On Sun, 12 Dec, 2021 at 4:26 PM, Chris Albertson <albertson.ch...@gmail.com> wrote:
To: enhanced machine controller (emc) On Sun, Dec 12, 2021 at 12:39 PM Gene Heskett <ghesk...@shentel.net<mailto:ghesk...@shentel.net>> wrote: > On Sun, 12 Dec, 2021 at 2:54 PM, Chris Albertson < > albertson.ch...@gmail.com<mailto:albertson.ch...@gmail.com>> wrote: > > > To: enhanced machine controller (emc) > I'm surprised that people don't use kinematics to remove the residual > alignment errors that can't be mechanically removed. Of course, you can't > remove tool orientation errors this way. If the z-axis is a few > milliradians "off" the tool will also be "off" but kinematics can > compensate for the X, Y error associated with variable Z movement. > > That said, I can't measure this kind of low-level stuff so I don't worry > about it. > > You should be able to lead the Z- column over at 45 degrees and still hit > X, Y point spot on. (it would work only for a spherical tool) > > > > If it was moveable Chris, but its not, the column is fixed, but the head > can be No, you never want to do that. Why not? I needed to drill and rigid tap a motor shaft to pulley joint, positioning the two holes half in the motor shaft, half in the pulley then fill the holes with 4mm metric screws to key the normally screwed on pulley to the shaft. I had done similarly to a 1 horse treadmill motor on my 7x12 but Jons pwm-servo driver can be quite brutal and powdered the grub screws I put in for keys on the first motor. I used solid screws for the 2nd one, and softened up the control rates, and its now worked for about 6 years. That switch to using the x axis for rigid tapping bypassed this leaning tower of pizza post, and cut perfect 4mm threads, much more precisely than I could do using the leaning z axis. My point was that there could be an absurd amount of error and you should still be able to work with it by telling the kinematics system the column meets the Y axis at 89.9<http://89.9> degrees. Its worse than that, if the head is trammed to the table, and you want to drill all the way thru a tap hat slug with a 7/32 drill, its bending the drill bit visibly sideways by the time the hole is 3/4" deep in a 1.25" slug of brass. Way out of tram, but its not. I'd think we are talking arc minutes at most here for a real milling machine. But there are home-made CNC machine made with rails mounted to a plywood base. BTW, even with the 0.1-degree error, you still have good accuracy with realistic Z-axis moves. > > rotated 90 degrees either way and I have several times. That works quite > well. > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net<mailto:Emc-users@lists.sourceforge.net> https://lists.sourceforge.net/lists/listinfo/emc-users . _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
