 command already takes care of this lead out chamfer and I specify the "pull out" in the second pair of digits in the first G76 block and is expressed as tenths of a revolution. This movement primarily pertains to the X-axis, although the Z-axis maintains synchronicity with the thread pitch.

So, my question, finally, is what does this thread chamfering which is controlled by the aforementioned M codes actually do? There is only a brief description that I have found in the 'Connections' manual of all places along with a couple pictorials. The pics lead me to believe the "pull-out" will occur over multiple thread pitches and not just a single turn. Is this true? If so, what is the purpose of such a tool path?
 








 
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