There seems to be little if any documentation from Tormach on the input field called “TAPER:” - see here:
It’s even absent in all the Tormach depictions of this screen?
Anyway, my first time using this function is for an external 1/2” NPT on a pipe end. Looked like an easy thing. Some parameters are automatically available using the drop down box & then just fill in the rest. Well not so fast, just what exactly do you enter into the taper field. It’s definitely not the angle because the resulting code is not even close.
So I started digging into the G76 command. Nothing from Tormach. So I figured it’s probably using something similar to LinuxCNC as described here.
Hmm, all the parameter match-up pretty good except for this O- parameter that corresponds to the TAPER field. No documentation on this parameter – anywhere…
So after reading about all G76 formats, FANUC, HAAS, LinuxCNC, etc…, I came to the conclusion it’s a special parameter that Tormach has added to its implementation of the G76 cycle. Maybe this has been talked about elsewhere but I could not find anything. My best guess is that you enter what the thread major diameter should be at Z END. Great, now I’m getting something that looks like a pipe thread.
So during all this exercise I decided to see if one could use the H-, E- & L- parameters. The H- parameter (number of springs passes) does work. Both E- & L- (tapered entry/exit) do not generate an error but they are ignored and it would be nice to have them work.
OK, so now I want to tune this thing up and get it cutting faster because cutting at 250 RPM with light cuts is generating a huge number of passes. Well you quickly realize you're never going to get close to the recommend SFM for your cutter & material. It’s gonna be a huge compromise to the low side and the H- parameter is gonna be handy - lots of spring back! For my 1/2" NPT program spindle RPM's higher than 780 generate an error.
Also I’m noticing that once you cut a thread for a given program & spindle RPM, if you change only the spindle RPM & rerun the same part the threads will no longer be in sync. This doesn't seem right to me.
So my questions are:
Is there a definition somewhere for the TAPER field?
How do you make a reasonable DOC at slow speeds & feeds and keep spring back to a minimum?
Is it wrong to assume thread sync should be maintained if you only change the spindle RPM & rerun the part?
Thanks