On Sunday 06 December 2020 00:41:20 John Dammeyer wrote: > I was watching a Clickspring video on the construction of a floating > die holder for a small Sherline lathe. He attached a belt drive to > the spindle and using the Division Master indexed the lathe while > running a spinning cutter for grooving the die holder. > > What I was wondering is if LinuxCNC, with a suitable Servo Motor or > high res encoder on the spindle can treat it like a 4th axis on a > mill. > > Realistically if a mill can be run with an AC servo and step/dir > control up to 3000 RPM then there's no reason the lathe spindle > couldn't be run the same way. And with step/dir also serve as a > spindle indexer. > > How easy is that? Or does it require a different version of LinuxCNC. > (ie differnet ini and hal files). The spindle normally only has > speed and direction. It's products like the MESA 7i92H that turn that > request into either PWM or step/dir. > > Would a module like the 7i92H need different FPGA programming to do > the same thing? What about with MachineKit and the BeagleBone Black. > It can use encoders on the spindle. But can it do actual position > control? > > Just curious. > John Dammeyer > Easy test John. Start a G33.1 move and reduce the spindle override to zero.
Reach for the spindle and turn it, z follows perfectly in either direction on my G0704. Or I've done the same stop with the encoder off the motor so I can turn it by hand. The spindle follows the encoder within a degree. Its driven by one of the Pico pwm-servo's. But the encoder is scaled to the motor so the control is very tight even in high gear. Only the index comes from the spindle, the encoder is on the rear of the motor and I have tally switches on the gearshift knob that change the scale in hal according to the gear, in low gear its a bit over 14,000 due to the gear ratio in the z head and the 4x multiplier in the encoder. That's the sort of follow precision you would get by driving the spindle with a stepper driver, so as long as the motor has the cajones to do it, I see no reason it wouldn't Just Work. And I can see one quite huge advantage in the use of a stepper, it s/b able to anticipate the null point, meaning there wouldn't be the tap breaking overshoots as the stop and reverse point can I think, be anticipated. 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
