On Monday 10 August 2015 19:38:28 David Bagby wrote: > Hi, > I'm planning a mill conversion to LCNC and I'd like it to be able to > do rigid tapping. > Description of mill, particularly its spindle & drive?
> I figure that this will require an encoder or equivalent) on the > spindle. I won't be able to to easily attach a common encoder disc to > the spindle, so I will probably have to create an encoder (which > appears easier than doing a remote encoder driven via a belt etc). That is what I did on this GO704, but I had to put my mind back in maker mode to do it. > I've looked but not found a spec for the required encoder resolution. > Does anyone have advice as to min spindle encoder resolution (ppr) > required? Has anyone gotten by with 8 or 12 pulses (32 or 48 > quadrature) ? > > Dave I have not tried that low, but I'd think, based on some that claim to have made it work with 1 PPR, that a suitably stiff controller that will not allow more than a few percent of speed variation with the load coming on when the tap starts to cut, it may be possible. I have not yet checked out this function on my conversion in progress GO704 though. With a 67 slot, 268 quadrature edges per rev, I can set Pgain in the spindle PID as high as 500. But that upsets the driver on a fast slowdown, so its currently set for 150. Stopped to 2600 is substantially under 1 second in high gear. So the question yet to be answered, is how big a tap can this stock 1HP motor, in low gear, turn? My lathe has a 50 slot wheel on it, 200 quadrature edges per rev, and within the horsepower limits set by a plastic driveline, can run an 8-32 straight into brass, and can peck, a half turn a peck, up to 1/4" SAE tap in steel. Better driveline parts should expand that to at least a 1/2-SAE tap. Sometime these question can be something like "how long is a piece of string? We won't know till we build it & break the weakest part 2 or 3 times. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
